0000879407-26-000047 | 10-Q | XBRL Viewer | Arrowhead Pharmaceuticals INC

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Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands									1 Months Ended			3 Months Ended			6 Months Ended
	Jan. 07, 2026	Jan. 02, 2026	Dec. 31, 2025	Aug. 13, 2025	Feb. 14, 2025	Feb. 07, 2025	Nov. 25, 2024	Dec. 02, 2022	Mar. 31, 2026	Feb. 28, 2026	Aug. 31, 2025	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025	Mar. 31, 2026	Mar. 31, 2025	Jan. 01, 2026
Class Of Stock [Line Items]
Common stock, share reserve for issuance (in shares)									11,354,663			11,354,663			11,354,663
Warrant exercise price (in dollars per share)							$ 0.001
Number of securities called by warrants (in shares)							917,441
Warrants purchase price (in dollars per share)							$ 27.25
Proceeds from issuance of warrants							$ 25,000								$ 99,998	$ 25,000
Number of warrants exercised (in shares)									0			0			0
Treasury stock value									$ 53,193			$ 53,193		$ 53,193	$ 53,193
Common stock, par value (in dollars per share)									$ 0.001			$ 0.001		$ 0.001	$ 0.001
Exercise of stock options (in shares)															427,001
Change in ownership interest in consolidated VIE												$ 0
Dividends declared by variable interest entity to noncontrolling shareholders													$ 40,520
Dividends paid to noncontrolling shareholders															$ 41,514	0
Non- controlling Interest
Class Of Stock [Line Items]
Change in ownership interest in consolidated VIE		$ 3,100										3,133
Dividends declared by variable interest entity to noncontrolling shareholders													40,520
Additional Paid-In Capital
Class Of Stock [Line Items]
Change in ownership interest in consolidated VIE		$ (3,100)										(3,120)
Visirna Therapeutics, Inc.
Class Of Stock [Line Items]
Ownership interest percentage		56.38%															66.25%
Variable Interest Entity, Primary Beneficiary
Class Of Stock [Line Items]
Exercise of stock options (in shares)		14,000,000
Cash dividends													$ 100,000
Dividends declared by variable interest entity to noncontrolling shareholders			$ 40,500
Dividends paid									$ 94,800
Dividends paid to noncontrolling shareholders									38,400
Exercise prices paid netted against dividends payable									3,100
Dividends payable									$ 2,100			$ 2,100			$ 2,100
Pre-Funded Warrants
Class Of Stock [Line Items]
Number of warrants exercised (in shares)									0			0			0
Sarepta \| Sarepta Collaboration Agreement
Class Of Stock [Line Items]
Net proceeds from sale of stock						$ 325,000
Common stock repurchased (in shares)				2,660,989							2,660,989
Common stock repurchase price per share (in dollars per share)				$ 18.79
Value of stock repurchased				$ 50,000							$ 50,000			$ 50,000
Proceeds from collaboration arrangements				50,000	$ 500,000					$ 50,000	50,000			$ 50,000
Milestone payment due from collaborative agreement				100,000
Treasury stock value				53,200							53,200
Gain on settlement of treasury stock				$ 3,200							$ 3,200
Arrowhead Pharmaceuticals, Inc. \| Variable Interest Entity, Primary Beneficiary
Class Of Stock [Line Items]
Dividends paid									$ 56,400
Private Placement
Class Of Stock [Line Items]
Shares of common stock issued (in shares)							11,926,301
Common stock sold price (in dollars per share)							$ 27.25
Net proceeds from sale of stock							$ 325,000
ATM Agreement
Class Of Stock [Line Items]
Shares of common stock issued (in shares)												0	689,000
Net proceeds from sale of stock													$ 46,800
Proceeds from issuance of common stock													$ 48,200		$ 48,156	241,388
ATM Agreement \| Maximum
Class Of Stock [Line Items]
Common stock shares value reserved for future issuance								$ 500,000
Percentage of commission to sales agent								3.00%
Underwriting Public Offering
Class Of Stock [Line Items]
Shares of common stock issued (in shares)	2,015,505
Common stock sold price (in dollars per share)	$ 64.50
Net proceeds from sale of stock	$ 216,600
Proceeds from issuance of common stock															$ 130,000	$ 0
Common stock, par value (in dollars per share)	$ 0.001
Proceeds from equity offering	$ 230,000
Underwriting Public Offering \| Pre-Funded Warrants
Class Of Stock [Line Items]
Warrant exercise price (in dollars per share)	$ 0.001
Number of securities called by warrants (in shares)	1,550,387
Class of warrant or right, offering price of warrants or rights	$ 64.499
2013 and 2021 Incentive Plans and Other Inducement Grants
Class Of Stock [Line Items]
Common stock, share reserve for issuance (in shares)									18,192,429			18,192,429		9,851,400	18,192,429

Collaboration and License Agreements - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Movement In Contract With Customer Liability [Roll Forward]
Balance at beginning of period	$ 155,931	$ 0	$ 2,399	$ 0
Deferred revenue additions	63,434	585,974	480,672	585,974
Revenue recognized	(62,207)	(542,706)	(325,913)	(542,706)
Balance at end of period	157,158	43,268	157,158	43,268
Plus contract assets included in other current assets	0	0	0	0	$ 0
Less deferred revenue, current	(108,543)	(43,268)	(108,543)	(43,268)	(2,399)
Deferred revenue, non-current	$ 48,615	$ 0	$ 48,615	$ 0	$ 0

Stockholders' Equity - Schedule of Shares of Common Stock and Preferred Stock (Details) - $ / shares shares in Thousands	Mar. 31, 2026	Sep. 30, 2025
Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	290,000	290,000
Common stock, shares issued (in shares)	143,232	138,363
Common stock, shares outstanding (in shares)	140,571	135,702
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000	5,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Finite Lived Intangible Assets [Line Items]
Net Carrying Amount	$ 6,011	$ 6,861
Novartis
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	24,857	24,857
Accumulated Amortization	18,846	17,996
Impairment	0	0
Net Carrying Amount	6,011	6,861
Novartis \| Patents
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	21,728	21,728
Accumulated Amortization	17,201	16,426
Impairment	0	0
Net Carrying Amount	$ 4,527	$ 5,302
Useful Lives	14 years	14 years
Novartis \| License
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,129	$ 3,129
Accumulated Amortization	1,645	1,570
Impairment	0	0
Net Carrying Amount	$ 1,484	$ 1,559
Useful Lives	21 years	21 years

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Subsequent Events (Details) - Subsequent Event $ in Millions	May 04, 2026 USD ($)	Apr. 27, 2026 USD ($) ft² option
Madrigal Pharmaceuticals, Inc. \| Madrigal Licensing Agreement
Subsequent Event [Line Items]
Initial transaction price	$ 25.0
Future potential milestone payments	$ 975.0
Corporate Headquarters In Pasadena
Subsequent Event [Line Items]
Operating lease, not yet commenced, lease space (in sq ft) \| ft²		98,444
Operating lease, not yet commenced, lease term		7 years 8 months
Operating lease, not yet commenced, number of renewal options \| option		2
Operating lease, not yet commenced, renewal lease term		5 years
Expected rent obligations		$ 50.3

Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Mar. 31, 2026	Sep. 30, 2025
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	290,000	290,000
Common stock, shares issued (in shares)	143,232	138,363
Common stock, shares outstanding (in shares)	140,571	135,702
Treasury stock (in shares)	2,661	2,661

Collaboration and License Agreements - Novartis Pharma AG (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Oct. 23, 2025 USD ($)	Aug. 29, 2025 USD ($) obligation	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue			$ 73,737	$ 542,709	$ 337,770	$ 545,209
Contract liabilities included in deferred revenue, current			108,543	43,268	108,543	43,268	$ 2,399
Contract liabilities included in deferred revenue, non-current			48,615	$ 0	48,615	$ 0	$ 0
Novartis
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities included in deferred revenue, current			97,400		97,400
Contract liabilities included in deferred revenue, non-current			48,600		$ 48,600
Novartis \| Novartis Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct performance obligations \| obligation		1
Upfront payment	$ 200,000
Enrollment related milestone payments		$ 30,000
Variable consideration	32,000
Total transaction price	$ 232,000
Collaboration agreement termination notice period prior to any regulatory approval of a licensed product		30 days
Collaboration arrangement, written notice period		180 days
Revenue			$ 20,500
Novartis \| Novartis Collaboration Agreement \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payments		$ 175,000
Sales-related milestone payments		285,000
Novartis \| Novartis Collaboration Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payments		245,000
Sales-related milestone payments		$ 370,000

Leases - Narrative (Details)	3 Months Ended			6 Months Ended		15 Months Ended
Leases - Narrative (Details)	Mar. 31, 2026 USD ($) ft² option	Mar. 31, 2025 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2026 USD ($) ft² option	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Jun. 29, 2025 ft²
Lessee Lease Description [Line Items]
Short-term lease cost \| $	$ 0	$ 0		$ 0	$ 0
California \| Corporate Headquarters In Pasadena
Lessee Lease Description [Line Items]
Operating lease, lease space (in sq ft) \| ft²	49,000			49,000
Number of options to renew \| option	1			1
Operating lease renewal term	5 years			5 years
California \| Research Facility in San Diego
Lessee Lease Description [Line Items]
Operating lease, lease space (in sq ft) \| ft²	144,000			144,000
Operating lease renewal term	10 years			10 years
Lease extension period	12 months			12 months
Lease term	15 years			15 years
Proceeds from additional tenant improvement allowance \| $			$ 3,100,000			$ 30,800,000
California \| Research Facility in San Diego \| Maximum
Lessee Lease Description [Line Items]
Number of options to renew \| option	1			1
Wisconsin \| Research Facility in Madison
Lessee Lease Description [Line Items]
Operating lease, lease space (in sq ft) \| ft²	110,956			110,956			107,000
Number of options to renew \| option	2			2
Operating lease renewal term	5 years			5 years

Collaboration and License Agreements - Takeda Pharmaceutical Company Limited (Details)	1 Months Ended
	Jan. 31, 2021 USD ($)	Oct. 31, 2020 bundle obligation	Mar. 31, 2026 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2023 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments			$ 15,200,000,000
Contract liabilities included in deferred revenue, current			108,543,000	$ 2,399,000	$ 43,268,000
Accrued expenses			76,585,000	$ 90,419,000
Takeda Pharmaceutical Company Limited \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle \| bundle		1
Number of distinct performance obligations \| obligation		1
Initial transaction price	$ 300,000,000.0
Milestone payment						$ 40,000,000.0
Contract liabilities included in deferred revenue, current			0
Accrued expenses			32,700,000
Takeda Pharmaceutical Company Limited \| Minimum \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales		20.00%
Takeda Pharmaceutical Company Limited \| Maximum \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales		25.00%
Development regulatory and sales milestones payments			$ 527,500,000

Equity Method Investment	6 Months Ended
Equity Method Investment	Mar. 31, 2026
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	EQUITY METHOD INVESTMENT On January 15, 2026, the Company, through its consolidated variable interest entity, Visirna, entered into and closed an Asset Transfer Agreement (the “Asset Transfer Agreement”) with Bisirna, pursuant to which the Company received 26,500,000 ordinary shares and 6,625,000 Series A preferred shares in exchange for in‑process research and development (“IPR&D”) assets transferred from Visirna to Bisirna. As a result of the asset transfer, the Company recognized a gain of $19.0 million in other income in the accompanying consolidated statements of operations and comprehensive (loss) income for the three months ended March 31, 2026. The Company evaluated whether there was a basis difference between the carrying value and fair value of its proportionate share of Bisirna’s underlying net assets. As Bisirna was not deemed a business as defined in ASC 805, Business Combinations, the Company immediately expensed the basis difference to the extent it related to acquired IPR&D assets. As of March 31, 2026, the Company held a 25.29% voting interest in Bisirna and one seat on Bisirna’s board of directors. The Company accounts its ownership in Bisirna under the equity method. As of March 31, 2026, the carrying value of the Company’s investment in Bisirna was $4.7 million, which was included in other assets in the accompanying consolidated balance sheets.

Collaboration and License Agreements - Sarepta Therapeutics, Inc. (Details) $ in Thousands					1 Months Ended			3 Months Ended			6 Months Ended
	Aug. 13, 2025 USD ($) shares	Feb. 14, 2025 USD ($)	Feb. 07, 2025 USD ($)	Nov. 25, 2024 USD ($) obligation program	Feb. 28, 2026 USD ($)	Nov. 30, 2025 USD ($)	Aug. 31, 2025 USD ($) shares	Mar. 31, 2026 USD ($) obligation	Sep. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Treasury stock value								$ 53,193	$ 53,193		$ 53,193
Revenue								73,737		$ 542,709	337,770	$ 545,209
Accounts receivable								15,685	6,824		15,685
Contract liabilities included in deferred revenue, current								108,543	2,399	$ 43,268	108,543	$ 43,268
Sarepta
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable								14,000			14,000
Contract liabilities included in deferred revenue, current								$ 11,100			$ 11,100
Sarepta \| Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations \| obligation				17
Upfront payment	$ 50,000	$ 500,000			$ 50,000		$ 50,000		50,000
Net proceeds from sale of stock			$ 325,000
Equity premium			$ 83,600
Annual fees				$ 250,000
Annual installment				$ 50,000
Annual installments period				5 years
Total transaction price				$ 904,900
Fixed consideration				833,600
Variable consideration				$ 71,200
Development milestone payments						$ 200,000	100,000		100,000
Value of stock repurchased	$ 50,000						$ 50,000		$ 50,000
Number of collaboration programs \| program				13
Collaboration agreement termination notice period prior to any regulatory approval of a licensed product				30 days
Common stock repurchased (in shares) \| shares	2,660,989						2,660,989
Treasury stock value	$ 53,200						$ 53,200
Gain on settlement of treasury stock	$ 3,200						$ 3,200
Number of distinct performance obligations \| obligation								4
Revenue								$ 37,400
Sarepta \| Sarepta Clinical Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue								$ 4,300
Sarepta \| Maximum \| Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of new target programs \| program				6
Regulatory milestone payments				$ 180,000
Sales-related milestone payments				700,000
Sarepta \| Minimum \| Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payments				110,000
Sales-related milestone payments				$ 500,000

Organization and Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2024
Accounting Policies [Abstract]
Cash, cash equivalents and restricted cash	$ 188,517	$ 226,548	$ 185,709	$ 102,685
Restricted cash	1,900
Available-for-sale securities, at fair value and short-term investments	1,595,574	$ 692,818
Development regulatory and sales milestones payments	$ 15,200,000

Net (Loss) Income Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	13,684	6,049	10,038	5,317
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	1,022	760	1,160	750
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	5,605	5,289	5,389	4,567
If-converted common stock from convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	7,057	0	3,489	0

Collaboration and License Agreements

6 Months Ended

Mar. 31, 2026

Collaboration And License Agreements [Abstract]

Collaboration and License Agreements

COLLABORATION AND LICENSE AGREEMENTS

The following table provides a summary of revenue recognized from our collaboration and license agreements:


	Three Months Ended March 31,				Sixth Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
GSK	$	—	$	3	$	—	$	2,503
Sarepta	41,735		542,706		271,199		542,706
Novartis	20,471		—		54,713		—
Sanofi	10,533		—		10,742		—
Total	$	72,739	$	542,709	$	336,654	$	545,209

The following table summarizes the balance of receivables, contract assets and contract liabilities related to the Company’s collaboration and license agreements, which, as of March 31, 2026, relate solely to the Company’s agreements with Sarepta, Novartis and Sanofi:


	March 31, 2026		September 30, 2025
	(in thousands)
Receivables included in accounts receivable	$	14,512	$	6,824
Contract assets included in other current assets	$	—	$	—
Contract liabilities included in deferred revenue, current	$	108,543	$	2,399
Contract liabilities included in deferred revenue, non-current	$	48,615	$	—

Deferred revenue consisted of the following:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Balance at beginning of period	$	155,931	$	—	$	2,399	$	—
Deferred revenue additions	63,434		585,974		480,672		585,974
Revenue recognized	(62,207)		(542,706)		(325,913)		(542,706)
Balance at end of period	157,158		43,268		157,158		43,268
Plus contract assets included in other current assets	—		—		—		—
Less deferred revenue, current	(108,543)		(43,268)		(108,543)		(43,268)
Deferred revenue, non-current	$	48,615	$	—	$	48,615	$	—

GlaxoSmithKline Intellectual Property (No. 3) Limited (“GSK”)

GSK-HSD License Agreement

On November 22, 2021, GSK and the Company entered into an Exclusive License Agreement (the “GSK-HSD License Agreement”). Under the GSK-HSD License Agreement, GSK has received an exclusive license for GSK-4532990 (formerly ARO-HSD). The exclusive license is worldwide with the exception of greater China. GSK is wholly responsible for all clinical development and commercialization of GSK-4532990 in its territory.

The Company has completed its performance obligation related to the upfront payment under the GSK-HSD License Agreement, and accordingly the $120.0 million upfront payment was fully recognized in the year ended September 30, 2022. Further, GSK dosed the first patient in a Phase 2b trial in March 2023 and paid a $30.0 million milestone payment to the Company in the third quarter of fiscal 2023.

The Company is eligible for an additional payment of $100.0 million upon achieving the first patient dosed in a Phase 3 trial. Furthermore, should the Phase 3 trial read out positively, and the potential new medicine receives regulatory approval in major markets, the deal provides for commercial milestone payments to the Company of up to $190.0 million at first commercial sale, and up to $590.0 million in sales-related milestone payments. The Company is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent.

As of March 31, 2026, the Company had no contract assets and liabilities recorded.

GSK-HBV Agreement

On December 11, 2023, the Company entered into an Amended and Restated License Agreement with GSK (the “GSK-HBV Agreement”) pursuant to which GSK received a worldwide, exclusive license to develop and commercialize daplusiran/tomligisiran (GSK5637608, formerly JNJ-3989), the Company’s third-generation subcutaneously administered RNAi therapeutic candidate being developed as a potential therapy for patients with chronic hepatitis B virus infection.

Under the terms of the GSK-HBV Agreement, the Company received $2.7 million in December 2023 upon signing the amended GSK-HBV Agreement. Further, GSK dosed the fifth patient in a Phase 2 trial in December 2024, triggering a $2.5 million milestone payment to the Company which was paid in the second quarter of fiscal 2025. The Company is eligible to receive up to $830.0 million in development and sales milestone payments under the GSK-HBV Agreement.

As of March 31, 2026, the Company had no contract assets and liabilities recorded.

