Document:

EXHIBIT 10.17

CERTAIN INFORMATION IN THIS EXHIBIT IS SUBJECT TO A REQUEST FOR CONFIDENTIAL
TREATMENT. IN ACCORDANCE WITH RULE 406 UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, SUCH INFORMATION HAS BEEN OMITTED AND FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION. THE LOCATION OF SUCH OMITTED INFORMATION HAS
BEEN INDICATED WITH AN ASTERISK(*).

                                  CONFIDENTIAL
                              TANOX BIOSYSTEMS INC.

                     Settlement and Participation Agreement

     This Settlement and Participation Agreement ("Agreement") is entered into
effective as of July 8, 1996 ("Effective Date") between Tanox Biosystems, Inc.,
a Texas corporation, with its principal offices at 10301 Stella Link, Houston,
Texas 77025 ("Tanox") and F. Hoffmann-La Roche Ltd. with its principal offices
at CH-4070, Basal, Switzerland ("Roche"), Hoffmann-La Roche, Inc., Roche Holding
Ltd. and Roche Holdings, Inc., (collectively with Roche, the "Roche Entities").

     Tanox and the Roche Entities are parties to a lawsuit, Civil Action No.
H-94-0189, in the United States District Court for the Southern District of
Texas, Houston Division, styled TANOX BIOSYSTEMS. INC. V. GENENTECH. INC. ET
AL., resulting from the consolidation of Civil Action No. H-94-0239, styled
TANOX BIOSYSTEMS. INC. V. GENENTECH. INC., ET. AL. with Civil Action No.
H-94-0189, styled GENENTECH., INC. V. TANOX BIOSYSTEMS. INC. (the "Lawsuit"),
which they desire to settle.

     Tanox, Genentech, Inc. ("Genentech") and Ciba-Geigy Ltd. ("Ciba"), together
with the participation of Roche, also have reached an agreement in principle
under which Genentech and Tanox and Ciba would merge their respective anti-IgE
antibody projects. Such agreement has been memorialized in an Outline of Terms
which Tanox, Genentech, and Ciba are executing on the Effective Date and which
provides for the development and commercialization of one or more anti-IgE
products with the participation of Roche, should it exercise certain options
provided therein {the "Multiparty Transaction").

     Discussions relating to the Multiparty Transaction and settlement of the
Lawsuit also have culminated in an agreement between Tanox and Genentech
entitled Settlement and Cross-Licensing Agreement which has been executed prior
to or simultaneously with the Effective Date {the "Genentech Agreement") and in
certain additional agreements between Tanox and Roche relating to such
collaboration and to certain licensing relationships based on the Parties desire
to avoid the possibility of future disputes.

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     Therefore, Tanox and Roche agree as follows:

     1.0 DEFINITIONS. In addition 10 the words otherwise used as defined 1em1s
throughout this Agreement, the words set forth below will have the meanings
indicated when used in this Agreement.

     1.1 "AFFILIATE" shall mean (i) an organization fifty (50%) percent or more
of the voting stock of which is owned and/or controlled directly or indirectly
by either Party; (ii) an organization which directly or indirectly owns and/or
controls fifty percent (50%) or more of the Voting stock of either Party; (iii)
an organization which is directly or indirectly under common control of either
Party through common share holdings; or (iv) an organization as to which either
Party can demonstrate that the operation and management of such organization is
under the control, directly or indirectly, of the Party.

     1.2 "ALL CLAIMS" shall mean all existing and future claims, demands, and
causes of action, known or unknown pending or threatened, for all existing and
future damages and remedies (i) that arise out of or are in any way related to
the Incident and (ii) that were brought, could have been brought, or were sought
to be brought in the Lawsuit. Under this definition, "All Claims" includes but
is not limited to all claims, demands, lawsuits, debts, accounts, covenants,
liens, encumbrances, agreements, actions, counterclaims, cross-actions,
liabilities, obligations, losses, attorney's fees, costs, expenses, remedies,
and causes of action of any nature, whether in contract or in tort, or based
upon fraud or misrepresentation, breach of duty or common law, or arising under
or by virtue of any judicial decision, or federal, state or foreign statute or
regulation, for past present and future damages, property or economic damage,
and for all other losses and damages of any kind, including BUT NOT LIMITED TO
the following: all actual damages; all exemplary and punitive damages; all
penalties of any kind, including WITHOUT LIMITATION any tax liabilities or
penalties; lost profits or goodwill; consequential damages; damages ensuing from
loss of credit; damages ensuing from breach of the covenant or

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duty of good faith and fair dealing; damages ensuing from breach of any
federal, state or foreign antitrust law; damages ensuing from breaches of
confidential and fiduciary duties; damages ensuing from breach of contract;
damages ensuing from actual or constructive fraud; and prejudgment and post
judgment interest, costs and attorney's fees.

     1.3 "ANTI-IgE ANTIBODY(IES)" shall mean an antibody directed against the
immunoglobulin IgE as an antigen, fragments or conjugates of such antibodies,
and other constructs comprising antibodies which are derived from or contain any
of the above-specified components. ANTI-IgE ANTIBODY PRODUCT(S) means any
pharmaceutical formulation, product, method or system which contains an Anti-IgE
Antibody.

     1.4 "CONSIDERATION" shall mean the value or benefit to each of the Parties,
respectively, of-the licenses, royalties, payments and agreements contained
herein, in the Genentech Agreement and in the Outline of Terms and all other
mutual promises, covenants, agreements, releases, and representations set forth
in this Agreement.

     1.5 "INCIDENT" shall mean the negotiations, beginning in 1989 and ending in
December 1993, between Tanox and Genentech with regard to a potential
collaboration in the identification and development of anti-immunoglobulin E
("anti-IgE") monoclonal antibodies and anti-IgE therapy; the agreements entered
into pursuant to those negotiations, as well as any supplements or amendments to
those agreements ("the Collaboration Agreements"), including but not limited to
a Confidentiality Agreement dated (by Tanox) March 29, 1989 and a Biological
Material Transfer and Confidentiality Agreement dated (by Tanox) July 27, 1989;
negotiations concerning the construction and meaning of the Collaboration
Agreements; the performance of the Collaboration Agreements; any interference in
the performance of the Collaboration Agreements; any statements regarding the
performance of the Collaboration Agreements; any acts or events prior to or
subsequent to the negotiation or execution of the Collaboration Agreements that
form the basis of any cause of action alleged in or that could have been alleged
in the Lawsuit; any other matters arising out of the Collaboration Agreements;
the use by

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Genentech of information provided by Tanox to Genentech pursuant to the
Collaboration Agreements or otherwise during such negotiations; the solicitation
and obtaining of licensing rights heretofore from third parties in the area of
monoclonal antibody research and technology; the research, development and
commercialization of anti-IgE monoclonal antibodies and/or anti-IgE therapy
heretofore; any infringement heretofore of patents rights held at any time by
the Parties to this Agreement regarding recombinant immunoglobulin preparations
and monoclonal antibody identification and development; and any statements or
representations heretofore made by either Party regarding research, development
and commercialization of anti-IgE monoclonal antibodies and/or anti-igE therapy.

