<PAGE>   1

                                                                  Exhibit 10.80


                                  EPIMMUNE INC.
                            RESTRICTED STOCK PURCHASE

                                    AGREEMENT


        EPIMMUNE INC. (the "Company") wishes to sell to you, and you wish to
purchase, shares of the Company's Common Stock (the "Common Stock") from the
Company pursuant to the provisions of this Restricted Stock Purchase Agreement,
dated January 16, 2001 ("Agreement"). Certain capitalized terms in the Agreement
are defined on Exhibit A attached hereto.

        The parties hereto agree as follows:

        1. PURCHASE AND SALE OF STOCK. You hereby agree to purchase from the
Company, and the Company hereby agrees to sell to you, an aggregate of one
million fifty-six thousand three hundred one (1,056,301) shares of the Common
Stock of the Company (the "Stock") at two dollars and fifty cents (US $2.50) per
share (the "Price Per Share"), for an aggregate purchase price of two million
six hundred forty thousand seven hundred fifty-two dollars and fifty cents (US
$2,640,752.50), payable by promissory note.

        2. CLOSING. The closing hereunder, including payment for and delivery of
the Stock shall occur at the offices of the Company immediately following the
execution of this Agreement, or at such other time and place as the parties may
mutually agree. At the closing you shall deliver the following documents:

            (a) Two executed copies of the Assignment Separate From Certificate
(with date and number of shares blank) substantially in the form attached hereto
as Exhibit B and executed Joint Escrow Instructions substantially in the form
attached hereto as Exhibit C, along with the certificate or certificates
evidencing the Stock, for use by the Escrow Agent pursuant to the terms of the
Joint Escrow Instructions.

           (b) Promissory note in substantially the form attached hereto as
Exhibit D and an executed pledge agreement in substantially the form attached
hereto as Exhibit E (the "Pledge Agreement"), along with the certificate or
certificates evidencing the Stock, for use by the Escrow Agent pursuant to the
terms of the Joint Escrow Instructions.

        3. VESTING. Subject to the limitations contained herein, the Stock will
vest ratably in equal daily installments over a period of four (4) years from
the date of this Agreement such that one hundred percent (100%) of the Stock
will be vested at the end of such four (4) year period, provided that vesting
will cease upon the termination of your Continuous Service.

        4. RESTRICTIONS ON TRANSFER. You agree that the Company (or a
representative of the underwriters) may, in connection with an underwritten
registration of the offering of any securities of the Company under the
Securities Act, require that you not sell, dispose of, transfer, make any short
sale of, grant any option for the purchase of, or enter into any hedging or
similar transaction with the same economic effect as a sale, any shares of
Common Stock or other securities of the Company held by you under this
Agreement, for a period of time specified by



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the underwriter(s) (not to exceed one hundred eighty (180) days) following the
effective date of the registration statement of the Company filed under the
Securities Act. You further agree to execute and deliver such other agreements
as may be reasonably requested by the Company and/or the underwriter(s) that are
consistent with the foregoing or that are necessary to give further effect
thereto. In order to enforce the foregoing covenant, the Company may impose
stop-transfer instructions with respect to your Common Stock until the end of
such period.

        5. PURCHASE OPTION. The Company shall have the right (the "Purchase
Option") to purchase all or any part of the Stock received pursuant to this
Agreement that has not as yet vested in accordance with the vesting schedule set
forth in Section 3 of this Agreement ("Unvested Shares") on the following terms
and conditions:

           (a) The Company shall, simultaneously with termination of your
Continuous Service, purchase at the Price Per Share all of the Unvested Shares,
unless the Company agrees to waive its Purchase Option as to some or all of the
Unvested Shares. Any such waiver shall be exercised by the Company by written
notice to you or your representative (with a copy to the Escrow Agent) within
ninety (90) days after the termination of your Continuous Service, and the
Escrow Agent may then release to you the number of Unvested Shares not being
reacquired by the Company. If the Company does not waive its Purchase Option as
to all of the Unvested Shares, then upon such termination of your Continuous
Service, the Escrow Agent shall transfer to the Company the number of Unvested
Shares the Company is purchasing.