Takeda Pharmaceutical Company Limited (“Takeda”)

In October 2020, Takeda and the Company entered into an Exclusive License and Co-Funding Agreement (the “Takeda License Agreement”). Under the Takeda License Agreement, Takeda and the Company will co-develop the Company’s fazirsiran program (formerly TAK-999 and ARO-AAT), the Company’s second-generation subcutaneously administered RNAi therapeutic candidate being developed as a treatment for liver disease associated with alpha-1 antitrypsin deficiency. Within the United States, fazirsiran, if approved, will be co-commercialized under a 50/50 profit sharing structure. Outside the United States, Takeda received an exclusive license to commercialize fazirsiran and will lead the global commercialization strategy, while the Company will be eligible to receive tiered royalties of 20% to 25% on net sales.

The Company determined that the key deliverables included the license and certain research and development services including the Company’s responsibilities to complete the initial portion of the SEQUOIA study, to complete the ongoing Phase 2 AROAAT2002 study, and to ensure certain manufacturing of fazirsiran drug product is completed and delivered to Takeda (the “Takeda R&D Services”). Due to the specialized and unique nature of these Takeda R&D Services and their direct relationship with the license, the Company determined that these deliverables represent one distinct bundle and, thus, one performance obligation. Takeda is responsible for managing clinical development and commercialization outside the United States. Within the United States, the Company and Takeda are responsible in the co-development and co-commercialization efforts. The Company considers the collaborative activities, including the co-development and co-commercialization, to be a separate unit of account within Topic 808, and as such, these co-funding amounts are recorded as research and development expenses or selling, general and administrative expenses, as appropriate.

Under the terms of the Takeda License Agreement, the Company received $300.0 million as an upfront payment in January 2021 and an additional $40.0 million upon Takeda’s initiation of a Phase 3 REDWOOD clinical study of fazirsiran in March 2023, and is eligible to receive up to $527.5 million in additional potential development, regulatory and commercial milestones.

The Company allocated the total $300.0 million initial transaction price to its one distinct performance obligation for the fazirsiran license and the associated Takeda R&D Services. The Company has substantially completed its performance obligation under the Takeda License Agreement by December 31, 2023. As such, all revenue has been fully recognized as of December 31, 2023. There were no further deferred revenue and contract liabilities as of March 31, 2026.

As of March 31, 2026, the accrued expense balance is $32.7 million that was primarily driven by co-development and co-commercialization activities.

Amgen Inc. (“Amgen”)

In September 2016, Amgen and the Company entered into two collaboration and license agreements and a common stock purchase agreement. Under the Second Collaboration and License Agreement (the “Olpasiran Agreement”), Amgen received a worldwide, exclusive license to the Company’s novel RNAi olpasiran (previously referred to as AMG- 890 or ARO-LPA) program. These RNAi molecules are designed to reduce elevated lipoprotein(a), which is a genetically validated, independent risk factor for atherosclerotic cardiovascular disease. Under the Olpasiran Agreement, Amgen is wholly responsible for clinical development and commercialization.

The Company has substantially completed its performance obligations under the Olpasiran Agreement. There were no contract assets and liabilities recorded as of March 31, 2026.

In November 2022, Royalty Pharma Investments 2019 ICAV (“Royalty Pharma”) and the Company entered into a Royalty Purchase Agreement with Royalty Pharma (the “Royalty Pharma Agreement”). In consideration for the payments

under the Royalty Pharma Agreement, Royalty Pharma is entitled to receive all royalties otherwise payable by Amgen to the Company under the Olpasiran Agreement. The Company remains eligible to receive up to an additional $485.0 million in remaining development, regulatory and sales milestone payments payable from Amgen and Royalty Pharma. See Note 12.

Sarepta Therapeutics, Inc.

On November 25, 2024, the Company entered into an Exclusive License and Collaboration Agreement (the “Sarepta Collaboration Agreement”) with Sarepta for the development and commercialization of multiple clinical and preclinical programs in rare, genetic diseases of the muscle, central nervous system, and lungs. The Company concurrently entered into a Stock Purchase Agreement (the “Stock Purchase Agreement”) with Sarepta (see Note 6).

Under the Sarepta Collaboration Agreement, Sarepta received an exclusive sublicensable worldwide license to SRP-1001 (formerly ARO-DUX4), SRP-1003 (formerly ARO-DM1), SRP-1002 (formerly ARO-MMP7), and SRP-1004 (formerly ARO-ATXN2) clinical stage programs (the “C1” programs). Sarepta also received an exclusive sublicensable worldwide license to the Company’s ARO-HTT, ARO-ATXN1, and ARO-ATXN3 preclinical stage programs (the “C2” programs). The Company will perform certain research and development activities for the C1 and C2 programs.

Further, Sarepta may select up to six gene targets for which the Company will perform discovery, optimization and preclinical development activities to identify RNAi compounds against each selected target (the “C3” programs). Upon target acceptance, Sarepta will receive an exclusive license to the Company’s intellectual property rights to exploit compounds directed to those targets and is wholly responsible for clinical development and commercialization of each compound after the Company delivers a Clinical Trial Application ready data package (the "CTA package").

The Company identified 17 performance obligations under the Sarepta Collaboration Agreement. The four C1 licenses are distinct performance obligations from the four C1 research and development performance obligations since the customer can use and benefit from the licenses separately. The performance obligations for the licenses were satisfied in the second quarter of fiscal 2025 upon delivery and the research and development performance obligations will be satisfied as the work is performed. The remaining nine performance obligations include three C2 preclinical stage program licenses and research and development activities, and six C3 discovery target licenses and research and development activities. Each of the three C2 programs and the six C3 programs were determined to represent one performance obligation, as the customer cannot benefit from the use of the product license at the point of transfer until the specified research and development activities are performed. As such, each of the C2 and C3 product licenses and respective research and development work will be combined to form one performance obligation. For these nine performance obligations, revenue is recognized over time as the work is performed.

For performance obligations recognized over time, the estimated performance period over which revenue will be recognized is determined to be the period over which the Company estimates it will perform the research and development activities. The Company determined that the most appropriate method of measuring progress for these performance obligations is an input method based on research and development costs in the program budget. Accordingly, the Company has estimated the total cost required to complete its obligation and recognized an amount of revenue equal to the proportion of services performed, which is reassessed on an ongoing basis as the program progresses. In the period an agreement expires or is terminated, remaining deferred revenue, if any, is recognized as revenue.

Under the terms of the Sarepta Collaboration Agreement, the Company received an upfront payment of $500.0 million on February 14, 2025. In addition, on February 7, 2025, the Company received $325.0 million in the form of an equity investment under the Stock Purchase Agreement. Based upon the Company's share price on February 7, 2025, (the “Closing Date”), the difference between the $325.0 million and the fair value of the shares on the Closing date resulted in a premium of $83.6 million. The premium is included as part of the total consideration of the Sarepta Collaboration Agreement for revenue recognition purposes. The Company is entitled to receive $250.0 million to be paid in annual installments of $50.0 million over the first five years of the agreement. The Company is also eligible to receive reimbursement of certain costs related to carrying out the research and development activities for the C1 programs. At contract inception, the transaction price was determined to be $904.9 million, consisting of fixed consideration of $833.6 million and estimated variable consideration of $71.2 million. The fixed consideration was allocated to all performance obligations based on their relative standalone selling price. The variable consideration was allocated to the performance obligation to which it is determined to be related, which is the respective development work that is being reimbursed. Standalone selling prices for the product licenses were determined using an adjusted market-based approach through the net present value of the expected future cash flows for each program. Standalone selling prices for the research and development work were determined based on an expected cost plus margin approach. During the fourth quarter of fiscal 2025, the Company earned the first of two ARO-DM1 development milestone payment of $100.0 million, of which $50.0 million was settled in cash and the remaining $50.0 million was settled through the repurchase of Company's common stock. In November 2025, the Company earned the second of two $200.0 million ARO-DM1 development

milestone payments and received the milestone payment in January 2026. In February 2026, the Company earned and received the first installment of the annual fee payment of $50.0 million.

The Company estimates the stand-alone selling price for each distinct performance obligation, which involves assumptions that may require significant judgment. The Company’s estimates of the stand-alone selling price for license-related performance obligations includes forecasted revenues and expenses, phase dates, probability of success, development timelines, and the discount rate. The estimates of the stand-alone selling price for research and development performance obligations generally include forecasting the expected costs of satisfying a performance obligation at market rates. The Company identified a discount based on the difference between the aggregate stand-alone selling price and the transaction price for accounting revenue recognition purposes. The Company allocated the discount proportionally to each of the performance obligations based upon their standalone selling price.

For each of the 13 programs, the Company is also eligible to receive regulatory milestone payments between $110.0 million and $180.0 million per program. Variable consideration associated with the milestones that may be achieved will be allocated to the performance obligation to which it is determined to be related, which will be the respective programs to which the milestones relate. The Company will recognize the regulatory milestones as revenue in the periods the underlying milestone events are achieved as achievement of the milestone events are highly susceptible to factors outside of the entity's influence and therefore there is a possibility that the milestone event will not be achieved.

The Company is also eligible to receive sales milestone payments between $500.0 million and $700.0 million per program as well as tiered royalties on net sales of licensed products of up to the low double digits, subject to the terms and conditions of the Sarepta Collaboration Agreement. The Company has applied the sales-based scope exception to the sales milestones and the royalty-based payments.

The Sarepta Collaboration Agreement commenced in February 2025 and may be terminated by either party in the event of a material breach as defined therein. In addition, Sarepta may voluntarily terminate the Sarepta Collaboration Agreement with 30 days' written notice to the Company if terminated prior to any regulatory approval of a licensed product. Unless earlier terminated, the Sarepta Collaboration Agreement expires on a product-by-product and country-by-country basis, upon the date of expiration of the relevant royalty term for such product in such country.

In August 2025, the Company repurchased 2,660,989 shares of its common stock from Sarepta in connection with the $100.0 million DM1 first development milestone under the Sarepta Collaboration Agreement. The repurchase satisfied $50.0 million of the milestone payment through delivery of the Company’s common stock, with the remaining $50.0 million settled in cash. The shares were recorded as treasury stock at their fair value of $53.2 million, resulting in a $3.2 million gain on settlement. The repurchased shares are presented as a reduction to total stockholders’ equity in accordance with ASC 505-30.

For the three months ended March 31, 2026, Sarepta exercised its contractual step‑in right under the Sarepta Collaboration Agreement with respect to certain C1 programs, pursuant to which Sarepta will assume responsibility for ongoing clinical trials for such programs on mutually agreed transition dates. Sarepta’s exercise of the step‑in right represents a contract modification under ASC 606, as it reduces both the scope of the Company’s remaining obligations and the amount of variable consideration related to reimbursable research and development costs for the affected C1 programs. The Company evaluated the modification and determined that the remaining research and development activities to be performed after the modification are not distinct from those performed prior to the modification and, accordingly, the modification is accounted for as part of the original performance obligation through a cumulative catch‑up adjustment. For the three months ended March 31, 2026, the Company did not record a cumulative catch‑up adjustment to revenue, as the revised C1 reimbursement budgets remain subject to mutual agreement between Sarepta and the Company. As a result, the associated variable consideration is constrained until the uncertainty is resolved. Any cumulative catch‑up adjustment will be recognized in future periods when the uncertainty related to the variable consideration is subsequently resolved. The contract modification did not impact revenue previously recognized related to the four C1 licenses, which were delivered as distinct performance obligations.

In December 2025, pursuant to the Sarepta Collaboration Agreement, the Company entered into a clinical supply agreement with Sarepta (the “Sarepta Clinical Supply Agreement”), whereby the Company is responsible for manufacturing and supplying certain materials to Sarepta for specified activities. For the three months ended March 31, 2026, the Company recorded $37.4 million and $4.3 million in revenue under the Sarepta Collaboration Agreement and the Sarepta Clinical Supply Agreement, respectively. As of March 31, 2026, the Company held $14.0 million in accounts receivable and $11.1 million in current deferred revenue, relating to the Sarepta Collaboration Agreement and the Sarepta Clinical Supply Agreement. The recognition of the remaining revenue for the performance obligations is dependent upon the time it takes to complete the respective research and development activities and in consideration of the timing of the selection of the rest of the targets within the C3 programs.

Novartis Pharma AG

On August 29, 2025, the Company entered into an Exclusive License and Collaboration Agreement (the “Novartis Collaboration Agreement”) with Novartis for the development and commercialization of multiple preclinical programs in rare, genetic diseases of the central nervous system.

Under the Novartis Collaboration Agreement, Novartis received an exclusive sublicensable worldwide license to the Company’s ARO-SNCA preclinical stage program. The Company will perform certain research and development activities for the program.

Further, Novartis has selected additional gene targets ("Collaboration Target") for which the Company has accepted and will perform discovery, optimization and preclinical development activities to identify RNAi compounds against each selected target. Novartis has received an exclusive license to the Company’s intellectual property rights to exploit compounds directed to those targets (the "CT" programs) and is wholly responsible for clinical development and commercialization of each compound after the Company delivers a Clinical Trial Application ready data package (the "CTA package").

The Company identified multiple performance obligations under the Novartis Collaboration Agreement. They include the ARO-SNCA preclinical stage program licenses and research and development activities, and CT programs licenses and research and development activities. Each of the programs were determined to represent one performance obligation, as the customer cannot benefit from the use of the product license at the point of transfer until the specified research and development activities are performed. As such, each of the product licenses and respective research and development work will be combined to form one performance obligation. For these performance obligations, revenue is recognized over time as the work is performed.

Under the terms of the Novartis Collaboration Agreement, the Company received an upfront payment of $200.0 million on October 23, 2025. The Company is also eligible to receive research milestone payments of up to $30.0 million and reimbursement of certain costs related to carrying out the research, development and manufacturing activities for the programs. The fixed consideration of $200.0 million and an estimated variable consideration of $32.0 million for a total of $232.0 million were allocated to all performance obligations based on their relative standalone selling price. Standalone selling prices for the product licenses were determined using an adjusted market-based approach through the net present value of the expected future cash flows for each program. The standalone selling prices for the research and development work were determined based on an expected cost plus margin approach.

The Company estimates the stand-alone selling price for each distinct performance obligation, which involves assumptions that may require significant judgment. The Company’s estimates of the stand-alone selling price for license-related performance obligations includes forecasted revenues, phase dates, probability of success, development timelines, and the discount rate. The estimates of the stand-alone selling price for research and development performance obligations generally include forecasting the expected costs of satisfying a performance obligation at market rates. The Company identified a premium based on the difference between the aggregate stand-alone selling price and the transaction price for accounting revenue recognition purposes. The Company allocated the premium proportionally to each of the performance obligations based upon their standalone selling price.

Further, for each of the programs, the Company is eligible to receive regulatory milestone payments between $175.0 million and $245.0 million per program. Variable consideration associated with the milestones that may be achieved will be allocated to the performance obligation to which it is determined to be related, which will be the respective programs to which the milestones relate. The Company will recognize the regulatory milestones as revenue in the periods the underlying milestone events are achieved as achievement of the milestone events are highly susceptible to factors outside of the entity's influence and therefore there is a possibility that the milestone event will not be achieved.

The Company is also eligible to receive sales milestone payments between $285.0 million and $370.0 million per program as well as tiered royalties on net sales of licensed products of up to the low double digits, subject to the terms and conditions of the Novartis Collaboration Agreement. The Company has applied the sales-based scope exception to the sales milestones and the royalty-based payments.

The Novartis Collaboration Agreement commenced in October 2025 and may be terminated by either party in the event of a material breach as defined therein. In addition, Novartis may voluntarily terminate the Novartis Collaboration Agreement with 30 days' written notice to the Company if terminated prior to any regulatory approval of a licensed product, or with 180 days' written notice to the Company if terminated after any regulatory approval of a licensed product. Unless earlier terminated, the Novartis Collaboration Agreement expires on a product-by-product and country-by-country basis, upon the date of expiration of the relevant royalty term for such product in such country.

For the three months ended March 31, 2026, the Company recorded $20.5 million in revenue from Novartis. As of March 31, 2026, the Company recorded $97.4 million in current deferred revenue and $48.6 million in non-current deferred revenue, related to the Novartis Collaboration Agreement. The recognition of the remaining revenue for the performance obligations is dependent upon the time it takes to complete the respective research and development activities.

Visirna Therapeutics Inc. (“Visirna”) and Genzyme Corporation (“Sanofi”)

On August 1, 2025, Visirna Therapeutics HK Limited (“Visirna HK”), a wholly owned subsidiary of Visirna Therapeutics, Inc, a majority owned subsidiary of the Company, entered into an Asset Purchase Agreement (the “Asset Purchase Agreement”) with Genzyme Corporation (“Sanofi”), a wholly owned subsidiary of Sanofi S.A., pursuant to which Visirna HK sold all of its assets and rights in investigational plozasiran to Sanofi, which included an assignment of Visirna HK’s rights (as successor by assignment from Visirna) to develop and commercialize investigational plozasiran in Greater China pursuant to that certain License Agreement by and between the Company and Visirna dated, April 25, 2022 (the “Visirna License Agreement”).

In connection with the Asset Purchase Agreement, the Company consented to the partial assignment of the Visirna License Agreement by Visirna HK to Sanofi (as so assigned, the “Sanofi License Agreement”), amongst other agreements between the Company and Visirna, effective as of the closing of the Asset Purchase Agreement. This agreement was not deemed a legal sale of intellectual property from the consolidated perspective of the Company. After giving effect to the Asset Purchase Agreement, Visirna HK retains rights to develop and commercialize in Greater China other cardiometabolic drugs licensed to it pursuant to the Visirna License Agreement.

Upon closing of the Asset Purchase Agreement, Visirna received an upfront payment of $130.0 million from Sanofi and is eligible to receive further development milestone payments of up to $265.0 million upon approval of plozasiran across various indications in mainland China.

Visirna identified the licenses as defined in the agreement as the performance obligations under the Asset Purchase Agreement. The performance obligations for the licenses was satisfied in the fourth quarter of fiscal 2025 upon delivery. The fixed consideration of $130.0 million was allocated to the performance obligations. The Company recognizes approval milestones as revenue in the periods the underlying milestone events are achieved as achievement of the milestone events are highly susceptible to factors outside of the entity's influence and therefore there is a possibility that the milestone events will not be achieved. The Company has also applied the sales-based scope exception to the royalty-based payments.

