<PAGE>   1
                                                                   EXHIBIT 10.78


                                           *** TEXT OMITTED AND FILED SEPARATELY
                                                CONFIDENTIAL TREATMENT REQUESTED
                                          UNDER 17 C.F.R. SECTIONS 200.80(b)(4),
                                                            200.83 AND 240.24B-2


                         NON-EXCLUSIVE LICENSE AGREEMENT

        THIS NON-EXCLUSIVE LICENSE AGREEMENT (the "Agreement") is entered into
as of November __, 2000 (the "Effective Date"), by and between EPIMMUNE INC., a
Delaware corporation, having offices at 5820 Nancy Ridge Drive, San Diego,
California 92121 ("Epimmune"), and VALENTIS, INC., a Delaware corporation,
having offices at 863A Mitten Road, Burlingame, California 94010 ("Valentis").

        WHEREAS, Valentis has developed and owns the Patent Rights and
Biological Material (as defined below);

        WHEREAS, Valentis has previously transferred the Biological Material to
Epimmune pursuant to the Material Transfer Agreement between the parties dated
August 31, 1999 (the "Prior Agreement"); and

        WHEREAS, Epimmune wishes to obtain, and Valentis is willing to grant, a
non-exclusive, worldwide license under the Patent Rights to develop and
commercialize Products in the HCV Field and the HIV Field (as such terms are
defined below), on the terms and subject to the conditions set forth herein.

        NOW, THEREFORE, in consideration of the mutual covenants and promises
hereinafter set forth, the parties hereto hereby agree as follows:

                                    ARTICLE 1

                                   DEFINITIONS

1.1     "AFFILIATE" shall mean any corporation or other entity which controls,
        is controlled by, or is under common control with, a party. A
        corporation or other entity shall be regarded as in control of another
        corporation or entity if it owns or directly or indirectly controls 100%
        of the voting securities or other ownership interest of the other
        corporation or entity, or if it possesses, directly or indirectly, the
        power to direct or cause the direction of the management and policies of
        the corporation or other entity.

1.2     "BIOLOGICAL MATERIAL" shall mean Valentis' proprietary plasmid backbone,
        designated pMB75.6, all information, maps or data relating to such
        plasmid backbone supplied by Valentis to Epimmune, and all derivatives
        or modifications thereof.

1.3     "BLA" shall mean a Biological License Application filed pursuant to the
        requirements of the FDA.

1.4     "CONFIDENTIAL INFORMATION" shall mean any confidential or proprietary
        information of a party, including information related to the Patent
        Rights or Biological Material, and any other information relating to any
        compound, research project, work in process, future development,
        scientific, engineering, manufacturing, marketing, business plan,
        financial or personnel matter relating to such party, its present or
        future products, sales, suppliers, customers, employees, investors or
        business, whether in oral, written, graphic or electronic form.
        Notwithstanding the foregoing, Confidential Information shall not
        include any information which the receiving party can prove by competent
        written evidence:

(a)     is now, or hereafter becomes, through no act or failure to act on the
        part of the receiving party, generally known or available;

(b)     is known by the receiving party at the time of receiving such
        information, as evidenced by its records;

(c)     is hereafter furnished to the receiving party by a Third Party, as a
        matter of right and without restriction on disclosure;
<PAGE>   2

(d)     is independently developed by the receiving party, as evidenced by its
        records, without knowledge of, and without the aid, application or use
        of, the Confidential Information of the disclosing party; or

(e)     is the subject of a written permission to disclose provided by the
        disclosing party.

1.5     "CONTROL" shall mean possession of the ability to grant a license or
        sublicense without violating the terms of any agreement or other
        arrangement with any Third Party.

1.6     "FDA" shall mean the United States Food and Drug Administration or
        equivalent regulatory agency in any of the following countries: Canada,
        China, France, Germany, Italy, Japan, Mexico, Spain, Australia or the
        United Kingdom.

1.7     "FIELD" shall mean the HCV Field and/or the HIV Field, as applicable.

1.8     "FIRST COMMERCIAL SALE" of a Product means the first sale for use or
        consumption of such Product in a country after required marketing
        approval has been granted by the governing health regulatory authority
        of such country. Sale to an Affiliate or sublicensee shall not
        constitute a First Commercial Sale unless the Affiliate or sublicensee
        is the end user of the Product.

1.9     "HCV FIELD" shall mean the prophylactic and/or therapeutic treatment of
        hepatitis C virus infection in humans.

1.10    "HIV FIELD" shall mean the prophylactic and/or therapeutic treatment of
        human immunodeficiency virus infection in humans.

1.11    "NDA" shall mean a New Drug Application or Product License Application,
        as appropriate, filed pursuant to the requirements of the FDA.

