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Document and Entity Information - shares	3 Months Ended
Dec. 31, 2014	Feb. 05, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2014
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	ARWR
Entity Registrant Name	ARROWHEAD RESEARCH CORP
Entity Central Index Key	0000879407
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		54,792,649

Consolidated Balance Sheets - USD ($)	Dec. 31, 2014	Sep. 30, 2014
CURRENT ASSETS
Cash and cash equivalents	$ 103,991,231	$ 132,510,610
Trade receivables	127,000
Prepaid expenses	4,451,124	588,626
Other current assets	62,841	48,502
Short term investments	23,532,402	21,653,032
TOTAL CURRENT ASSETS	132,164,598	154,800,770
Property and equipment, net	4,124,441	3,872,753
Intangible assets, net	999,809	1,013,473
Investments	17,806,499	23,088,346
Other assets	7,041,414	41,414
TOTAL ASSETS	162,136,761	182,816,756
CURRENT LIABILITIES
Accounts payable	5,994,951	2,579,478
Accrued expenses	1,148,092	1,399,486
Accrued payroll and benefits	2,175,484	3,268,506
Deferred revenue	109,375	103,125
Derivative liabilities	1,790,559	4,173,943
Capital lease obligation	213,991	213,991
Notes payable		50,000
Other current liabilities	65,213	58,495
TOTAL CURRENT LIABILITIES	11,497,665	11,847,024
LONG-TERM LIABILITIES
Capital lease obligation, net of current portion	705,173	758,340
Contingent consideration obligations	3,970,931	3,970,931
Other non-current liabilities	253,321	255,206
TOTAL LONG-TERM LIABILITIES	4,929,425	4,984,477
Commitments and contingencies
Arrowhead Research Corporation stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 18,300 and 18,300 shares issued and outstanding as of December 31, 2014 and September 30, 2014, respectively	18	18
Common stock, $0.001 par value; 145,000,000 shares authorized; 54,715,714 and 54,656,936 shares issued and outstanding as of December 31, 2014 and September 30, 2014, respectively	147,085	147,026
Additional paid-in capital	393,464,197	391,164,558
Accumulated deficit	(247,346,441)	(224,771,159)
Total Arrowhead Research Corporation stockholders' equity	146,264,859	166,540,443
Noncontrolling interest	(555,188)	(555,188)
TOTAL STOCKHOLDERS’ EQUITY	145,709,671	165,985,255
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 162,136,761	$ 182,816,756

Consolidated Statements of Operations (unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
REVENUE	$ 170,750	$ 43,750
OPERATING EXPENSES
Research and development	17,744,312	3,133,014
Salaries and payroll-related costs	3,150,617	2,081,791
General and administrative expenses	2,086,202	913,784
Stock-based compensation	2,014,856	521,138
Depreciation and amortization	290,039	403,405
TOTAL OPERATING EXPENSES	25,286,026	7,053,132
OPERATING LOSS	(25,115,276)	(7,009,382)
OTHER INCOME (EXPENSE)
Equity in income (loss) of unconsolidated affiliates		(138,456)
Gain (loss) on sale of fixed assets, net	(26,381)	(53,562)
Interest income (expense), net	237,417	40,578
Change in value of derivatives	2,382,142	(3,519,579)
Other income (expense)	(53,184)	(5,331)
TOTAL OTHER INCOME (EXPENSE)	2,539,994	(3,676,350)
LOSS BEFORE INCOME TAXES	(22,575,282)	(10,685,732)
NET LOSS	(22,575,282)	(10,685,732)
Net loss attributable to noncontrolling interests		57,420
NET LOSS ATTRIBUTABLE TO ARROWHEAD	$ (22,575,282)	$ (10,628,312)
NET LOSS PER SHARE ATTRIBUTABLE TO ARROWHEAD SHAREHOLDERS - BASIC AND DILUTED:	$ (0.41)	$ (0.28)
Weighted average shares outstanding - basic and diluted	54,692,392	37,741,743

Consolidated Statement of Stockholders' Equity (unaudited) - USD ($)	Total	Common stock issued @ $5.86	Common stock issued @ $18.95	Preferred stock issued at $1,000 per share	Common Stock Issued to Galloway	Preferred Stock	Preferred Stock Preferred stock issued at $1,000 per share	Common Stock	Common Stock Common stock issued @ $5.86	Common Stock Common stock issued @ $18.95	Common Stock Common Stock Issued to Galloway	Additional Paid-in Capital	Additional Paid-in Capital Common stock issued @ $5.86	Additional Paid-in Capital Common stock issued @ $18.95	Additional Paid-in Capital Preferred stock issued at $1,000 per share	Additional Paid-in Capital Common Stock Issued to Galloway	Accumulated Deficit during Development Stage	Non-controlling Interest
Beginning Balance Amount at Sep. 30, 2013	$ 25,734,789					$ 10		$ 124,859				$ 193,514,766					$ (166,140,969)	$ (1,763,877)
Beginning Balance Shares at Sep. 30, 2013						9,900		32,489,444
Exercise of warrants, Amount	10,148,044							$ 2,911				10,145,133
Exercise of warrants								2,911,919
Stock options exercised, Amount	$ 2,730,000							$ 455				2,729,545
Stock options exercised	454,863							454,863
Stock-based compensation	$ 5,696,173											5,696,173
Stock issuances		$ 14,060,112	$ 112,581,559	$ 46,000,000	$ 500,000		$ 46		$ 3,072	$ 6,325	$ 132		$ 14,057,040	$ 112,575,234	$ 45,999,954	$ 499,868
Stock issuances, Shares							46,000		3,071,672	6,325,000	131,579
Settlements related to derivative liability	5,956,079											5,956,079
Preferred stock converted to common stock, Amount						$ (38)		$ 9,272				(9,234)
Preferred stock converted to common stock, Shares						(37,600)		9,272,459
Deconsolidation of Calando Pharmaceuticals, Inc.	1,303,911																	1,303,911
Net loss	(58,725,412)																(58,630,190)	(95,222)
Ending Balance Amount at Sep. 30, 2014	165,985,255					$ 18		$ 147,026				391,164,558					(224,771,159)	(555,188)
Ending Balance Shares at Sep. 30, 2014						18,300		54,656,936
Exercise of warrants, Amount	270,624							$ 53				270,571
Exercise of warrants								53,578
Stock options exercised, Amount	$ 12,976							$ 3				12,973
Stock options exercised	2,500							2,500
Stock-based compensation	$ 2,014,856											2,014,856
Exercise of exchange rights, Amount	1,242							$ 3				1,239
Exercise of exchange rights, Shares								2,700
Net loss	(22,575,282)																(22,575,282)
Ending Balance Amount at Dec. 31, 2014	$ 145,709,671					$ 18		$ 147,085				$ 393,464,197					$ (247,346,441)	$ (555,188)
Ending Balance Shares at Dec. 31, 2014						18,300		54,715,714

Consolidated Statements of Cash Flows (unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (22,575,282)	$ (10,685,732)
Net loss attributable to noncontrolling interests		57,420
NET LOSS ATTRIBUTABLE TO ARROWHEAD	(22,575,282)	(10,628,312)
(Gain) loss on disposal of fixed assets	26,381	53,562
Change in value of derivatives	(2,382,142)	3,519,579
Stock-based compensation	2,014,856	521,138
Depreciation and amortization	290,039	403,405
Amortization/accretion of note premiums/discounts, net	347,703	28,443
Non-controlling interest		(57,420)
Changes in operating assets and liabilities:
Receivables	(127,000)	(11,825)
Other receivables	(9,506)
Prepaid expenses	(3,874,051)	(74,455)
Accounts payable	3,415,473	(610,284)
Accrued expenses	(1,325,675)	56,648
Other liabilities	(802)	(222,811)
NET CASH USED IN OPERATING ACTIVITIES	(24,200,006)	(7,022,332)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(554,945)	(116,215)
Proceeds from sale of fixed assets	500
Purchase of marketable securities		(19,075,306)
Proceeds from sale of marketable securities	3,054,774	4,045,956
Other investing activities	(7,000,000)
NET CASH USED IN INVESTING ACTIVITIES	(4,499,671)	(15,145,565)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on capital leases and notes payable	(103,168)	(54,715)
Proceeds from issuance of common stock and preferred stock, net		62,821,592
Proceeds from the exercise of warrants and stock options	283,466
NET CASH PROVIDED BY FINANCING ACTIVITIES	180,298	62,766,877
NET INCREASE (DECREASE) IN CASH	(28,519,379)	40,598,980
CASH AT BEGINNING OF PERIOD	132,510,610	19,114,444
CASH AT END OF PERIOD	103,991,231	59,713,424
Supplementary disclosures:
Interest paid	$ 3,938	$ 9,496

