<PAGE>   1
                                                                   EXHIBIT 10.24

    DATED                                                     1998

    (1)  IMPERIAL CANCER RESEARCH TECHNOLOGY LIMITED

    (2)  INTROGEN THERAPEUTICS, INC




OPTION AGREEMENT


 21/05/1998

 REFERENCE

DM/97 - 58598


<PAGE>   2
                                    CONTENTS

<TABLE>
<CAPTION>

CLAUSE

<S>                                                             <C>
1 INTRODUCTION ................................................ 1

2 INTERPRETATION .............................................. 1

3 GRANT OF THE FIRST OPTION ................................... 5

4 EXERCISE OF THE FIRST OPTION ................................ 7

5 THE PROJECT ................................................. 8

6 OWNERSHIP OF TECHNOLOGY AND INTELLECTUAL PROPERTY ...........11

7 CONFIDENTIALITY AND PUBLICATION .............................16

8 TERMINATION .................................................20

9 GENERAL .....................................................22

10 NOTICES AND SERVICE ........................................26

11 MISCELLANEOUS ..............................................27

SCHEDULES

SCHEDULE 1 ....................................................28

   THE EXISTING PATENTS .......................................28

SCHEDULE 2 ....................................................29

   THE TERMS OF THE FIRST LICENCE .............................29

SCHEDULE 3 ....................................................35

   OBJECTIVES OF THE PROJECT ..................................35

SCHEDULE 4 ....................................................36

   THE TERMS OF THE SECOND LICENCE ............................36
</TABLE>




<PAGE>   3
                   CONTENTS AGREEMENT dated             1998


BETWEEN:

(1)  IMPERIAL CANCER RESEARCH TECHNOLOGY LIMITED, incorporated in England and
     Wales with registered number 1662284, whose registered office is at
     Sardinia House, Sardinia Street, London WC2A 3NL, England ('ICRT')

(2)  INTROGEN THERAPEUTICS, INC, incorporated in the State of Delaware, whose
     principal office is at 301 Congress Avenue, Suite 1850, Austin, Texas
     78701, USA ('INTROGEN')

1    INTRODUCTION

1.1  Imperial Cancer Research Fund ('ICRF') and ICRT have identified and carried
     out a programme of research work relating to a tumour suppressor gene known
     as 'PTEN' which has potential diagnostic and therapeutic uses, and in
     respect of which certain patent applications have been made by ICRT,
     details of which are given in Schedule 1.

1.2  Introgen wishes to acquire rights in relation to the Gene in order to
     develop DNA based therapeutic products, in particular for the treatment of
     cancer.

1.3  ICRT is a company wholly owned by ICRF and, by arrangement with ICRF, owns
     and is responsible for the management and exploitation of ICRF technology.

2    INTERPRETATION

2.1  In this Agreement -

     'AFFILIATE' means, in relation to either party, a company which controls
     that party, or is controlled by that party or by a company which controls
     that party; and for these


                                     PAGE 1


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     purposes a company controls another company if, either directly or
     indirectly through one or more other companies, it can -

     o    exercise a majority of the votes attached to the shares in the other
          company; or

     appoint or remove a majority of the board of directors of the other
     company;

    'THE EFFECTIVE DATE' means 1st June 1998;

     'THE EXISTING PATENTS' means the patent applications referred to in clause
     1.1, any patents issued in pursuance of any such application, any
     extension, reissue, division, continuation or continuation-in-part of any
     such application or patent and any patent of addition, supplementary
     protection certificate or similar rights based on any such patent;

     'EXISTING TECHNOLOGY' means any Technology relating to the Gene which has
     been obtained, developed, found, produced or made by or for ICRF or ICRT at
     any time prior to the Effective Date;

     'THE FIELD' means the field of [*];

     'THE FIRST LICENCE' means the licence to be granted pursuant to clause 4.1;

     'THE FIRST OPTION' means the option granted by ICRT under clause 3.1;

     'THE FIRST OPTION PERIOD' means the period of [*] from the Effective
     Date;

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.


                                     PAGE 2


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    'THE GENE' means the PTEN gene referred to in clause 1.1 including, for the
    avoidance of doubt, any splice variants or other derivatives of that gene
    and for the purposes of the foregoing, a "derivative" means a nucleotide
    sequence derived from that gene (including fragments thereof) the product of
    which has tumour suppressor activity;

    'ICRF' means Imperial Cancer Research Fund;

    'INTELLECTUAL PROPERTY' means any patent application or patent (including
    any extension, reissue, division, continuation or continuation-in-part of
    any such application or patent and any patent of addition, supplementary
    protection certificate or similar rights based on any patent), copyright or
    other form of protection, the right to make any application for any such
    protection in any part of the world, and any right in respect of any trade
    secret or other confidential information;

    'THE INVENTION' means the invention(s) claimed or disclosed in the Existing
    Patents;

    'MATERIALS' means any model, prototype, material or substance (including,
    without limitation, any living organism or genetic material), and includes
    any progeny or derivative of any of the foregoing;

    'THE NEGOTIATION PERIOD' means the period of [*] from the date of exercise
    of the First Option or the Second Option, as the case may be, or such longer
    period as the parties may agree in either case;

    'THE PROJECT' means the programme of collaborative research referred to in
    clause 5.1;

    'PROJECT TECHNOLOGY' means any Technology obtained, developed, found,
    produced or made at any time on or after the Effective Date in the course of
    the Project;

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.


                                     PAGE 3


<PAGE>   6
     'PROJECT PATENTS' means any patent applications claiming any Project
     Technology, any patents issued in pursuance of any such application, any
     extension, reissue, division, continuation or continuation-in-part of any
     such application or patent and any patent of addition, supplementary
     protection certificate or similar rights based on any such patent;

     'THE SECOND LICENCE' means the agreement to be entered into pursuant to
     clause 6.7;

     'THE SECOND OPTION' and 'THE SECOND OPTION PERIOD' have the meanings given
     in clause 6.6;

     'TECHNOLOGY' means any methods, techniques, processes, discoveries,
     inventions (whether patentable or not), formulae, results of
     experimentation, statistics, data, computer software or plans, any
     Materials and any records in any form relating to any of the foregoing; and

     'YEAR' means a period of 365 (or, in the case of a leap year, 366) days.