1.12    "NET SALES" shall mean the gross amounts received by Epimmune, its
        Affiliates and its sublicensees for the sale of Products to Third
        Parties, less the following: (a) discounts actually granted, (b)
        credits, rebates or allowances actually granted upon claims, damaged
        goods, rejections or returns of Products, including recalls, (c)
        freight, postage, shipping and insurance charges actually allowed or
        paid for delivery of Products, to the extent billed, and (d) taxes,
        duties or other governmental charges (other than income taxes) levied
        on, absorbed or otherwise imposed on sales of Products. Amounts received
        by Epimmune or its Affiliates for the sale of Products between Epimmune
        and its Affiliates or sublicensees, whether for their own use or for
        resale or other disposition, will not be included in the computation of
        Net Sales hereunder.

        With regard to a product sold by Epimmune or its Affiliates or
        sublicensees that is comprised in part of a Product and in part of one
        or more other products (a "Combination Product"), Net Sales shall be
        determined by multiplying the amounts received by Epimmune or its
        Affiliates or sublicensees for the sale of such Combination Product by a
        fraction determined by dividing (i) the fair market value of the Product
        included in the Combination Product, by (ii) the sum of the fair market
        value of such Product and the fair market value of the other product(s)
        included in the Combination Product. As used herein, "fair market value"
        shall be equal to the average selling price, where such Product is sold
        on a stand-alone basis. If such Product is not sold on a stand-alone
        basis, "fair market value" shall be determined by mutual written
        agreement of the parties in good faith.

1.13    "PATENT RIGHTS" shall mean (a) the patents and patent applications
        listed on Exhibit A attached hereto, (b) any and all corresponding
        foreign patents and patent applications, whether now existing or
        hereafter filed, (c) any provisionals, substitutions, divisionals,
        reissues, renewals, continuations, continuations-in-part, substitute
        applications and inventors' certificates arising from, or based upon,
        any of the foregoing patents or patent applications, and (d) any patents
        issuing from any of the foregoing patent applications.

1.14    "PHASE I CLINICAL TRIALS" shall mean that portion of the clinical
        development program with respect to a pharmaceutical product which
        generally provides for the first introduction into humans of the product
        with the primary purpose of determining safety, metabolism and
        pharmacokinetic properties and clinical pharmacology of the product, as
        more specifically defined by the rules and regulations of the FDA and
        corresponding rules and regulations in other countries or jurisdictions.
<PAGE>   3

1.15    "PHASE III CLINICAL TRIALS" shall mean that portion of the clinical
        development program which provides for the continued trials of a
        pharmaceutical product on sufficient numbers of patients to establish
        the safety and efficacy of such product for the desired claims and
        indications, as more specifically defined by the rules and regulations
        of the FDA and corresponding rules and regulations in other countries or
        jurisdictions. Notwithstanding the foregoing, if Phase III Clinical
        Trials are not conducted, but Epimmune, its Affiliate or sublicensee
        nonetheless pursues regulatory approval of a Product based upon Phase II
        trial results, such Phase II trial shall be deemed to be a Phase III
        Clinical Trial.

1.16    "PRODUCT" shall mean a plasmid-based therapeutic or prophylactic vaccine
        developed by Epimmune, its Affiliates or its sublicensees the
        manufacture, use, importation, offer for sale, or sale of which is
        covered by a Valid Claim or is based upon or incorporates the Biological
        Material.

1.17    "ROYALTY TERM" shall mean, on a country-by-country basis, the longer of:
        (a) the period of time commencing on the First Commercial Sale and
        ending upon the expiration of the last to expire Valid Claim covering
        such Product in such country; and (b) the period of time commencing on
        the First Commercial Sale in such country and ending *** years from the
        date of First Commercial Sale in such country.

1.18    "THIRD PARTY" shall mean any entity other than Epimmune or Valentis or
        an Affiliate of Epimmune or Valentis.

1.19    "VALID CLAIM" shall mean a claim of an issued patent included within the
        Patent Rights, which claim has not lapsed, been canceled or become
        abandoned and has not been declared invalid or unenforceable by an
        unreversed and unappealable decision or judgment of a court or other
        appropriate body of competent jurisdiction, and which has not been
        admitted to be invalid or unenforceable through reissue, disclaimer or
        otherwise.

                                   ARTICLE 2

                                GRANT OF LICENSE

2.1     LICENSE GRANT. Subject to the terms and conditions of this Agreement,
        Valentis hereby grants to Epimmune and its Affiliates a non-exclusive,
        worldwide, non-transferable (except as provided in Section 10.1)
        royalty-bearing license, with the right to sublicense in accordance with
        Section 2.2, under the Patent Rights to develop, make, have made, use,
        offer for sale, sell, have sold and import Products solely for use in
        the HCV Field and the HIV Field and to use the Biological Material for
        such purposes.