Organization and Significant Accounting Policies	3 Months Ended
Organization and Significant Accounting Policies	Dec. 31, 2014
Accounting Policies [Abstract]
Organization and Significant Accounting Policies	NOTE 1. ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES Nature of Business Arrowhead Research Corporation develops novel drugs to treat intractable diseases by silencing the genes that cause them. Using the broadest portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep and durable knockdown of target genes. Arrowhead’s most advanced drug candidate in clinical development is ARC-520, which is designed to treat chronic hepatitis B infection by inhibiting the production of all HBV gene products. The goal is to reverse the immune suppression that prevents the body from controlling the virus and clearing the disease. Arrowhead’s second clinical candidate is ARC-AAT, a treatment for a rare liver disease associated with a genetic disorder that causes alpha-1 antitrypsin deficiency. Liquidity Historically, the Company’s primary source of financing has been through the sale of securities of Arrowhead. Research and development activities have required significant capital investment since the Company’s inception. We expect our operations to continue to require cash investment in fiscal 2015 and beyond as the Company pursues its research and development goals, as well as clinical trials and related drug manufacturing. At December 31, 2014, the Company had $104.0 million in cash to fund operations. In addition to its cash resources, the Company has invested excess cash in investment grade commercial bonds maturing in less than 24 months. These bonds provide a source of liquidity, though the Company plans to hold them until maturity. At December 31, 2014, the Company had invested $41.3 million in bonds. During the three months ended December 31, 2014, the Company’s cash position decreased by $28.5 million which was primarily the result of cash outflows related to continuing operating activities of $24.2 million, other investing activities of $7.0 million and capital expenditures of $0.5 million. These outflows were partially offset by maturities of fixed income investments totaling $3.1 million and proceeds from the exercise of warrants and options of $0.3 million. Summary of Significant Accounting Policies Principles of Consolidation—The consolidated financial statements include the accounts of Arrowhead and its Subsidiaries. Arrowhead’s primary operating subsidiary is Arrowhead Madison, which is located in Madison, Wisconsin, where the Company’s research and development facility is located. All significant intercompany accounts and transactions are eliminated in consolidation. Basis of Presentation and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Additionally, certain reclassifications have been made to prior period financial statements to conform to the current period presentation. Cash and Cash Equivalents—The Company considers all liquid debt instruments purchased with a maturity of three months or less to be cash equivalents. The Company had no restricted cash at December 31, 2014 and September 30, 2014. Concentration of Credit Risk—The Company maintains several bank accounts for its operations at two financial institutions. These accounts are insured by the Federal Deposit Insurance Corporation (FDIC) for up to $250,000 per account. Management believes the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which these deposits are held. Investments—The Company may invest excess cash balances in short-term and long-term marketable debt securities. Investments may consist of certificates of deposits, money market accounts, government-sponsored enterprise securities, corporate bonds and/or commercial paper. The Company accounts for its investment in marketable securities in accordance with FASB ASC 320, Investments – Debt and Equity Securities. This statement requires certain securities to be classified into three categories: Held-to-maturity—Debt securities that the entity has the positive intent and ability to hold to maturity are reported at amortized cost. Trading Securities—Debt and equity securities that are bought and held primarily for the purpose of selling in the near term are reported at fair value, with unrealized gains and losses included in earnings. Available-for-Sale—Debt and equity securities not classified as either securities held-to-maturity or trading securities are reported at fair value with unrealized gains or losses excluded from earnings and reported as a separate component of shareholders’ equity. The Company classifies its investments in marketable debt securities based on the facts and circumstances present at the time of purchase of the securities. At December 31, 2014, the Company classified all of its investments as held-to-maturity. Held-to-maturity investments are measured and recorded at amortized cost on the Company’s Consolidated Balance Sheet. Discounts and premiums to par value of the debt securities are amortized to interest income/expense over the term of the security. No gains or losses on investment securities are realized until they are sold or a decline in fair value is determined to be other-than-temporary. Property and Equipment—Property and equipment are recorded at cost, which may equal fair market value in the case of property and equipment acquired in conjunction with a business acquisition. Depreciation of property and equipment is recorded using the straight-line method over the respective useful lives of the assets ranging from three to seven years. Leasehold improvements are amortized over the lesser of the expected useful life or the remaining lease term. Long-lived assets, including property and equipment are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable. Intangible Assets Subject to Amortization—At December 31, 2014, intangible assets subject to amortization include certain license agreements. Intangible assets subject to amortization are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable. In-Process Research & Development (IPR&D)—IPR&D assets represent capitalized on-going research projects that were acquired through business combinations. Such assets are initially measured at their acquisition date fair values. The amounts capitalized are being accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of R&D efforts associated with the project. Upon successful completion of a project, Arrowhead will make a determination as to the then remaining useful life of the intangible asset and begin amortization. Arrowhead tests its indefinite-lived assets for impairment at least annually, through a two-step process. The first step is a qualitative assessment to determine if it is more likely than not that the indefinite lived assets are impaired. Arrowhead considers relevant events and circumstances that could affect the inputs used to determine the fair value of the intangible assets. If the qualitative assessment indicates that it is more likely than not that the intangible assets are impaired, a second step is performed which is a quantitative test to determine the fair value of the intangible asset. If the carrying amount of the intangible assets exceeds its fair value, an impairment loss is recorded in the amount of that excess. If circumstances determine that it is appropriate, the Company may also elect to bypass step one, and proceed directly to the second step. Contingent Consideration - The consideration for the Company’s acquisitions often includes future payments that are contingent upon the occurrence of a particular event. For example, milestone payments might be based on the achievement of various regulatory approvals or future sales milestones, and royalty payments might be based on drug product sales levels. The Company records a contingent consideration obligation for such contingent payments at fair value on the acquisition date. The Company estimates the fair value of contingent consideration obligations through valuation models designed to estimate the probability of such contingent payments based on various assumptions and incorporating estimated success rates. Estimated payments are discounted using present value techniques to arrive at estimated fair value at the balance sheet date. Changes in the fair value of our contingent consideration obligations are recognized within the Company’s Consolidated Statements of Operations. Changes in the fair value of the contingent consideration obligations can result from changes to one or multiple inputs, including adjustments to the discount rates, changes in the amount or timing of expected expenditures associated with product development, changes in the amount or timing of cash flows from products upon commercialization, changes in the assumed achievement or timing of any development milestones, changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements are based on significant inputs not observable in the market. Substantial judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions could have a material impact on the amount of contingent consideration expense the Company records in any given period. Revenue Recognition—Revenue from license fees are recorded when persuasive evidence of an arrangement exists, title has passed or services have been rendered, a price is fixed and determinable, and collection is reasonably assured. The Company may generate revenue from product sales, technology licenses, collaborative research and development arrangements, and research grants. Revenue under technology licenses and collaborative agreements typically consists of nonrefundable and/or guaranteed technology license fees, collaborative research funding and various milestone and future product royalty or profit-sharing payments. Payments under collaborative research and development agreements are recognized as revenue ratably over the relevant periods specified in the agreement, generally the period during which research and development is conducted. Revenue from up-front license fees, milestones and product royalties are recognized as earned based on the completion of the milestones and product sales, as defined in the respective agreements. Payments received in advance of recognition as revenue are recorded as deferred revenue. Allowance for Doubtful Accounts—The Company accrues an allowance for doubtful accounts based on estimates of uncollectible revenues by analyzing historical collections, accounts receivable aging and other factors. Accounts receivable are written off when all collection attempts have failed. Research and Development—Costs and expenses that can be clearly identified as research and development are charged to expense as incurred in accordance with FASB ASC 730-10. Included in research and development costs are operating costs, facilities, supplies, external services, clinical trial and manufacturing costs, overhead directly related to the Company’s research and development operations, and costs to acquire technology licenses. Earnings (Loss) per Share—Basic earnings (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted earnings (loss) per share are computed using the weighted-average number of common shares and dilutive potential common shares outstanding during the period. Dilutive potential common shares primarily consist of stock options and restricted stock units issued to employees and warrants to purchase Common Stock of the Company. All outstanding stock options, restricted stock units and warrants for the three months ended December 31, 2014 and 2013 have been excluded from the calculation of Diluted earnings (loss) per share due to their anti-dilutive effect. Stock-Based Compensation—The Company accounts for share-based compensation arrangements in accordance with FASB ASC 718, which requires the measurement and recognition of compensation expense for all share-based payment awards to be based on estimated fair values. The Company uses the Black-Scholes option valuation model to estimate the fair value of its stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. The Company uses historical data and other information to estimate the expected price volatility and the expected forfeiture rate. Derivative Assets and Liabilities – The Company accounts for warrants and other derivative financial instruments as either equity or assets/liabilities based upon the characteristics and provisions of each instrument. Warrants classified as equity are recorded as additional paid-in capital on the Company’s Consolidated Balance Sheet and no further adjustments to their valuation are made. Some of the Company’s warrants were determined to be ineligible for equity classification because of provisions that may result in an adjustment to their exercise price. Warrants classified as derivative liabilities and other derivative financial instruments that require separate accounting as assets or liabilities are recorded on the Company’s Consolidated Balance Sheet at their fair value on the date of issuance and are revalued on each subsequent balance sheet date until such instruments are exercised or expire, with any changes in the fair value between reporting periods recorded as other income or expense. The Company estimates the fair value of these assets/liabilities using option pricing models that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected volatility, expected life and risk-free interest rate. Income Taxes—The Company accounts for income taxes under the liability method, which requires the recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred income taxes are recognized for the tax consequences in future years of differences between the tax bases of assets and liabilities and their financial reporting amounts at each period end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. Valuation allowances are established, when necessary, to reduce deferred income tax assets to the amount expected to be realized. The provision for income taxes, if any, represents the tax payable for the period and the change in deferred income tax assets and liabilities during the period.