           (b) The Company shall pay for the purchase of any Unvested Shares
with respect to which it exercises its Purchase Option in cash or by
cancellation of purchase money indebtedness within ninety (90) days after the
termination of your Continuous Service.

           (c) The Stock issued under this Agreement shall be held in escrow
pursuant to the terms of the Joint Escrow Instructions attached hereto as
Exhibit C.

        6. ADJUSTMENTS TO STOCK. If, from time to time, during the term of the
Purchase Option there is any change affecting the Company's outstanding Common
Stock as a class that is effected without the receipt of consideration by the
Company (through merger, consolidation, reorganization, reincorporation, stock
dividend, dividend in property other than cash, stock split, liquidating,
dividend, combination of shares, change in corporation structure or other
transaction not involving the receipt of consideration by the Company), then any
and all new, substituted or additional securities or other property to which you
are entitled by reason of your ownership of Stock shall be immediately subject
to the Purchase Option and be included in the word "Stock" for all purposes of
the Purchase Option with the same force and effect as the shares of the Stock
presently subject to the Purchase Option, but only to the extent the Stock is,
at the time, covered by such Purchase Option. The Price Per Share of Stock upon
exercise of the Purchase Option shall be appropriately adjusted. The Company's
Board of Directors shall make such adjustments and its determination shall be
final, binding and conclusive (the conversion of any convertible securities of
the Company shall not be treated as a transaction "without receipt of
consideration" by the Company).


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        7. CHANGE IN CONTROL.

           (a) In the event (a) your employment is terminated by the Company or
its successor without Cause or if you resign from the Company with Good Reason
following a Change in Control and (b) within ninety (90) days after the
termination of your employment with the Company you furnish to the Company or
its successor an executed release and waiver of claims in substantially the form
attached to your offer letter dated January 16, 2001, then the Purchase Option
shall terminate and all of the Stock subject to the Purchase Option shall be
fully vested and released from the Purchase Option.

           (b) In the event of a Change in Control, then the Purchase Option may
be assigned by the Company to any successor of the Company (or the successor's
parent) in connection with such Change in Control. To the extent that the
Purchase Option remains in effect following such a Change in Control, it shall
apply to the new capital stock or other property received in exchange for the
Stock in consummation of the Change in Control, but only to the extent the Stock
is at the time subject to such Purchase Option. Appropriate adjustments shall be
made to the Price Per Share payable upon exercise of the Purchase Option to
reflect the effect of the Change in Control upon the Company's capital
structure.

        8. PARACHUTE PAYMENTS. In the event that any payments and other benefits
provided for in this Agreement or otherwise payable to you (the "Benefits")
would (i) constitute "parachute payments" within the meaning of Section 280G of
the Internal Revenue Code of 1986, as amended (the "Code"), and (ii) but for
this subsection would be subject to the excise tax imposed by Section 4999 of
the Code (the "Excise Tax"), then, the Benefits to which you are entitled
pursuant to this Agreement shall be either:

           (a) Provided to you in full, or

           (b) Provided to you at such lesser extent that would result in no
portion of the Benefits being subject to the Excise Tax, whichever of the
foregoing amounts, when taking into account applicable federal, state, local and
foreign income and employment taxes, the Excise Tax, and any other applicable
taxes, results in the receipt by you, on an after tax basis, of the greatest
amount of the Benefits, notwithstanding that all or some portion of the Benefits
may be taxable under the Excise Tax. Unless you and the Company otherwise agree
in writing, any determination required under this subsection shall be made in
writing in good faith by an accountant selected by you. In the event of a
reduction of the Benefits under this Agreement, you shall be given the choice of
which of the Benefits to reduce. For purposes of making the calculations
required by this subsection, the accountant that you select may make reasonable
assumptions and approximations concerning applicable taxes and may rely on
reasonable, good faith interpretations concerning the application of the Code,
and other applicable legal authority. You and the Company shall furnish your
accountant such information and documents as he may reasonably request in order
to make a determination under this subsection.



