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                                                                   EXHIBIT 10.12

               THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUED
                UPON ITS EXERCISE ARE SUBJECT TO THE RESTRICTIONS
               ON TRANSFER SET FORTH IN SECTION 4 OF THIS WARRANT
               --------------------------------------------------


Warrant No. ____                                          Number of Shares: ____
                                                         (subject to adjustment)
Date of Issuance: August 1, 1997


                          TRANSCEND THERAPEUTICS, INC.



                          Common Stock Purchase Warrant
                          -----------------------------

                           (Void after March 3, 2002)


         Transcend Therapeutics, Inc., a Delaware corporation (the "Company"),
for value received, hereby certifies that __________________________________
(the "Investor"), or its registered assigns (the "Registered Holder"), is
entitled, subject to the terms set forth below, to purchase from the Company, at
any time or from time to time on or after the date of issuance and on or before
March 3, 2002 at not later than 5:00 p.m. (Boston, Massachusetts time),
sixty-two (62) shares of Common Stock, $.01 par value per share, of the Company
at a purchase price of $10.00 per share. The shares purchasable upon exercise of
this Warrant, and the purchase price per share, each as adjusted from time to
time pursuant to the provisions of this Warrant, are hereinafter referred to as
the "Warrant Shares" and the "Purchase Price," respectively.

        1.      EXERCISE.

                (a)     This Warrant may be exercised by the Registered Holder,
in whole or in part, by surrendering this Warrant, with the purchase form
appended hereto as EXHIBIT I duly executed by such Registered Holder or by such
Registered Holder's duly authorized attorney, at the principal office of the
Company, or at such other office or agency as the Company may designate,
accompanied by payment in full, in lawful money of the United States, of the
Purchase Price payable in respect of the number of Warrant Shares purchased upon
such exercise.

                (b)     The Registered Holder may, at its option, elect to pay
some or all of the Purchase Price payable upon an exercise of this Warrant by
cancelling a portion of this Warrant exercisable for such number of Warrant
Shares as is determined by dividing (i) the total Purchase Price payable in
respect of the number



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of Warrant Shares being purchased upon such exercise by (ii) the excess of the
Fair Market Value per share of Common Stock as of the effective date of
exercise, as determined pursuant to subsection 1(c) below (the "Exercise Date")
over the Purchase Price per share. If the Registered Holder wishes to exercise
this Warrant pursuant to this method of payment with respect to the maximum
number of Warrant Shares purchasable pursuant to this method, then the number of
Warrant Shares so purchasable shall be equal to the total number of Warrant
Shares, minus the product obtained by multiplying (x) the total number of
Warrant Shares by (y) a fraction, the numerator of which shall be the Purchase
Price per share and the denominator of which shall be the Fair Market Value per
share of Common Stock as of the Exercise Date. The Fair Market Value per share
of Common Stock shall be determined as follows:

                        (i)     If the Common Stock is listed on a national
securities exchange, the Nasdaq National Market System, the Nasdaq system, or
another nationally recognized exchange or trading system as of the Exercise
Date, the Fair Market Value per share of Common Stock shall be deemed to be the
last reported sale price per share of Common Stock thereon on the Exercise Date;
or, if no such price is reported on such date, such price on the next preceding
business day provided that if no such price is reported on the next preceding
business day, the Fair Market Value per share of Common Stock shall be
determined pursuant to clause (ii)).

                        (ii)    If the Common Stock is not listed on a national
securities exchange, the Nasdaq National Market System, the Nasdaq system or
another nationally recognized exchange or trading system as of the Exercise
Date, the Fair Market Value per share of Common Stock shall be deemed to be the
amount most recently determined by the Board of Directors to represent the fair
market value per share of the Common Stock (including without limitation a
determination for purposes of granting Common Stock options or issuing Common
Stock under an employee benefit plan of the Company); and, upon request of the
Registered Holder, the Board of Directors (or a representative thereof) shall
promptly notify the Registered Holder of the Fair Market Value per share of
Common Stock. Notwithstanding the foregoing, if the Board of Directors has not
made such a determination within the three-month period prior to the Exercise
Date, then (A) the Fair Market Value per share of Common Stock shall be the
amount next determined by the Board of Directors to represent the fair market
value per share of the Common Stock (including without limitation a
determination for purposes of granting Common Stock options or issuing Common
Stock under an employee benefit plan of the Company), (B) the Board of Directors
shall make such a determination within 15 days of a request by the Registered
Holder that it do so, and (C) the exercise of this Warrant pursuant to this
subsection 1(b) shall be delayed until such determination is made.