2.2  Unless the context otherwise requires, each reference in this Agreement
     to -

     (a)  'WRITING', and any cognate expression, includes a reference to any
          communication effected by facsimile transmission or similar means (but
          not electronic mail);

     (b)  a licence includes a sub-licence; and 'LICENSE' (as a verb) and
          cognate expressions shall be construed accordingly;

     (c)  a statute or a provision of a statute is a reference to that statute
          or provision as amended, re-enacted or extended at the relevant time,
          and includes any statute or a corresponding provision in a statute
          replacing that statute or provision;


                                     PAGE 4


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     (d)  'THIS AGREEMENT' is a reference to this Agreement and each of the
          Schedules, as amended or supplemented at the relevant time;

     (e)  a Schedule is a reference to a schedule to this Agreement;

     (f)  a clause or a paragraph is a reference to a clause of this Agreement
          (other than the Schedules) or a paragraph of the relevant Schedule;

     (g)  any reference to the parties includes a reference to their respective
          successors in title and permitted assignees;

     (h)  any reference to a person includes any body corporate, unincorporated
          association, partnership or other legal entity;

     (i)  the singular includes the plural and vice versa; and

     (j)  words importing any gender include any other gender.


2.3  The headings in this Agreement are for convenience only and shall not
     affect its interpretation.

3    GRANT OF THE FIRST OPTION

3.1  ICRT hereby grants to Introgen, on and subject to the terms of this
     Agreement, the exclusive option to obtain an exclusive, world-wide licence
     (to the extent that ICRT is able to grant such a licence under any
     applicable law) in respect of the Existing Patents and any Materials or
     other Existing Technology referred to in clause 5.4, on the terms referred
     to in clause 4.1.

3.2  The First Option shall be exercisable by Introgen, subject to payment of
     the sum referred to in clause 3.3, by giving written notice to ICRT at any
     time during the First Option Period.


                                     PAGE 5


<PAGE>   8

3.3  In consideration of the grant of the First Option, Introgen shall pay to
     ICRT the sum of [*] on the Effective Date.

3.4  The sum referred to in clause 3.3 shall not be refunded in any
     circumstances.

3.5  If Introgen does not duly exercise the First Option during the First
     Option Period, it shall forthwith lapse.

3.6  During the First Option Period ICRT shall diligently prosecute and maintain
     the Existing Patents and keep Introgen fully informed as to the prosecution
     status of the Existing Patents (including, without limitation, furnishing
     to Introgen information relevant to such prosecution and maintenance) and
     shall give fair consideration to suggestions made by Introgen in respect of
     the prosecution strategy in so far as they relate to the Field, but if ICRT
     notifies Introgen in writing that -

     (a)  it wishes to abandon any patent application or patent within the
          Existing Patents which relates to the Field, it shall give a prompt
          written notice Introgen offering to assign it to Introgen at the
          expense of Introgen but otherwise free of charge, and if Introgen does
          not accept the offer in writing within 30 days, ICRT shall have no
          further obligation with respect to the patent or patent application;
          or

     (b)  it does not wish to elect to proceed from PCT stage to national stage
          with respect to any such application in any country, it shall give a
          prompt written notice to Introgen, and ICRT shall have no further
          obligation with respect to the application unless Introgen notifies
          ICRT in writing within thirty (30) days that it wishes ICRT so to
          proceed, in which event ICRT shall do so but at the sole expense of
          Introgen, and accordingly for the purposes of -

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.



                                     PAGE 6


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          (i)  clause 3.7(b), that application and any Existing Patent granted
               pursuant to it in the relevant country shall be treated as if
               they had been assigned to Introgen; and

          (ii) the provisions of the First Licence as to royalties summarised in
               paragraph 9 of Schedule 2, that application and any Existing
               Patent granted pursuant to it shall be deemed not to exist in the
               relevant country.

3.7  During the First Option Period the out-of-pocket costs and expenses of
     prosecuting and maintaining the Existing Patents shall be borne -

     (a)  in respect of any of the Existing Patents the claims of which relate
          exclusively to any matter outside the Field, by [*];

     (b)  in respect of any of the Existing Patents the claims of which relate
          exclusively to the Field, or which have been assigned to Introgen
          pursuant to clause 3.6(a) (or are treated as if they had been so
          assigned pursuant to clause 3.6(b)(i), [*];

     (c)  in respect of any other of the Existing Patents, by [*];

     and Introgen shall accordingly pay to ICRT the [*] of those
     costs and expenses incurred from time to time within 30 days after receipt
     from ICRT of an account setting out the relevant information to enable its
     share to be ascertained.

4    EXERCISE OF THE FIRST OPTION

4.1  If Introgen exercises the First Option in accordance with clause 3.2, ICRT
     and Introgen shall forthwith use their best endeavours during the
     Negotiation Period to negotiate in good faith the terms and conditions for
     the grant to Introgen of the

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.


                                     PAGE 7


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     licence referred to in clause 3.1 ('THE FIRST LICENCE'), which shall
     include the terms and conditions set out in Schedule 2 and such other terms
     and conditions (consistent with those set out in Schedule 2) as are
     reasonable and customary in the biopharmaceutical industry for arrangements
     of the type contemplated by the First Licence.

4.2  Upon agreement being reached between ICRT and Introgen as to the terms of
     the First Licence, the parties shall forthwith execute an agreement
     containing the terms so agreed between ICRT and Introgen.

4.3  If, notwithstanding their best endeavours, ICRT and Introgen do not agree
     upon the terms for the grant of the First Licence to Introgen during the
     Negotiation Period, Introgen shall have the right, exercisable by notifying
     ICRT in writing at any time within fifteen (15) days after the expiration
     of the Negotiation Period, to initiate a binding arbitration proceeding,
     pursuant to which the terms and conditions of the First Licence shall be
     established. Any arbitration under this provision shall be held in
     accordance with clause 9.12 by a single arbitrator and the sole issue
     before such arbitrator shall be to establish the terms and conditions of
     the First Licence in accordance with clause 4.1, to the extent that they
     have not been agreed. If Introgen does not exercise the foregoing right to
     initiate arbitration within the applicable fifteen (15) day period, the
     First Option shall lapse.

4.4  If the First Option lapses pursuant to clause 3.5 or 4.3 then, except to
     the extent that clauses 5, 6 and 7 continue to operate, this Agreement
     shall terminate automatically, in which case all rights and obligations of
     the parties shall terminate except as provided in clause 8.4.

