<PAGE>

                                                                   Exhibit 10.53


THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933. THEY
MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, OR HYPOTHECATED IN THE ABSENCE OF AN
EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL (WHICH
MAY BE COMPANY COUNSEL) REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH
REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT OF 1933.

                               WARRANT AGREEMENT

             To Purchase Shares of the Series A Preferred Stock of

                                 ONTOGENY, INC.

              Dated as of November 2, 1994 (the "Effective Date")

     WHEREAS, Ontogeny, Inc., a Delaware corporation (the "Company") has
entered into a Master Lease Agreement dated as of October 25, 1994, Equipment
Schedule No. VL-1, and related Schedules (the "Leases") with Comdisco, Inc., a
Delaware corporation (the "Warrantholder"); and

     WHEREAS, the Company desires to grant to Warrantholder, in
consideration for such Leases, the right to purchase shares of its Preferred
Stock;

     NOW, THEREFORE, in consideration of the Warrantholder executing and
delivering such Leases and in consideration of mutual covenants and agreements
contained herein, the Company and Warrantholder agree as follows:

1.   GRANT OF THE RIGHT TO PURCHASE PREFERRED STOCK.
     ----------------------------------------------

     The Company hereby grants to the Warrantholder, and the Warrantholder
is entitled, upon the terms and subject to the conditions hereinafter set forth,
to subscribe to and purchase, from the Company, 68,965 fully paid and non-
assessable shares of the Company's Series A Convertible Preferred Stock
("Preferred Stock") at a purchase price of $.87 per share (the "Exercise
Price"). The number and purchase price of such shares are subject to adjustment
as provided in Section 8 hereof.

     If the Warrantholder fails to make available any or all of the Part II
lease financing as set forth in the Leases, then the number of shares of the
Company's Preferred Stock which the Warrantholder shall be entitled to purchase
hereunder shall be reduced by 17,241 to 51,724.

2.   TERM OF THE WARRANT AGREEMENT.
     -----------------------------

     (a)   Except as otherwise provided for herein, the term of this Warrant
Agreement and the right to purchase Preferred Stock as granted herein shall
commence on the Effective Date and shall be exercisable for a period of ten (10)
years.

     (b)   Acceleration of Term Upon Initial Public Offering.  Not
           -------------------------------------------------
withstanding the term of this Warrant Agreement fixed pursuant to Section 2(a)
hereof, Warrantholder's right to purchase Preferred Stock as granted herein
shall expire, if not previously exercised, immediately upon the closing of the
issuance and sale of shares of Common Stock of the
<PAGE>

Company in the Company's first public offering of securities for its own account
pursuant to an effective registration statement under the Securities Act of
1933, as amended (the "Initial Public offering"), provided that the underwriters
request that the Warrantholder exercise this Warrant.

     The Company shall notify the Warrantholder if the Initial Public Offering
is proposed, within a reasonable period of time prior to the filing of a
registration statement and if the Company fails to deliver such written notice
within a reasonable period of time, anything to the contrary in this Warrant
Agreement notwithstanding, the rights to purchase will not expire until ten (10)
business days after the Company delivers such notice to the Warrantholder. Such
notice shall also contain such details of the proposed Initial Public Offering
as are reasonable in the circumstances and notice that this Warrant Agreement is
expected to expire upon closing thereof. If such closing does not take place,
the Company shall promptly notify the Warrantholder that such proposed
transaction has been terminated. Anything to the contrary in this Warrant
Agreement notwithstanding, the Warrantholder may rescind any exercise of its
purchase rights promptly after such notice of termination of the proposed
transaction if the exercise of Warrants occurred after the Company notified the
Warrantholder that the Initial Public Offering was proposed or if the exercise
were otherwise precipitated by such proposed Initial Public Offering. In the
event of such rescission, the Warrants will continue to be exercisable on the
same terms and conditions.

