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                                                                   Exhibit 10.51



                              LICENSING AGREEMENT

                                    BETWEEN

                          ARONEX PHARMACEUTICALS, INC.

                                      AND

                            BOEHRINGER MANNHEIM GMBH
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                                   AGREEMENT

     This agreement effective as of ______________, 19__, by and between
BOEHRINGER MANNHEIM GmbH, a corporation organized and existing under the laws of
_________________ (hereinafter called "BM") having its principal office at
___________________________________ ________________________________ and ARONEX
PHARMACEUTICALS, INC., with offices located at 3400 Research Forest Drive, The
Woodlands, Texas 77381 (hereinafter called "Aronex").

     WHEREAS Aronex is the exclusive licensee or owner of certain technology
related to the combination of a Pseudomonas exotoxin combined with an erbB2
ligand capable of targeting the erbB2 antigen;

     WHEREAS BM is desirous of exclusively licensing and sublicensing Aronex's
technology, contingent upon results of its own studies of the specificity of the
e23 antibody;

     WHEREAS BM is willing to undertake research efforts directed toward
developing Aronex's technology and to commit such financial and scientific
resources, facilities, equipment and materials as reasonably necessary to that
end;

     NOW WHEREFORE the parties agree.

                                   ARTICLE I

                                  DEFINITIONS

1.1     "Technology" shall mean that technical information owned by or licensed
to Aronex related to the combination of a Pseudomonas exotoxin, or a derivative
thereof (hereinafter referred to as PE), with erbB2 ligand or portion(s) thereof
capable of targeting the erbB2 antigen.

1.2     "Field" shall mean the use of the Technology as a cancer therapy.

1.3     "Licensed Product(s)" shall mean compounds and methods of therapy
utilizing the Technology within the Field.

1.4     "Specialties" means finished pharmaceutical preparations in dosage form
which contain a Licensed Product as an active ingredient.

1.5     "Patent Rights" shall mean the patent applications and patents as set
forth on Appendix A attached hereto.  Within the definition of Patent Rights any
continuations, continuations-in-part, divisions, patents of addition, reissues,
renewals of extensions shall also be included.
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1.6     "Licensed Right" shall mean, with respect to the Field of use, the right
and license to use Aronex Know-How, any Patent Right and any application for a
Patent Right that encompasses the claims incorporating the Aronex Know-How, to
make, have made, use and sell the Licensed Product.

1.7     "Net Sale" shall mean the gross sales price of the Specialties sold by
BM and its sublicensees to independent third parties, less discounts, rebates,
returns, credits, sales taxes and other governmental charges, all of which shall
be covered by a lump sum of 7.5% to be deducted from such actual gross amount
invoiced.  In case BM can demonstrate by convincing documentation that this
aggregate amount of deductions referred to exceeds the lump sum of 7.5%, then
the parties shall agree in good faith on a reasonable adjustment of this
percentage

1.8     "Subsidiary" means any company in the Territory, in which company BM
controls, or either directly or indirectly owns at least fifty percent of the
equity capital.  Unless the context otherwise requires, the rights granted under
this Agreement to BM shall be extended to any of its Subsidiaries, provided that
such Subsidiary shall observe all of the relevant provisions of this Agreement.

1.9     "Territory" shall mean all countries of the world.

                                  ARTICLE II

                                GRANT OF LICENSE

2.1     License.  Aronex grants to BM an exclusive license to make, have made,
use, import, export, distribute for sale and to offer to sell the Licensed
Products in all territories of the world (the "Territory") the Technology within
the Field (collectively referred to as the "License").

2.2     Co-Promotion.  Aronex shall have an option for co-promotion rights
within the U.S. wherein said option may be exercised by Aronex providing BM with
written notice of its intent within six (6) months after NDA filing and by
paying BM $2,000,000 U.S. dollars within the first four (4) years following
first product sales of the Specialties in the U.S. in equal amounts of five
hundred thousand ($500,000) U.S. dollars.  The payments may be made as either a
cash payment, credited against owed royalties, or a combination of cash and
royalty credit during each calendar year after notice of exercise of co-
promotion rights.  Co-promotion rights are defined as the right of Aronex to
provide a reasonable percentage of sales effort directed to the marketing and
sales of the Specialties under the same trade name, trademark, logo, labeling or
other means of identifying the Specialties to the relevant consumer as is used
by BM, and to receive a reasonable and customary return of gross sales
commensurate with the marketing and sales effort provided by Aronex.  The terms
of the agreement defining the co-promotion relationship between the parties
shall be negotiated in good business faith and shall be commensurate with
similar terms as utilized under industry standards wherein said negotiation
shall be initiated within six (6) months of filing an NDA and completed within
90 days of initiation of said negotiations.

