Document:

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                                                                   EXHIBIT 10.1

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
"1933 ACT") OR ANY STATE SECURITIES LAWS. SUCH SECURITIES MAY NOT BE SOLD OR
TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER
THE 1933 ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

                       WARRANT TO PURCHASE 25,000 SHARES
                            OF THE COMMON STOCK OF
                        Ribozyme Pharmaceuticals, Inc.

EFFECTIVE DATE: January 4, 2001

EXPIRATION DATE: January 4, 2004

     This certifies that Heidrick & Struggles, Inc. or its transferees or
assigns (each individually, the "Holder") for the agreed upon value of $1.00 and
for other good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, shall be entitled to purchase from Ribozyme
Pharmaceuticals, Inc., a Delaware corporation (the "Company"), having its
principal place of business at 2950 Wilderness Place, Boulder, Colorado 80301, a
maximum of 25,000 fully paid and nonassessable shares of the Company's Common
Stock ("Common Stock") for cash at a price equal to $9.938 per share (the
"Exercise Price") at any time, or from time to time, up to and including 5:00
p.m. Pacific time on the Expiration Date, upon the surrender to the Company at
its principal place of business (or at such other location as the Company may
advise the Holder in writing) of this Warrant properly endorsed, a Form of
Subscription in substantially the form attached hereto duly filled in and signed
and, as applicable, upon payment in cash or by check of the aggregate Exercise
Price for the number of shares for which this Warrant is being exercised
determined in accordance with the provisions hereof, or the surrender of the
right to acquire the number of shares of Common Stock determined in accordance
with Section 1.2. The Exercise Price and the number of shares of Common Stock
purchasable hereunder are subject to adjustment as provided in Section 3 of this
Warrant.

     The Warrant is being issued pursuant to the Agreement between the Company
and the Holder dated as of August 8, 2000 (the "Purchase Agreement"). The Holder
of this Warrant is subject to certain restrictions, and entitled to certain
rights as set forth in the Purchase Agreement. This Warrant is referred to as
the "Warrant" in the Purchase Agreement.

     This Warrant is subject to the following terms and conditions:

     1.   EXERCISE; ISSUANCE OF CERTIFICATES; PAYMENT FOR SHARES.

          1.1  General.  This Warrant is exercisable at the option of the holder
of record hereof at any time or from time, to time, up to the Expiration Date
for all or any part of the shares of Common Stock (but not for a fraction of a
share), which may be purchased hereunder. The Company agrees that the shares of
Common Stock purchased under this Warrant shall be and are deemed to be issued
to the Holder hereof as the record owner of such shares as of the close of
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business on the date on which this Warrant, properly endorsed, the completed and
executed Form of Subscription and appropriate payment for such shares shall have
each been delivered to the Company at its principal place of business.
Certificates for the shares of Common Stock so purchased, together with any
other securities or property to which the Holder is entitled upon such exercise,
shall be delivered to the Holder by the Company at the Company's expense within
a reasonable time after the rights represented by this Warrant have been so
exercised, and in any event, within five (5) business days of such exercise. In
case of a purchase of less than all the shares which may be purchased under this
Warrant, the Company shall cancel this Warrant and execute and deliver a new
Warrant or Warrants of like tenor for the balance of the shares purchasable
under the Warrant surrendered upon such purchase to the Holder hereof within a
reasonable time. Each stock certificate so delivered shall be in such
denominations of Common Stock as may be requested by the Holder hereof and shall
be registered in the name designated by such Holder.

