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                                                                   EXHIBIT 10.33

             ATALANTA/SOSNOFF CAPITAL CORPORATION (AND SUBSIDIARIES)
                              AMENDED AND RESTATED
                            MANAGEMENT INCENTIVE PLAN
                                     FOR THE
                       FIVE YEARS ENDING DECEMBER 31, 2003

      WHEREAS, in December 1992, the Board of Directors of Atalanta/Sosnoff
Capital Corporation and its direct and indirect subsidiaries (the "Company")
adopted a Management Incentive Plan (the "Original Plan") effective January 1,
1993 for the senior executive officers of the Company and identified the
participants therein for the three years ended December 31, 1995, subject to,
and upon the recommendation and approval of, the Compensation Committee (the
"Committee") of the Board of Directors, composed of the then two non-employee
directors, Messrs. Kenneth H. Iscol and Thurston Twigg-Smith, (the "Outside
Directors") and Martin T. Sosnoff, Chairman of the Board;

      WHEREAS, the Compensation Committee duly recommended and approved the
Original Plan in January 1993 and reported its recommendation and approval of
the Original Plan to the stockholders of the Company in its Report included in
the proxy statement of the Company furnished to stockholders in connection with
the 1993 Annual Meeting of Stockholders of the Company and the Company described
the Original Plan in that proxy statement;

      WHEREAS, subsequent to the adoption by the Board and the approval by the
Committee of the Original Plan, the Omnibus Budget Reconciliation Act of 1993
(the "Act") became law. Effective for fiscal years beginning on or after January
1, 1994, the Act denies deductions for federal income tax purposes for
compensation in excess of $1,000,000 per year to the chief executive officer and
to any of the four other most highly compensated officers, unless such
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compensation is excluded from the deduction limitation. Compensation under the
Original Plan was excluded from the deduction limitation since (i) the
performance goals were established by a compensation committee consisting solely
of two or more outside directors (a Compensation Sub-Committee was established
for that purpose (the "Compensation Sub-Committee")), (ii) the material terms
under which the compensation was to be paid, including the performance goals,
were disclosed to and approved by stockholders of the Company in a separate
vote, and (iii) prior to payment, the Compensation Sub-Committee certified that
the performance goals and any other material terms were in fact satisfied. The
Act also provides that stockholder approval and certification by the
Compensation Sub-Committee as described above must be made conditions to the
right of the executive to receive the performance based compensation. To comply
with the provisions of the Act to qualify the compensation payable to certain
executives under the Management Incentive Plan as performance based compensation
eligible for exclusion from the deduction limit, the Management Incentive Plan
as amended and restated was submitted to the stockholders for approval at the
1994 Annual Meeting of Stockholders. Consistent with the Act, the approval by
stockholders and certification by the Compensation Sub-Committee were made
conditions to the rights of a participant to receive any benefits under the
Management Incentive Plan with respect to fiscal years of the Company beginning
after December 31, 1993;

      WHEREAS, subsequent to its initial restatement, pursuant to its
recommendation and adoption by the Compensation Sub-Committee and the approval
of the Board of Directors, subject to stockholder approval, the Original Plan
was amended on July 29, 1996 (the "First Amendment") to change the method of
allocating Bonuses from the Annual Award Pool and the identity of the
Participants therein for the three years ended December 31, 1998 and the First

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Amendment was duly approved by stockholders at the 1996 Annual Meeting of
Stockholders;

      WHEREAS, pursuant to its recommendation and adoption by the Compensation
Sub-Committee and the approval of the Board of Directors on March 10, 1999 and,
subject to stockholder approval received at the 1999 Annual Meeting of
Stockholders, the Original Plan, as restated, and as amended by the First
Amendment, was amended and restated by the Second Amendment for the five years
ending December 31, 2003.

      WHEREAS, pursuant to its recommendation and adoption by the Compensation
Sub-Committee and the approval of the Board of Directors of the Company on
February 9, 2000 and, subject to stockholder approval to be sought at the 2000
Annual Meeting of Stockholders, the Original Plan, as restated, and as
previously amended by the First and Second Amendments, has been amended and
restated as provided herein for the five years ended December 31, 2003. (The
Original Plan as previously restated, and as amended by the First and Second
Amendments and, as amended and restated as provided herein is referred to herein
as the "Plan".);

      WHEREAS, the purpose of setting forth the Plan herein is to confirm the
terms of the Plan as adopted by the Board of Directors and recommended and
approved by the Compensation Sub-Committee for the five years ending December
31, 2003; and

      WHEREAS, a Compensation Sub-Committee of the Compensation Committee
consisting of two outside directors has established the performance goals set
forth in the Plan, and has approved and adopted the Plan and recommended its
approval by the stockholders of the Company.

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      Section 1. Purpose. The purpose of the Company's Plan is to provide a
stimulus to Participants to a continuing high level of commitment to further
improvement in the financial performance of the Company by giving them a direct
interest in the financial performance of the Company through basing incentive
compensation on exceeding base year adjusted operating earnings and relevant
benchmarks in investment performance. There are hereby established under the
Plan an Operating Earnings Component and an Investment Performance Component of
the Plan.

      Section 2. Term. Subject to stockholder approval, pursuant to Section 10,
the Plan shall be effective as of January 1, 1999 (the "Effective Date"), except
as otherwise set forth herein, and shall be applicable for each of the five
fiscal years of the Company during the period ending December 31, 2003, unless
amended or terminated by the Company pursuant to Section 9.

      Section 3. Coverage. For purposes of the Plan, the term "Participant"
shall include the senior executive officers of the Company serving as such at
any time during the fiscal year who are selected by the Compensation
Sub-Committee. As used herein, the term "Company" includes both the Company and
its direct and indirect subsidiaries, unless the context otherwise requires. The
Participants for the five fiscal years during the period ending December 31,
2003 were determined by the Compensation Sub-Committee and have been approved by
the Board of Directors and stockholders of the Company and their names and
titles and the Annual Award Pool in which they participate, and the inception
date thereof, are set forth on Exhibit A annexed hereto.

      Section 4.  Annual Award Pool.

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      4.1. For each fiscal year of the Company, each Participant shall be
entitled to receive a bonus award (a "Bonus") payable from an annual award pool
in which he participates, in an amount determined as provided in Section 5. For
each fiscal year, each Participant who was not a full year Participant shall be
entitled to a Bonus for such fiscal year to the extent set forth in Section 5.2
hereof. The annual award pools (each an "Annual Award Pool") shall consist of an
Operating Earnings Pool (the "Earnings Pool") in the Operating Earnings
Component of the Plan and two pools: an Investment Performance Pool (the
"Performance Pool") measured by the investment performance of the Company's
proprietary accounts, and a Sabre Pool (the "Sabre Pool") measured by the
Company's earnings from the management of Sabre Partners, L.P. and by the
performance of the Company's investment in that partnership in the Investment
Performance Component of the Plan.

      4.2. The Earnings Pool, the Performance Pool and the Sabre Pool for each
fiscal year shall be determined and paid as soon as practicable after the end of
such fiscal year of the Company and in no event later than 45 days thereafter
and shall be an amount determined as follows:

           (a)   The Earnings Pool

                 (i) If the Company's Adjusted Operating Earnings as defined in
Section 4.2(a)(iii) hereof for the fiscal year in which an Earnings Pool is to
be computed hereunder (the "Computation Year") exceeds the level of Adjusted
Operated Earnings achieved in fiscal year 1998 of $5,996,000 (the "Base Year"),
then subject to the limitation set forth in subsection (ii) hereof, the Earnings
Pool shall be an amount equal to the positive difference, if any, between
Adjusted Operating Earnings in the Computation Year and the Base Year

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multiplied by fifty percent (50%).

                 (ii) In no event shall the Earnings Pool as determined in
accordance with subsection (a) hereof exceed an amount which when subtracted
from the consolidated earnings of the Company would result in the reduction of
net earnings per share by more than ten percent 10%.

                 (iii) For purposes of this Plan, the "Adjusted Operating
Earnings" for a fiscal year shall be the consolidated operating earnings of the
Company and its subsidiaries, determined in accordance with generally accepted
accounting principles, plus amounts paid or accrued with respect to amounts
payable (A) under the Restricted Stock Bonus Plan of the Company, (B) under the
1996 Long Term Incentive Plan of the Company, (C) under this Plan, (D) as a
result of acquisitions, and (E) such other amounts paid, payable, accrued and/or
chargeable to operating income as the Sub-Committee shall determine in its
discretion should not be deducted from revenues for purposes of the Plan. By way
of example, but not limitation, the Sub-Committee has determined that amounts
chargeable to compensation expense in the acquisition of the business of William
M. Knobler should be added as an adjustment to operating earnings for purposes
of the Plan.

            (b)  The Performance Pool

                 (i) The Performance Pool for each fiscal year (a "Computation
Year") during which the Plan is in effect shall be computed by determining the
investment performance of the Company's proprietary accounts, consisting of
cash, cash equivalents, investments at market and investments in Company
sponsored investment companies and limited partnerships (referred to herein as
the "Account") in such Computation Year and comparing it to the

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performance of the Standard & Poors 500 Index (the "Benchmark") for such
Computation Year. The Investment Pool shall be an amount equal to twenty percent
(20%) of the positive difference, if any, by which the investment performance of
the Account in any Computation Year exceeds the Benchmark, multiplied by the
average market value of the Account during such Computation Year, provided,
however, that no amount shall be credited to the Performance Pool unless the
investment performance of the Account is positive. By way of example of the
foregoing, if (A) the Account had an average market value of $100 million during
the Computation Year, (B) the investment performance of the Account was 10%, and
(C) the Benchmark's performance was 8% in the Computation Year, then the
positive difference of 2% in performance would be multiplied by 20% and the
product of 0.4% would be multiplied by the average market value of the Account
during the Computation Year, resulting in a Performance Pool of $400,000.

