Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Musket David B
   2. Issuer Name and Ticker or Trading Symbol
AEROGEN INC [AEGN] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
125 CAMBRIDGEPARK DRIVE, 		 3. Date of Earliest Transaction (Month/Day/Year)
04/21/2005
(Street)

CAMBRIDGE, MA 02140		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
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 04/21/2005   P   33,000 A $ 0.875 766,972 I See Footnotes (1) (2)

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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 Underlying Securities
(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 of Derivative Security: 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

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Musket David B
125 CAMBRIDGEPARK DRIVE
CAMBRIDGE, MA 02140		     X    
KUROKAWA BARRY
C/O PROMED PARTNERS, L.P.
125 CAMBRIDGEPARK DRIVE
CAMBRIDGE, MA 02140		       Joint Filer
PROMED ASSET MANAGEMENT, LLC
125 CAMBRIDGEPARK DRIVE
CAMBRIDGE, MA 02140		       Joint Filer
PROMED PARTNERS L P
125 CAMBRIDGEPARK DR
CAMBRIDGE, MA 02104		       Joint Filer
PROMED PARTNERS II LP
125 CAMBRIDGEPARK DR
CAMBRIDGE, MA 02104		       Joint Filer
PROMED MANAGEMENT INC
125 CAMBRIDGEPARK DR
CAMBRIDGE, MA 02104		       Joint Filer
PROMED OFFSHORE FUND, LTD
125 CAMBRIDGEPARK DRIVE
CAMBRIDGE, MA 02140		       Joint Filer
PROMED OFFSHORE FUND II, LTD
125 CAMBRIDGEPARK DRIVE
CAMBRIDGE, MA 02140		       Joint Filer

Signatures

 David B. Musket   05/19/2005
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(1) The reported purchase of 25,000 shares of the Issuer was made on behalf of the account of ProMed Offshore II Fund, Ltd., a private investment fund (which as of the date of this Form 4, owns 58,000 shares of the Issuer), the Investment Manager of which is ProMed Management, Inc. ("ProMed Management"). ProMed Management is controlled by David B. Musket and Barry Kurokawa. The remainder of the reported amount of securities beneficially owned following the reported transaction may be deemed to be beneficially owned as follows: (A) 455,480 shares of the Issuer owned by and held in the account of ProMed Partners, L.P., whose general partner is ProMed Asset Management, L.L.C. ("ProMed Asset Management"), which is controlled by David B. Musket and Barry Kurokawa; See Footnote 2.
(2) (B) 83,986 shares of the Issuer owned by and held in the account of ProMed Partners II, L.P., whose general partner is also ProMed Asset Management; (C) 73,564 shares of the Issuer owned by and held in the account of ProMed Offshore Fund, Ltd., whose investment manager is ProMed Management; (D) 120,942 shares of the Issuer owned directly by David B. Musket; and (E) 1,533 shares of the Issuer owned directly by Barry Kurokawa. Each Reporting Person disclaims beneficial ownership of the reported securities except to the extent of his or its pecuniary interest therein, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

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