2.2     SUBLICENSES. Epimmune and its Affiliates shall have the right to grant
        sublicenses solely to bona fide strategic or collaborative partners of
        Epimmune or an Affiliate of Epimmune for use solely in such strategic or
        collaborative partners' collaborative research, development or
        commercialization program with Epimmune or such Affiliate and to
        transfer Biological Material to such partners for use in connection with
        such purposes, provided that such collaborative or strategic partner is
        also granted, at the same time as the sublicense, rights to
        substantially all other intellectual property Controlled by Epimmune or
        its Affiliates relating to a Product. Epimmune shall notify any
        sublicensee hereunder of all rights and obligations of Epimmune under
        this Agreement which are sublicensed to such sublicensee and shall
        notify Valentis within thirty (30) days of the grant of any sublicense
        hereunder, and provide a copy of such sublicense to Valentis.

2.3     NEGATIVE COVENANT. Epimmune hereby covenants that neither it nor any of
        its Affiliates shall practice any invention claimed in the Patent Rights
        or use the Biological Material outside the HCV Field or the HIV Field.
        Epimmune further covenants that neither it nor its Affiliates shall
        transfer the Biological Material to any Third Party except as permitted
        under Section 2.2 above, or otherwise for purposes of developing,
        manufacturing or commercializing Products.

2.4     REASONABLE ACCESS. Valentis will provide Epimmune with access to
        appropriate personnel of Valentis via telephone, facsimile or electronic
        mail during Valentis' regular business hours in order to discuss
        questions

                                              * CONFIDENTIAL TREATMENT REQUESTED
<PAGE>   4

        relating to the use of the Biological Material and the Patent Rights in
        connection with the Products, provided that such access is limited to
        six (6) days per year.

                                    ARTICLE 3

                               PAYMENT OBLIGATIONS

3.1     LICENSE FEE. In partial consideration of the license granted to Epimmune
        by Valentis, Epimmune shall pay to Valentis a license fee of *** within
        ten (10) days of the Effective Date.

3.2     ROYALTIES.

(a)     With regard to any Product the manufacture, use, importation, offer for
        sale or sale of which is covered by a Valid Claim, Epimmune shall pay to
        Valentis a royalty of (i) *** on that portion of annual Net Sales of
        such Product that is less than or equal to ***, and (ii) *** on that
        portion of annual Net Sales of such Product that is greater than ***;
        provided, however, that, if Epimmune or its Affiliate enters into a
        collaborative or strategic relationship with a Third Party with respect
        to such Product prior to initiation of Phase III Clinical Trials of such
        Product, then, with respect to such Product, Epimmune shall pay to
        Valentis a royalty equal to the greater of (A) *** of royalty payments
        received by Epimmune and its Affiliates from such Third Party with
        respect to sales of such Product or (B) the royalty on Net Sales of such
        Product specified in Section 3.2(a)(i) and (ii) above.

(b)     With regard to any Product the manufacture, use, importation, offer for
        sale or sale of which is not covered by a Valid Claim, Epimmune shall
        pay to Valentis a royalty of (i) *** on that portion of annual Net Sales
        of such Product that is less than or equal to ***, and (ii) *** on that
        portion of annual Net Sales of such Product that is greater than ***;
        provided, however, that, if Epimmune or its Affiliate enters into a
        collaborative or strategic relationship with a Third Party with respect
        to such Product prior to initiation of Phase III Clinical Trials of such
        Product, then, with respect to such Product, Epimmune shall pay to
        Valentis a royalty equal to the greater of (A) *** of royalty payments
        received by Epimmune and its Affiliates from such Third Party with
        respect to sales of such Product or (B) the royalty on Net Sales of such
        Product specified in Section 3.2(b)(i) and (ii) above.

(c)     Royalties under this Section 3.2 shall be paid, on a country-by-country
        and Product-by-Product basis, during the Royalty Term.

3.3     MILESTONES. At any time following initiation of Phase I Clinical Trials
        of the first Product to enter Phase I Clinical Trials in each of the HIV
        Field and the HCV Field, as applicable, Valentis shall have the right,
        exercisable upon written notice to Epimmune (the "Milestone Notice"), to
        cause the applicable milestone payment set forth below to become payable
        to Valentis by Epimmune with respect to a Product, which payment may be
        made, at Epimmune's option, either in cash or in Common Stock of
        Epimmune:

(a)     If Valentis delivers the Milestone Notice with respect to a Product in a
        Field after initiation of Phase I Clinical Trials of the first Product
        to enter Phase I Clinical Trials in such Field and before initiation of
        Phase III Clinical Trials of any Product in such Field, Epimmune shall
        pay to Valentis (i) *** in cash or (ii) *** of Common Stock (determined
        as set forth below). The milestone payment set forth in this Section
        3.3(a) shall be payable with respect to one (1) Product in each of the
        HIV Field and the HCV Field, provided that the applicable Milestone
        Notice is given during the specified period.