                 (ii) In no event shall the Performance Pool, as determined in
accordance with subsection (b) hereof, considered separately from the Earnings
Pool and without aggregation with it, exceed an amount which when subtracted
from the consolidated earnings of the Company would result in the reduction of
net earnings per share by more than ten percent (10%).

            (c)  The Sabre Pool

                 (i) The Sabre Pool for each fiscal year (a "Computation Year")
during which the Plan is in effect shall be based upon the pre-tax operating
earnings of Sabre Partners, L.P. and the performance of the Company's investment
in the Partnership and shall be computed by determining:

                     (A) the investment performance of the Company's investment
in

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the Partnership (the "Sabre Account") in such Computation Year and comparing
it to the performance of the Standard & Poors 500 Index (the "Benchmark") for
such Computation Year. The Sabre Pool shall be credited with an amount equal to
twenty percent (20%) of the positive difference, if any, by which the investment
performance of the Sabre Account in any Computation Year exceeds the Benchmark,
multiplied by the average market value of the Account during such Computation
Year, provided, however, that no amount shall be credited to the Sabre Pool
unless the investment performance of the Account is positive. By way of example
of the foregoing, if (x) the Sabre Account had an average market value of $25
million during the Computation Year, (y) the investment performance of the
Account was 30%, and (z) the Benchmark's performance was 20% in the Computation
Year, then the positive difference of 10% in performance would be multiplied by
20% and the product of 2.0% would be multiplied by the average market value of
the Sabre Account during the Computation Year, resulting in a performance Pool
of $500,000

                     (B) the pre-tax operating profits earned by the Company
(the "Net Profit") (exclusive of any income earned on its investment in the
Partnership) in such Computation Year and multiplying the Net Profit by fifty
percent. The product of such calculation shall be credited to the Sabre Pool,
and

                     (C) the sum of the amounts credited to the Sabre Pool
pursuant to subparagraphs (A) and (B) of this subsection (c) of Section 4 hereof
which shall constitute the Sabre Pool for the Computation Year.

                 (ii) In no event shall the Sabre Pool, as determined in
accordance with subsection (c), paragraph (i) hereof, considered separately from
the Earnings Pool and

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Performance Pool and without aggregation with them, exceed an amount which when
subtracted from the consolidated earnings of the Company would result in the
reduction of Net Earnings per share by more than ten percent (10%).

      Section 5.  Allocations.

      5.1. A Bonus shall be allocated to each Participant from the Annual Award
Pool in which he participates in the percentages assigned to such Participant in
Exhibit A.

      5.2. Notwithstanding anything in this Plan to the contrary, any
Participant who ceases to be an employee of the Company for any reason (other
than death or disability) prior to the end of a fiscal year shall not be
entitled to a Bonus with respect to such year. If such Participant ceased to be
an employee of the Company by reason of death or disability prior to fiscal
year-end then a Bonus shall be allocated to such Participant for the full fiscal
year.

      5.3. The Compensation Sub-Committee may elect as to any or all of the
Participants to pay to any such Participant a portion of such Participant's
Bonus in shares of Common Stock, par value $.01 per share, of the Company valued
by the Compensation Sub-Committee as it shall determine in its discretion based
on the market value at the date of the issuance of such stock to such
Participant, the average market value thereof for an appropriate period prior to
such issuance, and taking into account, as it shall deem appropriate, the
non-marketability, of such stock or book value as determined in accordance with
generally accepted accounting principles, at the time of issuance provided,
however, that any proposed discount from market value for the Common Stock as so
determined to take account of such non-marketability, resulting in an increase
in the number of shares of the Common Stock issuable to any such Participant
shall not be taken if, upon advice of counsel, the Compensation Sub-Committee
determines that such

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discount would constitute an impermissible exercise of discretion by the
Compensation Sub-Committee increasing any such Participant's Bonus and resulting
in any portion of such Participant's compensation under the Plan not being
qualified performance based compensation deductible by the Company for federal
income tax purposes under Section 162(m) of the Internal Revenue Code of 1986,
as amended. In no event shall Company Common Stock issued to any such
Participant as so valued represent more than 25% of the value of such
Participant's Bonus for any fiscal year. The Participant shall acknowledge that
the disposition of any Common Stock awarded as a Bonus is subject to restriction
under federal and state securities laws and shall agree to such other
restrictions as the Compensation Sub-Committee may impose as a condition to the
issuance of such stock. The Compensation Sub-Committee may determine that
payment of a portion of the Bonuses shall be deferred, the periods of such
deferrals and the interest, if any, to be paid in respect to deferred payments.
The Compensation Sub-Committee may also define such other conditions of payment
of Bonuses as it may deem desirable in carrying out the purposes of the Plan.
Any Participant, prior to December 1 of any Computation Year, may elect to defer
receipt of his Bonus for such period, not exceeding ten years, as he shall
determine.

      5.4 The aggregate Bonuses awarded for any year shall not exceed the
applicable Annual Award Pool for such year, including amounts awarded to
Participants who were not employees of the Company for the entire fiscal year.
In any fiscal year, any balance in any Annual Award Pool attributable to a
forfeiture of Bonus under Section 5.3 as a result of a Participant ceasing to be
an employee during such year (collectively, "Unawarded Bonuses"), or any portion
thereof, shall be distributed among all remaining Participants in proportion to
their respective shares.

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      Section 6. Administration and Interpretation. The Plan shall be
administered by the Compensation Sub-Committee, which shall have the sole
authority to make rules and regulations for the administration of the Plan. The
interpretations and decisions of the Compensation Sub-Committee with regard to
the Plan shall be final and conclusive. The Compensation Sub-Committee may
request advice or assistance or employ such persons (including, without
limitation, legal counsel and accountants) as it deems necessary for the proper
administration of the Plan.

      Section 7. Administrative Expenses. Any expense incurred in the
administration of the Plan shall be borne by the Company out of its general
funds and not charged against the Annual Award Pool, except insofar as such
expenses shall be taken into account in determining Adjusted Operating Earnings
hereunder.

      Section 8. Amendment or Termination.

            (a) The Compensation Sub-Committee of the Company may from time to
time amend the Plan in any respect or terminate the Plan in whole or in part
(and shall terminate the Plan upon the happening of an event described in
subsection (b) hereof), provided, however, that no such action shall
retroactively impair or otherwise adversely affect the rights of any Participant
to benefits under the Plan which have accrued prior to the date of such action
and, provided, further, that no amendment to the Plan shall effect a change in
the material terms thereof which would result in any portion of a Bonus made
hereunder not being deductible for federal income tax purposes under Section
162(m) of the Internal Revenue Code of 1986, as amended.

            (b) The Plan shall be terminated upon a "change in control" as
defined herein.

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For the purposes hereof a change in control shall mean:

                 (i) a change in the majority of the Board of Directors so that
a majority of its members are comprised of persons not nominated by existing
members of the Board of Directors;

                 (ii) consummation of a transaction or series of transactions
as a result of which persons who currently own 50% of the outstanding common
stock of the Company cease to own 50% thereof; or

                 (iii) the Company shall cease to have a class of equity
securities registered pursuant to Sections 12(b) or 12(g) of the Securities
Exchange Act of 1934, as amended.

      Section 9. No Assignment. The rights of a Participant hereunder, including
without limitation the right to receive a Bonus, shall not be sold, assigned,
transferred, encumbered or hypothecated by a Participant (except by testamentary
disposition or intestate succession), and during the lifetime of any recipient
any payment of a Bonus shall be payable only to such recipient.

      Section 10. Stockholder Approval. This Plan shall be subject to approval
by an affirmative vote of the stockholders of the Company holding a majority of
the Common Stock of the Company outstanding at the 2000 Annual Meeting of
Stockholders with respect to all Bonuses accrued on or after January 1, 2000,
and such stockholder approval shall be a condition to the right of a Participant
to receive any such Bonus hereunder.

      Section 11. Certification by Compensation Sub-Committee. As a condition to
the right of a Participant to receive any Bonus under this Plan for fiscal years
beginning after

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December 31, 1998 the Compensation Sub-Committee shall first be required to
certify, by written resolution of the Compensation Sub-Committee or other
appropriate written certification, that the performance goals set forth in
Section 4.2 have been satisfied and that the applicable Annual Award Pool and
the Bonus for each Participant has been accurately determined in accordance with
the provisions of this Plan.

      Section 12. No Preclusion. Nothing in the Plan shall preclude the Board of
Directors of the Company, or any Committee or Sub-Committee of the Board
thereunto duly authorized, where circumstances warrant, from making
discretionary bonus payments to any of the Participants or to any other employee
of the Company, not made pursuant hereto.

Date Adopted:           February 9, 2000
Date Approved
by Stockholders:        ______________EXHIBIT 10.24

     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 (*).

                                MASTER AGREEMENT

     This MASTER AGREEMENT (the "Agreement") is entered into as of March 17,
2000 (the "Effective Date") by and between PROTEIN DESIGN LABS, INC., a
Delaware corporation having its principal office at 34801 Campus Drive, Fremont,
California 94555 U.S.A. ("PDL"), and TANOX, INC., a Delaware corporation
having offices at 10301 Stella Link, Houston, TX 77025 U.S.A. ("TANOX").