3.   EXERCISE OF THE PURCHASE RIGHTS.
     -------------------------------

     The purchase rights set forth in this Warrant Agreement are exercisable by
the Warrantholder, in whole or in part, at any time, or from time to time, prior
to the expiration of the term set forth in Section 2 above, by tendering to the
company at its principal office a notice of exercise in the form attached hereto
as Exhibit I (the "Notice of Exercise"), duly completed and executed. Promptly
upon receipt of the Notice of Exercise and the payment of the purchase price in
accordance with the terms set forth below, and in no event later than twenty-one
(21) days thereafter, the Company shall issue to the Warrantholder a certificate
for the number of shares of Preferred Stock purchased and shall execute the
Notice of Exercise indicating the number of shares which remain subject to
future purchases, if any.

     The Exercise Price may be paid at the Warrantholder's election either
(i) by cash or check, or (ii) by surrender of Warrants ("Net Issuance") as
determined below.  If the Warrantholder elects the Net Issuance method, the
Company will issue Preferred Stock in accordance with the following formula:

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

Where:    X =  the number of shares of Preferred Stock to be issued to the
               Warrantholder.

     Y =  the, number of shares of Preferred Stock requested to be exercised
          under this Warrant Agreement.

     A =  the fair market value of one (1) share of Common Stock.

     B =  the Exercise Price.

                                       2
<PAGE>

          As used herein, current fair market value of Common Stock shall mean
with respect to each share of Common Stock:

          (i)     if the exercise is in connection with an initial public
     offering, and if the Company's Registration Statement relating to such
     public offering has been declared effective by the SEC, then the initial
     "Price to Public" specified in the final prospectus with respect to the
     offering;

          (ii)    if this Warrant is exercised after, and not in connection with
     the company's initial public offering, and:

                  (a) if traded on a securities exchange, the fair market value
                  shall be deemed to be the average of the closing prices over a
                  twenty-one (21) day period ending three days before the day
                  the current fair market value of the securities in being
                  determined; or

                  (b) if actively traded over-the-counter, the fair market value
                  shall be deemed to be the average of the closing bid and asked
                  prices quoted on the NASDAQ system (or similar system) over
                  the twenty-one (21) day period ending three days before the
                  day the current fair market value of the securities is being
                  determined;

          (iii)   if at any time the Common Stock is not listed on any
          securities exchange or quoted in the NASDAQ System or the over-the-
          counter market, the current fair market value of Common Stock shall be
          the highest price per share which the Company could obtain from a
          willing buyer (not a current employee or director) for shares of
          Common stock sold by the Company, from authorized but unissued shares,
          as determined in good faith by its Board of Directors, unless the
          Company shall become subject to a merger, acquisition or other
          consolidation pursuant to which the company is not the surviving
          party, in which came the fair market value of Common Stock shall be
          deemed to be the value per share of Common Stock received by the
          holders of the Company's Preferred Stock on a common equivalent basis
          pursuant to such merger or acquisition.

          Upon partial exercise by either cash or Net Issuance, the Company
     shall promptly issue an amended Warrant Agreement representing the
     remaining number of shares purchasable hereunder. All other terms and
     conditions of such amended Warrant Agreement shall be identical to those
     contained herein, including, but not limited to the Effective Date hereof.

4.   RESERVATION OF SHARES.
     ---------------------

     (a)  Authorization and Reservation of Shares.  During the term of this
          ---------------------------------------
Warrant Agreement, the Company will at all times have authorized and reserved a
sufficient number of shares of its Preferred Stock to provide for the exercise
of the rights to purchase Preferred Stock as provided for herein.

     (b)  Registration or Listing.  If any shares of Preferred Stock required to
          -----------------------
be reserved hereunder require registration with or approval of any governmental
authority under any Federal or State law (other than any registration under the
1933 Act, as then in effect, or any similar Federal statute then enforced, or
any state securities law, required by reason of

                                       3
<PAGE>

any transfer involved in such conversion), or listing on any domestic securities
exchange, before such shares may be issued upon conversion, the Company will, at
its expense and as expeditiously as possible, use its best efforts to cause such
shares to be duly registered, listed or approved for listing on such domestic
securities exchange, as the case may be.