5    THE PROJECT

5.1  As further consideration for the grant of the First Option, Introgen shall
     co-operate with ICRT on a programme of collaborative research on the
     following terms.

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5.2  Subject to the following provisions, the Project shall be carried on for a
     period of [*] from the Effective Date.

5.3  The overall objectives of the Project shall be as set out in Schedule 3.
     Within those overall objectives, the detailed objectives and implementation
     of the Project, and the work to be carried out by ICRT and Introgen
     respectively as part of the Project, shall be as agreed between Dr David
     Snary of ICRT and Dr Sunil Chadaof Introgen from time to time, but
     initially as set out in the document attached to this Agreement as Appendix
     A and initialled on behalf of the parties.

5.4  ICRT shall, as soon as practicable after the Effective Date -

     (a)  Supply to Introgen samples of such of the Materials relating to the
          Gene and in the possession or control of ICRT as are reasonably
          necessary to enable Introgen to carry its tasks in relation to the
          Project or as are otherwise requested by Introgen from time to time in
          connection with its evaluation of the Gene with a view to deciding
          whether or not to exercise the First Option or the Second Option; and

     (b)  disclose to Introgen such other of the Existing Technology as is
          relevant to the Project or it exercise of the First Option or the
          Second Option;

    and Introgen shall be entitled to use and practice the Invention, and to use
    any Materials so supplied and any Existing Technology so disclosed during
    the continuance of the Project, for the purposes only of carrying out its
    part of the Project and planning the development and exploitation in the
    Field of the Existing Technology and Project Technology or as otherwise
    reasonably necessary to evaluate the Gene with a view to deciding whether or
    not to exercise the First Option or the Second Option.

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.


                                     PAGE 9


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5.5  Subject as provided in clause 5.4, the resources to be applied to the
     Project by each of ICRT and Introgen shall be solely at its discretion.

5.6  Introgen shall pay to ICRT, as a contribution to the work to be carried out
     by ICRT as part of the Project, the sum of [*].

5.7  For the avoidance of doubt, each sum payable pursuant to clause 5.6 shall
     not be refunded in any circumstances, and if Introgen exercises the First
     Option before the end of that period, any such sum which is outstanding
     shall continue to be payable.

5.8  [*].

5.9  If within [*] from the Effective Date Introgen has not commenced good
     faith active steps with a view to carrying out its part of the Project for
     any reason, ICRT shall be entitled to terminate the Project by giving to
     Introgen not less than [*] written notice provided that Introgen
     does not commence such steps within such [*] period, in which
     case the parties shall forthwith take such steps as may be necessary to
     terminate the Project, and subject to those steps being taken this
     Agreement shall terminate automatically.

5.10 For the purposes of the Project the principal points of contact between the
     parties will be as follows -

          for ICRT:                  Dr David Snary

          for Introgen:              Dr Sunil Chada

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.



                                     PAGE 10




<PAGE>   13

5.11 ICRT and Introgen shall ensure that Dr Snary and Dr Chada respectively
     shall communicate and meet with one another as necessary to progress the
     work on the Project, and that each of them shall report their research data
     at semi-annual intervals in a short written report to Introgen and ICRT
     respectively.

5.12 If any employees or other representatives of ICRT are requested to visit
     the premises of Introgen for the purposes of the Project, Introgen shall -

     (a)  at its own cost give all reasonable assistance required by any of them
          for that purpose; and

     (b)  reimburse ICRT for their reasonable travel, accommodation and other
          expenses incurred, within 30 days after receipt of an invoice for the
          sum in question.

5.13 If by agreement with ICRT any employees or other representatives of
     Introgen visit the premises of ICRT for the purposes of the Project -

     (a)  ICRT shall at the cost of Introgen give all reasonable assistance
          required by any of them for that purpose, and Introgen shall reimburse
          to ICRT any out-of-pocket sum incurred by ICRT for that purpose
          within 30 days after receipt of an invoice for the sum in question;
          and

     (b)  Introgen shall be responsible for their travel, accommodation and
          other expenses.

6    OWNERSHIP OF TECHNOLOGY AND INTELLECTUAL PROPERTY

6.1  Subject to provisions of this Agreement, the Invention, the Existing
     Patents, the Existing Technology and all Intellectual Property in respect
     of any of the Existing Technology shall remain the exclusive property of
     ICRT.


                                     PAGE 11


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6.2  Any Project Technology, and any Project Patents or other Intellectual
     Property in respect of any Project Technology, shall -

     (a)  if made solely by ICRT staff working on the Project, belong
          exclusively to ICRT;

     (b)  if made solely by Introgen staff working on the Project, belong
          exclusively to Introgen;

     (c)  if made jointly by ICRT staff and Introgen staff working on the
          Project, belong to ICRT and Introgen jointly in equal undivided
          shares.


6.3  Except as otherwise provided in this Agreement and subject to the rights
     and licences granted herein, neither party shall have any obligation to
     account to the other for profits, or to obtain any approval or consent of
     the other party to license or exploit any Intellectual Property, by reason
     of their joint ownership of such Intellectual Property.

6.4  ICRT and Introgen shall discuss and seek to agree upon the extent to which,
     and the countries in which, patent protection for any Project Technology
     owned by ICRT or jointly owned by ICRT and Introgen should be obtained and,
     except to the extent that they otherwise agree in writing -

     (a)  the protection shall be applied for by ICRT in the name of ICRT, or
          jointly in the names of ICRT and Introgen, as the case may be;

     (b)  ICRT shall diligently prosecute and maintain the Project Patents in
          question and keep Introgen fully informed as to the prosecution status
          of the Project Patents (including, without limitation, furnishing to
          Introgen information relevant to such prosecution and maintenance) and
          shall give fair consideration to suggestions made by Introgen in
          respect of the prosecution


                                     PAGE 12


<PAGE>   15

          strategy in as far as they relate to the Field, but if ICRT notifies
          Introgen in writing that -

          (i)  it wishes to abandon any such patent application or patent, it
               shall give a prompt written notice to Introgen offering to assign
               it to Introgen at the expense of Introgen but otherwise free of
               charge, and if Introgen does not accept the offer in writing
               within 30 days, ICRT shall have no further obligation with
               respect to the patent or patent application in question; or

          (ii) it does not wish to elect to proceed from PCT stage to national
               stage with respect to any such application in any country, it
               shall give a prompt written notice to Introgen;


