XOMA LTD
S-3, 1996-06-28
PHARMACEUTICAL PREPARATIONS
Previous: ALLEGIANCE CORP, 10-12B, 1996-06-28
Next: LORD ABBETT AFFILIATED FUND INC, NSAR-A, 1996-07-01




As filed with the Securities and Exchange Commission on June 28, 1996
                                                       Registration No. 333-    
- - --------------------------------------------------------------------------------
                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549
                              -------------------

                                    FORM S-3
                             REGISTRATION STATEMENT
                                     Under
                           THE SECURITIES ACT OF 1933
                              -------------------

                                XOMA CORPORATION
             (Exact name of registrant as specified in its charter)

           Delaware                          94-2756657
(State or other jurisdiction of           (I.R.S. Employer
incorporation or organization)          Identification No.)

                        2910 Seventh Street
                    Berkeley, California  94710
                          (510) 644-1170
   (Address, including ZIP code, and telephone number, including
      area code, of registrant's principal executive offices)
                       --------------------

                   CHRISTOPHER J. MARGOLIN, ESQ.
                         XOMA CORPORATION
                        2910 Seventh Street
                    Berkeley, California  94710
                          (510) 644-1170
(Name, address, including ZIP code, and telephone number, including
                 area code, of agent for service)
                       --------------------

                             Copy to:
                    GEOFFREY E. LIEBMANN, ESQ.
                      CAHILL GORDON & REINDEL
                          80 Pine Street
                     New York, New York  10005
                          (212) 701-3000

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

    Approximate date of commencement of proposed sale to the public:
    From time to time after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant
to dividend or interest reinvestment plans, please check the following box.  /_/

If any of the securities being registered on this Form are to be offered on a
delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box.  /X/





     
<PAGE>
If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following
box and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering.  /_/
 
If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement 
for the same offering.  /_/

If delivery of the prospectus is expected to be made pursuant to Rule 434, 
please check the following box.  /_/
<TABLE>
<CAPTION>

                          CALCULATION OF REGISTRATION FEE

- - --------------------------------------------------------------------------------
Title of Each Class                  Proposed            Proposed  
   of Securities         Amount       Maximum             Maximum        Amount of
       To Be             To Be    Offering Price         Aggregate    Registration
    Registered        Registered    per Unit(1)     Offering Price(1)     Fee     
- - --------------------------------------------------------------------------------
<S>                   <C>            <C>               <C>               <C>
Common Stock,
par value $.0005
per share......       1,500,000(2)   $6.53             $9,795,000        $3,378
- - ---------------------------------------------------------------------------------
</TABLE>
(1) Estimated solely for purposes of computing the registration fee
    pursuant to Rule 457(c).

(2) Includes a like number of Preferred Stock Purchase Rights (the
    "Rights").  Since no separate consideration is paid for the
    Rights, the registration fee is included in the fee for the
    Common Stock.

The Registrant hereby amends this Registration Statement on such date
or dates as may be necessary to delay its effective date until the
Registrant shall file a further amendment which specifically states
that this Registration Statement shall thereafter become effective in
accordance with Section 8(a) of the Securities Act of 1933 or until
the Registration Statement shall become effective on such date as the
Commission, acting pursuant to said Section 8(a), may determine.
- - -------------------------------------------------------------------------









     
<PAGE>
            SUBJECT TO COMPLETION, DATED JUNE 28, 1996

                         1,500,000 Shares

                         XOMA CORPORATION

                           COMMON STOCK

          This Prospectus relates to 1,500,000 shares of Common
Stock, par value $.0005 per share (the "Common Stock"), of XOMA
Corporation (the "Company"), which have been registered for sale
from time to time by the selling stockholder named herein (the
"Selling Stockholder").  Any or all of the Common Stock being reg-
istered hereby may be sold from time to time to purchasers
directly by the Selling Stockholder.  Alternatively, the Selling
Stockholder may from time to time offer the Common Stock through
underwriters, dealers or agents who may receive compensation in
the form of underwriting discounts, concessions or commissions
from the Selling Stockholder and/or the purchasers of Common Stock
for whom they may act as agent.  The Company will receive no pro-
ceeds from the sale by the Selling Stockholder of the Common Stock
offered hereby.  The shares of Common Stock to which this Prospec-
tus relates were issued to the Selling Stockholder in the Private
Placement (as defined herein).  All Registration Expenses (as
defined herein) incurred in connection with the registration of
the Common Stock to which this Prospectus relates will be borne by
the Company.  The Company has agreed to indemnify the Selling
Stockholder against certain liabilities, including certain liabil-
ities under the Securities Act of 1933, as amended (the "Securi-
ties Act"), or to contribute to payments which the Selling Stock-
holder may be required to make in respect thereof.   See "Plan of
Distribution."  

          The Common Stock is traded on the Nasdaq National Market
under the symbol "XOMA."  The last reported bid price of the Com-
mon Stock as reported by the Nasdaq National Market on June 27,
1996 was $6.50 per share.

          The Common Stock offered hereby involves a high degree
of risk.  See "Risk Factors."
                       ---------------------

THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE
SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMIS-
SION NOR HAS THE SECURITIES AND EXCHANGE COMMISSION OR ANY STATE
SECURITIES COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THIS
PROSPECTUS.  ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL
OFFENSE.
                       ---------------------

          The date of this Prospectus is           , 1996.


     
<PAGE>
     Information contained herein is subject to completion or amendment.  A
registration statement relating to these securities has been filed with the
Securities and Exchange Commission.  These securities may not be sold nor may
offers to buy be accepted prior to the time the registration statement becomes
effective.  This prospectus shall not constitute an offer to sell or the
solicitation of an offer to buy nor shall there be any sale of these securities
in any State in which such offer, solicitation or sale would be unlawful prior
to registration or qualification under the securities laws of any such state.












































     
<PAGE>
                               -2-



                             AVAILABLE INFORMATION

          The Company is subject to the informational requirements of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), and is
required to file periodic reports, proxy statements and other information with
the Securities and Exchange Commission (the "SEC") relating to its business,
financial statements and other matters.  Such reports, proxy statements and
other information may be inspected and copied at the public reference facilities
maintained by the SEC at Judiciary Plaza, 450 Fifth Street, N.W., Washington,
D.C. 20549, and at the regional offices of the SEC located at 500 West Madison
Street, Suite 1400, Chicago, Illinois 60661 and at Seven World Trade Center,
13th Floor, New York, New York 10048.  Copies of such material can also be
obtained from the SEC at prescribed rates from the Public Reference Section of
the SEC at 450 Fifth Street, N.W., Washington, D.C. 20549.

          The Company has filed a Registration Statement on Form S-3 with the
SEC under the Securities Act with respect to the Common Stock offered hereby.
As permitted by the rules and regulations of the SEC, this Prospectus omits
certain information contained in the Registration Statement.  For further
information, reference is made to the Registration Statement, including the
financial schedules and exhibits incorporated therein by reference or filed as a
part thereof.  Statements made in this Prospectus as to the contents of any
contract, agreement or other document referred to are not necessarily complete,
and, in each instance, reference is made to the copy of such document filed as
an exhibit to the Registration Statement or otherwise filed with the SEC.  Each
such statement shall be deemed qualified in its entirety by such reference. 

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

          The Company will provide without charge to each person to whom a copy
of this Prospectus is delivered, upon the written or oral request of such
person, a copy of any or all of the documents incorporated herein by reference
(other than exhibits to such documents, unless such exhibits are specifically
incorporated by reference in such documents).  Requests for such copies should
be directed to Director, Corporate Communications, XOMA Corporation, 2910
Seventh Street, Berkeley, California 94710, (510) 644-1170.













     
<PAGE>
                               -3-



                     INFORMATION INCORPORATED BY REFERENCE

     The following documents filed by the Company with the SEC pursuant to the
Exchange Act are hereby incorporated by reference in this Prospectus:

          (1)  Annual Report on Form 10-K for the fiscal year ended December 31,
     1995 as amended by Amendment No. 1 on Form 10-K/A and Amendment No. 2 on
     Form 10-K/A (File No. 0-14710);

          (2)  Quarterly Report on Form 10-Q for the quarterly period ended
     March 31, 1996 (File No. 0-14710);

          (3)  Current Report on Form 8-K dated April 22, 1996 (File No.
     0-14710); and

          (4)  The description of XOMA's Common Stock in the Registration
     Statement on Form 8-A dated June 9, 1986 filed on June 11, 1986 under
     Section 12 of the Exchange Act, including any amendment or report for the
     purpose of updating such description (Registration No. 33-4793).

          All documents filed by the Company with the SEC pursuant to Section
13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this Prospectus
and prior to the termination of the offering of the Common Stock offered hereby
shall be deemed to be incorporated by reference in this Prospectus and to be a
part hereof from the date any such document is filed.

          Any statements contained in a document incorporated by reference in
this Prospectus shall be deemed to be modified or superseded for purposes of
this Prospectus to the extent that a statement contained in this Prospectus (or
in any other subsequently filed document which also is incorporated by reference
in this Prospectus) modifies or supersedes such statement.  Any statement so
modified or superseded shall not be deemed to constitute a part of this
Prospectus except as so modified or superseded.

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

          No person has been authorized in connection with the offering made
hereby to give any information or make any representation not contained in this
Prospectus and, if given or made, such information or representation must not be
relied upon as having been authorized by the Company or any other person.  This
Prospectus does not constitute an offer to sell or solicitation of any offer to
buy any of the securities offered hereby in any jurisdiction in which it is
unlawful to make such offer or solicitation.  Neither the delivery of this
Prospectus nor any sale made hereunder shall, under any circumstances, create
any implication that the information contained herein is correct as of any date
subsequent to the date hereof.  









     
<PAGE>
                               -4-



                                  RISK FACTORS

          In addition to the other information included or incorporated by
reference in this Prospectus, the following factors should be considered
carefully in evaluating an investment in the shares of Common Stock offered by
this Prospectus.

No Assurance of Regulatory Approvals or Additional Product Development

          XOMA's products are subject to rigorous preclinical and clinical
testing requirements and to approval processes by the U.S. Food and Drug
Administration (the "FDA") and similar authorities in other countries.  The
Company's products are primarily regulated on a product-by-product basis under
the U.S. Food, Drug and Cosmetic Act and Section 351(a) of the Public Health
Service Act.  Most of the Company's human therapeutic products are or will be
classified as biologic products and would be subject to regulation by the FDA
Center for Biologics Evaluation and Research.  Approval of a biologic for
commercialization requires licensure of the product and the manufacturing
facilities.

          In December 1992, XOMA submitted an investigational new drug
application ("IND") to the FDA to begin Phase I human testing of Neuprex(TM), a
recombinantly-derived fragment of human bactericidal/permeability-increasing
protein ("BPI").  In March 1993, the Company initiated human safety and
pharmacokinetic testing under the IND.  In mid-1995, the Company initiated three
clinical efficacy trials testing the Neuprex(TM) products as a treatment for
bacterial endotoxin-related conditions.  A fourth trial started in the first
quarter of 1996.  No assurance can be given, however, that product approval for
Neuprex(TM) or any other BPI product will be obtained.

          In March 1989, XOMA filed a product license application ("PLA") for
approval of E5(R), a monoclonal antibody product, for the treatment of gram-
negative sepsis.  XOMA has completed several clinical trials of E5(R), including
two randomized, double-blind, placebo-controlled, multicenter Phase III studies
involving nearly 1,300 patients.  In September 1991, an FDA advisory committee
heard E5(R) data presentations but made no recommendations regarding the 
safety or efficacy of the product.  In June 1992, the FDA informed XOMA that 
E5(R) was not approvable without further clinical testing.  In June 1993, a 
third Phase III clinical trial of the E5(R) product commenced with narrower 
entry criteria than the previous trials.  The trial is being managed and 
co-funded by Pfizer Inc. ("Pfizer").  There can be no assurance that the 
continuing








     
<PAGE>
                               -5-



trial will yield data that will result in licensure of the product in the United
States.  In October 1993, Pfizer submitted an application for approval to market
E5(R) for endotoxin reduction to regulatory authorities in Japan.  There can 
be no assurance that such application will be approved.

          During December 1991 and January 1992 the manufacturing facilities for
E5(R) were inspected for licensure by the FDA.  XOMA believes that there are no
major manufacturing issues outstanding.  Such licenses are currently pending and
will not be finalized unless and until E5(R) has been approved for sale.
Additionally,  FDA licensure of XOMA's manufacturing facilities for Neuprex(TM)
will be required prior to any commercial use or sale of Neuprex(TM).  No 
assurance can be given that approval of the manufacturing facilities for E5(R) 
or Neuprex(TM) will be obtained.

          The antibodies currently used by XOMA in its E5(R) product are derived
from ascites produced in mice by Charles River Laboratories ("CRL").  If the
Company must obtain ascites from other sources, including its own facilities or
a different facility of CRL, regulatory licensure of such other sources will be
required.  There can be no assurance that any such licensure will be obtained
without significant delay, expense or additional clinical testing.

          The FDA has substantial discretion in both the product approval
process and manufacturing facility approval process and it is not possible to
predict at what point, or whether, the FDA will be satisfied with the Company's
submissions or whether the FDA will raise questions which may be material and
delay or preclude product approval or manufacturing facility approval.  As
additional clinical data are accumulated, they will be submitted to the FDA and
may have a material impact on the FDA product approval process.

          The Company has accumulated inventories of raw material and
intermediates for E5(R).  Because the achievement, timing and terms of 
regulatory licensures and subsequent sales of pharmaceutical products are 
uncertain, there
can be no assurance that the inventories of raw materials and intermediates will
be usable.  In connection with its October 1992 restructuring, the Company
established a $6.0 million reserve for a portion of its E5(R) inventory and
recorded a $2.5 million charge to earnings for future idle capacity.  The
Company increased the reserve to $6.9 million in 1993 and to $11.1 million in
1995 to cover the entire value of the inventory.  See "-- History of Losses and
Accumulated Deficit."