          1.2  Net Issue Exercise.  Notwithstanding any provisions herein to the
contrary, if the fair market value of one share of the Company's Common Stock is
greater than the Exercise Price (at the date of calculation as set forth below),
in lieu of exercising this Warrant for cash, the Holder may elect a "Net Issue
Exercise" pursuant to which it will receive shares equal to the value (as
determined below) of this Warrant (or the portion thereof being exercised) by
surrender of this Warrant at the principal office of the Company together with
the properly endorsed Form of Subscription and notice of such election in which
event the Company shall issue to the Holder a number of shares of Common Stock
computed using the following formula:

               X = Y (A-B)
                   -------
                      A

     Where X = the number of shares of Common Stock to be issued to the Holder

                         Y =  the number of shares of Common Stock purchasable
                         under the Warrant or, if only a portion of the Warrant
                         is being exercised, the portion of the Warrant being
                         exercised (at the date of such exercise)

                         A =  the fair market value of one share of the
                         Company's Common Stock (at the date of such exercise)

                         B =  Exercise Price (as adjusted to the date of such
                         exercise).

For purposes of the above calculation, the fair market value of one share of
Common Stock shall be determined by the Company's Board of Directors in good
faith; provided, however, that where there is a public market for the Company's
Common Stock, the fair market value per share shall be the average of the
closing prices of the Company's Common Stock quoted on the Nasdaq National
Market (or similar system) or on any exchange on which the Common Stock is
listed, whichever is applicable, over the five (5) trading day period ending on
the trading day immediately preceding the day the Warrant is being exercised.

                                      2.
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     2.   SHARES TO BE FULLY PAID; RESERVATION OF SHARES.  The Company covenants
and agrees that all shares of Common Stock which may be issued upon the exercise
of the rights represented by this Warrant will, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable and free from all
preemptive rights of any shareholder and free of all taxes, liens and charges
with respect to the issue thereof. The Company further covenants and agrees
that, during the period within which the rights represented by this Warrant may
be exercised, the Company will at all times have authorized and reserved, for
the purpose of issue or transfer upon exercise of the subscription rights
evidenced by this Warrant, a sufficient number of shares of authorized but
unissued Common Stock, or other securities and property, when and as required to
provide for the exercise of the rights represented by this Warrant. The Company
will take all such action as may be necessary to assure that such shares of
Common Stock may be issued as provided herein without violation of any
applicable law or regulation, or of any requirements of any domestic securities
exchange upon which the Common Stock may be listed; provided, however, that the
Company shall not be required to effect a registration under Federal or State
securities laws with respect to such exercise. The Company will not take any
action which would result in any adjustment of the Exercise Price (as set forth
in Section 3 hereof) if the total number of shares of Common Stock issuable
after such action upon exercise of all outstanding warrants, together with all
shares of Common Stock then outstanding and all shares of Common Stock then
issuable upon exercise of all options and upon the conversion of all convertible
securities and other equity purchase rights then outstanding, would exceed the
total number of shares of Common Stock then authorized by the Company's
Articles/Certificate of Incorporation (the "Company Charter").

     3.   ADJUSTMENT OF EXERCISE PRICE AND NUMBER OF SHARES.  The Exercise Price
and the number of shares purchasable upon the exercise of this Warrant shall be
subject to adjustment from time to time upon the occurrence of certain events
described in this Section 3. Upon each adjustment of the Exercise Price, the
Holder of this Warrant shall thereafter be entitled to purchase, at the Exercise
Price resulting from such adjustment, the number of shares obtained by
multiplying the Exercise Price in effect immediately prior to such adjustment by
the number of shares purchasable pursuant hereto immediately prior to such
adjustment, and dividing the product thereof by the Exercise Price resulting
from such adjustment.

          3.1  Subdivision or Combination of Stock.  In case the Company shall
at any time subdivide its outstanding shares of Common Stock into a greater
number of shares, the Exercise Price in effect immediately prior to such
subdivision shall be proportionately reduced, and conversely, in case the
outstanding shares of Common Stock of the Company shall be combined into a
smaller number of shares (by reverse stock split or otherwise), the Exercise
Price in effect immediately prior to such combination shall be proportionately
increased.

