Exhibit 10.12.1

FIRST AMENDMENT

THIS FIRST AMENDMENT(this "Amendment") is made and entered into as of November 6, 2003, by and between CA-SHORELINE TECHNOLOGY PARK LIMITED PARTNERSHIP,a Delaware limited partnership("Landlord"), andAEROGEN, INC., a Delaware corporation("Tenant").

RECITALS

NOW, THEREFORE, in consideration of the mutual covenants and agreements herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, Landlord and Tenant agree as follows.

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|Period
of Lease Term |  | Total Monthly
Base Rent
Payable
Under
Lease* |            | Monthly
Reduced
Base Rent
Payment* |   | Monthly
Deferred
Base Rent |  | Monthly
Base Rent
Differential* |            | Monthly
LC
Offset
|-------------------- |  | -------------------------------------------- | ---------- | ---------------------------------- | - | -------------------------- |  | ------------------------------- | ---------- | -----------------
|07/01/03 - 12/31/03  |  | $                                            | 197,902.44 |                                    | $ | 100,000.00                 |  | $                               | 97,902.44  |                  
|01/01/04 - 02/10/04  |  | $                                            | 197,902.44 |                                    | $ | 100,000.00                 |  | $                               | 97,902.44  |                  
|02/11/04 - 12/31/04  |  | $                                            | 204,346.80 |                                    | $ | 100,000.00                 |  | $                               | 104,346.80 |                  
|1/01/05 - 02/10/05   |  | $                                            | 204,346.80 |                                    | $ | 100,000.00                 |  | $                               | 104,346.80 |                  
|02/11/05 - 06/30/05  |  | $                                            | 210,956.40 |                                    | $ | 100,000.00                 |  | $                               | 110,956.40 |                  

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| |  | "Landlord                                       
| |  | ------------------------------------------------
| |  | Ca-Shoreline Technology Park Limited Partnership
| |  | 1740 Technology Drive, Suite 150                
| |  | San Jose, California 95110                      
| |  | Attention:                                      
| |  |                                                 



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[SIGNATURES ARE ON FOLLOWING PAGE]

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IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Amendment as of the day and year first above written.

| |  | LANDLORD:                                                                       
| |  | --------------------------------------------------------------------------------
| |  | CA-SHORELINE TECHNOLOGY PARK LIMITED PARTNERSHIP, a Delaware limited partnership
| |  | By:                                                                             
| |  |                                                                                 
| |  |                                                                                 
| |  |                                                                                 
| |  |                                                                                 
| |  | TENANT                                                                          
| |  | AEROGEN, INC., a Delaware corporation                                           
| |  | By:                                                                             
| |  | Name:                                                                           
| |  | Title:                                                                          
| |  | 33-0488580Tenant's Tax ID Number (SSN or FEIN)                                  

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EXHIBIT AOUTLINE AND LOCATION OF HOLDOVER SPACE

MAP

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EXHIBIT BINVESTMENT REPRESENTATION LETTER

Aerogen. Inc.
2071 Stierlin Court
Mountain View, CA 94043-4655

Ladies
and Gentlemen:

The
undersigned hereby makes the following certifications and representations with respect to the Three Hundred Thousand (300,000) shares (the "Shares") of Common Stock of Aerogen, Inc., a Delaware
corporation (the "Company"), which are being acquired by the undersigned pursuant to the First Amendment dated October
    , 2003 but effective as of July 1, 2003 to the Lease Agreement dated as of October 1, 2001.

The
undersigned is an "accredited investor," as that term is defined in Regulation D of the Securities Act of 1933, as amended (the "Securities Act").

The
undersigned represents and warrants that the undersigned is acquiring the Shares solely for the undersigned's account for investment and not with a view to or for sale or
distribution of the Shares or any part thereof. The undersigned also represents that the entire legal and beneficial interests of the Shares the undersigned is acquiring is being acquired for, and
will be held for, the undersigned's account only.

The
undersigned understands that the Shares have not been registered under the Securities Act of 1933, as amended (the "Securities Act"), on the basis that no distribution or public
offering of the
Shares is to be effected. The undersigned realizes that the basis for the exemption may not be present if, notwithstanding the undersigned's representations, the undersigned has in mind merely
acquiring the Shares for a fixed or determinable period in the future, or for a market rise, or for sale if the market does not rise. The undersigned has no such intention.

The
undersigned recognizes that the Shares being acquired by the undersigned must be held indefinitely unless they are subsequently registered under the Securities Act or an exemption
from such registration is available.

The
undersigned is aware that the Shares may not be sold pursuant to Rule 144 adopted under the Securities Act ("Rule 144") unless certain conditions are met and until the
undersigned has held the Shares for at least one year. Among the conditions for use of the Rule is the availability of current information to the public about the Company.