                                    RECITALS

     WHEREAS, PDL owns certain patents and related patent applications related
to humanized antibodies and antibody humanization technology that are sometimes
referred to as the "Queen et al. Patents."

     WHEREAS, PDL and TANOX are parties to a Patent License Agreement dated June
30, 1998, as amended by an amendment dated June 28, 1999 (as amended, the "Prior
Agreement").

     WHEREAS, PDL and TANOX desire to terminate the Prior Agreement and to enter
into this Agreement to provide TANOX the right to obtain certain nonexclusive
license rights under the Queen et al. Patents for the development, manufacture
and commercialization of antibody products directed against up to four antigens,
under the terms and conditions set forth below.

                                    AGREEMENT

     NOW, THEREFORE, the parties agree to follow:

1.  DEFINITIONS

     All references to particular Exhibits, Articles and Sections shall mean the
Exhibits to, and Articles and Sections of, this Agreement, unless otherwise
specified. References to this "Agreement" include the Exhibits. For the purposes
of this Agreement the following words and phrases shall have the following
meanings:

     1.1 "AFFILIATE" means, with respect to a party hereto, any corporate or
other entity which, directly or indirectly controls, is controlled by, or is
under common control with such party during the term of this Agreement, where
"control" means the ownership of not less than fifty percent (50%) of the voting
shares of a corporation, or decision-making authority as to an unincorporated
entity, provided that such entity shall be an Affiliate only so long as such
control exists.

     1.2 "ANTIBODY" means any antibody directed against an Antigen and shall
include, without limitation, monospecific and bispecific antibodies (but a
separate license shall be required for each Antigen targeted by a bispecific
antibody); less than full-length antibody forms such as Fv, Fab, Fab' and
F(ab')2; single-chain antibodies; and antibody conjugates bound to a toxin,
label or other moiety.

     1.3 "ANTIGEN" means a target molecule to which an Antibody specifically
binds and includes all epitopes on that target molecule.

     1.4 "LICENSED PRODUCT" means an Antibody with respect to which TANOX has
either significant marketing rights or has done significant development
(including without limitation created, humanized or conducted preclinical or
clinical development), the manufacture, import, use, offer to sell or sale of
which would infringe, if not licensed under this Agreement, a Valid Claim. *

     1.5 "PDL LICENSE AGREEMENT" means the form of PDL License Agreement
attached as Exhibit B.
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     1.6 "PDL PATENT RIGHTS" means the patent applications or patents (as well
as any foreign counterparts thereto identified on Exhibit A. PDL Patent Rights
shall include U.S. or foreign patents or patent applications which claim
priority to any application to which a listed U.S. Patent also claims priority.
PDL Patent Rights shall also include any foreign equivalents, including any
additions, continuations, continuations-in-part or divisions of such patents or
patent applications, or any substitute applications therefor; any patents issued
with respect to such patent applications, any reissues, extensions or patent
term extensions of any such patent, and any confirmation patents or registration
patents or patents of addition based on any such patents.

     1.7  "TANOX NAMED ANTIGENS"  shall mean: *

     1.8 "VALID CLAIM" means (a) any claim in any issued patent included in the
PDL Patent Rights which would be infringed but for the license granted under
Section 2.01 and which claim has not been disclaimed or held unenforceable or
invalid by a governmental agency or court of competent jurisdiction by a
decision from which no appeal has been taken within the time period permitted
for filing an appeal or may be taken; and (b) any pending claims under PDL
Patent Rights which, if granted, would be infringed but for the license granted
under Section 2.01 and which pending claim would be a Valid Claim if the pending
claim were treated as granted, provided that examination has been timely
requested for such pending claims and they are otherwise being diligently
prosecuted in an effort to have them allowed and granted in an issued patent.

2.  RIGHTS TO LICENSES

     2.1 ELECTION. Subject to the terms and conditions of this Agreement, PDL
hereby grants to TANOX through the * anniversary of the Effective Date
(or until such earlier time as TANOX has exercised its rights under this Section
2.1 with respect to four (4) Antigens), the rights upon written notice to
receive licenses under the PDL Patent Rights for up to four (4) Antigens
designated by TANOX. Each license shall be a nonexclusive, worldwide license
under the PDL Patent Rights to make, have made, use, import, market, promote,
offer for sale and sell or otherwise dispose of Antibodies pursuant to a PDL
License Agreements. The rights of TANOX under the PDL License Agreements shall
include the right to grant sublicenses for Antibodies in accordance with the
terms of the applicable PDL License Agreement. Each license elected by TANOX
hereunder shall be pursuant to a separate PDL License Agreement and effective as
of the date when the election for such license by TANOX becomes irrevocable,
pursuant to Section 2.2.

     2.2 PROCEDURE FOR EXERCISE OF LICENSE RIGHTS. TANOX shall provide PDL with
written notice identifying the Antigen for which TANOX desires to enter into a
PDL License Agreement pursuant to the provisions of Section 2.1. A separate
notice shall be provided with respect to each Antigen for which a license is
requested. Within fifteen (15) business days of the written notice or upon
execution and return of the relevant PDL License Agreement by PDL, whichever is
later, TANOX shall pay the applicable License Exercise Fee specified in Section
3.2. PDL shall promptly review and respond in writing to the request by TANOX
for a license within ten (10) business days of receipt of the written request.
PDL may refuse to grant TANOX a license only if PDL has previously granted an
exclusive or co-exclusive license or an unexpired option for an exclusive or
co-exclusive license with respect to an Antibody to the identical Antigen, can
demonstrate that it is then actively engaged in bona fide negotiations for such
an exclusive or co-exclusive license or option for an exclusive or co-exclusive
license, or then has development, marketing or co-promotion rights, or an option
to obtain such rights, to a product or a potential product directed against the
Antigen and which is on the market or in research or development and reasonably
expected to enter human clinical trials within twenty-four (24) months;
provided, however, that with respect to each of the Tanox Named Antigens, PDL
shall provide Tanox with written notice prior to entering into an exclusive or
co-exclusive license, development, marketing or co-promotion rights, or option
for such license or rights, with any third party with respect to that Tanox
Named Antigen and shall permit Tanox the opportunity to exercise its rights
under Section 2.1 for a period not to exceed fifteen (15) days for a

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license for that Tanox Named Antigen prior to conclusion of an agreement with
such third party for a license or option; * In the event that PDL validly
refuses to grant TANOX a license under the PDL Patent Rights, TANOX' right under
Section 2.1 shall not be considered exercised. If PDL affirms TANOX' request or
has not responded by notice in writing with ten (10) business days of receipt of
TANOX' request under this Section 2.2, then TANOX' election shall be deemed
irrevocable and TANOX and PDL shall enter into a PDL License Agreement with
respect to that Antigen.

3.  PAYMENTS

     3.1 INITIAL FEES. Within thirty (30) days after the Effective Date, TANOX
shall pay an initial nonrefundable, noncreditable fee of * for the right to
obtain nonexclusive licenses pursuant to Section 2.1.

     3.2 LICENSE EXERCISE FEES. Within fifteen (15) business days after the
delivery of a written notice to PDL for a nonexclusive license for Antibodies
for one (1) Antigen under Section 2.1 or PDL's execution of a PDL license
Agreement for the same, whichever is later, TANOX shall pay to PDL an exercise
fee ("License Exercise Fee") of * provided that such amount shall be increased
annually beginning April 1, 2001 and on each April 1 thereafter by an amount
equal to the Consumer Price Index-U (or its successor) published by the U.S.
Bureau of Labor Statistics ("CPI-U") for the prior calendar year; provided,
however, that if the CPI-U for the prior year has not been published by April 1
of the applicable year, any adjustments hereunder shall be payable within
fifteen (15) days of the publication of the CPI-U for the applicable year.

4.  TERMINATION OF PRIOR AGREEMENT

     In partial consideration of the rights granted to TANOX in Article 2, the
parties agree that upon execution and delivery of this Agreement, the Prior
Agreement shall immediately terminate and be of no further force or effect.

5.  REPRESENTATIONS, DISCLAIMERS

     5.1 VALID AGREEMENT. Each party represents and warrants to the other that
it knows of no legal reason to, and is not a party to any agreement which would,
prevent it from entering into and performing its obligations under this
Agreement, and the the signatory hereto is duly authorized to execute and
deliver this Agreement.

     5.2 CURRENT PDL PATENT RIGHTS. The PDL Patent Rights constitute all of the
patents and patent applications owned by PDL as of the Effective Date which
relate generally on the humanization of antibodies.

     5.3 NO WARRANTY OF VALIDITY, NON-INFRINGEMENT. Nothing in this Agreement
shall be construed as (a) a warranty or representation by PDL as to the validity
or scope of any PDL Patent Rights; or (b) a warranty or representation that any
Licensed Product made, used, sold or otherwise disposed of under any PDL License
Agreement is or will be free from infringement of patents, copyrights,
trademarks, trade secrets or other rights of third parties.