          3.2  Dividends in Common Stock, Other Stock, Property,
Reclassification.  If at any time or from time to time the Holders of Common
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

               (a)  Common Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Common Stock, or any

                                      3.
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rights or options to subscribe for, purchase or otherwise acquire any of the
foregoing by way of dividend or other distribution,

               (b)  any cash paid or payable otherwise than as a cash dividend,
or

               (c)  Common Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than shares of
Common Stock issued as a stock split or adjustments in respect of which shall be
covered by the terms of Section 3.1 above),

then, and in each such case, the Holder hereof shall, upon the exercise of this
Warrant, be entitled to receive, in addition to the number of shares of Common
Stock receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clause (b) above and this clause (c)) which such
Holder would hold on the date of such exercise had he been the holder of record
of such Common Stock as of the date on which holders of Common Stock received or
became entitled to receive such shares or all other additional stock and other
securities and property.

          3.3  Reorganization, Consolidation, Merger or Sale.  If any
recapitalization or reorganization of the capital stock of the Company, or any
consolidation or merger of the Company with another corporation, or the sale of
all or substantially all of its assets or other transaction shall be effected in
such a way that holders of Common Stock shall be entitled to receive stock,
securities, or other assets or property (an "Organic Change"), then, as a
condition of such Organic Change, lawful and adequate provisions shall be made
by the Company whereby the Holder hereof shall thereafter have the right to
purchase and receive (in lieu of the shares of the Common Stock of the Company
immediately theretofore purchasable and receivable upon the exercise of the
rights represented by this Warrant) such shares of stock, securities or other
assets or property as may be issued or payable with respect to or in exchange
for a number of outstanding shares of such Common Stock equal to the number of
shares of such stock immediately theretofore purchasable and receivable upon the
exercise of the rights represented by this Warrant. In the event of any Organic
Change, appropriate provision shall be made by the Company with respect to the
rights and interests of the Holder of this Warrant to the end that the
provisions hereof (including, without limitation, provisions for adjustments of
the Exercise Price and of the number of shares purchasable and receivable upon
the exercise of this Warrant) shall thereafter be applicable, in relation to any
shares of stock, securities or assets thereafter deliverable upon the exercise
hereof. Prior to the consummation of any such consolidation, merger or sale, the
successor entity (if other than the Company) resulting from such consolidation
or the corporation purchasing such assets shall assume by written instrument
reasonably satisfactory in form and substance to the Holders executed and mailed
or delivered to the registered Holder hereof at the last address of such Holder
appearing on the books of the Company, the obligation to deliver to such Holder
such shares of stock, securities or assets as, in accordance with the foregoing
provisions, such Holder may be entitled to purchase.

          3.4  Certain Events.  If any change in the outstanding Common Stock of
the Company or any other event occurs as to which the other provisions of this
Section 3 are not strictly applicable or if strictly applicable would not fairly
protect the purchase rights of the Holder of the Warrant in accordance with such
provisions, then the Board of Directors of the

                                      4.
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Company shall make an adjustment in the number and class of shares available
under the Warrant, the Exercise Price or the application of such provisions, so
as to protect such purchase rights as aforesaid. The adjustment shall be such as
will give the Holder of the Warrant upon exercise for the same aggregate
Exercise Price the total number, class and kind of shares as the Holder would
have owned had the Warrant been exercised prior to the event and had the Holder
continued to hold such shares until after the event requiring adjustment.

          3.5  Notices of Change.

               (a)  Immediately upon any adjustment in the number or class of
shares subject to this Warrant and/or of the Exercise Price, the Company shall
give written notice thereof to the Holder, setting forth in reasonable detail
and certifying the calculation of such adjustment.

               (b)  The Company shall give written notice to the Holder at least
10 business days prior to the date on which the Company closes its books or
takes a record for determining rights to receive any dividends or distributions.

               (c)  The Company shall also give written notice to the Holder at
least 30 business days prior to the date on which an Organic Change shall take
place.

     4.   ISSUE TAX.  The issuance of certificates for shares of Common Stock
upon the exercise of the Warrant shall be made without charge to the Holder of
the Warrant for any issue tax (other than any applicable income taxes) in
respect thereof; provided, however, that the Company shall not be required to
pay any tax which may be payable in respect of any transfer involved in the
issuance and delivery of any certificate in a name other than that of the then
Holder of the Warrant being exercised.