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                (c)     Each exercise of this Warrant shall be deemed to have
been effected immediately prior to the close of business on the day on which
this Warrant shall have been surrendered to the Company as provided in
subsection 1(a) above. At such time, the person or persons in whose name or
names any certificates for Warrant Shares shall be issuable upon such exercise
as provided in subsection 1(d) below shall be deemed to have become the holder
or holders of record of the Warrant Shares represented by such certificates.

                (d)     As soon as practicable after the exercise of this
Warrant in full or in part, and in any event within 10 days thereafter, the
Company, at its expense, will cause to be issued in the name of, and delivered
to, the Registered Holder, or as such Holder (upon payment by such Holder of any
applicable transfer taxes) may direct:

                        (i)     a certificate or certificates for the number of
full Warrant Shares to which such Registered Holder shall be entitled upon such
exercise plus, in lieu of any fractional share to which such Registered Holder
would otherwise be entitled, cash in an amount determined pursuant to Section 3
hereof; and

                        (ii)    in case such exercise is in part only, a new
warrant or warrants (dated the date hereof) of like tenor, calling in the
aggregate on the face or faces thereof for the number of Warrant Shares equal
(without giving effect to any adjustment therein) to the number of such shares
called for on the face of this Warrant minus the sum of (a) the number of such
shares purchased by the Registered Holder upon such exercise plus (b) the number
of Warrant Shares (if any) covered by the portion of this Warrant cancelled in
payment of the Purchase Price payable upon such exercise pursuant to subsection
1(b) above.

        2.      ADJUSTMENTS.

                  (a) If outstanding shares of the Company's Common Stock shall
be subdivided into a greater number of shares or a dividend in Common Stock
shall be paid in respect of Common Stock, the Purchase Price in effect
immediately prior to such division or at the record date of such dividend shall
simultaneously with the effectiveness of such subdivision or immediately after
the record date of such dividend be proportionately reduced. If outstanding
shares of Common Stock shall be combined into a smaller number of shares, the
Purchase Price in effect immediately prior to such combination shall,
simultaneously with the effectiveness of such combination, be proportionately
increased. When any adjustment is required to be made in the Purchase Price, the
number of Warrant Shares purchasable upon the exercise of this Warrant shall be
changed to the number determined by dividing (i) an amount equal to the number
of shares issuable upon the exercise of this Warrant immediately prior to such
adjustment, multiplied by the Purchase Price in effect immediately prior to such
adjustment, by (ii) the Purchase Price in effect immediately after such
adjustment.



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                  (b) If there shall occur any capital reorganization or
reclassification of the Company's Common Stock (other than a change in par value
or a subdivision or combination as provided for in subsection 2(a) above), or
any consolidation or merger of the Company with or into another corporation, or
a transfer of all or substantially all of the assets of the Company, then, as
part of any such reorganization, reclassification, consolidation, merger or
sale, as the case may be, lawful provision shall be made so that the Registered
Holder of this Warrant shall have the right thereafter to receive upon the
exercise hereof the kind and amount of shares of stock or other securities or
property which such Registered Holder would have been entitled to receive if,
immediately prior to any such reorganization, reclassification, consolidation,
merger or sale, as the case may be, such Registered Holder had held the number
of shares of Common Stock which were the purchasable upon the exercise of this
Warrant. In any such case, appropriate adjustment (as reasonably determined in
good faith by the Board of Directors of the Company) shall be made in the
application of the provisions set forth herein with respect to the rights and
interests thereafter of the Registered Holder of this Warrant, such that the
provisions set forth in this Section 2 (including provisions with respect to
adjustment of the Purchase Price) shall thereafter be applicable, as nearly as
is reasonably practicable, in relation to any shares of stock or other
securities or property thereafter deliverable upon the exercise of this Warrant.

                (c)     When any adjustment is required to be made in the
Purchase Price, the Company shall promptly mail to the Registered Holder a
certificate setting forth the Purchase Price after such adjustment and setting
forth a brief statement of the facts requiring such adjustment. Such certificate
shall also set forth the kind and amount of stock or other securities or
property into which this Warrant shall be exercisable following the occurrence
of any of the events specified in subsection 2(a) or (b) above.

        3.      FRACTIONAL SHARES. The Company shall not be required upon the
exercise of this Warrant to issue any fractional shares, but shall make an
adjustment therefor in cash on the basis of the Fair Market Value per share of
Common Stock, as determined pursuant to subsection 1(b) above.

        4.      REQUIREMENTS FOR TRANSFER.

                (a)     This Warrant and the Warrant Shares shall not be sold or
transferred unless either (i) they first shall have been registered under the
Act, or (ii) the Company first shall have been furnished with an opinion of
legal counsel, reasonably satisfactory to the Company, to the effect that such
sale or transfer is exempt from the registration requirements of the Act.