Stockholders' Equity

3 Months Ended

Dec. 31, 2014

Equity [Abstract]

Stockholders' Equity

NOTE 5. STOCKHOLDERS’ EQUITY

At December 31, 2014, the Company had a total of 150,000,000 shares of capital stock authorized for issuance, consisting of 145,000,000 shares of Common Stock, par value $0.001 per share, and 5,000,000 shares of Preferred Stock, par value $0.001 per share.

At December 31, 2014, 54,715,714 shares of Common Stock were outstanding. Additionally, 18,300 shares of Preferred Stock were outstanding, including 2,300 shares of Series B Preferred Stock, convertible into 1,256,831 shares of Common Stock, and 16,000 shares of Series C Preferred Stock, convertible into 2,730,375 shares of Common Stock. At December 31, 2014, 7,274,674 shares of Common Stock were reserved for issuance upon exercise of options and vesting of restricted stock units granted or available for grant under Arrowhead’s 2004 Equity Incentive Plan and 2013 Incentive Plan, as well as for inducement grants made to new employees.

The Preferred Stock is convertible to Common Stock by its holder at its stated conversion price, though it is not convertible to the extent the holder would beneficially own more than 9.99% of the number of shares of outstanding Common Stock immediately after the conversion. The holders of Preferred Stock are eligible to vote with the Common Stock of the Company on an as-converted basis, but only to the extent they are eligible for conversion without exceeding the 9.99% ownership limitation. The Preferred Stock does not carry a coupon, but it is entitled to receive dividends on a pari passu basis with Common Stock, when and if declared. In any liquidation or dissolution of the Company, the holders of Preferred Stock are entitled to participate in the distribution of the assets, to the extent legally available for distribution, on a pari passu basis with the Common Stock.

On October 11, 2013, the Company sold 3,071,672 shares of Common Stock, at a price of $5.86 per share, and 46,000 shares of Series C Preferred Stock, at a price of $1,000 per share. The Preferred Shares are convertible into shares of common stock at a conversion price of $5.86. The aggregate purchase price paid by the purchasers for the Common Stock and Series C Preferred Stock was $64,000,000 and the Company received net proceeds of approximately $60,000,000, after advisory fees and offering expenses.

On February 24, 2014, the Company sold 6,325,000 shares of Common Stock, at a public offering price of $18.95 per share. Net proceeds were approximately $112.6 million after underwriting commissions and discounts and other offering expenses.

The following table summarizes information about warrants outstanding at December 31, 2014:

Exercise prices		Number of Warrants		Remaining Life in Years
$	70.60		94,897		2.4
$	5.00		390,625		0.7
$	5.09		239,534		0.5
$	1.38		24,324		1.0
$	4.16		1,000		2.0
$	3.25		334,347		1.6
$	2.12		75,000		3.0
$	1.83		277,284		3.0
Total warrants outstanding			1,437,011

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Commitments and Contingencies

3 Months Ended

Dec. 31, 2014

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 6. COMMITMENTS AND CONTINGENCIES

Leases

The Company leases office space for its corporate headquarters in Pasadena, California. In March 2014, the Company signed a lease addendum to expand its corporate headquarters, and the new space became available in September 2014. The leases for the expansion space and the current space will expire in September 2019. Rental costs, including the expansion space, are approximately $23,000 per month, increasing approximately 3% annually.

The Company’s research facility in Madison, Wisconsin is leased through February 28, 2019. Monthly rental expense is approximately $25,000. Other monthly rental expenses include common area maintenance and real estate taxes totaling approximately $16,000 per month. Utilities costs are approximately $15,000 per month. Total monthly costs are approximately $75,000 per month, including monthly payments recorded under a capital lease of approximately $19,000.

Facility rent expense for the three months ended December 31, 2014 and 2013 was $171,500 and $145,000, respectively.

As of December 31, 2014, future minimum lease payments due in fiscal years under capitalized leases are as follows:

2015 (remainder of)	$	171,315
2016		228,420
2017		228,420
2018		228,420
2019		95,178
2020 and thereafter		-
Less interest		(32,589	)
Principal		919,164
Less current portion		(213,991	)
Noncurrent portion	$	705,173

As of December 31, 2014, future minimum lease payments due in fiscal years under operating leases are as follows:

2015 (remainder of)	$	436,532
2016		596,877
2017		613,664
2018		637,897
2019		459,633
2020 and thereafter		-
Total	$	2,744,603

Litigation

The Company, its Chief Executive Officer and its Chief Operating Officer have been named as defendants in two securities class actions filed in the United States District Court for the Central District of California regarding certain public statements in connection with the Company’s hepatitis B drug research. Both actions assert claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and seek damages in an unspecified amount. Additionally, three putative stockholder derivative action have been filed in the United States District Court for the Central District of California, alleging breach of fiduciary duty by the Company’s Board of Directors in connection with the facts underlying the Securities Claims. Each of these five suits seek damages in unspecified amounts and some seek various forms of injunctive relief.

The Company and two of its former executives have been named as defendants in a complaint filed by William Marsh Rice University (“Rice University”) currently pending in the United States District Court for the Southern District of Texas relating to alleged breaches of a license agreement between Rice University and the Company’s former subsidiary, Unidym, Inc. The plaintiff has alleged that the Company and its former executives acted fraudulently with respect to Unidym’s license from Rice University and seeks injunctive relief, damages, including unspecified compensatory and punitive damages, and attorneys’ fees.

The Company believes it has a meritorious defense and intends to vigorously defend itself in each of the above matters. The Company makes provisions for liabilities when it is both probable that a liability has been incurred and the amount can be reasonably estimated. No such liability has been recorded related to these matters. The Company does not expect these matters to have any material effect on its Consolidated Financial Statements. With regard to legal fees, such as attorney fees related to these matters or any other legal matters, the Company’s accounting policy is to recognize such cost as incurred.

Purchase Commitments

In the normal course of business, we enter into various purchase commitments for the manufacture of drug components, toxicology studies, and for clinical studies. As of December 31, 2014, these future commitments were approximately $43.1 million, of which approximately $31.6 million is expected to be incurred in the remainder of fiscal 2015, and $11.5 million is expected to be incurred beyond fiscal 2015.

Technology License Commitments

The Company has licensed from third parties the rights to use certain technologies that it uses in its research and development activities, as well as in any products the Company may develop using these licensed technologies. These agreements and other similar agreements often require milestone and royalty payments. Milestone payments, for example, may be required as the research and development process progresses through various stages of development, such as when clinical candidates enter or progress through clinical trials, upon NDA and upon certain sales level milestones. These milestone payments could amount to the mid to upper double digit millions of dollars. In certain agreements, the Company may be required to make mid to high single digit percentage royalty payments based on a percentage of the sales of the relevant products.