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2.3     Co-Marketing. If the parties are unable to come to a mutually acceptable
agreement under Aronex's option to co-promote the Specialties as provided above,
Aronex shall have a first right to negotiate for co-marketing rights within the
U.S.  Co-marketing rights are defined as the right of Aronex to market
Specialties under its own tradename, trademark, logo, labeling or other means of
identifying the Specialty to the relevant consumer.  Aronex may negotiate said
first right by providing BM with written notice of its intent within nine (9)
months after NDA filing.  The terms of the agreement defining the co-marketing
relationship between the parties shall be negotiated in good business faith and
shall be commensurate with similar terms as utilized under industry standards,
wherein said negotiation shall be completed within 90 days of initiation of said
negotiation.  Such co-marketing terms shall at least include the right of Aronex
to purchase the Specialties from BM at BM's reasonable costs of production, in
order to ensure that Aronex shall not be placed at a commercial disadvantage to
BM or any third party purchasing Specialties from BM.  In the event the parties
cannot agree on a co-promotion or a co-marketing agreement, the parties agree to
arbitration as defined in 14.2.

2.4     Successors and Assigns.  Pursuant to a sale, merger, or transfer of all
or substantially all of Aronex' assets to a third party, the right to co-promote
under paragraph 2.2, but not the right to co-market under paragraph 2.3 above
shall accrue to the benefit of the third party.  Additionally, in the case of
such a transfer or sale of assets, should BM and the third party transfer be
unable to come to a mutually acceptable agreement under the third party
transferee's option to co-promote the specialties under paragraph 2.2, the
disagreement shall be submitted for arbitration as defined in paragraph 14.2

2.5     Sublicense.  BM shall have the right to assign or sublicense its rights
hereunder; provided, that (i) the rights or Aronex hereunder shall not be
derogated, (ii) BM shall guaranty the performance of the sublicensee.

2.6     Reservation of Rights.  Aronex shall retain all rights in the Technology
in the Field, otherwise not expressly granted hereunder, including but not
limited to the use of the erbB2 ligand alone or in combination with molecules
other than exotoxins.

2.7     Exclusivity.  With the exception of research performed in the European
Common Communities, Aronex shall not conduct, have conducted, or fund any
research, development, or marketing activity of the Technology within the Field
during the Term of this Agreement except pursuant to this Agreement.

                                  ARTICLE III

                        RESEARCH AND DEVELOPMENT PROGRAM

3.1     Best Research Efforts.  BM shall use its commercially reasonable
research efforts according to the Research Schedule as set forth in Appendix B
(the "Research Program"). BM shall commit to the Research Program such financial
and scientific resources, facilities, equipment, personnel and materials as BM
within its reasonably exercised discretion deems necessary to achieve

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the milestones set forth. Such best efforts by BM shall be no less than those
efforts BM would reasonably undertake to demonstrate the commercially-useful
specificity of an antibody of its own design. BM shall commit to the Research
Program such financial and scientific resources, facilities, equipment,
personnel and materials as deemed necessary by the parties to achieve the
milestones set forth in Appendix B. As provided for herein, and as necessary to
achieve those milestones, BM shall have access to all Technology, whether owned
or licensed by Aronex, for use in the Field.

3.2     Research Progress Reports.  BM shall provide Aronex with progress
reports twice annually within thirty (30) days following the end of the second
(2nd) and fourth (4th) calendar quarters. These reports will describe the
progress made in the Research Program in sufficient detail to allow an
independent normally-skilled scientist to repeat all work accomplished.  Aronex
will agree to maintain secrecy and confidentiality regarding any information
provided by BM which may impact its intellectual property.