In January 2026, the NMPA approved REDEMPLO in Greater China, which triggered a $10.0 million milestone payment to Visirna. The Company is also eligible to receive royalties from Sanofi on net commercial product sales in Greater China under the Sanofi License Agreement. For the three months ended March 31, 2026, the Company recorded $10.5 million in revenue and $0.5 million in accounts receivable as of March 31, 2026 under the Sanofi License Agreement. The Sanofi License Agreement may be terminated by either party in the event of a material breach as defined therein. Unless earlier terminated, the Sanofi License Agreement expires on a product-by-product basis, upon the date of expiration of the relevant royalty term for such product in Greater China.

Intangible Assets (Tables)

6 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

The following table presents the components of intangible assets:


	Gross Carrying Amount		Accumulated Amortization		Impairment		Net Carrying Amount		Useful Lives
	(in thousands)								(in years)
As of March 31, 2026
Patents	$	21,728	$	17,201	$	—	$	4,527	14
License	3,129		1,645		—		1,484		21
Total intangible assets, net	$	24,857	$	18,846	$	—	$	6,011

As of September 30, 2025
Patents	$	21,728	$	16,426	$	—	$	5,302	14
License	3,129		1,570		—		1,559		21
Total intangible assets, net	$	24,857	$	17,996	$	—	$	6,861

Schedule of Intangible Assets Future Amortization Expense

The following table presents the estimated future amortization expense related to intangible assets as of March 31, 2026:


	Amortization Expense
Year Ending September 30,	(in thousands)
2026 (remainder)	$	850
2027	1,700
2028	1,700
2029	795
2030	149
Thereafter	817
Total	$	6,011

Consolidated Statements of Operations and Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Income Statement [Abstract]
Revenue	$ 73,737	$ 542,709	$ 337,770	$ 545,209
Operating expenses:
Research and development	173,253	133,102	350,456	270,104
Selling, general and administrative	41,744	28,405	87,765	55,315
Total operating expenses	214,997	161,507	438,221	325,419
Operating (loss) income	(141,260)	381,202	(100,451)	219,790
Other income (expense):
Interest income	16,869	9,615	26,560	17,217
Interest expense	(23,846)	(21,639)	(46,351)	(43,285)
Loss on equity method investment	(6,719)	0	(6,719)	0
Gain on VIE's sale of IPR&D assets	19,000	0	19,000	0
Other, net	(1,609)	438	(1,332)	779
Total other income (expense)	3,695	(11,586)	(8,842)	(25,289)
(Loss) income before income tax expense and noncontrolling interest	(137,565)	369,616	(109,293)	194,501
Income tax expense	7	1,753	35	1,856
Net (loss) income including noncontrolling interest	(137,572)	367,863	(109,328)	192,645
Net loss attributable to noncontrolling interest, net of tax	(4,840)	(2,582)	(7,409)	(4,715)
Net (loss) income attributable to Arrowhead Pharmaceuticals, Inc.	$ (132,732)	$ 370,445	$ (101,919)	$ 197,360
Net (loss) income per share attributable to Arrowhead Pharmaceuticals, Inc.:
Basic (in dollars per share)	$ (0.93)	$ 2.78	$ (0.73)	$ 1.53
Diluted (in dollars per share)	$ (0.93)	$ 2.75	$ (0.73)	$ 1.52
Weighted-average shares used in calculating
Basic (in shares)	142,417	133,363	139,762	129,059
Diluted (in shares)	142,417	134,484	139,762	130,265
Comprehensive (loss) income:
Net (loss) income including noncontrolling interest	$ (137,572)	$ 367,863	$ (109,328)	$ 192,645
Other comprehensive (loss) income, net of tax:
Unrealized (losses) gains on available-for-sale securities	(6,934)	653	(6,788)	146
Foreign currency translation adjustments	990	(400)	1,100	(506)
Total other comprehensive (loss) income	(5,944)	253	(5,688)	(360)
Comprehensive (loss) income	(143,516)	368,116	(115,016)	192,285
Comprehensive loss attributable to noncontrolling interest	(4,425)	(2,582)	(6,966)	(4,715)
Comprehensive (loss) income attributable to Arrowhead Pharmaceuticals, Inc.	$ (139,091)	$ 370,698	$ (108,050)	$ 197,000

Investments - Schedule of Contract Maturity of Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Investments, Debt and Equity Securities [Abstract]
Within one year	$ 579,223	$ 224,328
After one to two years	566,425	468,490
After two to three years	449,926	0
Total current Investments, Fair Value	$ 1,595,574	$ 692,818

Investments

6 Months Ended

Mar. 31, 2026

Investments, Debt and Equity Securities [Abstract]

Investments

INVESTMENTS

The Company’s investments consisted of the following:


	As of March 31, 2026
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	1,598,704	$	1,091	$	(4,943)	$	1,594,852

Short‑term investments	722		—		—		722
Total current investments	$	1,599,426	$	1,091	$	(4,943)	$	1,595,574


	As of September 30, 2025
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	689,882	$	2,956	$	(20)	$	692,818

Total current investments	$	689,882	$	2,956	$	(20)	$	692,818

The following table summarizes the contract maturity of the available-for-sale securities and short-term investments as of:


	March 31, 2026		September 30, 2025
	(in thousands)


Within one year	$	579,223	$	224,328
After one to two years	566,425		468,490
After two to three years	449,926		—
Total	$	1,595,574	$	692,818

As of March 31, 2026 and September 30, 2025, the gross unrealized losses were immaterial. The Company has determined that the available-for-sale securities that were in an unrealized loss position did not have any credit loss impairment as of March 31, 2026 and 2025.

Balance Sheet Accounts

6 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Accounts

BALANCE SHEET ACCOUNTS

Property, Plant and Equipment

The following table summarizes the Company’s major classes of property, plant and equipment:


	March 31, 2026		September 30, 2025
	(in thousands)
Land	$	2,996	$	2,996
Buildings	252,932		251,317
Research equipment	62,685		62,758
Manufacturing equipment	24,726		18,588
Furniture	5,594		5,594
Computers and software	970		1,064
Leasehold improvements	104,448		104,425
Construction in progress	11,756		15,942
	466,107		462,684
Less: Accumulated depreciation and amortization	(91,285)		(80,169)
Property, plant and equipment, net	$	374,822	$	382,515

Depreciation and amortization expense for property, plant and equipment for the three months ended March 31, 2026 and 2025 was $5.9 million and $5.6 million, respectively. Depreciation and amortization expense for property, plant and equipment for the six months ended March 31, 2026 and 2025 was $11.9 million and $10.4 million, respectively.

Accrued Expenses

Accrued expenses consisted of the following as of:


	March 31, 2026		September 30, 2025
	(in thousands)
Accrued research and development expenses	$	32,926	$	30,330
Accrued research and development expenses; co-development	32,676		31,296
Accrued capital expenditures	334		277
Accrued income taxes	—		20,799
Dividends declared by variable interest entity to noncontrolling shareholders	2,110		—
Other	8,539		7,717
Total accrued expenses	$	76,585	$	90,419

As of March 31, 2026, the Company’s accrued research and development expenses were primarily attributable to ongoing clinical trial operations, preclinical animal studies, and associated toxicology assessments. Research and development expenses related to co-development and co-commercialization activities per the Takeda License Agreement are reported as accrued research and development expenses; co-development in the table above. (see Note 2).

Financing Agreement - Schedule of Principal Repayment Related to Credit Facility (Details) - Secured Debt - Line of Credit $ in Thousands	Mar. 31, 2026 USD ($)
Line of Credit Facility [Line Items]
2026 (remainder)	$ 25,000
2027	40,000
2028	15,000
2029	15,000
2030	15,000
Thereafter	239,114
Total	$ 349,114

Segment Information (Tables)

6 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

In addition, research and development and selling, general and administrative expenses are significant segment expenses regularly provided to the

CEO with the following categories:

Research and Development


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Candidate costs	$	99,449	$	71,191	$	204,439	$	148,087
Discovery costs	18,498		14,806		40,326		27,742
Salaries	33,546		26,907		63,585		54,052
Facilities related	7,595		6,737		15,697		14,487
Total research and development expense, excluding non-cash expense	$	159,088	$	119,641	$	324,047	$	244,368
Stock compensation	8,297		7,888		14,655		15,437
Depreciation and amortization	5,868		5,573		11,754		10,299
Total research and development expense	$	173,253	$	133,102	$	350,456	$	270,104

Selling, General & Administrative


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Salaries	$	12,435	$	7,857	$	24,375	$	15,188
Professional, outside services, and other	18,940		10,815		37,841		20,941
Facilities related	1,496		1,082		3,159		2,367
Total selling, general and administrative expense, excluding non-cash expense	$	32,871	$	19,754	$	65,375	$	38,496
Stock compensation	8,373		8,140		21,386		15,799
Depreciation/amortization	500		511		1,004		1,020
Total selling, general and administrative expense	$	41,744	$	28,405	$	87,765	$	55,315

Balance Sheet Accounts - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Depreciation and amortization expense for property and equipment	$ 5.9	$ 5.6	$ 11.9	$ 10.4

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References + Details

Fair Value Measurements - Narrative (Details) $ in Millions	Mar. 31, 2026 USD ($)
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Convertible debt, fair value	$ 722.8

- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

+ Details

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Current assets:
Cash, cash equivalents and restricted cash	$ 188,517	$ 226,548
Accounts receivable	15,685	6,824
Available-for-sale securities, at fair value and short-term investments	1,595,574	692,818
Prepaid expenses	21,721	10,933
Other current assets	18,254	13,516
Total current assets	1,839,751	950,639
Property, plant and equipment, net	374,822	382,515
Intangible assets, net	6,011	6,861
Right-of-use assets	42,794	43,891
Other assets	4,887	1,389
Total Assets	2,268,265	1,385,295
Current liabilities:
Accounts payable	30,747	17,674
Accrued expenses	76,585	90,419
Accrued payroll and benefits	20,366	26,895
Lease liabilities	7,774	7,289
Deferred revenue	108,543	2,399
Credit facility	40,000	40,000
Other liabilities	11,205	10,811
Total current liabilities	295,220	195,487
Long-term liabilities:
Lease liabilities, net of current portion	100,106	104,112
Deferred revenue, net of current portion	48,615	0
Liability related to the sale of future royalties	383,829	367,397
Credit facility, net of current portion	159,639	214,883
Convertible notes, net	681,940	0
Total long-term liabilities	1,374,129	686,392
Commitments and contingencies (Note 7)
Noncontrolling interest and stockholders’ equity:
Common stock, $0.001 par value: Authorized 290,000 shares; 143,232 shares issued and 140,571 outstanding as of March 31, 2026 and 138,363 shares issued and 135,702 outstanding as of September 30, 2025	236	231
Additional paid-in capital	2,395,267	2,139,725
Accumulated other comprehensive income	742	6,443
Accumulated deficit	(1,729,075)	(1,627,154)
Treasury stock; at cost; 2,661 shares of common stock at March 31, 2026 and September 30, 2025	(53,193)	(53,193)
Stockholders’ equity	613,977	466,052
Noncontrolling interest	(15,061)	37,364
Total noncontrolling interest and stockholders’ equity	598,916	503,416
Total Liabilities, Noncontrolling Interest and Stockholders’ Equity	2,268,265	1,385,295
Consolidated Entity Excluding Variable Interest Entities (VIE)
Current assets:
Cash, cash equivalents and restricted cash	147,531	88,706
Variable Interest Entity, Primary Beneficiary
Current assets:
Cash, cash equivalents and restricted cash	$ 40,986	$ 137,842

Leases - Schedule of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Leases [Abstract]
2026 (remainder)	$ 7,986
2027	15,050
2028	13,696
2029	13,985
2030	14,282
2031 and thereafter	100,672
Total	165,671
Less imputed interest	(57,791)
Total operating lease liabilities (includes current portion)	$ 107,880

Organization and Significant Accounting Policies	6 Months Ended
Organization and Significant Accounting Policies	Mar. 31, 2026
Accounting Policies [Abstract]
Organization and Significant Accounting Policies	ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES General and Recent Developments Arrowhead Pharmaceuticals, Inc. and its subsidiaries (referred to herein collectively as the “Company”) are primarily engaged in developing medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, the Company’s therapies trigger the RNA interference mechanism to induce rapid, deep and durable knockdown of target genes. RNA interference (“RNAi”) is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. The Company’s RNAi-based therapeutics may leverage this natural pathway of gene silencing to target and shut down specific disease-causing genes. Approved Products REDEMPLO® (plozasiran) is approved by the U.S. Food and Drug Administration (“FDA”) as an adjunct to diet to reduce triglycerides for adults with Familial Chylomicronemia Syndrome (“FCS”). REDEMPLO is also approved by the Chinese National Medical Products Administration (“NMPA”), Health Canada, and the Australian Therapeutic Goods Administration (TGA) for the same indication. REDEMPLO also received a positive Committee for Medicinal Products for Human Use (“CHMP”) opinion recommending approval to reduce triglycerides in adults with FCS in Europe. The European Commission is expected to issue a decision on REDEMPLO’s Marketing Authorization in the second calendar quarter of 2026. REDEMPLO is a small interfering RNA (“siRNA”) therapeutic designed to suppress the production of apolipoprotein C-III (APOC3), a protein produced in the liver that raises triglyceride levels by slowing their breakdown and clearance. By targeting the APOC3 gene with sustained silencing, REDEMPLO delivers significant reductions in triglyceride levels. REDEMPLO is the first and only FDA-approved siRNA treatment studied in both genetically confirmed and clinically diagnosed patients living with FCS. Consolidation and Basis of Presentation The interim Consolidated Financial Statements include the accounts of Arrowhead Pharmaceuticals, Inc. and its subsidiaries (wholly-owned subsidiaries and a variable interest entity for which the Company is the primary beneficiary). Wholly-owned subsidiaries refer to Arrowhead Madison, Inc., Arrowhead Australia Pty Ltd., Arrowhead Pharmaceuticals Ireland Limited, Arrowhead Pharmaceuticals NZ Limited. The Company’s variable interest entity is Visirna Therapeutics, Inc. (“Visirna”). For subsidiaries in which the Company owns or is exposed to less than 100% of the economics, the Company records net loss attributable to noncontrolling interests in its consolidated statements of operations equal to the percentage of the economic or ownership interests retained in such entity by the respective noncontrolling party. The interim Consolidated Financial Statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). The financial data of the Company included herein are unaudited. In the opinion of management, all material adjustments of a normal recurring nature have been made to present fairly the Company’s financial position as of March 31, 2026 and the results of operations and cash flows for the periods presented. All intercompany transactions and balances have been eliminated. Certain prior period amounts have been reclassified to conform with the current period presentation. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted from the accompanying interim consolidated financial statements and related notes. Readers are urged to review the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2025 for more complete descriptions and discussions. Operating results and cash flows for the six months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2026. The Company operates as a single segment as the chief operating decision maker (“CODM”), reviews operating results on an aggregate basis and manages the operations as a single operating segment. Refer to Note 16, Segment Information, for further details on the segment information. Liquidity The Company’s primary sources of financing have been through the sale of its equity securities, credit facility, revenue from its licensing and collaboration agreements, the sale of certain future royalties and issuance of convertible debt. Research and development activities have required significant investment since the Company’s inception and are expected to continue to require significant cash expenditure in the future, particularly as the Company’s pipeline of drug candidates and its headcount have both expanded. Additionally, significant investment will be required as a growing commercial-stage Company and as the Company’s pipeline matures into later stage clinical trials. As of March 31, 2026, the Company had $188.5 million in cash, cash equivalents and restricted cash ($1.9 million in restricted cash) and $1,595.6 million in available-for-sale securities to fund operations. In total, the Company is eligible to receive up to $15.2 billion in additional developmental, regulatory and sales milestones based on programs that have been partnered, and may receive various royalties on net sales from its licensing and collaboration agreements, subject to the terms and conditions of those agreements. Summary of Significant Accounting Policies There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K for the fiscal year ended September 30, 2025, other than below: Equity method investment The Company accounts for investments over which it has significant influence but not control under the equity method. The investment is initially recorded at cost and subsequently adjusted for the Company’s proportionate share of the investee’s net income or loss and are included in other assets in the accompanying consolidated balance sheets. The Company presents income or losses from equity investments as loss on equity method investment on the consolidated statements of operations and comprehensive (loss) income. If the share of losses exceeds the carrying value of the Company’s investment, the Company will suspend recognizing additional losses and will continue to do so unless it commits to providing additional funding or commits to guarantee investee liabilities. As of March 31, 2026, the Company had an equity method investment in Bisirna Therapeutics, Inc. (“Bisirna”). Refer to Note 8, Equity Method Investment, for further details. Convertible debt The Company accounts for its convertible debt instrument as a single unit of accounting, classified as a liability, as the conversion features do not require bifurcation as a derivative under ASC 815-15 and the convertible debt instrument was not issued at a substantial premium. The Company records debt issuance costs as contra-liabilities in the consolidated balance sheets at issuance, and amortizes them over the contractual term of the convertible debt instrument based on the effective interest method. The balance of the convertible notes presented in the consolidated balance sheets represents the principal balance of the convertible debt instrument less the unamortized portion of the debt issuance costs. As of March 31, 2026, the Company had outstanding convertible notes, which mature on January 15, 2032. Refer to Note 14, Convertible Notes, for further details. Recent Accounting Pronouncements In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Asset. This ASU allows companies to elect a practical expedient to assume that conditions as of the balance sheet date will remain unchanged for the remaining life of the asset when estimating the expected credit losses of the asset. The ASU will become effective for the Company beginning October 1, 2026, and the Company is currently evaluating the impact on its consolidated financial statements and related disclosures. In January 2025, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, in November 2024, and ASU 2025-01, Clarifying the Effective Date. These updates require entities to provide disaggregated disclosures of income statement expenses. The ASUs do not affect the expense captions presented on the face of the income statement but instead require the disaggregation of certain expense captions into specified categories within the footnotes to the financial statements. The ASUs will become effective for the Company beginning October 1, 2027, and the Company is currently evaluating the impact on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve its income tax disclosure requirements. Under the guidance, entities must annually (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. This guidance became effective for the Company beginning on October 1, 2025. The Company is currently evaluating the impact of this new ASU on its financial statements and plans to adopt ASU 2023-09 on a prospective basis during this fiscal year.