     5.   CLOSING OF BOOKS.  The Company will at no time close its transfer
books against the transfer of any warrant or of any shares of Common Stock
issued or issuable upon the exercise of any warrant in any manner which
interferes with the timely exercise of this Warrant.

     6.   NO VOTING OR DIVIDEND RIGHTS; LIMITATION OF LIABILITY.  Nothing
contained in this Warrant shall be construed as conferring upon the Holder
hereof the right to vote or to consent or to receive notice as a shareholder of
the Company or any other matters or any rights whatsoever as a shareholder of
the Company. No dividends or interest shall be payable or accrued in respect of
this Warrant or the interest represented hereby or the shares purchasable
hereunder until, and only to the extent that, this Warrant shall have been
exercised. No provisions hereof, in the absence of affirmative action by the
holder to purchase shares of Common Stock, and no mere enumeration herein of the
rights or privileges of the holder hereof, shall give rise to any liability of
such Holder for the Exercise Price or as a shareholder of the Company, whether
such liability is asserted by the Company or by its creditors.

     7.   WARRANTS TRANSFERABLE.  Subject to compliance with applicable federal
and state securities laws, this Warrant and all rights hereunder are
transferable, in whole or in part, without charge to the holder hereof (except
for transfer taxes), upon surrender of this Warrant properly endorsed. Each
taker and holder of this Warrant, by taking or holding the same, consents and
agrees that this Warrant, when endorsed in blank, shall be deemed negotiable,

                                      5.
<PAGE>

and that the holder hereof, when this Warrant shall have been so endorsed, may
be treated by the Company, at the Company's option, and all other persons
dealing with this Warrant as the absolute owner hereof for any purpose and as
the person entitled to exercise the rights represented by this Warrant, or to
the transfer hereof on the books of the Company any notice to the contrary
notwithstanding; but until such transfer on such books, the Company may treat
the registered owner hereof as the owner for all purposes.

     8.   RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, shall survive the
exercise of this Warrant.

     9.   FURTHER REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY.

               (a)  Articles and Bylaws.  The Company has made available to
Holder true, complete and correct copies of the Company Charter and Bylaws, as
amended, through the date hereof.

               (b)  Due Authority.  The execution and delivery by the Company
of this Warrant and the performance of all obligations of the Company hereunder,
including the issuance to Holder of the right to acquire the shares of Common
Stock, have been duly authorized by all necessary corporate action on the part
of the Company, and the Warrant is not inconsistent with the Company Charter or
Bylaws and constitutes a legal, valid and binding agreement of the Company,
enforceable in accordance with its terms.

               (c)  Consents and Approvals.  No consent or approval of, giving
of notice to, registration with, or taking of any other action in respect of any
state, federal or other governmental authority or agency is required with
respect to the execution, delivery and performance by the Company of its
obligations under this Warrant, except for any filing required by applicable
federal and state securities laws, which filing will be effective by the time
required thereby.

               (d)  Issued Securities.  All issued and outstanding shares of
capital stock of the Company have been duly authorized and validly issued and
are fully paid and nonassessable. All outstanding shares of capital stock were
issued in full compliance with all federal and state securities laws.

               (e)  Exempt Transaction.  Subject to the accuracy of the Holders
representations in Section 10 hereof, the issuance of the Common Stock upon
exercise of this Warrant will constitute a transaction exempt from (i) the
registration requirements of Section 5 of the Securities Act of 1933, as amended
(the "1933 Act"), in reliance upon Section 4(2) thereof, and (ii) the
qualification requirements of the applicable state securities laws.

               (f)  Compliance with Rule 144.  At the written request of the
Holder, who proposes to sell Common Stock issuable upon the exercise of the
Warrant in compliance with Rule 144 promulgated by the Securities and Exchange
Commission, the Company shall furnish to the Holder, within thirty (30) days
after receipt of such request, a written statement confirming the Company's
compliance with the filing requirements of the Securities and

                                      6.
<PAGE>

Exchange Commission as set forth in such Rule, as such Rule may be amended from
time to time.