                                  ARTICLE IV

                           MARKETING AND MANUFACTURE

4.1     Promotion.  BM shall use  commercially reasonable efforts to develop and
expand a market and to sell diligently throughout the entire Territory the
Licensed Product, and Specialties.

4.2     Conflicting Sales.  Aronex shall exercise its  reasonable efforts and
due diligence to prevent, and cause the prevention of, the sale or use of any
Licensed Product or any Licensed Right  within the Field of Use in the
Territory.

4.3     Manufacturing.  BM shall manufacture Licensed Products or Specialties
pursuant to the grant provided herein.  If Aronex chooses to co-market in the
United States, BM shall sell such Licensed Product and/or Specialty to Aronex at
BM's reasonable cost of production in order to insure that Aronex is not placed
at a commercial disadvantage to BM, a sublicensee, an affiliate, or any other
third party.

                                   ARTICLE V

                   UPFRONT EXECUTION FEES/MINIMUM ANNUAL FEES

5.1     Upfront License Execution Fee.  In consideration for the License, BM
shall pay to Aronex an upfront payment of $150,000 U.S. dollars wherein said
payment shall be made in two separate installments as follows:  (a) BM shall pay
to Aronex a non-refundable payment of $25,000 U.S. dollars within thirty (30)
days of the execution of this agreement, and (b) upon BM's decision to proceed
with this Agreement based upon the results of the specificity studies, BM shall
pay to Aronex $125,000 U.S. dollars wherein said payment shall be made within
three (3) months from the date of execution of this Agreement, but no later than
March 3, 1997. The initial $25,000 payment shall be non-refundable and shall be
retained by Aronex in the event that BM determines not to proceed with this
Agreement.  In the event that BM determines to proceed with this

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Agreement by payment of the balance to the upfront fee, i.e., $125,000 U.S.
dollars, BM shall commit its know-how and related proprietary technology as well
as internal resources, both financial and material, towards the development of
the Technology for use in the Field according to the Research Program defined in
Appendix B.

5.2     Minimum Annual Licensing Fees.  BM further agrees to pay to Aronex a
minimum annual licensing fee of $100,000 U.S. dollars for the Term of the
Agreement with the first minimum annual payment due within thirty (30) days of
the first (1st) anniversary of the Agreement.  Each subsequent minimum annual
payment shall be due on the date of the anniversary of the agreement but may be
payable at any time within the following year but prior to the next occurring
anniversary date.

                                  ARTICLE VI

                               MILESTONE PAYMENTS

6.1     Milestone Payments.  BM will make payments to Aronex on the achievements
of certain milestones.  The milestone schedule contains two designated milestone
payment points as further consideration of the License.

     Milestone Schedule:                      Payment
     -------------------                      -------

     Commencement of Phase III               $  650,000
     human clinical trials

     Submission of NDA or equivalent to      $2,000,000
     U.S. FDA or European Regulatory
     Agency

6.2     Costs of Research.  BM shall fund all costs of the Research Program.

                                  ARTICLE VII

                                   ROYALTIES

7.1     Royalty Rate.

(a)  BM shall make incremental base royalty payments of its worldwide net sales
of seven percent (7%) on net sales for the first one hundred million U.S.
dollars (less than or equal to $100,000,000) and eight percent (8%) for all net
sales above one hundred million U.S. dollars (greater than $100,000,000) to
Aronex for access to any and all relevant patent(s) owned by or licensed to
Aronex covering the sale of the Products.

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(b)  In the event that BM is obligated to pay royalties to a third party in
respect to any Speciality, and the total royalty obligation is greater than
three percent (3%) above that owned to Aronex, the royalty payable to Aronex in
respect of that Speciality shall be reduced by an amount equal to 50% of the
royalty obligation to the third party wherein the maximum royalty reduction
shall be no more than 50% of the then current Aronex royalty due.

7.2     Payments.

(a)  BM will make written reports to Aronex biannually within sixty (60) days of
the end of each 2nd and 4th calendar quarter, and, if this Agreement terminates
on a date (the "Termination Date") other than the end of the 2nd or 4th calendar
quarter, within sixty (60) days of the Termination Date.