                (b)     Notwithstanding the foregoing, no registration or
opinion of counsel shall be required for (i) a transfer by a Registered Holder
which is a



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partnership to a partner of such partnership or a retired partner of such
partnership who retires after the date hereof, or to the estate of any such
partner or retired partner, if the transferee agrees in writing to be subject to
the terms of this Section 4, or (ii) a transfer made in accordance with the Rule
144 under the Act.

                (c)     Each certificate representing Warrant Shares 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 securities 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."

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

        5.      NO IMPAIRMENT. The Company will not, by amendment of its charter
or through reorganization, consolidation, merger, dissolution, sale of assets or
any other voluntary action, 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 action as
may be necessary or appropriate in order to protect the rights of the holder of
this Warrant against impairment.

        6.      LIQUIDATING DIVIDENDS. If the Company pays a dividend or makes a
distribution on the Common Stock payable otherwise than in cash out of earnings
or earned surplus (determined in accordance with generally accepted accounting
principles) except for a stock dividend payable in shares of Common Stock (a
"Liquidating Dividend"), then the Company will pay or distribute to the
Registered Holder of this Warrant, upon the exercise hereof, in addition to the
Warrant Shares purchased upon such exercise, the Liquidating Dividend which
would have been paid to such Registered Holder if he had been the owner of
record of such Warrant Shares immediately prior to the date on which a record is
taken for such Liquidating Dividend or, if no record is taken, the date as of
which the record holders of Common Stock entitled to such dividends or
distribution are to be determined.

        7.      NOTICES OF RECORD DATE, ETC. In case:

                (a)     the Company shall take a record of the holders of its
Common Stock (or other stock or securities at the time deliverable upon the
exercise of this Warrant) for the purpose of entitling or enabling them to
receive any dividend or



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other distribution, or to receive any right to subscribe for or purchase any
shares of stock of any class or any other securities, or to receive any other
right; or

                (b)     of any capital reorganization of the Company, any
reclassification of the capital stock of the Company, any consolidation or
merger of the Company with or into another corporation (other than a
consolidation or merger in which the Company is the surviving entity), or any
transfer of all or substantially all of the assets of the Company; or

                (c)     of the voluntary or involuntary dissolution, liquidation
or winding-up of the Company,

then, and in each such case, the Company will mail or cause to be mailed to the
Registered Holder of this Warrant a notice specifying, as the case may be, (i)
the date on which a record is to be taken for the purpose of such dividend,
distribution or right, and stating the amount and character of such dividend,
distribution or right, or (ii) the effective date on which such reorganization,
reclassification, consolidation, merger, transfer, dissolution, liquidation or
winding-up is to take place, and the time, if any is to be fixed, as of which
the holders of record of Common Stock (or such other stock or securities at the
time deliverable upon the exercise of this Warrant) shall be entitled to
exchange their shares of Common Stock (or such other stock or securities) for
securities or other property deliverable upon such reorganization,
reclassification, consolidation, merger, transfer, dissolution, liquidation or
winding-up. Such notice shall be mailed at least ten (10) day prior to the
record date or effective date for the event specified in such notice.

        8.      RESERVATION OF STOCK. The Company will at all times reserve and
keep available, solely for issuance and delivery upon the exercise of this
Warrant, such number of Warrant Shares and other stock, securities and property,
as from time to time shall be issuable upon the exercise of this Warrant.

        9.      EXCHANGE OF WARRANTS. Upon the surrender by the Registered
Holder of any Warrant or Warrants, properly endorsed, to the Company at the
principal office of the Company, the Company will, subject to the provisions of
Section 4 hereof, issue and deliver to or upon the order of such Holder, at the
Company's expense, a new Warrant or Warrants of like tenor, in the name of such
Registered Holder or as such Registered Holder (upon payment by such Registered
Holder of any applicable transfer taxes) may direct, calling in the aggregate on
the face or faces thereof for the number of shares of Common Stock called for on
the face or faces of the Warrant or Warrants so surrendered.

        10.     REPLACEMENT OF WARRANTS. Upon receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant and (in the case of loss, theft or destruction) upon delivery of an
indemnity


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agreement (with surety if reasonably required) in an amount reasonably
satisfactory to the Company, or (in the case of mutilation) upon surrender and
cancellation of this Warrant, the Company will issue, in lieu thereof, a new
Warrant of like tenor.

        11.     TRANSFER, ETC.

                (a)     The Company will maintain a registered containing the
names and addresses of the Registered Holders of this Warrant. Any Registered
Holder may change its or his address as shown on the warrant register by written
notice to the Company requesting such change.