     1.6 "OUTLINE OF TERMS" shall mean the agreement between Tanox, Genentech
and Ciba which sets forth the basic terms agreed by such parties with respect to
the joint development and commercialization of Anti-IgE Antibodies, with the
participation of Roche to the extent it exercises its options thereunder, and
which is intended to be followed and superseded by a definitive agreement(s) as
contemplated by Section 8.2 of the Outline of Terms [which agreement(s) is
referred to as the ("Definitive Agreement")].

     1.7 "PARTY" shall mean, when used in the singular, either Tanox or the
Roche Entities, as appropriate, and "Parties" shall mean Tanox and the Roche
Entities.

     1.8 "PERSON" OR "PERSONS" shall include any natural person, as well as any
entity such as a corporation, partnership, proprietorship, or business
association.

     1.9 "ROCHE ENTITIES" shall mean, jointly and severally, each and all of the
following companies and their Affiliates (excluding Genentech): F. Hoffmann-La
Roche Ltd. Hoffmann-LaRoche, Inc., Roche Holding Ltd., and Roche Holdings, Inc.

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     2.0 MUTUAL RELEASE, INDEMNIFICATION AND SETTLEMENT AGREEMENT

     2.1 DISMISSAL OF LAWSUIT. Tanox and the Roche Entities agree as follows:

          (i)  Tanox will file a motion to dismiss its claims in the Lawsuit
               against the Roche Entities with prejudice; and

          (ii) each of the parties shall bear its own costs of court incurred.

     2.2 RELEASE OF ROCHE ENTITIES. For the Consideration, including the
agreements set forth in this Section 2, Tanox hereby RELEASES, ACQUITS, and
FOREVER DISCHARGES the Roche Entities and (I) all of their present or former
agents, employees, officers, directors, shareholders, partners, joint venturers,
and attorneys; (ii) all companies partnerships, joint ventures, or firms
affiliated with or subsidiary to, the Roche Entities; (iii) their predecessors,
successors, and assigns; (iv) all other persons, partners, joint venturers,
firms, partnerships, joint ventures, and corporations for whose conduct the
Roche Entities may be liable; and (v) all of their insurers from All Claims that
have accrued or that may ever accrue to Tanox or any person or persons now or
hereafter claiming by, through, or under Tanox.

     2.3 RELEASE OF TANOX. For the Consideration including the agreements set
forth in this Section 2, the Roche Entities RELEASE, ACQUIT, and FOREVER
DISCHARGE Tanox and (i) all of its present or former agents, employees,
officers, directors, shareholders, partners, joint venturers, and attorneys;
(ii) all companies, partnerships, joint ventures, or firms affiliated with or
subsidiary to Tanox; (iii) its predecessors, successors, and assigns; (iv) all
other persons, partners, joint venturers, firms, partnerships, joint ventures,
and corporations for whose conduct Tanox may be liable; and (v) all of its
insurers from All Claims that have accrued or that may ever accrue to the Roche
Entities or any person or persons now or hereafter claiming by, through, or
under the Roche Entities.

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     2.4 NO ADMISSION OF LIABILITY. Agreement to the Consideration is not an
admission of liability and may not be so construed. The Roche Entities
vigorously deny the position taken by Tanox in the Lawsuit and Tanox
acknowledges the highly disputed nature of its claims in the Lawsuit. Tanox
vigorously denies the position taken by the Roche Entities in the Lawsuit, and
the Roche Entities acknowledges the highly disputed nature of their defenses in
the Lawsuit. Each party acknowledges that this Agreement is made as a
compromise to avoid further expense and to terminate for all time the
controversies which were asserted, could have been asserted, or were sought to
be asserted in the Lawsuit.

     2.5 INDEMNIFICATION BY TANOX. Tanox agrees to INDEMNIFY and to DEFEND and
to HOLD HARMLESS the Roche Entities and (i) all of their present or former
agents, employees, officers, directors, shareholders, partners, joint venturers,
and attorneys; (ii) all companies, partnerships, joint ventures, or firms
affiliated with or subsidiary to, the Roche Entities; (iii) their predecessors,
successors, and assigns; (iv) all other persons, partners, joint venturers,
firms, partnerships, joint ventures, and corporations for whose conduct the
Roche Entities may be liable; and (v) all of their insurers from All Claims,
together with all costs, expenses, and legal fees, that may be asserted against
the Roche Entities by any person, entity, firm, or corporation claiming by,
through, or under Tanox, that arise out of the Incident and/or the Lawsuit.

     2.6 INDEMNIFICATION BY THE ROCHE ENTITIES. The Roche Entities agree to
INDEMNIFY and to DEFEND and to HOLD HARMLESS Tanox and (i) all of its present or
former agents, employee, officers, directors, shareholders, partners, joint
venturers, and attorneys; (ii) all companies, partnerships, joint ventures, or
firms affiliated with or subsidiary to Tanox; (iii) its predecessors,
successors, and assigns; (iv) all other persons, partners, joint venturers,
firms, partnerships joint ventures, and corporations for whose conduct Tanox may
be liable; and (v) all of its insurers from All Claims, together with all costs,
expenses, and legal fees, that may be asserted against Tanox by any person,
entity,

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firm, or corporation claiming by, through, or under the Roche Entities that
arise out of the Incident and/or the Lawsuit

     2.7 NO OPPOSITION. The Roche Entities represent and warrant that they have
not filed any opposition in the European Patent Office to Tanox's patent No.
EP-B-407392 relating to Anti-IgE Antibodies or taken any other actions to
re oppose, request the examination of, or otherwise challenge the validity or
enforceability, directly or indirectly, of any Tanox patents covering Anti-IgE
Antibodies.

     2.8 ANTI-IgE ANTIBODY PATENTS. The Roche Entities represent and warrant to
Tanox that they do not have knowledge of any patents owned in whole or in part
and/or controlled by them which would prevent Tanox from being able to make, use
and sell Anti-IgE Antibodies. If Roche has exercised its option set forth in the
Outline of Terms (or Definitive Agreement) in a particular country or has
received a sublicense or assumed Genentech's rights and obligations under the
Genentech Agreement, then to the extent the Roche Entities should ever own in
whole or in part and/or control any such patents the Roche Entities agree to
grant to Tanox under all such patents a royalty-free, non-exclusive,
sublicensable license to make, have made, use, sell, have sold and import
Anti-IgE Antibodies for the treatment, prophylaxis or diagnosis of any disease
or condition in humans and animals in the country or territory with respect to
which Roche has exercised its options under the Outline of Terms (or Definitive
Agreement) or has received a sublicense or assumed Genentech's rights and
obligations under the Genentech Agreement.

     2.9 EXEMPTION FROM PROTECTIVE ORDER. Notwithstanding the terms of the
protective order agreed in connection with the Lawsuit, the Parties agree that
the employees, experts and consultants of a Party having access to information
during the course of the Lawsuit will not be prohibited from participating in
on-going development and commercialization activities associated with the
Anti-IgE Antibody projects of such Party

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and/or development and commercialization activities of the Parties pursuant to
the Outline of Terms or Definitive Agreement.