Stock-Based Compensation - Schedule of Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total	$ 16,568	$ 15,081	$ 36,158	$ 29,257
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total	8,441	7,264	14,817	14,110
Selling, general and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total	$ 8,127	$ 7,817	$ 21,341	$ 15,147

Equity Method Investment (Details) $ in Thousands		3 Months Ended		6 Months Ended
Equity Method Investment (Details) $ in Thousands	Jan. 15, 2026 shares	Mar. 31, 2026 USD ($) seat	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($) seat	Mar. 31, 2025 USD ($)
Schedule of Equity Method Investments [Line Items]
Gain on VIE's sale of IPR&D assets		$ 19,000	$ 0	$ 19,000	$ 0
Bisirna Therapeutics, Inc.
Schedule of Equity Method Investments [Line Items]
Gain on VIE's sale of IPR&D assets		$ 19,000
Voting interest		25.29%		25.29%
Number of seats on board of directors \| seat		1		1
Equity method investments		$ 4,700		$ 4,700
Bisirna Therapeutics, Inc. \| Series A Preferred Stock
Schedule of Equity Method Investments [Line Items]
Shares in exchange of IPR&D assets transferred (in shares) \| shares	6,625,000
Bisirna Therapeutics, Inc. \| Common Stock
Schedule of Equity Method Investments [Line Items]
Shares in exchange of IPR&D assets transferred (in shares) \| shares	26,500,000

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Stock-Based Compensation - Narrative (Details)			3 Months Ended		6 Months Ended
Stock-Based Compensation - Narrative (Details)	Mar. 31, 2026 USD ($) plan shares	Mar. 19, 2026 shares	Mar. 31, 2026 USD ($) plan shares	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($) plan shares	Mar. 31, 2025 USD ($) shares	Sep. 30, 2025 shares	Sep. 30, 2021 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of plans \| plan	3		3		3
Awards granted and outstanding (in shares)	6,811,828		6,811,828		6,811,828
Granted (in shares)					0	0
Common stock, share reserve for issuance (in shares)	11,354,663		11,354,663		11,354,663
Number of options outstanding (in shares)	980,034		980,034		980,034		1,407,035
Stock compensation \| $			$ 16,568,000	$ 15,081,000	$ 36,158,000	$ 29,257,000
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	5,831,794		5,831,794		5,831,794		5,810,351
Stock compensation \| $			$ 16,600,000	15,100,000	$ 36,200,000	29,200,000
Number of shares exchanged for each equity instrument	1		1		1
Unrecognized pre-tax compensation expense \| $	$ 171,500,000		$ 171,500,000		$ 171,500,000
Weighted average period to recognize pre-tax compensation expense					2 years 4 months 24 days
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised \| $			5,800,000	3,700,000	$ 18,400,000	4,600,000
Stock compensation \| $			$ 0	3,000.0	$ 0	100,000
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted and outstanding (in shares)	1,657,364		1,657,364		1,657,364
Number of shares forfeited (in shares)					170,898
Number of options outstanding (in shares)	557,364		557,364		557,364
2013 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	1,100,000		1,100,000		1,100,000
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted and outstanding (in shares)	4,053,936		4,053,936		4,053,936
Number of shares authorized (in shares)								18,500,000
Granted (in shares)					7,940,708
Number of shares forfeited (in shares)					624,473
Number of additional shares authorized (in shares)		10,500,000
Number of options outstanding (in shares)	22,965		22,965		22,965
2021 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	4,030,971		4,030,971		4,030,971
Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	832,950		832,950		832,950
Granted (in shares)					807,012
Common stock, share reserve for issuance (in shares)	25,938		25,938		25,938
Number of options outstanding (in shares)	399,705		399,705		399,705
Inducement Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	50,850		50,850		50,850
Visirna ESOP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	20,000,000		20,000,000		20,000,000
Granted (in shares)	16,400,000
Stock compensation \| $			$ 100,000	$ (100,000)	$ (100,000)	$ 1,900,000

Balance Sheet Accounts - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 466,107	$ 462,684
Less: Accumulated depreciation and amortization	(91,285)	(80,169)
Property, plant and equipment, net	374,822	382,515
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,996	2,996
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	252,932	251,317
Research equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	62,685	62,758
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	24,726	18,588
Furniture
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,594	5,594
Computers and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	970	1,064
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	104,448	104,425
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 11,756	$ 15,942

Collaboration and License Agreements - Schedule of Receivables and Contract Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025	Mar. 31, 2025
Collaboration And License Agreements [Abstract]
Receivables included in accounts receivable	$ 14,512	$ 6,824
Contract assets included in other current assets	0	0	$ 0
Contract liabilities included in deferred revenue, current	108,543	2,399	43,268
Contract liabilities included in deferred revenue, non-current	$ 48,615	$ 0	$ 0

Stockholders' Equity (Tables)

6 Months Ended

Mar. 31, 2026

Equity [Abstract]

Schedule of Shares of Common Stock and Preferred Stock

The following table summarizes the Company’s shares of common stock and preferred stock:


			Shares
	Par Value		Authorized	Issued	Outstanding
			(in thousands)
As of March 31, 2026
Common stock (1)	$	0.001	290,000	143,232	140,571
Preferred stock	$	0.001	5,000	—	—

As of September 30, 2025
Common stock (1)	$	0.001	290,000	138,363	135,702
Preferred stock	$	0.001	5,000	—	—

(1) Does not include shares of common stock into which the 2024 and 2026 Avoro Pre-Funded Warrants may be exercised.

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Liability Related to the Sale of Future Royalties - Schedule of Liability Related to the Sale of Future Royalties (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Liability, Sale Of Future Royalties [Roll Forward]
Beginning carrying value	$ 367,397	$ 341,361
Milestone payment received	0	0
Non-cash interest expense recognized	16,432	10,915
Ending carrying value	$ 383,829	$ 352,276

Intangible Assets - Schedule of Expected Future Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Goodwill and Intangible Assets Disclosure [Abstract]
2026 (remainder)	$ 850
2027	1,700
2028	1,700
2029	795
2030	149
Thereafter	817
Net Carrying Amount	$ 6,011	$ 6,861

Organization and Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2026
Accounting Policies [Abstract]
Equity method investment	Equity method investment The Company accounts for investments over which it has significant influence but not control under the equity method. The investment is initially recorded at cost and subsequently adjusted for the Company’s proportionate share of the investee’s net income or loss and are included in other assets in the accompanying consolidated balance sheets. The Company presents income or losses from equity investments as loss on equity method investment on the consolidated statements of operations and comprehensive (loss) income. If the share of losses exceeds the carrying value of the Company’s investment, the Company will suspend recognizing additional losses and will continue to do so unless it commits to providing additional funding or commits to guarantee investee liabilities. As of March 31, 2026, the Company had an equity method investment in Bisirna Therapeutics, Inc. (“Bisirna”).
Convertible debt	Convertible debt The Company accounts for its convertible debt instrument as a single unit of accounting, classified as a liability, as the conversion features do not require bifurcation as a derivative under ASC 815-15 and the convertible debt instrument was not issued at a substantial premium. The Company records debt issuance costs as contra-liabilities in the consolidated balance sheets at issuance, and amortizes them over the contractual term of the convertible debt instrument based on the effective interest method. The balance of the convertible notes presented in the consolidated balance sheets represents the principal balance of the convertible debt instrument less the unamortized portion of the debt issuance costs.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Asset. This ASU allows companies to elect a practical expedient to assume that conditions as of the balance sheet date will remain unchanged for the remaining life of the asset when estimating the expected credit losses of the asset. The ASU will become effective for the Company beginning October 1, 2026, and the Company is currently evaluating the impact on its consolidated financial statements and related disclosures. In January 2025, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, in November 2024, and ASU 2025-01, Clarifying the Effective Date. These updates require entities to provide disaggregated disclosures of income statement expenses. The ASUs do not affect the expense captions presented on the face of the income statement but instead require the disaggregation of certain expense captions into specified categories within the footnotes to the financial statements. The ASUs will become effective for the Company beginning October 1, 2027, and the Company is currently evaluating the impact on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve its income tax disclosure requirements. Under the guidance, entities must annually (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. This guidance became effective for the Company beginning on October 1, 2025. The Company is currently evaluating the impact of this new ASU on its financial statements and plans to adopt ASU 2023-09 on a prospective basis during this fiscal year.

Leases (Tables)

6 Months Ended

Mar. 31, 2026

Leases [Abstract]

Schedule of Lease Assets and Liabilities and Lease Cost

The components of lease assets and liabilities along with their classification on the Company’s consolidated balance sheets were as follows:


Lease Assets and Liabilities	Classification	March 31, 2026		September 30, 2025
		(in thousands)

Operating lease assets	Right-of-use assets	$	42,794	$	43,891
Current operating lease liabilities	Lease liabilities	7,774		7,289
Non-current operating lease liabilities	Lease liabilities, net of current portion	100,106		104,112


			Three Months Ended March 31,				Six Months Ended March 31,
Lease Cost	Classification		2026		2025		2026		2025
		(in thousands)

Operating lease cost	Research and development		$	2,789	$	2,709	$	5,518	$	5,520
	Selling, general and administrative		497		500		1,008		993

Variable lease cost (1)	Research and development		1,138		951		2,090		1,937
	Selling, general and administrative		—		—		—		—

Total			$	4,424	$	4,160	$	8,616	$	8,450

(1) Variable lease cost is primarily related to operating expenses associated with the Company’s operating leases.

Schedule of Maturities of Operating Lease Liabilities on an Undiscounted Basis

The following table presents maturities of operating lease liabilities on an undiscounted basis as of March 31, 2026:


Year	Amounts
	(in thousands)
2026 (remainder)	$	7,986
2027	15,050
2028	13,696
2029	13,985
2030	14,282
2031 and thereafter	100,672
Total	$	165,671
Less imputed interest	(57,791)
Total operating lease liabilities (includes current portion)	$	107,880

Supplemental cash flow and other information related to leases was as follows:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026			2025
	(in thousands)




Operating cash flows from operating leases	$	3,944	$	3,840	$	7,887		$	7,680
					March 31,
					2026			2025
Weighted-average remaining lease term (in years)					11.3			12.1
Weighted-average discount rate					8.0		%	8.0		%

Financing Agreement

6 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Financing Agreement

FINANCING AGREEMENT

On August 7, 2024 (the “Closing Date”), the Company entered into a Financing Agreement with the guarantors party thereto, the lenders party thereto (the “Lenders”), and Sixth Street Lending Partners (“Sixth Street”), as the administrative agent and collateral agent for the Lenders (the “Financing Agreement”). The Financing Agreement

establishes a senior secured term loan facility of $500.0 million (the “Credit Facility”), consisting of $400.0 million funded on the Closing Date and an additional $100.0 million available at the Company’s option, subject to mutual agreement with Sixth Street. The loans under the Credit Facility bear interest at an annual rate of 15.0%, which is paid in kind and added to the outstanding principal balance of the Credit Facility each period. The outstanding principal balance of this Credit Facility, including amounts representing accrued but unpaid interest previously paid in kind, is due and payable on August 7, 2031.

The Company is permitted to use the net proceeds for working capital, capital expenditures and general corporate purposes of the Company and its subsidiaries.

The Company will have the right to prepay loans under the Credit Facility at any time. The Company is required to partially repay loans under the Credit Facility with proceeds from certain asset sales, condemnation events and extraordinary receipts, subject, in some cases, to reinvestment rights. If the Company repays in full the aggregate principal outstanding under the Credit Facility and such payment in full occurs on or prior to August 7, 2028, the Company will be required to make an additional payment to the lenders under the Credit Facility on such date in an amount necessary for the lenders to achieve a two times multiple of invested capital (“MOIC”) of the aggregate principal amount funded on the Closing Date (the “MOIC Payment”). If such payment in full occurs after August 7, 2028, the Company will be required to make a payment to the lenders under the Credit Facility on such date in an amount necessary for the lenders to achieve the greater of the MOIC Payment and the present value of all interest payments that would have been payable from such date through the maturity date of the Credit Facility discounted at the Treasury Rate (as defined in the Financing Agreement) plus 0.5%; provided that such payment amount in this instance will not exceed the amount necessary for the lenders to achieve a 2.5 times MOIC.

On November 26, 2024, the Company entered into an amendment to the Financing Agreement (the "Amendment") to modify, amongst other things, some of the prepayment terms of the loans under the Credit Facility, including, the prepayment terms related to the Sarepta Collaboration Agreement. The Amendment was effective on February 14, 2025, following the closing of the Sarepta Collaboration Agreement and receipt of the $500.0 million upfront payment from Sarepta. The Amendment added an additional prepayment clause that requires certain contractual prepayments of principle and MOIC payments throughout the life of the loans under the Credit Facility. Additionally, any prepayment will be split with 50% of any such prepayment paying down the principle balance of the loans under the Credit Facility and the other 50% being applied to prepay the MOIC Payment. In the event the prepayment amounts result in fees being prepaid in excess of the actual amounts required to be paid, the excess fees shall be reallocated and applied to reduce the amount of the principal balance upon repayment in full of the loans under the Credit Facility. As of March 31, 2026, the Company has paid $142.3 million in MOIC payments of which $21.5 million is expected to be applied to principal upon repayment in full. To date, the Company has paid $286.1 million of the loans under the Credit Facility.

The Amendment was accounted for as a debt modification under ASC 470-50, “Debt—Modification and extinguishments” since the Amendment did not result in substantially different terms. In connection with the Amendment, the Company did not incur significant third-party fees.

All obligations under the Financing Agreement are secured on a first-priority basis by security interests in substantially all assets of the Company and material subsidiaries of the Company, including its intellectual property, subject to certain exceptions, and is guaranteed by material subsidiaries of the Company, including foreign subsidiaries, subject to certain exceptions.

The Financing Agreement contains customary covenants, including, without limitation, a financial covenant to maintain liquidity (cash, cash equivalents and investments) of at least $250.0 million if the Company’s market capitalization is above $2.0 billion, and negative covenants that, subject to certain exceptions, restrict indebtedness, liens, investments (including acquisitions), fundamental changes, asset sales and licensing transactions, dividends, modifications to material agreements, payment of subordinated indebtedness, distributions from certain parties, and other matters customarily restricted in such agreements. Pursuant to the terms of the Financing Agreement, the Company and its subsidiaries are not permitted to have an aggregate principal amount of convertible indebtedness outstanding at any one time in excess of the greater of $300.0 million and 10% of the market capitalization of the Company (based on the closing price of the common stock of the Company on the trading date immediately prior to the incurrence of such indebtedness), but in no event greater than $700.0 million in the aggregate. The Company is subject to restrictions on sales and licensing transactions with respect to certain core intellectual property, subject to certain exceptions, including certain transactions related to areas outside the United States, United Kingdom, European Union, Japan and China.

The Financing Agreement contains certain embedded features that were identified and evaluated as not material to the consolidated financial statements.

On August 13, 2025, the Company entered into second amendment to the Financing Agreement (the "Second

Amendment") that permitted the share repurchase of the Company's common stock from Sarepta and required the Company to pay a nominal administrative fee.

The outstanding balance of the Credit Facility consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Initial Term Loan	$	400,000	$	400,000
Accumulated interest on the Initial Term Loan	92,993		66,942
Accumulated accretion of the MOIC Payment	5,940		3,478
Less: Unamortized debt issuance costs	(13,163)		(13,912)
Less: Current portion of credit facility	(40,000)		(40,000)
Less: Payments	(286,131)		(201,625)
Credit facility, net of current portion	$	159,639	$	214,883

The following table sets forth total interest expense recognized related to the Credit Facility:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	367	$	1,129	$	748	$	1,682
Accretion of the MOIC Payment	1,178		—		2,462		—
Contractual interest expense	12,812		15,009		26,052		30,687
Total interest expense	$	14,357	$	16,138	$	29,262	$	32,369

The amounts shown in the table below, related to the Credit Facility, represent the expected repayments of principle and accrued interest balance as of March 31, 2026 inclusive of scheduled mandatory prepayments that the Company is obligated to make to the Lenders during the indicated periods. The principal balance will increase from accrued paid in kind interest, and the table does not include MOIC prepayments beyond those contractually scheduled. Actual payments on current principal may vary from the amounts presented in the table.


Year	Amounts
	(in thousands)
2026 (remainder)	$	25,000
2027	40,000
2028	15,000
2029	15,000
2030	15,000
Thereafter	239,114
Total	$	349,114

In May 2025, Visirna entered into the Revolving Credit Agreement with Bank of Zhejiang. The maximum aggregate credit facility is 72.9 million Chinese Yuan ($10.5 million) bearing an annual interest rate of 4.1%. The term of each loan is twelve months. The amount outstanding as of March 31, 2026 was 72.9 million Chinese Yuan ($10.5 million) on the credit facility which was classified as other current liabilities.

CONVERTIBLE NOTES

In January 2026, the Company issued 700.0 million aggregate principal amount of 0.00% Convertible Notes (the “Notes”) due January 15, 2032. The initial conversion rate is 11.4844 shares of common stock per $1,000 principal amount of Notes, which represents an initial conversion price of approximately $87.07 per share, subject to adjustment upon the occurrence of certain specified events. The Notes are convertible into an aggregate of approximately 8,039,080 shares of the Company’s common stock. The conversion rate is subject to adjustment, including in the case of conversions in connection with a make-whole fundamental change as defined in the indenture for the Notes or a redemption of the Notes.

The Notes are convertible at the option of the holders upon the occurrence of certain events prior to October 15, 2031, and thereafter at any time until the close of business on the second scheduled trading day immediately preceding the

maturity date. Prior to October 15, 2031, holders may convert the Notes only upon the occurrence of one of the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending March 31, 2026, if the last reported sale price of the Company’s common stock exceeds 130% of the conversion price for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading‑day period ending on, and including, the last trading day of the immediately preceding calendar quarter; (ii) during the five business days immediately following any ten consecutive trading‑day period in which the trading price per $1,000 principal amount of the Notes for each trading day of such ten consecutive trading-day period is less than 98% of the product of the last reported sale price of the Company’s common stock and the applicable conversion rate on such trading day; (iii) upon the occurrence of certain specified corporate events or distributions on the common stock; or (iv) if the Company calls the Notes for redemption. Upon conversion, the Company may, at its election, settle the Notes in cash, shares of the Company’s common stock, or a combination thereof.

The Company may not redeem the Notes prior to January 16, 2029. On or after January 16, 2029 and on or before the 30th scheduled trading day immediately preceding the maturity date, the Company may redeem for cash all or any portion of the Notes, at its option, if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading‑day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption. The redemption price will equal 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid special interest, if any, to, but excluding, the redemption date.

Upon the occurrence of a fundamental change, which includes certain change-of-control transactions, a delisting of the Company’s common stock, or a liquidation event, holders may require the Company to repurchase their Notes for cash at a price equal to 100% of the principal amount of the Notes, plus accrued and unpaid interest, if any, to, but excluding, the repurchase date.