     
<PAGE>
                               -6-



          Other potential XOMA products will require significant additional
development, including extensive clinical testing.  There can be no assurance
that any of the products under development by the Company will be developed
successfully, obtain the requisite regulatory approval or be successfully
manufactured or marketed.

Need for Additional Funds

          XOMA has expended and expects to continue to expend substantial funds
in connection with research and development relating to its products and
production technologies, the scale-up of its production capabilities, extensive
human clinical trials and the protection of its intellectual property.  The
Company's cash position and resulting investment income are sufficient to
finance the Company's currently anticipated needs for operating expenses,
working capital, equipment and current research projects through approximately
the end of 1997.  The Company continues to evaluate strategic alliances,
potential partnerships and financing arrangements which would further strengthen
its competitive position and provide additional funding.  However, no assurance
can be given that operations will generate meaningful funds, that additional
agreements for product development funding or strategic alliances can be
negotiated or that adequate additional financing will be available for the
Company to finance its own development on acceptable terms, if at all.  If
adequate funds are not available, the business of the Company will be materially
adversely affected.

History of Losses and Accumulated Deficit

          XOMA has experienced significant losses and, as of
March 31, 1996, had an accumulated deficit of approximately $313.5 million.

          For the year ended December 31, 1995 and the quarter ended March 31,
1996, XOMA had net losses of approximately $22.5 million, or $0.95 per share,
and $7.0 million, or $0.25 per share, respectively.  The Company expects to
incur additional losses in the future.  Its ability to achieve a profitable
level of operations is dependent in large part on obtaining regulatory approval
for its products, entering into agreements for product development and
commercialization, and making a transition to a manufacturing and marketing
company.  XOMA's ability to fund its ongoing operations is dependent on the
foregoing factors and on its ability to secure additional funds.  There can be
no assurance that the Company will ever achieve a profitable level of operations
or that








     
<PAGE>
                               -7-



cash flow from future operations will be sufficient to meet such obligations.

No Assurance of Effective Marketing

          As of the date of this Prospectus, the Company has not entered into
any marketing agreements regarding its Neuprex(TM) product.  The Company has
engaged an investment banking firm to assist it in completing one or more
strategic alliances with respect to the Neuprex(TM) product.  The Company cannot
predict whether or when any such alliance(s) will be consummated.

          The Company has entered into marketing agreements with Pfizer
regarding the E5(R) product, which provide Pfizer with exclusive rights to 
E5(R) exchange for funding of certain clinical and development activities.  
In January 1994, the territory covered by the agreements was redefined to 
include only the countries of Japan and the United States.  Pfizer also has a 
limited first right to negotiate for future XOMA products, other than BPI-
derived products, if they will be used for the treatment, cure or prevention 
of gram-negative sepsis.  The agreements can be canceled with appropriate 
notice upon reimbursement by Pfizer of certain of XOMA's research and 
development expenses.  In the third quarter of 1995, XOMA and Pfizer agreed 
to modify the funding arrangement of the current E5(R) clinical trial and 
the payment terms relating to certain patent litigation
costs (see Notes 1, 3 and 6 to the Company's Financial Statements, which are
incorporated herein by reference).  No assurance can be given that Pfizer will
be able to market the Company's products successfully.  The Company does not
currently have a marketing and sales organization for any of its products, and
no assurance can be given that XOMA will be able to develop the marketing and
sales organization necessary for the successful commercialization of its
products.

          Assuming timely regulatory approval, which cannot be assured, the
successful commercialization of XOMA's products will be dependent to a large
extent upon the marketing capabilities of its pharmaceutical partners.  The
Company believes that termination of its relationship with Pfizer could have a
material adverse effect on its future revenues and prospects.

No Assurance of Scale-up of Manufacturing Processes

          The Company has never commercially introduced any pharmaceutical
products.  In addition, there can be no assurance that the Company's, CRL's or
Pfizer's existing manufacturing facilities will receive regulatory approval in a
timely manner.  If one or








     
<PAGE>
                               -8-



more of the Company's products and the relevant manufacturing facilities were to
receive regulatory approval, no assurance can be given that these existing
manufacturing capabilities would be able to produce sufficient quantities of
such products to meet market demand.  Additionally, no assurance can be given
that if additional manufacturing facilities are needed to meet market demand,
such manufacturing facilities will be successfully obtained or that the
requisite regulatory approval for such facilities will be obtained.

No Assurance of Patent Protection/Avoidance of Patent Infringement

          Because of the length of time and the expense associated with bringing
new products through development and government approval to the marketplace, the
pharmaceutical industry has traditionally placed considerable importance on
obtaining and maintaining patent and trade secret protection for significant new
technologies, products and processes.  The Company and other biotechnology firms
hold and are in the process of applying for a number of patents in the United
States and abroad to protect their products and important processes and also
have obtained or have the right to obtain exclusive licenses to certain patents
and applications filed by others.  However, the patent position of biotechnology
companies generally is highly uncertain and no consistent policy regarding the
breadth of allowed claims has emerged from the actions of the U.S. Patent and
Trademark Office (the "Patent Office") with respect to biotechnology patents.
Legal considerations surrounding the validity of biotechnology patents continue
to be in transition, and no assurance can be given that historical legal
standards surrounding questions of validity will continue to be applied or that
current defenses as to issued biotechnology patents will in fact be considered
substantial in the future.  Accordingly, no assurance can be given as to the
degree and range of protection any patents will afford against competitors with
similar technologies, that patents will issue, that others will not obtain
patents claiming aspects similar to those covered by the Company's patent
applications or as to the extent to which the Company will be successful in
avoiding any patents granted to others.

          During the period from September 1994 to June 1996, the Patent Office
issued ten patents to the Company related to its BPI-based products, including
novel compositions, their manufacturer, formulation, assay and use.  In
addition, the Company is the exclusive licensee of three BPI-related patents
owned by NYU.  The Company and NYU have also received five more U.S. Notices of











     
<PAGE>
                               -9-



Allowance, and the Company has more than twenty pending patent applications for
its BPI-based products.

          The Company is aware of an agreement between Genentech, Inc.
("Genentech" or the "Selling Stockholder") and Incyte Pharmaceuticals Inc.
("Incyte") pursuant to which Incyte claims to hold worldwide rights to all
Incyte and Genentech technology related to BPI and through which Genentech will
receive a royalty on Incyte's BPI product sales under certain circumstances.
Between 1992 and 1994, the Patent Office issued five patents related to BPI to
Incyte (the "Incyte BPI Patents").  While the Company believes, based on the
opinion of its patent counsel, that it does not infringe any valid claims of any
of the Incyte BPI Patents, no assurance can be given that XOMA has not infringed
or will not infringe any valid claims of any of the Incyte BPI Patents.

          If certain patents issued to others are upheld or if certain patent
applications filed by others issue and are upheld, the Company may require
certain licenses from others in order to develop and commercialize certain
potential products incorporating the Company's technology.  There can be no
assurance that such licenses, if required, will be available on acceptable
terms.

          While the Company pursues patent protection, due to uncertainty as to
the future utility of patent protection for biotechnology products or processes,
the Company also relies upon trade secrets, know-how and continuing
technological advancement to develop and maintain its competitive position.  All
Company employees have signed confidentiality agreements under which they have
agreed not to use or disclose any of the Company's proprietary information.
Research and development contracts and relationships between the Company and its
scientific consultants and potential customers provide access to aspects of the
Company's know-how that are protected generally under confidentiality agreements
with the parties involved.  There can be no assurance that all confidentiality
agreements will be honored or are enforceable.

No Assurance of Product Efficacy or the Ability To Compete Successfully

          The biotechnology and pharmaceutical industries are subject to
continuous and substantial technological change.  Competition in the areas of
recombinant DNA-based and monoclonal antibody-based technologies is intense and
expected to increase in the future as a number of established biotechnology
firms and large chemical and pharmaceutical companies diversify into the field.
A number of these large pharmaceutical and chemical








     
<PAGE>
                               -10-



companies have enhanced their capabilities by entering into arrangements with,
or acquiring, biotechnology companies.  Substantially all of these companies
have significantly greater financial resources, larger research and development
and marketing staffs and larger production facilities than those of the Company.
Moreover, certain of these companies have extensive experience in undertaking
preclinical testing and human clinical trials.  These factors may enable such
companies to develop products and processes competitive with or superior to
those of the Company.  In addition, a significant amount of research in
biotechnology is being carried out in universities and other non-profit research
organizations.  These entities are becoming increasingly aware of the commercial
value of their work and may become more aggressive in seeking patent protection
and licensing arrangements.  There can be no assurance that developments by
others will not render the Company's products or technologies obsolete or
uncompetitive.

          Earlier in the 1990's, a number of corporations including Centocor,
Inc., Synergen, Inc. and Chiron, Inc. discontinued development of products (like
E5(R)) designed to treat gram-negative sepsis.  These actions may have a 
material adverse effect on the regulatory review of E5(R), and there can be 
no assurance that E5(R) will receive regulatory approval in the United States 
or that Pfizer will be able to market E5(R) effectively.  The Company 
believes that research and human testing is being conducted with other 
products, some of which are designed to treat a broader population of sepsis 
patients, including patients with gram-positive as well as gram-negative 
sepsis.  E5(R) is intended to treat only patients with severe gram-negative 
sepsis.  There can be no assurance that products currently unknown to the 
Company will not prove to be more effective than or receive regulatory 
approval prior to E5(R).

          In addition, it is possible that Incyte or some other company is
developing one or more products based on BPI, and there can be no assurance that
such product(s) will not prove to be more effective than Neuprex(TM).

No Assurance of Supply of Monoclonal Antibodies

          XOMA obtains the unpurified ascites containing the monoclonal
antibodies used in its E5(R) product from a single supplier, CRL, which has
multiple manufacturing sites.  XOMA and CRL entered into a supply agreement in
1989 and renewed the agreement in 1991, committing CRL to supply and the Company
to purchase XOMA's anticipated ascites needs for five years after FDA licensure
of E5(R).  Among the requirements for FDA licensure of E5(R)









     
<PAGE>
                               -11-



is that the CRL manufacturing facilities be licensed by the FDA.  If the Company
must obtain ascites from other sources, including its own facilities or a
different facility of the same supplier, regulatory approval of such other
sources will be required.  Although the Company believes that it currently has
sufficient quantities of ascites for product launch and the first few years of
sales, any significant future interruption in supply could materially and
adversely affect the Company's business relating to E5(R).

Potential Impact of Healthcare Reform

          The successful commercialization of the Company's products will depend
upon, among other things, the Company's marketing arrangements for its products.
The Company's ability to enter into marketing arrangements on acceptable terms
and/or the terms of its existing arrangements could be materially adversely
affected if legislation were to be enacted or regulations adopted which mandates
or otherwise results in the reduction or containment of the cost of phar-
maceutical products to consumers.  In addition, if legislation were to be
enacted or regulations adopted which mandates or otherwise results in the
reduction of pharmaceutical product manufacturer's prices, the Company's
business could be materially adversely affected.

Uncertainties in Attracting and Retaining Qualified Personnel

          The Company's success in developing marketable products and achieving
a competitive position will depend, in part, on its ability to attract and
retain qualified scientific and management personnel.  Competition for such
personnel is intense, and no assurances can be given that the Company will be
able to attract or retain such personnel.  The loss of a significant group of
key personnel would adversely affect the Company's product development efforts.

Risk of Product Liability Claims

          The testing and marketing of medical products entails an inherent risk
of allegations of product liability.  The Company believes it currently has
adequate levels of insurance for its clinical trials.  The Company will seek to
obtain additional insurance, if needed, if and when the Company's products are
commercialized; however, there can be no assurance that adequate insurance
coverage will be available or be available at acceptable costs or that a product
liability claim would not materially










     
<PAGE>
                               -12-



adversely affect the business or financial condition of the Company.

Certain Provisions Relating to Changes in Control

          The Stockholder Rights Agreement, dated as of October 27, 1993 (the
"Rights Agreement"), between the Company and First Interstate Bank of
California, as Rights Agent, and the Company's Amended and Restated By-Laws
contain provisions that may have the effect of making more difficult an
acquisition of control of the Company that has not been approved by the
Company's Board of Directors.  See "Description of Equity Securities -- Certain
Provisions Relating to Changes in Control of the Company."

Volatility of Stock Price

          The market prices for securities of biotechnology companies, including
XOMA, have been highly volatile.  See "Price Range of Common Stock and Dividend
Information." Announcements regarding the results of regulatory approval
filings, clinical trials or other testing, technological innovations or new
commercial products by XOMA or its competitors, government regulations,
developments concerning proprietary rights or public concern as to safety of
biotechnology have historically had, and are expected to continue to have, a
significant impact on the market price of XOMA's Common Stock.

                                  THE COMPANY

          The Company is a biopharmaceutical company developing products for the
treatment of infectious diseases and major complications due to infections,
traumatic injury and surgery.  The Company's current product development
programs include:

     -    Neuprex(TM), a recombinantly-derived fragment of BPI and
          XOMA's lead BPI product, which is currently in efficacy
          clinical trials for four different indications.

     -    I-PREX(TM), a proprietary topical formulation of BPI for
          the treatment of ophthalmic disorders, which is undergo-
          ing preclinical testing as a treatment for corneal
          ulcerations and transplants.

     -    Mycoprex(TM), a potent fungicidal peptide compound derived
          from BPI that is currently in preclinical product
          development.







     
<PAGE>
                               -13-



     -    E5(R), XOMA's monoclonal antibody product, which is in a
          Phase III trial in the United States as a treatment for
          gram-negative sepsis and has been submitted for approval
          in Japan as a treatment for endotoxemia.