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           Any payment and benefits received by you upon a Change in Control
shall be in lieu of any other severance payment to you, including the severance
payment provided in subsection 7 herein. In the event that you become entitled
to payment and benefits upon a Change in Control, the Company shall have no
further obligation to pay you any base salary, bonus or other compensation or
benefits under this Agreement, except for benefits due to you (or your
dependents) under the terms of your benefit plans.

        9. RESTRICTIVE LEGENDS. The shares issued under this Agreement shall be
endorsed with appropriate legends determined by the Company, including but not
limited to the following legends:

        THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO AN OPTION SET
FORTH IN AN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER, OR SUCH
HOLDER'S PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT THE PRINCIPAL
OFFICE OF THIS COMPANY. ANY TRANSFER OR ATTEMPTED TRANSFER OF ANY SHARES SUBJECT
TO SUCH OPTION IS VOID WITHOUT THE PRIOR EXPRESS WRITTEN CONSENT OF THE COMPANY.

        THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933 AS AMENDED. THEY MAY NOT BE SOLD, OFFERED FOR
SALE, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION
STATEMENT AS TO THE SECURITIES UNDER SAID ACT OR AN OPINION OF COUNSEL
SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.

        10. INVESTMENT REPRESENTATIONS. In connection with the purchase of the
Stock, you represent to the Company the following:

            (a) You are aware of the Company's business affairs and financial
condition and have acquired sufficient information about the Company to reach an
informed and knowledgeable decision to acquire the Stock. You are purchasing the
Stock for investment for your own account only and not with a view to, or for
resale in connection with, any "distribution" thereof within the meaning of the
Securities Act.

            (b) You understand that the Stock has not been registered under the
Act by reason of a specific exemption therefrom, which exemption depends upon,
among other things, the bona fide nature of your investment intent as expressed
herein.

            (c) You further acknowledge and understand that the Stock must be
held indefinitely unless the Stock is subsequently registered under the
Securities Act or an exemption from such registration is available.

            (d) You are familiar with the provisions of Rule 144 under the Act,
as in effect from time to time, which, in substance, permit limited public
resale of "restricted securities" acquired, directly or indirectly, from the
issuer thereof (or from an affiliate of such


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<PAGE>   5


issuer), in a non-public offering subject to the satisfaction of certain
conditions. The Stock may be resold by you in certain limited circumstances
subject to the provisions of Rule 144, which requires, among other things: (i)
the availability of certain public information about the Company and (ii) the
resale occurring following the required holding period under Rule 144 after you
have purchased, and made full payment of (within the meaning of Rule 144), the
securities to be sold.

            (e) You further warrant and represent that you have either (i)
preexisting personal or business relationships, with the Company or any of its
officers, directors or controlling persons, or (ii) the capacity to protect your
own interests in connection with the purchase of the Stock by virtue of your
business or financial expertise or of your professional advisors who are
unaffiliated with and who are not compensated by the Company or any of its
affiliates, directly or indirectly.

        11. AGREEMENT NOT A SERVICE CONTRACT. This Agreement is not an
employment or service contract, and nothing in this Agreement shall be deemed to
create in any way whatsoever any obligation on your part to continue in the
employ of the Company or an Affiliate, or on the part of the Company or an
Affiliate to continue your employment. In addition, nothing in this Agreement
shall obligate the Company or an Affiliate, their respective stockholders,
boards of directors, Officers or Employees to continue any relationship that you
might have as a Director or Consultant for the Company or an Affiliate.

        12. WITHHOLDING OBLIGATIONS.

            (a) Upon the execution of this Agreement, or at any time thereafter
as requested by the Company, you hereby authorize withholding from payroll and
any other amounts payable to you, and otherwise agree to make adequate provision
for any sums required to satisfy the federal, state, local and foreign tax
withholding obligations of the Company or an Affiliate, if any, which arise in
connection with this Agreement.

            (b) Unless the tax withholding obligations of the Company and/or any
Affiliate are satisfied, the Company shall have no obligation to issue a
certificate for such shares or release such shares from any escrow provided for
herein.