     2.10 REPRESENTATIONS OF TANOX. Tanox makes the representations and
warranties set forth in Exhibit 1 to the Roche Entities.

     2.11 REPRESENTATIONS OF ROCHE. The Roche Entities make the representations
and warranties set forth in Exhibit 2 to Tanox.

     3.0 BENEFICIARY OF AGREEMENTS. On the Effective Date, Tanox, Ciba and
Genentech have executed the Outline of Terms. The Outline of Terms and
Definitive Agreement, together with that certain Development and Licensing
Agreement dated May 11, 1990, between Tanox and Ciba (the "D & L Agreement"),
shall among them govern the development and commercialization of one or more
anti-IgE Products (as such term is used in the Outline of Terms) which have been
identified and synthesized by Tanox, Ciba, or Genentech before July 1, 1996.
Additionally, on the Effective Date, Tanox and Genentech have executed the
Genentech Agreement which, among other things, grants certain additional license
rights to such parties which may be effective in addition to or in lieu of
rights under the Outline of Terms and Definitive Agreement. The Parties
acknowledge that under such agreements, including the Genentech Agreement, and
subject to certain agreements between Roche and Genentech, Roche will have
certain rights to participate in the development and commercialization of
Anti-IgE Antibody products.

     4.0 LICENSES FOR ANTI-IgE ANTIBODY PATENTS. If (i) Roche has exercised its
options set forth in the Outline of Terms (or Definitive Agreement) in a country
or has received a sublicense or assumed Genentech's rights and obligations under
the Genentech Agreement in a particular country and (ii) the Roche Entities
should ever desire to obtain exclusive access to a patent owned and/or
controlled by a third party which covers Anti-IgE Antibodies in such country in
any manner, then the Roche Entities will acquire rights to

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such patent in a manner which reserves for Tanox the opportunity to obtain
co-exclusive rights to such patent for Anti-IgE Antibodies in such country.

5.0 ADDITIONAL LICENSES. Subject to all of the existing licenses and existing
agreements that restrict the ability of 1he Roche Entities to grant licenses and
subject to the additional restrictions set forth below, "the Roche Entities
agree to grant to Tanox, a worldwide, nonexclusive, nonsublicenseable (except to
Affiliates, but only in conjunction with the license of a specific product)
license to make, have made, use, sell, have sold and import products for * under
patents owned by the Roche Entities now or in the future, and which the Roche
Entities have made or agree to make generally available on a non-exclusive
basis, except that such products shall not include those (i) that are the
subject of a prior exclusive license by the Roche Entities to a third party;
(ii) that are the subject of an active research or development program of the
Roche Entities; or (iii) that compete with, or will compete with, a then current
product of the Roche Entities or a product in an active research and/or
development program of the Roche Entities; provided, however, that if any such
patents desired by Tanox shall be subject to exclusive rights to a third party
which would prevent the license desired by Tanox , the Roche Entities agree that
Tanox shall have the right to negotiate a sublicense, if possible, from any such
third party on terms agreed between Tanox and such third party. The Roche
Entities also agree to negotiate in good faith with Tanox on the availability of
such a license for Tanox products under other patents owned by the Roche
Entities. The Parties agree to negotiate in good faith the royalty rate and
terms on which any license will be granted. Subject to the limitations set forth
above, Tanox may exercise its right to such a license, without threat of suit or
penalty from the Roche Entities, with respect to a product at any time prior to
the date of the first commercial sale of such product to an independent third
party following regulatory approval to sell such product. If Tanox should ever
have under development a product which could be subject to the restrictions on
receiving a license set forth herein, then the Roche Entities or Tanox should
notify the other of such possibility prior to taking any other actions. If the
Parties are unable to resolve the issues prior to the time the

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activities of Tanox would constitute an infringement of a patent owned and/or
controlled by the Roche Entities pursuant to applicable laws, which resolution
could include a collaboration or cross-licensing opportunity or Tanox's express
agreement not to manufacture, develop or market in such country in which a valid
claim of any patent of the Roche Entities covering such product may exist, then
the Roche Entities shall be entitled to pursue such legal or other actions as
they may determine, in their sole discretion, to be appropriate under the
circumstances.

     6.0 CONFIDENTIALITY. In connection with preparation and during the term of
this Agreement, one Party may disclose to the other or receive written
information from the other relating to the subject matter of this Agreement
which information, if so identified in writing either pursuant to this Section
6.0 or otherwise upon disclosure, shall be considered to be the disclosing
Party's Confidential Information. Each Party agrees that it will take the same
steps to protect the confidentiality of the other Party's Confidential
Information as it takes to protect its own proprietary and Confidential
Information. Each Party shall protect and keep confidential and shall not use,
publish or otherwise disclose to any third party, except as permitted by this
Agreement or with the other Party's written consent, the other Party's
Confidential Information for a period of ten (10) years from the date of
disclosure, respectively, of any such Confidential Information. For the purposes
of this Agreement, Confidential Information shall not include such information
that (i) was lawfully known to the receiving Party at the time of disclosure;
(ii) was generally available to the public or was otherwise part of the public
domain at the time of disclosure or became generally available to the public or
otherwise part of the public domain after disclosure other than through any act
or omission of the receiving Party in breach of this Agreement; (iii) became
known to the receiving Party after disclosure from a source that had a lawful
right to disclose such information to others; or (iv) is required to be
disclosed by the receiving Party to comply with applicable laws, to defend or
prosecute litigation or to comply with governmental regulations, provided that
the receiving Party provides prior written notice of such disclosure to the
other Party and takes reasonable and lawful actions to avoid and/or minimize the
degree of such disclosure.

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Notwithstanding the above, the Parties may disclose Confidential information to
their legal representatives, to Affiliates and their legal representatives, and
to consultants (to the extent such disclosure is intended to further the
purposes contemplated under this Agreement) and provided such legal
representatives, Affiliates and consultants have agreed in writing to be bound
to protect the confidentiality of such information in a manner at least as
restrictive as that generally set forth herein.

     7.0 TERM; DEFAULT; SURVIVAL.

     7.1 TERM. Except as otherwise set forth herein, this Agreement shall
terminate at such time following the first commercial sale of an Anti-IgE
Antibody product as royalties are no longer owed to Tanox by or as a result of
sales for the benefit of the Roche Entities or any Affiliate, excluding
Genentech or sales by or for the benefit of Genentech. Notwithstanding the
foregoing, this Agreement shall terminate upon the prior occurrence of the
expiration unexercised of any option rights which the Roche Entities may have
under the Outline of Terms or Definitive Agreement and the expiration
unexercised of any rights which the Roche Entities may have to receive a
sublicense or to assume Genentech's rights and obligations under the Genentech
Agreement.