          The Company's cash position and resulting investment
income are sufficient to finance the Company's currently antici-
pated needs for operating expenses, working capital, equipment and
current research projects through approximately the end of 1997.
The Company continues to evaluate strategic alliances, potential
partnerships, and financing arrangements which would further
strengthen its competitive position and provide additional fund-
ing.  The Company has engaged an investment banking firm to assist
in completing one or more strategic alliances with respect to the
Neuprex(TM) product.  The Company cannot predict whether or when any
such alliance(s) will be consummated or whether additional funding
will be available when required.

          On May 15, 1996, the Company announced the granting of
an exclusive license to Genentech, including a sublicense to IDEC
Pharmaceuticals Corporation, to intellectual property covering the
therapeutic use of chimeric IgG1 antibodies specific for the CD20
antigen on the surface of human B-cells.  The Company received an
initial cash payment of $3 million and will receive royalties on
the sale of products employing the anti-CD20 technology that are
sold in the United States and in other countries where the Company
holds relevant patents.

          Certain statements contained herein that are not related
to historical facts may contain "forward looking" information, as
that term is defined in the Private Securities Litigation Reform
Act of 1995.  Such statements are based on the Company's current
beliefs as to the outcome and timing of future events, and actual
results may differ materially from those projected or implied in
the forward looking statements.  Further, certain forward looking
statements are based upon assumptions of future events which may
not prove to be accurate.  The forward looking statements involve
risks and uncertainties including, but not limited to, the risks
and uncertainties referred to under "Risk Factors" and elsewhere
herein and in other of the Company's Securities and Exchange Com-
mission filings.








     
<PAGE>
                               -14-



       PRICE RANGE OF COMMON STOCK AND DIVIDEND INFORMATION

          The Company's Common Stock trades on the Nasdaq National
Market under the symbol "XOMA."  The following table sets forth
the quarterly range of high and low reported sale prices of the
Company's Common Stock on the Nasdaq National Market for the peri-
ods indicated.

                                            High       Low
                                            ----       ---
     1994:

          First Quarter ...............   $6 1/4     $3 3/4
          Second Quarter ..............    4 1/4      2 1/2
          Third Quarter ...............    3 5/8      2 1/4
          Fourth Quarter ..............    4 1/8      2 3/16

     1995:

          First Quarter ...............    $3 1/16   $1 1/8
          Second Quarter ..............     2 7/8     1 9/32
          Third Quarter ...............     4 1/4     1 11/16
          Fourth Quarter ..............     4 1/8     1 7/8

     1996:

          First Quarter ...............     5 3/4     3 3/8
          Second Quarter
          (through June 27, 1996) .....     8 1/8     3 7/8


          On June 27, 1996 the last reported bid price of the Com-
mon Stock as reported on the Nasdaq National Market was $6.50 per
share.  On June 27, 1996, there were approximately 2,700 record
holders of XOMA's Common Stock.

          The Company has not paid cash dividends on its Common
Stock.  The Company currently intends to retain earnings for use
in the development and expansion of its business and, therefore,
does not anticipate paying cash dividends on its Common Stock in
the foreseeable future.








     
<PAGE>
                              -15-



                       SELLING STOCKHOLDER

          The following table sets forth certain information
regarding the beneficial ownership of Common Stock by the Selling
Stockholder as of May 31, 1996, and the number of shares of Com-
mon Stock covered by this Prospectus.

                                 Beneficial Ownership       Number of Shares
Name and Address of              of Common Stock prior      of Common Stock
Selling Stockholder              to the Offering            Registered Hereby
- - --------------------             ---------------------      -----------------

                                 Number of    Percent 
                                 Shares       of Class
                                 ---------    --------

Genentech, Inc.
 460 Point San Bruno Boulevard
 South San Francisco, CA  94080  1,500,000(1)   4.5%        1,500,000


(1)  Does not include an indeterminate number of shares of Common
     Stock issuable upon conversion of the $5 million aggregate
     principal amount of the convertible note outstanding under
     the Convertible Subordinated Note Agreement dated as of
     April 22, 1996, as amended, between the Company and
     Genentech (the "Convertible Note") into shares of the Compa-
     ny's Convertible Preferred Stock, Series E ("Series E Pre-
     ferred Stock"), at the conversion price of $10,000 per
     share, and the further conversion of such shares of Series E
     Preferred Stock into shares of Common Stock.  See "Descrip-
     tion of Equity Securities - Series E Preferred Stock."  The
     Convertible Note and the 1,500,000 shares of Common Stock
     being registered hereby were issued to Genentech in April
     1996 in a transaction exempt from registration under the
     Securities Act pursuant Section 4(2) thereof (the "Private
     Placement").  The collaboration agreement to which the Pri-
     vate Placement relates is described in the Company's Current
     Report on Form 8-K, dated April 22, 1996, filed with the SEC
     and incorporated herein by reference and has been filed with
     the SEC as an exhibit to the Registration Statement of which
     this Prospectus is a part.












     
<PAGE>
                             -16-



               DESCRIPTION OF EQUITY SECURITIES

          The authorized capital stock of the Company consists
of 70,000,000 shares of Common Stock, $.0005 par value, of
which 33,432,932 shares were outstanding on June 27, 1996, and
1,500,000 shares of preferred stock, $.05 par value, of which
650,000 have been designated Series A Cumulative Preferred
Stock (the "Series A Preferred Stock"), of which none were out-
standing on such date, 5,000 have been designated Non-Voting
Cumulative Convertible Preferred Stock, Series D (the "Series D
Preferred Stock"), of which 4,100 were outstanding on such
date, and 7,500 have been designated Convertible Preferred
Stock, Series E (the "Series E Preferred Stock"), of which none
were outstanding on such date.

Common Stock

          Holders of shares of Common Stock are entitled to one
vote per share on all matters to be voted on by stockholders.
The holders of Common Stock are entitled to receive such divi-
dends, if any, as may be declared from time to time by the Com-
pany's Board of Directors out of funds legally available there-
for.  Upon liquidation or dissolution of the Company, the hold-
ers of the Common Stock are entitled to share ratably in the
distribution of assets, subject to the rights of the holders of
the Series D Preferred Stock or any other series of preferred
stock that may then be outstanding.  There are no redemption or
sinking fund provisions with respect to the Common Stock.  All
of the outstanding shares of Common Stock are validly issued,
fully paid and nonassessable.

Preferred Stock Purchase Rights

          On October 27, 1993, the Board of Directors of the
Company declared a dividend distribution of one Preferred Stock
Purchase Right (a "Right") for each outstanding share of Common
Stock.  Each Right entitles the holder to purchase from the
Company a unit consisting of one one-hundredth of a share (a
"Unit") of Series A Preferred Stock at a cash exercise price of
$30.00 per Unit, subject to adjustment.

          The Rights are attached to all outstanding shares of
Common Stock, including the shares of Common Stock offered
hereby.  The Rights will separate from the Common Stock and
will be distributed to holders of Common Stock upon the ear-
liest of (i) ten business days after the first public announce-
ment that a person or group of affiliated or associated persons


     
<PAGE>
                             -17-



(an "Acquiring Person") has acquired beneficial ownership of
20% or more of the Common Stock then outstanding (the date of
said announcement being referred to as the "Stock Acquisition
Date"), (ii) ten business days following the commencement of a
tender offer or exchange offer that would result in a person or
group of persons becoming an Acquiring Person or (iii) the dec-
laration by the Board of Directors of the Company that any per-
son is an "Adverse Person" (the earliest of such dates, the
"Distribution Date").

          The Board of Directors of the Company may generally
declare a person to be an Adverse Person after a declaration
that such person has become the beneficial owner of 10% or more
of the outstanding shares of Common Stock and a determination
that (a) such beneficial ownership by such person is intended
to cause or is reasonably likely to cause the Company to repur-
chase the Common Stock owned by such Person or to cause the
Company to enter into other transactions not in the best
long-term interests of the Company or (b) such beneficial own-
ership is reasonably likely to cause a material adverse impact
on the business or prospects of the Company.  The Rights are
not exercisable until the Distribution Date and will expire on
December 31, 2002, unless previously redeemed or exchanged by
the Company.

          In the event that a person becomes an Acquiring Per-
son or the Board of Directors determines that a person is an
Adverse Person, each holder of a Right will thereafter have the
right (a "Subscription Right") to receive upon exercise that
number of Units of Series A Preferred Stock having a market
value of two times the exercise price of the Rights.  In the
event that, at any time following the Stock Acquisition Date,
(i) the Company consolidates with, or merges with and into, any
person, and the Company is not the surviving corporation;
(ii) any person consolidates with the Company, or merges with
and into the Company and the Company is the continuing or sur-
viving corporation of such merger and, in connection with such
merger, all or part of the shares of Common Stock are changed
into or exchanged for other securities of any other person or
cash or any other property, or (iii) 50% or more of the Compa-
ny's assets are sold or otherwise transferred, each holder of a
Right shall thereafter have the right (a "Merger Right") to
receive, upon exercise, common stock of the acquiring company
having a market value equal to two times the exercise price of
the Rights.  Rights that are beneficially owned by an Acquiring
or Adverse Person may, under certain circumstances, become null
and void.


     
<PAGE>
                             -18-



          At any time after a person becomes an Acquiring Per-
son or the Board of Directors of the Company determines that a
person is an Adverse Person, the Board of Directors of the Com-
pany may exchange all or any part of the then outstanding and
exercisable Rights for shares of Common Stock or Units of
Series A Preferred Stock at an exchange ratio of one share of
Common Stock or one Unit of Series A Preferred Stock per Right.
Notwithstanding the foregoing, the Board of Directors of the
Company generally will not be empowered to effect such exchange
at any time after any person becomes the beneficial owner of
50% or more of the Common Stock then outstanding.

          The Rights may be redeemed in whole, but not in part,
at a price of $.001 per Right by the Board of Directors of the
Company at any time prior to the date on which a person is
declared to be an Adverse Person, the tenth business day after
the Stock Acquisition Date, the occurrence of an event giving
rise to the Merger Right or the expiration date of the Rights
Agreement.

The Series A Preferred Stock

          There are currently no shares of Series A Preferred
Stock outstanding.  Pursuant to the Certificate of Designation
relating to the Series A Preferred Stock, subject to the rights
of holders of any shares of any series of preferred stock rank-
ing prior and superior (such as the Series D Preferred Stock),
the holders of Series A Preferred Stock are entitled to
receive, when, as and if declared by the Board of Directors of
the Company out of funds legally available for the purpose,
quarterly dividends payable in cash on the first day of March,
June, September and December in each year (a "Dividend Payment
Date"), commencing on the first Dividend Payment Date after the
first issuance of a share or fraction of a share of Series A
Preferred Stock, in an amount per share equal to the greater of
(a) $1.00 or (b) 100 times the aggregate per share amount of
all cash dividends, plus 100 times the aggregate per share
amount of all non-cash dividends or other distributions, other
than a dividend payable in shares of Common Stock, declared on
the Common Stock since the immediately preceding Dividend Pay-
ment Date, or, with respect to the first Dividend Payment Date,
since the first issuance of Series A Preferred Stock.

          In addition to any other voting rights required by
law, holders of Series A Preferred Stock shall have the right
to vote on all matters submitted to a vote of stockholders of
the Company with each share of Series A Preferred Stock


     
<PAGE>
                             -19-



entitled to 100 votes.  Except as otherwise provided by law,
holders of Series A Preferred Stock and holders of Common Stock
shall vote together as one class on all matters submitted to a
vote of stockholders of the Company.

          Unless otherwise provided in a Certificate of Desig-
nation relating to a subsequently designated series of pre-
ferred stock of the Company, the Series A Preferred Stock shall
rank junior to any other series of preferred stock as to the
payment of dividends and distribution of assets on liquidation,
dissolution or winding-up and shall rank senior to the Common
Stock.  Upon any liquidation, dissolution or winding-up of the
Company, no distributions shall be made to holders of shares of
stock ranking junior to the Series A Preferred Stock unless,
prior thereto, the holders of Series A Preferred Stock shall
have received an amount equal to accrued and unpaid dividends
and distributions, whether or not declared, to the date of such
payment, plus an amount equal to the greater of (1) $100.00 per
share or (2) an aggregate amount per share equal to 100 times
the aggregate amount to be distributed per share to holders of
Common Stock or to the holders of stock ranking on parity with
the Series A Preferred Stock, except distributions made ratably
on the Series A Preferred Stock and all other such parity stock
in proportion to the total amount to which the holders of all
such shares are entitled upon such liquidation, dissolution or
winding-up.

          If the Company shall enter into any consolidation,
merger, combination or other transaction in which shares of
Common Stock are exchanged for or changed into cash, other
securities and/or any other property, then any shares of
Series A Preferred Stock outstanding shall at the same time be
similarly exchanged or changed in an amount per share equal to
100 times the aggregate amount of cash, securities and/or other
property, as the case may be, into which or for which each
share of Common Stock is changed or exchanged.

          The shares of Series A Preferred Stock shall not be
redeemable.

The Series B Preferred Stock

          The 18,775 shares of Senior Convertible Preferred
Stock, Series B, issued by the Company in a private placement
consummated in December 1993 in reliance upon the exemption
contained in Section 4(2) of the Securities Act, have been con-
verted into an aggregate of 3,751,454 shares of Common Stock.  


     
<PAGE>
                             -20-



The Series C Preferred Stock

          The 4,799 shares of Convertible Preferred Stock,
Series C, issued by the Company in an offering made to foreign
investors in reliance on Regulation S under the Securities Act
in August 1995, have been converted into an aggregate of
2,728,190 shares of Common Stock.