        13. TAX CONSEQUENCES. The acquisition and vesting of the Stock may have
adverse tax consequences to you that may be avoided or mitigated by filing an
election under Section 83(b) of the Code. Such election must be filed within
thirty (30) days after the date you purchase the shares pursuant to this
Agreement. YOU ACKNOWLEDGE THAT IT IS YOUR OWN RESPONSIBILITY, AND NOT THE
COMPANY'S, TO FILE A TIMELY ELECTION UNDER CODE SECTION 83(B), EVEN IF YOU
REQUEST THE COMPANY TO MAKE THE FILING ON YOUR BEHALF.

        14. NOTICES. Any notices provided for in this Agreement shall be given
in writing and shall be deemed effectively given upon receipt or, in the case of
notices delivered by the Company to you, five (5) days after deposit in the
United States mail, postage prepaid, addressed to you at the last address you
provided to the Company.



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<PAGE>   6

        15. MISCELLANEOUS.

            (a) SUCCESSORS AND ASSIGNS. This Agreement shall inure to the
benefit of the successors and assigns of the Company and, subject to the
restrictions on transfer herein set forth, be binding upon you, your successors,
and assigns. The Purchase Option of the Company hereunder shall be assignable by
the Company at any time or from time to time, in whole or in part. Your rights
and obligations under this Agreement may only be assigned with the prior written
consent of the Company.

           (b) ATTORNEYS' FEES; SPECIFIC PERFORMANCE. You shall reimburse the
Company for all costs incurred by the Company in enforcing the performance of,
or protecting its rights under, any part of this Agreement, including reasonable
costs of investigation and attorneys' fees. It is the intention of the parties
that the Company, upon exercise of the Purchase Option and payment of the
purchase price for any Unvested Shares purchased upon exercise of the Purchase
Option, pursuant to the terms of this Agreement, shall be entitled to receive
the Stock, in specie, in order to have such Stock available for future issuance
without dilution of the holdings of other stockholders. Furthermore, it is
expressly agreed between the parties that money damages are inadequate to
compensate the Company for the Stock and that the Company shall, upon proper
exercise of the Purchase Option, be entitled to specific enforcement of its
rights to purchase and receive said Stock.

           (c) GOVERNING LAW; VENUE. This Agreement shall be governed by and
construed in accordance with the laws of the State of California as they apply
to agreements entered into in the State of California between residents of that
state. The parties agree that any action brought by either party to interpret or
enforce any provision of this Agreement shall be brought in, and each party
agrees to, and does hereby, submit to the jurisdiction and venue of, the
appropriate state or federal court located in San Diego, California.

           (d) FURTHER EXECUTION. The parties agree to take all such further
action(s) as may reasonably be necessary to carry out and consummate this
Agreement as soon as practicable, and to take whatever steps may be necessary to
obtain any governmental approval in connection with or otherwise qualify the
issuance of the securities that are the subject of this Agreement.

           (e) ENTIRE AGREEMENT; AMENDMENT. This Agreement constitutes the
entire agreement between the parties with respect to the subject matter hereof
and supersedes and merges all prior agreements or understandings, whether
written or oral. This Agreement may not be amended, modified or revoked, in
whole or in part, except by an agreement in writing signed by each of the
parties hereto.

           (f) SEVERABILITY. If one or more provisions of this Agreement are
held to be unenforceable under applicable law, the parties agree to renegotiate
such provision in good faith. In the event that the parties cannot reach a
mutually agreeable and enforceable replacement for such provision, then (i) such
provision shall be excluded from this Agreement, (ii) the balance of the
Agreement shall be interpreted as if such provision were so excluded and (iii)
the balance of the Agreement shall be enforceable in accordance with its terms.



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           (g) COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original and all of which
together shall constitute one instrument.

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.


                                   EPIMMUNE INC.


                                   By: /s/ Robert De Vaere
                                       ----------------------------------------

                                   Title: VP, Finance & CFO
                                          -------------------------------------

                                   Address:  5820 Nancy Ridge Drive, Suite 100
                                             San Diego, CA 92121


                                   /s/ Emile Loria
                                   --------------------------------------------
                                   EMILE LORIA


                                   Address: 31 rue de Dr. Jean Arlaud
                                            31500 Toulouse, France



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<PAGE>   8

                                    EXHIBIT A

                               CERTAIN DEFINITIONS


For purposes of the Agreement (including this Exhibit A):

"AFFILIATE" means any parent corporation or subsidiary corporation of the
Company, whether now or hereafter existing, as those terms are defined in
Sections 424(e) and (f), respectively, of the Code.