     5.4 DISCLAIMER OF WARRANTIES. EXCEPT AS SPECIFICALLY SET FORTH IN SECTIONS
5.1 AND 5.2, NEITHER PDL NOR TANOX MAKE TO THE OTHER ANY REPRESENTATIONS OR
EXTEND ANY WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED. FURTHER, PDL DOES
NOT MAKE ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE OR THAT PRACTICE UNDER THE PDL PATENT RIGHTS UNDER A PDL LICENSE
AGREEMENT WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

                                        3
<PAGE>
6.  CONFIDENTIALITY

     6.1 PRIOR AGREEMENTS. This Agreement supersedes the Prior Agreement;
provided, however, that with respect to all Confidential Information disclosed
thereunder and/or within the definition of "Confidential Information" in the
Prior Agreement, or information otherwise subject to the terms and conditions of
Section 6.02 of the Prior Agreement, such Confidential Information shall be
subject to the terms and conditions of Section 6.2 of this Agreement.

     6.2 CONFIDENTIALITY. PDL and TANOX acknowledge that in the course of
negotiations of this Agreement or other discussions between the parties of
prospective agreements or business relationships and/or in furtherance of the
interests of the parties hereunder that it ("Recipient") has received and/or may
receive confidential information of the other party ("Provider"). "Confidential
Information" means any and all data and information which (a) has been reduced
to tangible form and marked clearly and conspicuously with a legend identifying
its confidential or proprietary nature; or (b) with respect to any oral
presentation or communication, is or was designated as confidential immediately
before, during, or within a reasonable time after the oral presentation or
communication and such designation is subsequently confirmed in writing; (c) is
or was otherwise characterized by Provider as confidential information; or (d)
is subject to the terms and conditions of this Section 6.2 as provided in
Section 6.1.

     Each party shall keep and protect as confidential, and shall not use for
any purpose (other than TANOX' use for the development and commercial
exploitation of Licensed Products or either party's use for specific purposes
otherwise contemplated by a business relationship entered into between them),
during the term of this Agreement and for five (5) years after termination
hereof, all Confidential Information heretofore and hereafter supplied by the
other, provided however, that the foregoing obligations of confidentiality shall
not apply to the extent that any Confidential Information (a) is already known
to the Recipient at the time of disclosure, as evidenced by written record, or
is developed by Recipient thereafter in the course of work entirely independent
of any disclosure by the other party; (b) is publicly known prior to or becomes
publicly known after disclosure other than through acts of omissions of the
Recipient; (c) is disclosed in good faith to Recipient by a third party who is
not under obligations of non-disclosure to the Provider; (d) is required to be
disclosed pursuant to an order of a court of law or regulation of a governmental
agency; provided that the disclosing party shall advise the other party promptly
of any such disclosure requirement (other than a filing of information or
materials with the U.S. Securities and Exchange Commission made with a request
for confidential treatment for portions of such material for which such
treatment may reasonably be expected to be granted) in order to permit such
other party to undertake efforts to restrict or limit the required disclosure
including by cooperating in drafting a protective order; or (e) disclosure is
made to a government regulatory agency as part of such agency's biological
license approval process.

7.  TERM AND TERMINATION

     7.1 TERM. Unless earlier terminated in accordance with this Article 7, this
Agreement shall remain in effect until the expiration of the last PDL License
Agreement.

     7.2  TERMINATION.

     (a) If either party shall at any time default in the making of any payment
hereunder, or shall commit any material breach of any covenant or agreement
herein contained, and shall fail to have initiated and actively pursued remedy
of any such default or breach within sixty (60) days after receipt of written
notice thereof by the other party, the other party may, at its option, cancel
this Agreement and revoke any rights herein granted by notice in writing to such
effect, but such act shall not prejudice the right of the party giving notice to
recover any sums due at the time of such cancellation, it being understood,
however, that if within sixty (60) days after receipt of any such notice the
receiving party shall have initiated and actively pursued remedy of its default,
then the rights herein

                                        4
<PAGE>
granted shall remain in force as if no breach or default had occurred on the
part of the receiving party, unless such breach or default is not in fact
remedied within a reasonable period of time.

     (b) This Agreement may be terminated by either party upon the occurrence of
any of the following which is not stayed or vacated within ninety (90) days of
such occurrence: (i) petition in bankruptcy filed by or against the other party;
(ii) adjudication of the other party as bankrupt or insolvent; (iii) appointment
of a liquidator, receiver or trustee for all or a substantial part of the other
party's property; or (iv) an assignment for the benefit of creditors of the
other party.

     (c) All right and licenses granted under or pursuant to this Agreement by
PDL to TANOX, 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 TANOX, as a licensee of such rights under this Agreement,
shall retain and may fully exercise all of its right and elections under the
U.S. Bankruptcy Code, subject to performance by TANOX of its preexisting
obligations under this Agreement.

     (d) To the extent permitted under applicable law, the rights granted under
this agreement may be terminated as to any country by PDL upon thirty (30) days
prior written notice in the event that TANOX challenges the PDL Patent Rights in
that country.

     7.3 NO WAIVER. The right of either party to terminate this Agreement as
provided herein shall not be affected in any way by its waiver of, or failure to
take action with respect to, any previous failure to perform hereunder.

     7.4 RIGHTS AND OBLIGATIONS UPON TERMINATION OR EXPIRATION. Upon expiration
or termination of this Agreement for any reason, nothing herein shall be
construed to release either party from any obligation that matured prior to the
effective date of such termination. In addition, the obligations set forth in
Articles 6 and 7 shall survive the expiration or termination of this Agreement.
Upon termination of this Agreement, each party shall return to the other party
any confidential information disclosed by the other party under this Agreement.

8.  MISCELLANEOUS

     8.1 ASSIGNMENT. This Agreement may not be assigned by either party without
the prior written consent of the other, except to Affiliates upon prior written
notice to the other party, and except that either party may assign this
Agreement to a party which acquires all or substantially all of its business,
whether by merger, sale of assets or otherwise.

     8.2 ENTIRE AGREEMENT. This Agreement constitutes the entire Agreement
between the parties hereto with respect to the within subject matter and
supersedes all previous Agreements (except as provided in Section 6.1), whether
written or oral. This Agreement shall not be changed or modified orally, but
only by an instrument in writing signed by both parties.

     8.3 SEVERABILITY. If any provision of this Agreement is declared invalid by
a court of last resort or by any court, the decision of which appeal is not
taken within the time provided by law, then and in such event, this Agreement
will be deemed to have been terminated only as to the portion thereof which
relates to the provision invalidated by that decision and only in the relevant
jurisdiction, but this Agreement, in all other respects and all other
jurisdictions, will remain in force; provided, however, that if the provision so
invalidated is essential to the Agreement as a whole, then the parties shall
negotiate in good faith to amend the terms hereof as nearly as practical to
carry out the original interest of the parties, and, failing such amendment,
either party may submit the matter to a court of competent jurisdiction for
resolution.

     8.4 NOTICES. Any notice or report required or permitted to be given under
this Agreement shall be in writing and shall be sent by expedited delivery or
telecopied and confirmed by mailing, as follows and shall be considered received
three (3) days after such delivery:

                                        5
<PAGE>
If to PDL:                 Protein Design Labs, Inc.
                           34801 Campus Drive
                           Fremont, California 94555 USA
                           Attention: Chief Executive Officer
                           Fax No: 510-574-1500

Copy to:                   Protein Design Labs, Inc.
                           34801 Campus Drive
                           Fremont, California 94555 USA
                           Attention: General Counsel
                           Fax No: 510-574-1473

If to TANOX:               Tanox, Inc.
                           10301 Stella Link
                           Houston, TX 77025 USA
                           Attention: Nancy T. Chang, President and CEO
                           Fax No: (713) 664-8914

Copy to:                   Tanox, Inc.
                           10301 Stella Link
                           Houston, TX 77025 USA
                           Attention: Head of Legal Affairs

     8.5  DISPUTE RESOLUTION.

     (A) NEGOTIATIONS. Any dispute, controversy or claim arising out of or
relating to any provision of this Agreement or a PDL License Agreement or the
interpretation, enforceability, performance, breach, termination or validity
hereof or thereof, including without limitation, this dispute resolution
provision, shall be subject to the procedures set forth in this Section 8.5. A
designated representative of PDL and TANOX will meet as reasonably requested by
either party to review any dispute, controversy or claim arising out of or
relating to any provision of this Agreement or a PDL License Agreement. If the
disagreement is not resolved by the designated representatives by mutual
agreement within thirty (30) days after a meeting to discuss the disagreement,
either party may at any time thereafter provide the other written notice
specifying the terms of such disagreement in reasonable detail. Upon receipt of
such notice, the chief executive officers of PDL and TANOX shall meet at a
mutually agreed upon time and location for the purpose of resolving such
disagreement. They will discuss the problems and/or negotiate for a period of up
to sixty (60) days in an effort to resolve the disagreement or negotiate an
acceptable interpretation or revision of the applicable portion of this
Agreement or a PDL License Agreement, as applicable, mutually agreeable to both
parties, without the necessity of formal procedures relating thereto. During the
course of such negotiations, the parties will reasonably cooperate and provide
information that is not materially confidential in order that each of the
parties may be fully informed with respect to the issues in dispute. The
institution of a formal legal proceeding under Section 8.5(b) or (c) to resolve
the disagreement may occur by written notice to the other party only after the
earlier of: (a) the chief executive officers mutually agreeing that resolution
of the disagreement through continued negotiation is not likely to occur, or (b)
following expiration of the sixty (60) day negotiation period.

     (B) ARBITRATION. Subject to Section 8.5(a), any dispute, controversy or
claim arising out of or in connection with or relating to this Agreement or a
PDL License Agreement or the breach or alleged breach thereof, but not including
any dispute, controversy or claim concerning the validity of any PDL Licensed
Patent, shall be submitted by the parties to arbitration in Denver, Colorado in
accordance with the then-current JAMS Comprehensive Arbitration Rules and
Procedures under the auspices of JAMS ("JAMS") except as otherwise provided
herein. If the dispute, controversy or claim concerns the validity of any PDL
Licensed Patent, all matters subject to dispute, controversy or claim hereunder
shall be removed to Federal District Court as provided in Section 8.5(c).