The Series D Preferred Stock

          The 4,100 outstanding shares of Series D Preferred
Stock were issued by the Company to GFL-B in an offering of
Series D Preferred Stock and Common Stock exempt from the reg-
istration requirements of the Securities Act pursuant to Regu-
lation D thereunder in March 1996.  Pursuant to the Certificate
of Designations relating to the Series D Preferred Stock, the
holders thereof are entitled to receive, when, as and if
declared by the Board of Directors of the Company, out of funds
legally available therefor, dividends at an annual rate of
$40.00 per share, payable semi-annually in arrears, commencing
June 30, 1996.  Dividends are payable, at the option of the
Company, in cash, in Common Stock or any combination of cash
and Common Stock.  In addition, the Company may elect not to
declare or make payment of any dividend, in which event the
accrued and unpaid dividends shall be taken into account at the
time of conversion, as described below.

          The Series D Preferred Stock ranks senior with
respect to rights on liquidation, winding-up and dissolution of
the Company to all classes of Common Stock.  Upon any voluntary
or involuntary liquidation, dissolution or winding-up of the
Company, holders of Series D Preferred Stock will be entitled
to receive $1,000 per share, plus accrued and unpaid dividends,
before any distribution is made on the Common Stock or any pre-
ferred stock of the Company ranking junior as to liquidation
rights to the Series D Preferred Stock, but only after any pay-
ments with respect to liquidation preference of preferred stock
ranking senior as to liquidation rights to the Series D Pre-
ferred Stock are fully met.  Except as may be required by law
and except with respect to certain actions which may adversely
affect the holders of Series D Preferred Stock, the holders of
Series D Preferred Stock are not entitled to vote on any matter
submitted to a vote of stockholders of the Company.

          The holders of Series D Preferred Stock have the
right to convert shares of Series D Preferred Stock into Common
Stock at a conversion price equal to 80% of the then current


     
<PAGE>
                             -21-



market price of the Common Stock on or after the 75th day fol-
lowing the first date of original issuance of any shares of
Series D Preferred Stock; provided that in no event shall GFL-B
or GFL Performance be entitled to convert any shares of Series
D Preferred Stock if the issuance of shares of Common Stock
upon a proposed conversion, when the shares to be so issued are
counted together with other shares of Common Stock beneficially
owned by GFL-B, GFL Performance or any associate or affiliate
of or adviser to GFL-B or GFL Performance (collectively, the
"GFL Persons") (other than shares so owned through ownership of
Series D Preferred Stock), would result in a GFL Person benefi-
cially owning more than 4.9% of the outstanding shares of Com-
mon Stock; and provided, further, that in the event that for
any 15 trading days during a 20 consecutive trading day period
the conversion of all the outstanding shares of Series D Pre-
ferred Stock upon surrender thereof would require the issuance
of more than approximately 4.5 million shares of Common Stock
in the aggregate with respect to all conversions of Series D
Preferred Stock, the Company will have the option to either
redeem the Series D Preferred Stock at a redemption price of
$1,250 per share or, with stockholder approval, convert such
Series D Preferred Stock into shares of Common Stock.  In addi-
tion, subject to the proviso of the immediately preceding sen-
tence, the Corporation has the right, so long as it is in mate-
rial compliance with its obligations to the holders of the
Series D Preferred Stock, exercisable at any time on or after
January 15, 1998, to require the holders thereof to convert
their shares of Series D Preferred Stock into Common Stock at a
conversion price equal to 80% of the then current market price
of the Common Stock.

          Each share of Series D Preferred Stock may be
redeemed at the option of the Company at any time on or after
October 1, 1996 at a redemption price of $1,250 per share. 

The Series E Preferred Stock

          There are currently no shares of Series E Preferred
Stock outstanding.  The 7,500 shares of Series E Preferred
Stock have been designated by the Company for issuance upon
conversion of the convertible subordinated loans to the Company
made and to be made by Genentech in connection with the funding
of the Company's development costs for anti-CD11a through 1998.
Such loans are and will be convertible into Series E Preferred
Stock upon the occurrence of certain events relating to certain
regulatory approvals, payment defaults, prepayments and other
circumstances.  Pursuant to the Certificate of Designation


     
<PAGE>
                             -22-



relating to the Series E Preferred Stock, the holders of shares
of Series E Preferred Stock will not be entitled to receive any
dividends on shares of the Series E Preferred Stock.

          The Series E Preferred Stock will rank senior with
respect to rights on liquidation, winding-up and dissolution of
the Company to all classes of Common Stock.  Upon any voluntary
or involuntary liquidation, dissolution or winding-up of the
Company, holders of Series E Preferred Stock will be entitled
to receive $10,000 per share of Series E Preferred Stock before
any distribution is made on the Common Stock.  The holders of
shares of Series E Preferred Stock will have no voting rights,
except as required under the General Corporation Law of the
State of Delaware.

          The holders of Series E Preferred Stock will have the
right to convert shares of Series E Preferred Stock into shares
of Common Stock at a conversion price equal to the current mar-
ket price of the Common Stock (determined as provided below).
The current market price will be determined (a) for shares of
Series E Preferred Stock issued in connection with a conversion
of one or more of the convertible subordinated loans upon cer-
tain regulatory approvals, payment defaults or in certain other
circumstances, as of the first date on which such a conversion
occurs, and (b) for shares of Series E Preferred Stock issued
in connection with certain prepayments of one or more of the
convertible subordinated loans or a conversion thereof in cer-
tain other circumstances, as of the date of the issuance of
such shares of Series E Preferred Stock.

          The Series E Preferred Stock will be automatically
converted into Common Stock at its then effective conversion
rate immediately upon the transfer by the initial holder to any
third party which is not an affiliate of such holder.

          The Company will have the right, at any time and from
time to time, to redeem any or all shares of Series E Preferred
Stock for cash in an amount equal to the conversion price mul-
tiplied by the number of shares of Common Stock into which each
such share of Series E Preferred Stock would then be
convertible.

Certain Provisions Relating to Changes in Control of the
Company

          Certain provisions of the Amended and Restated
By-Laws of the Company (the "By-Laws") and the Rights


     
<PAGE>
                             -23-



(summarized above) may delay, defer or prevent a change in con-
trol of the Company that a stockholder might consider to be in
his or her best interest, including those applicable to a
change in control of the Company that might result in a premium
over the market price for the shares of Common Stock held by
stockholders.

          Special Meeting of Stockholders.  The By-Laws provide
that meetings of stockholders of the Company may be called only
by the Chief Executive Officer or the Board of Directors of the
Company.  This provision may make it more difficult for stock-
holders to take action opposed by management or the Board of
Directors of the Company.

          Advance Notice Requirements for Stockholder Proposals
and Director Nominations.  The By-Laws provide that stockhold-
ers seeking to bring business before an annual meeting of
stockholders or to nominate candidates for election as direc-
tors at an annual meeting of stockholders, must provide timely
notice thereof in writing.  To be timely, a stockholder's
notice must be received by the Secretary of the Company not
less than sixty nor more than ninety days prior to the first
anniversary of the preceding year's annual meeting, or in the
case of an annual meeting that is called for a date that is
more than thirty days or delayed by more than sixty days from
such anniversary, notice by the stockholder to be timely must
be so received not earlier than the ninetieth day prior to such
annual meeting and not later than the close of business on the
later of (1) the sixtieth day prior to such annual meeting or
(2) the tenth day following the day on which such notice of the
date of the annual meeting was mailed or publicly disclosed.
These provisions may preclude some stockholders from bringing
matters before an annual meeting of stockholders or making nom-
inations for directors at an annual meeting of stockholders.

          Preferred Stock Purchase Rights.  The provisions of
the Rights and the Series A Preferred Stock may make it more
difficult or more costly for a person or group of persons to
acquire control of the Company in a transaction opposed by the
Board of Directors of the Company.  See "-- Preferred Stock
Purchase Rights" and "-- The Series A Preferred Stock."

Transfer Agent and Registrar

          First Interstate Bank of California is the transfer
agent and registrar of the Common Stock.



     
<PAGE>
                             -24-



                     PLAN OF DISTRIBUTION

          Any or all of the Common Stock being registered
hereby may be sold from time to time to purchasers directly by
the Selling Stockholder.  Alternatively, the Selling Stock-
holder may from time to time offer the Common Stock through
underwriters, dealers or agents who may receive compensation in
the form of underwriting discounts, concessions or commissions
from the Selling Stockholder and/or the purchasers of Common
Stock for whom they may act as agent.  The Selling Stockholder,
and any such underwriters, dealers or agents that participate
in the distribution of Common Stock, may be deemed to be under-
writers, and any profit on the sale of the Common Stock by them
and any discounts, commissions or concessions received by them
may be deemed to be underwriting discounts and commissions
under the Securities Act.  At the time a particular offer of
Common Stock is made, to the extent required, a supplement to
this Prospectus will be distributed which will set forth the
terms of the offering, including the name or names of any
underwriters, dealers or agents, the purchase price paid by any
underwriter for Common Stock purchased from the Selling Stock-
holder and any discounts, commissions and other items consti-
tuting compensation from the Selling Stockholder and any dis-
counts, commissions or concessions allowed or reallowed or paid
to dealers, including the proposed selling price to the public.
The Company will receive no proceeds from the sale by the Sell-
ing Stockholder of the Common Stock offered hereby.

          In connection with distributions of the Common Stock,
the Selling Stockholder may enter into hedging transactions
with broker-dealers and the broker-dealers may engage in short
sales of the Common Stock in the course of hedging the posi-
tions they assume with the Selling Stockholder.  The Selling
Stockholder also may sell the Common Stock short and deliver
the Common Stock to close out such short positions.  The Sell-
ing Stockholder also may enter into option or other transac-
tions with broker-dealers that involve the delivery of the Com-
mon Stock to the broker-dealers, which may then resell or
otherwise transfer such Common Stock.  The Selling Stockholder
also may loan or pledge the Common Stock to a broker-dealer and
the broker-dealer may sell the Common Stock so loaned or upon a
default may sell or otherwise transfer the pledged Common
Stock.

          The shares of Common Stock covered by this Prospectus
are shares of Common Stock purchased by Genentech in the Pri-
vate Placement.


     
<PAGE>
                             -25-



          All Registration Expenses incurred in connection with
the registration of the Common Stock to which this Prospectus
relates, estimated to be approximately $110,000, will be borne
by the Company.  As and when the Company is required to update
this Prospectus, it may incur additional expenses in excess of
this estimated amount.  "Registration Expenses" means all
expenses incurred by the Company in complying with the regis-
tration rights granted to the Selling Stockholder pursuant to
which the Registration Statement to which this Prospectus
relates has been filed.

          The Company has agreed to indemnify the Selling
Stockholder against certain liabilities, including certain lia-
bilities under the Securities Act, or to contribute to payments
which the Selling Stockholder may be required to make in
respect thereof.

                        LEGAL OPINIONS

          The validity of the shares of Common Stock to which
this Prospectus relates has been passed upon for the Company by
Cahill Gordon & Reindel, a partnership including a professional
corporation, located in New York, New York.  Opinions regarding
certain legal matters with respect to patents and patent law
have been provided to the Company by Marshall, O'Toole,
Gerstein, Murray & Borun, located in Chicago, Illinois.

                            EXPERTS

          The financial statements of XOMA incorporated by ref-
erence in this Prospectus and elsewhere in the Registration
Statement have been audited by Arthur Andersen LLP, independent
public accountants, as indicated in their report with respect
thereto, and are incorporated by reference herein in reliance
upon the authority of said firm as experts in giving said
report.













     
<PAGE>
=====================================   ===================================
      No dealer, salesman or other per-
son has been authorized to give
any information or to make representa-
tions other than those contained in
this Prospectus, and, if given or                  1,500,000 Shares
made, such information or representa- 
tions must not be relied upon as having            XOMA Corporation
been authorized by the Company or the
Selling Stockholder.  Neither the                    Common Stock
delivery of this Prospectus nor any
sale made hereunder shall, under any
circumstances, create an implication
that the information herein is correct
as of any time subsequent to its date.               -------------
This Prospectus does not constitute an
offer or solicitation by anyone in any               PROSPECTUS 
jurisdiction in which such offer
or solicitation is not authorized or in              -------------
which the person making such offer or
solicitation is not qualified to do so
or to anyone to whom it is unlawful to
make such offer or solicitation.

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

       TABLE OF CONTENTS
                                 Page

Available Information...........    
Information Incorporated
  by Reference..................    
Risk Factors....................    
The Company.....................   
Price Range of Common Stock
  and Dividend Information......   
Selling Stockholder.............  
Description of Equity
  Securities....................   
Plan of Distribution............   
Legal Opinions..................   
Experts.........................   
                                                           , 1996
=====================================   ===================================






     
<PAGE>
                            PART II

            INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14.  Other Expenses of Issuance and Distribution

          The estimated expenses in connection with this offer-
ing are as follows:

                                               Amount
                                             to be Paid

SEC registration fee ......................  $  3,378
Nasdaq fee ................................    17,500
Legal fees and expenses (including             
  Blue Sky fees and expenses) .............    75,000
Accounting fees and expenses ..............     3,000
Miscellaneous .............................    11,122
                                             --------
Total .....................................  $110,000
                                             --------


Item 15.  Indemnification of Directors and Officers

          The Delaware General Corporation Law provides for
indemnification of directors, officers, employees and agents,
subject to certain limitations (Del. Code, Title 8 Sec. 145).
Article VII of the Company's Bylaws provides that expenses
incurred by an officer or director of the Company in defending
a civil or criminal action, suit or proceeding shall be paid by
the Company in advance of a final disposition of the action,
suit or proceeding upon receipt by the Company of an undertak-
ing by the officer or director that he or she will repay such
expenses if it is ultimately determined that he or she is not
entitled to indemnification under the Delaware General Corpora-
tion Law.

