Exhibit
10.9  FIRST AMENDMENT TO
SUBLEASE AND SUBLEASE EXTENSION
AGREEMENT   THIS FIRST AMENDMENT TO SUBLEASE AND SUBLEASE
EXTENSION AGREEMENT (Agreement) is made as of this 12th day of
December, 2001, by and between Microbar, Inc. (Sublessor) and Aerogen, Inc.
(Sublessee).  RECITALS  A.            Sublessor
is lessee under that certain Lease dated December 17, 1996 with The Realty
Associates Fund III, L.P. as lessor (Master Lessor), as amended by that
certain Amendment dated April 28, 1999 (as amended, the Master Lease).  B.            Sublessor
and Sublessee entered into that certain Sublease dated August 9, 1999 (as
amended to date, the Sublease), for approximately 38,000 rentable square feet
of space located at Orleans Drive, Sunnyvale, California (the Entire Premises).  The Sublease is subject to the Master Lease
as provided in Recital B of the Sublease. 
Capitalized terms used in this Agreement but not defined herein shall
have the meanings given them in the Sublease.  C.            The
stated term of the Sublease expires on December 31, 2001 (Expiration Date).  D.            Sublessee
desires, and the Sublessor is willing, to extend the term of the Sublease for
the Entire Premises through June 30, 2002 on the terms and conditions set forth
in this Agreement.   NOW, THEREFORE, for valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, Sublessor and
Sublessee hereby amend the Sublease as follows:  1.             Extension
of Term.  The term of the Sublease
for the Entire Premises is extended through June 30, 2002.  2.             Rent
for the Entire Premises.  Base Rent
for the Entire Premises, from January 1, 2002 through June 30, 2002, shall be
as follows:  Month
  
  RentJanuary through
  March
  
  $63,181April
  
  $25,000May
  
  $20,000June
  
  $20,000    
   3.             Surrender
of Entire Premises.  Sublessee shall
vacate and surrender the Entire Premises in the condition required by the
Sublease on or before June 30, 2002. 
Sublessees obligation to pay Base Rent and Additional Rent for the
Surrendered Premises shall cease and terminate on June 30, 2002.  Sublessor shall notify Sublessee in writing
of those Tenant Improvements which Sublessor requires Sublessee to remove from
the Surrendered Premises on or before June 1, 2001.  4.             Ongoing
Rights.  Until June 30, 2002,
Sublessee shall have the right to its monument signage and the parking rights
which Sublessor has pursuant to the Master Lease, and Sublessee and its agents
and employees shall continue to have all rights to use entry doors, hallways
and restrooms pursuant to the Sublease.  5.             Brokers.  Sublessor and Sublessee each represent and
warrant to the other that it has dealt with no brokers (Brokers) in
connection with this Agreement.  Each of
the Sublessor and Sublessee shall indemnify and hold harmless the other from
and against any and all claims, liabilities, losses, damages, costs and
expenses (including, without limitation, attorneys fees) arising out of or
related to any breach of such partys representation and warranty set forth in
this Paragraph 5.  6.             Counterparts.  This Sublease may be signed in multiple
counterparts which, when signed by all parties, shall constitute a binding
agreement.  7.             Conflicts;
No Further Amendments.  In the event
of any conflict or inconsistency between the terms and conditions of this Agreement
and the terms and conditions of the Sublease, the terms and conditions of this
Agreement shall control.  Except as
expressly amended or modified above, the terms and conditions of the Sublease
shall remain unmodified and in full force and effect.  IN WITNESS WHEREOF, Sublessor and Sublessee have
executed this Agreement as of the date and year first above written.   SUBLESSOR:
  MICROBAR, INC.
  
  SUBLESSEE:
  AEROGEN, INC.By:  /s/
  Michael Lund
  
  By:  /s/
  Carol A. GambleIts:  Chief
  Financial Officer
  
  Its:  Vice
  President and General Counsel    2