(b)     If Valentis delivers the Milestone Notice with respect to a Product in a
        Field after initiation of Phase III Clinical Trials of a Product in such
        Field and before FDA approval of an NDA or BLA (as applicable) of such
        Product in such Field, Epimmune shall pay to Valentis (i) *** in cash or
        (ii) *** of Common Stock (determined as set forth below).

                                              * CONFIDENTIAL TREATMENT REQUESTED

<PAGE>   5

        The milestone payment set forth in this Section 3.3(b) shall be payable
        with respect to one (1) Product in each of the HIV Field and the HCV
        Field, provided that the applicable Milestone Notice is given during the
        specified period.

(c)     If Valentis delivers the Milestone Notice with respect to a Product in a
        Field after FDA approval of an NDA or BLA (as applicable) of such
        Product in such Field, Epimmune shall pay to Valentis (i) *** in cash or
        (ii) *** of Common Stock (determined as set forth below). The milestone
        payment set forth in this Section 3.3(c) shall be payable with respect
        to one (1) Product in each of the HIV Field and the HCV Field, provided
        that the applicable Milestone Notice is given during the specified
        period.

        The number of shares of Common Stock that may be issuable to Valentis
        under this Section 3.3 shall be determined by dividing the dollar amount
        set forth in Section 3.3(a)(ii), 3.3(b)(ii) or 3.3(c)(ii), as
        applicable, by a per share price equal to the average of the closing
        prices per share of the Common Stock on the Nasdaq National Market (or
        any other national securities exchange on which the Common Stock is then
        traded) for the thirty (30) consecutive trading days ending on the
        trading day immediately preceding the Epimmune Notice (as defined
        below). In the event that the per share price of Common Stock to be
        issued to Valentis under this Section 3.3 as determined above is below
        ***, then Epimmune will be obligated to deliver the applicable milestone
        payment in cash. Notwithstanding the foregoing, in no event will
        Epimmune be obligated to issue shares of Common Stock under this
        Agreement to the extent such issuance would require approval of
        Epimmune's stockholders under the rules and regulations of the Nasdaq
        Stock Market (or any other national securities exchange on which the
        Common Stock is then traded). In such event, Epimmune would be obligated
        to deliver to Valentis the applicable milestone payment in cash.

        Epimmune shall make each milestone payment for which it has received a
        Milestone Notice hereunder and for which it elects to pay cash within
        twenty (20) days following receipt of such Milestone Notice. If Epimmune
        elects to make any milestone payment under this Section 3.3 in Common
        Stock, Epimmune shall provide Valentis with written notice of such
        election (the "Epimmune Notice") within ten (10) days following receipt
        of the applicable Milestone Notice. Such Common Stock shall be delivered
        to Valentis within sixty (60) days of the Epimmune Notice.

        On the Effective Date, the parties shall enter into an agreement in the
        form attached hereto as EXHIBIT B with respect to such shares of Common
        Stock that may be issued to Valentis.

                                    ARTICLE 4

                            PAYMENTS; RECORDS; AUDITS

4.1     PAYMENT; REPORTS. Royalty payments and reports for the sale of Products
        shall be calculated and reported for each calendar quarter. All royalty
        payments due to Valentis under this Agreement shall be paid within sixty
        (60) days of the end of each calendar quarter. Each payment of royalties
        shall be accompanied by a report of Net Sales of Products (and, if
        applicable under Section 3.2, royalties received by Epimmune and its
        Affiliates) in sufficient detail to permit confirmation of the accuracy
        of the royalty payment made, including, without limitation, the number
        of Products sold, the gross sales and Net Sales of Products, the
        royalties payable and the method used to calculate the royalty.

4.2     EXCHANGE RATE; MANNER AND PLACE OF PAYMENT. All payments hereunder shall
        be payable in U.S. dollars. With respect to each quarter, for countries
        other than the United States, whenever conversion of royalty payments
        from any foreign currency shall be required, such conversion shall be
        made at the rate of exchange reported in The Wall Street Journal
        (Western Edition) on the last business day of such quarter. All payments
        owed under this Agreement shall be made by wire transfer to a bank and
        account designated in writing by Valentis, unless otherwise specified in
        writing by Valentis.


                                              * CONFIDENTIAL TREATMENT REQUESTED

<PAGE>   6

4.3     LATE PAYMENTS. Any amounts not paid by Epimmune when due under this
        Agreement shall be subject to interest from the date payment is due
        through the date payment is received by Valentis at a rate equal to the
        sum of two percent (2%) plus the prime rate of interest quoted in the
        Money Rates section of The Wall Street Journal (Western Edition),
        calculated daily on the basis of a 360-day year, or similar reputable
        data source, or, if lower, the highest rate permitted under applicable
        law.