The outstanding balance of the Notes consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Outstanding principal balance	$	700,000	$	—
Less: Unamortized debt issuance costs	(18,060)		—
Convertible Notes, Net	$	681,940	$	—

The following table sets forth total interest expense recognized related to the Notes:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	657	$	—	$	657	$	—
Total interest expense	$	657	$	—	$	657	$	—

Capped Call Transactions

In connection with the issuance of the Notes, the Company entered into privately negotiated capped call transactions (the “Capped Calls”) with certain financial institutions. The Capped Calls have an initial strike price corresponding to the initial conversion price of the Notes and an initial cap price of $119.33 per share, subject to adjustment under the terms of the Capped Call confirmations. The Capped Calls are intended to reduce or offset potential dilution to the Company’s common stock upon conversion of the Notes, with such reduction or offset subject to the applicable cap price. The Capped Calls cover, subject to anti‑dilution adjustments, the number of shares of the Company’s common stock underlying the Notes.

The Capped Calls are separate transactions that are not part of the terms of the Notes and do not affect the rights of holders of the Notes. The Company paid $47.9 million in connection with the Capped Call transactions, which was recorded as a reduction to additional paid‑in capital in the consolidated balance sheets. As the Capped Calls meet the applicable equity classification criteria under ASC 815, Derivatives and Hedging, they are recorded within stockholders’ equity and are not subsequently remeasured to fair value.

Insider Trading Arrangements

3 Months Ended

Mar. 31, 2026

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

During the quarter ended March 31, 2026, the following directors and officers (as defined in Exchange Act Rule 16a-1(f)) adopted certain trading plans intended to satisfy Rule 10b5-1(c):

Name

Title

Adoption or Termination Date

Plan End Date

Shares Vesting and Subject to Sell-To-Cover (1)

Other Shares Being Sold (Subject to Certain Conditions)

Victoria Vakiener

Board Member

01/12/2026

12/31/2026

4,300

Adeoye Olukotun

Board Member

01/14/2026

12/31/2026

7,819

Hongbo Lu

Board Member

01/14/2026

12/31/2026

7,449

William Waddill

Board Member

02/25/2026

12/31/2026

3,910

Daniel Apel

Chief Financial Officer

03/29/2026

04/27/2027

43,750

(1) This column indicates the total number of shares vesting, but the 10b5-1 Plan provides for the sale of only those shares necessary to satisfy payment of applicable withholding taxes.

Non-Rule 10b5-1 Arrangement Adopted

false

Rule 10b5-1 Arrangement Terminated

false

Non-Rule 10b5-1 Arrangement Terminated

false

Victoria Vakiener [Member]

Trading Arrangements, by Individual

Name

Victoria Vakiener

Title

Board Member

Rule 10b5-1 Arrangement Adopted

true

01/12/2026

12/31/2026

353 days

4,300

Adeoye Olukotun [Member]

Trading Arrangements, by Individual

Name

Adeoye Olukotun

Title

Board Member

Rule 10b5-1 Arrangement Adopted

true

01/14/2026

12/31/2026

351 days

7,819

Trading Arrangements, by Individual

Name

Hongbo Lu

Title

Board Member

Rule 10b5-1 Arrangement Adopted

true

01/14/2026

12/31/2026

351 days

7,449

William Waddill [Member]

Trading Arrangements, by Individual

Name

William Waddill

Title

Board Member

Rule 10b5-1 Arrangement Adopted

true

02/25/2026

12/31/2026

309 days

3,910

Trading Arrangements, by Individual

Name

Daniel Apel

Title

Chief Financial Officer

Rule 10b5-1 Arrangement Adopted

true

03/29/2026

04/27/2027

394 days

43,750

Investments (Tables)

6 Months Ended

Mar. 31, 2026

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

The Company’s investments consisted of the following:


	As of March 31, 2026
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	1,598,704	$	1,091	$	(4,943)	$	1,594,852

Short‑term investments	722		—		—		722
Total current investments	$	1,599,426	$	1,091	$	(4,943)	$	1,595,574


	As of September 30, 2025
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	689,882	$	2,956	$	(20)	$	692,818

Total current investments	$	689,882	$	2,956	$	(20)	$	692,818

Schedule of Contract Maturity of Available for Sale Securities

The following table summarizes the contract maturity of the available-for-sale securities and short-term investments as of:


	March 31, 2026		September 30, 2025
	(in thousands)


Within one year	$	579,223	$	224,328
After one to two years	566,425		468,490
After two to three years	449,926		—
Total	$	1,595,574	$	692,818

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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+ Details

Net (Loss) Income Per Share - Schedule of Computation of Basic and Diluted Net (Loss) Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Numerator:
Net (loss) income attributable to Arrowhead Pharmaceuticals, Inc.	$ (132,732)	$ 370,445	$ (101,919)	$ 197,360
Denominator:
Weighted-average basic shares outstanding (in shares)	142,417	133,363	139,762	129,059
Effect of dilutive securities (in shares)	0	1,121	0	1,206
Weighted-average diluted shares outstanding (in shares)	142,417	134,484	139,762	130,265
Basic net (loss) income per share (in dollars per share)	$ (0.93)	$ 2.78	$ (0.73)	$ 1.53
Diluted net (loss) income per share (in dollars per share)	$ (0.93)	$ 2.75	$ (0.73)	$ 1.52

- Definition

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+ Details

Intangible Assets

6 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

INTANGIBLE ASSETS

Intangible assets subject to amortization include patents and a license agreement capitalized as part of the Novartis RNAi asset acquisition in March 2015. The following table presents the components of intangible assets:


	Gross Carrying Amount		Accumulated Amortization		Impairment		Net Carrying Amount		Useful Lives
	(in thousands)								(in years)
As of March 31, 2026
Patents	$	21,728	$	17,201	$	—	$	4,527	14
License	3,129		1,645		—		1,484		21
Total intangible assets, net	$	24,857	$	18,846	$	—	$	6,011

As of September 30, 2025
Patents	$	21,728	$	16,426	$	—	$	5,302	14
License	3,129		1,570		—		1,559		21
Total intangible assets, net	$	24,857	$	17,996	$	—	$	6,861

Intangible assets are reviewed annually for impairment and more frequently if potential impairment indicators exist. No impairment indicators were identified during the six months ended March 31, 2026 and 2025.

Intangible assets with definite useful lives are amortized on a straight-line basis over their useful lives. Intangible assets amortization expense was $0.4 million for the three months ended March 31, 2026 and 2025, and $0.9 million for each of the six months ended March 31, 2026 and 2025. None of the intangible assets with definite useful lives are anticipated to have a residual value.

The following table presents the estimated future amortization expense related to intangible assets as of March 31, 2026:


	Amortization Expense
Year Ending September 30,	(in thousands)
2026 (remainder)	$	850
2027	1,700
2028	1,700
2029	795
2030	149
Thereafter	817
Total	$	6,011

Fair Value Measurements (Tables)

6 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Schedule of Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s assets and liabilities measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques utilized by the Company:


	March 31, 2026
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities

U.S. government and agency securities	$	—	$	256,086	$	—	$	256,086
Municipal securities	—		5,999		—		5,999
Commercial notes	—		143,970		—		143,970
Corporate debt securities	—		1,188,797		—		1,188,797
Total available-for-sale securities	—		1,594,852		—		1,594,852
Short‑term investments
Term deposits	—		722		—		722
Total Short‑term investments	—		722		—		722
Cash equivalents
Money market instruments	113,828		—		—		113,828
Term deposit	—		16,950		—		16,950
Commercial notes	—		30,246		—		30,246
Total cash equivalents	113,828		47,196		—		161,024
Total financial assets	$	113,828	$	1,642,770	$	—	$	1,756,598


	September 30, 2025
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	150,695	$	—	$	150,695
Certificate of deposits	—		12,019		—		12,019
Municipal securities	—		7,046		—		7,046
Commercial notes	—		13,801		—		13,801
Corporate debt securities	—		509,257		—		509,257
Total available-for-sale securities	—		692,818		—		692,818
Cash equivalents
Money market instruments	64,460		—		—		64,460
Term deposit	—		134,357		—		134,357
Certificate of deposits	—		3,001		—		3,001
Corporate debt securities	—		16,182		—		16,182
Total cash equivalents	64,460		153,540		—		218,000
Total financial assets	$	64,460	$	846,358	$	—	$	910,818

Segment Information

6 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Segment Information

SEGMENT INFORMATION

We operate in a single segment dedicated to the discovery, development, manufacturing and commercialization of RNAi therapeutics. The Company's RNAi therapeutics are comprised of siRNAs that function upstream of conventional medicines by potently silencing mRNA that encode for proteins implicated in the cause or pathway of disease, thus preventing them from being made. Consistent with our operational structure, our Chief Executive Officer (“CEO”), as the CODM, manages and allocates resources on a consolidated basis at the global corporate level. Our global research and development and technical operations and quality organizations are responsible for the discovery, development, and supply of products. Commercial efforts that coordinate the marketing, sales and distribution of these products are organized by geographic region. All of these activities are supported by corporate staff functions. Managing and allocating resources at the corporate level enables our CEO to assess the overall level of resources available and how to best deploy these resources in line with our overarching long-term, corporate-wide strategic goals. The determination of a single segment is consistent with the consolidated financial information regularly reviewed by the CODM for the purposes of evaluating performance, forecasting future period financial results, allocating resources and setting incentive targets.

Consistent with our management reporting, results of our operations are reported on a consolidated basis for purposes of segment reporting. The CEO evaluates performance and decides how to allocate resources based on consolidated net (loss) income that is reported on the consolidated statements of operations and comprehensive (loss) income. The measure of segment assets is reported on the consolidated balance sheets as total assets. The CEO uses consolidated net (loss) income to evaluate loss or income generated from the Company’s business activities in deciding how to allocate company resources (such as pursuing clinical development or entering a strategic collaboration), monitoring budget versus actual results, and establishing management’s compensation. Please refer to the consolidated financial statements for further information related to these measures of segment performance. In addition, research and development and selling, general and administrative expenses are significant segment expenses regularly provided to the

CEO with the following categories:

Research and Development


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Candidate costs	$	99,449	$	71,191	$	204,439	$	148,087
Discovery costs	18,498		14,806		40,326		27,742
Salaries	33,546		26,907		63,585		54,052
Facilities related	7,595		6,737		15,697		14,487
Total research and development expense, excluding non-cash expense	$	159,088	$	119,641	$	324,047	$	244,368
Stock compensation	8,297		7,888		14,655		15,437
Depreciation and amortization	5,868		5,573		11,754		10,299
Total research and development expense	$	173,253	$	133,102	$	350,456	$	270,104

Selling, General & Administrative


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Salaries	$	12,435	$	7,857	$	24,375	$	15,188
Professional, outside services, and other	18,940		10,815		37,841		20,941
Facilities related	1,496		1,082		3,159		2,367
Total selling, general and administrative expense, excluding non-cash expense	$	32,871	$	19,754	$	65,375	$	38,496
Stock compensation	8,373		8,140		21,386		15,799
Depreciation/amortization	500		511		1,004		1,020
Total selling, general and administrative expense	$	41,744	$	28,405	$	87,765	$	55,315

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

+ Details

Stock-Based Compensation - Schedule of Awards Outstanding (Details) - shares	Mar. 31, 2026	Sep. 30, 2025
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options (in shares)	980,034	1,407,035
Total (in shares)	6,811,828
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units (in shares)	5,831,794	5,810,351
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options (in shares)	557,364
Total (in shares)	1,657,364
2013 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units (in shares)	1,100,000
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options (in shares)	22,965
Total (in shares)	4,053,936
2021 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units (in shares)	4,030,971
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options (in shares)	399,705
Total (in shares)	1,100,528
Inducement Awards \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units (in shares)	700,823

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Fair Value Measurements

6 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

The Company employs a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The Company’s valuation techniques and inputs used to measure fair value and the definition of the three levels (Level 1, Level 2, and Level 3) of the fair value hierarchy are disclosed in Note 10 - Fair Value Measurements of Notes to Consolidated Financial Statements of Part IV, “Item 15. Exhibits and Financial Statement Schedules” of its Annual Report on Form 10-K for the fiscal year ended September 30, 2025.

The Company uses prices and inputs that are current as of the measurement date, including during periods of market disruption. In periods of market disruption, the ability to observe prices and inputs may be reduced for many instruments. This condition could cause an instrument to be reclassified from Level 1 to Level 2, or from Level 2 to Level 3. The Company recognizes transfers between levels at either the actual date of the event or a change in circumstances that caused the transfer. As of March 31, 2026 and September 30, 2025, the Company did not have any financial assets or financial liabilities based on Level 3 measurements.


	March 31, 2026
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities

U.S. government and agency securities	$	—	$	256,086	$	—	$	256,086
Municipal securities	—		5,999		—		5,999
Commercial notes	—		143,970		—		143,970
Corporate debt securities	—		1,188,797		—		1,188,797
Total available-for-sale securities	—		1,594,852		—		1,594,852
Short‑term investments
Term deposits	—		722		—		722
Total Short‑term investments	—		722		—		722
Cash equivalents
Money market instruments	113,828		—		—		113,828
Term deposit	—		16,950		—		16,950
Commercial notes	—		30,246		—		30,246
Total cash equivalents	113,828		47,196		—		161,024
Total financial assets	$	113,828	$	1,642,770	$	—	$	1,756,598


	September 30, 2025
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	150,695	$	—	$	150,695
Certificate of deposits	—		12,019		—		12,019
Municipal securities	—		7,046		—		7,046
Commercial notes	—		13,801		—		13,801
Corporate debt securities	—		509,257		—		509,257
Total available-for-sale securities	—		692,818		—		692,818
Cash equivalents
Money market instruments	64,460		—		—		64,460
Term deposit	—		134,357		—		134,357
Certificate of deposits	—		3,001		—		3,001
Corporate debt securities	—		16,182		—		16,182
Total cash equivalents	64,460		153,540		—		218,000
Total financial assets	$	64,460	$	846,358	$	—	$	910,818

Convertible Notes

Our Convertible Notes (see Note 14) had a fair value of $722.8 million at March 31, 2026. We determine the fair value of the Convertible Notes based on quoted market prices for these notes, which are Level 2 measurements because the

Convertible Notes do not trade regularly.

Credit Facility

The fair value of the Company’s outstanding credit facility (see Note 13) was estimated using the net present value of the expected contractual payments, discounted at an interest rate consistent with a market interest rate, which represents a Level 2 input. As of March 31, 2026, the estimated fair value of our credit facility approximated its carrying amount.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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-Section 50
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+ Details

Fair Value Measurements - Schedule of Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 1,594,852	$ 692,818
Short‑term investments	722
Cash equivalents	161,024	218,000
Total financial assets	1,756,598	910,818
Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	113,828	64,460
Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	16,950	134,357
Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	30,246
Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		3,001
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		16,182
U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	256,086	150,695
Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities		12,019
Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	5,999	7,046
Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	143,970	13,801
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	1,188,797	509,257
Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short‑term investments	722
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Short‑term investments	0
Cash equivalents	113,828	64,460
Total financial assets	113,828	64,460
Level 1 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	113,828	64,460
Level 1 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 1 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 1 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Level 1 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Level 1 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 1 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities		0
Level 1 \| Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 1 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 1 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 1 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short‑term investments	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	1,594,852	692,818
Short‑term investments	722
Cash equivalents	47,196	153,540
Total financial assets	1,642,770	846,358
Level 2 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 2 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	16,950	134,357
Level 2 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	30,246
Level 2 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		3,001
Level 2 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		16,182
Level 2 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	256,086	150,695
Level 2 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities		12,019
Level 2 \| Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	5,999	7,046
Level 2 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	143,970	13,801
Level 2 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	1,188,797	509,257
Level 2 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short‑term investments	722
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Short‑term investments	0
Cash equivalents	0	0
Total financial assets	0	0
Level 3 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 3 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Level 3 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Level 3 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 3 \| Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities		0
Level 3 \| Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 3 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Level 3 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	$ 0
Level 3 \| Term deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short‑term investments	$ 0

Financing Agreement (Tables)

6 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Schedule of Outstanding Balance of Credit Facility

The outstanding balance of the Credit Facility consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Initial Term Loan	$	400,000	$	400,000
Accumulated interest on the Initial Term Loan	92,993		66,942
Accumulated accretion of the MOIC Payment	5,940		3,478
Less: Unamortized debt issuance costs	(13,163)		(13,912)
Less: Current portion of credit facility	(40,000)		(40,000)
Less: Payments	(286,131)		(201,625)
Credit facility, net of current portion	$	159,639	$	214,883

Schedule of Total Interest Expense Recognized

The following table sets forth total interest expense recognized related to the Credit Facility:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	367	$	1,129	$	748	$	1,682
Accretion of the MOIC Payment	1,178		—		2,462		—
Contractual interest expense	12,812		15,009		26,052		30,687
Total interest expense	$	14,357	$	16,138	$	29,262	$	32,369

Schedule of Principal Repayment Related to Credit Facility


Year	Amounts
	(in thousands)
2026 (remainder)	$	25,000
2027	40,000
2028	15,000
2029	15,000
2030	15,000
Thereafter	239,114
Total	$	349,114

Leases - Schedule of Lease Assets and Liabilities and Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Lease Assets and Liabilities
Operating lease assets	$ 42,794		$ 42,794		$ 43,891
Current operating lease liabilities	7,774		7,774		7,289
Non-current operating lease liabilities	100,106		100,106		$ 104,112
Lease Cost
Total	4,424	$ 4,160	8,616	$ 8,450
Research and development
Lease Cost
Operating lease cost	2,789	2,709	5,518	5,520
Variable lease cost	1,138	951	2,090	1,937
Selling, general and administrative
Lease Cost
Operating lease cost	497	500	1,008	993
Variable lease cost	$ 0	$ 0	$ 0	$ 0

Leases - Schedule of Cash Flow and Other Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Leases [Abstract]
Operating cash flows from operating leases	$ 3,944	$ 3,840	$ 7,887	$ 7,680
Weighted-average remaining lease term (in years)	11 years 3 months 18 days	12 years 1 month 6 days	11 years 3 months 18 days	12 years 1 month 6 days
Weighted-average discount rate	8.00%	8.00%	8.00%	8.00%

Balance Sheet Accounts - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued research and development expenses	$ 32,926	$ 30,330
Accrued research and development expenses; co-development	32,676	31,296
Accrued capital expenditures	334	277
Accrued income taxes	0	20,799
Dividends declared by variable interest entity to noncontrolling shareholders	2,110	0
Other	8,539	7,717
Total accrued expenses	$ 76,585	$ 90,419