5.   NO FRACTIONAL SHARES OR SCRIP.
     -----------------------------

     No fractional shares or scrip representing fractional shares shall be
issued upon the exercise of the Warrant, but in lieu of such fractional shares
the Company shall make a cash payment therefor upon the basis of the Exercise
Price then in effect.

6.   NO RIGHTS AS SHAREHOLDER.
     ------------------------

     This Warrant Agreement does not entitle the Warrantholder to any voting
rights or other rights as a shareholder of the Company prior to the exercise of
the Warrant.

7.   WARRANTHOLDER REGISTRY.
     ----------------------

     The company shall maintain a registry showing the name and address of the
registered holder of this Warrant Agreement.

8.   ADJUSTMENT RIGHTS.
     -----------------

     The purchase price per share and the number of shares of Preferred Stock
purchasable hereunder are subject to adjustment, as follows:

     (a)   Merger and Sale of Assets.  If at any time there shall be a capital
           -------------------------
reorganization of the shares of the Company's stock (other than a combination,
reclassification, exchange or subdivision of shares otherwise provided for
herein), or a merger or consolidation of the Company with or into another
corporation when the company is not the surviving corporation, or the sale of
all or substantially all of the Company's properties and assets to any other
person (hereinafter referred to as a "Merger Event"), then, as a part of such
Merger Event, lawful provision shall be made so that the Warrantholder shall
thereafter be entitled to receive, upon exercise of the Warrant, the number and
kind of shares of stock or other securities of the successor corporation or cash
or other property that the Warrantholder would have been entitled to receive if
such Warrantholder had exercised this Warrant immediately prior to the Merger
Event.  In any such case, appropriate adjustment (as determined in good faith by
the Company's Board of Directors) shall be made in the application of the
provisions of this Warrant Agreement with respect to the rights and interest of
the Warrantholder after the Merger Event to the end that the provisions of this
Warrant Agreement (including adjustments of the Exercise Price and number of
shares of Preferred Stock purchasable) shall be applicable to the greatest
extent possible.

     (b)   Reclassification of Shares.  If the Company at any time shall, by
           --------------------------
combination, reclassification, exchange or subdivision of securities or
otherwise, change any of the Series A Preferred Stock exist into the same or a
different number of securities of any other class or classes, this Warrant
Agreement shall thereafter represent the right to acquire such number and kind
of securities as would have been issuable an the result of such change with
respect to the securities which were subject to the purchase rights under this
Warrant Agreement immediately prior to such combination, reclassification,
exchange, subdivision or other change.

                                       4
<PAGE>

     (c)   Subdivision or Combination of Shares. If the Company at any time
           ------------------------------------
shall combine or subdivide its Preferred Stock, the Exercise Price shall be
proportionately decreased in the case of a subdivision, or proportionately
increased in the case of a combination.

     (d)   Right to Purchase Additional Stock.  If the Warrantholder's total
           ----------------------------------
cost of equipment leased pursuant to Part I of the Leases exceeds $500,000.00,
Warrantholder shall have the right to purchase from the Company, at the Exercise
Price (adjusted as set forth herein), an additional number of shares of
Preferred Stock, which number shall be determined by (i) multiplying the amount
by which the Warrantholder's total equipment cost exceeds $500,000.00 by 9%, and
(ii) dividing the product thereof by the Exercise Price per share referenced
above.

     If the Warrantholder's total cost of equipment leased pursuant to Part II
of the Leases exceeds $250,000.00, Warrantholder shall have the right to
purchase from the Company, at the Exercise Price (adjusted as set forth herein),
an additional number of shares of Preferred Stock, which number shall be
determined by (i) multiplying the amount by which the Warrantholder's total
equipment cost exceeds $250,000.00 by 6%, and (ii) dividing the product thereof
by the Exercise Price per share referenced above.