4.4     RECORDS AND AUDITS. Epimmune shall keep for a period covering at least
        the preceding *** years complete and accurate records pertaining to the
        development and sale or other disposition of Products in sufficient
        detail to permit Valentis to confirm the accuracy of all payments due
        hereunder. Valentis shall have the right to cause an independent,
        certified public accountant reasonably acceptable to Epimmune to audit
        such records for the purpose of verifying any amounts payable, or
        information provided, under this Agreement. Such audits may be exercised
        during normal business hours upon reasonable prior written notice to
        Epimmune. Prompt adjustments shall be made by the parties to reflect the
        results of such audit. Valentis shall bear the full cost of such audit,
        unless such audit discloses a variance of more than *** from the amounts
        actually due, in which case Epimmune shall bear the full cost of such
        audit.

4.5     TAXES. All taxes levied on account of the royalties and other payments
        accruing to Valentis under this Agreement shall be paid by Valentis for
        its own account, including taxes levied thereon as income to Valentis.
        If provision is made in law or regulation for withholding, such tax
        shall be deducted by Epimmune from the sums otherwise payable by it
        hereunder for payment to the proper taxing authority on behalf of
        Valentis and a receipt of payment of the tax secured and promptly
        delivered to Valentis. Each party agrees to assist the other party in
        claiming exemption from such deductions or withholdings under any double
        taxation or similar agreement or treaty from time to time in force.

4.6     PROHIBITED PAYMENTS. Notwithstanding any other provision of this
        Agreement, if Epimmune is prevented from paying any royalty payment
        hereunder by virtue of the statutes, laws, codes or governmental
        regulations of the country from which the payment is to be made, then
        such royalty may be paid by depositing funds in the currency in which
        accrued to Valentis' account in a bank acceptable to Valentis in the
        country whose currency is involved.

                                   ARTICLE 5

                          CONFIDENTIALITY; PUBLICATION

5.1     CONFIDENTIALITY. During the term of this Agreement, and for a period of
        *** years thereafter, each party hereto will maintain in confidence all
        Confidential Information disclosed by the other party hereto. Neither
        party will use, disclose or grant use of such Confidential Information
        except as expressly authorized by this Agreement. To the extent that
        disclosure is authorized by this Agreement, the disclosing party will
        obtain prior agreement from its employees, agents or consultants to whom
        disclosure is to be made to hold in confidence and not make use of such
        information for any purpose other than those permitted by this
        Agreement. Each party will use at least the same standard of care as it
        uses to protect its own Confidential Information to ensure that such
        employees, agents or consultants do not disclose or make any
        unauthorized use of such Confidential Information. Each party will
        promptly notify the other upon discovery of any unauthorized use or
        disclosure of the Confidential Information.

5.2     AUTHORIZED DISCLOSURE. Each party may disclose the Confidential
        Information to the extent such disclosure is reasonably necessary in
        filing or prosecuting patent applications, prosecuting or defending
        litigation or complying with applicable governmental regulations,
        provided that if such party is required to make any such disclosure of
        the Confidential Information it will to the extent practicable give
        reasonable advance notice to the other party of such disclosure
        requirement and, except to the extent inappropriate in the case of
        patent applications, will use its best efforts to secure confidential
        treatment of such information required to be disclosed.


                                              * CONFIDENTIAL TREATMENT REQUESTED

<PAGE>   7

                                    ARTICLE 6

                          INTELLECTUAL PROPERTY RIGHTS

6.1     FILING, PROSECUTION AND MAINTENANCE OF THE PATENT RIGHTS. Valentis shall
        own all right, title and interest in, and shall have the sole right to
        control the filing, prosecution and maintenance of, all patent
        applications and patents included in the Patent Rights, at Valentis'
        expense.

6.2     INFRINGEMENT ACTIONS. Valentis shall have the sole right to prosecute,
        at its discretion, any and all infringements of any Patent Rights, and
        to defend all charges of infringement arising as a result of such Patent
        Rights, and to enter all settlements, judgments or other arrangements
        with respect to the same, all at its own expense and by counsel of its
        own choice. Any damages or other recovery from such infringement actions
        in excess of the expenses and costs incurred by Valentis in connection
        with such action shall belong solely Valentis.

6.3     PATENT MARKING. Epimmune and its Affiliates and sublicensees shall mark
        Products with appropriate patent numbers in those countries where
        markings have notice value as against infringers.

6.4     INFRINGEMENT OF THIRD PARTY RIGHTS. If the sale of any Product is
        determined or alleged to infringe, or if Epimmune receives notice of or
        is sued for infringement of, a patent owned or licensed by Third Party,
        Valentis and Epimmune shall meet to discuss what action should be taken
        if such claim involves the Patent Rights. Epimmune or its Affiliate or
        sublicensee, as applicable, shall be solely responsible for the defense
        or settlement of any patent infringement claim or lawsuit brought by any
        Third Party involving the sale of any Product, including all expenses
        and amounts payable as damages or in settlement.


