SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
X	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* KNOTT DAVID M (Last) (First) (Middle) 485 UNDERHILL BLVD STE 205 (Street) SYOSSET NY 11791-3419 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol ARROWHEAD RESEARCH CORP [ ARWR ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 03/21/2007
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/21/2007		S		24,200	D	$3.8084	728,600	I	By Shoshone Partners, L.P.(1)(3)
Common Stock								4,300	I	By Mulsanne Partners, L.P.(1)(3)
Common Stock	03/21/2007		S		49,400	D	$3.8084	1,764,231	I	By Knott Partners Offshore Master Fund, L.P.(1)(3)
Common Stock	03/21/2007		S		7,800	D	$3.8084	241,578	I	By Managed Accounts(2)(3)
Common Stock	03/21/2007		S		52,300	D	$3.8084	1,241,800	I	By Knott Partners, L.P.(1)(3)
Common Stock	03/21/2007		S		21,200	D	$3.8197	707,400	I	By Shoshone Partners, L.P.(1)(3)
Common Stock	03/21/2007		S		43,450	D	$3.8197	1,720,781	I	By Knott Partners Offshore Master Fund, L.P.(1)(3)
Common Stock	03/21/2007		S		6,800	D	$3.8197	234,778	I	By Managed Accounts(2)(3)
Common Stock	03/21/2007		S		45,800	D	$3.8197	1,196,000	I	By Knott Partners, L.P.(1)(3)
Common Stock	03/21/2007		S		210,100	D	$3.8	497,300	I	By Shoshone Partners, L.P.(1)(3)
Common Stock	03/21/2007		S		428,500	D	$3.8	1,292,281	I	By Knott Partners Offshore Master Fund, L.P.(1)(3)
Common Stock	03/21/2007		S		68,000	D	$3.8	166,778	I	By Managed Accounts(2)(3)
Common Stock	03/21/2007		S		453,400	D	$3.8	742,600	I	By Knott Partners, L.P.(1)(3)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The Reporting Person is the managing member of Knott Partners Management, LLC, which is (i) the sole general partner of Shoshone Partners, L.P., Knott Partners Offshore Master Fund, L.P. and Mulsanne Partners, L.P., and (ii) the managing general partner of Knott Partners, L.P. The Reporting Person is also a general partner of Knott Partners, L.P.

2. The entry represents securities of the issuer held by managed accounts for which Dorset Management Corporation provides investment management services (the "Managed Accounts").

3. As a result of the Reporting Person's interests in Knott Partners Management, LLC and in Dorset Management Corporation, the Reporting Person has investment discretion and control of the securities represented in this entry. The Reporting Person may be deemed to beneficially own an indirect pecuniary interest in the securities represented in this entry as a result of its performance-related fee. Except with respect to Shoshone Partners, L.P. and Knott Partners, L.P., in which the Reporting Person owns a beneficial interest, the Reporting Person disclaims beneficial ownership therein except to the extent ultimately realized. Each of Shoshone Partners, L.P., Mulsanne Partners, L.P., Knott Partners Offshore Master Fund, L.P., Knott Partners, L.P. and the Managed Accounts disclaims beneficial ownership of securities reported as owned by any other party.

	/s/ David M. Knott	03/22/2007
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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