Stock-Based Compensation

3 Months Ended

Dec. 31, 2014

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

NOTE 7. STOCK-BASED COMPENSATION

Arrowhead has two plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan and 2013 Incentive Plan, 2,657,352 and 4,000,000 shares, respectively, of Arrowhead’s Common Stock are reserved for the grant of stock options, stock appreciation rights, restricted stock awards and performance unit/share awards by the Board of Directors to employees, consultants and others. As of December 31, 2014, there were options granted and outstanding to purchase 2,561,018 and 1,686,000 shares of Common Stock under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, respectively, and there were 470,000 restricted stock units granted and outstanding under the 2013 Incentive Plan. Also, as of December 31, 2014, there were 617,322 shares reserved for options and restricted stock units issued as inducement grants to new employees outside of equity compensation plans. During the three months ended December 31, 2014, no options were granted under the 2004 Equity Incentive Plan, 864,000 options were granted under the 2013 Incentive Plan, and 120,000 options and 30,000 restricted stock units were granted as inducement awards to new employees outside of equity incentive plans. Additionally, the Company’s 2000 Stock Option Plan and the 38,000 stock options that were outstanding under the 2000 Stock Option Plan expired during the three months ended December 31, 2014.

The following tables summarize information about stock options:

	Number of Options Outstanding		Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
Balance At September 30, 2013		3,419,285	$	4.68
Granted		1,039,000		14.05
Cancelled		(152,582)		6.05
Exercised		(454,863)		6.00
Balance At September 30, 2014		3,850,840		6.99
Granted		984,000		5.45
Cancelled		(38,000)		18.46
Exercised		(2,500)		5.19
Balance At December 31, 2014		4,794,340	$	6.59		8.4 years	$	11,479,110
Exercisable At December 31, 2014		1,860,703	$	5.80		7.3 years	$	5,106,714

Stock-based compensation expense related to stock options for the three months ended December 31, 2014 and 2013 was $981,399 and $521,138, respectively. The Company does not recognize an income tax benefit as the Company is currently operating at a loss and an actual income tax benefit may not be realized. For non-qualified stock options, the loss creates a timing difference, resulting in a deferred tax asset, which is fully reserved by a valuation allowance.

The fair value of the options granted by Arrowhead for the three months ended December 31, 2014 and 2013 is estimated at $3,596,618 and $531,510, respectively.

The intrinsic value of the options exercised during the three months ended December 31, 2014 and 2013 was $23,774 and $314,858, respectively.

As of December 31, 2014, the pre-tax compensation expense for all outstanding unvested stock options in the amount of approximately $13,093,446 will be recognized in our results of operations over a weighted average period of 3.1 years.

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 valuation 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 our stock price on the date of grant, as well as assumptions regarding a number of highly complex and subjective variables. Because the Company’s employee stock options have characteristics significantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models do not necessarily provide a reliable single measure of the fair value of its employee stock options.

The assumptions used to value stock options are as follows:

	Three months ended December 31,
	2014	2013
Dividend yield	—	—
Risk-free interest rate	1.61 – 1.85%	1.90%
Volatility	75%	69%
Expected life (in years)	6.25	6.25
Weighted average grant date fair value per share of options granted	$3.66	$5.06

The dividend yield is zero as the Company currently does not pay a dividend.

The risk-free interest rate is based on the U.S. Treasury bond.

Volatility is estimated based on volatility average of the Company’s Common Stock price.

Restricted Stock Units

Restricted Stock Units (RSUs) were granted under the Company’s 2013 Incentive Plan and inducement grants granted outside of the Plan. During the three months ended December 31, 2014 and 2013, the Company issued 30,000 and 0 restricted stock units, respectively, to certain members of management. Of the restricted stock units granted during the three months ended December 31, 2014, 30,000 were granted outside of the Plan as an inducement grant to a new employee. At vesting each RSU will be exchanged for one share of the Company’s Common Stock. The RSUs issued during the three months ended December 31, 2014 vest in equal annual installments over three years from the date of grant.

The following table summarizes the activity of the Company’s Restricted Stock Units:

	Number of RSUs		Weighted- Average Grant Date Fair Value
Unvested at September 30, 2013		—	$	—
Granted		510,000		14.58
Vested		—		—
Forfeited		—		—
Unvested at September 30, 2014		510,000	$	14.58
Granted		30,000		5.22
Vested		—		—
Forfeited		—		—
Unvested at December 31, 2014		540,000	$	14.06

The Company recorded $1,033,457 and $0 of expense relating to restricted stock units during the three months ended December 31, 2014 and 2013, respectively, and such expense is included in stock-based compensation expense in the Company’s Consolidated Statement of Operations.

As of December 31, 2014, the pre-tax compensation expense for all unvested restricted stock units in the amount of approximately $4,036,658 will be recognized in the Company’s results of operations over a weighted average period of 1.4 years.

Fair Value Measurements

3 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Measurements

NOTE 8. FAIR VALUE MEASUREMENTS

The Company measures its financial assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., exit price) in an orderly transaction between market participants at the measurement date. Additionally, the Company is required to provide disclosure and categorize assets and liabilities measured at fair value into one of three different levels depending on the assumptions (i.e., inputs) used in the valuation. Level 1 provides the most reliable measure of fair value while Level 3 generally requires significant management judgment. Financial assets and liabilities are classified in their entirety based on the lowest level of input significant to the fair value measurement. The fair value hierarchy is defined as follows:

Level 1—Valuations are based on unadjusted quoted prices in active markets for identical assets or liabilities.

Level 2—Valuations are based on quoted prices for similar assets or liabilities in active markets, or quoted prices in markets that are not active for which significant inputs are observable, either directly or indirectly.

Level 3—Valuations are based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. Inputs reflect management’s best estimate of what market participants would use in valuing the asset or liability at the measurement date.

The following table summarizes fair value measurements at December 31, 2014 and September 30, 2014 for assets and liabilities measured at fair value on a recurring basis:

December 31, 2014:

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	103,991,231	$	—	$	—	$	103,991,231
Derivative liabilities	$	—	$	—	$	1,790,559	$	1,790,559
Acquisition-related contingent consideration obligations	$	—	$	—	$	3,970,931	$	3,970,931

September 30, 2014:

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	132,510,610	$	—	$	—	$	132,510,610
Derivative liabilities	$	—	$	—	$	4,173,943	$	4,173,943
Acquisition-related contingent consideration obligations	$	—	$	—	$	3,970,931	$	3,970,931

The Company invests its excess cash balances in short and long-term corporate bonds, generally with remaining maturities of less than two years. At December 31, 2014, the Company had short-term investments of $23,532,402, and long-term investments of $17,806,499, for a total of $41,338,901. The fair value of its investment at December 31, 2014 was $40,759,068. The Company expects to hold such investments until maturity, and thus unrealized gains and losses from the fluctuations in the fair value of the securities are not likely to be realized.

As part of an equity financing in June 2010, Arrowhead issued warrants to acquire up to 329,649 shares of Common Stock (the “2010 Warrants”), of which 24,324 warrants were outstanding at December 31, 2014. Similarly, as part of a financing in December 2012, Arrowhead issued warrants to acquire up to 912,543 shares of Common Stock (the “2012 Warrants”) of which 265,161 warrants were outstanding at December 31, 2014. Further, as part of a financing in January 2013, Arrowhead issued warrants to acquire up to 833,530 shares of Common Stock (the “2013 Warrants”) of which 12,123 warrants were outstanding at December 31, 2014 (collectively the “Warrants”). Each of the Warrants discussed above contains a mechanism to adjust the strike price upon the issuance of certain dilutive equity securities. If during the terms of the Warrants, the Company issues Common Stock at a price lower than the exercise price for the Warrants, the exercise price would be reduced to the amount equal to the issuance price of the Common Stock. As a result of these features, the Warrants are subject to derivative accounting as prescribed under ASC 815. Accordingly, the fair value of the Warrants on the date of issuance was estimated using an option pricing model and recorded on the Company’s Consolidated Balance Sheet as a derivative liability. The fair value of the Warrants is estimated at the end of each reporting period and the change in the fair value of the Warrants is recorded as a non-operating gain or loss as change in value of derivatives in the Company’s Consolidated Statement of Operations. During the three months ended December 31, 2014, the Company recorded a non-cash gain from the change in fair value of the derivative liability of $2,179,651, and during the three months ended December 31, 2013, the Company recorded a non-cash loss of $3,507,496.