                                    ARTICLE 7

                     REPRESENTATIONS; WARRANTIES; COVENANTS

7.1     CORPORATE POWER. Each party hereby represents and warrants that it is
        duly organized, validly existing and in good standing under the laws of
        the state or jurisdiction of its incorporation or formation and has full
        corporate power and authority to enter into this Agreement and to carry
        out the provisions hereof.

7.2     DUE AUTHORIZATION. Each party hereby represents and warrants that such
        party is duly authorized to execute and deliver this Agreement and to
        perform its obligations hereunder.

7.3     BINDING AGREEMENT. Each party hereby represents and warrants that this
        Agreement is a legal and valid obligation binding upon it and is
        enforceable in accordance with its terms. The execution, delivery and
        performance of this Agreement by such party does not conflict with any
        agreement, instrument or understanding, oral or written, to which it is
        a party or by which it may be bound, nor violate any law or regulation
        of any court, governmental body or administrative or other agency having
        authority over it.

7.4     PATENT PROCEEDINGS. Valentis represents and warrants that to the best of
        its knowledge, no patent or patent application within the Patent Rights
        is the subject of any pending interference, opposition, cancellation or
        other protest proceeding.

7.5     DISCLAIMER OF WARRANTIES. EXCEPT AS EXPRESSLY SET FORTH IN THIS
        AGREEMENT, NEITHER PARTY MAKES ANY REPRESENTATION OR WARRANTY TO THE
        OTHER PARTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING, WITHOUT
        LIMITATION, ANY WARRANTY OF TITLE, NON-INFRINGEMENT, MERCHANTABILITY OR
        FITNESS FOR A PARTICULAR PURPOSE.
<PAGE>   8

7.6     INDEMNIFICATION.

(a)     Epimmune and its Affiliates (each an "Indemnifying Party") shall
        indemnify, hold harmless and defend Valentis, its officers, directors
        and employees and/or agents (the "Indemnitees") against any and all
        Third Party claims, suits, losses, damage, costs, fees (including
        reasonable attorney's fees) and expenses resulting from or arising out
        of Epimmune's or its Affiliates', or its or their sublicensees'
        development, testing, distribution, marketing, promotion or sale of any
        Product; provided that no Indemnitee shall be entitled to
        indemnification hereunder to the extent that any such claims, suits,
        losses, damage, costs, fees and expenses result from the gross
        negligence or willful misconduct of any Indemnitee.

(b)     Any Indemnitee, as the case may be, shall notify the Indemnifying Party
        promptly in writing of an indemnifiable claim or cause of action under
        Section 7.6(a) upon receiving notice or being informed of the existence
        thereof. The Indemnifying Party shall assume, at its cost and expense,
        the sole defense of such claim or cause of action through counsel
        selected by the Indemnifying Party and reasonably acceptable to the
        Indemnitee. The Indemnifying Party shall maintain control of such
        defense, including any decision as to settlement; provided that, in the
        event that the Indemnifying Party does not maintain control of such
        defense on a timely basis, then, without prejudice to any other rights
        and remedies available to the Indemnitee under this Agreement, the
        Indemnitee may take over such defense with counsel of its choosing, at
        the Indemnifying Party's cost and expense. The Indemnitee may, at its
        option and expense, participate in the Indemnifying Party's defense, and
        if the Indemnitee so participates, the Indemnifying Party and the
        Indemnitee shall cooperate with one another in such defense.

7.7     INSURANCE. Epimmune represents and warrants that it is covered and will
        continue to be covered by a comprehensive general liability insurance
        program which covers all Epimmune's activities and obligations
        hereunder. Epimmune shall provide Valentis with written notice at least
        fifteen (15) days prior to any cancellation or material change in such
        insurance program. Epimmune shall maintain such insurance program, or
        other program with comparable coverage, beyond the expiration or
        termination of this Agreement during (i) the period that any Product is
        being commercially distributed or sold by Epimmune, its Affiliates or a
        sublicensee, and (ii) a commercially reasonable period thereafter.

7.8     LIMITATION OF LIABILITY. EXCEPT FOR AMOUNTS PAYABLE UNDER ARTICLE 3 AND
        EXCEPT AS REQUIRED FOR EPIMMUNE TO SATISFY ITS INDEMNIFICATION
        OBLIGATIONS UNDER SECTION 7.6, NEITHER EPIMMUNE NOR ANY OF ITS
        AFFILIATES SHALL BE LIABLE FOR ANY INDIRECT, INCIDENTAL, SPECIAL OR
        CONSEQUENTIAL DAMAGES SUFFERED BY VALENTIS IN CONNECTION WITH THIS
        AGREEMENT, EVEN IF EPIMMUNE OR ANY OF ITS AFFILIATES HAS BEEN ADVISED OF
        THE POSSIBILITY OF SUCH DAMAGES.