(b)  Royalties from BM shall be payable in currency of the United States of
America. The Royalty obligation of BM shall be determined by converting the
currency of the country in which the Net Sales generating the Royalties took
place into the currency of the United States of America at the conversion rate
established by official regulations in such country in force on the last day of
the calendar quarter for which Royalties are being paid; or, if there are no
such regulations, then at the closing middle rate on such date as certified by
Deutsche Bundesbank.

(c)  In the event the laws or regulations of a country in which Net Sales by BM
are made do not allow the remission of Royalties therefrom, or do not allow the
remission of the full amount of Royalties due under this Agreement, BM will pay
from some other source that amount of Royalties that are not remittable from
such country.

(d)  The parties understand that under the existing Double Taxation Treaty
between the United States and the Federal Republic of Germany no withholding tax
is being levied on royalty payments due hereunder at a late time, such
withholding tax shall be borne by Aronex. Should an exemption for withholding
tax purposes then be available under the laws of the Federal Republic of
Germany, a Double Taxation Treaty or any similar agreement in force at that
time, then BM shall use its best efforts to enable Aronex to obtain such
exemption.

     In case of deliveries of Licensed Products by BM to Aronex, the cost of
nationalization of such products, such as customs duties, the costs of customs
clearance and handling charges relating to the importation of License Products,
shall be borne by Aronex.

7.3     Royalty Term.  The Royalties according to Paragraph 4.1 shall be paid as
long as the production and sale of a Specialty would, in the absence of the
rights granted hereunder, represent an infringement of a patent within the
Patent Rights, provided, however, that the Royalties shall be payable for at
least a period of not less than ten (10) years commencing with the first
commercial sale of a Specialty.

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                                 ARTICLE VIII

                                    RECORDS

     BM shall keep complete and adequate books and records with respect to the
sale of Licensed Product and/or Specialties and Royalties payable hereunder.
Aronex shall have the right to have such pertinent books and records of BM
inspected and examined at all reasonable times for the purpose of determining
the correctness of royalty payments made hereunder.  Such inspection and
examination shall be done by the independent, certified, public accountant who
regularly audits the accounts of BM.  Such accountant shall not disclose to
Aronex any information other than that necessary to verify the accuracy of the
reports and payments made pursuant to this Agreement.  If the inspection
discloses that such Royalties were underreported by an amount equal to or
greater than five percent (5%) of the amount actually paid, BM shall reimburse
Aronex for the cost of such inspection.  It is understood that such examination
with respect to any quarterly accounting period hereunder shall take place no
later than three (3) years following the expiration of said period.

                                  ARTICLE IX

                                      TERM

9.1     Term.  The termination date of this Agreement shall be the earlier of
ten (10) years following commercial launch (first sale of a Licensed Product) or
the expiration of the last to expire of the licensed patents as defined in
Appendix A, including continuations or new applications arising from research
conducted under this Agreement (the period from the effective date until
termination date hereinafter referred to as the "Term").

9.2     Termination of this Agreement.

(a)  If either party fails to substantially perform any of its obligations or
undertakings to be performed under this Agreement and such default is not cured
within ninety (90) days after receipt of a written notice from the non-
defaulting party specifying the nature of the default or, if reasonably required
under the circumstances, within a longer period of time as reasonably determined
by the non-defaulting party, then the non-defaulting party shall have the right
to terminate this Agreement by giving written notice to the other party.

(b)  If either party should enter bankruptcy or otherwise become insolvent, or
if either party dissolves on otherwise winds up, then the other party shall have
the right to terminate this Agreement at any time by giving written notice to
the other party.

(c)  If either party, without cause at any time wishes to terminate the
Agreement, it may do so by written notice to the other party. However, in such
an instance, the remaining party shall receive all marketing rights and the
right to use all results of the Research Program and other efforts generated
under the Agreement.

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(d)  Aronex shall have the right to terminate this Agreement, if through failure
of BM to apply commercially reasonable efforts to the Research Program as
defined in Appendix B, BM fails to submit its bi-annual research progress
reports within sixty (60) days after their due date, or if BM fails to institute
phase I clinical trials by the second anniversary of the Effective Date of this
Agreement, provided, however, that Aronex will provide BM with written notice of
its intent to terminate the Agreement and BM fails to cure such failure within
ninety (90) days of said notice.

