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                               SECURED PROMISSORY NOTE


$150,000                                                        January 8, 1999

     FOR VALUE RECEIVED, the undersigned (the "Maker") hereby promises to pay on
or before January 8, 2003 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 Fifty Thousand
Dollars ($150,000), together with interest on the unpaid principal balance
thereof from the date hereof at the rate of Four and Forty Four One-Hundredth
Percent (4.44%) 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.  Interest shall be payable quarterly with
the first interest payment due three months from the date hereof and additional
interest payment due on the same date of each three-month period thereafter
until this Note, including all interest and principal, is paid in full.  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.
     
     The principal balance of this Note shall be forgiven to the extent
hereinafter provided.  So long as Maker remains an employee of Payee pursuant to
the certain Letter of Agreement dated as of November 6, 1998, by and between
Maker and Payee ("Employment Agreement"), the amount of Nine Thousand Three
Hundred and Seventy Five Dollars ($9,375) of the unpaid principal balance shall
be forgiven each quarter commencing on the last day of a period ending three (3)
months from the date hereof and continuing quarterly on the last day of each
successive three-month period thereafter until either the loan is totally
forgiven or the total amount of the forgiveness and principal paid in lawful
money equals the original principal amount of this Note.  In addition to the
foregoing, the entire amount of the unpaid principal balance shall be forgiven
upon a "Change in Control" as defined for the purposes of the Payee's 1996 Stock
Incentive Plan as the same is in effect on the date hereof.
     
     This Note is a full-recourse note originally secured by a pledge of all
options and rights of Maker to acquire the Common Stock of the Payee (the
"COMMON STOCK"), however and whenever acquired, together with any shares of
Common Stock otherwise issuable to Maker upon the exercise of any such options
or pursuant to any such rights, all as more fully set forth in that certain
Security Agreement of even date herewith executed by Maker in favor of Payee and
which is on file with the Secretary of Payee; PROVIDED, HOWEVER, that if the
Common Stock is publicly traded on the New York Stock Exchange or quoted on the
Nasdaq National Market at the time such shares of Common Stock would otherwise
be issuable to Maker, then an amount of such shares representing the value of
such shares, if any, in excess of one hundred fifty percent (150%) of the then
outstanding principal balance of this Note shall be released to Maker at such
time (based upon the average of the last trading price of the Common Stock over
the ten trading day period immediately preceding the time such shares would
otherwise be issuable to Maker).

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     The entire unpaid and unforgiven principal balance of this Note plus
accrued interest shall become due and payable ten (10) days from the date Maker
ceases to be an employee of Payee under the Employment Agreement 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
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 not 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.

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     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/ Michael G. Grey           
                                   ---------------------
                                   Michael G. Grey
     
     APPROVED BY:
     
Written Consent by Compensation Committee on November 6, 1998.
     











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