     (e)   Antidilution Rights.  Additional antidilution rights applicable to
           -------------------
the Preferred Stock purchasable hereunder are as set forth in the Company's
Certificate of Incorporation, as amended through the Effective Date, a true and
complete copy of which is attached hereto as Exhibit __ (the "Charter"). The
Company shall promptly provide the Warrantholder with any restatement,
amendment, modification or waiver of the Charter affecting such anti-dilution
rights. The Company will give Warrantholder notice of all dilutive issuances of
its stock.

     (f)   Notice of Adjustments.  If:  (i) the company shall declare any
           ---------------------
dividend or distribution upon its stock, whether in cash, property, stock or
other securities; (ii) the Company shall offer for subscription prorata to the
holders of any class of its Preferred Stock or other convertible stock any
additional shares of stock of any class or other rights; (iii) there shall be
any Merger Event; or (iv) there shall be any voluntary or involuntary
dissolution, liquidation or winding up of the Company; (i) then, in connection
with each such event, the Company shall send to the Warrantholder: (A) at least
twenty (20) days' prior written notice of the date on which the books of the
Company shall close or a record shall be taken for such dividend, distribution,
subscription rights (specifying the date on which the holders of Preferred Stock
shall be entitled thereto) or for determining rights to vote in respect of such
Merger Event, dissolution, liquidation or winding up; and (B) in the case of any
such Merger Event, dissolution, liquidation or winding up, at least twenty (20)
days, prior written notice of the date when the same shall take place (and
specifying the date on which the holders of Preferred Stock shall be entitled to
exchange their Preferred Stock for securities or other property deliverable upon
such Merger Event, dissolution, liquidation or winding up).

     Each such written notice shall set forth, in reasonable detail, (i) the
event requiring the adjustment, (ii) the amount of the adjustment, (iii) the
method by which such adjustment was calculated, (iv) the Exercise Price, and (v)
the number of shares subject to purchase hereunder after giving effect to such
adjustment, and shall be given by first class mail, postage prepaid, addressed
to the Warrantholder, at the address as shown on the books of the Company.

     (g)   Timely Notice.  Failure to timely provide such notice required by
           -------------
subsection (g) above shall entitle Warrantholder to retain the benefit of the
applicable notice period

                                       5
<PAGE>

notwithstanding anything to the contrary contained in any insufficient notice
received by Warrantholder. The notice period shall begin on the date
Warrantholder actually receives a written notice containing all the information
specified above.

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

     (a)   Reservation of Preferred Stock.  The Preferred stock issuable upon
           ------------------------------
exercise of the Warrantholder's rights has been duly and validly reserved and,
when issued in accordance with the provisions of this Warrant Agreement, will be
validly issued, fully paid and non-assessable, and will be free of any taxes,
liens, charges or encumbrances of any nature whatsoever; provided, however, that
the Preferred Stock issuable pursuant to this Warrant Agreement may be subject
to restrictions on transfer under state and/or Federal securities laws.  The
Company has made available to the Warrantholder true, correct and complete
copies of its Charter and Bylaws, as amended, and minutes of all Board of
Directors (including all committees of the Board of Directors, if any) and
Shareholder meetings from inception through ________, 19__.  The issuance of
certificates for shares of Preferred Stock upon exercise of the Warrant shall be
made without charge to the Warrantholder for any issuance tax in respect
thereof, or other cost incurred by the Company in connection with such exercise
and the related issuance of shares of Preferred Stock.  The Company shall not be
required to pay any tax which may be payable in respect of any transfer involved
and the issuance and delivery of any certificate in a name other than that of
the Warrantholder.