(e)  BM shall have the right to terminate this Agreement by giving Aronex sixty
(60) days notice if product development costs to be borne by BM under Article
3.1 hereof are materially greater than anticipated by BM, and if BM, within its
own reasonable exercised discretion, cannot be expected to continue the
development of the Licensed Product in view of these additional costs. In such
instance, Aronex will receive all marketing rights and the right to use all
results of the Research Program and other efforts generated by the program.

9.3  Rights and Duties of the Parties Upon Termination.

     Upon the termination of this Agreement, Aronex shall have the right to
retain any sums already paid, and BM shall pay all sums accrued hereunder that
are then due.  Payments to be made by either party under this Agreement shall
become due at the latest sixty (60) days after the termination or expiration of
this Agreement becomes effective, provided that the amount may be calculated at
that time.  If this is not the case, such payments shall become due as soon as
the amount can be calculated and such amount is correctly billed to the other
party.

     The termination or expiration of this Agreement for any reason whatsoever
shall be without prejudice to any obligations or rights on the part of either
party which have occurred prior to such termination and shall not affect or
prejudice any provision of this License Agreement which is expressly or by
implication provided to come into effect on, or continue in effect after such
termination.

                                   ARTICLE X

                              IMPROVEMENTS PATENTS

     BM hereby grants to Aronex and Aronex grants to BM a first right of refusal
to license, under terms reasonable and consistent with industry standards, any
improvements related to enhanced specificity of erbB2, including all patent
applications filed or patents obtained therein in the Territory.

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                                  ARTICLE XI

                  OBLIGATIONS REGARDING TECHNICAL INFORMATION

11.1     Nondisclosure.  The parties to this Agreement shall not reveal or
disclose to Third Parties any information received from the other Party under
any provision of this Agreement without its consent, except as may be required
for purposes of manufacturing, and marketing the Licensed Product or Specialties
and as may be required for securing essential or desirable authorizations,
privileges, or rights from agencies of government.  The confidentiality
obligation of this clause shall not extend to information that is in the public
domain at the time of the disclosure, becomes public after disclosure, is known
to BM at the time of the disclosure, or is subsequently disclosed to it by a
Third Party under no confidentiality obligation to the disclosing Party.  The
Parties shall take reasonable measures to assure that no unauthorized use or
disclosure is made by others to whom access to such information is granted.

11.2     Exchange of Information.  Each Party shall regularly inform the other
of any further information it obtains or develops regarding the medicinal
utility, method of manufacture, and safety of the Licensed Product and shall use
its best efforts to report to the other any confirmed information of serious or
unexpected adverse reactions reported in connection with the medicinal
administration of the Licensed Product.

                                  ARTICLE XII

                        INTELLECTUAL PROPERTY  OWNERSHIP

12.1     Division of Rights.  The ownership of all inventions made during the
term of this Agreement and/or during the course of the Research Program shall be
determined as follows:  all right, title and interest in and to any new
developments and to patentable improvements or modifications discovered during
the course of the Research Program shall be the property of the inventor(s) (or
their employers in accordance with employment agreements), and in the case of
joint inventorship between an employee of Aronex and an employee of BM (or any
third party evaluating any technology on behalf of BM), the invention shall be
the joint property of Aronex and BM.

12.2     Patent Prosecution Costs.  BM shall pay the cost associated with patent
prosecution relating to those patents and patent applications, for which such
costs are incurred beginning on January 1, 1996, but not to exceed $25,000 in
1996, licensed from the National Institute of Health and/or Dr. Ira Pastan
wherein said payments shall be credited against earned royalties.

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                                 ARTICLE XIII

                     INTELLECTUAL PROPERTY INDEMNIFICATION

13.1     Trademarks.  BM may choose and register its own trademarks for Licensed
Products and Specialties marketed under this Agreement and use whatever
trademark or trademarks (collectively, the "Trademarks") in the Territory they
wish, provided that they may not use any trademarks owned by the other party
without a specific license thereto in writing.  Aronex may choose and register
its own trademark for specialties provided Aronex elects to co-market pursuant
to Section 2.2 above.