The
undersigned further agrees not to make any disposition of all or any part of the Shares being acquired in any event unless and until:



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The
undersigned understands and agrees that all certificates evidencing the Shares to be issued to the undersigned may bear the following legend:



|Very truly yours,                               
|------------------------------------------------
|CA-SHORELINE TECHNOLOGY PARK LIMITED PARTNERSHIP
|                                                
|                                                
|                                                
|                                                
|                                                

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EXHIBIT CCapitalization of the Tenant

As
of September 30, 2003:

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EXHIBIT DTerms of the Registration of Common Stock

1.Expenses.Tenant will pay all expenses associated with the Registration Statement, including up to $5,000 of
the fees and disbursements of Bryan Cave LLP as special counsel for SF Capital.

2.Indemnification.Tenant will indemnify and hold harmless Landlord, its directors, officers, agents and
employees, each Person who controls the Landlord (within the meaning of Section 15 of the Securities Act and Section 20 of the Exchange Act), and the directors, officers, agents or
employees of such controlling Persons, to the fullest extent permitted by applicable law, from and against any and all losses, claims, damages, liabilities, costs (including, without limitation,
reasonable costs of preparation and reasonable attorneys' fees) and expenses (collectively, "Losses"), as incurred, arising out of or relating to any untrue or alleged untrue statement of a material
fact contained in the Registration Statement, any Prospectus or any form of prospectus or in any amendment or supplement thereto or in any preliminary prospectus, or arising out of or relating to any
omission or alleged omission of a material fact required to be stated therein or necessary to make the statements therein (in the case of any Prospectus or form of prospectus or supplement thereto, in
light of the circumstances under which they were made) not misleading, except to the extent, but only to the extent, that (1) such untrue statements or omissions are based solely upon
information regarding Landlord furnished in writing to Tenant by Landlord expressly for use therein, or to the extent that such information relates to Landlord or Landlord's proposed method of
distribution of Registrable Securities and was reviewed and expressly approved in writing by Landlord expressly for use in the Registration Statement, such Prospectus or such form of Prospectus or in
any amendment or supplement thereto (it being understood that Landlord has approved Annex A hereto for this purpose) or (2) the use by Landlord of an outdated or defective Prospectus after
Tenant has notified Landlord in writing that the Prospectus is outdated or defective and prior to the receipt by Landlord of a written advice that use of the Prospectus may be resumed (an "Advice") or
an amended or supplemented Prospectus, but only if and to the extent that following the receipt of the Advice or amended or supplemented Prospectus the misstatement or omission giving rise to such
Loss would have been corrected.

Landlord
will indemnify and hold harmless Tenant, its directors, officers, agents and employees, each Person who controls Tenant (within the meaning of Section 15 of the
Securities Act and Section 20 of the Exchange Act), and the directors, officers, agents or employees of such controlling Persons, to the fullest extent permitted by applicable law, from and
against all Losses, as incurred, arising solely out of or based solely upon: (x) Landlord's failure to comply with the prospectus delivery requirements of the Securities Act or (y) any
untrue statement of a material fact contained in any Registration Statement, any prospectus, or any form of prospectus, or in any amendment or supplement thereto, or arising solely out of or based
solely upon any omission of a material fact required to be stated therein or necessary to make the statements therein not misleading to the extent, but only to the extent that, (1) such untrue
statements or omissions are based solely upon information regarding Landlord furnished in writing to Tenant by Landlord expressly for use therein, or to the extent that such information relates to
Landlord or Landlord's proposed method of distribution of Registrable Securities and was reviewed and expressly approved in writing by Landlord expressly for use in the Registration Statement (it
being understood that Landlord has approved Annex A hereto for this purpose), such Prospectus or such form of Prospectus or in any amendment or supplement thereto or (2) the use by Landlord of
an outdated or defective Prospectus after Tenant has notified Landlord in writing that the Prospectus is outdated or defective and prior to the receipt by Landlord of an Advice or an amended or
supplemented Prospectus, but only if and to the extent that following the receipt of the Advice or the amended or supplemented Prospectus the misstatement or omission giving rise to such Loss would
have been corrected. In no event shall the liability of Landlord be greater in amount

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than
the dollar amount of the net proceeds received by Landlord upon the sale of the Registrable Securities giving rise to such indemnification obligation.

3.Registration.The Registration Statement will be on Form S-3 (except if Tenant is not
S-3 eligible, in which case the Registration Statement will be on another appropriate form) and shall contain (except if otherwise required by the Commission or directed by SF Capital) the
"Plan of Distribution" attached hereto asAnnex A. The Tenant shall use its best efforts to keep such
Registration Statement continuously effective under the Securities Act until the date which is two years after the date that such Registration Statement is declared effective by the Commission or such
earlier date when all Registrable Securities covered by a Registration Statement have been sold or may be sold without volume restrictions pursuant to Rule 144(k).

