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                                                                  EXHIBIT 10.2

CONFIDENTIAL PORTIONS OF THIS EXHIBIT HAVE BEEN OMITTED PURSUANT TO REGULATION
240.25B-2B OF THE SECURITIES EXCHANGE ACT OF 1934. [*] INDICATES OMITTED
MATERIAL THAT IS THE SUBJECT OF A CONFIDENTIAL TREATMENT REQUEST AND IS FILED
SEPARATELY WITH THE COMMISSION.


   AMENDMENT TO CHIRON CORP. - RIBOZYME PHARMACEUTICALS, INC. COLLABORATIVE
             RESEARCH, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

This Amendment to Chiron Corp. - Ribozyme Pharmaceuticals, Inc Collaborative
Research, Development and Commercialization Agreement ("Amendment") is entered
into effective as of March 20, 2001 (the "Effective Date") by and between Chiron
Corporation, a Delaware corporation having a place of business at 4560 Horton
Street, Emeryville, California 94608 ("Chiron"), and Ribozyme Pharmaceuticals,
Inc., a Delaware corporation having a place of business at 2950 Wilderness
Place, Boulder, Colorado 80301 ("RPI").


                                   RECITALS

     A.   RPI and Chiron are parties to that certain Chiron Corp. - Ribozyme
          Pharmaceuticals, Inc Collaborative Research, Development and
          Commercialization Agreement effective as of July 15, 1994, as amended
          by that certain letter agreement between Chiron and RPI effective
          October 8, 1998 (together, the "Agreement").

     B.   Pursuant to the Agreement, RPI and Chiron have evaluated certain
          targeted genetic sequences for potential clinical development and
          commercialization as human therapeutics or diagnostics within the
          Field. The parties now seek to modify their rights and obligations
          under the Agreement with respect to a certain Named Target on the
          terms and conditions set forth in this Amendment.

NOW THEREFORE, in consideration of the mutual promises contained herein, the
parties agree as follows:

1.   Definitions.  Unless otherwise defined herein, the terms in this Amendment
     -----------
     shall have the same meaning given them in the Agreement.

     1.1  "HIV" shall mean human immunodeficiency virus.

2.   HIV as Named Target.  The parties hereby agree that, as of the Effective
     -------------------
     Date of this Amendment, (i) HIV shall cease to be a Named Target and may
     not hereafter be nominated as a Named Target, a Suggested Target or a
     Potential Named Target under the Agreement and (ii) RPI shall be entitled
     to all rights of a Developing Party of a Solely

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     Developed Product with respect to any Product containing or utilizing an
     HIV Target ("HIV Product"), subject to the following terms and conditions.

     2.1  In partial consideration for the rights granted pursuant to Section 2
          above, RPI shall pay to Chiron a non-refundable, non-creditable fee in
          the amount of Two Hundred Seventy-Five Thousand Dollars ($275,000)
          ("HIV Fee") payable as follows: RPI shall transfer to Chiron within
          ten (10) days of the Effective Date, pursuant to RPI's standard form
          of stock transfer agreement, such number shares of RPI common stock at
          the average of the closing price for RPI's common stock on each of the
          ten (10) consecutive Business Days prior to the Effective Date
          (rounding down to the nearest share) equal to the HIV Fee. "Business
          Day" shall mean any date upon which NASDAQ is open for trading.

     2.2  Chiron and RPI waive their rights under Section 8.5 of the Agreement
          with respect to any HIV Product.

     2.3  With respect to any HIV Product, Chiron shall be a Non-Developing
          Party, provided however that any royalty obligations payable to Chiron
          under Section 8.6 of the Agreement shall be modified as follows:

          In partial consideration for the rights granted pursuant to Section 2
          above, RPI shall pay to Chiron royalties according to the following
          schedule on the Net Sales of each HIV Product developed and
          commercialized by RPI:

          Annual Net Sales                        Royalty
          ----------------                        -------

          [ * ]                                   [ * ]
          [ * ]                                   [ * ]
          [ * ]                                   [ * ]
          [ * ]                                   [ * ]

3.   Rights to Collaboration Technology.   RPI shall have the right to use and
     ----------------------------------
     sublicense Jointly Owned Technology in connection with the development,
     manufacture and commercialization of any HIV Product but shall have no
     right to use any Chiron Core Technology, Chiron Developed Technology and
     Chiron Additional Contributed Technology in connection with the
     development, manufacture and commercialization of any HIV Product.

4.   Representations and Warranties.
     ------------------------------

     4.1  Each party represents that it (i) has all right, power and authority
          necessary to enter into this Amendment and to grant the rights granted
          herein, (ii) has obtained all approvals and authorizations that it is
          required to obtain in connection with this Amendment under applicable
          laws and regulations, and (iii) has not entered, and

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          will not enter, into any arrangements or agreements inconsistent with
          this Agreement.

     4.2  RPI represents and warrants to Chiron that RPI has not, to the best of
          its knowledge, infringed, and covenants that RPI will not knowingly
          and willfully infringe, any intellectual or proprietary property
          rights owned or controlled by Chiron, including without limitation,
          any patents or patent applications, and, specifically without
          limitation, any Chiron Core Technology, Chiron Developed Technology or
          Chiron Additional Contributed Technology. RPI shall indemnify and hold
          Chiron, its directors, officers, employees, agents, and Affiliates
          harmless against all claims, demands, damages, liabilities, losses,
          costs and expenses, including without limitation attorney's fees,
          resulting from or arising out of any material breach by RPI of any of
          RPI's representations, warranties or covenants hereunder.

5.   Entire Agreement.  The terms and conditions herein contained constitute the
     ----------------
entire agreement between the parties hereto with respect to the subject matter
hereof and supersede all previous agreements and understandings, whether oral or
written, between the parties.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be signed
by duly authorized officers or representatives as of the date first above
written.


CHIRON CORPORATION                           RIBOZYME PHARMACEUTICALS, INC.


By: /s/ Lewis T. Williams                    By: /s/ Ralph E Christoffersen
    ---------------------------------------      -------------------------------

Print Name: Lewis T. Williams, M.D., Ph.D.   Print Name: Ralph E. Christoffersen
            -------------------------------              -----------------------

Title: Chief Scientific Officer, Pres., R&D  Title: Chief Executive Officer
       ------------------------------------         ----------------------------

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