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                               SECURED PROMISSORY NOTE

$120,000                                                       February 1, 1999

     FOR VALUE RECEIVED, the undersigned (the "Maker") hereby promises to pay 
on or before February 1, 2001 to the order of Trega Biosciences, Inc., (the 
"Payee") at its principal offices currently located at 9880 Campus Point 
Drive, San Diego, California  92121, the principal amount of One Hundred 
Twenty Thousand Dollars ($120,000), together with interest on the unpaid 
principal balance thereof from the date hereof at the rate of four and 
sixty-four one-hundredth percent (4.64%) per annum simple interest, subject 
to the terms and conditions hereinafter provided.

     Payment of this Note shall be made in lawful money of the United States of
America at the Office of the Payee.  Principal and interest shall be payable in
full on or before February 1, 2001.  Payment of principal and accrued interest
may be made at any time without penalty.

     The Maker waives presentment, demand for payment, notice of dishonor,
notice of protest, and all other notices or demands in connection with delivery,
acceptance, performance, default, endorsement or guarantee of this Note.

     This Note is a full-recourse note originally secured by a pledge of One
Hundred Twenty Thousand (120,000) shares of the Common Stock of the Payee (the
"Common Stock") owned by the Maker, all as more fully set forth in that certain
pledge as Security Agreement of even date herewith executed by Maker in favor of
Payee and which is on file with the Secretary of Payee.
 
     The entire unpaid principal balance of this Note plus accrued interest
shall become due and payable six-months from the date Maker ceases to be an
employee of Payee and immediately due and payable upon the occurrence of any one
of the following events of default.

     1.   Any principal or interest under this Note shall not be paid when due;
          or
     2.   Maker files a petition in bankruptcy, makes a general assignment for
          the benefit of creditors, or commits any act of bankruptcy; or
     3.   Any proceeding of an insolvency nature is commenced against the Maker
          and such proceedings is not dismissed within thirty (30) days
          thereafter; or
     4.   Any collateral which is securing this Note is attached, seized,
          subjected to writ levied upon or comes within the possession of any
          receiver, trustee, custodian or assignee for the benefit of creditors;
          or
     5.   Any notice of lien, levy or assessment is filed or recorded with
          respect to any collateral which is securing this Note by any federal,
          state, county, local or other governmental agency unless Maker is
          contesting in good faith, or for so long as Maker continues to so
          contest such notice.

     The liability of Maker hereunder shall be unconditional and shall not be in
any manner affected by any indulgence whatsoever granted or consented to by the
Payee including, without limitation, any extension of time, renewal, waiver or
other modification.  Any failure of the Payee to exercise any right hereunder
shall not be construed as a waiver of the right to exercise the same or of any
other right at any time and from time to time.  The Maker hereby irrevocably


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submits to the jurisdiction of the state courts of the State of California 
for the purpose of any suit, action or other proceeding arising out of this 
Note.

     In the event this Note shall not be promptly paid when due, the Maker shall
pay all costs of enforcement and collection of the Note, including without
limitation reasonable attorney's fees, expenses and court costs.

     Any provisions of this Note which may prove unenforceable under any law
shall not affect the validity or enforceability of any other provision hereof.

     This Note may be assigned, transferred or pledged without the consent of
the Maker.  In the event this Note is assigned, transferred or pledged, the
Maker hereby waives, as against such transferee, assignee or pledgee, any
defenses and counterclaims of every kind that the Maker may have against the
Payee.

     This Note shall be governed by and construed in accordance with the laws of
the State of California as such laws are applied to contracts entered into and
to be performed entirely within California.

                                             MAKER:



                                            /s/ John E. Wehrli
                                            ---------------------
                                            John E. Wehrli


Approved by:



/s/ Michael G. Grey 
--------------------------------
Michael G. Grey
President and Chief Executive Officer



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