13.2     Patent Litigation.  In the event BM becomes aware of any actual or
threatened infringement of any Patent Right, after consulting with Aronex, BM
may at its free discretion bring an action against a third party for patent
infringement for marketing products infringing a Patent Right licensed
hereunder, such an action shall be brought in BM's name and the cost of
prosecuting an infringement action shall be borne by BM alone.  Any net recovery
from prosecuting such action shall be divided between the parties in proportion
to their losses.  BM shall have control of any such patent litigation, but shall
keep Aronex posted on its progress, and consult with Aronex from time to time
concerning it and BM shall not settle any such action without Aronex's prior
consent.  If BM fails to prosecute such an action, Aronex may do so at Aronex's
own expense, and all monetary recovery gained from such action shall be retained
by Aronex.  In such event, BM may cooperate in the litigation at BM's expense.

13.3     Defense Against "Third Parties" Patent Claims.

     13.3.1  Mutual Information.  The parties shall immediately notify each
other if a claim or proceedings are brought against either party alleging that
the manufacture, distribution, sale or use of the Licensed Products under the
Licensed Technology infringes upon the Patent Rights of such a Third Party in a
country of the Territory.

     13.3.2   Defense of Third Party Action Brought Against BM;  Indemnification
of BM.

     13.3.2.1   If a claim or proceedings are brought against BM alleging that
the manufacture, distribution, sale or use of the Licensed Products in a country
of the Territory infringe upon the patent rights of such a Third Party, the
parties shall immediately consult on how to further proceed.  The final decision
whether or not and, as the case may be, how to defend or settle such claim or
proceedings shall be with Aronex.  Aronex shall have the right to join any such
proceedings as a party hereto at its own expense by counsel of its own choosing.

     13.3.2.2   Aronex shall indemnify and hold BM harmless against any such
claim or proceedings referred to in the preceding sub-paragraph brought against
BM, including reasonable attorneys fees, provided, however, that any obligations
to indemnify shall be excluded if BM fails to immediately notify Aronex of the
assertion of any such claims, and to entrust Aronex to conduct

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a respective lawsuit, and/or to adjust any such claims; and/or if BM recognizes
or settles part or all of any such claims without Aronex's prior written
consent.

     13.3.3   Defense of Third Party Action Brought Against Aronex and BM.  The
aforementioned stipulations shall apply accordingly in case Third Party patent
infringement action is being brought against both BM and Aronex.

13.4     Liability and Indemnification.

(a)  Aronex shall defend, indemnify and hold BM harmless from and against any
and all liabilities, losses, costs, damages and expenses (including reasonable
attorney's fees) which BM incurs arising in connection with (1) the human bodily
injury and/or death of any person caused by the use of a Licensed Product or
Specialties marketed or sold by Aronex, (2) the negligence of Aronex in the
manufacture, sale, marketing and distribution of Licensed Products or
Specialties and (3) the breach of any covenant or warranty made by Aronex and
set forth herein.

(b)  BM shall defend, indemnify and hold Aronex harmless from and against any
and all liabilities, losses, costs, damages and expenses (including reasonable
attorney's fees), which Aronex incurs, arising after the date hereof, in
connection with (1) the human bodily injury and/or death of any person caused by
the use of a Licensed Product or Specialties marketed or sold by BM, (2) the
negligence of BM in the manufacture, sale, marketing and distribution of
Licensed Products or Specialties and (3) the breach of any covenant of BM set
forth in this Agreement.

(c)  A Party seeking indemnification hereunder shall give to the other Party
prompt notice upon the happening of any event which might give rise to a claim
for indemnification under Paragraph 9.3(a) or 9.3(b) above (an "Indemnifying
Event"). The failure of a Party to give such notice shall not prejudice the
right of such Party to be indemnified as herein provided, except to the extent
that such failure materially prejudiced the rights of the indemnifying Party.