Collaboration and License Agreements - Visirna Therapeutics Inc. (“Visirna”) and Genzyme Corporation (“Sanofi”) (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 01, 2025	Jan. 31, 2026	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue			$ 73,737	$ 542,709	$ 337,770	$ 545,209
Accounts receivable			15,685		15,685		$ 6,824
Sanofi \| Sanofi License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 130,000
Future potential milestone payments	265,000
Fixed consideration	$ 130,000
Triggered milestone payments		$ 10,000
Revenue			10,500
Accounts receivable			$ 500		$ 500

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 8: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479941/924-10-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-4

+ Details

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Common Stock in Treasury	Non- controlling Interest
Common stock, beginning balance (in shares) at Sep. 30, 2024		124,376,000
Beginning balance at Sep. 30, 2024	$ 191,063	$ 217	$ 1,806,000	$ 4,750	$ (1,625,523)		$ 5,619
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	15,209		15,209
Exercise of stock options (in shares)		70,000
Exercise of stock options	634		634
Common stock - restricted stock units vesting (in shares)		209,000
Issuance of pre-funded warrants	25,000		25,000
Foreign currency translation adjustments	(106)			(106)
Unrealized gains (losses) on available-for-sale securities, net	(507)			(507)
Net income (loss)	(175,218)				(173,085)		(2,133)
Common stock, ending balance (in shares) at Dec. 31, 2024		124,655,000
Ending balance at Dec. 31, 2024	56,075	$ 217	1,846,843	4,137	(1,798,608)		3,486
Common stock, beginning balance (in shares) at Sep. 30, 2024		124,376,000
Beginning balance at Sep. 30, 2024	191,063	$ 217	1,806,000	4,750	(1,625,523)		5,619
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	(506)
Unrealized gains (losses) on available-for-sale securities, net	146
Net income (loss)	192,645
Common stock, ending balance (in shares) at Mar. 31, 2025		138,062,000
Ending balance at Mar. 31, 2025	684,225	$ 230	2,106,864	4,390	(1,428,163)		904
Common stock, beginning balance (in shares) at Dec. 31, 2024		124,655,000
Beginning balance at Dec. 31, 2024	56,075	$ 217	1,846,843	4,137	(1,798,608)		3,486
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	16,027		16,027
Exercise of stock options (in shares)		353,000
Exercise of stock options	2,619		2,619
Common stock - restricted stock units vesting (in shares)		1,128,000
Common stock - restricted stock units vesting	1	$ 1
Common stock issued (in shares)		11,926,000
Common stock issued	241,387	$ 12	241,375
Foreign currency translation adjustments	(400)			(400)
Unrealized gains (losses) on available-for-sale securities, net	653			653
Net income (loss)	367,863				370,445		(2,582)
Common stock, ending balance (in shares) at Mar. 31, 2025		138,062,000
Ending balance at Mar. 31, 2025	$ 684,225	$ 230	2,106,864	4,390	(1,428,163)		904
Common stock, beginning balance (in shares) at Sep. 30, 2025	135,702,000	138,363,000
Beginning balance at Sep. 30, 2025	$ 503,416	$ 231	2,139,725	6,443	(1,627,154)	$ (53,193)	37,364
Treasury stock, beginning balance (in shares) at Sep. 30, 2025	(2,661,000)					(2,661,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 19,371		19,371
Exercise of stock options (in shares)		296,000
Exercise of stock options	5,098		5,098
Common stock - restricted stock units vesting (in shares)		704,000
Common stock - restricted stock units vesting	2	$ 1	1
Common stock issued (in shares)		689,000
Common stock issued	46,832	$ 1	46,831
Foreign currency translation adjustments	110			110
Unrealized gains (losses) on available-for-sale securities, net	146			146
Dividends declared by variable interest entity to noncontrolling shareholders	(40,520)						(40,520)
Net income (loss)	28,242				30,811		(2,569)
Common stock, ending balance (in shares) at Dec. 31, 2025		140,052,000
Ending balance at Dec. 31, 2025	$ 562,697	$ 233	2,211,026	6,699	(1,596,343)	$ (53,193)	(5,725)
Treasury stock, ending balance (in shares) at Dec. 31, 2025						(2,661,000)
Common stock, beginning balance (in shares) at Sep. 30, 2025	135,702,000	138,363,000
Beginning balance at Sep. 30, 2025	$ 503,416	$ 231	2,139,725	6,443	(1,627,154)	$ (53,193)	37,364
Treasury stock, beginning balance (in shares) at Sep. 30, 2025	(2,661,000)					(2,661,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	427,001
Purchase of Capped Calls related to the 2026 Convertible Note			(47,880)
Foreign currency translation adjustments	$ 1,100
Unrealized gains (losses) on available-for-sale securities, net	(6,788)
Net income (loss)	$ (109,328)
Common stock, ending balance (in shares) at Mar. 31, 2026	140,571,000	143,232,000
Ending balance at Mar. 31, 2026	$ 598,916	$ 236	2,395,267	742	(1,729,075)	$ (53,193)	(15,061)
Treasury stock, ending balance (in shares) at Mar. 31, 2026	(2,661,000)					(2,661,000)
Common stock, beginning balance (in shares) at Dec. 31, 2025		140,052,000
Beginning balance at Dec. 31, 2025	$ 562,697	$ 233	2,211,026	6,699	(1,596,343)	$ (53,193)	(5,725)
Treasury stock, beginning balance (in shares) at Dec. 31, 2025						(2,661,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	16,670		16,670
Exercise of stock options (in shares)		121,000
Exercise of stock options	1,968		1,968
Common stock - restricted stock units vesting (in shares)		1,043,000
Common stock - restricted stock units vesting	1	$ 1
Common stock issued (in shares)		2,016,000
Common stock issued	116,607	$ 2	116,605
Issuance of pre-funded warrants	99,998		99,998
Purchase of Capped Calls related to the 2026 Convertible Note	(47,880)
Foreign currency translation adjustments	990			990
Unrealized gains (losses) on available-for-sale securities, net	(6,934)			(6,934)
Change in ownership interest in consolidated VIE	0		(3,120)	(13)			3,133
Gain on VIE's sale of IPR&D assets	(7,629)						(7,629)
Net income (loss)	$ (137,572)				(132,732)		(4,840)
Common stock, ending balance (in shares) at Mar. 31, 2026	140,571,000	143,232,000
Ending balance at Mar. 31, 2026	$ 598,916	$ 236	$ 2,395,267	$ 742	$ (1,729,075)	$ (53,193)	$ (15,061)
Treasury stock, ending balance (in shares) at Mar. 31, 2026	(2,661,000)					(2,661,000)

Net (Loss) Income Per Share

6 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Net (Loss) Income Per Share

NET (LOSS) INCOME PER SHARE

The following table presents the computation of basic and diluted net (loss) income per share for the three and six months ended March 31, 2026 and 2025.


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands, except per share amounts)
Numerator:
Net (loss) income attributable to Arrowhead Pharmaceuticals, Inc.	$	(132,732)	$	370,445	$	(101,919)	$	197,360

Denominator:
Weighted-average basic shares outstanding (1)	142,417		133,363		139,762		129,059
Effect of dilutive securities	—		1,121		—		1,206
Weighted-average diluted shares outstanding (1)	142,417		134,484		139,762		130,265

Basic net (loss) income per share	$	(0.93)	$	2.78	$	(0.73)	$	1.53
Diluted net (loss) income per share	$	(0.93)	$	2.75	$	(0.73)	$	1.52

(1) Include shares of common stock into which the 2024 and 2026 Avoro Pre-Funded Warrants may be exercised. See Note 6.

The following table sets forth the weight-average number of potentially dilutive securities that have been excluded from the calculation of diluted net (loss) income per share because to include them would be anti-dilutive.


	Three Months Ended March 31,		Six Months Ended March 31,
	2026	2025	2026	2025
	(in thousands)
Options	1,022	760	1,160	750
Restricted stock units	5,605	5,289	5,389	4,567
If-converted common stock from convertible notes	7,057	—	3,489	—
Total	13,684	6,049	10,038	5,317

Financing Agreement - Schedule of Total Interest Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Line of Credit Facility [Line Items]
Amortization of debt issuance costs			$ 657	$ 0
Secured Debt \| Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Amortization of debt issuance costs	$ 367	$ 1,129	748	1,682
Accretion of the MOIC Payment	1,178	0	2,462	0
Contractual interest expense	12,812	15,009	26,052	30,687
Total interest expense	$ 14,357	$ 16,138	$ 29,262	$ 32,369

Investments - Schedule of Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities, Adjusted Basis	$ 1,598,704	$ 689,882
Available-for-sale securities, Gross Unrealized Gains	1,091	2,956
Available-for-sale securities, Gross Unrealized Losses	(4,943)	(20)
Available-for-sale securities, Fair Value	1,594,852	692,818
Short-term investments, Amortized Cost	722
Short-term investments, Fair Value	722
Total current Investments, Amortized Cost	1,599,426	689,882
Total current Investments, Fair Value	$ 1,595,574	$ 692,818

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (109,328)	$ 192,645
Adjustments to reconcile net (loss) income to net cash flow from operating activities
Stock-based compensation	36,041	31,236
Depreciation and amortization	12,758	11,319
Accretion of available-for-sale securities premiums/discounts	(2,515)	(2,788)
Amortization of convertible notes issuance costs	657	0
Realized gain on investments	(19)	0
Non-cash interest expense on liability related to the sale of future royalties	16,432	10,915
Non-cash interest expense on credit facility	29,262	32,369
Loss on equity method investment	6,719	0
Gain on VIE's sale of IPR&D assets	(19,000)	0
Non-cash transfer of property and equipment to affiliate	555	0
Changes in operating assets and liabilities:
Accounts receivable	(8,861)	(2,365)
Prepaid expenses and other current assets	(8,413)	(20,936)
Accounts payable	13,073	(1,717)
Accrued expenses	(22,136)	18,921
Deferred revenue	154,760	43,268
Operating lease, net	(2,423)	(2,255)
Other	361	3,169
Net cash provided by operating activities	97,923	313,781
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(4,713)	(12,813)
Purchases of available-for-sale securities	(1,061,577)	(677,892)
Proceeds from sales of available-for-sale securities	23,748	0
Proceeds from maturities of available-for-sale securities	124,518	347,402
Net cash used in investing activities	(918,024)	(343,303)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercises of stock options	10,146	3,253
Proceeds from issuance of warrants	99,998	25,000
Proceeds from issuance of convertible notes	700,000	0
Payments of debt issuance costs	(18,716)	(5,000)
Purchase of capped calls	(47,880)	0
Repayments of credit facility	(84,506)	(151,625)
Dividends paid by variable interest entity to noncontrolling shareholders	(41,514)	0
Net cash provided by financing activities	780,967	113,016
Net (decrease) increase in cash, cash equivalents and restricted cash	(39,134)	83,494
Effect of exchange rate on cash, cash equivalents and restricted cash	1,103	(470)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
BEGINNING OF PERIOD	226,548	102,685
END OF PERIOD	188,517	185,709
Supplemental disclosure of cash flows:
Interest paid	0	(19)
Income taxes paid	(21,565)	(81)
Supplemental disclosure of non-cash investing activities:
Capital expenditures included in accrued expenses	334	358
ATM Agreement
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	48,156	241,388
Payments of issuance costs of common stock	(1,324)	0
Underwriting Public Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	130,000	0
Payments of issuance costs of common stock	$ (13,393)	$ 0

Balance Sheet Accounts (Tables)

6 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Property, Plant and Equipment

The following table summarizes the Company’s major classes of property, plant and equipment:


	March 31, 2026		September 30, 2025
	(in thousands)
Land	$	2,996	$	2,996
Buildings	252,932		251,317
Research equipment	62,685		62,758
Manufacturing equipment	24,726		18,588
Furniture	5,594		5,594
Computers and software	970		1,064
Leasehold improvements	104,448		104,425
Construction in progress	11,756		15,942
	466,107		462,684
Less: Accumulated depreciation and amortization	(91,285)		(80,169)
Property, plant and equipment, net	$	374,822	$	382,515

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of:


	March 31, 2026		September 30, 2025
	(in thousands)
Accrued research and development expenses	$	32,926	$	30,330
Accrued research and development expenses; co-development	32,676		31,296
Accrued capital expenditures	334		277
Accrued income taxes	—		20,799
Dividends declared by variable interest entity to noncontrolling shareholders	2,110		—
Other	8,539		7,717
Total accrued expenses	$	76,585	$	90,419

Stock-Based Compensation - Schedule of Stock Option Activity (Details) - USD ($)	6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Shares
Beginning balance (in shares)	1,407,035
Granted (in shares)	0	0
Cancelled or expired (in shares)	0
Exercised (in shares)	(427,001)
Ending balance (in shares)	980,034
Number of options outstanding, exercisable (in shares)	980,034
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share)	$ 28.90
Granted (in dollars per share)	0
Cancelled or expired (in dollars per share)	0
Exercised (in dollars per share)	17.26
Ending balance (in dollars per share)	33.83
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share)	$ 33.83
Weighted- Average Remaining Contractual Term (Years)	3 years 3 months 18 days
Weighted-Average Remaining Contractual Term, Exercisable	3 years 3 months 18 days
Aggregate Intrinsic Value	$ 29,108,721
Aggregate Intrinsic Value, Exercisable	$ 29,108,721

Convertible Notes - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jan. 31, 2026 USD ($) shares day $ / shares	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)
Debt Instrument [Line Items]
Payments for capped call \| $		$ 47,880	$ 0
Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Aggregate principal amount \| $	$ 700,000
Interest rate	0.00%
Conversion ratio	0.0114844
Conversion price (in dollars per share) \| $ / shares	$ 87.07
Convertible, number of equity instruments (in shares) \| shares	8,039,080
Days preceding maturing date	30
Redemption price, percentage	100.00%
Initial cap price (in dollars per share) \| $ / shares	$ 119.33
Payments for capped call \| $	$ 47,900
Convertible Notes \| Convertible Debt \| Debt Conversion Terms One
Debt Instrument [Line Items]
Threshold percentage of stock price trigger	130.00%
Threshold trading days	20
Threshold consecutive trading days	30
Convertible Notes \| Convertible Debt \| Debt Conversion Terms Two
Debt Instrument [Line Items]
Threshold trading days	5
Threshold consecutive trading days	10
Threshold percentage of stock trading price	98.00%

Collaboration and License Agreements - GlaxoSmithKline Intellectual Property (No. 3) Limited (Details) - USD ($)		1 Months Ended	3 Months Ended
	Nov. 22, 2021	Dec. 31, 2023	Mar. 31, 2025	Mar. 31, 2026	Sep. 30, 2025	Dec. 11, 2023	Jun. 30, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract assets			$ 0	$ 0	$ 0
Contract liabilities included in deferred revenue, current			43,268,000	108,543,000	$ 2,399,000
GSK \| GSK-HSD License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 120,000,000.0
Milestone payment receivable							$ 30,000,000.0
Milestone payment receivable upon achievement of phase two and first patient dosed in phase three	100,000,000.0
Contract assets				0
Contract liabilities included in deferred revenue, current				0
GSK \| GSK-HSD License Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Commercial milestone payments at first commercial sale	190,000,000.0
Sales-related milestone payments	$ 590,000,000.0
Percentage of eligible to receive tiered royalties on net sales	20.00%
GSK \| GSK-HBV Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price		$ 2,700,000
Development milestone payments			$ 2,500,000
Contract assets				0
Contract liabilities included in deferred revenue, current				$ 0
GSK \| GSK-HBV Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development and sales milestone payments						$ 830,000,000.0

Cover - shares	6 Months Ended
Cover - shares	Mar. 31, 2026	May 01, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
Document Transition Report	false
Entity File Number	001-38042
Entity Registrant Name	ARROWHEAD PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-0408024
Entity Address, Address Line One	177 E. Colorado Blvd
Entity Address, Address Line Two	Suite 700
Entity Address, City or Town	Pasadena
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91105
City Area Code	626
Local Phone Number	304-3400
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ARWR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		140,857,021
Entity Central Index Key	0000879407
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Amendment Flag	false

Liability Related to the Sale of Future Royalties - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2022	Jun. 30, 2024	Dec. 31, 2023	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Sep. 30, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment received				$ 0	$ 0
Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received			$ 250,000
Milestone payment receivable	$ 160,000
Milestone payment receivable upon achievement of enrollment in phase 3 clinical trial						$ 50,000
Milestone payment receivable upon FDA approval	50,000
Milestone payment receivable upon receipt of royalty payments	60,000
Royalty payment threshold	70,000
Milestone payment received		$ 50,000
Future potential milestone payments payable				$ 110,000
Liability related to the sale of future royalties, interest rate				9.40%			8.30%
Maximum \| Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 410,000

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Litigation From time to time, the Company may be subject to various claims and legal proceedings in the ordinary course of business. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount is reasonably estimable, the Company will accrue a liability for the estimated loss. There were no contingent liabilities recorded as of March 31, 2026. On September 10, 2025, the Company filed a Complaint for Declaratory Judgment in the United States District Court for the District of Delaware against Ionis Pharmaceuticals, Inc. (“Ionis”) to declare that United States Patent No. 9,593,333 (“the ’333 patent”) is invalid and not infringed by the Company’s planned commercialization of investigational plozasiran (the “Delaware DJ action”). On December 23, 2025, the court granted Ionis’s motion to dismiss the Delaware DJ action. On September 11, 2025, Ionis filed a Complaint for Patent Infringement against the Company in the United States District Court for the Central District of California alleging patent infringement of the ’333 patent by the Company’s planned commercialization of investigational plozasiran and seeking damages. The Company disputes the allegations of wrongdoing and intends to vigorously defend itself. Commitments As of March 31, 2026, the Company did not have any material commitments.

Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 0.4	$ 0.4	$ 0.9	$ 0.9

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-18

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
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-Name Accounting Standards Codification
-Section 55
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-11

Reference 4: http://www.xbrl.org/2003/role/exampleRef
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-URI https://asc.fasb.org/1943274/2147476153/220-40-55-24

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
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-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-12

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 40
-SubTopic 30
-Topic 350
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482640/350-30-55-40

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
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-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482686/350-30-45-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-6

+ Details

Stock-Based Compensation - Schedule of Share Activity Related to RSUs (Details) - Restricted stock units	6 Months Ended
	Mar. 31, 2026 $ / shares shares
Number of RSUs
Beginning of period (in shares) \| shares	5,810,351
Granted (in shares) \| shares	1,977,689
Vested (in shares) \| shares	(1,747,007)
Forfeited (in shares) \| shares	(209,239)
End of period (in shares) \| shares	5,831,794
Weighted- Average Grant Date Fair Value Per Share
Beginning balance (in dollars per share) \| $ / shares	$ 36.97
Granted (in dollars per share) \| $ / shares	66.07
Vested (in dollars per share) \| $ / shares	42.23
Forfeited (in dollars per share) \| $ / shares	27.89
Ending balance (in dollars per share) \| $ / shares	$ 45.60

Stock-Based Compensation

6 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

The Company has three plans that provide for equity-based compensation.

Under the 2013 Incentive Plan (the “2013 Plan”), 1,657,364 awards are granted and outstanding, relating to stock options and restricted stock awards to employees and directors as of March 31, 2026.

Under the 2021 Incentive Plan (the “2021 Plan”), 18,500,000 shares (subject to certain adjustments) of the Company’s common stock are authorized for grants of stock options, stock appreciation rights, restricted and unrestricted stock, performance awards, cash awards and other awards convertible into or otherwise based on shares of the Company’s common stock. The maximum number of shares authorized under the 2021 Plan will be (i) reduced by any shares subject to awards made under the 2013 Plan after January 1, 2021, and (ii) increased by any shares subject to outstanding awards under the 2013 Plan as of January 1, 2021 that, after January 1, 2021, are canceled, expired, forfeited or otherwise not issued under such awards (other than as a result of being tendered or withheld to pay the exercise price or withholding taxes in connection with any such awards) or settled in cash. As of March 31, 2026, 7,940,708 shares have been granted under the 2021 Plan, the total number of shares available for issuance was 11,354,663 shares, which includes 170,898 and 624,473 shares that were forfeited under the 2013 and 2021 Plans, respectively. This reflects an amendment and restatement of the 2021 Plan approved by the Company’s stockholders on March 19, 2026 to increase the total number of authorized shares by 10,500,000 shares and extend the term of the plan to January 21, 2036.

Under the Company’s Inducement Plan (the “Inducement Plan”), 832,950 shares of the Company’s common stock are authorized for issuance pursuant to grants of stock options, stock appreciation rights, restricted and unrestricted stock, stock units (including restricted stock units), performance awards, cash awards, and other awards convertible into or otherwise based on shares of the Company’s common stock. Awards under the Inducement Plan may only be granted to new employees of the Company in accordance with the provisions of Rule 5635(c)(4) of the Nasdaq Listing Rules. As of March 31, 2026, 807,012 shares have been granted, net of cancellations, under the Inducement Plan. The total number of shares remaining available for issuance was 25,938 shares.

In addition, prior to adoption of the Inducement Plan, the Company previously granted stand-alone inducement awards in the form of stock options and restricted stock units outside of the Company’s equity plans to new employees under Rule 5635(c)(4) of the Nasdaq Listing Rules. As of March 31, 2026, there were 399,705 and 50,850 shares underlying outstanding stand-alone inducement options and restricted stock units, respectively.

The following table presents a summary of awards outstanding attributable to Arrowhead Pharmaceuticals, Inc.:


	March 31, 2026
	2013 Plan	2021 Plan	Inducement Awards	Total
Granted and outstanding awards:
Options	557,364	22,965	399,705	980,034
Restricted stock units	1,100,000	4,030,971	700,823	5,831,794
Total	1,657,364	4,053,936	1,100,528	6,811,828

The following table summarizes stock-based compensation expenses included in operating expenses attributable to Arrowhead Pharmaceuticals, Inc.:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Research and development	$	8,441	$	7,264	$	14,817	$	14,110
Selling, general and administrative	8,127		7,817		21,341		15,147
Total	$	16,568	$	15,081	$	36,158	$	29,257

Stock Option Awards

The following table presents a summary of the stock option activity for the six months ended March 31, 2026:


	Shares	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding at September 30, 2025	1,407,035	$	28.90
Granted	—	—
Cancelled or expired	—	—
Exercised	(427,001)	17.26
Outstanding at March 31, 2026	980,034	$	33.83	3.3	$	29,108,721
Exercisable at March 31, 2026	980,034	$	33.83	3.3	$	29,108,721

The aggregate intrinsic values represent the amount by which the market price of the underlying stock exceeds the exercise price of the option. The total intrinsic value of the options exercised during the three months ended March 31, 2026 and 2025 was $5.8 million and $3.7 million, respectively. The total intrinsic value of the options exercised during the six months ended March 31, 2026 and 2025 was $18.4 million and $4.6 million, respectively.

Stock-based compensation expense related to stock options outstanding for the three months ended March 31, 2026 and 2025, was $0 and $3.0 thousand, respectively. Stock-based compensation expense related to stock options outstanding for the six months ended March 31, 2026 and 2025, was $0 and $0.1 million, respectively.

As of March 31, 2026, the pre-tax compensation expense for all outstanding unvested stock options is considered nominal.

The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options, which do not have vesting restrictions and are fully transferable. The determination of the fair value of each stock option is affected by the Company’s stock price on the date of grant, as well as assumptions regarding a number of highly complex and subjective variables. No options were granted during the six months ended March 31, 2026 and 2025.

Visirna ESOP: Through March 31, 2026, Visirna, a subsidiary of the Company, granted an aggregate of 16,400,000 stock options to its employees from the Employee Stock Option Plan (the “Visirna ESOP”), which authorizes 20,000,000 shares for issuance. The Visirna ESOP is independently managed by Visirna, including the valuation process. For the three months ended March 31, 2026 and 2025, stock-based compensation expense related to the Visirna ESOP was $0.1 million and $(0.1) million, respectively. For the six months ended March 31, 2026 and 2025, stock-based compensation expense related to the Visirna ESOP was $(0.1) million and $1.9 million, respectively.

Restricted Stock Units

Restricted Stock Units (“RSUs”), including market-based, time-based and performance-based awards, have been granted under the Company’s 2013 and 2021 Plans, the Inducement Plan, and as inducements awards granted outside of the Company’s equity-based compensation plans. At vesting, each outstanding RSU will be exchanged for one share of the Company’s common stock. RSU awards generally vest subject to the satisfaction of service requirements or the satisfaction of both service requirements and achievement of certain performance targets.

The following table summarizes the activity of the Company’s RSUs:


	Number of RSUs	Weighted- Average Grant Date Fair Value Per Share
Outstanding at September 30, 2025	5,810,351	$	36.97
Granted	1,977,689	66.07
Vested	(1,747,007)	42.23
Forfeited	(209,239)	27.89
Outstanding at March 31, 2026	5,831,794	$	45.60

The fair value of RSUs was determined based on the closing price of the Company’s common stock on the grant

date, with consideration given to the probability of achieving service and/or performance conditions for awards.

For the three months ended March 31, 2026 and 2025, the Company recorded $16.6 million and $15.1 million of expense related to RSUs, respectively. For the six months ended March 31, 2026 and 2025, the Company recorded $36.2 million and $29.2 million of expense related to RSUs, respectively. As of March 31, 2026, there was $171.5 million of total unrecognized compensation cost related to RSUs that is expected to be recognized over a weighted-average period of 2.4 years.

Net (Loss) Income Per Share (Tables)

6 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net (Loss) Income Per Share

The following table presents the computation of basic and diluted net (loss) income per share for the three and six months ended March 31, 2026 and 2025.


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands, except per share amounts)
Numerator:
Net (loss) income attributable to Arrowhead Pharmaceuticals, Inc.	$	(132,732)	$	370,445	$	(101,919)	$	197,360

Denominator:
Weighted-average basic shares outstanding (1)	142,417		133,363		139,762		129,059
Effect of dilutive securities	—		1,121		—		1,206
Weighted-average diluted shares outstanding (1)	142,417		134,484		139,762		130,265

Basic net (loss) income per share	$	(0.93)	$	2.78	$	(0.73)	$	1.53
Diluted net (loss) income per share	$	(0.93)	$	2.75	$	(0.73)	$	1.52

(1) Include shares of common stock into which the 2024 and 2026 Avoro Pre-Funded Warrants may be exercised. See Note 6.

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share


	Three Months Ended March 31,		Six Months Ended March 31,
	2026	2025	2026	2025
	(in thousands)
Options	1,022	760	1,160	750
Restricted stock units	5,605	5,289	5,389	4,567
If-converted common stock from convertible notes	7,057	—	3,489	—
Total	13,684	6,049	10,038	5,317

Liability Related to the Sale of Future Royalties

6 Months Ended

Mar. 31, 2026

LIABILITY RELATED TO THE SALE OF FUTURE ROYALTIES

In November 2022, the Company and Royalty Pharma entered into the Royalty Pharma Agreement, pursuant to which Royalty Pharma agreed to pay up to $410.0 million in cash to the Company in consideration for the Company’s future royalty interest in olpasiran, a siRNA originally developed by the Company and licensed to Amgen in September 2016 under the Olpasiran Agreement.

Pursuant to the Royalty Pharma Agreement, Royalty Pharma paid $250.0 million upfront and agreed to pay up to an additional $160.0 million in aggregate one-time milestone payments due if and when the following milestone events occur: (i) $50.0 million on completion of enrollment in the OCEAN Phase 3 clinical trial for olpasiran, (ii) $50.0 million upon receipt of FDA approval of olpasiran for an approved indication (reduction in the risk of myocardial infarction, urgent coronary revascularization, or coronary heart disease death in adults with established cardiovascular disease and elevated Lp(a)), and (iii) $60.0 million upon Royalty Pharma’s receipt of at least $70.0 million of royalty payments under the Royalty Pharma Agreement in any single calendar year. During the third quarter of fiscal 2024, Amgen completed enrollment of the Phase 3 OCEAN(a) outcomes trial of olpasiran, which triggered a $50.0 million milestone payment that the Company received in the same quarter. As of March 31, 2026, up to $110.0 million of additional milestone payments remain payable in the future, contingent upon the achievement of the remaining regulatory and royalty-based milestones.

In consideration for the payment of the foregoing amounts under the Royalty Pharma Agreement, Royalty Pharma is entitled to receive all royalties otherwise payable by Amgen to the Company under the Olpasiran Agreement. The Company remains eligible to receive any milestone payments potentially payable by Amgen under the Olpasiran Agreement.

The Company has evaluated the terms of the Royalty Pharma Agreement and concluded, in accordance with the relevant accounting guidance, that the Company accounted for the transaction as debt and the funding of $250.0 million and $50.0 million from Royalty Pharma were recorded as liabilities related to the sale of future royalties on its consolidated balance sheets. The Company is not obligated to repay these funds received under the Royalty Pharma Agreement.

The Company records the obligations at their carrying value using the effective interest method. In order to amortize the sale of future royalties, the Company utilizes the prospective method to estimate the future royalties to be paid by the Company to the counterparty over the life of the arrangement. Under the prospective method, a new effective interest rate is determined based on the revised estimate of remaining cash flows. The new rate is the discount rate that equates the present value of the revised estimate of remaining cash flows with the carrying amount of the debt, and it will be used to recognize non-cash interest expense for the remaining periods. The Company periodically assesses the amount and the timing of expected royalty payments using a combination of internal projections and forecasts from external sources. The estimates of future net product sales (and resulting royalty payments) are based on key assumptions including population, penetration, probability of success and sales price, among others. To the extent such payments are greater or less than the Company’s initial estimates or the timing of such payments is different than its original estimates, the Company will prospectively adjust the amortization of the royalty financing obligations and the effective interest rate.

During the three months ended March 31, 2026, the Company updated its estimates of future royalty payments based on revised assumptions related primarily to expected pricing, product launch timing, and projected sales. These revisions resulted in changes to the expected amount and timing of future cash flows and, accordingly, an increase in the effective interest rate. As a result, the estimated effective interest rate increased from 8.3% as of September 30, 2025 to 9.4% as of March 31, 2026.

The following table presents the activity with respect to the liability related to the sale of future royalties.


	Six Months Ended March 31,
	2026		2025
	(in thousands)
Beginning carrying value	$	367,397	$	341,361
Milestone payment received	—		—
Non-cash interest expense recognized	16,432		10,915
Ending carrying value	$	383,829	$	352,276

Collaboration and License Agreements (Tables)

6 Months Ended

Mar. 31, 2026

Collaboration And License Agreements [Abstract]

Schedule of Revenue

The following table provides a summary of revenue recognized from our collaboration and license agreements:


	Three Months Ended March 31,				Sixth Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
GSK	$	—	$	3	$	—	$	2,503
Sarepta	41,735		542,706		271,199		542,706
Novartis	20,471		—		54,713		—
Sanofi	10,533		—		10,742		—
Total	$	72,739	$	542,709	$	336,654	$	545,209

Schedule of Receivables and Contract Liabilities


	March 31, 2026		September 30, 2025
	(in thousands)
Receivables included in accounts receivable	$	14,512	$	6,824
Contract assets included in other current assets	$	—	$	—
Contract liabilities included in deferred revenue, current	$	108,543	$	2,399
Contract liabilities included in deferred revenue, non-current	$	48,615	$	—

Deferred revenue consisted of the following:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Balance at beginning of period	$	155,931	$	—	$	2,399	$	—
Deferred revenue additions	63,434		585,974		480,672		585,974
Revenue recognized	(62,207)		(542,706)		(325,913)		(542,706)
Balance at end of period	157,158		43,268		157,158		43,268
Plus contract assets included in other current assets	—		—		—		—
Less deferred revenue, current	(108,543)		(43,268)		(108,543)		(43,268)
Deferred revenue, non-current	$	48,615	$	—	$	48,615	$	—

Segment Information - Schedule of Research and Development and Selling, General and Administrative Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Stock compensation	$ 16,568	$ 15,081	$ 36,158	$ 29,257
Depreciation/amortization	5,900	5,600	11,900	10,400
Total research and development expense	173,253	133,102	350,456	270,104
Total selling, general and administrative expense	41,744	28,405	87,765	55,315
Research and development
Segment Reporting Information [Line Items]
Stock compensation	8,441	7,264	14,817	14,110
Selling, general and administrative
Segment Reporting Information [Line Items]
Stock compensation	8,127	7,817	21,341	15,147
Operating Segment
Segment Reporting Information [Line Items]
Candidate costs	99,449	71,191	204,439	148,087
Discovery costs	18,498	14,806	40,326	27,742
Salaries	33,546	26,907	63,585	54,052
Facilities related	7,595	6,737	15,697	14,487
Total research and development expense, excluding non-cash expense	159,088	119,641	324,047	244,368
Salaries	12,435	7,857	24,375	15,188
Professional, outside services, and other	18,940	10,815	37,841	20,941
Facilities related	1,496	1,082	3,159	2,367
Total selling, general and administrative expense, excluding non-cash expense	32,871	19,754	65,375	38,496
Total research and development expense	173,253	133,102	350,456	270,104
Total selling, general and administrative expense	41,744	28,405	87,765	55,315
Operating Segment \| Research and development
Segment Reporting Information [Line Items]
Stock compensation	8,297	7,888	14,655	15,437
Depreciation/amortization	5,868	5,573	11,754	10,299
Operating Segment \| Selling, general and administrative
Segment Reporting Information [Line Items]
Stock compensation	8,373	8,140	21,386	15,799
Depreciation/amortization	$ 500	$ 511	$ 1,004	$ 1,020

Financing Agreement - Schedule of Outstanding Balance of Credit Facility (Details) - USD ($) $ in Thousands	6 Months Ended		8 Months Ended	12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Sep. 30, 2025
Line of Credit Facility [Line Items]
Less: Current portion of credit facility	$ (40,000)		$ (40,000)	$ (40,000)
Less: Payments	(84,506)	$ (151,625)
Secured Debt \| Line of Credit
Line of Credit Facility [Line Items]
Initial Term Loan	349,114		349,114
Secured Debt \| Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Initial Term Loan	400,000		400,000	400,000
Accumulated interest on the Initial Term Loan	92,993		92,993	66,942
Accumulated accretion of the MOIC Payment	5,940		5,940	3,478
Less: Unamortized debt issuance costs	(13,163)		(13,163)	(13,912)
Less: Current portion of credit facility	(40,000)		(40,000)	(40,000)
Less: Payments	(286,131)		(286,100)	(201,625)
Credit facility, net of current portion	$ 159,639		$ 159,639	$ 214,883

Convertible Notes - Schedule of Convertible Debt (Details) - Convertible Notes - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Debt Instrument [Line Items]
Outstanding principal balance	$ 700,000	$ 0
Less: Unamortized debt issuance costs	(18,060)	0
Convertible Notes, Net	$ 681,940	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References

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+ Details

Stockholders' Equity

6 Months Ended

Mar. 31, 2026

Equity [Abstract]

Stockholders' Equity

STOCKHOLDERS’ EQUITY

The following table summarizes the Company’s shares of common stock and preferred stock:


			Shares
	Par Value		Authorized	Issued	Outstanding
			(in thousands)
As of March 31, 2026
Common stock (1)	$	0.001	290,000	143,232	140,571
Preferred stock	$	0.001	5,000	—	—

As of September 30, 2025
Common stock (1)	$	0.001	290,000	138,363	135,702
Preferred stock	$	0.001	5,000	—	—

(1) Does not include shares of common stock into which the 2024 and 2026 Avoro Pre-Funded Warrants may be exercised.

As of March 31, 2026 and September 30, 2025, respectively, 18,192,429 and 9,851,400 shares of common stock were reserved for issuance upon exercise of options and vesting of restricted stock units granted or available for grant under the Company’s 2013 and 2021 Incentive Plans, as well as for other inducement grants made to new employees under Rule 5635(c)(4) of the Nasdaq Listing Rules.

On November 25, 2024, the Company entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with an institutional and accredited investor for a private placement of pre-funded warrants to purchase shares of common stock with an exercise price of $0.001 per share (“2024 Avoro Pre-Funded Warrants”). Pursuant to the Securities Purchase Agreement, the Company sold pre-funded warrants to purchase up to 917,441 shares of common stock at a purchase price of $27.25 per pre-funded warrant, for an aggregate value of approximately $25.0 million. The outstanding 2024 Avoro Pre-Funded Warrants are exercisable at any time and do not have an expiration date.

The Company concluded that the 2024 Avoro Pre-funded Warrants are both indexed to its own stock and meet all other conditions for equity classification. Accordingly, the Company has classified the 2024 Avoro Pre-funded Warrants as equity and recorded within additional paid-in capital. As of March 31, 2026, no shares underlying the 2024 Avoro Pre-Funded Warrants had been exercised.