The assumptions used in valuing the derivative liability were as follows:

2010 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	0.25%	0.13%
Expected life	1.0 Years	1.2 Years
Dividend yield	None	None
Volatility	75%	69%

2012 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	1.10%	1.07%
Expected life	3.0 Years	3.2 Years
Dividend yield	None	None
Volatility	75%	69%

2013 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	1.10%	1.07%
Expected life	3.1 Years	3.3 Years
Dividend yield	None	None
Volatility	75%	69%

The following is a reconciliation of the derivative liability related to these warrants:

Value at September 30, 2013	$	4,091,797
Issuance of instruments		—
Change in value		5,821,796
Net settlements		(5,956,079	)
Value at September 30, 2014	$	3,957,514
Issuance of instruments		—
Change in value		(2,179,651)
Net settlements		—
Value at December 31, 2014	$	1,777,863

In conjunction with the financing of Ablaris in fiscal 2011, Arrowhead sold exchange rights to certain investors whereby the investors have the right to exchange their shares of Ablaris for a prescribed number of Arrowhead shares of Common Stock based upon a predefined ratio. The exchange rights have a seven-year term. During the first year, the exchange right allows the holder to exchange one Ablaris share for 0.06 Arrowhead shares. This ratio declines to 0.04 in the second year, 0.03 in the third year and 0.02 in the fourth year. In the fifth year and beyond the exchange ratio is 0.01. Exchange rights for 675,000 Ablaris shares were sold in fiscal 2011, and 585,000 remain outstanding at December 31, 2014. The exchange rights are subject to derivative accounting as prescribed under ASC 815. Accordingly, the fair value of the exchange rights on the date of issuance was estimated using an option pricing model and recorded on the Company’s Consolidated Balance Sheet as a derivative liability. The fair value of the exchange rights is estimated at the end of each reporting period and the change in the fair value of the exchange rights is recorded as a non-operating gain or loss in the Company’s Consolidated Statement of Operations. During the three months ended December 31, 2014, the Company recorded a non-cash gain from the change in fair value of the derivative liability of $202,491 and during the three months ended December 31, 2013, the Company recorded a non-cash loss of $12,082.

The assumptions used in valuing the derivative liability were as follows:

	December 31, 2014	September 30, 2014
Risk free interest rate	1.27%	1.07%
Expected life	3.0 Years	3.3 Years
Dividend yield	None	None
Volatility	75%	100%

The following is a reconciliation of the derivative liability related to these exchange rights:

Value at September 30, 2013	$	4,569
Issuance of instruments		—
Change in value		211,860
Net settlements		—
Value at September 30, 2014	$	216,429
Issuance of instruments		—
Change in value		(202,491	)
Net settlements		(1,242)
Value at December 31, 2014	$	12,696

The derivative assets/liabilities are estimated using option pricing models that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected volatility, expected life and risk-free interest rate. Changes in the assumptions used could have a material impact on the resulting fair value. The primary input affecting the value of our derivatives liabilities is the Company’s stock price. Other inputs have a comparatively insignificant effect.

As of December 31, 2014, the Company has a liability for contingent consideration related to its acquisition of Roche Madison Inc. The fair value measurement of the contingent consideration obligations is determined using Level 3 inputs. The fair value of contingent consideration obligations is based on a discounted cash flow model using a probability-weighted income approach. The measurement is based upon unobservable inputs supported by little or no market activity based on the Company’s assumptions and experience. Estimating timing to complete the development and obtain approval of products is difficult, and there are inherent uncertainties in developing a product candidate, such as obtaining U.S. Food and Drug Administration (FDA) and other regulatory approvals. In determining the probability of regulatory approval and commercial success, the Company utilizes data regarding similar milestone events from several sources, including industry studies and its own experience. These fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market. Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions could have a material impact on the amount of contingent consideration expense the Company records in any given period. Changes in the fair value of the contingent consideration obligations are recorded in the Company’s Consolidated Statement of Operations.

The following is a reconciliation of contingent consideration fair value.

Value at September 30, 2013	$	1,595,273
Purchase price contingent consideration		—
Contingent consideration payments		—
Change in fair value of contingent consideration		2,375,658
Value at September 30, 2014	$	3,970,931
Purchase price contingent consideration		—
Contingent consideration payments		—
Change in fair value of contingent consideration		—
Value at December 31, 2014	$	3,970,931

The fair value of contingent consideration obligations is estimated through valuation models designed to estimate the probability of such contingent payments based on various assumptions and incorporating estimated success rates. Estimated payments are discounted using present value techniques to arrive at estimated fair value at the balance sheet date. Changes in the fair value of the contingent consideration obligations can result from changes to one or multiple inputs, including adjustments to the discount rates, changes in the amount or timing of expected expenditures associated with product development, changes in the amount or timing of cash flows from products upon commercialization, changes in the assumed achievement or timing of any development milestones, changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. Each of these assumptions can have a significant impact on the calculation of contingent consideration.

The carrying amounts of the Company’s other financial instruments, which include accounts receivable, accounts payable, and accrued expenses approximate their respective fair values due to the relatively short-term nature of these instruments. The carrying value of the Company’s debt obligations approximates fair value based on market interest rates.