     7.2 DEFAULT. Failure by either Party (the "defaulting Party") to comply
with any of the material obligations contained in this Agreement shall entitle
the other Party (the "nondefaulting Party") to give the defaulting Party notice
specifying the nature of the default and requiring it to cure such default. If
such default is not cured within the sixty (60) day period after the receipt of
such notice, the nondefaulting Party shall be entitled, except as otherwise
specifically provided in this Agreement and without prejudice to any of its
other rights conferred on it by this Agreement, to terminate all or part of this
Agreement.

     7.3 SURVIVAL OF PROVISIONS. The obligations of the Parties under Sections
2.0 and 6.0 shall survive any termination of this Agreement, except to the
extent limited therein.

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     8.0 GENERAL PROVISIONS.

     8.1 ADEQUACY OF CONSIDERATION. By signing this Agreement, each Party to
this Agreement acknowledges the receipt by such Party and the sufficiency to
such party of the Consideration.

     8.2 NOTICES. All notices which may be required pursuant to this Agreement
(i) shal1 be in writing, (ii) shal1 be addressed, in the case of the Roche
Entities (except as otherwise specified herein), to Corporate Law, F.
Hoffmann-La Roche Ltd. at the address set forth at the beginning of this
Agreement and to Corporate Secretary, Hoffmann-La Roche, Inc., 340 Kingsland St,
Nutley, N.J. 07110, and in the case of Tanox to the President at the address set
forth at the beginning of this Agreement, (or to such other person or address as
either Party may so designate from time to time), (iii) shall be mailed,
postage-prepaid, by registered mail or certified mail, return receipt
requested, or transmitted by courier for hand delivery or sent by express
courier service, and (iv) shall be deemed to have been given on the date of
receipt if sent by mail or on the date of delivery if transmitted by courier or
express courier service.

     8.3 ENTIRE AGREEMENT. This Agreement is the entire agreement between the
Parties regarding the subject matter hereof, and there are no prior written or
oral promises or representations not incorporated herein. No amendment or
modification of the terms of this Agreement shall be binding on either Party
unless reduced to writing and signed by an authorized officer of the Party to be
bound.

     8.4 BINDING EFFECT. This Agreement shall be binding upon and inure to the
benefit of the Parties hereto, Affiliates, and their respective successors and
permitted assigns. This Agreement shall not be assignable by either Party
without the other's prior written consent, except that this Agreement may be
assigned in whole or in part to an Affiliate or a successor to all or
substantially all of a Party's business by merger, sale of assets, sale of stock
or otherwise.

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     8.5 WAIVER. The waiver by a Party hereto of any breach of or default under
any of the provisions of this Agreement or the failure of a Party to enforce any
of the provisions of this Agreement or to exercise any right thereunder shall
not be construed as a waiver of any other breach or default or as a waiver of
any such rights or provisions hereunder.

     8.6 SEVERABILITY. If any part of this Agreement shall be invalid or
unenforceab1e under applicable law, such part shall be ineffective only to the
extent of such invalidity or unenforceability, without in any way affecting the
remaining parts of this Agreement. In addition, the part that is ineffective
shall be reformed in such a manner as to as nearly approximate the intent of
the Parties as possible.

     8.7 PUBLICITY. Except for disclosure that settlement of the Lawsuit has
occurred, neither the Roche Entities nor Tanox shall issue any public statement
concerning this Agreement without the other Party's reasonable prior written
consent; provided, however, that either Party may disclose the transaction or
the terms hereof or thereof from time to time without the other Party's consent
(i) if such consent has been requested and not received and such information is
set forth in disclosures to investors and prospective investors in the
securities of a Party pursuant to laws, rules and regulations covering any such
transactions or such Party has a written opinion from outside counsel that it is
otherwise required by law to disclose the transaction or the terms thereof, or
(ii) to the extent that similar disclosure has been previously approved by the
Parties pursuant to this Section 8.7. The foregoing notwithstanding, Tanox may
disclose the terms of this Agreement to its shareholders, investment bankers and
other financial consultants, and prospective investors in Tanox, provided that
the recipients of such information agree to be bound to protect the
confidentiality of that information for a period of at least three (3) years and
in a manner otherwise at least as restrictive as that generally set forth in
Section 6.0 above.

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     8.8 NO PARTNERSHIP. Nothing in this Agreement is intended or shall be
deemed to constitute a partnership, agency, employer-employee or joint venture
relationship between the Parties. No party shall incur any debts or make any
commitments for the other.

     8.9 SURVIVAL OF REPRESENTATIONS. All agreements and representations made by
the parties in this Agreement shall survive the execution and delivery of this
Agreement, the receipt of the Consideration, and the execution and delivery of
any other instrument, or the taking of any other actions required or provided
for in this Agreement.

     8.10 DISPUTE RESOLUTION. The laws of the State of New York shall govern the
construction and interpretation of this Agreement, and any action to enforce
this agreement or resolve any disputes shall be by binding arbitration conducted
pursuant to the then current American Arbitration Association ("AAA") Commercial
Arbitration rules in New York City, New York, such arbitration to be conducted
by a panel of three arbitrators selected from a pool of arbitrators to be
presented to the Parties by AAA.

     8.11 AGREEMENT TO PERFORM NECESSARY ACTS. Each Party agrees to perform any
further acts and execute and deliver any and all further documents, agreements,
and/or instruments which may be reasonably necessary or desirable to carry out
or effect the provisions of this Agreement.

     8.12 COUNTERPARTS. This Agreement may be executed in counterparts, and each
such counterpart shall be deemed an original for all purposes.

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F. Hoffman-La Roche Ltd                         Roche Holding Ltd
By:   ILLEGIBLE                                 By:   ILLEGIBLE
Title: Authorized Signatory                     Title: Director

By:   ILLEGIBLE                                 By:   ILLEGIBLE
Title: Director                                 Title: Director

Hoffman-La Roche Inc.                           Roche Holdings, Inc
By:   ILLEGIBLE                                 By:   ILLEGIBLE
Title: V.P.                                     Title: Secretary

Tanox Biosystems, Inc.
By: David Anderson
Title: Executive Vice President

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                                   EXHIBIT 1
                    Representations and Warranties by Tanox

(a)  Before executing this Agreement, Tanox became fu11y informed of the terms
     contents, conditions, and effect of this Agreement.

(b)  Tanox is a corporation duly organized, existing, and in good standing under
     the laws of the State of Texas.

(c)  Tanox possesses all requisite power and authority to enter into and perform
     this Agreement and to carry out the transactions contemplated herein.

(d)  Tanox has taken a1l necessary corporate and legal addition to authorize the
     execution, delivery, and performance of this Agreement.

(e)  No consent or authorization of, filing with or any other act by or in
     respect of any other person (including any shareholder or creditor) or
     court is required in connection with the settlement of All Claims as set
     forth in this Agreement or with the execution, delivery, or performance by
     Tanox or the validity or enforceability as to Tanox of this Agreement.

(f)  This Agreement has been duly executed and delivered by Tanox and
     constitutes a legal, valid and binding obligation of Tanox enforceable
     against Tanox in accordance with its terms.