     (b)   Due Authority.  The execution and delivery by the company of this
           -------------
Warrant Agreement and the performance of all obligations of the Company
hereunder, including the issuance to Warrantholder of the right to acquire the
shares of Preferred Stock, have been duly authorized by all necessary corporate
action on the part of the Company, and the Leases and this Warrant Agreement are
not inconsistent with the Company's Charter or Bylaws, do not contravene any law
or governmental rule, regulation or order applicable to it, do not and will not
contravene any provision of, or constitute a default under, any indenture,
mortgage, contract or other instrument to which it is a party or by which it is
bound, and the Leases and this Warrant Agreement constitute legal, valid and
binding agreements of the Company, enforceable in accordance with their
respective 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 Agreement, except for the filing of notices pursuant to Regulation
D under the 1933 Act and Section 4 (G) of the Illinois corporate Securities Law,
which filings will be effective by the time required thereby.

     (d)   Issued Securities.  All issued and outstanding shares of Common
           -----------------
Stock, Preferred Stock or any other securities of the Company have been duly
authorized and validly issued and are fully paid and nonassessable. All
outstanding shares of Common Stock, Preferred Stock and any other securities
were issued in full compliance with all Federal and state securities laws. In
addition:

     (i)   The authorized capital of the Company consists of (A) 8,000,000
shares of Common Stock, of which 1,270,000 shares are issued and outstanding,
and (B) 4,737,778 shares of Series A Preferred Stock, of which 4,737,778 shares
are issued and outstanding and are convertible into 4,737,778 shares of Common
Stock.

                                       6
<PAGE>

     (ii)   There are no other options, warrants, conversion privileges or other
rights presently outstanding to purchase or otherwise acquire any authorized but
unissued shares of the Company's capital stock or other securities of the
Company.

     (iii)  In accordance with the Company's Articles of Incorporation, no
shareholder of the Company has preemptive rights to purchase new issuances of
the Company's capital stock.

     (e)    Insurance.  The Company has in full force and effect insurance
            ---------
policies, with extended coverage, insuring the company and its property and
business against such losses and risks, and in such amounts, as are customary
for corporations engaged in a similar business and similarly situated.

     (f)    Other Commitments to Register Securities. Except as set forth in
            ----------------------------------------
this Warrant Agreement, Registration Rights and Right of First Refusal Agreement
dated August 26, 1994 between the Company and certain shareholders and the Stock
Purchase Agreement dated September 2, 1994 between the Company and a certain
Institution, the Company is not, pursuant to the terms of any other agreement
currently in existence, under any obligation to register under the 1933 Act any
of its presently outstanding securities or any of its securities which may
hereafter be issued.

     (g)   Exempt Transaction.  Subject to the accuracy of the Warrantholder's
           ------------------
representations in section 10 hereof, the issuance of the Preferred Stock upon
exercise of this Warrant will constitute a transaction exempt from (i) the
registration requirements of Section 5 of the 1933 Act, in reliance upon Section
4(2) thereof, and (ii) the qualification requirements of the Illinois Corporate
Securities Law, in reliance upon Section 4 (G) thereof.

     (h)   Compliance with Rule 144. At the written request of the
           ------------------------
Warrantholder, who proposes to sell Preferred 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 Warrantholder, within ten
days after receipt of such request, a written statement confirming the Company's
compliance with the filing requirements of the Securities and Exchange
Commission as set forth in such Rule, as such Rule may be amended from time to
time.

10.  REPRESENTATIONS AND COVENANTS OF THE WARRANTHOLDER.
     --------------------------------------------------

     This warrant Agreement has been entered into by the Company in reliance
upon the following representations and covenants of the Warrantholder:

     (a)   Investment Purpose.  The right to acquire Preferred Stock or the
           ------------------
Preferred Stock issuable upon exercise of the Warrantholder's rights contained
herein will be acquired for investment and not with a view to the sale or
distribution of any part thereof, and the Warrantholder has no present intention
of selling or engaging in any public distribution of the same except pursuant to
a registration or exemption.