"CAUSE" shall mean: (i) willful misconduct by you including, but not limited to,
dishonesty which materially and adversely reflects upon your ability to perform
your duties for the Company; (ii) your conviction of, or the entry of a pleading
of guilty or nolo contendere by you to, any crime involving moral turpitude or
any felony; (iii) fraud, embezzlement or theft against the Company; (iv) a
material breach by you of any material provision of the Proprietary Information
and Inventions Agreement between you and the Company; or (v) your willful and
habitual failure to attend to your duties as assigned by the Board of Directors
or officers of the Company to whom you report and, in the case of clauses (iv)
and (v) above, which breach, misconduct or non-performance is not cured by you
within thirty (30) days after you receive written notice from the Company of
such breach, misconduct or non-performance.

"CHANGE IN CONTROL" shall mean: (i) a dissolution or liquidation of the Company;
(ii) a sale or other disposition of all or substantially all of the assets of
the Company; (iii) a merger or consolidation in which the Company is not the
surviving corporation and in which beneficial ownership of securities of the
Company representing at least fifty percent (50%) of the combined voting power
entitled to vote in the election of Directors has changed; (iv) an acquisition
by any person, entity or group within the meaning of Section 13(d) or 14(d) of
the Exchange Act, or any comparable successor provisions (excluding any employee
benefit plan, or related trust, sponsored or maintained by the Company or
subsidiary of the Company or other entity controlled by the Company) of the
beneficial ownership (within the meaning of Rule 13d-3 promulgated under the
Exchange Act, or comparable successor rule) of securities of the Company
representing at least fifty percent (50%) of the combined voting power entitled
to vote in the election of Directors.

"CONTINUOUS SERVICE" means that the Participant's service with the Company or an
Affiliate, whether as an Employee or Director, is not interrupted or terminated.
The Participant's Continuous Service shall not be deemed to have terminated
merely because of a change in the capacity in which the Participant renders
service to the Company or an Affiliate as an Employee, or Director or a change
in the entity for which the Participant renders such service, provided that
there is no interruption or termination of the Participant's Continuous Service.
For example, a change in status from an Employee of the Company to a Director
will not constitute an interruption of Continuous Service. The Company's Board
of Directors or the chief executive officer of the Company, in that party's sole
discretion, may determine whether Continuous Service shall be considered
interrupted in the case of any leave of absence approved by that party,
including sick leave, military leave or any other personal leave.


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"DIRECTOR" means a member of the Board of Directors of the Company.

"EMPLOYEE" means any person employed by the Company or an Affiliate. Mere
service as a Director or payment of a director's fee by the Company or an
Affiliate shall not be sufficient to constitute "employment" by the Company or
an Affiliate.

"EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended.

"GOOD REASON" shall mean termination by you of your employment with the Company
upon not less than thirty (30) days' prior written notice to the Company (to
allow the Company to remedy any basis for Good Reason termination) as a result
of (i) a substantial diminution in the scope of your duties and authority within
the Company which results in the assignment of duties and responsibilities of
materially lesser status, dignity and character than your duties and
responsibilities on the date of execution of this Agreement, which is not the
result of your failure to attend to and/or successfully complete your duties and
responsibilities, (ii) any reduction in your base salary as initially set forth
herein or as may be increased from time to time, or (iii) relocation of your
office, without your consent, to a location that is more than thirty (30) miles
from the Company's current corporate headquarters.

"OFFICER" means a person who is an officer of the Company within the meaning of
Section 16 of the Exchange Act and the rules and regulations promulgated
thereunder.

"SECURITIES ACT" means the Securities Act of 1933, as amended.