          As permitted by Section 102 of the Delaware General
Corporation Law, the Company's Certificate of Incorporation
contains provisions eliminating a director's personal liability
for monetary damages to the Company and its stockholders aris-
ing from a breach of a director's fiduciary duty except for
liability under Section 174 of the Delaware General Corporation
Law or liability for any breach of the director's duty of loy-
alty to the Company or its stockholders, for acts or omissions
not in good faith or which involve intentional misconduct or a
knowing violation of law or for any transaction by which the
director derived an improper personal benefit.  The Company has
also entered into indemnification agreements with its directors



                             II-1
     
<PAGE>
and officers providing for indemnification and advancements of
expenses to the fullest extent permitted under Delaware law.

Item 16.  Exhibits and Financial Statement Schedules

(a)  Exhibits

     Exhibit
     Number
     -------
     4.1      Restated Certificate of Incorporation(1)

     4.2      Certificate of Amendment of Restated Certificate
              of Incorporation

     4.3      Amended and Restated By-Laws(2)

     4.4      Stockholder Rights Agreement dated October 27,
              1993 by and between the Company and First Inter-
              state Bank of California as Rights Agent(3)

     4.5      Certificate of Designations of Non-Voting Cumula-
              tive Convertible Preferred Stock, Series D(4)

     4.6      Certificate of Designation of Convertible Pre-
              ferred Stock, Series E(4)

     4.7      Amended Certificate of Designation of Convertible
              Preferred Stock, Series E

     5.1      Opinion of Cahill Gordon & Reindel

     10.1     Collaboration Agreement, dated as of April 22,
              1996, between XOMA Corporation and Genentech,
              Inc. (with certain confidential information
              omitted)

     10.2     Common Stock and Convertible Note Purchase Agree-
              ment, dated as of April 22, 1996, between XOMA
              Corporation and Genentech, Inc. (with certain
              confidential information omitted)

     10.3     Convertible Subordinated Note Agreement, dated
              April 22, 1996, between XOMA Corporation and
              Genentech (with certain confidential information
              omitted)





                             II-2
     
<PAGE>
     10.4     Amendment to Convertible Subordinated Note Agree-
              ment, dated June 13, 1996, between XOMA Corpora-
              tion and Genentech, Inc.

     23.1     Consent of Arthur Andersen LLP

     23.2     Consent of Marshall, O'Toole, Gerstein, Murray &
              Borun











































                             II-3
     
<PAGE>
     23.3     Consent of Cahill Gordon & Reindel (included in
              Exhibit 5.1)

     24.1     Power of Attorney (included on the signature page
              hereto)

____________________

(1)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 33-59379).

(2)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 33-74982).

(3)  Incorporated by reference to the Company's Current Report
     on Form 8-K dated October 27, 1993.

(4)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 333-2493).

Item 17.  Undertakings

          The undersigned registrant hereby undertakes:

          (1)  To file, during any period in which offers or
sales are being made, a post-effective amendment to this regis-
tration statement:

          (i)  To include any prospectus required by Section
     10(a)(3) of the Securities Act of 1933;

         (ii)  To reflect in the prospectus any facts or events
     arising after the effective date of the registration
     statement (or the most recent post-effective amendment
     thereof) which, individually or in the aggregate, repre-
     sent a fundamental change in the information set forth in
     the registration statement;

        (iii)  To include any material information with respect
     to the plan of distribution not previously disclosed in
     the registration statement or any material change to such
     information in the registration statement;

          Provided, however, that paragraphs (1)(i) and (1)(ii)
do not apply if the registration statement is on Form S-3 or
Form S-8, and the information required to be included in the
post-effective amendment by those paragraphs is contained in
periodic reports filed by the registrant pursuant to Section 13



                             II-4
     
<PAGE>
or Section 15(d) of the Securities Exchange Act of 1934 that
are incorporated by reference in the registration statement.

          (2)  That, for the purpose of determining any lia-
bility under the Securities Act of 1933, each post-effective
amendment shall be deemed to be a new registration statement
relating to the securities offered herein, and the offering of
such securities at that time shall be deemed to be the initial
bona fide offering thereof.

          (3)  To remove from registration by means of a post-
effective amendment any of the securities being registered
which remain unsold at the termination of the offering.

          The undersigned registrant hereby undertakes that,
for purposes of determining any liability under the Securities
Act of 1933, each filing of the registrant's annual report pur-
suant to Section 13(a) or Section 15(d) of the Securities
Exchange Act of 1934 that is incorporated by reference in the
registration statement shall be deemed to be a new registration
statement relating to the securities offered herein, and the
offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

          Insofar as indemnification for liabilities arising
under the Securities Act of 1933 may be permitted to directors,
officers and controlling persons of the registrant pursuant to
the foregoing provisions, or otherwise, the registrant has been
advised that in the opinion of the Securities and Exchange Com-
mission such indemnification is against public policy as
expressed in the Securities Act of 1933 and is, therefore,
unenforceable.  In the event that a claim for indemnification
against such liabilities (other than the payment by the regis-
trant of expenses incurred or paid by a director, officer or
controlling person of the registrant in the successful defense
of any action, suit or proceeding) is asserted by such direc-
tor, officer or controlling person in connection with the secu-
rities being registered, the registrant will, unless in the
opinion of counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the
question whether such indemnification by it is against public
policy as expressed in the Securities Act of 1933 and will be
governed by the final adjudication of such issue.

          The undersigned registrant hereby undertakes to
deliver or cause to be delivered with the prospectus, to each
person to whom the prospectus is sent or given, the latest
annual report to security holders that is incorporated by ref-
erence in the prospectus and furnished pursuant to and meeting


                             II-5
     
<PAGE>
the requirements of Rule 14a-3 or Rule 14c-3 under the Securi-
ties Exchange Act of 1934; and, where interim financial infor-
mation required to be presented by Article 3 of Regulation S-X
is not set forth in the prospectus, to deliver, or cause to be
delivered to each person to whom the prospectus is sent or
given, the latest quarterly report that is specifically incor-
porated by reference in the prospectus to provide such interim
financial information.











































                             II-6
     
<PAGE>
                          SIGNATURES


          Pursuant to the requirements of the Securities Act of
1933, the Registrant certifies that it has reasonable grounds
to believe that it meets all of the requirements for filing on
Form S-3 and has duly caused this Amendment to be signed on its
behalf by the undersigned, thereunto duly authorized, in the
City of Berkeley, State of California, on June 28, 1996.

                                   XOMA CORPORATION



                                   By: /s/John L. Castello
                                       ------------------------
                                       John L. Castello
                                       Chairman of the Board,
                                       President and 
                                       Chief Executive Officer


                       POWER OF ATTORNEY

          KNOW ALL PERSONS BY THESE PRESENTS, that each person
whose signature appears below constitutes and appoints John L.
Castello and Christopher J. Margolin, and each of them, as his
true and lawful attorneys-in-fact and agents, with full power
of substitution and resubstitution, for him and in his name,
place and stead, in any and all capacities, to sign any and all
amendments (including post-effective amendments) and supple-
ments to this registration statement, and to file the same,
with the Commission, granting unto said attorneys-in-fact and
agents, and each of them, full power and authority to do and
perform each and every act and thing requisite and necessary to
be done in connection therewith, as fully to all intents and
purposes as he might or could do in person, hereby ratifying
and confirming all that said attorneys-in-fact and agents, or
any of them, or their or his substitute or substitutes, may
lawfully do or cause to be done by virtue hereof.












                             II-7
     
<PAGE>
          Pursuant to the requirements of the Securities Act of
1933, this Registration Statement has been signed below by the
following persons on behalf of the registrant and in the capac-
ities and on the dates indicated.


Signature                Title                   Date
- - ---------                -----                   ----

/s/John L. Castello      Chairman of the Board,
- - -------------------      President and Chief
John L. Castello         Executive Officer
                         (Principal Executive
                         Officer)                June 28, 1996


/s/Patrick J. Scannon    Chief Scientific and
- - ---------------------    Medical Officer and
Patrick J. Scannon       Director                June 28, 1996


/s/Peter B. Davis        Vice President,
- - ---------------------    Finance and Chief
Peter B. Davis           Financial Officer
                         (Principal Financial
                         and Accounting Officer) June 28, 1996


/s/James G. Andress      Director                June 28, 1996
- - ----------------------
James G. Andress


/s/William K. Bowes, Jr. Director                June 28, 1996
- - ----------------------
William K. Bowes, Jr.


/s/Arthur Kornberg       Director                June 28, 1996
- - ----------------------
Arthur Kornberg


/s/Steven C. Mendell     Director                June 28, 1996
- - ----------------------
Steven C. Mendell


/s/W. Denman Van Ness    Director                June 28, 1996
- - -----------------------
W. Denman Van Ness


/s/Gary Wilcox           Director                June 28, 1996
- - -----------------------
Gary Wilcox




                             II-8
     
<PAGE>
                         EXHIBIT INDEX


Exhibit
Number                                                 Page
- - -------                                                ----
4.1       Restated Certificate of Incorporation(1)

4.2       Certificate of Amendment of Restated
          Certificate of Incorporation

4.3       Amended and Restated By-Laws(2)

4.4       Stockholder Rights Agreement dated Octo-
          ber 27, 1993 by and between the Company
          and First Interstate Bank of California
          as Rights Agent(3)

4.5       Certificate of Designations of
          Non-Voting Cumulative Convertible Pre-
          ferred Stock, Series D (4)

4.6       Certificate of Designation of Convert-
          ible Preferred Stock, Series E (4)

4.7       Amended Certificate of Designation of
          Convertible Preferred Stock, Series E

5.1       Opinion of Cahill Gordon & Reindel

10.1      Collaboration Agreement, dated as of
          April 22, 1996, between XOMA Corporation
          and Genentech, Inc. (with certain confi-
          dential information omitted)

10.2      Common Stock and Convertible Note Pur-
          chase Agreement, dated as of April 22,
          1996, between XOMA Corporation and
          Genentech, Inc. (with certain confiden-
          tial information omitted)

10.3      Convertible Subordinated Note Agreement,
          dated April 22, 1996, between XOMA Cor-
          poration and Genentech (with certain
          confidential information omitted)

10.4      Amendment to Convertible Subordinated
          Note Agreement, dated June 13, 1996,
          between XOMA Corporation and Genentech,
          Inc.

23.1      Consent of Arthur Andersen LLP



     
<PAGE>
23.2      Consent of Marshall, O'Toole, Gerstein,
          Murray & Borun

23.3      Consent of Cahill Gordon & Reindel
          (included in Exhibit 5.1)

25.1      Power of Attorney (included on signature
          page to Registration Statement)

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

(1)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 33-59379).

(2)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 33-74982).

(3)  Incorporated by reference to the Company's Current Report
     on Form 8-K dated October 27, 1993.

(4)  Incorporated by reference to the Company's Registration
     Statement on Form S-3 (File No. 333-2493).






































                  CERTIFICATE OF AMENDMENT OF

           RESTATED CERTIFICATE OF INCORPORATION OF

                       XOMA CORPORATION


          XOMA Corporation, a corporation organized and
existing under and by virtue of the General Corporation Law of
the State of Delaware (the "Corporation"), does hereby certify:

          FIRST:  That the Board of Directors of the
Corporation, at a meeting duly held, adopted the following
resolution:

               RESOLVED that this Board deems it
          advisable to amend, and hereby does amend,
          Article IV of the Corporation's Restated
          Certificate of Incorporation to read in its
          entirety as follows:

                               "IV

                         STOCK STRUCTURE

          The Corporation shall be authorized to issue
          two classes of stock to be designated,
          respectively, "preferred stock" and "common
          stock"; the total number of shares of both
          classes of stock authorized to be issued by
          the Corporation shall be Seventy-One Million
          Five Hundred Thousand (71,500,000) shares.
          Such shares shall have no preemptive or
          preferential rights of subscription
          concerning further issuance or authorization
          of any of the Corporation's shares.

          A.   Common Stock.

          The total number of shares of common stock
          authorized to be issued by the Corporation
          shall be Seventy Million (70,000,000) shares
<PAGE>
                              -2-



          and each such share of common stock shall
          have a par value of $.0005.  The common stock
          may be issued from time to time in one or
          more series.

          B.   Preferred Stock.

          The total number of shares of preferred stock
          authorized to be issued by the Corporation
          shall be One Million Five Hundred Thousand
          (1,500,000) shares and each such share of
          preferred stock shall have a par value of
          $.05.  The number of authorized shares of
          preferred stock may be increased or decreased
          (but not below the number of shares thereof
          then outstanding) by the affirmative vote of
          the holders of a majority of the shares of
          preferred stock and common stock then
          outstanding, voting as a class."


          SECOND:  That said amendment has been duly adopted by
the stockholders of this Corporation at a meeting duly held in
accordance with the applicable provisions of Sections 222 and
242 of the General Corporation Law of the State of Delaware.

          THIRD:  That said amendment was duly adopted in
accordance with the applicable provisions of Section 242 of the
General Corporation Law of the State of Delaware.
<PAGE>
                              -3-



          IN WITNESS WHEREOF, XOMA Corporation has caused this
Certificate of Amendment to be signed by John L. Castello, its
Chairman of the Board, President and Chief Executive Officer,
and Christopher J. Margolin, its Vice President, General
Counsel and Secretary, on this 13th day of June, 1996.