(g)  No promise or representation of any kind has been made to Tanox or by
     anyone acting for Tanox, except as is expressly stated in this Agreement.

(h)  Except for certain claims or portions thereof which may have been assigned
     to its attorneys, Tanox is the lawful owner of All Claims asserted by Tanox
     in the Lawsuit and has not assigned, pledged, or in any other manner sold
     or transferred any right, title, interest, or claim that arises out of or
     is the subject of the Incident and/or the Lawsuit.

(i)  In entering this Agreement, Tanox has had the benefit of the advice of
     lawyers of its own choosing; and Tanox enters this Agreement freely, by
     Tanox's own choice and judgment, and without duress or other influence.

(j)  Tanox understands that this Agreement is a full, final, and complete
     release of the other Party to this Agreement and that the Consideration
     includes the ONLY benefits Tanox shall ever receive from such Party as a
     result of the Incident and the Lawsuit.

(k)  Tanox recognizes that the recitations contained in this Agreement are
     contractual and not a mere recital.
<PAGE>
                                   EXHIBIT 2
              Representations and Warranties by The Roche Entities

(a)  Before executing this Agreement, the Roche Entities became fully informed
     of the terms, contents, conditions, and effect of this Agreement.

(b)  The Roche Entities are corporations duly organized, existing, and in good
     standing under the laws of the respective states, cantons, and countries
     under which they have been organized.

(c)  The Roche Entities possess all requisite power and authority to enter into
     and perform this Agreement and to carry out the transactions contemplated
     herein.

(d)  The Roche Entities have taken all necessary corporate and legal action to
     authorize the execution, delivery, and performance of this Agreement.

(e)  No consent or authorization of, filing with or any other act by or in
     respect of any other person (including any shareholder or creditor) or
     court is required in connection with the settlement of All Claims as set
     forth in this Agreement or with the execution, delivery, or performance by
     the Roche Entities or the validity or enforceability as to the Roche
     Entities of this Agreement.

(f)  This Agreement has been duly executed and delivered by the Roche Entities
     and constitutes a legal, valid and binding obligation of the Roche Entities
     enforceable against the Roche Entities in accordance with its terms.

(g)  No promise or representation of any kind has been made to the Roche
     Entities or by anyone acting for the Roche Entities, except as is expressly
     stated in this Agreement.

(h)  In entering this Agreement, the Roche Entities have had the benefit of the
     advice of lawyers of its own choosing; and the Roche Entities enter this
     Agreement freely, by their own choice and judgment, and without duress or
     other influence.

(i)  The Roche Entities understand that this Agreement is a full, final, and
     complete release of the other Party to this Agreement and that the
     Consideration includes the ONLY benefits the Roche Entities shall ever
     receive from such Party as a result of the Incident and the Lawsuit.

(j)  The Roche Entities recognize that the recitations contained in this
     Agreement are contractual and not a mere recital.EXHIBIT 10.22

                 G-CSF RECEPTOR NON-EXCLUSIVE LICENSE AGREEMENT

     THIS G-CSF RECEPTOR NON-EXCLUSIVE LICENSE AGREEMENT is entered into and
made effective this 11th day of January, 2000, by and between IMMUNEX
CORPORATION, a corporation of the state of Washington, having its principle
place of business as 51 University Street, Seattle, Washington 98101
(hereinafter referred to as "Immunex"), and TANOX, INC., a corporation of the
State of Texas, and having a place of business at 10301 Stella Link, Houston,
Texas 77025.

                                   BACKGROUND

          WHEREAS, Immunex is a biopharmaceutical company engaged in the
     research, development, marketing and sale of therapeutics for treating
     human disease. Immunex owns proprietary and confidential information and
     intellectual property relating to G-CSF Receptor ("G-CSF Receptor
     Technology"). Immunex is the sole owner of and has full right to the
     Licensed Patent Rights (as defined below):

          WHEREAS, Licensee (as defined herein) wishes to obtain *

          WHEREAS, the use of G-CSF Receptor Technology is valuable to Licensee
     in the discovery, research and development of Developed Products;
     therefore, Licensee is willing to compensate Immunex for such use by paying
     Immunex a royalty calculated as a percentage of Net Sales (as defined
     below) of Developed Products, in addition to license execution and
     maintenance fees and fees payable upon the achievement of certain
     milestones relating to Developed Products.

                                   AGREEMENT

     NOW THEREFORE, in consideration of the premises and mutual covenants and
agreements contained herein, and for good and other valuable consideration, the
receipt and sufficiency of which is hereby acknowledged, Immunex and Licensee,
intending to be legally bound hereby, do hereby agree as follows:
<PAGE>
1.  DEFINITIONS

     1.1  "AFFILIATE" shall mean any corporation, company, partnership, joint
venture, firm or other entity which directly or indirectly owns, is owned by or
is under common ownership with a Party (as defined below) where "owns" or
"ownership" means possession of at least fifty percent (50%) of the equity (or
such lesser percentage which is the maximum allowed to be owned by a foreign
corporation in a particular jurisdiction or such lesser percentage provided the
operational control is held by the Party) having the power to vote on or direct
the affairs of the entity and any person, firm, partnership, corporation or
other entity actually controlled by, controlling or under common control with a
Party.

     1.2  "CALENDAR QUARTER" shall mean each three (3) month period commencing
January 1, April 1, July 1 and October 1 of each year during the Term (as
defined in Section 5.1) of this Agreement.

     1.3  "DEVELOPED PRODUCT" *

     1.4  "EFFECTIVE DATE" shall mean the date this Agreement is effective,
which shall be the date first indicated above.

     1.5  "FIELD" *

     1.6  "FORCE MAJEURE" shall mean any act of God or the public enemy, any
accident, explosion, fire, storm, earthquake, flood, drought, peril of the sea,
riot, embargo, war or foreign, federal, state or municipal order issued by a
court or other authorized official, seizure, requisition or allocation, any
failure or delay of transportation, shortage of or inability to obtain supplies,
equipment, fuel or labor or any other circumstance or event beyond the
reasonable control and without the fault or negligence of the Party relying upon
such circumstance or event.

     1.7  "LICENSED PATENT RIGHTS" *

                                       2
<PAGE>
     1.8  "LICENSEE" shall mean Tanox, Inc. and/or its Affiliates, as
applicable.

     1.9  "NET SALES" *

     1.10  "PARTY" shall mean either Immunex or Licensee, as applicable. The
term "PARTIES" shall mean both Immunex and Licensee.

     1.11  "PHASE III" shall mean, with respect to a Developed Product, the
period of product development commencing with enrollment of the first patient in
a placebo-controlled or otherwise appropriately controlled clinical trial that
is intended to demonstrate efficacy for registration of such Developed Product
and ending upon filing of an NDA, BLA, or foreign equivalent seeking Regulatory
Approval, where the clinical trial is sponsored by a Party or its sublicensees.