                                    ARTICLE 8

                                TERM; TERMINATION

8.1     TERM. This Agreement shall commence as of the Effective Date and shall
        continue, on a country-by-country basis, until the last day of the
        Royalty Term, unless terminated earlier as provided herein (the "Term").
        Following the expiration of this Agreement, Epimmune shall have a
        license on the same terms as set forth in Section 2.1, except that the
        license shall be a fully-paid, irrevocable license.

8.2     TERMINATION FOR BREACH. A party may terminate this Agreement prior to
        the expiration of the Term upon or after the breach of any material
        provision of this Agreement by the other party if the breaching party
        has not cured such breach within sixty (60) days after written notice
        thereof by the non-breaching party.

8.3     TERMINATION BY EPIMMUNE. Epimmune may terminate this Agreement prior to
        the expiration of the Term at any time upon thirty (30) days' written
        notice to Valentis.

8.4     TERMINATION FOR PATENT CHALLENGE. Valentis shall have the right to
        terminate this Agreement if Epimmune, its Affiliate or sublicensee
        challenges the validity of any patent included in the Patent Rights
        within any country effective thirty (30) days after Epimmune's receipt
        of written notice of such termination by Valentis.

<PAGE>   9

8.5     EFFECT OF TERMINATION.

(a)     Upon termination of this Agreement (i) all rights to the Patent Rights
        and Biological Material shall revert to Valentis, and (ii) any
        sublicense granted hereunder by Epimmune shall remain in full force and
        effect, but shall be assigned to Valentis.

(b)     Within thirty (30) days following the expiration or termination of this
        Agreement, each party shall return to the other party, or destroy, upon
        the written request of the other party, any and all Confidential
        Information of the other party in its possession. Epimmune shall return
        or destroy all Biological Material in its possession.

(c)     Expiration or termination of this Agreement shall not relieve the
        parties of any obligation accruing prior to such expiration or
        termination. The provisions of Sections 4.3, 7.5, 7.8 and 8.4 and
        Articles 1, 5, 9 and 10 shall survive termination or expiration of this
        Agreement.

                                    ARTICLE 9

                               DISPUTE RESOLUTION

        If a dispute arises between the parties relating to the interpretation
        or performance of this Agreement or the grounds for the termination
        thereof (but not as to the enforceability or validity or interpretation
        of any claims within the Patent Rights), and the parties cannot resolve
        the dispute within thirty (30) days of a written request by either party
        to the other party, the parties agree to hold a meeting, attended by
        individuals with decision-making authority regarding the dispute, to
        attempt in good faith to negotiate a resolution of the dispute prior to
        pursuing other available remedies. If, within thirty (30) days after
        such meeting, the parties have not succeeded in negotiating a resolution
        of the dispute, such dispute shall be submitted to final and binding
        arbitration under the then current commercial rules and regulations of
        the American Arbitration Association (the "AAA") relating to voluntary
        arbitrations in San Francisco, California. The arbitration shall be
        conducted by one arbitrator, who is knowledgeable in the subject matter
        at issue in the dispute and who will be selected by mutual agreement of
        the parties or, failing such agreement, shall be selected in accordance
        with the AAA rules. Each party shall initially bear its own costs and
        legal fees associated with such arbitration. The prevailing party in any
        such arbitration shall be entitled to recover from the other party
        reasonable attorneys' fees, costs and expenses incurred by such
        prevailing party in connection with such arbitration. The decision of
        the arbitrator shall be final and binding and may be sued on or enforced
        by the party in whose favor it runs in any court of competent
        jurisdiction. The arbitrator shall prepare and deliver a written,
        reasoned opinion conferring its decision within thirty (30) days
        following the final arbitration hearing.

        Notwithstanding the foregoing, either party shall have the right to
        pursue an action in a court of competent jurisdiction to obtain
        injunctive or other equitable remedy, in order to preserve the status
        quo during the resolution of any dispute under this provision.


                                   ARTICLE 10

                                  MISCELLANEOUS

10.1    ASSIGNMENT. Except as expressly provided hereunder, neither this
        Agreement nor any rights or obligations hereunder may be assigned or
        otherwise transferred by either party without the prior written consent
        of the other party (which consent shall not be unreasonably withheld);
        provided, however, that either party may assign this Agreement and its
        rights and obligations hereunder without the other party's consent (a)
        in connection with the transfer or sale of all or substantially all of
        the business of such party to which this Agreement relates to a Third
        Party, whether by merger, sale of stock, sale of assets or otherwise, or
        (b) to any Affiliate. Notwithstanding the foregoing, any such assignment
        to an Affiliate shall not relieve the assigning party of its
        responsibilities for performance of its obligations under this
        Agreement. The rights and obligations of the parties under this
        Agreement shall be binding upon and inure to the benefit of the
        successors and permitted assigns of the parties. Any assignment not in
        accordance with this Agreement shall be void.