     10.  REPRESENTATIONS AND COVENANTS OF THE HOLDER.

     This Warrant has been entered into by the Company in reliance upon the
following representations and covenants of the Holder:

               (a)  Investment Purpose.  The Warrant and the Common Stock
issuable upon exercise of the Warrant will be acquired for investment and not
with a view to the sale or distribution of any part thereof, and the Holder has
no present intention of selling or engaging in any public distribution of the
same except pursuant to a registration or exemption pursuant to the 1933 Act.

               (b)  Private Issue.  The Holder understands (i) that the Warrant
and the Common Stock issuable upon exercise of this Warrant is not registered
under the 1933 Act or qualified under applicable state securities laws on the
ground that the issuance contemplated by this Warrant will be exempt from the
registration and qualifications requirements thereof pursuant to Section 4(2) of
the 1933 Act and any applicable state securities laws, and (ii) that the
Company's reliance on such exemption is predicated on the representations set
forth in this Section 10.

               (c)  Disposition of Holders Rights.  In no event will the Holder
make a disposition of the Warrant or the Common Stock issuable upon exercise of
the Warrant unless and until (i) it shall have notified the Company of the
proposed disposition, and (ii) if requested by the Company, it shall have
furnished the Company with an opinion of counsel (which counsel may either be
inside or outside counsel to the Holder) satisfactory to the Company and its
counsel to the effect that (A) appropriate action necessary for compliance with
the 1933 Act has been taken, or (B) an exemption from the registration
requirements of the 1933 Act is available. Notwithstanding the foregoing, the
restrictions imposed upon the transferability of any of its rights to acquire
Common Stock or Common Stock issuable on the exercise of such rights do not
apply to transfers from the beneficial owner of any of the aforementioned
securities to its nominee or from such nominee to its beneficial owner, and
shall terminate as to any particular share of Common Stock when (1) such
security shall have been effectively registered under the 1933 Act and sold by
the holder thereof in accordance with such registration or (2) such security
shall have been sold without registration in compliance with Rule 144 under the
1933 Act, or (3) a letter shall have been issued to the Holder at its request by
the staff of the Securities and Exchange Commission or a ruling shall have been
issued to the Holder at its request by such Commission stating that no action
shall be recommended by such staff or taken by such Commission, as the case may
be, if such security is transferred without registration under the 1933 Act in
accordance with the conditions set forth in such letter or ruling and such
letter or ruling specifies that no subsequent restrictions on transfer are
required. Whenever the restrictions imposed hereunder shall terminate, as
hereinabove provided, the Holder or holder of a share of Common Stock then
outstanding as to which such restrictions have terminated shall be entitled to
receive from the Company, without expense to such holder, one or more new
certificates for the Warrant or for such shares of Common Stock not bearing any
restrictive legend.

                                      7.
<PAGE>

               (d)  Financial Risk.  The Holder has such knowledge and
experience in financial and business matters as to be capable of evaluating the
merits and risks of its investment, and has the ability to bear the economic
risks of its investment.

               (e)  Risk of No Registration.  The Holder understands that if the
Company does not register with the Securities and Exchange Commission pursuant
to Section 12 of the 1933 Act, or file reports pursuant to Section 15(d), of the
Securities Exchange Act of 1934 (the "1934 Act"), or if a registration statement
covering the securities under the 1933 Act is not in effect when it desires to
sell (i) the Warrant, or (ii) the Common Stock issuable upon exercise of the
Warrant, it may be required to hold such securities for an indefinite period.
The Holder also understands that any sale of the Warrant or the Common Stock
issuable upon exercise of the Warrant which might be made by it in reliance upon
Rule 144 under the 1933 Act may be made only in accordance with the terms and
conditions of that Rule.

               (f)  Accredited Investor.  Holder is an "accredited investor"
within the meaning of Rule 501 of Regulation D under the 1933 Act, as presently
in effect.

     11.  MODIFICATION AND WAIVER.  This Warrant and any provision hereof may be
waived, discharged or terminated only by an instrument in writing signed by the
party against which enforcement of the same is sought.