     1.12  "REGULATORY AGENCY" shall mean the United States Food and Drug
Administration ("FDA") or any successor agency vested with administrative and
regulatory authority to approve testing and marketing of human pharmaceutical or
biological therapeutic products in the United States and/or any regulatory body
with similar regulatory authority in any other part of the world where any Party
to

                                       3
<PAGE>
this Agreement elects to file an NDA, BLA or foreign equivalent seeking
Regulatory Approval.

     1.13  "REGULATORY APPROVAL" shall mean the receipt by a Party of the
authorization by an appropriate Regulatory Agency to market and sell Developed
Product in a country, including to the extent required, any governmental pricing
approval for such Developed Product in such country.

     1.14  "THIRD PARTY" shall mean any individual, partnership, corporation,
firm, association, unincorporated organization, joint venture, trust or other
entity that is neither a Party nor an Affiliate.

     1.15 *

2.  LICENSE GRANT

     2.1 Immunex hereby grants a non-exclusive worldwide license under the
Licensed Patent Rights, for manufacture and use of G-CSF Receptor in the Field
by Licensee. This license includes the limited right to sublicense the Licensed
Patent Rights to a Third Party to manufacture Developed Products on behalf of
Licensee. The license grant herein does not include the right to sublicense the
Licensed Patent Rights to sell or offer for sale G-CSF Receptor. In any event,
such license grant shall permit the manufacture, use, sale, offer for sale and
importation of Developed Products by Licensee throughout the world. Nothing
contained in this Agreement shall restrict or prohibit Licensee's right to grant
to a Third Party such right to sell or offer for sale a Developed Product.

3.  PAYMENTS AND REPORTS

     3.1  LICENSE EXECUTION FEE.  * after the Effective Date, Licensee shall pay
to Immunex *

     3.2  LICENSE MAINTENANCE FEE.  In consideration of maintaining the license
granted to it pursuant to this Agreement. Licensee shall pay to Immunex *

                                       4
<PAGE>
     3.3  MILESTONE FEES.  For each Developed Product, Licensee, or its
Affiliate, shall pay Immunex the following fees upon occurrence of the following
milestone events:

                                       *

     3.4 ROYALTIES. Licensee shall pay Immunex a royalty of * in respect of the
annual Net Sales of all Developed Products * following the last day of each
Calendar Quarter following * Such royalties shall not be returnable in any
event. *

     3.5  ROYALTY REPORTS AND TERM. *

                                       5
<PAGE>
     3.6  CURRENCY CONVERSION.  Royalty and milestone payments by Licensee shall
be made to Immunex in U.S. Dollars. For converting any royalty payments on Net
Sales made in a currency other than U.S. Dollars, Net Sales shall first be
determined in the currency of the country in which they are earned and shall be
converted each Calendar Quarter into an account in U.S. Dollars at the average
of the bid and ask prices reported in the WALL STREET JOURNAL as of the close of
the last business day of such Calendar Quarter in which such royalty is due. If
the last day of such Calendar Quarter is not a business day, then the closest
preceding business day shall be used for such calculation. All such converted
Net Sales shall be consolidated with U.S. Net Sales for each Calendar Quarter
and the applicable royalty payable determined therefrom. If by law, regulation
or fiscal policy of a particular country, remittance of royalties in U.S.
Dollars is restricted or forbidden, notice thereof will be promptly given to
Immunex, and payment of the royalty shall be made by the deposit thereof in
local currency to the credit of Immunex in a recognized banking institution
designated by Licensee. When in any country a law or regulation prohibits both
the transmittal and deposit of royalties on sales in such a country, royalty
payments shall be suspended for as long as such prohibition is in effect and as
soon as such prohibition ceases to be in effect, all royalties that Licensee
would have been under obligation to transmit or deposit but for the prohibition,
shall forthwith be deposited or transmitted promptly to the extent allowable.
The actual currency conversion calculations by Licensee for any country for a
particular Calendar Quarter shall be included in the royalty report provided to
Immunex for such Calendar Quarter under Section 3.5 above.

     3.7  WITHHOLDING TAXES.  All royalty amounts required to be paid to Immunex
pursuant to this Agreement may be paid with deduction for withholding for or on
account of any taxes (other than taxes imposed on or measured by net income) or
similar governmental charge imposed by a jurisdiction other than the United
States ("Withholding Taxes"). At Immunex's request, Licensee shall provide
Immunex a certificate evidencing payment of any Withholding Taxes hereunder and
shall reasonably assist Immunex to obtain the benefit of any applicable tax
treaty, at Immunex's sole cost for providing such reasonable assistance.

4.  RECORDS

     4.1  LICENSEE'S RECORDS.  Licensee shall keep and maintain, and shall
require each Affiliate to keep and maintain, in accordance with generally
acceptable accounting principles, adequate records in sufficient detail to
enable the payments due under Sections 3.3 and 3.4 to be determined. Nothing
herein shall require Licensee or any Affiliate to retain such records longer
than three (3) years after the payments to which they relate are paid.

                                       6
<PAGE>
     4.2  AUDITS.  At Immunex's request and expense. Licensee shall permit such
records under Section 4.1 to be inspected at any time during regular business
hours, but not more than once in any calendar year, by an independent public
accountant, appointed by Immunex for this purpose and reasonably acceptable to
Licensee, who shall report to Immunex only the amount of the royalties due
hereunder. If such independent public accountant reasonably determines that such
royalties, after adjustments in accordance with generally acceptable accounting
principles, have been understated by Licensee, for any calendar year. Licensee
shall pay the amount due for all royalties not properly reported. If it is
determined that Licensee has understated such royalties by an amount equal to or
greater than * Licensee shall pay all reasonable fees and costs
incurred by such independent public accountant in the course of making such
determination.

5.  TERM AND TERMINATION

     5.1 TERM This Agreement shall be effective as of the Effective Date and
shall continue in full force and effect until the later of the expiration,
lapse, revocation, unenforceability or invalidation of the last of the Licensed
Patent Rights, on a country-by country basis, unless earlier terminated earlier
as provided in this Agreement (the "Term"). Upon expiration of this Agreement,
all rights licensed hereunder shall become irrevocable upon payment of any
amounts due that have accrued hereunder prior to expiration. Expiration of this
Agreement shall not preclude Licensee from continuing to make, have made, use,
sell, offer for sale or import Developed Product worldwide without further
royalty payments or other remuneration to Immunex with respect to Licensed
Patent Rights.

     5.2 IMMUNEX'S RIGHT TO TERMINATE. Immunex shall have the right to terminate
this Agreement, including the licenses granted herein, in the event that any
material term or condition of this Agreement is breached by Licensee or an
Affiliate, and such breach is unremedied for a period of sixty (60) days after
Licensee's receipt of Immunex's written notice thereof. If such breach is
corrected within the sixty (60) day period, this Agreement and the rights
granted shall continue in force.

     5.3  LICENSEE'S RIGHT TO TERMINATE.  In the event that Licensee determines
that it will no longer carry out or continue drug discovery, research,
development of manufacturing using Licensed Patent Rights or continue
development or sale of Developed Products. Licensee shall notify Immunex in
writing, and this Agreement shall be terminated as of the date Immunex receives
such notice from Licensee.