                              XOMA CORPORATION



                              By
                                -------------------------------
                                John L. Castello
                                  Chairman of the Board,
                                  President and Chief Executive
                                  Officer

Attest:



- - ---------------------------------
Christopher J. Margolin
  Vice President, General Counsel
  and Secretary







                            AMENDED

                  CERTIFICATE OF DESIGNATION

                              OF

             CONVERTIBLE PREFERRED STOCK, SERIES E

                              OF

                       XOMA CORPORATION

                (Pursuant to Section 151 of the
               Delaware General Corporation Law)


          XOMA CORPORATION, a corporation organized and
existing under the General Corporation Law of the State of
Delaware (the "Corporation"), does hereby certify that (i) no
shares of its Convertible Preferred Stock, Series E, par value
$.05 per share (the "Series E Preferred Stock"), have been
issued and (ii) pursuant to authority conferred upon the Board
of Directors of the Corporation by the Restated Certificate of
Incorporation of the Corporation, as amended, and pursuant to
the provisions of Section 151 of the General Corporation Law of
the State of Delaware, said Board of Directors duly adopted the
following resolution on June 13, 1996, which resolution remains
in full force and effect as of the date hereof:

               RESOLVED, that pursuant to the authority granted
          to and vested in the Board of Directors of the
          Corporation in accordance with the provisions of its
          Restated Certificate of Incorporation, as amended,
          the Board of Directors hereby amends the certificate
          of designation of the Series E Preferred Stock by
<PAGE>
                              -2-



          deleting the first paragraph of subsection (A) of
          Section 6 thereof in its entirety and substituting
          therefor the following:

               (A)  Right to Convert.  Each share of Series E
          Preferred Stock shall be convertible, at the option
          of the holder thereof, into that number of shares of
          the Common Stock, par value $.0005 per share, of the
          Corporation (herein, the "Common Stock") as
          determined by dividing $10,000.00 by the Conversion
          Price (determined as provided below).  The
          "Conversion Price" for any shares of Series E
          Preferred Stock issued in connection with a
          conversion pursuant to clauses (i) through (iii) of
          Section 4(a) of the Convertible Subordinated Note
          Agreement, dated as of April 22, 1996, between the
          Corporation and Genentech, Inc., as amended (the
          "Note Agreement"), shall be an amount per share equal
          to the Current Market Price (as defined below) of the
          Common Stock determined as of the first occurring
          Conversion Date (as such term is defined in Section
          4(a) of the Note Agreement) (herein, the "Initial
          Issue Date").  The "Conversion Price" for any shares
          of Series E Preferred Stock issued in connection with
          either a conversion pursuant to clause (iv) of
          Section 4(a) of the Note Agreement or a prepayment
          pursuant to Section 3(d) of the Note Agreement shall
          be an amount per share equal to the Current Market
          Price of the Common Stock determined as of the date
          of the issuance of such shares (herein, the
          "Prepayment Issue Date").  The number of shares of
          Common Stock into which a share of Series E Preferred
          Stock is convertible is hereinafter referred to as
          the "Conversion Rate" of such series.  The Conversion
          Price shall be subject to adjustment from time to
          time after the Initial Date or applicable Prepayment
          Issue Date, as the case may be, as set forth in this
          Section 6.
<PAGE>
                              -3-



          IN WITNESS WHEREOF, the undersigned have executed
this certificate as of June 13, 1996.


                              ---------------------------------
                              Clarence L. Dellio
                              Senior Vice President, Operations




                              ---------------------------------
                              Christopher J. Margolin
                              Vice President, General Counsel
                              and Secretary



                                                    EXHIBIT 5.1


            [LETTERHEAD OF CAHILL GORDON & REINDEL]




                         June 28, 1996


                                                 (212) 701-3000

XOMA Corporation
2910 Seventh Street
Berkeley, California 94710

Ladies and Gentlemen:

          As counsel for XOMA Corporation (the "Company"), we
are representing the Company in connection with the registra-
tion statement on Form S-3 (the "Registration Statement") filed
with the Securities and Exchange Commission (the "Commission")
on June 28, 1996 relating to the registration under the Securi-
ties Act of 1933, as amended (the "Act"), of 1,500,000 shares
(the "Shares") of the Company's Common Stock, par value $.0005
per share.

          We advise you that in our opinion the Shares were
validly issued and are fully paid and non-assessable.

          We hereby consent to the filing of this opinion with
the Commission as an exhibit to the Registration Statement.  We
also consent to the reference under the heading "Legal Opin-
ions" in the Registration Statement to our having passed upon
the legal matters referred to above.  Our consent to such ref-
erence does not constitute a consent under Section 7 of the
Act, as in consenting to such reference we have not certified
any part of the Registration Statement and do not otherwise
come within the categories of persons whose consent is required
under said Section 7 or under the rules and regulations of the
Commission thereunder.

                              Very truly yours,



                              CAHILL GORDON & REINDEL









WHEREVER CONFIDENTIAL INFORMATION
IS OMITTED HEREIN (SUCH
OMISSIONS ARE DENOTED BY AN
ASTERISK), SUCH CONFIDENTIAL
INFORMATION HAS BEEN SUBMITTED
SEPARATELY TO THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO A
REQUEST FOR CONFIDENTIAL TREATMENT
























                             COLLABORATION AGREEMENT

                               GENENTECH, INC. AND
                                XOMA CORPORATION

<PAGE>
                             COLLABORATION AGREEMENT


     THIS COLLABORATION AGREEMENT is made effective as of the 22nd day of April,
1996 (the "Effective Date") by and between Xoma Corporation, a Delaware
corporation having its principal place of business at 2910 7th Street, Berkeley,
California 94710 ("Xoma") and GENENTECH, INC., a Delaware corporation having its
principal place of business at 460 Point San Bruno Boulevard, South San
Francisco, California 94080 ("Genentech"), each on behalf of itself and its
Affiliates. Xoma and Genentech are sometimes referred to herein individually as
a "Party" and collectively as the "Parties," and references to "Xoma" and
"Genentech" shall include their respective Affiliates.

                                    RECITALS

     1. Genentech has licensed a monoclonal antibody (known as MHM-24) to the
CD11a cell adhesion molecule on the surface of leucocytes under the terms of an
Evaluation and License Agreement dated July 1, 1991 among Genentech, The
Chancellor Masters and Scholars of the University of Oxford, Andrew J. McMichael
and James E.K. Hildreth (the "Oxford Agreement"). Genentech has humanized such
antibody and begun its preclinical development including the development of a
pilot process for producing the antibody.

     2. Genentech and Xoma wish to continue development of and eventually market
such antibody in a collaborative fashion so that the resources and expertise of
each is put to good use.

     3. Genentech wishes to grant to Xoma a sublicense under the Oxford
Agreement to permit Xoma to participate in such collaborative effort.

     4. Simultaneously with the execution of this Agreement, Genentech will
purchase shares of Common Stock of Xoma for an aggregate purchase price of $ *
according to the terms and conditions of a Common Stock and Convertible Note
Purchase Agreement (the "Stock Purchase Agreement") of even date herewith.
Genentech will also loan Xoma funds in an initial amount of $5,000,000 according
to the terms and conditions of a Convertible Subordinated Note Agreement (the
"Note Purchase Agreement") of even date herewith.

                                   ARTICLE 1.
                                   DEFINITIONS

     The following terms shall have the following meanings as used in this
Agreement:

     1.1 "Administration Costs" shall have the meaning defined in Exhibit A.

     1.2 "Affiliate" means an entity that, directly or indirectly, through one
or more intermediaries, is controlled by Xoma or Genentech. As used herein, the
term "control" will mean the direct or indirect ownership of fifty percent (50%)
or more of the stock having the

<PAGE>
<PAGE>


                                       -2-


     right to vote for directors thereof or the ability to otherwise control the
management of the corporation or other business entity.

     1.3 "Allocable Overhead" shall have the meaning defined in Exhibit A.

     1.4 "Anti-CD11a" means that certain monoclonal antibody, which recognizes
the CD11a cell adhesion molecule on leucocytes, more particularly described on
Exhibit B attached hereto.

     1.5 "Control" means possession of the ability to grant a license or
sublicense as provided for herein without violating the terms of any agreement
or other arrangement with any Third Party.

     1.6 "Combination Product Adjustment" means the following: in the event a
Licensed Product is sold in the form of a combination product containing one or
more active ingredients in addition to a Licensed Product, Royalty-Bearing Sales
or Net Sales for such combination product will be adjusted by multiplying actual
Royalty-Bearing Sales, or Net Sales as applicable, of such combination product
by the fraction A/(A + B) where A is the invoice price of the Licensed Product,
if sold separately, and B is the invoice price of any other active component or
components in the combination, if sold separately. If, on a country-by-country
basis, the other active component or components in the combination are not sold
separately in said country, Royalty-Bearing Sales or Net Sales shall be
calculated by multiplying actual Royalty-Bearing Sales or Net Sales of such
combination product by the fraction A/C where A is the invoice price of the
Product if sold separately, and C is the invoice price of the combination
product. If, on a country-by-country basis, neither the Product nor the other
active component or components of the combination product is sold separately in
said country, Royalty- Bearing Sales or Net Sales shall be determined by the
Parties in good faith.

     1.7 "Competing Product" shall mean any monoclonal antibody whose mechanism
of action is initiated by interaction with the CD11a determinant on leucocytes
developed or acquired by either Party.

     1.8 "Co-Promote" means to promote jointly Licensed Products through
Genentech, Xoma and their respective sales forces under a single trademark in
the Co-Promotion Territory.

     1.9 "Co-Promotion Profits" shall have the same meaning as "Operating
Profits and Losses" as defined in Exhibit A.

     1.10 "Co-Promotion Territory" means the * .

     1.11 "Cost of Goods Sold" in the Co-Promotion Territory shall have the
meaning defined in Exhibit A.

     1.12 "Development Costs" shall have the meaning defined in Exhibit A.

<PAGE>
<PAGE>


                                       -3-



     1.13 "Development Plan" means the comprehensive plan for the development of
Anti- CD11a, designed to generate the preclinical, process
development/manufacturing scale-up, clinical and regulatory information required
for filing Drug Approval Applications in the Co- Promotion Territory, and is
attached hereto as Exhibit C but will be modified at least annually by the
Project Core Team. Development shall refer to all activities related to
preclinical testing, toxicology, formulation, process development, manufacturing
scale-up, quality assurance/quality control, clinical studies and regulatory
affairs for a Licensed Product in connection with obtaining Regulatory Approvals
of such Products.

     1.14 "Distribution Costs" shall have the meaning defined in Exhibit A.

     1.15 "Drug Approval Application" means an application for Regulatory
Approval required for commercial sale or use of a Licensed Product as a drug in
the Field in a regulatory jurisdiction.

     1.16 "Field" means * .

     1.17 "Genentech Know-how" means Information which (i) Genentech discloses
to Xoma under this Agreement and (ii) is within the Control of Genentech.

     1.18 "Genentech Patent" means the rights granted by any governmental
authority under a Patent which covers a method, apparatus, material,
manufacture, use, treatment, process, compound, composition, or
product-by-process necessary to make, use or sell a Licensed Product in the
Field, which Patent is owned or Controlled by Genentech, including its interest
in any Patents owned jointly by the Parties as provided hereunder.

     1.19 "Genentech Territory" means * .

     1.20 "Gross Sales" shall have the meaning defined in Exhibit A.

     1.21 "Information" means techniques and data relating to the Licensed
Products, including, but not limited to, biological materials, inventions,
practices, methods, knowledge, knowhow, skill, experience, test data including
pharmacological, toxicological and clinical test data, analytical and quality
control data, marketing, pricing, distribution, cost, sales, manufacturing,
patent data or descriptions.

     1.22 "Initial Indications" means the indications for Licensed Products set
forth in Section 2.1.

     1.23 "Licensed Product" means a formulation for use in the Field containing
Anti- CD11a or any molecule derived from Anti-CD11a that is substituted by the
Steering Committee as the subject of this collaboration, except as otherwise set
forth in Section 2.2.

     1.24 "Marketing Costs" shall have the meaning defined in Exhibit A.

<PAGE>
<PAGE>


                                       -4-



     1.25 "Net Sales" shall have the meaning defined in Exhibit A.

     1.26 "Operating Profits or Losses" shall have the meaning defined in
Exhibit A.

     1.27 "Patent" means (i) valid and enforceable letters patent, including any
extension, registration, confirmation, reissue, continuation, division,
continuation-in-part, re-examination or renewal thereof and (ii) pending
applications for letters patent.

     1.28 "Patent Costs" shall have the meaning defined in Exhibit A.

     1.29 "Phase II Clinical Trial" means such studies in humans of the safety,
dose ranging and efficacy of a Licensed Product which have generated sufficient
data to commence Phase III Clinical Trials.

     1.30 "Phase III Clinical Trial" means a controlled study in humans of the
efficacy and safety of a Licensed Product which is prospectively designed to
demonstrate statistically whether the Licensed Product is effective for use in a
particular indication in a manner sufficient to obtain regulatory approval to
market that Licensed Product and which the Project Core Team designates as a
Phase III Clinical Trial.

     1.31 "Project Core Team" means that body established pursuant to Section
3.2 below.

     1.32 "Regulatory Approval" means any approvals (including pricing and
reimbursement approvals), licenses, registrations or authorizations of any
federal, state or local regulatory agency, department, bureau or other
governmental entity, necessary for the manufacture and sale of Products in a
regulatory jurisdiction.

     1.33 "Royalty-Bearing Sales" means the gross amount invoiced by Genentech
or its permitted sublicensees for sales to an unrelated Third Party of a
Licensed Product in the Genentech Territory, less (i) trade, cash and quantity
discounts or rebates, (ii) credits or allowances given or made for rejection or
return of, and for uncollectible amounts on, previously sold products or for
retroactive price reductions (including rebates similar to Medicare), (iii)
taxes, duties or other governmental charges levied on or measured by the billing
amount, as adjusted for rebates and refunds, (iv) charges for freight and
insurance directly related to the distribution of Licensed Products (to the
extent not paid by the Third Party customer), and (v) credits or allowances
given or made for wastage replacement, indigent patient and similar programs, to
the extent actually deducted from the gross amount invoiced. Such amount shall
then be adjusted by the Combination Product Adjustment, if applicable.

     1.34 "Sales Costs" shall have the meaning defined in Exhibit A.

     1.35 "Sales Representative" means an employee of either Party or its
Affiliates (i) who is responsible for contacting customers and others who can
buy or influence the buying decision on the applicable Licensed Product in the
applicable country in the Co-Promotion Territory, and

<PAGE>
<PAGE>


                                       -5-


     (ii) whose success at such activities is a significant factor in the
ongoing employment of the individual, and shall exclude an employee of either
Party or an Affiliate engaged in telemarketing, professional education, and
similar indirect activities in support of direct selling.