     (c)  where ICRT gives such a notice pursuant to clause 6.4(b)(ii) above,
          ICRT shall have no further obligation with respect to the application
          unless Introgen notifies ICRT in writing within 30 days that it
          wishes ICRT so to proceed, in which event ICRT shall do so but at the
          sole expense of Introgen, and accordingly for the purposes of -

          (i)  clause 6.4(d), that application and any Project Patent granted
               pursuant to it in the relevant country shall be treated as if
               they had been assigned to Introgen; and

          (ii) the provisions of the First Licence as to royalties summarised in
               paragraph 9 of Schedule 2 (as they apply to Project Patents
               pursuant to paragraph 3 of Schedule 4), that application and any
               Existing Patent granted pursuant to it shall be deemed
               not to exist in the relevant country;


                                     PAGE 13


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     (d)  the out of pocket costs and expenses of prosecuting and maintaining
          the Project Patents in question shall be borne, as if they were
          Existing Patents, in the manner provided in clause 3.7 which shall
          apply with the necessary changes (and so that the reference therein to
          clause 3.6(b)(i) shall be deemed to be a reference to clause
          6.4(c)(i));

     (e)  Introgen shall keep ICRT informed as to the prosecution status of all
          patent applications within the Project Patents owned by Introgen; and

     (f)  each of ICRT and Introgen shall give the other such assistance as the
          other may reasonably require and at the other party's expense in order
          to obtain and maintain such protection.

6.5  ICRT hereby grants to Introgen the exclusive option to take an exclusive
     licence under any or all of the Project Patents and Project Technology
     owned exclusively by ICRT and the exclusive right to exploit any and all
     Project Patents owned jointly by ICRT and Introgen.

6.6  The option granted under clause 6.5 ('THE SECOND OPTION') shall be
     exercisable by Introgen by giving written notice to ICRT at any time during
     the period ('THE SECOND OPTION PERIOD') of [*] after the termination of the
     Project (except where this Agreement is terminated by ICRT pursuant to
     clause 8.2 or 8.3).

6.7  If Introgen exercises the Second Option in accordance with clause 6.6, the
     First Licence shall be modified to include such Project Patents and Project
     Technology within the scope of the First Licence, in accordance with the
     provisions of Schedule 4, and ICRT and Introgen shall forthwith execute an
     agreement ('THE SECOND LICENCE') to effect such a modification. In the
     event of any disagreement as to the terms of the Second Licence, the
     provisions of clause 4.3 shall apply with the necessary changes.

      [*] Certain information on this page has been omitted and filed
          separately with the Commission. Confidential treatment has been
          requested with respect to the omitted portions.

                                     PAGE 14


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6.8  Notwithstanding any licence or right granted by ICRT pursuant to this
     Agreement, ICRT (for itself and ICRF) shall retain -

     (a)  the exclusive right to use any Existing Technology (and any Existing
          Patents or other Intellectual Property in respect thereof) for any
          purpose outside the Field;

     (b)  the exclusive right to use any Project Technology which belongs
          exclusively to ICRT (and any Project Patents or other Intellectual
          Property in respect thereof), for any purpose outside the Field;

     (c)  the exclusive right to use any Project Technology which belongs to
          ICRT and Introgen jointly (and any Project Patents or other
          Intellectual Property in respect thereof) for [*]; and

     (d)  the non-exclusive right to use any Project Technology which belongs to
          ICRT and Introgen jointly (and any Project Patents or other
          Intellectual Property in respect thereof) for research and all other
          applications (except [*]) outside the Field.

6.9  Introgen hereby grants to ICRT (for itself and ICRF) an irrevocable,
     perpetual non-exclusive, worldwide, royalty-free licence, with the right to
     grant sublicenses, in respect of any Introgen Improvement, and any Project
     Patents or other Intellectual Property in respect of any such Introgen
     Improvement, for the purposes of research and the manufacture, sale and use
     of products for [*] outside the Field.

     For the purposes of this Agreement, 'Introgen Improvement' means any
     Project Technology which belongs exclusively to Introgen and which is a
     derivative (as defined in clause 2.1) of the Gene or a method of using the
     Gene (including derivatives thereof); provided, however, Introgen
     Improvements shall not include


         [*]    Certain information on this page has been omitted and filed
                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.




                                     PAGE 15


<PAGE>   18

     any vector, delivery system, method, compositions or other subject matter
     which is proprietary to Introgen, or any such Project Technology which
     necessarily involves or includes the use of or combination of any vector,
     delivery system, method, composition or other subject matter.

6.10 If Introgen does not duly exercise the Second Option during the Second
     Option Period, the Second Option shall lapse, and ICRT shall have the
     option, exercisable within a further [*] by giving written notice to
     Introgen, to negotiate for the grant to ICRT of an exclusive licence in
     respect of any Introgen Improvement, a non-exclusive licence in respect of
     any other Project Technology which belongs to ICRT and Introgen jointly,
     and all Project Patents or other Intellectual Property in respect thereof
     (but excluding any rights in respect of any vector, delivery system,
     method, compositions or other technology which is proprietary to Introgen,
     or any such Project Technology which necessarily involves or includes the
     use of or combination of any vector, delivery system, method), to use the
     same for any purpose, on a world-wide, royalty-bearing basis, to the extent
     that Introgen is able to grant such a licence or right.

6.11 If ICRT exercises the option referred to in clause 6.10, ICRT and Introgen
     shall forthwith use their best endeavours to negotiate in good faith the
     terms of an agreement for the grant of the licence or right within the
     period of [*] from the date of exercise of the option (provided that any
     such agreement shall contain the right for ICRT to grant licences (or
     sub-licences) under the Project Patents and Project Technology in question
     to any other person). In the event of any disagreement as to the terms of
     such agreement, the provisions of clause 4.3 shall apply with the necessary
     changes.

7    CONFIDENTIALITY AND PUBLICATION

7.1  Except as provided herein, each party shall maintain in confidence during
     the term of this Agreement and for seven (7) years thereafter, and shall
     not use for any


         [*]    Certain information on this page has been omitted and filed
                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.