(d)  The indemnifying Party shall, at its own expense, prosecute, defend
against, contest or otherwise dispose of the Indemnifying Event, with counsel
reasonably satisfactory to the indemnified Party, and each Party shall receive
from the other Party all necessary and reasonable cooperation in handling such
Indemnifying Event including the services of employees of the other Party who
are familiar with the facts relating to the Indemnifying Event. In the event
that the indemnifying Party fails to undertake such action promptly, the
indemnified Party shall have the right to undertake such action by counsel of
its own choosing, but at the cost and expense of the indemnifying Party. In the
event that the indemnifying Party undertakes such action in accordance with the
first sentence of this Paragraph 13.3(d), the indemnified Party may participate
in such action by separate counsel of its own choosing, at the cost and expense
of the indemnified Party. No indemnified Party shall have the right to settle or
compromise any Indemnifying Event without the written consent of the
indemnifying Party, which consent shall not be withheld or delayed unreasonably.

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     13.3.5   Third Party Licenses.

     13.3.5.1   If a claim or proceedings are brought against BM or Aronex
alleging that the manufacture, distribution, sale or use of the Licensed
Products in a country of the Territory infringe upon patent rights of such a
Third Party, then BM shall have the right to decide within its own reasonably
exercised discretion whether or not to take a license from that Third Party, as
well as under which conditions.

     13.3.5.2   Any such Third Party License Agreement shall be entered into
between BM and such Third Party; royalty payment due thereunder shall be owed
and made by BM only.

     13.3.5.3   Should BM decide to enter into any such Third Party License
Agreement and have to make royalty payments thereunder, then such royalties
shall be deductible from turnover royalties payable by BM to Aronex as provided
under Article 7.1.

                                  ARTICLE XIV

                                 MISCELLANEOUS

14.1     Notices.  Any notice required or permitted to be given under or in
connection with this Agreement or the subject matter hereof shall be given by
first class air mail, telex or telefax to the recipient at its address as shown
on the first page of this Agreement, or to any other address as may have
therefore been furnished in writing by the recipient to the sending party.  Any
such aforementioned notice or request shall be effective upon receipt by the
party to which it is addressed.

14.2     Agreement to Arbitrate.

(a)  Any dispute, controversy or claim arising out of, relating to or in
connection with this Agreement or the performance of non-performance of either
Party and any sublicensee and assignee hereunder shall be submitted to
arbitration under the rules and regulations of the American Arbitration
Association. The Parties shall bear their own expenses in connection with any
such arbitration. The cost and expenses of such arbitration shall be borne by
the Parties equally unless the determination by the panel of arbitrators
includes an award of costs, in which case, in accordance with such award;

(b)  In the event any actions are required to be taken by any Party to this
Agreement or under the rules and regulations of the American Arbitration
Association, the Party required to take such action shall do so within the time
periods required by such rules and regulations;

(c)  The decision and award of the panel of arbitrators shall be final and
conclusive upon the Parties, in lieu of all other legal, equitable or judicial
proceedings between them, and no appeal or judicial review of the award or
decision of the board of arbitrators shall be taken, but rather any such award
or decision may be entered as a judgment and enforced in any court having
jurisdiction over the party against whom enforcement is sought.

                                      -12-
<PAGE>

(d)  Arbitration shall take place in  the state of Delaware, U.S.A.

(e)  If either Party fails to abide by the provisions of this Paragraph 14.2 or
fails to pay any award thereunder, the other Party shall have the right to bring
such legal, equitable or judicial proceeding as is necessary to require the
Party so failing to comply with this Agreement.

14.3     Law Governing.  This Agreement shall be governed in all respects by the
laws of the State of Texas without regard to what the laws might apply under
applicable principles of choice of law and comity.

14.4     Complete Agreement.  This Agreement constitutes the complete agreement
between the Parties respecting the subject matter hereof, and supersedes all
prior written or oral undertakings between the Parties regarding the subject
matter hereof.

14.5     Amendments.  This document may be amended only by a writing executed by
both parties.

14.6     Construction; Severability.  The headings of the Paragraphs of this
Agreement are for convenience only, and shall not affect the construction
thereof.  All stipulations contained in this Agreement shall be so construed as
not to infringe the provisions of any applicable laws, but if any such
stipulation does infringe any such provision, the same shall be deemed void and
severable and shall be replaced by an appropriate provision conforming to such
law and reflecting the economical intentions of the parties hereto.