     Any arbitration proceeding hereunder shall be held in English and a
transcribed record prepared in English. The parties shall choose, by mutual
agreement, one (1) neutral arbitrator within thirty (30)

                                        6
<PAGE>
days of receipt of notice of the intent to arbitrate. If no arbitrator is
appointed within the times herein provided or any extension of time which is
mutually agreed upon, JAMS shall make such appointment of a person who shall
devote substantial time to arbitrating within thirty (30) days of such failure.
Discovery permitted by the arbitrator shall be pursuant to the Federal Rules of
Civil Procedure, provided that all discovery shall be completed within sixty
(60) days of the appointment of such arbitrator and the decision rendered by
such arbitrator shall thereafter be delivered in writing setting forth the basis
therefor within thirty (30) days after the completion of discovery. The award
rendered by the arbitrator shall include costs of arbitration, reasonable
attorneys' fees and reasonable costs for expert and other witnesses, and
judgment on such award may be entered in any court having jurisdiction thereon.
Nothing in this Agreement shall be deemed as preventing either party from
seeking injunctive relief (or any other provisional remedy) from any court
having jurisdiction over the parties and the subject matter of the dispute but
only to the extent necessary to protect either party's name, proprietary
information, trade secrets, know-how or any other similar proprietary rights. If
the issues in dispute involve scientific or technical matters related to
monoclonal antibody technology, any arbitrator chosen hereunder shall have not
less than five (5) years of educational training and/or experience sufficient to
demonstrate a reasonable level of relevant scientific and/or technical knowledge
related to monoclonal antibody technology or such arbitrator shall have the
right to appoint an expert with such experience to assist such arbitrator as
necessary. If the issues in dispute involve patent matters (other than validity
of a PDL Licensed Patent), then such arbitrator shall also be knowledgeable
about patent law matters and to the extent possible, with monoclonal antibody
technology. The decision of the arbitrator shall be in writing and shall set
forth the basis therefor. The arbitrator shall have the authority to award such
remedies as he or she believes appropriate in the circumstances, including, but
not limited to, compensatory damages subject to the Three and Three-Quarters
Percent (3.75%) royalty maximum set forth in the PDL License Agreement,
consequential and incidental damages, interest, tort damages (but not punitive
or similar damages) and specific performance and other equitable relief.

     (C) PATENT VALIDITY. Subject to Section 8.5(a), any dispute, controversy or
claim (i) which involves the validity of a PDL Licensed Patent issued in the
United States shall be subject to actions before the United States Patent and
Trademark Office and/or adjudicated in Federal District Court, Central District,
Santa Clara County in the State of California and (ii) which involves the
validity of a PDL Licensed Patent issued in any other country shall be brought
before an appropriate regulatory or administrative body or court in that
country. The prevailing party shall be entitled to recover from the other party,
the reasonable attorneys' fees, costs and expenses incurred by such prevailing
party in connection with any action or proceeding under this Section 8.5(c).

     8.6 CHOICE OF LAW. The validity, performance, construction, and effect of
this Agreement shall be governed by the laws of the State of California which
are applicable to contracts between California residents to be performed wholly
within California.

     8.7 WAIVER. None of the terms, covenants and conditions of this Agreement
can be waived except by the written consent of the party waiving compliance.

     8.8 FORCE MAJEURE. Neither party shall be responsible to the other for
failure or delay in performing any of its obligations under this Agreement or
for other non-performance hereof provided that such delay or non-performance is
occasioned by a cause beyond the reasonable control and without fault or
negligence of such party, including, but not limited to war, terrorism,
earthquake, fire, flood, explosion, discontinuity in the supply of power, court
order or governmental interference, act of God, strike or other labor trouble
and provided that such party will inform the other party as soon as is
reasonably practicable and that it will entirely perform its obligations within
a reasonable time after the relevant cause has ceased its effect.

     8.9 PUBLICITY. PDL will issue a press release concerning the parties' entry
into this Agreement and the amount of the initial fees to be paid hereunder,
with the content of such release to be

                                        7
<PAGE>
approved in advance by TANOX, which approval shall not be unreasonably withheld.
Except as required by law or regulation, neither party shall publicly disclose
the other terms and conditions of this Agreement unless expressly authorized to
do so by the other party, which authorization shall not be unreasonably
withheld; provided, however that the parties may disclose such terms and
conditions to their respective investors, prospective investors, advisors, and
consultants under a written confidentiality agreement protecting the
confidentiality of the terms hereof as provided under Article 6, and to their
accountants and attorneys provided that such accountants and attorneys agree to
maintain the confidentiality of the terms hereof as provided under Article 6,
and either party may disclose such terms and conditions as deemed required in
connection with any securities offering it elects to make.

     8.10 HEADINGS. The captions used herein are inserted for convenience of
reference only and shall not be construed to create obligations, benefits, or
limitations.

     8.11 COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, and such
counterparts together shall constitute one agreement. Execution and delivery of
this Agreement by facsimile copies bearing the facsimile signatures of the
parties shall constitute a valid and binding execution and delivery of this
Agreement by the signing party, and such facsimile copies shall constitute
original documents.

     IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as
of the Effective Date.

PDL:                               TANOX:
PROTEIN DESIGN LABS, INC.          TANOX, INC.

By:  /s/ LAURENCE JAY KORN         By:  /s/ NANCY T. CHANG
    ----------------------             --------------------
     Laurence Jay Korn                  Nancy T. Chang
     CEO                                President and CEO

                                        8
<PAGE>
                                    EXHIBIT A

                                PDL PATENT RIGHTS

The following are patents and patent applications (also known as the "Queen et
al. patents") issued and filed in certain countries in the world and licensed as
part of the PDL Patent Rights under the Agreement. (Updated as of January 27,
2000.)

1.  The following issued U.S. patents and U.S. patent applications:

        No. 5,585,089, "Humanized Immunoglobulins," issued December 17, 1996.

        No. 5,693,761, "Polynucleotides Encoding Improved Humanized
        Immunoglobulins," issued December 2, 1997.

        No. 5,693,762, "Humanized Immunoglobulins," issued December 2, 1997.

        *

2.  The following patents and patent applications outside the U.S.:

<TABLE>
<CAPTION>
PATENT NO.                          COUNTRY                           TITLE*
<S>             <C>                 <C>              <C>
                                                          "Novel Immunoglobulins, Their

Issued          647383              Australia                  Production and Use"
Issued          671949              Australia                           "
Issued          AT E133452          Austria                             "
Issued          0451216             Belgium                             "
Issued          61095               Bulgaria                            "
Issued          98389               Chile                               "
Issued          P920500A            Croatia                             "
Issued          0451216B1           Europe1                             "
Issued          0682040 B1          Europe1                             "
Issued          FR0451216           France                              "
Issued          DE 68925536         Germany                             "
Issued          DE 68929061         Germany                             "
Issued          DD 296 964          East Germany                        "
Issued          GB 0451216          Great Britain                       "
Issued          1001050             Greece                              "
Issued          211174              Hungary                             "
Issued          IT 0451216          Italy                               "
Issued          2828340             Japan                               "
Issued          LU 0451216          Luxembourg                          "
Issued          92.2146             Monaco                              "
Issued          NL 0451216          Netherlands                         "
Issued          231984              New Zealand                         "
Issued          132068              Pakistan                            "
Issued          29729               Philippines                         "
Issued          92758               Portugal                            "
Issued          2126046             Russia                              "
Issued          SG 0451216          Singapore                           "
Issued          8912489             Slovenia                            "
Issued          89/9956             South Africa                        "
Issued          178385              South Korea                         "
Issued          0231090             South Korea                         "
Issued          2081974 T3          Spain                               "
Issued          2136760             Spain
</TABLE>

                                        9

LEGAL COMMON/CONTRACTS/TANOX/LIC OPTN/MSTR000316                          000316
<PAGE>
<TABLE>
<S>             <C>                 <C>              <C>
Issued          SE 0451216          Sweden                              "
Issued          CH 0451216          Switzerland                         "
Issued          50034               Taiwan                              "
Issued          13349               Uruguay                             "
Issued          56455               Venezuela                           "
Issued          48700               Yugoslavia                          "
<CAPTION>
                COUNTRY             APPLICATION NO.                   TITLE*

Pending            *                      *                             *
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
</TABLE>

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

* Exact titles may differ in different countries.

1 and corresponding European national patents issued therefrom.

                                       10
<PAGE>

                                    EXHIBIT B

                          FORM OF PDL LICENSE AGREEMENT

                                       11
<PAGE>
                                    EXHIBIT B

                            PATENT LICENSE AGREEMENT

     This Agreement ("Agreement"), effective as of

("Effective Date"), is made by and between PROTEIN DESIGN LABS, INC., a
Delaware corporation having offices at 34801 Campus Drive, Fremont, CA 94555,
U.S.A. (hereinafter "PDL") and TANOX, INC., a Delaware corporation having
offices at 10301 Stella Link, Houston, TX 77025, U.S.A. (hereinafter "TANOX").

                                    RECITALS

     A. TANOX and PDL have entered in a Master Agreement effective March 17,
2000 (the "Master Agreement"), pursuant to which TANOX may enter into this
Agreement with respect to a license under the PDL Patent Rights (as defined
below) for TANOX'S antibody products.