     5.4  CONTINUING OBLIGATIONS.  Termination of this Agreement shall not
relieve License of any obligations to make payment of any sum due prior to
termination

                                       7
<PAGE>
under Article 3, or to keep records and provide written reports with
respect thereto, and to permit inspection thereof in accordance with Section 4.2

6.  WARRANTIES

     6.1  WARRANTIES AND REPRESENTATIONS OF IMMUNEX.  Immunex warrants to
Licensee that:

          6.1.1  Immunex is a corporation duly organized, validly existing and
     in good standing under the laws of the State of Washington and has all
     necessary corporate power to enter into and perform its obligations under
     this Agreement.

          6.1.2  the execution, delivery and performance of this Agreement by
     Immunex have been duly authorized and approved by all necessary corporate
     action, and this Agreement is binding, upon and enforceable against Immunex
     in accordance with its terms (subject to bankruptcy and similar laws
     affecting the rights of creditors generally);

          6.1.3 as of the Effective Date, Immunex is the owner of the Licensed
     Patent Rights and has the right to grant Licensee the licenses granted
     hereunder; and

          6.1.4 Immunex is not aware of any special or unusual hazards that
     would would proscribe Licensee's right to develop and sell Developed
     Products.

     6.2  WARRANTIES AND REPRESENTATION OF LICENSEE.  Licensee represents and
warrants to Immunex that:

          6.2.1  Licensee is a corporation duly organized, validly existing, and
     in good standing, under the laws of the State of Texas and has all
     necessary corporate power to enter into and perform their obligations under
     this Agreement;

          6.2.2  the execution, delivery and performance of this Agreement by
     Licensee, have been duly authorized and approved by all necessary corporate
     action, and this Agreement is binding, upon and enforceable against
     Licensee, in accordance with its terms (subject to bankruptcy and similar
     laws affecting rights of creditors generally); and

          6.2.3  during the Term of this Agreement, Licensee shall not practice
     the Licensed Patent Rights other than as specifically authorized in this
     Agreement.

     6.3  LIMITATION OF LIABILITY.  Immunex has no control over the manner in
which the Licensee intends to use the Developed Products or Licensed Patent
Rights. Immunex shall not be liable to Licensee for any losses, damages, costs
or

                                       8
<PAGE>
expenses of any nature incurred or suffered by Licensee or by a Third Party,
arising, out of any dispute or other claims or proceedings made by or brought
against Licensee, (including, without limitation, product liability claims and
claims by a Third Party alleging infringement of its intellectual property
rights by the use or sale of any Developed Product), nor shall Immunex be
responsible in any way for dealing with any such dispute, claim or proceedings,
except to the extent that any such dispute, claim or proceeding arises from (a)
a breach by Immunex of any warranty set forth in Section 6.1 hereof, or (b) the
gross negligence or willful misconduct by Immunex, its employees, agents or
directors. EXCEPT AS SET FORTH IN SECTION 6.1 OR 6.2 HEREOF, NEITHER PARTY MAKES
ANY PRODUCT WARRANTY, EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. IMMUNEX SHALL NOT BE LIABLE
TO LICENSEE FOR ANY USE OF LICENSED PATENT RIGHTS BY LICENSEE OR FOR ANY LOSS,
CLAIM, DAMAGE, OR LIABILITY, OF ANY KIND OR NATURE, WHICH MAY ARISE FROM OR IN
CONNECTION WITH THIS AGREEMENT. NEITHER PARTY TO THIS AGREEMENT SHALL BE
ENTITLED TO RECOVER FROM THE OTHER ANY SPECIAL INCIDENTAL, CONSEQUENTIAL OR
PUNITIVE DAMAGES. IN ADDITION, THE PARTIES MAKE NO REPRESENTATIONS AND EXTEND NO
WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, AND PARTICULARLY THAT
PRODUCTS WILL BE DEVELOPED HEREUNDER, WILL HAVE COMMERCIAL UTILITY OR
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. FURTHERMORE, IMMUNEX MAKES
NO WARRANTY EITHER EXPRESS OR IMPLIED THAT THE COMMERCIALIZATION OF DEVELOPED
PRODUCTS USING THE LICENSED PATENT RIGHTS WILL NOT INFRINGE ANY OTHER
INTELLECTUAL PROPERTY OF A THIRD PARTY.

     6.4  NO CONFLICT.  Each Party represents and warrants that, notwithstanding
anything to the contrary in this Agreement, the execution and delivery of this
Agreement and the performance of its obligations hereunder (a) do not conflict
with or violate any requirements of applicable laws or regulations and (b) do
not and shall not conflict with, violate or breach or constitute a default or
constitute a default or require any consent under, any contractual obligation.

7.  INDEMNIFICATION

     7.1  Licensee shall indemnify and hold harmless each of Immunex, its
successors and assigns, and the officers, employees, agents and counsel thereof
(the "Immunex Indemnities") from and against any and all claims of whatever
kind or nature, including, without limitation, any claim or liability based upon
any theory of negligence, warranty, strict liability, violation of government
regulation or infringement of patent or other proprietary rights, arising from
or occurring as a

                                       9
<PAGE>
result of (a) the use of Licensed Patent Rights and Developed Products by
Licensee or any agent of Licensee, or (b) any breach of this Agreement by
Licensee, provided:

          7.1.1  Licensee shall not be obligated under this Section to the
     extent that such claim or liability was the result of the breach of any
     warranty of Immunex set forth in Section 6.1 hereof, or gross negligence or
     willful misconduct of any employee or agent of Immunex;

          7.1.2  Licensee shall have no obligation under this Article unless
     Immunex (a) gives Licensee at least thirty (30) days written notice of any
     claim or liability for which it seeks to be indemnified under this
     Agreement, (b) Licensee is granted full authority and control over the
     defense, including settlement, of such claim or liability, and (c) Immunex
     cooperates fully with Licensee and its agents in defense of the claim or
     liability; and

          7.1.3  Immunex shall have the right, at its own expense, to have its
     own counsel participate in the defense of any such claim or liability
     referred to in this Article, provided, however, that Licensee shall have
     full authority and control to handle any such claim or liability, including
     any settlement or other disposition thereof, for which Immunex seeks
     indemnification under this Article and such counsel shall cooperate with
     Licensee.

8.  MISCELLANEOUS

     8.1  NOTICES.  All notices, reports, and other communications to Immunex or
Licensee shall be in writing (including electronic facsimile transmissions),
shall refer specifically to this Agreement and shall be sent by electronic
facsimile transmission or by registered mail or certified mail, return receipt
requested, postage prepaid, by express courier services providing evidence of
delivery, in each case to the respective address specified below (or to such
address as may be specified in writing to the other Party);

If addressed to Licensee:

                            Tanox, Inc.
                            10301 Stella Link
                            Houston, Texas 77025
                            Attention:  Nancy T. Chang, President
                            Fax:  (713) 664-8914

                            with a copy to:
                            Head of Legal Affairs
                            Fax:  (713) 664-8914

                                       10
<PAGE>
and if to Immunex shall be sent to:

                            Immunex Corporation
                            51 University Street
                            Seattle, Washington 98101
                            Attn:  General Counsel
                            Fax:  (206) 233-0644

     8.2  FORCE MAJEURE.  Immunex and Licensee shall each be excused for any
failure or delay in performing any of its respective obligations under this
Agreement if such failure or delay is caused by Force Majeure. The Party
affected by the Force Majeure shall use all reasonable efforts to correct the
Force Majeure as quickly as possible and to give the other Party prompt written
notice when it is again fully able to perform its obligations hereunder.