     (b)   Private Issue.  The Warrantholder understands (i) that the Preferred
           -------------
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 Agreement will be exempt from the
registration and qualifications requirements thereof, and

                                       7
<PAGE>

(ii) that the Company's reliance on such exemption is predicated on the
representations set forth in this Section 10.

     (c)   Disposition of Warrantholder's Rights.  In no event will the
           -------------------------------------
Warrantholder make a disposition of any of its rights to acquire Preferred Stock
or Preferred Stock issuable upon exercise of such rights 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
Warrantholder) 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 Preferred Stock or Preferred
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 an to any particular
share of Preferred 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 Warrantholder at its request by the staff of the Securities and
Exchange Commission or a ruling shall have been issued to the Warrantholder 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
Warrantholder or holder of a share of Preferred 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 Preferred Stock not bearing any restrictive
legend.

     Notwithstanding anything to the contrary contained herein:

     (i)   The Warrantholder shall not sell or transfer or agree to sell or
transfer any rights to acquire shares of stock of the Company or any shares of
stock of the Company (collectively, the "Offered Shares"), unless in each case
the Warrantholder shall have first complied with this Section 10 (c).  The
Warrantholder shall deliver to the Company a written notice of any proposed or
intended sale of Offered Shares (the "Offer"), which Offer shall (a) identify
the Offered Shares, (b) describe the price and other terms upon which they are
to be sold or transferred, and the number or amount of the Offered Shares to be
sold or transferred, and (c) offer to sell to the Company all (but not less than
all) such Offered Shares.  The Company shall have the right, for a period of
five (5) days following delivery of the Offer, to purchase or acquire, at a
price and upon the other terms specified in the Offer, any and all Offered
Shares described above.  The Offer by its term shall remain open and irrevocable
for such 5-day period.

     (ii)  To accept an offer, the Company must deliver a written notice to the
Warrantholder prior to the and of the 5-day period of the Offer (the "Notice of
Acceptance").  If the Company does not accept the Offer, the Warrantholder may
sell the Offered Shares on the terms and conditions set forth in the Offer for a
period of forty-five (45) days following the end of the 5-day period of the
Offer.

                                       8
<PAGE>

     (iii)  Any Offered Shares not acquired by the Company or other persons in
accordance with this Section 10 (c) may not be issued, sold or exchanged until
they are again offered to the Company under the procedures specified in this
Agreement.

     (iv)   The provisions of this Section 10 (c) shall terminate upon the
closing of the Company's initial public offering of shares of Common Stock
pursuant to an effective registration statement under the Securities Act.

     (d)    Financial Risk.  The Warrantholder has such knowledge and experience
            --------------
in financial and business matters and in investing in companies similar to the
Company 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)    Authority.  The Warrantholder has full power and authority to enter
            ---------
into and to perform this Agreement in accordance with its terms.  The
Warrantholder has not been organized, reorganized or recapitalized specifically
for the purpose of investing in the company.

     (f)   Risk of No Registration.  The Warrantholder 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 rights to purchase Preferred Stock pursuant to this Warrant
Agreement, or (ii) the Preferred Stock issuable upon exercise of the right to
purchase, it may be required to hold such securities for an indefinite period.
The Warrantholder also understands that any sale of its rights of the
Warrantholder to purchase Preferred Stock or Preferred Stock 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.

11.  TRANSFERS.
     ---------

     (a)   Subject to the terms and conditions contained in section 10 hereof,
this Warrant Agreement and all rights hereunder are transferable in whole or in
part by the Warrantholder and any successor transferee, provided, however, in no
event shall the number of transfers of the rights and interests in all of the
Warrants exceed three (3) transfers.  The transfer shall be recorded on the
books of the Company upon receipt by the Company of a notice of transfer in the
form attached hereto as Exhibit II (the "Transfer Notice"), at its principal
offices and the payment to the Company of all transfer taxes and other
governmental charges imposed on such transfer.