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                                    EXHIBIT B

                      ASSIGNMENT SEPARATE FROM CERTIFICATE


        FOR VALUE RECEIVED and pursuant to that certain Restricted Stock
Purchase Agreement (the "Agreement"), Emile Loria hereby sells, assigns and
transfers unto Epimmune Inc., a Delaware corporation ("Assignee"),
________________________ (__________) shares of the Common Stock of the
Assignee, standing in the undersigned's name on the books of said corporation
represented by Certificate No. _____ herewith and do hereby irrevocably
constitute and appoint ____________________________ as attorney-in-fact to
transfer the said stock on the books of the within named company with full power
of substitution in the premises. This Assignment may be used only in accordance
with and subject to the terms and conditions of the Agreement, in connection
with the reacquisition of shares of Common Stock of said corporation issued to
the undersigned pursuant to the Agreement, and only to the extent that such
shares remain subject to the Assignee's Purchase Option under the Agreement.

Dated:   January 16, 2001
      ------------------------------


                                      Signature:      /s/ Emile Loria
                                                 ------------------------------
                                                          EMILE LORIA



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                      ASSIGNMENT SEPARATE FROM CERTIFICATE


        FOR VALUE RECEIVED and pursuant to that certain Restricted Stock
Purchase Agreement (the "Agreement"), Emile Loria hereby sells, assigns and
transfers unto Epimmune Inc., a Delaware corporation ("Assignee"),
________________________ (__________) shares of the Common Stock of the
Assignee, standing in the undersigned's name on the books of said corporation
represented by Certificate No. _____ herewith and do hereby irrevocably
constitute and appoint ____________________________ as attorney-in-fact to
transfer the said stock on the books of the within named company with full power
of substitution in the premises. This Assignment may be used only in accordance
with and subject to the terms and conditions of the Agreement, in connection
with the reacquisition of shares of Common Stock of said corporation issued to
the undersigned pursuant to the Agreement, and only to the extent that such
shares remain subject to the Assignee's Purchase Option under the Agreement.


Dated:     January 16, 2001
       ------------------------


                                        Signature:  /s/ Emile Loria
                                                   ----------------------------
                                                   EMILE LORIA, RECIPIENT


<PAGE>   12

                                    EXHIBIT C

                            JOINT ESCROW INSTRUCTIONS


January 16, 2000

Assistant Secretary
Epimmune Inc.
5820 Nancy Ridge Drive
San Diego, CA  92121

Dear Sir/Madam:

        As Escrow Agent for both Epimmune Inc., a Delaware corporation (the
"Company"), and the undersigned recipient of stock of the Company ("Recipient"),
you are hereby authorized and directed to hold the documents delivered to you
pursuant to the terms of that certain Restricted Stock Purchase Agreement, dated
January 16, 2001 (the "Agreement") to which a copy of these Joint Escrow
Instructions is attached, in accordance with the following instructions set
forth below. Capitalized terms used but not otherwise defined herein shall have
the meaning given such terms in the Agreement.

        1. In the event Recipient ceases to render Continuous Service to the
Company or an Affiliate during the vesting period set forth in the Agreement,
the Company or its assignee will give to Recipient and you a written notice
specifying that the shares of Stock shall be transferred to the Company.
Recipient and the Company hereby irrevocably authorize and direct you to close
the transaction contemplated by such notice in accordance with the terms of said
notice.

        2. At the closing you are directed (a) to date any stock assignments
necessary for the transfer in question, (b) to fill in the number of shares of
Stock being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Company.

        3. Recipient irrevocably authorizes the Company to deposit with you any
certificates evidencing shares of Stock to be held by you hereunder and any
additions and substitutions to said shares as specified in the Agreement.
Recipient does hereby irrevocably constitute and appoint you as Recipient's
attorney-in-fact and agent for the term of this escrow to execute with respect
to such securities and other property all documents of assignment and/or
transfer and all stock certificates necessary or appropriate to make all
securities negotiable and complete any transaction herein contemplated.


<PAGE>   13

        4. This escrow shall terminate upon the later of (a) payment in full
under the Promissory Note of even date herewith and (b) vesting of all of the
shares of Stock or the earlier repurchase of all of the Unvested Shares by the
Company (or waiver of the Purchase Option with regard to such Unvested Shares).