     B. The Master Agreement provides TANOX with the right to obtain a
nonexclusive, worldwide, royalty-bearing license under the PDL Patent Rights
under the terms and conditions of this Agreement.

                                    AGREEMENT

     NOW THEREFORE, in consideration of the mutual covenants herein contained
and intending to be legally bound, the parties agree as follows:

1.  DEFINITIONS

     All references to Exhibits, Articles and Sections shall be references to
Exhibits, Articles and Sections of this Agreement. In addition, except as
otherwise expressly provided herein, the following terms in this Agreement shall
have the following meanings:

     1.01 "AFFILIATE" means with respect to a party hereto, any corporate or
other entity which, directly or indirectly, controls, is controlled by, or is
under common control with such party where "control" means the ownership of not
less than 50% of the voting shares of a corporation, or decision-making
authority as to an unincorporated entity.

     1.02 "ANTIBODY" means any antibody directed against an Antigen, including,
without limitation, monospecific and bispecific antibodies; less than
full-length antibody forms such as Fv, Fab, and F(ab')2; single-chain
antibodies; and antibody conjugates bound to a toxin, label or other moiety.

     1.03  "ANTIGEN" means the target molecule:
                                    .

     1.04 "COMBINATION PRODUCT(S)" shall mean any product containing both a
pharmaceutically active agent or ingredient which constitutes a Licensed Product
and one or more other pharmaceutically active agents or ingredients which do not
constitute Licensed Products.

     1.05 "LICENSED PRODUCT(S)" shall mean therapeutic products of TANOX or
TANOX'S sublicensees or Affiliates that include an Antibody developed by or for
TANOX or its Affiliates, jointly or otherwise, binding to the Antigen whose
development, manufacture, use or sale would, but for a license under this
Agreement, infringe a Valid Claim.

     1.06 "NET SALES" shall mean the aggregate gross revenues, whether in cash
or in kind, derived by or payable from or on account of the sale of Licensed
Products, less actual amounts incurred for (a) credits or allowances, if any,
actually granted on account of price adjustments, recalls, rejection or return
of items previously sold, (b) excise and sales taxes, duties or other taxes
imposed on and paid with respect to such sales (excluding income or franchise
taxes of any kind) and (c) outer packing, freight and freight insurance costs.
All amounts deducted under this Section 1.06 shall be properly documented and
specified in any summary report provided to PDL under Section 3.07. If TANOX or
any of its Affiliates or sublicensees receive non-cash consideration for any
Licensed Product sold or

                                        1
<PAGE>
otherwise transferred to an independent third party not an Affiliate of the
seller or transferor, the fair market value of such non-cash consideration on
the date of such transfer as known to TANOX, or as reasonably estimated by TANOX
if unknown, shall be included in the definition of Net Sales.

     1.07 "PDL PATENT RIGHTS" means the patent applications or patents (as well
as any foreign counterparts thereto) identified on EXHIBIT A. PDL Patent Rights
shall include U.S. or foreign patents or patent applications which claim
priority to any application to which a listed U.S. Patent also claims priority.
PDL Patent Rights shall also include any foreign equivalents, additions,
continuations, continuations-in-part or divisions of such patents or patent
applications or any substitute applications therefor; any patents issued with
respect to such patent applications, any reissues, extensions or patent term
extensions of any such patent, and any confirmation patents or registration
patents or patents of addition based on any such patents.

     1.08 "VALID CLAIM" means (a) any claim in any issued patent included in the
PDL Patent Rights which would be infringed but for the license granted under
Section 2.01 and which claim has not been disclaimed or held unenforceable or
invalid by a governmental agency or court of competent jurisdiction from which
no appeal has been taken within the time period permitted for filing an appeal
or may be taken; and (b) any pending claims under PDL Patent Rights which, if
granted, would be infringed but for the license granted under Section 2.01 and
which pending claim would be a Valid Claim if the pending claim were treated as
granted, provided that examination has been timely requested for such pending
claims and they are otherwise being diligently prosecuted in an effort to have
them allowed and granted in an issued patent.

2.  LICENSE

     2.01 LICENSE GRANT. Subject to the terms and conditions of this Agreement,
PDL hereby grants and TANOX hereby accepts a worldwide nonexclusive license
under the PDL Patent Rights, including the right to grant sublicenses in
accordance with Section 2.02 to make, import, have made, use, offer to sell or
sell Licensed Products.

     2.02 LIMITATION ON SUBLICENSES; NOTIFICATION. TANOX shall have the right to
grant sublicenses of its rights with respect to the Licensed Product under
Section 2.01 only to its Affiliates or in connection with the assignment or
license by TANOX of a Licensed Product to a third party. Notwithstanding the
assignment or grant of a sublicense by TANOX hereunder, TANOX shall remain
obligated to pay all royalties due to PDL with respect to the sale of Licensed
Products by its assignee or sublicensee. In addition, the grant of any
sublicenses under Section 2.01 shall be on terms and conditions which are
subject to and subordinate to the terms of this Agreement and TANOX shall remain
fully responsible to PDL for the performance of any and all such terms by its
sublicensees. Promptly following execution of any sublicense hereunder, but in
any event not less than ten (10) days thereafter, TANOX shall notify PDL of the
identity of the sublicensee and the scope of the sublicense.

     2.03 NO OTHER LICENSE RIGHTS. TANOX expressly acknowledges and agrees that,
except for the license expressly granted under Section 2.01, no rights to any
other PDL patents, patent applications, know-how or licenses are included in
this Agreement and that any royalties or payments that may be due to third
parties in order for TANOX to make, have made, use or sell Licensed Products
shall be the sole responsibility of TANOX.

     2.04 UPDATES TO LIST OF PDL PATENT RIGHTS. Upon written request of TANOX,
which request shall not be made more than once per calendar year, PDL agrees to
provide a written update listing the patents and patent applications under the
PDL Patent Rights, and such update shall constitute an amendment to Exhibit "A."
PDL may, at its option, furnish such update to TANOX from time to time during
the terms of this Agreement as part of an update to the Master Agreement.

                                        2
<PAGE>
3.  PAYMENT; ROYALTIES, REPORTS

     3.01 PAYMENTS.  In consideration for the licensed granted by PDL under
Article 2 of this Agreement TANOX shall pay to PDL a nonrefundable signing and
licensing fee by the later of fifteen (15) business days after Tanox' exercise
of its right under the Master Agreement to enter into this Agreement or the
Effective Date, the sum of                         United States Dollars
(US$            [DRAFTING NOTE: ENTER AMOUNT CALCULATED UNDER SECTION 3.2 OF THE
MASTER AGREEMENT]

     3.02 ROYALTIES TO PDL. Subject to reduction for any offset as provided in
Section 3.05, or withholding under Section 3.09(b), and in further consideration
of the rights and licenses granted under Article 2, TANOX shall pay to PDL a
royalty of * of the Net Sales of all Licensed Products sold by TANOX or its
Affiliates or sublicensees in each country until the last date on which there is
a Valid Claim that, but for a license granted to TANOX under this Agreement,
would be infringed by the making, using, having made or sale of that Licensed
Product in such country or by the manufacture of Licensed Product in the country
of manufacture.

     3.03 SALES AMONG AFFILIATES. Sales between and among TANOX and its
Affiliates or sublicensees of Licensed Products which are subsequently resold or
to be resold by such Affiliates or sublicensees shall not be subject to royalty,
but in such cases royalties shall accrue and be calculated on the sale of such
Licensed Products to a third party.

     3.04 COMBINATION PRODUCTS. Net Sales in a particular country, in the case
of the Combination Products for which the pharmaceutically active agent or
ingredient constituting a Licensed Product and each of the other
pharmaceutically active agents or ingredients not constituting Licensed Products
have established market prices in that country in the Territory when sold
separately, shall be determined by multiplying the Net Sales for each such
Combination Product by a fraction, the numerator of which shall be the
established market price for the Licensed Product(s) contained in the
Combination Product and the denominator of which shall be the sum of the
established market prices for the Licensed Product(s) plus the established
market prices for the other pharmaceutically active agents or ingredients
contained in the Combination Product. When such separate market prices are not
established in that country, then the parties shall negotiate in good faith to
determine a fair and equitable method of calculating Net Sales in that country
for the Combination Product in question.

     3.05 ANNUAL MAINTENANCE FEE. In further consideration of the licenses
granted under Article 2, following the second (2nd) anniversary of the Effective
Date and not later than each anniversary thereafter within thirty (30) days
after receipt of an invoice from PDL, TANOX shall pay PDL a nonrefundable annual
maintenance fee in the amount of *. An amount of fifty percent (50%) of the
annual maintenance fee paid by TANOX hereunder shall be creditable against
royalties payable to PDL pursuant to Section 3.02 beginning in the year in which
a Biologist License Application ("BLA") or foreign equivalent thereof is filed
with the U.S. Food and Drug Administration (or any successor thereto, or a
foreign counterpart agency), with respect to a Licensed Product; provided that
in no event shall any portion of the annual maintenance fees paid prior to the
year in which a BLA is filed with respect to the Licensed Product be creditable
against royalties hereunder.

     3.06 CURRENCY CONVERSION. All amounts payable to PDL under this Agreement
shall be payable in U.S. Dollars by wire transfer to a bank account designated
by PDL. In the case of royalties on Net Sales, all amounts payable shall first
be calculated in the currency of sale and then converted into U.S. Dollars using
the average of the daily exchange rates for such currency quoted by Citibank,
N.A. for each of the last fifteen (15) banking days of each calendar quarter.