     (b)   Legends.  Each certificate or agreement representing rights to
           -------
acquire shares of Preferred Stock, Preferred Stock issuable upon the exercise of
such rights or shares of Common Stock issuable upon the conversion of the
Preferred Stock shall bear a legend substantially in the following form:

          "The securities represented by this certificate have not been
          registered under the Securities Act of 1933, as amended, and may not
          be offered, sold or otherwise transferred, pledged or hypothecated
          unless and until such shares are registered under such Act, or an
          opinion of counsel satisfactory to the Company is obtained to the
          effect that such registration is not required."

                                       9
<PAGE>

     The foregoing legend shall be removed from the certificates representing
any Restricted Shares, at the request of the holder thereof, at such time as
they become eligible for resale pursuant to Rule 144 under the Securities Act.

     (c)  If any of the provisions set forth in this Agreement are violated, the
Company shall not be required (i) to transfer on its books any of the rights to
acquire shares of Preferred Stock, Preferred Stock issuable upon the exercise of
such rights or shares of Common Stock issuable upon the conversion of the
Preferred Stock, or (ii) to treat an owner of such rights to acquire shares of
Preferred Stock, Preferred Stock issuable upon the exercise of such rights or
shares of Common Stock issuable upon the conversion of the Preferred Stock or to
pay dividends to any transferee to whom any such rights to acquire shares of
Preferred Stock, Preferred Stock issuable upon the exercise of such rights or
shares of Common Stock issuable upon the conversion of the Preferred Stock shall
have been so sold or transferred.

12.  MISCELLANEOUS.
     -------------

     (a)  Effective Date.  The provisions of this Warrant Agreement shall be
          --------------
construed and shall be given effect in all respects as if it had been executed
and delivered by the Company on the date hereof.  This Warrant Agreement shall
be binding upon any successors or assigns of the Company.

     (b)  Attorney's Fees.  In any litigation, arbitration or court proceeding
          ---------------
between the Company and the Warrantholder relating hereto, the prevailing party
shall be entitled to attorneys' fees and expenses and all costs of proceedings
incurred in enforcing this Warrant Agreement.

     (c)  Governing Law.  This Warrant Agreement shall be governed by and
          -------------
construed for all purposes under and in accordance with the laws of the State of
Illinois.

     (d)  Counterparts.  This Warrant Agreement may be executed in two or more
          ------------
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     (e)  Notices.  Any notice required or permitted hereunder shall be given in
          -------
writing and shall be deemed effectively given upon personal delivery, facsimile
transmission (provided that the original is sent by personal delivery or mail as
hereinafter set forth) or seven (7) days after deposit in the United States
mail, by registered or certified mail, addressed (i) to the Warrantholder at
6111 North River Road, Rosemont, Illinois 60018, attention:  James Labe, Venture
Leasing Director, cc:  Legal Department, (and/or, if by facsimile, (708) 518-
5465 and (ii) to the Company c/o Greylock Management Corporation, One Federal
Street, Boston, MA 02110, (and/or if by facsimile, (617) 482-0059 or at such
other address as any such party may subsequently designate by written notice to
the other party.

     (f)  Remedies.  In the event of any default hereunder, the non-defaulting
          --------
party may proceed to protect and enforce its rights either by suit in equity
and/or by action at law, including but not limited to an action for damages as a
result of any such default, and/or an action for specific performance for any
default where Warrantholder will not have an adequate remedy at law and where
damages will not be readily ascertainable.

                                       10
<PAGE>

     (g)  No Impairment of Rights.  The Company will not, by amendment of its
          -----------------------
Charter or through any other means, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
actions an may be necessary or appropriate in order to protect the rights of the
Warrantholder against impairment.  Any and all costs incurred by the company in
assisting the Warrantholder in the protection of the Warrantholder's rights
shall be paid for, or reimbursed, by the Warrantholder.