     1.36 "Steering Committee" means that committee established pursuant to
Section 3.1 below.

     1.37 "Third Party" means any entity other than Xoma or Genentech.

     1.38 "Third Party Royalties" means royalties payable to a Third Party in
connection with Licensed Products.

     1.39 "Xoma Know-how" means Information which (i) Xoma discloses to
Genentech under this Agreement and (ii) is within the Control of Xoma.

     1.40 "Xoma Patent" means the rights granted by any governmental authority
under a Patent which covers a method, apparatus, material, manufacture, use,
treatment, process, compound, composition or product-by-process necessary to
make, use or sell a Licensed Product in the Field, which Patent is owned or
Controlled by Xoma, including its interest in any Patents owned jointly by the
Parties as provided hereunder.

                                   ARTICLE 2.
                             SCOPE OF COLLABORATION

     2.1 Initial Indications. The Parties will focus their initial efforts on
the development of Licensed Products to treat psoriasis and prevent or decrease
the rejection of organ transplants.

     2.2 Option to Include Competing Products. Neither Party shall , alone or
with any Third Party, conduct any human clinical trial of any Competing Product
without first giving the other Party (the "Electing Party") advance written
notice. The Electing Party shall have 120 days from the date the first Party
delivers such notice to elect to include such Competing Product as a Licensed
Product. The terms and conditions governing the development and
commercialization of Competing Products shall be similar to the terms and
conditions set forth in this Agreement for the development and commercialization
of Anti-CD11a, taking into account the relative commercial value of the
Competing Product compared to Anti-CD11a. If the Electing Party does not notify
the first Party of its election to so include a Competing Product within such
120-day period, the first Party shall be free to proceed with the development
and commercialization of such Competing Product without any obligation to the
Electing Party.

     2.3 Development Costs.

          (a) Xoma shall bear all Development Costs of Anti-CD11a in the Field
in the Co-Promotion Territory through the successful completion of Phase II
Clinical Trials, including but not limited to certain IND-enabling studies and
supplying Anti-CD11a and all costs of

<PAGE>
<PAGE>


                                       -6-


activities set forth in the Development Plan, as amended from time to time
by the Project Core Team.

          (b) If Xoma elects the option set forth in Section 5.1(b) below, all
Development Costs incurred by the Parties in the Co-Promotion Territory after
the first Regulatory Approval for Anti-CD11a in the United States shall be
charged against Operating Profits (or Losses).

          (c) Genentech shall bear all costs for development of Anti-CD11a in
the Field not incurred in the Co-Promotion Territory.

                                   ARTICLE 3.
                         MANAGEMENT OF THE COLLABORATION

     3.1 Steering Committee.

     (a) Within thirty (30) days of the Effective Date, the Parties will
establish a Steering Committee to oversee and manage the collaboration in the
Co-Promotion Territory contemplated by this Agreement. The Steering Committee
will be composed of two representatives appointed and replaced by Xoma and two
representatives appointed and replaced by Genentech. Such representatives will
be senior officers and/or managers of their respective companies. Any member of
the Steering Committee may designate a substitute to attend and perform the
functions of that member at any meeting of the Steering Committee. The Steering
Committee will meet at least once each calendar quarter, or at any frequency
agreed by the Steering Committee, and will operate by consensus.

          (b) The Steering Committee shall perform the following functions:

               (i) determine the overall strategy for and monitor the
collaboration in the manner contemplated by this Agreement;

               (ii) review and approve development and commercialization plans
and annual budgets formulated by the Project Core Team and annual budgets
formulated by the Project Core Team or the Finance Committee.

               (iii) settle disputes or disagreements that are unresolved by the
Project Core Team or Finance Committee unless otherwise indicated in this
Agreement; and

               (iv) perform such other functions as appropriate to further the
purposes of this Agreement as determined by the Parties.

     If the Steering Committee is unable to resolve a dispute regarding any
issue presented to it, such dispute shall be resolved in accordance with Article
17 below.


<PAGE>
<PAGE>


                                       -7-


     3.2 Project Core Team.

          (a) Within thirty (30) days of the Effective Date, the Parties will
establish the Project Core Team to oversee and control all development and
commercialization of Anti-CD11a in the Co-Promotion Territory, in the Field,
including pre-clinical research, clinical research, manufacturing, regulatory
filings, and post-approval development studies. If the Parties Co- Promote
Licensed Products, the Product Core Team will also (i) monitor, review and
direct the commercialization of Licensed Products in the Co-Promotion Territory,
including annual marketing and sales budgets, annual forecasts of sales and
production requirements, the annual marketing plan, the appropriate role for
Genentech and Xoma to play in commercialization activities in the Co-Promotion
Territory, broad product positioning and creative campaign strategies, pricing,
managed care contract strategies, Phase IV clinical support (especially
strategic direction), and allocation of Marketing Costs, Sales Costs and
Administration Costs of each company as well as (ii) select trademarks for
Licensed Products. The Project Core Team will be composed of three
representatives appointed by each of Xoma and Genentech. Each representative
will have one vote on all matters within the Project Core Team's purview. Such
representatives will include individuals with expertise and responsibilities in
the areas of preclinical development, clinical development, process sciences,
manufacturing, regulatory affairs or product development and marketing. Either
Party may replace any or all of its representatives at any time upon written
notice to the other Party. Any member of the Project Core Team may designate a
substitute to attend and perform the functions of that member at any meeting of
the Project Core Team. The Project Core Team will meet at least once each
calendar quarter, or more frequently, as agreed by the Project Core Team. The
Project Core Team will operate by consensus. If the Project Core Team is unable
to resolve a dispute regarding any issue presented to it, such dispute shall be
resolved in accordance with Article 17 below.

          (b) The Project Core Team shall be responsible for formulating
development and commercialization plans and an annual budget and for
implementing all activities approved by the Steering Committee, except that Xoma
shall formulate the first annual budget and submit it for approval to the
Project Core Team within thirty (30) days of the Effective Date. The Project
Core Team will finalize each subsequent annual budget and modify the Development
Plan at least four months prior to the end of the then-current development year.

          (c) If any Genentech European development partner so requests, Xoma
will consider in good faith allowing a representative of such partner to be a
non-voting member of the Project Core Team.

          (d) The Project Core Team will cease operations and have no further
function hereunder on the later of (i) the date on which the Parties are no
longer developing any Licensed Product in the Co-Promotion Territory, or (ii)
the date on which the Parties are no longer sharing Operating Profits or Losses
with respect to any Licensed Product in the Co-Promotion Territory.


<PAGE>
<PAGE>


                                       -8-


     3.3 Finance Committee. (a) Within thirty (30) days of the date Xoma elects
the option set forth in Section 5.1(b) below, the Parties will establish the
Finance Committee to be composed of two representatives appointed and replaced
by each of Xoma and Genentech. Such representatives will include individuals
with expertise and responsibilities in the areas of accounting, cost allocation,
budgeting and financial reporting. Any member of the Finance Committee may
designate a substitute to attend and perform the functions of that member at any
meeting of the Finance Committee. The Finance Committee will operate by
consensus. If the Finance Committee is unable to resolve a dispute regarding any
issue presented to it, such dispute shall be resolved in accordance with Article
17.

     (b) The Finance Committee shall operate under the direction of the Steering
Committee to provide services to and consult with the Project Core Team in order
to address the financial, budgetary and accounting issues which arise in
connection with the Development Plan and updates thereto as described in Exhibit
A.

     (c) The Finance Committee shall have no involvement in the development of
Licensed Products in the Genentech Territory, which shall be the responsibility
of Genentech, subject to the terms and conditions of this Agreement.

     (d) The Finance Committee will cease operating and have no further function
hereunder on the date on which the Parties are no longer sharing Operating
Profits or Losses with respect to any Licensed Product in the Co-Promotion
Territory.

     3.4



                                                         *




                                   ARTICLE 4.
                    DEVELOPMENT IN THE CO-PROMOTION TERRITORY

     4.1 Development Efforts. Xoma and Genentech each agree to collaborate
diligently in the development of Licensed Products in the Field and to use
commercially reasonable and diligent efforts to develop and bring Licensed
Products to market in the Field as soon as practicable. The Parties further
agree to execute and substantially perform the Development Plan and to cooperate
with the other in carrying out the Development Plan. As used in this Agreement,
the term commercially reasonable and diligent efforts will mean those efforts
consistent with the exercise of prudent scientific and business judgment, as
applied to other pharmaceutical products of similar potential and market size by
the Party in question.


<PAGE>
<PAGE>


                                       -9-


     4.2 Genentech Development Responsibilities. Genentech agrees to be
responsible for the following specific activities necessary to complete
development of Anti-CD11a up to completion of Phase II Clinical Trials:

          (a) Transfer all preclinical data, assays and associated materials,
protocols, procedures and any other information in Genentech's possession
required to initiate clinical development of Anti-CD11a at no cost to Xoma.

          (b) Complete its development of a pilot process to manufacture
Anti-CD11a. Transfer the cell bank for Anti-CD11a production as well as all
associated assays, procedures and other information required for Xoma to supply
Licensed Product for any IND-enabling studies and human clinical trials to the
end of Phase II Clinical Trials. The Project Core Team will determine if any
process improvements or refinements are required and which Party will be
responsible for such improvements or refinements. Xoma will pay all costs
incurred in making such improvements or refinements after Genentech has
transferred the pilot process to Xoma and Xoma has accepted it, such acceptance
not to be unreasonably withheld.

          (c) Conduct additional preclinical research as agreed upon by the
Project Core Team and approved by the Steering Committee to develop Anti-CD11a
for indications additional to the Initial Indications at Xoma's expense.

Development Costs shall exclude the costs incurred by Genentech  pursuant to (a)
and (b) above.

      4.3 Xoma Development Responsibilities. Xoma agrees to be responsible
for the following specific activities necessary to complete development of
Anti-CD11a up to the successful completion of Phase II Clinical Trials:

          (a) Use commercially reasonable and diligent efforts to conduct all
IND- enabling studies and human clinical studies for the Initial Indications
through the successful completion of Phase II Clinical Trials and make all
filings with and supporting all communications with the US Food and Drug
Administration ("FDA") necessary to conduct such studies.

          (b) Upon transfer of manufacturing technology by Genentech, Xoma will
use Genentech's process at Xoma's manufacturing facilities (upgrading such
facilities if necessary) to supply all requirements of Licensed Product for
preclinical and human clinical trials up to the successful completion of Phase
II Clinical Trials in the Co-Promotion Territory.

     4.4 Drug Approval Applications. Consistent with the Development Plan,
Genentech shall use commercially reasonable and diligent efforts to file Drug
Approval Applications and seek Regulatory Approvals for Licensed Products in the
Co-Promotion Territory. Prior to submitting any Drug Approval Application, the
Parties, through the Project Core Team, shall consult, cooperate in preparing
and mutually agree on such Applications and their content and scope. Genentech
shall own all regulatory submissions including all Drug Approval

<PAGE>
<PAGE>


                                      -10-


Applications for Licensed Products in the Co-Promotion Territory. If the
Parties Co-Promote Licensed Products, the Parties will include on all package
labels and inserts for Licensed Products sold in the Co-Promotion Territory the
names and logos of Xoma and Genentech with equal prominence, to the extent
permitted by the applicable regulatory authorities.

     4.5 Development Delays. The Development Plan and the Parties contemplate
that Xoma will successfully complete a Phase II Clinical Trial for one of the
Initial Indications by December 31, 1998, assuming that Genentech provides
necessary materials on a timely basis to Xoma and completes the transfer
described in Section 4.2(a) by June 1, 1996. Any delay in such transfer will
cause the December 31, 1998 date to be extended by the length of time of such
delay. In addition, any material delay by Genentech in performing any of its
obligations under this Agreement that actually causes Xoma not to be able to
meet the timelines set forth in the Development Plan will cause the December 31,
1998 or extended date to be extended by the length of time of the delay by
Genentech.

                                   ARTICLE 5.
                 COMMERCIALIZATION IN THE CO-PROMOTION TERRITORY

     5.1 Xoma Options for Commercialization. If Xoma successfully completes a
Phase II Clinical Trial for one of the Initial Indications by December 31, 1998
(or such other date set pursuant to Section 4.5) as determined by the Steering
Committee, then Xoma may choose either option A or option B as described below
for continuing development and commercialization of Licensed Products:

          (a) Under Option A, Xoma will continue to participate in the
development of Anti-CD11a to the extent elected by Genentech under Section
5.2(b) below. Genentech may elect to have Xoma participate in activities leading
to Regulatory Approval in the Co-Promotion Territory. If Xoma incurs any further
Development Costs due to such participation (elected by Genentech) during the
period ending on the date on which Regulatory Approval by the FDA is first
received for a Licensed Product, such costs will be funded by a loan from
Genentech under the mechanism set forth in the Note Agreement. Upon such
Regulatory Approval, all outstanding balances then due and owing to Genentech
under the provisions of the Note Agreement would be accelerated and converted
into the non-voting preferred stock described in the Note Agreement. Under
Option A, Xoma would *


          (b) Under Option B, Xoma will continue to participate in the
development of Anti-CD11a to the extent elected by Genentech under Section
5.2(b) below. Xoma will * receive the right to Co-Promote Licensed Products.
Xoma may elect to have * . In such event, * , all amounts previously loaned to
Xoma by Genentech will become immediately due and payable in cash, or, at Xoma's
option, will be convertible into equity based on the fair market value of Xoma

<PAGE>
<PAGE>


                                      -11-


Common Stock on such date. Upon receipt of Regulatory Approval from
the FDA, all outstanding balances due and owing to Genentech would be
accelerated as described in (a) above. Under Option B, Xoma would receive

                                                         *

      Xoma will notify Genentech whether it elects Option A or Option B
above within thirty (30) days after the successful completion of a Phase II
Clinical Trial for one of the Initial Indications.