     8.3  ASSIGNABILITY.  Neither this Agreement nor the rights herein granted
may be assigned by either Party to any Third Party without the written consent
of the other, which consent shall not be unreasonably withheld; provided,
however, that either Party may assign this Agreement to any Affiliate, or to any
corporation with which it may merge or consolidate or to which it may transfer
all or substantially all of its assets to which this Agreement relates, without
obtaining the consent of the other Party.

     8.4  AMENDMENTS.  No terms or provisions of this Agreement shall be varied
or modified by any prior or subsequent statement, conduct or act of either of
the Parties, whether oral or written, except that the Parties may amend this
Agreement by written instruments specifically referring to and executed in the
same manner as this Agreement.

     8.5  SEVERABILITY.  If any provision hereof should be held invalid, illegal
or unenforceable in any respect in any jurisdiction, then, to the fullest extent
permitted by law, (a) all other provisions hereof shall remain in full force and
effect in such jurisdiction and shall be liberally construed in order to carry
out the intentions of the parties hereto as nearly as may be possible and (b)
such invalidity, illegality or unenforceability shall not affect the validity,
legality or enforceability of such provision in any other jurisdiction. To the
extent permitted by applicable law, Immunex and Licensee hereby waive any
provision of law that would render any provision hereof prohibited or
unenforceable in any respect. In the event that the terms and conditions of this
Agreement are materially altered as a result of this Section, the parties will
renegotiate the terms and conditions of this Agreement to resolve any
inequities.

                                       11
<PAGE>
     8.6  HEADINGS.  Headings used herein are for convenience only and shall not
in any way affect the construction of, or be taken into consideration
interpreting this Agreement.

     8.7  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, and all of such
counterparts taken together shall constitute one and the same instrument.

     8.8  ENTIRE AGREEMENT.  This Agreement, on and as of the Effective Date
hereof, constitutes the entire agreement between the parties relating to the
subject matter hereof and supersedes all previous or contemporaneous writings
and understanding, whether written or oral.

     8.9  BANKRUPTCY.  Notwithstanding the bankruptcy of Immunex, or the
impairment of performance by Immunex of its obligations under this Agreement as
a result of bankruptcy or insolvency of Immunex, Licensee shall be entitled to
retain the licenses granted herein, subject to Immunex's rights to terminate
this Agreement for reasons other than bankruptcy or insolvency as expressly
provided in this Agreement, and subject to performance by Licensee of its
preexisting obligations under this Agreement.

All rights and licenses granted under or pursuant to this Agreement by Immunex
to Licensee, are, and shall otherwise be deemed to be, for purposes of Section
365(n) of the U.S. Bankruptcy Code, licenses of rights to "intellectual
property" as defined under Section 101(52) of the U.S. Bankruptcy Code. The
parties agree that Licensee, as a license of such rights under this Agreement,
shall retain and may fully exercise all of its rights and elections under the
U.S. Bankruptcy Code, subject to performance by Licensee of its preexisting
obligations under this Agreement. The parties further agree that, in the event
of the commencement of a bankruptcy proceeding by or against Immunex under the
U.S. Bankruptcy Code, Licensee shall be entitled to a complete duplicate of (or
complete access to, as appropriate) any such intellectual property and all
embodiments of such intellectual property, and same, if not already in its
possession, shall be promptly delivered to Licensee (a) upon any such
commencement of a bankruptcy proceeding upon written request therefor by
Licensee, unless Immunex elects to continue to perform all of its obligations
under this Agreement, or (b) if not delivered under (a) above, upon the
rejection of this Agreement by or on behalf of Immunex upon written request
therefor by Licensee, provided, however, that upon Immunex's (or its
successor's) written notification to Licensee that it is again willing and able
to perform all of its obligations under this Agreement. Licensee shall promptly
return all such tangible materials to Immunex, but only to the extent that
Licensee does not require continued access to such materials to enable Licensee
to perform its obligations under this Agreement.

                                       12
<PAGE>
     8.10  RELATIONSHIP.  The relationship of employer and employee shall not
exist between Immunex and Licensee under this Agreement. This Agreement shall
not be deemed to establish a joint venture or partnership between Licensee and
Immunex. Nothing contained in this Agreement shall be construed, by implication
or otherwise, as an obligation incurred by Licensee to enter into any further
agreement with Immunex.

     8.11  APPLICABLE LAW.  This Agreement is acknowledged to have been made in
and shall be construed in accordance with the laws of the state of Washington
without reference to any rules govening conflicts of laws.

                      [This space is intentionally left blank.]

                                       13
<PAGE>
     8.12 PRESS RELEASE. No public announcement or other disclosure to Third
Parties (other than Affiliates and external collaborators) concerning the
existence of or terms of this Agreement shall be made, either directly or
indirectly, by either party, without first obtaining the written approval of the
other Party and agreement upon the nature and text of such announcement or
disclosure. The Party desiring to make my such public announcement or other
disclosure shall inform the other Party of the proposed announcement or
disclosure in reasonably sufficient time prior to public release and shall
provide the other Party with a written copy thereof, in order to allow such
other Party to comment upon such announcement or disclosure. Once any such
public announcement or disclosure has been approved in accordance with this
Section 8.12. then either Party may appropriately communicate information
contained in such permitted announcement or disclosure. Each Party shall
cooperate fully with the other with respect to all required disclosures
regarding this Agreement to the Securities and Exchange Commission or any other
governmental or regulatory agency. Each Party shall be entitled to disclose this
Agreement, its terms or other confidential information of the other obtained
pursuant to this Agreement with respect to disclosures regarding this Agreement
that are required by the Securities and Exchange Commission or any other
governmental or regulatory agency under applicable laws, rules and regulations.
Either Party may disclose such confidential information without the other
Party's prior written approval provided that the other Party is given an
opportunity to review and comment on the information being disclosed prior to
its disclosure, and that such information is disclosed only to the extent
required in order to comply with such applicable laws, rules and regulations or
with orders by courts of competent jurisdiction requiring such disclosures.

IN WITNESS WHEREOF, the parties have executed the Agreement and have entered the
effective date of the first page hereof.

         IMMUNEX CORPORATION                    TANOX, INC.
         By:  /s/BARRY G. PEA                   By:  /s/NANCY T. CHANG
         Name:  Barry G. Pea                    Name:  Nancy T. Chang
                Vice President and              Title:  President and CEO
         Title: Deputy General Counsel
         Date:  1-12-00                         Date:  1/11/00

                                       14

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