In connection with the Sarepta Collaboration Agreement, on November 25, 2024, the Company entered into the Stock Purchase Agreement with an affiliate of Sarepta for a private placement of shares of common stock of the Company (the “Private Placement”). Pursuant to the Stock Purchase Agreement, the Company sold 11,926,301 shares of common stock, at a price per share of $27.25, for an aggregate value of approximately $325.0 million. The Private Placement closed on February 7, 2025. On August 13, 2025, the Company subsequently entered into an agreement with Sarepta to repurchase 2,660,989 common stock of the Company from Sarepta at a price per share of $18.79 for an aggregate value of approximately $50.0 million and approximately $50.0 million in cash to partially satisfy the milestone payment of $100.0 million due from Sarepta. The shares were recorded as treasury stock at their fair value of $53.2 million, resulting in a $3.2 million gain on settlement. As of the end of fiscal 2025, Sarepta no longer holds an equity position in the Company.

On December 2, 2022, the Company entered into an open market sale agreement (the “Open Market Sale Agreement”) with Jefferies LLC (“Jefferies”). On December 10, 2025, the Company entered into an Amended and Restated Open Market Sale Agreement (the “Amended and Restated Sale Agreement”) with Jefferies, which amended and restated the Open Market Sale Agreement in its entirety. Under the Amended and Restated Sale Agreement, the Company may, from time to time, sell up to $500.0 million in shares of the Company’s common stock through Jefferies, acting as the sales agent and/or principal, in an at-the-market offering (“ATM Offering”). The Amended and Restated Sale Agreement continues to provide for the sale, from time to time, of shares of the Company’s common stock up to the maximum program amount permitted under the Company’s shelf registration statement and subject to continued compliance with the terms of the Amended and Restated Sale Agreement, including the delivery of issuance notices, prospectus supplements, and periodically updated representations, warranties, and deliverables. The Company pays Jefferies a commission of up to 3.0% of the aggregate gross proceeds received from all sales of the common stock under the ATM Offering. The Amended and Restated Sale Agreement may be terminated by either party upon written notice.

During the first quarter of fiscal 2026, the Company sold approximately 689,000 shares of common stock under the ATM Offering, generating gross proceeds of $48.2 million and net proceeds of $46.8 million, after deducting underwriting commissions and offering costs. The Company did not make any sales under the ATM Offering during the second quarter

of fiscal 2026.

On January 7, 2026, the Company entered into an underwriting agreement with Jefferies and J.P. Morgan Securities, LLC (“J.P. Morgan”) for an underwritten public offering (the “2026 Offering”) of: (i) 2,015,505 shares of common stock with $0.001 par value per share, at a public offering price of $64.50 per share, and (ii) pre‑funded warrants (“2026 Avoro Pre-Funded Warrants”) to purchase 1,550,387 shares of common stock, at a public offering price of $64.499 per share, which represents the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. The 2026 Offering closed on January 9, 2026, generating gross proceeds of $230 million and net proceeds of $216.6 million after deducting the underwriting discounts and commissions and other offering expenses. The Company concluded that the 2026 Avoro Pre-funded Warrants are both indexed to its own stock and meet all other conditions for equity classification. Accordingly, the Company has classified the 2026 Avoro Pre-funded Warrants as equity and recorded within additional paid-in capital. As of March 31, 2026, no shares underlying the 2026 Avoro Pre-Funded Warrants had been exercised.

On January 2, 2026, option holders of Visirna, the Company's consolidated variable interest entity, exercised 14,000,000 stock options. As a result, the Company’s ownership interest in Visirna decreased from 66.25% to 56.38%. Because the Company retained its controlling financial interest in Visirna, the change in ownership was accounted for as an equity transaction in accordance with ASC 810-10-45-22 through 45-24.

The noncontrolling interest was increased by $3.1 million to reflect the change in ownership resulting from exercise of 14,000,000 stock options by Visirna option holders. The decrease of $3.1 million was recorded to additional paid‑in capital attributable to Arrowhead.

During the first quarter of fiscal 2026, Visirna declared a cash dividend of $100.0 million to its shareholders. As of December 31, 2025, the portion of the dividend declared payable to the Company’s noncontrolling shareholders totaled $40.5 million and was included in the accompanying consolidated statements of equity. In March 2026, Visirna paid cash dividends totaling $94.8 million, consisting of $56.4 million paid to the Company and $38.4 million paid to the Company’s noncontrolling shareholders. The remaining $3.1 million of the declared dividend represents exercise prices paid by certain noncontrolling shareholders in connection with the exercise of their stock options, which were netted against the dividend otherwise payable to those shareholders. As of March 31, 2026, Visirna had a remaining dividend payable of $2.1 million to the Company’s noncontrolling shareholder, which was included in accrued expenses in the accompanying consolidated balance sheets.

- Definition

The entire disclosure for equity.

+ References

+ Details

Leases

6 Months Ended

Mar. 31, 2026

Leases [Abstract]

Leases

LEASES

Pasadena, California: The Company leases 49,000 square feet of office space located at 177 East Colorado Blvd. for its corporate headquarters from 177 Colorado Owner, LLC. The lease expires on April 30, 2027, and contains an option to renew for one additional five-year term. As of March 31, 2026, the Company had not exercised the renewal option and therefore it is not included in right-of-use assets and liabilities. Subsequent to March 31, 2026, the Company entered into a lease amendment with 177 Colorado Owner, LLC. See Note 17, Subsequent Events.

San Diego, California: The Company leases 144,000 square feet of office and research and development laboratory space located at 10102 Hoyt Park from 11404 & 11408 Sorrento Valley Owner, LLC, which lease expires on April 30, 2038. Pursuant to the lease, within twelve months of the expiration of the initial 15-year term, the Company has the option to extend the lease for up to one additional ten-year term, with certain annual increases in base rent. The Company is not reasonably certain that it will exercise this option to renew and therefore it is not included in right-of-use assets and liabilities as of March 31, 2026.

The lease agreement, as amended, granted the Company the right to receive an Additional Tenant Improvement Allowance (“ATIA”) funded by the lessor. The Company received $30.8 million in ATIA, including a final payment of $3.1 million during the first quarter of fiscal 2024. As a result, the Company remeasured its lease liability and right-of-use assets to reflect these additional allowances and the related increased lease payments. The Company has further concluded that these ATIAs have no effects on the classification of the lease.

Madison, Wisconsin: The Company leases 110,956 square feet space, which it increased from 107,000 square feet on June 30, 2025, located at 502 South Rosa Road for its office and laboratory facilities, which lease expires on September 30, 2031. The lease contains options to renew for two terms of five years. The Company is not reasonably certain that it will exercise this option and therefore it is not included in right-of-use assets and liabilities as of March 31, 2026.

The components of lease assets and liabilities along with their classification on the Company’s consolidated balance sheets were as follows:


Lease Assets and Liabilities	Classification	March 31, 2026		September 30, 2025
		(in thousands)

Operating lease assets	Right-of-use assets	$	42,794	$	43,891
Current operating lease liabilities	Lease liabilities	7,774		7,289
Non-current operating lease liabilities	Lease liabilities, net of current portion	100,106		104,112


			Three Months Ended March 31,				Six Months Ended March 31,
Lease Cost	Classification		2026		2025		2026		2025
		(in thousands)

Operating lease cost	Research and development		$	2,789	$	2,709	$	5,518	$	5,520
	Selling, general and administrative		497		500		1,008		993

Variable lease cost (1)	Research and development		1,138		951		2,090		1,937
	Selling, general and administrative		—		—		—		—

Total			$	4,424	$	4,160	$	8,616	$	8,450

(1) Variable lease cost is primarily related to operating expenses associated with the Company’s operating leases.

There was no short-term lease cost during the three and six months ended March 31, 2026 and 2025, respectively.

The following table presents maturities of operating lease liabilities on an undiscounted basis as of March 31, 2026:


Year	Amounts
	(in thousands)
2026 (remainder)	$	7,986
2027	15,050
2028	13,696
2029	13,985
2030	14,282
2031 and thereafter	100,672
Total	$	165,671
Less imputed interest	(57,791)
Total operating lease liabilities (includes current portion)	$	107,880

Supplemental cash flow and other information related to leases was as follows:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026			2025
	(in thousands)




Operating cash flows from operating leases	$	3,944	$	3,840	$	7,887		$	7,680
					March 31,
					2026			2025
Weighted-average remaining lease term (in years)					11.3			12.1
Weighted-average discount rate					8.0		%	8.0		%

Financing Agreement - Narrative (Details) $ in Thousands, ¥ in Millions					1 Months Ended			3 Months Ended	6 Months Ended		8 Months Ended	12 Months Ended
	Aug. 13, 2025 USD ($)	Feb. 14, 2025 USD ($)	Nov. 26, 2024	Aug. 07, 2024 USD ($)	Feb. 28, 2026 USD ($)	Aug. 31, 2025 USD ($)	May 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2026 CNY (¥)	May 31, 2025 CNY (¥)
Line of Credit Facility [Line Items]
Repayments of credit facility									$ 84,506	$ 151,625
Credit facility								$ 40,000	40,000		$ 40,000	$ 40,000
Sarepta \| Sarepta Collaboration Agreement
Line of Credit Facility [Line Items]
Upfront payment	$ 50,000	$ 500,000			$ 50,000	$ 50,000		50,000
Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Interest rate				15.00%
Secured Debt \| Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 500,000
Long-term line of credit				400,000
Line of credit facility, remaining borrowing capacity				$ 100,000
Multiple of invested capital rate				2
Basis spread on variable rate				0.50%
Repayments of credit facility									286,131		286,100	201,625
Covenant, minimum liquidity cash, cash equivalents and investments									250,000		250,000
Covenant, market capitalization threshold									2,000,000		2,000,000
Covenant, convertible indebtedness outstanding maximum									$ 300,000		$ 300,000
Covenant, convertible indebtedness outstanding, marked capitalization percentage, maximum									10.00%		10.00%		10.00%
Covenant, aggregate convertible indebtedness outstanding, maximum									$ 700,000		$ 700,000
Credit facility								$ 40,000	40,000		40,000	$ 40,000
Secured Debt \| Financing Agreement, MOIC Payment \| Line of Credit
Line of Credit Facility [Line Items]
Multiple of invested capital rate				2.5
Debt instrument, prepayment percentage			50.00%
Repayments of credit facility											142,300
MOIC payments expected to be applied to principal upon repayment									21,500		21,500
Secured Debt \| Financing Agreement, Initial Term Loan \| Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, prepayment percentage			50.00%
Revolving Credit Facility \| Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity							$ 10,500							¥ 72.9
Interest rate							4.10%							4.10%
Debt instrument term							12 months
Credit facility									$ 10,500		$ 10,500		¥ 72.9

Subsequent Events	6 Months Ended
Subsequent Events	Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Lease Amendment On April 27, 2026, the Company entered into a lease amendment (the “Pasadena Lease Amendment”) with 177 Colorado Owner, LLC for its corporate headquarters located at 177 East Colorado Blvd. in Pasadena, California (the “Premises”). Under the terms of the Pasadena Lease Amendment, the Company will lease approximately 98,444 square feet of office space at the Premises. The 2026 Pasadena Lease Amendment is expected to commence on the later of May 1, 2027, or the date of substantial completion of tenant improvements, but in no event later than August 1, 2027. The Pasadena Lease Amendment has a lease term of seven years and eight months and provides two consecutive options to extend the lease term by five years each. Total rent and other obligations under the Pasadena Lease Amendment are expected to be approximately $50.3 million. Licensing Agreement On May 4, 2026, the Company entered into a Licensing Agreement with Madrigal Pharmaceuticals, Inc., (“Madrigal”). Under the terms of the agreement, Madrigal will receive an exclusive global license to develop, manufacture, and commercialize ARO-PNPLA3, a clinical stage program. The Company will receive an upfront payment of $25.0 million, and is eligible to receive milestone payments of up to $975.0 million. The Company is further eligible to receive tiered royalties on commercial sales ranging from high-single digits to the mid-teens.

Convertible Notes (Tables)

6 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Schedule of Convertible Debt

The outstanding balance of the Notes consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Outstanding principal balance	$	700,000	$	—
Less: Unamortized debt issuance costs	(18,060)		—
Convertible Notes, Net	$	681,940	$	—

The following table sets forth total interest expense recognized related to the Notes:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	657	$	—	$	657	$	—
Total interest expense	$	657	$	—	$	657	$	—

Convertible Notes

6 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Convertible Notes

FINANCING AGREEMENT

The Company is permitted to use the net proceeds for working capital, capital expenditures and general corporate purposes of the Company and its subsidiaries.

The Financing Agreement contains certain embedded features that were identified and evaluated as not material to the consolidated financial statements.

On August 13, 2025, the Company entered into second amendment to the Financing Agreement (the "Second

Amendment") that permitted the share repurchase of the Company's common stock from Sarepta and required the Company to pay a nominal administrative fee.

The outstanding balance of the Credit Facility consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Initial Term Loan	$	400,000	$	400,000
Accumulated interest on the Initial Term Loan	92,993		66,942
Accumulated accretion of the MOIC Payment	5,940		3,478
Less: Unamortized debt issuance costs	(13,163)		(13,912)
Less: Current portion of credit facility	(40,000)		(40,000)
Less: Payments	(286,131)		(201,625)
Credit facility, net of current portion	$	159,639	$	214,883

The following table sets forth total interest expense recognized related to the Credit Facility:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	367	$	1,129	$	748	$	1,682
Accretion of the MOIC Payment	1,178		—		2,462		—
Contractual interest expense	12,812		15,009		26,052		30,687
Total interest expense	$	14,357	$	16,138	$	29,262	$	32,369


Year	Amounts
	(in thousands)
2026 (remainder)	$	25,000
2027	40,000
2028	15,000
2029	15,000
2030	15,000
Thereafter	239,114
Total	$	349,114

CONVERTIBLE NOTES

The outstanding balance of the Notes consisted of the following:


	March 31, 2026		September 30, 2025
	(in thousands)
Outstanding principal balance	$	700,000	$	—
Less: Unamortized debt issuance costs	(18,060)		—
Convertible Notes, Net	$	681,940	$	—

The following table sets forth total interest expense recognized related to the Notes:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Amortization of debt issuance costs	$	657	$	—	$	657	$	—
Total interest expense	$	657	$	—	$	657	$	—

Capped Call Transactions

Liability Related to the Sale of Future Royalties (Tables)

6 Months Ended

Mar. 31, 2026

Schedule of Liability Related to the Sale of Future Royalties

The following table presents the activity with respect to the liability related to the sale of future royalties.


	Six Months Ended March 31,
	2026		2025
	(in thousands)
Beginning carrying value	$	367,397	$	341,361
Milestone payment received	—		—
Non-cash interest expense recognized	16,432		10,915
Ending carrying value	$	383,829	$	352,276

Convertible Notes - Schedule of Interest Expense Recognized Related to Notes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 657	$ 0
Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Amortization of debt issuance costs	$ 657	$ 0	657	0
Total interest expense	$ 657	$ 0	$ 657	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Collaboration and License Agreements - Amgen, Inc. (Details)	Mar. 31, 2026 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Sep. 30, 2016 agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract assets	$ 0	$ 0	$ 0
Contract liabilities included in deferred revenue, current	108,543,000	$ 2,399,000	$ 43,268,000
Amgen Incorporated \| Olpasiran Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of agreements \| agreement				2
Contract assets	0
Contract liabilities included in deferred revenue, current	0
Amgen Incorporated \| Olpasiran Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments	$ 485,000,000.0

Collaboration and License Agreements - Schedule of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenue	$ 73,737	$ 542,709	$ 337,770	$ 545,209
Collaboration and License Agreements
Disaggregation of Revenue [Line Items]
Revenue	72,739	542,709	336,654	545,209
Collaboration and License Agreements \| GSK
Disaggregation of Revenue [Line Items]
Revenue	0	3	0	2,503
Collaboration and License Agreements \| Sarepta
Disaggregation of Revenue [Line Items]
Revenue	41,735	542,706	271,199	542,706
Collaboration and License Agreements \| Novartis
Disaggregation of Revenue [Line Items]
Revenue	20,471	0	54,713	0
Collaboration and License Agreements \| Sanofi
Disaggregation of Revenue [Line Items]
Revenue	$ 10,533	$ 0	$ 10,742	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
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-Paragraph 91
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
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-Paragraph 91
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Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
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-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (e)
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-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Commitments and Contingencies (Details)	Mar. 31, 2026 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contingent liabilities	$ 0

Stock-Based Compensation (Tables)

6 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Schedule of Awards Outstanding

The following table presents a summary of awards outstanding attributable to Arrowhead Pharmaceuticals, Inc.:


	March 31, 2026
	2013 Plan	2021 Plan	Inducement Awards	Total
Granted and outstanding awards:
Options	557,364	22,965	399,705	980,034
Restricted stock units	1,100,000	4,030,971	700,823	5,831,794
Total	1,657,364	4,053,936	1,100,528	6,811,828

Schedule of Stock-Based Compensation Expenses

The following table summarizes stock-based compensation expenses included in operating expenses attributable to Arrowhead Pharmaceuticals, Inc.:


	Three Months Ended March 31,				Six Months Ended March 31,
	2026		2025		2026		2025
	(in thousands)
Research and development	$	8,441	$	7,264	$	14,817	$	14,110
Selling, general and administrative	8,127		7,817		21,341		15,147
Total	$	16,568	$	15,081	$	36,158	$	29,257

Schedule of Stock Option Activity

The following table presents a summary of the stock option activity for the six months ended March 31, 2026:


	Shares	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding at September 30, 2025	1,407,035	$	28.90
Granted	—	—
Cancelled or expired	—	—
Exercised	(427,001)	17.26
Outstanding at March 31, 2026	980,034	$	33.83	3.3	$	29,108,721
Exercisable at March 31, 2026	980,034	$	33.83	3.3	$	29,108,721

Schedule of Share Activity Related to RSUs

The following table summarizes the activity of the Company’s RSUs:


	Number of RSUs	Weighted- Average Grant Date Fair Value Per Share
Outstanding at September 30, 2025	5,810,351	$	36.97
Granted	1,977,689	66.07
Vested	(1,747,007)	42.23
Forfeited	(209,239)	27.89
Outstanding at March 31, 2026	5,831,794	$	45.60

Segment Information - Narrative (Details)	6 Months Ended
Segment Information - Narrative (Details)	Mar. 31, 2026 segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1