<PAGE>   10

10.2    FORCE MAJEURE. Neither party shall be held liable or responsible to the
        other party nor be deemed to have defaulted under or breached this
        Agreement for failure or delay in fulfilling or performing any term of
        this Agreement when such failure or delay is caused by or results from
        causes beyond the reasonable control of the affected party, including,
        without limitation, fire, floods, earthquakes, natural disasters,
        embargoes, war, acts of war (whether war be declared or not),
        insurrections, riots, civil commotions, strikes, lockouts or other labor
        disturbances, acts of God or acts, omissions or delays in acting by any
        governmental authority or the other party.

10.3    GOVERNING LAW. This Agreement shall be governed by, and construed and
        enforced in accordance with, the laws of the State of California,
        without regard to its choice of law provisions.

10.4    WAIVER. Except as specifically provided for herein, the waiver from time
        to time by either party of any right or failure to exercise any remedy
        shall not operate or be construed as a continuing waiver of the same
        right or remedy or of any other of such party's rights or remedies
        provided under this Agreement.

10.5    SEVERABILITY. In case any provision of this Agreement shall be invalid,
        illegal or unenforceable, the validity, legality and enforceability of
        the remaining provisions shall not in any way be affected or impaired
        thereby.

10.6    INDEPENDENT CONTRACTORS. It is expressly agreed that Epimmune and
        Valentis shall be independent contractors and that the relationship
        between the two parties shall not constitute a partnership, joint
        venture or agency of any kind. Neither party shall have the authority to
        make any statements, representations or commitments of any kind, or to
        take any action, which shall be binding on the other party, without the
        prior written consent of the other party.

10.7    NOTICES. All notices and other communications provided for hereunder
        shall be in writing and shall be mailed by first-class, registered or
        certified mail, postage paid, or delivered personally, by overnight
        delivery service or by facsimile, with confirmation of receipt,
        addressed as follows:

        IF TO EPIMMUNE:             EPIMMUNE INC.
                                    5820 Nancy Ridge Drive
                                    San Diego, CA  92121
                                    Attention:  President
                                    Facsimile:  (858) 860-2600
        IF TO VALENTIS:             VALENTIS, INC.
                                    863A Mitten Road
                                    Burlingame, California  94010
                                    Attention:  CEO
                                    Facsimile:  (650) 652-1990

        Either party may by like notice specify or change an address to which
        notices and communications shall thereafter be sent. Notices sent by
        facsimile shall be effective upon confirmation of receipt, notices sent
        by mail or overnight delivery service shall be effective upon receipt,
        and notices given personally shall be effective when delivered.


10.8    ENTIRE AGREEMENT; AMENDMENT. This Agreement (including the Exhibits
        attached hereto) sets forth all of the agreements and understandings
        between the parties hereto with respect to the subject matter hereof,
        and supersedes and terminates all prior agreements and understandings
        between the parties with respect to the subject matter hereof, except
        for the Prior Agreement, which shall remain in full force and effect to
        the extent not expressly superceded by this Agreement. There are no
        agreements or understandings with respect to the subject matter hereof,
        either oral or written, between the parties other than as set forth
        herein or in the Prior Agreement. Except as expressly set forth in this
        Agreement, no subsequent amendment, modification or addition to this
        Agreement shall be binding upon the parties hereto unless reduced to

<PAGE>   11

        writing and signed by the respective authorized officers of the parties.

10.9    HEADINGS. The captions contained in this Agreement are not a part of
        this Agreement, but are merely guides or labels to assist in locating
        and reading the several Articles hereof.

10.10   COUNTERPARTS. This 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.


<PAGE>   12


        IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first set forth above.


EPIMMUNE INC.                                    VALENTIS, INC.


<TABLE>
<S>                                              <C>
By:    /s/ Stephen F. Keane                      By:    /s/ Margaret M. Snowden
     ----------------------------------------       ------------------------------------------------------

Name:  Stephen F. Keane                          Name: Margaret M. Snowden
       --------------------------------------          ---------------------------------------------------

Title: Vice President, Corporate Development     Title: Vice Pres., Intellectual Property & Legal Affairs
       --------------------------------------           --------------------------------------------------
</TABLE>


<PAGE>   13



                                    EXHIBIT A
                                  PATENT RIGHTS

                                       ***













                                              * CONFIDENTIAL TREATMENT REQUESTED



<PAGE>   14



                                    EXHIBIT B
                     FORM OF COMMON STOCK ISSUANCE AGREEMENT