     In the event that the terms and conditions of this Agreement are materially
altered as a result of the preceding sub-paragraph, the parties shall
renegotiate the terms and conditions of this Agreement in order to resolve any
inequities.

                                      -13-
<PAGE>

     IN WITNESS WHEREOF, the Parties have executed this Agreement in two
counterparts, each of which shall constitute an original, with effective date as
first above written.

                 ARONEX PHARMACEUTICALS, INC.

                 By: /s/ James M. Chubb
                     ----------------------------------------------

                 Title: President
                       --------------------------------------------

                 Date:   December 3, 1996
                       --------------------------------------------


                 BOEHRINGER MANNHEIM GMBH

                 By: /s/ CLAUS-JORG RUETSCH
                    -----------------------------------------------

                 Title: Vice President, International Legal Affairs
                       --------------------------------------------

                 --------------------------------------------------

                 Date:   December 7, 1996
                      ---------------------------------------------



                 By:   /s/ GUNTHER SCHUMACHER
                    -----------------------------------------------

                 Title: Vice President, Research and Development
                       --------------------------------------------

                 Date:   December 10, 1996
                      ---------------------------------------------

                                      -14-
<PAGE>

                                                                      APPENDIX A


License L-318-91, Oncologix, Inc./Medical Oncology, Inc. erbB-2 License

USSN 07/341,361 (CIP of USSN 06/911,227, now abandoned), filed April 24, 1989,
entitled: "Recombinant Antibody Toxin Fusion Protein," Pastan et al.

USSN 07/865,722 (FWC of USSN 07/341,361), filed April 8, 1992, entitled:
"Recombinant Antibody Toxin Fusion Protein," Pastan et al.

USSN 08/461,825 (DIV of 07/865,722), filed June 5, 1995, entitled:  "Recombinant
Antibody Toxin Fusion Protein," Pastan et al.

USSN 08/463,163 (DIV of 007/865,722), filed June 5, 1995, entitled:
"Recombinant Antibody Toxin Fusion Protein," Pastan et al.

USSN 07/459,635 (now abandoned), filed January 2, 1990, entitled:  "Target-
specific, Cytotoxic, Recombinant Pseudomonas Exotoxin," Pastan et al.

USSN 07/938,559 (FWC of 07/459,835, now abandoned), filed August 28, 1992,
entitled:  "Target-Specific, Cytotoxic, Recombinant Pseudomonas Exotoxin,"
Pastan et al.

U.S. Patent Number 5,458,878 (USSN 07/522,562 (CIP of 07/459,635)), filed May
14, 1990, issued October 17, 1995, entitled:  "Target-Specific, Cytotoxic,
Recombinant Pseudomonas Exotoxin," Pastan et al.

USSN 08/461,233 (DIV of 07/522,563), filed June 5, 1995, entitled:  "Target-
Specific, Cytotoxic, Recombinant Pseudomonas Exotoxin," Pastan et al.

Background Licensed Patent Rights

U.S. Patent Number 4,892,827 (USSN 06/911,227), filed September 24, 1986,
entitled:  "Recombinant Pseudomonas Exotoxins Construction of an Active
Immunotoxin with Low Side Effects"

U.S. Patent Application Number 06/836,414, filed March 5, 1986, entitled:
"Human Gene Related to but Distinct From EGF Receptor Gene," Richter et al.
(see attached sheet)

L-211-84/0, Oncologix, Inc./Medical Oncology, Inc. EGF License
<PAGE>

                                                                      APPENDIX B

                           ERB B2 IMMUNOTOXIN PROGRAM
                           --------------------------

<TABLE>
<CAPTION>


                  TASK                        START         COMPLETE
<S>                                       <C>             <C>
1.  Specificity Studies                   September 1996  February 1997

2.  Histology Program                     February 1997   February 1998
     Specific construct
     Potency in-vitrolin-vivo
     Technical production feasibility

3.  Preclinical Program                   October 1997    July 1998
    In-vivo effocacy, toxicology,
           pharmacology:
     mouse
     monkey

4.  Clinical Development
          IND filed                                       October 1998

          Phase I                                         2 Years
          Phase II                                        1-1.5 Years
          Phase IIB

</TABLE>