     (h)  Survival.  The representations, warranties, covenants and conditions
          --------
of the respective parties contained herein or made pursuant to this Warrant
Agreement shall survive the execution and delivery of this Warrant Agreement.

     (i)  Severability.  In the event any one or more of the provisions of this
          ------------
Warrant Agreement shall for any reason be hold invalid, illegal or
unenforceable, the remaining provisions of this Warrant Agreement shall be
unimpaired, and the invalid, illegal or unenforceable provision shall be
replaced by a mutually acceptable valid, legal and enforceable provision, which
comes closest to the intention of the parties underlying the invalid, illegal or
unenforceable provision.

     (j)  Amendments.  Any provision of this Warrant Agreement may be amended by
          ----------
a written instrument signed by the Company and by the Warrantholder.

     (k)  Additional Documents.  The Company, upon execution of this Warrant
          --------------------
Agreement, shall provide the Warrantholder with certified resolutions with
respect to the representations, warranties and covenants set forth in
subparagraphs (a) through (d), (f) and (g) of Section 9 above.  The Company
shall also supply such other documents as the Warrantholder may from time to
time reasonably request.

     IN WITNESS WHEREOF, the parties hereto have caused this Warrant Agreement
to be executed by its officers thereunto duly authorized as of the Effective
Date.

                              Company:  ONTOGENY, INC.



                              By:_________________________________

                              Title:______________________________


                              Warrantholder:  COMDISCO, INC.


                              By:_________________________________

                              Title:______________________________

                                       11
<PAGE>

                                   EXHIBIT I

                               NOTICE OF EXERCISE

To:  ___________________________

(1)  The undersigned Warrantholder hereby elects to purchase ________ shares of
     the Preferred Stock of ________________ pursuant to the terms of the
     Warrant Agreement dated the _________ day of ___________, 19__ (the
     "Warrant Agreement") between ____________________ and the Warrantholder,
     and tenders herewith payment of the purchase price for such shares in full,
     together with all applicable transfer taxes, if any.

(2)  In exercising its rights to purchase the Preferred Stock of
     ________________, the undersigned hereby confirms and acknowledges the
     investment representations and warranties made in Section 10 of the Warrant
     Agreement.

(3)  Please issue a certificate or certificates representing said shares of
     Preferred Stock in the name of the undersigned or in such other name as is
     specified below.


________________________________
(Name)

________________________________
(Address)

Warrantholder:  COMDISCO, INC.

By:______________________________

Title:____________________________

Date:____________________________

                                       12
<PAGE>

                          ACKNOWLEDGEMENT OF EXERCISE

     The undersigned _______________________________________ hereby acknowledge
receipt of the "Notice of Exercise" from Comdisco, Inc., to purchase shares of
the Preferred Stock _______ of ____________________________, pursuant to the
terms of the Warrant Agreement, and further acknowledges that ________ shares
remain subject to purchase under the terms of the Warrant Agreement.

                              Company:

                              By:________________________________

                              Title:_____________________________

                              Date:______________________________

                                       13
<PAGE>

                                   EXHIBIT II

                                TRANSFER NOTICE

     (To transfer or assign the foregoing Warrant Agreement execute this form
     and supply required information.  Do not use this form to purchase shares.)

     FOR VALUE RECEIVED,, the foregoing Warrant Agreement and all rights
evidenced thereby are hereby transferred and assigned to

_______________________________________________________________________________
     (Please Print)

whose address is_______________________________________________________________

_______________________________________________________________________________

          Dated________________________________________________________________

          Holder's Signature___________________________________________________

          Holder's Address_____________________________________________________

          _____________________________________________________________________

Signature Guaranteed:__________________________________________________________

     NOTE:     The signature to this Transfer Notice must correspond with the
               name as it appears on the face of the Warrant Agreement, without
               alteration or enlargement or any change whatever. Officers of
               corporations and those acting in a fiduciary or other
               representative capacity should file proper evidence of authority
               to assign the foregoing Warrant Agreement.

                                       14