- 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 + Details

Organization and Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Nature of Business	Nature of Business Arrowhead Research Corporation develops novel drugs to treat intractable diseases by silencing the genes that cause them. Using the broadest portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep and durable knockdown of target genes. Arrowhead’s most advanced drug candidate in clinical development is ARC-520, which is designed to treat chronic hepatitis B infection by inhibiting the production of all HBV gene products. The goal is to reverse the immune suppression that prevents the body from controlling the virus and clearing the disease. Arrowhead’s second clinical candidate is ARC-AAT, a treatment for a rare liver disease associated with a genetic disorder that causes alpha-1 antitrypsin deficiency.
Liquidity	Liquidity Historically, the Company’s primary source of financing has been through the sale of securities of Arrowhead. Research and development activities have required significant capital investment since the Company’s inception. We expect our operations to continue to require cash investment in fiscal 2015 and beyond as the Company pursues its research and development goals, as well as clinical trials and related drug manufacturing. At December 31, 2014, the Company had $104.0 million in cash to fund operations. In addition to its cash resources, the Company has invested excess cash in investment grade commercial bonds maturing in less than 24 months. These bonds provide a source of liquidity, though the Company plans to hold them until maturity. At December 31, 2014, the Company had invested $41.3 million in bonds. During the three months ended December 31, 2014, the Company’s cash position decreased by $28.5 million which was primarily the result of cash outflows related to continuing operating activities of $24.2 million, other investing activities of $7.0 million and capital expenditures of $0.5 million. These outflows were partially offset by maturities of fixed income investments totaling $3.1 million and proceeds from the exercise of warrants and options of $0.3 million.
Principles of Consolidation	Principles of Consolidation—The consolidated financial statements include the accounts of Arrowhead and its Subsidiaries. Arrowhead’s primary operating subsidiary is Arrowhead Madison, which is located in Madison, Wisconsin, where the Company’s research and development facility is located. All significant intercompany accounts and transactions are eliminated in consolidation.
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Additionally, certain reclassifications have been made to prior period financial statements to conform to the current period presentation.
Cash and Cash Equivalents	Cash and Cash Equivalents—The Company considers all liquid debt instruments purchased with a maturity of three months or less to be cash equivalents. The Company had no restricted cash at December 31, 2014 and September 30, 2014.
Concentration of Credit Risk	Concentration of Credit Risk—The Company maintains several bank accounts for its operations at two financial institutions. These accounts are insured by the Federal Deposit Insurance Corporation (FDIC) for up to $250,000 per account. Management believes the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which these deposits are held.
Investments	Investments—The Company may invest excess cash balances in short-term and long-term marketable debt securities. Investments may consist of certificates of deposits, money market accounts, government-sponsored enterprise securities, corporate bonds and/or commercial paper. The Company accounts for its investment in marketable securities in accordance with FASB ASC 320, Investments – Debt and Equity Securities. This statement requires certain securities to be classified into three categories: Held-to-maturity—Debt securities that the entity has the positive intent and ability to hold to maturity are reported at amortized cost. Trading Securities—Debt and equity securities that are bought and held primarily for the purpose of selling in the near term are reported at fair value, with unrealized gains and losses included in earnings. Available-for-Sale—Debt and equity securities not classified as either securities held-to-maturity or trading securities are reported at fair value with unrealized gains or losses excluded from earnings and reported as a separate component of shareholders’ equity. The Company classifies its investments in marketable debt securities based on the facts and circumstances present at the time of purchase of the securities. At December 31, 2014, the Company classified all of its investments as held-to-maturity. Held-to-maturity investments are measured and recorded at amortized cost on the Company’s Consolidated Balance Sheet. Discounts and premiums to par value of the debt securities are amortized to interest income/expense over the term of the security. No gains or losses on investment securities are realized until they are sold or a decline in fair value is determined to be other-than-temporary.
Property and Equipment	Property and Equipment—Property and equipment are recorded at cost, which may equal fair market value in the case of property and equipment acquired in conjunction with a business acquisition. Depreciation of property and equipment is recorded using the straight-line method over the respective useful lives of the assets ranging from three to seven years. Leasehold improvements are amortized over the lesser of the expected useful life or the remaining lease term. Long-lived assets, including property and equipment are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.
Intangible Assets subject to amortization	Intangible Assets Subject to Amortization—At December 31, 2014, intangible assets subject to amortization include certain license agreements. Intangible assets subject to amortization are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.
In-Process Research & Development (IPR&D)	In-Process Research & Development (IPR&D)—IPR&D assets represent capitalized on-going research projects that were acquired through business combinations. Such assets are initially measured at their acquisition date fair values. The amounts capitalized are being accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of R&D efforts associated with the project. Upon successful completion of a project, Arrowhead will make a determination as to the then remaining useful life of the intangible asset and begin amortization. Arrowhead tests its indefinite-lived assets for impairment at least annually, through a two-step process. The first step is a qualitative assessment to determine if it is more likely than not that the indefinite lived assets are impaired. Arrowhead considers relevant events and circumstances that could affect the inputs used to determine the fair value of the intangible assets. If the qualitative assessment indicates that it is more likely than not that the intangible assets are impaired, a second step is performed which is a quantitative test to determine the fair value of the intangible asset. If the carrying amount of the intangible assets exceeds its fair value, an impairment loss is recorded in the amount of that excess. If circumstances determine that it is appropriate, the Company may also elect to bypass step one, and proceed directly to the second step.
Contingent Consideration	Contingent Consideration - The consideration for the Company’s acquisitions often includes future payments that are contingent upon the occurrence of a particular event. For example, milestone payments might be based on the achievement of various regulatory approvals or future sales milestones, and royalty payments might be based on drug product sales levels. The Company records a contingent consideration obligation for such contingent payments at fair value on the acquisition date. The Company estimates the fair value of contingent consideration obligations through valuation models designed to estimate the probability of such contingent payments based on various assumptions and incorporating estimated success rates. Estimated payments are discounted using present value techniques to arrive at estimated fair value at the balance sheet date. Changes in the fair value of our contingent consideration obligations are recognized within the Company’s Consolidated Statements of Operations. Changes in the fair value of the contingent consideration obligations can result from changes to one or multiple inputs, including adjustments to the discount rates, changes in the amount or timing of expected expenditures associated with product development, changes in the amount or timing of cash flows from products upon commercialization, changes in the assumed achievement or timing of any development milestones, changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements are based on significant inputs not observable in the market. Substantial judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions could have a material impact on the amount of contingent consideration expense the Company records in any given period.
Revenue Recognition	Revenue Recognition—Revenue from license fees are recorded when persuasive evidence of an arrangement exists, title has passed or services have been rendered, a price is fixed and determinable, and collection is reasonably assured. The Company may generate revenue from product sales, technology licenses, collaborative research and development arrangements, and research grants. Revenue under technology licenses and collaborative agreements typically consists of nonrefundable and/or guaranteed technology license fees, collaborative research funding and various milestone and future product royalty or profit-sharing payments. Payments under collaborative research and development agreements are recognized as revenue ratably over the relevant periods specified in the agreement, generally the period during which research and development is conducted. Revenue from up-front license fees, milestones and product royalties are recognized as earned based on the completion of the milestones and product sales, as defined in the respective agreements. Payments received in advance of recognition as revenue are recorded as deferred revenue.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts—The Company accrues an allowance for doubtful accounts based on estimates of uncollectible revenues by analyzing historical collections, accounts receivable aging and other factors. Accounts receivable are written off when all collection attempts have failed.
Research and Development	Research and Development—Costs and expenses that can be clearly identified as research and development are charged to expense as incurred in accordance with FASB ASC 730-10. Included in research and development costs are operating costs, facilities, supplies, external services, clinical trial and manufacturing costs, overhead directly related to the Company’s research and development operations, and costs to acquire technology licenses.
Earnings (Loss) per Share	Earnings (Loss) per Share—Basic earnings (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted earnings (loss) per share are computed using the weighted-average number of common shares and dilutive potential common shares outstanding during the period. Dilutive potential common shares primarily consist of stock options and restricted stock units issued to employees and warrants to purchase Common Stock of the Company. All outstanding stock options, restricted stock units and warrants for the three months ended December 31, 2014 and 2013 have been excluded from the calculation of Diluted earnings (loss) per share due to their anti-dilutive effect.
Stock-Based Compensation	Stock-Based Compensation—The Company accounts for share-based compensation arrangements in accordance with FASB ASC 718, which requires the measurement and recognition of compensation expense for all share-based payment awards to be based on estimated fair values. The Company uses the Black-Scholes option valuation model to estimate the fair value of its stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. The Company uses historical data and other information to estimate the expected price volatility and the expected forfeiture rate.
Derivative Assets and Liabilities	Derivative Assets and Liabilities – The Company accounts for warrants and other derivative financial instruments as either equity or assets/liabilities based upon the characteristics and provisions of each instrument. Warrants classified as equity are recorded as additional paid-in capital on the Company’s Consolidated Balance Sheet and no further adjustments to their valuation are made. Some of the Company’s warrants were determined to be ineligible for equity classification because of provisions that may result in an adjustment to their exercise price. Warrants classified as derivative liabilities and other derivative financial instruments that require separate accounting as assets or liabilities are recorded on the Company’s Consolidated Balance Sheet at their fair value on the date of issuance and are revalued on each subsequent balance sheet date until such instruments are exercised or expire, with any changes in the fair value between reporting periods recorded as other income or expense. The Company estimates the fair value of these assets/liabilities using option pricing models that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected volatility, expected life and risk-free interest rate.
Income Taxes	Income Taxes—The Company accounts for income taxes under the liability method, which requires the recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred income taxes are recognized for the tax consequences in future years of differences between the tax bases of assets and liabilities and their financial reporting amounts at each period end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. Valuation allowances are established, when necessary, to reduce deferred income tax assets to the amount expected to be realized. The provision for income taxes, if any, represents the tax payable for the period and the change in deferred income tax assets and liabilities during the period.

Investments (Tables)

3 Months Ended

Dec. 31, 2014

Equity [Abstract]

Summary of Short and Long-term Investments

The following tables summarize the Company’s short and long-term investments as of December 31, 2014, and September 30, 2014.

	As of December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial notes (due within one year)	$	23,532,402	$	—	$	(313,407	)	$	23,218,995
Commercial notes (due after one year through two years)	$	17,806,499		—	$	(266,426	)	$	17,540,073
Total	$	41,338,901	$	—	$	(579,833	)	$	40,759,068

	As of September 30, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial notes (due within one year)	$	21,653,032	$	—	$	(189,830	)	$	21,463,202
Commercial notes (due after one year through two years)	$	23,088,346		—	$	(217,693	)	$	22,870,653
Total	$	44,741,378	$	—	$	(407,523	)	$	44,333,855

- Definition

Tabular disclosure of all investments in certain debt and equity securities for which the entity has the positive intent and ability to hold until maturity.