                                     PAGE 16


<PAGE>   19

     purpose or disclose to any third party, any Technology or other information
     disclosed by the other party in writing and marked "Confidential" or that
     is disclosed orally and confirmed in writing as confidential within
     forty-five (45) days following such disclosure (collectively, 'CONFIDENTIAL
     INFORMATION'), except to the extent that any such Confidential
     Information -

     (a)  is at the time of being so provided or after that time through no
          fault of the party to whom it was so provided becomes public
          knowledge; or

     (b)  was lawfully available on a non-confidential basis to the party to
          whom it was so provided before that time; or

     (c)  can be shown by the party to whom it was so provided to have been
          independently produced by that party without any use of such
          confidential information provided to it by the other party; or

     (d)  is made available to the party to whom it was so provided otherwise
          than in breach of an obligation of confidentiality owed to the other
          party.

7.2  The results of the Project may be made public by either party (or, in the
     case of ICRT, by ICRF) except to the extent that -

     (a)  publication would include any Confidential Information of the other
          party; or

     (b)  publication would prejudice the obtaining of patent protection for an
          invention constituting Project Technology, or the commercial
          exploitation of any unpatented or unpatentable Project Technology
          which remains unpublished.

7.3  To allow time for review of any proposed disclosure of any subject matter
     which may be precluded from being made public under clause 7.2, each of
     ICRT and Introgen shall provide to the other -

                                     PAGE 17


<PAGE>   20

     (a)  a copy of any manuscript disclosing any results of the Project not
          less than 45 days notice before submitting the manuscript for
          publication; and

     (b)  a copy of any slides to be used in an oral presentation disclosing any
          results of the Project together with an outline of the presentation
          not less than 20 working days before making any such oral
          presentation.

7.4  The party receiving any such material pursuant to clause 7.3 shall promptly
     and in any event prior to the proposed date of submission for publication
     review the proposed disclosure and notify the other party in writing of its
     conclusions, failing which the other party shall be free to make the
     proposed disclosure.

7.5  If in the reasonable opinion of the party receiving the material the
     proposed disclosure does not include subject matter which is precluded from
     being made public under clause 7.2, it shall promptly notify the other
     party which shall thereupon be free to make the proposed disclosure.

7.6  If in the reasonable opinion of either party -

     (a)  the proposed disclosure includes subject matter which is precluded
          from being made public under clause 7.2 and which is patentable,
          neither party shall publish or otherwise disclose the material in
          question for a period of three months from the date on which the
          relevant material was received by the party in question and, if a
          patent application is made within that period of three months, for a
          further period as agreed but in any event not exceeding a total of 18
          months from that date (including such period of three months),
          following which the other party shall be free to make the proposed
          disclosure; or

     (b)  the proposed disclosure includes unpatented (or unpatentable) Project
          Technology which that party wishes to maintain as unpublished and
          which

                                     PAGE 18


<PAGE>   21
          has been identified in Project reports pursuant to clause 5.11 as
          being of potential commercial significance, neither party shall
          publish or otherwise disclose the material in question for a period of
          18 months from that date, following which either party shall be free
          to make the proposed disclosure; or

     (c)  the proposed disclosure includes Confidential Information of the
          reviewing party, the disclosing party shall remove such Confidential
          Information prior to such disclosure.

7.7  Notwithstanding the foregoing provisions of this clause 7 above, the
     receiving party may use or disclose Confidential Information of the
     disclosing party

     (a)  to the extent necessary to exercise its rights hereunder (including
          providing such information to bona fide licensees or prospective
          licensees as contemplated by this Agreement or otherwise and to
          potential investors or partners on reasonable terms of
          confidentiality) or to fulfil its obligations and/or duties hereunder;

     (b)  in filing for, prosecuting or maintaining any proprietary rights,
          prosecuting or defending litigation; and

     (c)  in complying with applicable governmental regulations and/or
          submitting information to tax or other governmental authorities; or as
          otherwise required by law;

     provided that if the receiving party is required by law to make any public
     disclosures of Confidential Information of the disclosing party then, to
     the extent it may legally do so, it shall give reasonable advance notice to
     the disclosing party of such disclosure and shall use its reasonable
     efforts to secure confidential treatment of


                                     PAGE 19

<PAGE>   22
          Confidential Information prior to its disclosure (whether through
          protective orders or otherwise).

     8    TERMINATION

     8.1  This Agreement shall be deemed to have come into force on the
          Effective Date and, subject to the following provisions, shall
          continue in force for the respective periods of time provided for in
          this Agreement and otherwise without any time limit.

     8.2  ICRT shall be entitled to terminate this Agreement forthwith by giving
          fifteen (15) days' prior written notice to Introgen if any sum payable
          under this Agreement is not paid in full within seven (7) days after
          the due date for payment and Introgen falls to make such payment
          within such fifteen (15) day period.

     8.3  Either party shall be entitled to terminate this Agreement forthwith
          by giving written notice to the other party if -

          (a)  the other party commits a breach of any of its obligations under
               this Agreement (other than, in the case of Introgen, a breach to
               which clause 8.2 applies) and, falls to remedy to breach within
               thirty (30) days after receiving a written notice from the first
               mentioned party specifying the breach and requiring it to be
               remedied; or

          (b)  the other party goes into liquidation, has a receiver appointed
               over any of its assets, has an administrator appointed, makes any
               voluntary arrangement with any of its creditors, or ceases to
               carry on business, or any similar event under the law of any
               foreign jurisdiction occurs in relation to the other party.


     8.4  On the termination of this Agreement for any reason (including, for
          the avoidance of doubt, any termination or partial termination
          pursuant to clause 4.4 or clause 5.9)


                                PAGE 20

<PAGE>   23
          (a)  the rights and obligations of Introgen under the First Licence
               (if it has been executed) and the Second Licence (if it has been
               executed) or of ICRT under any agreement entered into pursuant to
               clause 6.11 (if it has been executed) shall continue in force;

          (b)  subject to paragraph (a), Introgen shall forthwith cease all use
               of the Gene, the Invention, the Existing Technology and any
               Project Technology which belongs exclusively to ICRT, and destroy
               all Materials in the possession or control of Introgen which have
               been supplied by ICRT or produced or derived from any Materials
               so supplied;

          (c)  except to the extent that paragraph (a) above applies (and that
               accordingly this paragraph (c) does riot apply), ICRT shall be
               entitled to license the Existing Patents and the Existing
               Technology, any Project Patents (other than any of them which
               belong exclusively to Introgen) and any unpatented (or
               unpatentable) Project Technology (other than data which Introgen
               reasonably considers proprietary to itself) to any other person;

          (d)  the provisions of clause 6.1, 6.2, 6.3, 6.8, 6.9, 6.10, 6.11, 7,
               9.10, 9.11 and 9.12 shall continue in force in accordance with
               their terms,

          but subject to the foregoing, and except for any accrued right or
          obligation of either ICRT or Introgen, neither of them shall be under
          any further obligation to the other.