     3.7  ROYALTY REPORTS.

     (A)  CURRENT REPORTS.  TANOX agrees to make written reports and royalty
payments to PDL within sixty (60) days after the close of each calendar quarter
during the terms of this Agreement,

                                        3
<PAGE>
beginning with the calendar quarter in which the date of first sale of Licensed
Product by TANOX, its Affiliates or sublicensees, following regulatory approval
occurs. These reports shall show for the calendar quarter in question Net Sales
by TANOX, its Affiliates and sublicensees of the Licensed Products in the
Territory on a country-by-country basis, details of the quantities of Licensed
Products sold in each country and the country of manufacture, if different,
applicable offsets, withholding taxes and the net royalty due to PDL thereon
pursuant to Article 3. No later than at the time of the making of each such
report, TANOX shall make any payment due to PDL of royalties for the period
covered by such report.

     (B) TERMINATION REPORT. For each Licensed Product, TANOX also agrees to
make a written report to PDL within ninety (90) days after the date on which
TANOX, its Affiliates or sublicensees last sell that Licensed Product stating in
such report the same information required by quarterly reports for all such
Licensed Products made, sold or otherwise disposed of which were not previously
reported to PDL.

     3.08 INSPECTION. TANOX agrees to keep clear, accurate and complete records
for a period of at least three (3) years after each reporting period in which
Net Sales occur showing the manufacturing, sales and other disposition of
Licensed Products in the Territory in sufficient detail to enable the royalties
payable hereunder to be determined. TANOX further agrees to permit its books and
records to be examined by an independent accounting firm selected by PDL and
reasonably satisfactory to TANOX from time-to-time but not more than once a
year. Such examination is to be made at the expense of PDL, except in the event
that the results of the audit reveal that TANOX underpaid PDL by * or more, then
the audit fees shall be paid by TANOX. Any such discrepancies will be promptly
corrected by a payment or refund, as appropriate.

     3.09  WITHHOLDING.

     (A) PAYMENTS. All amounts payable under Section 3.01 and 3.05 shall
represent the actual proceeds to be received by PDL, net of any withholding or
other taxes or levies that may be applicable to such payments. PDL agrees to
reasonably cooperate with TANOX in obtaining a refund of any withholding taxes
or levies paid by TANOX if any, with respect to any payments to PDL hereunder.
In the event that PDL is successful in obtaining any refund of tax withholding
amounts paid by TANOX under this Agreement, PDL agrees to promptly remit such
refund amount to TANOX.

     (B) ROYALTY PAYMENTS. TANOX may withhold from royalties due to PDL amounts
for payment of any withholding tax that TANOX has actually paid to any taxing
authority with respect to the royalty payments due to PDL hereunder, provided
that such amounts are properly documented and specific in any summary report to
PDL hereunder. TANOX agrees to reasonably cooperate with PDL in obtaining a
foreign tax credit in the U.S. with respect to royalties due to PDL on the sale
or manufacture of Licensed Products at the sole expense of PDL.

4.  PATENT PROSECUTION AND MAINTENANCE.

     4.01  PROSECUTION.  PDL hereby agrees that, at its own expense it will use
commercially reasonable efforts to:

     (a) prosecute any patent applications included in the PDL Patent Rights and
     to secure the most extensive protection reasonably obtainable under the PDL
     Patent Rights; and

     (b) maintain the claims in patents included in the PDL Patent Rights as
     valid and enforceable claims for the full term thereof.

     4.02 UPDATES. Upon the written request of TANOX (which request shall not be
made more than once per calendar year), PDL agrees to provide a written update
of the information relating to the PDL Patent Rights as set forth on EXHIBIT A.

                                        4
<PAGE>
     4.03 DEFENSE OF PDL PATENT RIGHTS. With respect to the PDL Patent Rights
licensed under this Agreement, PDL at its sole cost and expense agrees to take
all steps and proceedings and to undertake such other acts as PDL may, in its
sole discretion, deem necessary or advisable to restrain any infringement or
improper or unlawful use of the PDL Patent Rights and to recover any actual or
punitive compensation therefor. TANOX shall provide reasonable assistance to PDL
and permit PDL to have the sole right to take such steps, conduct any such
proceedings or undertake any such action to restrain any infringement or
improper or unlawful use of the PDL Patent Rights, whether or not TANOX is a
party to such steps, proceedings or actions, all of which shall be at PDL's
expense. Any monies recovered from alleged infringers shall be retained by PDL.

5.  REPRESENTATIONS AND WARRANTIES; INDEMNIFICATION

     5.01 VALID AGREEMENT. Each party represents and warrants to the other that
it knows of no legal reason to, and is not a party to any agreement which would,
prevent it from entering into and performing its obligations under this
Agreement and that the signatory hereto is duly authorized to execute and
deliver this Agreement.

     5.02 NO WARRANTY OF VALIDITY, NON-INFRINGEMENT. Nothing in this Agreement
shall be construed as (a) a warranty or representation by PDL as to the validity
or scope of any PDL Patent Rights; or (b) a warranty or representation that any
Licensed Product made, used, sold or otherwise disposed of under the license
granted in this Agreement is or will be free from infringement of patents,
copyrights, trademarks, trade secrets or other rights of third parties.

     5.03 NO OTHER WARRANTIES. EXCEPT AS SPECIFICALLY SET FORTH IN ARTICLE 5,
PDL MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND, EITHER EXPRESS OR
IMPLIED, WITH RESPECT TO ANY CELL LINES, ANTIBODIES OR LICENSED PRODUCTS
DEVELOPED BY TANOX UNDER THE LICENSE SET FORTH IN THIS AGREEMENT AND PDL FURTHER
MAKES NO EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, OR THAT THE USE OF ANY CELL LINES, ANTIBODIES, LICENSED
PRODUCTS OR OTHER MATERIALS DEVELOPED BY TANOX UNDER THE LICENSE SET FORTH IN
THIS AGREEMENT WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

     5.04 INDEMNIFICATION. TANOX shall at all times, during the term of this
Agreement and thereafter, indemnify and hold harmless PDL and its Affiliates,
sublicensees, directors, officers, agents and employees from any claim,
proceeding, loss, expense, and liability of any kind whatsoever (including but
not limited to those resulting from death, personal injury, illness or property
damage and including legal expenses and reasonable attorneys' fees) arising out
of or resulting from (a) any claim of patent infringement (direct or
contributory) or including patent infringement with respect to the activities of
TANOX and (b) the development, manufacture, holding, use, testing,
advertisement, sale or other disposition by TANOX, its Affiliates or
sublicensees, or any distributor, customer or representative of TANOX or any one
in privity therewith, of any Licensed Product; provided, however, that PDL shall
promptly notify TANOX of such claim, proceeding, loss, expense or liability and
TANOX, at TANOX's cost, shall have sole control over the defense, including
settlement of any claim or action, with full cooperation from PDL.

6. CONFIDENTIALITY. PDL and TANOX acknowledge that in the course of negotiations
of this Agreement or other discussions between the parties of prospective
agreements or business relationships and/or in furtherance of the interests of
the parties hereunder that each has received and/or may receive confidential
information of the other party. To the extent that such information is
"Confidential Information" as defined in Section 6.2 of the Master Agreement,
each party is subject to the obligations of such Section 6.2 with respect to the
Confidential Information.

                                        5
<PAGE>
7.  TERM AND TERMINATION

     7.01 TERM. Unless earlier terminated as provided in this Article 7, this
Agreement shall come into force on the Effective Date and shall continue until
the expiration of the last obligation of TANOX to pay royalties to PDL in
accordance with Article 3 above. Thereafter, with the exception of the surviving
clauses specified in Section 7.04, this Agreement shall terminate and all
licenses or sublicenses granted hereunder shall become fully paid-up,
irrevocable licenses.

     7.02  TERMINATION.

        (A) This Agreement may be terminated in its entirety on sixty (60) days
prior written notice by TANOX.

        (B) If TANOX shall at any time default in the payment of any royalty, or
the making of any report hereunder, or shall commit any material breach of any
covenant or agreement herein contained or shall make any false report, and shall
fail to have initiated and actively pursued remedy of any such default or breach
within sixty (60) days after receipt of written notice thereof by the other
party, PDL may, at its option, cancel this Agreement and revoke any rights and
licenses herein granted and directly affected by the default or breach by notice
in writing to such effect, but such act shall not prejudice PDL's rights to
recover any royalty or other sums due at the time of such cancellation, it being
understood, however, that if within sixty (60) days days after receipt of any
such notice TANOX shall have initiated and actively pursued remedy of its
default, then the rights and licenses herein granted shall remain in force as if
no breach or default had occurred on the part of TANOX, unless such breach or
default is not in fact remedied within a reasonable period of time. If TANOX
disputes the existence of a default or material breach or making a false report
or the failure to pursue a remedy or to remedy the default or breach, the
provisions for resolution of a default shall be limited to those set forth in
Section 8.5 of the Master Agreement.

        (C) This Agreement may be terminated by either party upon the occurrence
of any of the following which is not stayed or vacated within ninety (90) days
of such occurrence: (i) petition in bankruptcy filed by or against the other
party; (ii) adjudication of the other party as bankrupt or insolvent; (iii)
appointment of a liquidator, receiver or trustee for all or a substantial part
of the other party's property; or (iv) an assignment for the benefit of
creditors of the other party.