                (b)     Subject to the provisions of Section 4 hereof, this
Warrant and all rights hereunder are transferable, in whole or in part, upon
surrender of this Warrant with a properly executed assignment (in the form of
EXHIBIT II hereto) at the principal office of the Company.

                (c)     Until any transfer of this Warrant is made in the
warrant register, the Company may treat the Registered Holder of this Warrant as
the absolute owner hereof for all purposes; PROVIDED, HOWEVER, that if and when
this Warrant is properly assigned in blank, the Company may (but shall not be
obligated to) treat the bearer hereof as the absolute owner hereof for all
purposes, notwithstanding any notice to the contrary.

        12.     REGISTRATION RIGHTS. The shares of Common Stock issuable upon
exercise of this Warrant shall have the registration rights set forth in the
Third Amended and Restated Registration Rights Agreement dated June 13, 1997
between the Company and certain investors listed on the signatures pages
thereof.

        13.     MAILING OF NOTICES, ETC. All notices and other communications
from the Company to the Registered Holder of this Warrant shall be mailed by
first-class certified or registered mail, postage prepaid, to the address
furnished to the Company in writing by the last Registered Holder of this
Warrant who shall have furnished an address to the Company in writing. All
notices and other communications from the Registered Holder of this Warrant or
in connection herewith to the Company shall be mailed by first-class certified
or registered mail, postage prepaid, to the Company at its principal office set
forth below. If the Company should at any time change the location of its
principal office to a place other than as set forth below, it shall give prompt
written notice to the Registered Holder of this Warrant and thereafter all
references in this Warrant to the location of its principal office at the
particular time shall be as so specified in such notice.

        14.     NO RIGHTS AS STOCKHOLDER. Until the exercise of this Warrant,
the Registered Holder of this Warrant shall not have or exercise any rights by
virtue hereof as a stockholder of the Company.



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        15.     CHANGE OR WAIVER. This Warrant is one of a series of Warrants
issued by the Company, all dated the date hereof and of like tenor, except as to
the number of shares of Common Stock subject thereto (collectively, the "Company
Warrants"). Any term of this Warrant may be amended or waived upon the written
consent of the Company and the holders of Company Warrants representing at least
66 2/3 % of the number of shares of Common Stock then subject to outstanding
Company Warrants; PROVIDED that any such amendment or waiver must apply to all
Company Warrants then outstanding; and PROVIDED FURTHER that the number of
Warrant Shares subject to this Warrant and the Purchase Price of this Warrant
may not be amended, and the right to exercise this Warrant may not be waived,
without the written consent of the holder of this Warrant (it being agreed that
an amendment to or waiver under any of the provisions of Section 2 of this
Warrant shall not be considered an amendment of the number of Warrant Shares or
the Purchase Price).

        16.     HEADINGS. The headings in this Warrant are for purposes of
reference only and shall not limit or otherwise affect the meaning of any
provision of this Warrant.

        17.     GOVERNING LAW. This Warrant will be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts.



                              TRANSCEND THERAPEUTICS, INC.
                              640 Memorial Drive
                              Cambridge, MA 02139

                              By:
                                 ---------------------------------------------
                                 Name: Hector J. Gomez, M.D., Ph.D
                                 Title: President and Chief Executive Officer



[Corporate Seal]

ATTEST:

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




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                                                                       Exhibit I
                                                                       ---------

                                  PURCHASE FORM
                                  -------------



TO:  Transcend Therapeutics, Inc.                      Dated:  ________________


        The undersigned, pursuant to the provisions set forth in the attached
Warrant No. __ hereby irrevocably elects to purchase _____ shares of the Common
Stock covered by such Warrant. The undersigned herewith makes payment of
$_______, representing the full purchase price for such shares at the price per
share provided for in such Warrant. Such payment takes the form of (check
applicable box or boxes):


                  [ ]  $__________ in lawful money of the United States, and/or

                  [ ]  the cancellation of such portion of the attached Warrant
                       is as exercisable for a total of ________ Warrant Shares
                       (using a Fair Market Value of $__________ per share for
                       purposes of this calculation).


                                 Signature:__________________________________

                                 Address:____________________________________

                                         ____________________________________








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                                                                      Exhibit II
                                                                      ----------


                                 ASSIGNMENT FORM
                                 ---------------


         FOR VALUE RECEIVED, ______________________ hereby sells, assigns and
transfers all of the rights of the undersigned under the attached Warrant No. __
with respect to the number of shares of Common Stock covered thereby set forth
below, unto:


Name of Assignee                Address                     No. of Shares




Dated:______________________________     Signature:___________________________

Dated:______________________________     Witness:_____________________________