     8.5  Notwithstanding anything herein to the contrary, if either party
          disputes in good faith the other party's right to terminate this
          Agreement pursuant to the foregoing provisions of this clause 8 by
          reason of a breach by the other party, the other party's right to
          terminate shall be stayed unless or until it has been determined in
          accordance with clause 9.12 that such party has such a right and, if
          it is so determined, the party in breach has failed to remedy the
          breach in question within thirty (30) days after such determination.


                                PAGE 21

<PAGE>   24

     9    GENERAL

     9.1  This Agreement and the rights granted under it are personal to each
          party, which may not assign, transfer or charge to any other person
          any of its rights under this Agreement, or subcontract or otherwise
          transfer to any other person any of its obligations under this
          Agreement.

     9.2  Notwithstanding clause 9.1, either party may assign this Agreement
          and its obligations hereunder to a party that is an Affiliate of the
          assigning party at the time of the assignment or a party that succeeds
          to all or substantially all of its business or assets relating to this
          Agreement whether by sale, merger, operation of law or otherwise;
          provided that in either case such assignee promptly enters into an
          agreement in writing with the other party to be bound by the terms and
          conditions of this Agreement.

     9.3  ICRT warrants to Introgen that -

          (a)  except as disclosed in writing to Introgen, ICRT owns all right,
               title and interest in and to the Existing Technology, the
               Existing Patents and all other Intellectual Property of ICRT in
               respect of the Existing Technology and, subject to clause 9.4, it
               has the authority to enter into this Agreement and to grant the
               rights granted by it under this Agreement;

          (b)  the execution by ICRT of, and the performance of its obligations
               under, this Agreement require no governmental or other approvals
               or, if required, all such approvals have been obtained;

          (c)  it has not granted and, except as otherwise provided in this
               Agreement, will not during the continuance of this Agreement
               grant to any third party any rights which are inconsistent with
               the rights granted by it under or pursuant to this Agreement;


                                PAGE 22

<PAGE>   25

          (d)  except as disclosed in writing to Introgen, it is not aware of
               any third party claims or governmental restrictions (other than
               legal provisions of general application) which would restrict its
               ability to grant the rights agreed to be granted by it under this
               Agreement; and

          (e)  except for the Existing Patents, as at the Effective Date ICRT
               does not own or control any patents or patent applications the
               claims of which would dominate the practice of the rights to be
               granted to Introgen pursuant to this Agreement.

     9.4  Without limiting clause 9.3, ICRT does not warrant -

          (a)  the efficacy or usefulness of the Existing Technology or any
               Project Technology; or

          (b)  that the exercise of the rights granted under this Agreement will
               not infringe the patent or other Intellectual Property rights of
               any third party; or

          (c)  that any of the Existing Patents or Project Patents is or will be
               valid or enforceable, or (in the case of an application) will
               proceed to grant.

     9.5  Introgen warrants to ICRT that -

          (a)  it has the authority to enter into this Agreement and to grant
               the rights granted by it under this Agreement;

          (b)  the execution by Introgen of, and the performance of its
               obligations under, this Agreement require no governmental or
               other approvals or, if required, all such approvals have been
               obtained;

          (c)  it has not granted and, except as otherwise provided in this
               Agreement, will not during the continuance of this Agreement
               grant to any third party any


                                    PAGE 23

<PAGE>   26

               rights which are inconsistent with the rights granted by it under
               or pursuant to this Agreement; and

          (d)  it is not aware of any third party claims or governmental
               restrictions (other than legal provisions of general application)
               which would restrict its ability to grant the rights agreed to be
               granted by it under this Agreement.

     9.6  Subject to the terms of the First Licence (if executed), the Second
          Licence (if executed) or any agreement entered into pursuant to clause
          6.11, if either party becomes aware of any infringement of any of the
          Existing Patents or the Project Patents, or any claim is made or
          threatened against either party that the exercise of any rights
          granted under this Agreement infringes the patent or other
          Intellectual Property rights of any third party, it shall forthwith
          notify the other party, whereupon the parties shall consult and seek
          to decide what steps if any to take, and each of them shall give the
          other party (at the other party's expense) such assistance as the
          other party may reasonably request in connection therewith.

     9.7  Neither party nor its representatives or employees (or, in the case of
          ICRT, those of ICRF) shall be deemed in any circumstances to be the
          employees or representatives of the other party (or, in the case of
          ICRT, to be those of ICRF), or shall have any authority or power to
          bind the other party or to contract in its name.

     9.8  This Agreement contains the entire agreement between the parties with
          respect to its subject matter and may not be modified except by an
          instrument in writing signed by the duly authorised representatives of
          the parties, and each party acknowledges that, in entering into this
          Agreement, it does not do so in reliance on any representation,
          warranty or other provision, except as expressly provided herein, and
          any implied warranties are hereby excluded to the fullest extent
          permitted by law, but nothing in this provision shall affect the
          liability of either party for any fraudulent misrepresentation.

                                     PAGE 24

<PAGE>   27
     9.9  Except with regard to the exercise of the First Option and the Second
          Option, no failure or delay by either party in exercising any of its
          rights under this Agreement shall be deemed to be a waiver of that
          right, and no waiver by either party of a breach of any provision of
          this Agreement shall be deemed to be a waiver of any subsequent
          breach of the same or any other provision.

     9.10 If any provision of this Agreement is held by any court or other
          competent authority to be invalid or unenforceable in whole or in
          part, the other provisions of this Agreement and the remainder of the
          affected provision shall continue to be valid.

     9.11 This Agreement (and any licence to be entered into pursuant to this
          Agreement) shall be governed and construed in all respects in
          accordance with the laws of England, and the parties agree to submit
          to the non-exclusive jurisdiction of the English Courts.