+ References + Details

Stock-Based Compensation (Tables)

3 Months Ended

Dec. 31, 2014

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summarize Information about Stock Options

The following tables summarize information about stock options:

	Number of Options Outstanding		Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
Balance At September 30, 2013		3,419,285	$	4.68
Granted		1,039,000		14.05
Cancelled		(152,582)		6.05
Exercised		(454,863)		6.00
Balance At September 30, 2014		3,850,840		6.99
Granted		984,000		5.45
Cancelled		(38,000)		18.46
Exercised		(2,500)		5.19
Balance At December 31, 2014		4,794,340	$	6.59		8.4 years	$	11,479,110
Exercisable At December 31, 2014		1,860,703	$	5.80		7.3 years	$	5,106,714

Assumptions Used to Value Stock Options

The assumptions used to value stock options are as follows:

	Three months ended December 31,
	2014	2013
Dividend yield	—	—
Risk-free interest rate	1.61 – 1.85%	1.90%
Volatility	75%	69%
Expected life (in years)	6.25	6.25
Weighted average grant date fair value per share of options granted	$3.66	$5.06

Summary of Share Activity Related to Restricted Stock Units

The following table summarizes the activity of the Company’s Restricted Stock Units:

	Number of RSUs		Weighted- Average Grant Date Fair Value
Unvested at September 30, 2013		—	$	—
Granted		510,000		14.58
Vested		—		—
Forfeited		—		—
Unvested at September 30, 2014		510,000	$	14.58
Granted		30,000		5.22
Vested		—		—
Forfeited		—		—
Unvested at December 31, 2014		540,000	$	14.06

Fair Value Measurements (Tables)

3 Months Ended

Dec. 31, 2014

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

The following table summarizes fair value measurements at December 31, 2014 and September 30, 2014 for assets and liabilities measured at fair value on a recurring basis:

December 31, 2014:

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	103,991,231	$	—	$	—	$	103,991,231
Derivative liabilities	$	—	$	—	$	1,790,559	$	1,790,559
Acquisition-related contingent consideration obligations	$	—	$	—	$	3,970,931	$	3,970,931

September 30, 2014:

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	132,510,610	$	—	$	—	$	132,510,610
Derivative liabilities	$	—	$	—	$	4,173,943	$	4,173,943
Acquisition-related contingent consideration obligations	$	—	$	—	$	3,970,931	$	3,970,931

Change in Fair Value of Contingent Consideration Obligations

The following is a reconciliation of contingent consideration fair value.

Value at September 30, 2013	$	1,595,273
Purchase price contingent consideration		—
Contingent consideration payments		—
Change in fair value of contingent consideration		2,375,658
Value at September 30, 2014	$	3,970,931
Purchase price contingent consideration		—
Contingent consideration payments		—
Change in fair value of contingent consideration		—
Value at December 31, 2014	$	3,970,931

Exchange rights

Assumptions Used in Valuing Derivative Liabilities

The assumptions used in valuing the derivative liability were as follows:

	December 31, 2014	September 30, 2014
Risk free interest rate	1.27%	1.07%
Expected life	3.0 Years	3.3 Years
Dividend yield	None	None
Volatility	75%	100%

Reconciliation of Derivative Liability

The following is a reconciliation of the derivative liability related to these exchange rights:

Value at September 30, 2013	$	4,569
Issuance of instruments		—
Change in value		211,860
Net settlements		—
Value at September 30, 2014	$	216,429
Issuance of instruments		—
Change in value		(202,491	)
Net settlements		(1,242)
Value at December 31, 2014	$	12,696

Warrant

Assumptions Used in Valuing Derivative Liabilities

The assumptions used in valuing the derivative liability were as follows:

2010 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	0.25%	0.13%
Expected life	1.0 Years	1.2 Years
Dividend yield	None	None
Volatility	75%	69%

2012 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	1.10%	1.07%
Expected life	3.0 Years	3.2 Years
Dividend yield	None	None
Volatility	75%	69%

2013 Warrants	December 31, 2014	September 30, 2014
Risk free interest rate	1.10%	1.07%
Expected life	3.1 Years	3.3 Years
Dividend yield	None	None
Volatility	75%	69%

Reconciliation of Derivative Liability

The following is a reconciliation of the derivative liability related to these warrants:

Value at September 30, 2013	$	4,091,797
Issuance of instruments		—
Change in value		5,821,796
Net settlements		(5,956,079	)
Value at September 30, 2014	$	3,957,514
Issuance of instruments		—
Change in value		(2,179,651)
Net settlements		—
Value at December 31, 2014	$	1,777,863

Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule Of Investments [Line Items]
Cash to fund operations	$ 103,991,231	$ 59,713,424	$ 132,510,610	$ 19,114,444
Investments	41,338,901		44,741,378
Net increase (decrease) in cash	(28,519,379)	40,598,980
Cash outflow related to continuing operating activities	(24,200,006)	(7,022,332)
Other investing activities	(7,000,000)
Capital expenditures	554,945	116,215
Net cash invested in fixed income investments	3,100,000
Proceeds from the exercise of warrants and stock options	283,466
Restricted Cash	0		$ 0
Amount insured in FDIC per account	$ 250,000
Minimum
Schedule Of Investments [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum
Schedule Of Investments [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Commercial bonds
Schedule Of Investments [Line Items]
Maturity description	less than 24 months
Investments	$ 41,300,000

Stockholders' Equity - Additional Information (Detail) - USD ($)	Feb. 24, 2014	Oct. 11, 2013	Dec. 31, 2014	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Capital stock authorized for issuance			150,000,000
Common stock, shares authorized			145,000,000	145,000,000
Common stock, par value			$ 0.001	$ 0.001
Preferred stock, shares authorized			5,000,000	5,000,000
Preferred stock, par value			$ 0.001	$ 0.001
Common stock, shares outstanding			54,715,714	54,656,936
Preferred stock, shares outstanding			18,300	18,300
Threshold percentage of common stock ownership upon preferred stock conversion			9.99%
Stock issuances, Shares	6,325,000	3,071,672
Sale of stock, price per share	$ 18.95	$ 5.86
Conversion price		$ 5.86
Proceeds from issuance of common stock and warrants, net	$ 112,600,000	$ 60,000,000
Series B convertible preferred stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock equivalent of preferred stock			1,256,831
Preferred stock, shares outstanding			2,300
Series C Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock equivalent of preferred stock			2,730,375
Preferred stock, shares outstanding			16,000
Stock issuances, Shares		46,000
Sale of stock, price per share		$ 1,000
Aggregate price on issuance or Sale of equity		$ 64,000,000
2004 Equity Incentive Plan, 2013 Equity Incentive Plan, and Inducement Grants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, Share reserve for issuance			7,274,674

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014	Oct. 01, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options Outstanding, Granted	984,000		1,039,000
Number of Options Outstanding	4,794,340		3,850,840	3,419,285
Stock options outstanding expired	38,000		152,582
Share-based compensation, description	At vesting each RSU will be exchanged for one share of the Company’s Common Stock. The RSUs issued during the three months ended December 31, 2014 vest in equal annual installments over three years from the date of grant.
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 981,399	$ 521,138
Fair value of the options granted	3,596,618	531,510
Intrinsic value of options exercised	23,774	314,858
Unrecognized pre-tax compensation expense	$ 13,093,446
Weighted average period to recognize pre-tax compensation expense	3 years 1 month 6 days
Dividend yield	0.00%
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding, granted	30,000		510,000
Stock-based compensation expense	$ 1,033,457	$ 0
Weighted average period to recognize pre-tax compensation expense	1 year 4 months 24 days
Unrecognized pre-tax compensation expense	$ 4,036,658
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	2,657,352
Number of Options Outstanding, Granted	0
2004 Equity Incentive Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options Outstanding	2,561,018
2013 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	4,000,000
Number of Options Outstanding, Granted	864,000
2013 Incentive Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options Outstanding	1,686,000
2013 Incentive Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding, granted	470,000	30,000
Number of restricted stock units outstanding	470,000
Outside Of Equity Compensation Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	617,322
Outside Of Equity Compensation Plans \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units granted outside of Equity Incentive plans	120,000
Outside Of Equity Compensation Plans \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units granted outside of Equity Incentive plans	30,000
2000 Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options outstanding expired	38,000

Stock-Based Compensation - Summarize Information about Stock Options (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options Outstanding, beginning balance	3,850,840
Number of Options Outstanding, Granted	984,000	1,039,000
Number of Options Outstanding, Cancelled	(38,000)	(152,582)
Number of Options Outstanding, Exercised	(2,500)	(454,863)
Number of Options Outstanding, ending balance	4,794,340	3,850,840
Number of Options Outstanding, Exercisable	1,860,703
Weighted Average Exercise Price Per Share, beginning balance	$ 6.99
Weighted Average Exercise Price Per Share, Granted	5.45	$ 14.05
Weighted Average Exercise Price Per Share, Cancelled	18.46	6.05
Weighted Average Exercise Price Per Share, Exercised	5.19	6.00
Weighted Average Exercise Price Per Share, ending balance	6.59	$ 6.99
Weighted Average Exercise Price Per Share, Exercisable	$ 5.80
Weighted Average Remaining Contractual Term	8 years 4 months 24 days
Weighted Average Remaining Contractual Term, Exercisable	7 years 3 months 18 days
Aggregate Intrinsic Value	$ 11,479,110
Aggregate Intrinsic Value, Exercisable	$ 5,106,714