        (D) All rights and licenses granted under or pursuant to this Agreement
by PDL to TANOX, 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 TANOX, as a licensee 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 TANOX of its preexisting
obligations under this Agreement.

        (E) To the extent permitted under applicable law, the license granted
under this Agreement may be terminated as to any country by PDL upon thirty (30)
days prior written notice in the event that TANOX challenges any PDL Patent
Rights in that country.

     7.03 NO WAIVER. The right of either party to terminate this Agreement as
provided herein shall not be affected in any way by its waiver of, or failure to
take action with respect to, any previous failure to perform hereunder.

     7.04  SURVIVAL.

        (A) Termination for any reason hereunder shall not affect any accrued
rights or obligations of the parties arising in any manner under this Agreement
as of the date of termination. In any event, the confidentiality and indemnity
obligations and any accrued payment and reporting obligations under Articles 3,
5 and 6 shall survive any termination of this Agreement.

                                        6
<PAGE>
        (b) Upon termination of this Agreement under Section 7.02(c), PDL hereby
grants TANOX a license to sell within three (3) months of such termination any
Licensed Products in TANOX' or TANOX' Affiliate's or sublicensee's inventory on
the date of such termination, which have not previously been sold ("Inventory");
provided, however, that TANOX shall pay the royalties due on such inventory,
provide related reports and allow a final audit in the amounts and manner
provided for in Sections 7.07 and 3.08.

     7.05 DISPUTES. The provisions of Section 8.5 of the Master Agreement are
incorporated by reference as if set forth in their entirety herein.

8.  MISCELLANEOUS

     8.01 ASSIGNMENT. This Agreement may not be assigned by either party without
the prior written consent of the other, except to Affiliates upon prior written
notice to the other party, and except that either party may assign this
Agreement to a party which acquires all or substantially all of its business,
whether by merger, sale of assets or otherwise.

     8.02 ENTIRE AGREEMENT. This Agreement and the Master Agreement constitute
the entire agreement between the parties hereto with respect to the within
subject matter and together they supersede all previous agreements (except as
otherwise provided in the Master Agreement), whether written or oral. This
Agreement shall not be changed or modified orally, but only by an instrument in
writing signed by both parties.

     8.03 SEVERABILITY. If any provision of this Agreement is declared invalid
by a court of last resort or by any court, the decision of which appeal is not
taken within the time provided by law, then and in such event, this Agreement
will be deemed to have been terminated only as to the portion thereof which
relates to the provision invalidated by that decision and only in the relevant
jurisdiction, but this Agreement, in all other respects and all other
jurisdictions, will remain in force; provided, however, that if the provision so
invalidated is essential to the Agreement as a whole, then the parties shall
negotiate in good faith to amend the terms hereof as nearly as practical to
carry out the original interest of the parties, and failing such amendment,
either party may submit the matter to a court of competent jurisdiction for
resolution.

     8.04 NOTICES. Any notice or report required or permitted to be given under
this Agreement shall be in writing and shall be sent by expedited delivery or
telecopied and confirmed by mailing, as follows and shall be considered received
three (3) days after such delivery.

          If to PDL:             Protein Design Labs, Inc.
                                 34801 Campus Drive
                                 Fremont, California 94555 USA
                                 Attention: Chief Executive Officer
                                 Fax No: 510-574-1500

          Copy to:               Protein Design Labs, Inc.
                                 34801 Campus Drive
                                 Fremont, California 94555 USA
                                 Attention: General Counsel
                                 Fax No: 510-574-1473

          If to TANOX:           Tanox, Inc.
                                 10301 Stella Link
                                 Houston, TX 77025 USA
                                 Attention: Nancy T. Chang, President and CEO
                                 Fax No: (713) 664-8914

          Copy to:               Tanox, Inc.
                                 10301 Stella Link
                                 Houston, TX 77025 USA
                                 Attention: Head of Legal Affairs

                                        7
<PAGE>
     8.05 CHOICE OF LAW. The validity, performance, construction, and effect of
this Agreement shall be governed by the laws of the State of California which
are applicable to contracts between California residents to be performed wholly
within California.

     8.06 WAIVER. None of the terms, covenants and conditions of this Agreement
can be waived except by the written consent of the party waiving compliance.

     8.07 FORCE MAJEURE. Neither party shall be responsible to the other for
failure or delay in performing any of its obligations under this Agreement or
for other non-performance hereof provided that such delay or non-performance is
occasioned by a cause beyond the reasonable control and without fault or
negligence of such party, including, but not limited to war, terrorism,
earthquake, fire, flood, explosion, discontinuity in the supply of power, court
order or governmental interference, act of God, strike or other labor trouble
and provided that such party will inform the other party as soon as is
reasonably practicable and that it will entirely perform its obligations within
a reasonable time after the relevant cause has ceased its effect.

     8.08 PUBLICITY. PDL will issue a press release concerning the parties'
entry into this Agreement and the amount of signing and licensing fees paid
hereunder, with the content of such release to be approved in advance by TANOX,
which approval shall not be unreasonably withheld. Except as required by law or
regulation, neither party shall publicly disclose the other terms and conditions
of this Agreement unless expressly authorized to do so by the other party, which
authorization shall not be unreasonably withheld, and both parties agree that
PDL shall not disclose the antigen which is the subject of this Agreement,
without TANOX' prior written consent; provided, however, that the parties may
disclose such terms and conditions to their respective investors, prospective
investors, advisors, and consultants under a written confidentiality agreement
protecting the confidentiality of the terms hereof in a manner at least as
restrictive as provided under Article 6 of the Master Agreement, and to their
accountants and attorneys provided that such accountants and attorneys agree to
maintain the confidentiality of the terms hereof in a manner at least as
restrictive as provided under Article 6 of the Master Agreement, and either
party may disclose such terms and conditions as deemed required in connection
with any securities offering it elects to make.

     8.09 HEADINGS. The captions used herein are inserted for convenience of
reference only and shall not be construed to create obligations, benefits, or
limitations.

     8.10 COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, and such
counterparts together shall constitute one agreement. Execution and delivery of
this Agreement by facsimile copies bearing the facsimile signatures of the
parties shall constitute a valid and binding execution and delivery of this
Agreement by the signing party, and such facsimile copies shall constitute
original documents.

     IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as
of the date first above written.

PDL:                                                    TANOX:
PROTEIN DESIGN LABS, INC.                               TANOX, INC.

By:______________________                               By:___________________
     Laurence Jay Korn                                  Nancy T. Chang
     CEO                                                President and CEO

                                        8
<PAGE>
                                    EXHIBIT A

                                PDL PATENT RIGHTS

The following are patents and patent applications (also known as the "Queen et
al. patents") issued and filed in certain countries in the world and licensed as
part of the PDL Patent Rights under the Agreement. (Updated as of January 27,
2000.)

1.  The following issued U.S. patents and U.S. patent applications:

        No. 5,585,089, "Humanized Immunoglobulins," issued December 17, 1996.

        No. 5,693,761, "Polynucleotides Encoding Improved Humanized
        Immunoglobulins," issued December 2, 1997.

        No. 5,693,762, "Humanized Immunoglobulins," issued December 2, 1997.

        *

2.  The following patents and patent applications outside the U.S.:

<TABLE>
<CAPTION>
PATENT NO.                          COUNTRY                           TITLE*
<S>             <C>                 <C>              <C>
                                                          "Novel Immunoglobulins, Their

Issued          647383              Australia                  Production and Use"
Issued          671949              Australia                           "
Issued          AT E133452          Austria                             "
Issued          0451216             Belgium                             "
Issued          61095               Bulgaria                            "
Issued          98389               Chile                               "
Issued          P920500A            Croatia                             "
Issued          0451216B1           Europe1                             "
Issued          0682040 B1          Europe1                             "
Issued          FR0451216           France                              "
Issued          DE 68925536         Germany                             "
Issued          DE 68929061         Germany                             "
Issued          DD 296 964          East Germany                        "
Issued          GB 0451216          Great Britain                       "
Issued          1001050             Greece                              "
Issued          211174              Hungary                             "
Issued          IT 0451216          Italy                               "
Issued          2828340             Japan                               "
Issued          LU 0451216          Luxembourg                          "
Issued          92.2146             Monaco                              "
Issued          NL 0451216          Netherlands                         "
Issued          231984              New Zealand                         "
Issued          132068              Pakistan                            "
Issued          29729               Philippines                         "
Issued          92758               Portugal                            "
Issued          2126046             Russia                              "
Issued          SG 0451216          Singapore                           "
Issued          8912489             Slovenia                            "
Issued          89/9956             South Africa                        "
Issued          178385              South Korea                         "
Issued          0231090             South Korea                         "
Issued          2081974 T3          Spain                               "
Issued          2136760             Spain
</TABLE>

                                        9

LEGAL COMMON/CONTRACTS/TANOX/LIC OPTN/MSTR000316                          000316
<PAGE>
<TABLE>
<S>             <C>                 <C>              <C>
Issued          SE 0451216          Sweden                              "
Issued          CH 0451216          Switzerland                         "
Issued          50034               Taiwan                              "
Issued          13349               Uruguay                             "
Issued          56455               Venezuela                           "
Issued          48700               Yugoslavia                          "
<CAPTION>
                COUNTRY             APPLICATION NO.                   TITLE*

Pending            *                      *                             *
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
Pending
</TABLE>

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

* Exact titles may differ in different countries.

1 and corresponding European national patents issued therefrom.

                                       10

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