     9.12 Any dispute or arising out of, in relation to, or in connection with
          this Agreement, or the validity, enforceability, construction,
          performance or breach hereof, shall be settled by binding arbitration
          in London, England, under the then-current Rules of Arbitration of
          the International Chamber of Commerce Court of Arbitration by a single
          arbitrator appointed in accordance with such rules, provided that if
          either party so requests (and unless otherwise provided hereunder) the
          arbitration shall be conducted by a panel of three (3) arbitrators
          appointed in accordance with the Rules. The decision and/or award
          rendered by the arbitrator(s) shall be written, final and
          non-appealable and may be entered in any court of competent
          jurisdiction. Accordingly, the parties hereby waive any and all rights
          of appeal to the Court under the Arbitration Act 1996. The parties
          agree that, any provision of applicable law notwithstanding, they will
          not request, and the arbitrator shall have no authority to award,
          punitive or exemplary damages against any party. The costs of any
          arbitration, including administrative fees and fees of the
          arbitrator(s), shall be shared equally by the parties, unless
          otherwise determined by the arbitrator(s). Each

                                    PAGE 25

<PAGE>   28
          party shall bear the cost of its own legal and expert fees; provided
          that the arbitrator(s) may in his or their discretion award to the
          prevailing party the costs and expenses incurred by the prevailing
          party in connection with the arbitration proceeding.

     10   NOTICES AND SERVICE

     10.1 Any notice or other information required or authorized by this
          Agreement to be given by either party to the other shall be given by -

          (a)  delivering it by hand;

          (b)  sending it by pre-paid registered post; or

          (c)  sending it by facsimile transmission or similar means of
               communication (but not electronic mail);

          to the other party at the address given in clause 10.4.

     10.2 Any notice or information sent by post in the manner provided by
          clause 10.1(b) which is not returned to the sender as undelivered
          shall be deemed to have been given on the seventh day after the
          envelope containing it was so posted; and proof that the envelope
          containing any such notice or information was properly addressed,
          pre-paid, registered and posted, and that it has not been so returned
          to the sender, shall be sufficient evidence that the notice or
          information has been duly given.

     10.3 Any notice or information sent by facsimile transmission or similar
          means of communication (but not electronic mail) shall be deemed to
          have been duly given on the date of transmission, provided that a
          confirming copy is sent as provided in clause 10.1(b) to the other
          party at the address given in clause 10.4 within 24 hours after
          transmission.


                                PAGE 26

<PAGE>   29

     10.4 The address of either party for service of any legal proceedings
          concerning or arising out of this Agreement, or for the purposes of
          clause 10.1, shall be that of its registered or principal office, or
          such other address as it may last have notified to the other party in
          writing from time to time.

     11   MISCELLANEOUS

     11.1 Each sum payable pursuant to this Agreement is exclusive of any
          applicable Value Added Tax or other taxes or duties (other than taxes
          on profits or income), which shall be additionally payable by Introgen
          together with the relevant sum.

     11.2 Each party shall from time to time do all such acts and execute all
          such documents as may be reasonably necessary in order to give effect
          to the provisions of this Agreement.

     11.3 The parties shall bear their own costs of and incidental to the
          preparation, execution and implementation of this Agreement.

     11.4 Except as required by law, neither party shall make any press or other
          public announcement concerning any aspect of this Agreement or use
          the name of the other (including, in the case of ICRT, that of ICRF)
          without first obtaining the agreement in writing of an authorised
          representative of the other party.

     11.5 This Agreement may be executed in more than one counterpart and shall
          come into force once each party has executed such a counterpart in
          identical form and exchanged it with the other party.


                                    PAGE 27

<PAGE>   30

                                    SCHEDULE 1

                              THE EXISTING PATENTS
<TABLE>
<CAPTION>
    TITLE                               COUNTRY              APPLICATION
                                                               NUMBER           DATE

<S>                                        <C>               <C>               <C>

[*]


</TABLE>


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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.




                                PAGE 28

<PAGE>   31
                                   SCHEDULE 2

                         THE TERMS OF THE FIRST LICENCE

1    Parties:       ICRT (the Licensor) and Introgen (the Licensee).


2    Definitions:   'LICENSED PRODUCT' will mean any product (i) which
                    incorporates the Gene, or (ii) the manufacture, use or sale
                    of which would in the absence of the licence granted to
                    Introgen infringe a valid claim within any of the Existing
                    Patents in the country for which the product is sold.

                    A "valid claim" will include the claims of issued patents
                    (including patents of addition, supplementary protection
                    certificates or similar rights based on any such patent) and
                    patent applications; provided that in the case of a patent
                    application which has not been issued, not more than [*]
                    have elapsed from the earliest priority filing date to which
                    the claim is entitled.

                    'LICENSED SUBJECT MATTER' will mean the Existing Technology,
                    the Existing Patents and any other Intellectual Property of
                    ICRT in respect of the Existing Technology.

                    Subject as provided above, the provisions of clause 2 shall
                    apply.

3    Licence:       ICRT will grant to Introgen an exclusive, worldwide licence,
                    with the right to grant and authorise sublicences, under the
                    Licensed Subject Matter to make, have made, use and sell
                    Licensed Products, practice any method, process or procedure
                    and otherwise exploit the Licensed Subject Matter, in each
                    case within the Field. For the avoidance of


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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.




                                PAGE 29
<PAGE>   32
                    doubt, Introgen will not have any rights in respect of any
                    [*] or in respect of any [*] outside the Field.

4    Retained       Notwithstanding the foregoing, ICRT (for itself and ICRF)
     Rights:        will retain the rights under the Licensed Subject Matter
                    referred to in clause 6.8.

5    Clinical       Introgen will be responsible for conducting, directly or
     Development:   through third parties, clinical development with respect to
                    Licensed Products. Such clinical development shall include
                    carrying out clinical trials sufficient to market a Licensed
                    Product in all Major Markets. Without limiting the
                    foregoing, Introgen will use the same diligent efforts to
                    initiate and complete such clinical trials as it expends for
                    its other products being developed with similar market
                    potential. The detailed plans and budgets for clinical
                    development will be determined by Introgen in consultation
                    with ICRT (and in default of agreement settled by
                    arbitration pursuant to clause 4.3) and set forth in the
                    Agreement. Introgen will consult with and keep ICRT
                    reasonably informed relating to the scope and progress of
                    such clinical development and will provide semi-annual
                    reports to ICRT on each stage of product development.

                    'MAJOR MARKET' will mean the [*], [*] and the [*].

6    Data Access:   During the term of the Agreement, Introgen will have access
                    to copies of data, reports, analyses and other information
                    in ICRT's possession or control, which are reasonably
                    necessary for Introgen's exercise of its rights under the
                    Licensed Subject Matter. In addition, ICRT will provide
                    Introgen with reasonable quantities of the Gene from time to


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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.