        5. If at the time of termination of this escrow you should have in your
possession any documents, securities, or other property belonging to Recipient,
you shall deliver all of same to any pledgee entitled thereto or, if none, to
Recipient and shall be discharged of all further obligations hereunder.

        6. Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

        7. You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties or
their assignees. You shall not be personally liable for any act you may do or
omit to do hereunder as Escrow Agent or as attorney-in-fact for Recipient while
acting in good faith and any act done or omitted by you pursuant to the advice
of your own attorneys shall be conclusive evidence of such good faith.

        8. You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or corporation,
excepting only orders or process of courts of law, and are hereby expressly
authorized to comply with and obey orders, judgments or decrees of any court. In
case you obey or comply with any such order, judgment or decree of any court,
you shall not be liable to any of the parties hereto or to any other person,
firm or corporation by reason of such compliance, notwithstanding any such
order, judgment or decree being subsequently reversed, modified, annulled, set
aside, vacated or found to have been entered without jurisdiction.

        9. You shall not be liable in any respect on account of the identity,
authority or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

        10. You shall not be liable for the outlawing of any rights under any
statute of limitations with respect to these Joint Escrow Instructions or any
documents deposited with you.

        11. You shall be entitled to employ such legal counsel, including but
not limited to Cooley Godward LLP, and other experts as you may deem necessary
properly to advise you in connection with your obligations hereunder, may rely
upon the advice of such counsel, and may pay such counsel reasonable
compensation therefor.

        12. Your responsibilities as Escrow Agent hereunder shall terminate if
you shall cease to be Assistant Secretary of the Company or if you shall resign
by written notice to each party. In


<PAGE>   14

the event of any such termination, the Company may appoint any officer or
assistant officer of the Company as successor Escrow Agent and Recipient hereby
confirms the appointment of such successor or successors as his attorney-in-fact
and agent to the full extent of your appointment.

        13. If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.

        14. It is understood and agreed that should any dispute arise with
respect to the delivery and/or ownership or right of possession of the
securities, you may (but are not obligated to) retain in your possession without
liability to anyone all or any part of said securities until such dispute shall
have been settled either by mutual written agreement of the parties concerned or
by a final order, decree or judgment of a court of competent jurisdiction after
the time for appeal has expired and no appeal has been perfected, but you shall
be under no duty whatsoever to institute or defend any such proceedings.

        15. Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
any United States Post Box, by registered or certified mail with postage and
fees prepaid, addressed to each of the other parties hereunto entitled at the
following addresses, or at such other addresses as a party may designate by ten
(10) days' written notice to each of the other parties hereto:


        COMPANY:                 Epimmune Inc.
                                 5820 Nancy Ridge Drive
                                 San Diego, CA  92121
                                 Attn: Chief Financial Officer

        RECIPIENT:               Emile Loria
                                 31 rue du Dr Jean Arlaud
                                 31500 Toulouse, France

        ESCROW AGENT:            Epimmune Inc.
                                 5820 Nancy Ridge Drive
                                 San Diego, CA  92121
                                 Attn:  Assistant Secretary

        16. By signing these Joint Escrow Instructions you become a party hereto
only for the purpose of said Joint Escrow Instructions; you do not become a
party to the Agreement.

        17. This instrument shall be binding upon and inure to the benefit of
the parties hereto, and their respective successors and permitted assigns. It is
understood and agreed that references to "you" or "your" herein refer to the
original Escrow Agent and to any and all successor Escrow Agents. It is
understood and agreed that the Company may at any time or from


<PAGE>   15


time to time assign its rights under the Agreement and these Joint Escrow
Instructions in whole or in part.


                                            Very truly yours,

                                            EPIMMUNE, INC.



                                            By:   /s/ Robert De Vaere
                                               --------------------------------
                                            Title:   VP, Finance & CFO
                                                   ----------------------------


                                            RECIPIENT


                                                     /s/ Emile Loria
                                            -----------------------------------
                                            Emile Loria



ESCROW AGENT:

/s/ Robert De Vaere
-----------------------------------
Robert De Vaere