     12.  NOTICES.  Any notice, request or other document required or permitted
to be given or delivered to the holder hereof or the Company shall be delivered
or shall be sent by an established overnight service provider (e.g., Federal
Express), or registered or certified mail, postage prepaid, to each such holder
at its address as shown on the books of the Company or to the Company at the
address indicated therefor in the first paragraph of this Warrant or such other
address as either may from time to time provide to the other in accordance with
this Section.

     13.  BINDING EFFECT ON SUCCESSORS.  This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets. All of the obligations of the
Company relating to the Common Stock issuable upon the exercise of this Warrant
shall survive the exercise and termination of this Warrant. All of the covenants
and agreements of the Company shall inure to the benefit of the successors and
assigns of the holder hereof.

     14.  DESCRIPTIVE HEADINGS AND GOVERNING LAW.  The description headings of
the several sections and paragraphs of this Warrant are inserted for convenience
only and do not constitute a part of this Warrant. This Warrant shall be
construed and enforced in accordance with, and the rights of the parties shall
be governed by, the laws of the State of Colorado, without giving effect to
principles of conflicts of laws.

     15.  LOST WARRANTS.  The Company represents and warrants to the Holder
hereof that upon receipt of evidence reasonably satisfactory to the Company of
the loss, theft, destruction, or mutilation of this Warrant and, in the case of
any such loss, theft or destruction, upon receipt of an indemnity reasonably
satisfactory to the Company, or in the case of any such mutilation upon
surrender and cancellation of such Warrant, the Company, at its expense, will

                                      8.
<PAGE>

make and deliver a new Warrant, of like tenor, in lieu of the lost, stolen,
destroyed or mutilated Warrant.

     16.  FRACTIONAL SHARES.  No fractional shares shall be issued upon exercise
of this Warrant. The Company shall, in lieu of issuing any fractional share, pay
the holder entitled to such fraction a sum in cash equal to such fraction
multiplied by the then effective Exercise Price.

                                      9.
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be duly executed
by its officers, thereunto duly authorized.

                                    Ribozyme Pharmaceuticals, Inc.
                                    a Delaware corporation

                                    By: /s/ Ralph E. Christoffersen
                                        --------------------------------

                                    Name: Ralph E. Christoffersen, Ph.D.
                                          ------------------------------

                                    Title: Chief Executive Officer
                                           -----------------------------

ATTEST:

/s/ Lawrence E. Bullock
-------------------------------
Secretary

Lawrence E. Bullock
<PAGE>

                                   EXHIBIT A

                               SUBSCRIPTION FORM

                                               Date:  _________________, 200___

Ribozyme Pharmaceuticals, Inc.
2950 Wilderness Place
Boulder, Colorado 80301

Attn:  President

Ladies and Gentlemen:

[_]  The undersigned hereby elects to exercise the warrant issued to it by
     ______________ (the "Company") and dated ___________ _____, ____ -___ (the
     "Warrant") and to purchase thereunder __________________________________
     shares of the Common Stock of the Company (the "Shares") at a purchase
     price of ___________________________________________ Dollars ($__________)
     per Share or an aggregate purchase price of
     __________________________________ Dollars ($__________) (the "Exercise
     Price"). Pursuant to the terms of the Warrant the undersigned has delivered
     the Exercise Price herewith in full in cash or by certified check or wire
     transfer.

[_]  The undersigned hereby elects to convert _______________________ percent
     (____%) of the value of the Warrant pursuant to the provisions of Section
     1.2 of the Warrant.

Please issue a certificate or certificates representing said shares of Common
Stock in the name of the undersigned or in such other name as is specified
below:

               Name: _____________________________

               Address: __________________________

               ___________________________________

                                    Very truly yours,

                                    __________________________________

                                    By: ______________________________

                                    Title: ___________________________<PAGE>

                                                                  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

                                       1
<PAGE>

     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

                                       2
<PAGE>

          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
       ------------------------------------         ----------------------------

                                       3

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