                                     PAGE 30

<PAGE>   33
                    time.

7    Licence Fee:   Introgen shall pay to ICRT on the execution of the First
                    Licence [*], which shall be non-refundable and
                    non-creditable against royalties.

8    Milestone      Upon the occurrence of the events set forth below for the
     Payments:      first Licensed Product, Introgen will make the corresponding
                    payment below to ICRT -

<TABLE>
<CAPTION>

         MILESTONE                            AMOUNT
         ---------                            ------
<S>                                           <C>
Completion of [*] trials                       [*]

Completion of [*] trials                       [*]

First approval for [*]                         [*]

First approval for [*]                         [*]

First year where Net Sales of a                [*]
Licensed Product exceeds [*]
    TOTAL                                      [*]
</TABLE>


9    Royalties:     Introgen will pay to ICRT as royalties the following
                    percentages of Net Sales by Introgen and its sublicensees,
                    based upon the aggregate Net Sales of all Licensed
                    Products -



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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.


                                     PAGE 31
<PAGE>   34
<TABLE>
<CAPTION>

                   Annual Net Sales   Royalties on Incremental
                   ----------------   ------------------------
                                               Amount
                                               ------

<S>                <C>                          <C>
                   [*]                           [*]

                   [*]                           [*]
</TABLE>


                    The foregoing royalties will be reduced by [*] in countries
                    where no valid claim of any of the Existing Patents covers a
                    Licensed Product.

                    In the event that Licensed Products are sold in combination
                    with one or more other registered products for which a
                    royalty would not otherwise be due, it is understood that
                    Net Sales from the combination product will be reasonably
                    allocated as to be set forth in the First Licence.

                    In the event Introgen, its affiliate or sublicensee becomes
                    obligated to pay a royalty to a third party in respect of
                    patent rights covering the Gene or use thereof such that the
                    total royalty burden on the Gene or use thereof (prior to
                    reductions) is in excess of [*] Introgen may deduct [*] of
                    such excess royalty from the royalty owing to ICRT on the
                    applicable net sales; provided, however, the royalty rate
                    payable on applicable net sales to such third party after
                    adjustments will not exceed the royalty rate payable (after
                    adjustments) to ICRT on such net sales (except with the
                    consent of ICRT, which consent will not be unreasonably
                    withheld) and in no case will the amount paid to ICRT be so
                    reduced to less than [*] of the amount that would otherwise
                    be due to ICRT on such net sales.

                    Each royalty payment will be accompanied by a proper
                    statement and will be made without deduction. Introgen will
                    keep proper accounts


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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.



                                    PAGE 32

<PAGE>   35
                    to enable the accuracy of royalty payments to be confirmed,
                    and will allow ICRT access to inspect and take copies.

10   Marketing:     Introgen will be responsible for the establishment, control
                    and implementation of the promotion and marketing strategy,
                    plans and budgets for Licensed Products. Introgen will use
                    the same diligent efforts with respect to the marketing,
                    sale and promotion of Licensed Products for each Major
                    Market as Introgen expends for its own products being
                    developed with similar market potential.

11   Patent         The provisions of clauses 3.6 and 3.7 above will apply
     Prosecution:   throughout the term of the First Licence as they apply
                    during the First Option Period.

12   Miscellaneous: Each party will keep Confidential Information of the other
                    confidential on the same terms as under clause 7 above.

                    The First Licence will be subject to termination on the
                    same terms as under clause 8 above. On termination all
                    rights will revert to ICRT.

                    Introgen will assume responsibility for the exploitation of
                    the Licensed Subject Matter and will indemnify ICRT (and
                    ICRF) accordingly. ICRT (or ICRF) will have no liability
                    howsoever arising under or in connection with the First
                    Licence for loss of profit or indirect or consequential loss
                    or for sums exceeding the amount of royalties paid by
                    Introgen.

                    Clauses 9, 10 and 11 above will apply to the First Licence.

                    The First Licence will include other reasonable and
                    customary terms and conditions contained in similar
                    agreements of this type, in so far

                                     PAGE 33

<PAGE>   36


                    as they are consistent with the above.








                                     PAGE 34

<PAGE>   37

                                   SCHEDULE 3

                            OBJECTIVES OF THE PROJECT


                                      [*]








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                separately with the Commission. Confidential treatment has been
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                                     PAGE 35

<PAGE>   38
                                   SCHEDULE 4

                         THE TERMS OF THE SECOND LICENCE

     1    'LICENSED SUBJECT MATTER' will include, in addition to the Existing
          Patents and Existing Technology, any Project Technology and Project
          Patent owned exclusively by ICRT or owned jointly by ICRT and
          Introgen.

     2    'LICENSED PRODUCT' will mean any product (i) which incorporates the
          Gene, or (ii) the manufacture, use or sale of which would in the
          absence of the licence granted to Introgen infringe a valid claim
          within any of the Existing Patents or the Project Patents owned
          exclusively by ICRT or owned jointly by ICRT and Introgen (or, in the
          latter case, would do so if the Project Patent in question was owned
          exclusively by ICRT) in the country for which the product is sold.

     3    Royalties will be payable, at the rates specified in Schedule 2, on
          Net Sales of Licensed Products (as defined above), where the product
          (i) incorporates the Gene or (ii) is covered by a valid claim of an
          Existing Patent or a Project Patent owned exclusively by ICRT. The
          foregoing royalties will be reduced by [*] in countries where no valid
          claim of an Existing Patent or a Project Patent owned exclusively by
          ICRT covers a Licensed Product.

     4    Clauses 6.3, 6.4, 6.8 and 6.9 shall apply throughout the term of the
          Second Licence.

     5    Subject to paragraphs 1 to 4 above, the provisions of Schedule 2 shall
          apply with the necessary changes (and so that references to Existing
          Technology and Existing Patents shall be construed as references to
          Existing Technology and Existing Patents and/or Project Technology and
          Project Patents owned exclusively by ICRT or owned jointly by ICRT and
          Introgen).



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                separately with the Commission. Confidential treatment has been
                requested with respect to the omitted portions.




                                     PAGE 36

<PAGE>   39

     For  IMPERIAL CANCER RESEARCH TECHNOLOGY LIMITED


     /s/ JOHN C. WALL
     --------------------------------
     Director




     For  INTROGEN THERAPEUTICS, INC.


     /s/ MAHENDRA G. SHAH
     --------------------------------
     Director


                                    PAGE 37