Fair Value Measurements - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Sep. 30, 2014 USD ($)	Jan. 31, 2013 shares	Dec. 31, 2012 shares	Jun. 30, 2010 shares
Fair Value Measurements Disclosure [Line Items]
Short term investments \| $	$ 23,532,402		$ 21,653,032
Investments \| $	17,806,499		23,088,346
Total investments \| $	41,338,901		44,741,378
Fair value of investment \| $	$ 40,759,068		$ 44,333,855
Warrants outstanding	1,437,011
Non-cash gain (loss) from change in fair value of the derivative liability \| $	$ 2,179,651	$ (3,507,496)
Duration of exchange rights	7 years
Ablaris Therapeutics
Fair Value Measurements Disclosure [Line Items]
Warrants outstanding	585,000
Non-cash gain (loss) from change in fair value of the derivative liability \| $	$ 202,491	$ (12,082)
Exchange right convertible conversion ratio for first year	0.06
Exchange right convertible conversion ratio for second year	0.04
Exchange right convertible conversion ratio for third year	0.03
Exchange right convertible conversion ratio for fourth year	0.02
Exchange right convertible conversion ratio for fifth year and beyond	0.01
Number of exchange right sold	675,000
2010 Warrants
Fair Value Measurements Disclosure [Line Items]
Warrants issued to acquire Common Stock						329,649
Warrants outstanding	24,324
2012 Warrants
Fair Value Measurements Disclosure [Line Items]
Warrants issued to acquire Common Stock					912,543
Warrants outstanding	265,161
2013 Warrants
Fair Value Measurements Disclosure [Line Items]
Warrants issued to acquire Common Stock				833,530
Warrants outstanding	12,123

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($)	Dec. 31, 2014	Sep. 30, 2014
Property Plant And Equipment [Abstract]
Computers, office equipment and furniture	$ 374,535	$ 334,162
Research equipment	5,010,151	4,614,176
Software	69,623	69,623
Leasehold improvements	3,117,537	3,045,022
Total gross fixed assets	8,571,846	8,062,983
Less: Accumulated depreciation and amortization	(4,447,405)	(4,190,230)
Property and equipment, net	$ 4,124,441	$ 3,872,753

Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014
Expected Amortization Expense [Line Items]
Finite-lived intangible assets, accumulated amortization	$ 175,100
Amortization expense	13,664	$ 13,664	$ 54,653
Amortization of license agreements in 2015	41,900
Amortization of license agreements in 2016	13,000
Amortization of license agreements, thereafter	$ 0
Licensing Agreements
Expected Amortization Expense [Line Items]
Amortization period of intangible assets	4 years

Intangible Assets - Schedule of Intangible Asset (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible assets not subject to amortization, beginning balance	$ 944,935	$ 3,117,322	$ 3,117,322
Intangible assets not subject to amortization, Impairment			(2,172,387)
Intangible assets not subject to amortization, ending balance	944,935		944,935
Intangible assets subject to amortization, beginning balance	68,538	123,191	123,191
Intangible assets subject to amortization, Amortization	(13,664)	(13,664)	(54,653)
Intangible assets subject to amortization, ending balance	54,874		68,538
Total Intangible assets, beginning balance	1,013,473	$ 3,240,513	3,240,513
Total Intangible assets, Impairment			(2,172,387)
Total Intangible assets, ending balance	$ 999,809		$ 1,013,473

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Other Commitments [Line Items]
Facility and equipment rent expense	$ 171,500	$ 145,000
Provision for recorded liabilities	0
Future commitments	43,100,000
Commitments expected to be incurred in fiscal 2015	31,600,000
Commitments expected to be incurred beyond fiscal 2015	11,500,000
Corporate Headquarters In Pasadena
Other Commitments [Line Items]
Rental expense	$ 23,000
Operating lease expiration date	Sep. 30, 2019
Percentage of increase in annual rental cost	3.00%
Research Facility in Madison
Other Commitments [Line Items]
Rental expense	$ 25,000
Operating lease expiration date	Feb. 28, 2019
Other rental expenses including common area maintenance and real estate taxes	$ 16,000
Utilities costs per month	15,000
Increase in total monthly expenditures	75,000
Research Facility in Madison \| Assets Held under Capital Leases
Other Commitments [Line Items]
Monthly payments under capital lease	$ 19,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2014	Sep. 30, 2014
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	18,300	18,300
Preferred stock, shares outstanding	18,300	18,300
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	54,715,714	54,656,936
Common stock, shares outstanding	54,715,714	54,656,936

Consolidated Statement of Stockholders' Equity (unaudited) (Parenthetical)	Sep. 30, 2014 $ / shares
Common stock issued @ $5.86
Common stock issued, price per share	$ 5.86
Common stock issued @ $18.95
Common stock issued, price per share	18.95
Preferred stock issued at $1,000 per share
Common stock issued, price per share	$ 1,000

Investments - Summary of Short and Long-term Investments (Detail) - USD ($)	Dec. 31, 2014	Sep. 30, 2014
Schedule Of Investments [Line Items]
Gross Unrealized Losses	$ (579,833)	$ (407,523)
Fair Value	40,759,068	44,333,855
Commercial notes (due within one year), amortized cost	23,532,402	21,653,032
Commercial notes (due after one year through two years), amortized cost	17,806,499	23,088,346
Total	41,338,901	44,741,378
Commercial Notes Due Within One Year
Schedule Of Investments [Line Items]
Gross Unrealized Losses	(313,407)	(189,830)
Fair Value	23,218,995	21,463,202
Commercial Notes Due After One Year Through Two Years
Schedule Of Investments [Line Items]
Gross Unrealized Losses	(266,426)	(217,693)
Fair Value	$ 17,540,073	$ 22,870,653

Stockholders' Equity - Summary of Information About Warrants (Detail)	3 Months Ended
	Dec. 31, 2014 $ / shares shares
Class Of Warrant Or Right [Line Items]
Warrants outstanding	1,437,011
Warrant 1
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 70.60
Warrants outstanding	94,897
Remaining Life in Years	2 years 4 months 24 days
Warrant 2
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 5.00
Warrants outstanding	390,625
Remaining Life in Years	8 months 12 days
Warrant 3
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 5.09
Warrants outstanding	239,534
Remaining Life in Years	6 months
Warrant 4
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 1.38
Warrants outstanding	24,324
Remaining Life in Years	1 year
Warrant 5
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 4.16
Warrants outstanding	1,000
Remaining Life in Years	2 years
Warrant 6
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 3.25
Warrants outstanding	334,347
Remaining Life in Years	1 year 7 months 6 days
Warrant 7
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 2.12
Warrants outstanding	75,000
Remaining Life in Years	3 years
Warrant 8
Class Of Warrant Or Right [Line Items]
Exercise prices \| $ / shares	$ 1.83
Warrants outstanding	277,284
Remaining Life in Years	3 years

Commitments and Contingencies - Future Minimum Lease Payments Under Capitalized Leases (Detail) - USD ($)	Dec. 31, 2014	Sep. 30, 2014
Leases [Abstract]
2015 (remainder of)	$ 171,315
2016	228,420
2017	228,420
2018	228,420
2019	95,178
Less interest	(32,589)
Principal	919,164
Less current portion	(213,991)	$ (213,991)
Noncurrent portion	$ 705,173	$ 758,340

Commitments and Contingencies - Future Minimum Lease Payments Under Operating Leases (Detail)	Dec. 31, 2014 USD ($)
Leases [Abstract]
2015 (remainder of)	$ 436,532
2016	596,877
2017	613,664
2018	637,897
2019	459,633
Total	$ 2,744,603

Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liabilities	$ 1,790,559	$ 4,173,943
Acquisition-related contingent consideration obligations	3,970,931	3,970,931	$ 1,595,273
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	103,991,231	132,510,610
Derivative liabilities	1,790,559	4,173,943
Acquisition-related contingent consideration obligations	3,970,931	3,970,931
Fair Value, Measurements, Recurring \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	103,991,231	132,510,610
Fair Value, Measurements, Recurring \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liabilities	1,790,559	4,173,943
Acquisition-related contingent consideration obligations	$ 3,970,931	$ 3,970,931

Fair Value Measurements - Change in Fair Value of Contingent Consideration Obligations (Detail)	12 Months Ended
	Sep. 30, 2014 USD ($)
Business Combinations [Abstract]
Contingent consideration obligations, Beginning balance	$ 1,595,273
Change in fair value of contingent consideration	2,375,658
Contingent consideration obligations, Ending balance	$ 3,970,931