4.Procedures.Tenant shall furnish to Landlord, without charge, as many copies of each Prospectus or
Prospectuses (including each form of prospectus) and each amendment or supplement thereto as Landlord may reasonably request. Prior to any public offering of Registrable Securities, Tenant shall use
its best efforts to register or qualify or cooperate with Landlord in connection with the registration or qualification (or exemption from such registration or qualification) of such Registrable
Securities for offer and sale under the securities or Blue Sky laws of all jurisdictions within the United States, to keep each such registration or qualification (or exemption therefrom) effective
during the Effectiveness Period and to do any and all other acts or things necessary or advisable to enable the disposition in such jurisdictions of the Registrable Securities covered by the
Registration Statements;provided, that Tenant shall not be required to qualify generally to do business in any jurisdiction where it is not then so
qualified or subject Tenant to any material tax in any such jurisdiction where it is not then so subject.

At
any time, upon written notice to Landlord and for a period not to exceed twenty (20) Trading Days thereafter (the "Suspension
Period"), Tenant may suspend the use or effectiveness of the Registration Statement (and Landlord hereby agrees not to offer or sell any Registrable Securities pursuant to such
Registration Statement during the Suspension Period) if Tenant reasonably believes that it may, in the absence of such delay or suspension hereunder, be required under state or federal securities laws
to disclose any corporate development the disclosure of which could reasonably be expected to have a material adverse effect upon it, its stockholders, a potentially significant transaction or event
involving Tenant, or any negotiations, discussions, or proposals directly relating thereto. In the event that Tenant shall exercise its right to suspend the effectiveness of the Registration
Statement, the applicable time period during which the Registration Statement is to remain effective shall be extended by a period of time equal to the duration of the Suspension Period. Tenant may
extend the Suspension Period for an additional twenty (20) Trading Days with the consent of SF Capital. If so directed by Tenant, Landlord shall use its commercially reasonable efforts to
deliver to Tenant (at Tenant's expense) all copies, other than permanent file copies then in Landlord's possession, of the Prospectus relating to such Registrable Securities current at the time of
receipt of such notice.

Annex A  Plan of Distribution

The
Selling Stockholders and any of their pledgees, donees, assignees and successors-in-interest may, from time to time, sell any or all of their shares of Common
Stock on any stock exchange, market or trading facility on which the shares are traded or in private transactions. These sales may be at fixed or negotiated prices. The Selling Stockholders will act
independently of us in making decisions regarding the timing, manner and size of each sale. The Selling Stockholders may use any one or more of the following methods when selling shares:



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The
Selling Stockholders may also sell shares under Rule 144 under the Securities Act, if available, rather than under this prospectus.

Broker-dealers
engaged by the Selling Stockholders may arrange for other brokers-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the Selling
Stockholders (or, if any broker-dealer acts as agent for the purchaser of shares, from the purchaser) in amounts to be negotiated. The Selling Stockholders do not expect these commissions and
discounts to exceed what is customary in the types of transactions involved.

The
Selling Stockholders may from time to time pledge or grant a security interest in some or all of the Shares or Warrant Shares owned by them and, if they default in the performance of
their secured obligations, the pledgees or secured parties may offer and sell shares of Common Stock from time to time under this prospectus, or under an amendment to this prospectus under
Rule 424(b)(3) or other
applicable provision of the Securities Act of 1933 amending the list of selling stockholders to include the pledgee, transferee or other successors in interest as selling stockholders under this
prospectus.

Upon
the Tenant being notified in writing by a Selling Stockholder that any material arrangement has been entered into with a broker-dealer for the sale of Common Stock through a block
trade, special offering, exchange distribution or secondary distribution or a purchase by a broker or dealer, a supplement to this prospectus will be filed, if required, pursuant to Rule 424(b)
under the Securities Act, disclosing (i) the name of each such Selling Stockholder and of the participating broker-dealer(s), (ii) the number of shares involved, (iii) the price
at which such the shares of Common Stock were sold, (iv) the commissions paid or discounts or concessions allowed to such broker-dealer(s), where applicable, (v) that such
broker-dealer(s) did not conduct any investigation to verify the information set out or incorporated by reference in this prospectus, and (vi) other facts material to the transaction. In
addition, upon the Tenant being notified in writing by a Selling Stockholder that a donee or pledge intends to sell more than 500 shares of Common Stock, a supplement to this prospectus will be filed
if then required in accordance with applicable securities law.

The
Selling Stockholders also may transfer the shares of common stock in other circumstances, in which case the transferees, pledgees or other successors in interest will be the selling
beneficial owners for purposes of this prospectus.

The
Selling Stockholders and any broker-dealers or agents that are involved in selling the shares may be deemed to be "underwriters" within the meaning of the Securities Act in
connection with such sales. In such event, any commissions received by such broker-dealers or agents and any profit on the resale of the shares purchased by them may be deemed to be underwriting
commissions or discounts under the Securities Act. Because the Selling Stockholders may be deemed to be "underwriters" within the meaning of the Securities Act, the Selling Stockholders will be
subject to the prospectus delivery requirements of the Securities Act. Each Selling Stockholders has represented and warranted to the

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Tenant
that it does not have any agreement or understanding, directly or indirectly, with any person to distribute the Common Stock.

The
Tenant is required to pay all fees and expenses incident to the registration of the shares. The Tenant has agreed to indemnify the Selling Stockholders against certain losses,
claims, damages and liabilities, including liabilities under the Securities Act.

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