      5.2 Genentech Options for Commercialization. (a) If Xoma elects the
option set forth in Section 5.1(a) above, Genentech may choose to either (1) *

          or (2) * . Genentech shall notify Xoma of its election of option (1)
or option (2) within thirty (30) days of receipt of notice from Xoma of its
election under Section 5.1. If Genentech selects option (1), * .

          (b) Within fifteen days of receipt of Xoma's notice pursuant to
Section 5.1 above, Genentech shall notify Xoma whether Genentech elects to
assume all or some part of the responsibility (subject to * for the development
of Licensed Products under either of the options selected by Xoma under Section
5.1 above, including scale-up of the commercial manufacturing process, conduct
of Phase III Clinical Trials and activities associated with making the Drug
Approval Application in the Co-Promotion Territory. Such election shall be at
Genentech's sole discretion. All other development responsibilities will be
determined by the Project Core Team.

          (c) In the event that Xoma does not successfully complete a Phase II
Clinical Trial for one of the Initial Indications by December 31, 1998 (or such
other date set under Section 4.5), Genentech may select from one of the
following two options: (1) extend the period for successful completion of a
Phase II Clinical Trial for one of the Initial Indications past December 31,
1998 to any date it wishes, thereby also extending the right of Xoma to select
an option under Section 5.1 above, or (2) select the option set forth in Section
5.1(a) above.

     5.3 Commercialization Efforts. If Xoma elects the option set forth in
Section 5.1(b) above, Xoma and Genentech each agree to (i) collaborate
diligently in the commercialization of the Licensed Products and (ii) use
commercially reasonable and diligent efforts to commercialize the Licensed
Products promptly and in such a manner as to maximize Operating Profits. The
Parties agree that Genentech will play the primary role and Xoma the secondary
role in all sales, marketing and product launch activities and tactical
execution of marketing and sales promotional programs in the Co-Promotion
Territory. The Parties shall be guided by a standard of reasonableness in
economic terms and of fairness to each of the Parties, striving to balance as
best they can the legitimate interests and concerns of the Parties and to
realize the economic
<PAGE>
<PAGE>


                                      -12-


potential of the Licensed Products. The Project Core Team (subject to
approval by the Steering Committee) shall develop a plan for commercialization
of Licensed Product at such time as the members of the Project Core Team decide
it is useful to do so. Such plan shall, among other things, determine the
responsibilities for sales of and distributing Licensed Products, development of
marketing and promotional materials and conduct of training programs for Sales
Representatives of both Parties. Unless otherwise agreed, Genentech shall have
the sole responsibility with respect to the following:

          (a) Booking sales for and distributing the Licensed Products.

          (b) Handling all returns of the Licensed Products.

          (c) Handling all recalls of the Licensed Products.

          (d) Handling all aspects of order processing, invoicing and
collection, Licensed Product distribution, warehousing, inventory and
receivables, and collection of data of sales to hospitals and other end users
(e.g., DDD data).

          (e) Handling all other customer service related functions.

     5.4 Sales Efforts in the Co-Promotion Territory.

          (a) Although Genentech has the primary marketing role, Xoma shall be
permitted to deploy Sales Representatives in the Co-Promotion Territory to the
extent that such deployment will enhance the Parties' ability to maximize
Operating Profits, but in no event may Xoma * in the Co-Promotion Territory. The
Parties agree to allocate markets and accounts in an unbiased manner based on
objective, quantifiable information and market research data with the objectives
of allocating to each Party markets and accounts from which each such Party will
have the opportunity to maximize Operating Profits.

          (b) The Parties shall recover their Sales Costs in accordance with
Exhibit A.

                                   ARTICLE 6.
            DEVELOPMENT AND COMMERCIALIZATION IN GENENTECH TERRITORY

     6.1 Development Costs, Marketing Costs and Cost of Goods Sold. Genentech
shall bear all costs related to the development and commercialization of the
Licensed Products in the Genentech Territory. Genentech shall have the sole
responsibility for, and right to make all decisions regarding, all development
and marketing activities in the Genentech Territory.

     6.2 Cooperation on Development Efforts. To facilitate cooperation between
the Parties on the worldwide development and marketing of Licensed Products,
Genentech shall keep Xoma informed of all substantive development activities in
the Genentech Territory. Genentech

<PAGE>
<PAGE>


                                      -13-


     shall consider in good faith any comments made by Xoma. Both Parties agree
that they will do nothing during Licensed Product development activities to
imperil Regulatory Approvals in any country in any territory.

                                   ARTICLE 7.
      EQUITY AND DEBT PURCHASES, MILESTONES, PROFIT SHARING, AND ROYALTIES

     7.1 Payments upon Execution. On the Effective Date, Genentech shall make
the following payments to Xoma:

          (a) $ * to purchase shares of Xoma Common Stock as set forth in the
Stock Purchase Agreement.

          (b) $5,000,000 as an interest-bearing loan under the terms and
conditions of the Note Agreement one of the terms of which is convertibility to
the non-voting Preferred Stock of Xoma upon the earlier of (i) the date of
receipt of any Regulatory Approval in the United States or (ii) the date that is
ten days after the date the loan is due and payable, assuming the loan is not
paid in full before such date. The purpose of Genentech's making such $5,000,000
loan is to provide Xoma the necessary funds to permit it to fulfill its initial
development obligations under this Agreement, and, accordingly, one condition
contained in the Note Purchase Agreement is a condition that any loans made
under the Note Purchase Agreement are to be used solely for the development of
Licensed Product as set forth in the Development Plan. The Parties believe that
the $5,000,000 loan will be sufficient to support development for the first
year, but Genentech will make up any shortfall between the $5,000,000 and the
actual budget for the first year by increasing the loan by that amount when the
next year's budget and modifications to the Development Plan are approved by the
Steering Committee. Similarly, any amount of the $5,000,000 that is over the
first year's budget will be carried forward to fund the next year's budget.

     7.2 Other Note Purchases. Genentech will increase the amount loaned to Xoma
under the terms and conditions of the Note Purchase Agreement for the purposes
of developing Licensed Products at the beginning of each year to cover the
budget formulated by the Project Core Team for that year until the earlier of
(1) December 31, 1998 (or any later date selected by Genentech under Section
5.2(c)(1)) and (2) the completion of a Phase II Clinical Trial for an Initial
Indication. In addition, if Xoma selects the option set forth in Section 5.1 (a)
or Genentech selects such option for Xoma under Section 5.2(c)(2), Genentech
will loan Xoma the amount necessary to fund its development obligations under
the Development Plan based on the annual budget in a similar fashion each year
until the receipt of Regulatory Approval (unless Genentech earlier terminates
this Agreement) under the terms and conditions of the Note Purchase Agreement.

     7.3 Milestone Payment. Genentech shall make a milestone payment to Xoma of
$ * within thirty (30) days after the successful completion of a Phase II
Clinical Trial for one of the Initial Indications, as recommended by the Project
Core Team and approved by the

<PAGE>
<PAGE>


                                      -14-


Steering Committee, but such milestone payment will be made if and only if
such successful completion occurs on or before December 31, 1998 (as may be
extended pursuant to Section 4.5).

     7.4 Share of Operating Profits or Losses. If Xoma selects the option set
forth in Section 5.1(b), Xoma and Genentech shall share in Operating Profits or
Losses from sales of Licensed Products in the Co-Promotion Territory as provided
in Exhibit A. The Parties shall share Operating Profits or Losses hereunder in
the Co-Promotion Territory until the earlier of the date the Parties mutually
agree to terminate the collaboration in the Co-Promotion Territory or * after
the first commercial sale of Licensed Product in the Co-Promotion Territory. At
the end of such period, Xoma's rights to Co-Promote shall cease. Genentech may
continue to market Licensed Products and will pay Xoma a royalty of * of
Royalty- Bearing sales worldwide in any year.

     7.5 Royalties.

          (a) Genentech shall pay Xoma a royalty on Royalty-Bearing Sales of
Licensed Products in the Genentech Territory as follows:


                                                         *


          (b) Genentech shall pay any Third Party royalties owed on account of
sales of Licensed Product in the Genentech Territory, including royalties owed
due to the manufacture of Licensed Products by Genentech. Genentech shall
receive a credit of * % of the royalties it pays on account of the manufacture,
use or sale of Licensed Products against royalties due to Xoma * provided,
however, that in no event shall royalties due to Xoma be reduced to *



     7.6 Royalty Payment Reports. Royalty payments under this Agreement shall be
made to Xoma or its designee quarterly within ninety (90) days following the end
of each calendar quarter for which royalties are due. Each royalty payment shall
be accompanied by a report summarizing the Royalty-Bearing Sales during the
relevant three-month period.

     7.7 Term of Royalty Obligations.

          (a) Genentech shall pay royalties hereunder with respect to each
Licensed Product in each country in the Genentech Territory for * from the date
of first commercial sale in such country.


<PAGE>
<PAGE>


                                      -15-


          (b) Upon expiration of the royalty term for a Licensed Product in a
country as described above, Genentech shall thereafter have an exclusive,
paid-up irrevocable license to make, use, sell, offer for sale, have sold and
import that Licensed Product in that country.

     7.8 Taxes. Xoma shall pay any and all taxes levied on account of, or
measured exclusively by, any payment including royalties it receives under this
Agreement. If laws or regulations require that taxes be withheld, Genentech will
(i) deduct those taxes from the remittable royalty, (ii) timely pay the taxes to
the proper taxing authority, and (iii) send proof of payment to Xoma within
sixty (60) days following that payment.

     7.9 Blocked Currency. In each country where the local currency is blocked
and cannot be removed from the country, royalties shall continue to be accrued
in such country and Royalty-Bearing Sales in such country shall continue to be
reported, but such royalties will not be paid until they may be removed from the
country. At such time as Genentech is able to remove currency from such country
it shall also remove and pay the royalties accrued on Xoma's behalf.

     7.10 Foreign Exchange. For the purpose of computing Royalty-Bearing Sales
for Licensed Products sold in a currency other than United States Dollars, such
currency shall be converted into United States Dollars in accordance with
Genentech's customary and usual translation procedures consistently applied.

     7.11 Payments to or Reports by Affiliates. Any payment required under any
provision of this Agreement to be made to either Party or any report required to
be made by any Party shall be made to or by an Affiliate of that Party if
designated by that Party as the appropriate recipient or reporting entity.

     7.12 Sales By Sublicensees. In the event Genentech grants licenses or
sublicenses to others to make or sell Licensed Products in the Genentech
Territory and such licenses or sublicenses are granted to an unrelated Third
Party (understanding that Roche (as defined in Section 6(b) of the Stock
Purchase Agreement) is not an unrelated Third Party), then Genentech *

     . Any licenses or sublicenses granted by Genentech shall include an
obligation for the licensee or sublicensee to account for and report its
Royalty-Bearing Sales of such Products on the same basis as if such sales were
Royalty-Bearing Sales by Genentech, and Genentech shall pay royalties to Xoma as
if the Royalty-Bearing Sales of the sublicensee were Royalty-Bearing Sales of
Genentech. Genentech shall provide Xoma with copies of any licenses or
sublicenses it grants, with any financial or other confidential terms redacted.


<PAGE>
<PAGE>


                                      -16-


                                   ARTICLE 8.
                             MANUFACTURE AND SUPPLY

     8.1 Transfer of Materials and Knowhow.

     No later than April 23, 1996, Genentech will transfer to Xoma the
pre-master cell bank cells and associated media necessary for Xoma to undertake
the manufacture of Licensed Products for preclinical development and provide
know-how and expertise to help Xoma with such manufacture in a timely fashion
provided that Xoma only uses such biological materials, know-how, reagents and
expertise to manufacture Licensed Products. If Xoma is unable to use the
pre-bank cells and must instead use cells from the master cell bank to be
developed on or about May 1, 1996, the Project Core Team (with the approval of
the Steering Committee) will discuss in good faith whether the delay in
obtaining a cell line has caused a delay in the project timeline of the kind
described in Section 4.5. All transfers of materials and information to Xoma
shall be free of charge to Xoma; provided, however, that Genentech's obligation
to train Xoma personnel in the use of such materials or information shall be
limited to a reasonable number of hours.

     8.2 Manufacture of Licensed Products for Clinical Trials.

          (a) Xoma will supply all quantities of Anti-CD11a for pre-clinical
studies and clinical trials in the Co-Promotion Territory directed toward the
successful completion of a Phase II Clinical Trial for the Initial Indications.

          (b) Xoma shall supply to Genentech, at Xoma's actual Cost of Goods
Sold, all quantities of Licensed Products for preclinical studies and clinical
trials in the Genentech Territory or for expanded needs recommended by the
Project Core Team and approved by the Steering Committee (and budgeted) beyond
the successful completion of a Phase II Clinical Trial for one of the Initial
Indications subject to the election of Genentech under 5.2(b) on providing
Licensed Products.

     8.3 Termination of Participation. If Genentech elects to assume
responsibility for manufacturing under Section 5.2(b), Xoma shall immediately
provide to Genentech at Genentech's request all process and manufacturing
technology, material and data and, provide access to regulatory filings
sufficient to enable Genentech concurrently to produce and supply Licensed
Product. Xoma shall provide reasonable assistance to Genentech with respect to
such transfer so as to permit Genentech to begin manufacturing and supplying its
requirements as soon as possible to minimize any disruption in the continuity of
supply.

                                   ARTICLE 9.
                                    LICENSES

     9.1 Licenses To Xoma Within The Field. Genentech grants to Xoma a
co-exclusive royalty-free license under the Genentech Patents and Genentech
Know-how in the Field to

<PAGE>
<PAGE>


                                      -17-


develop, make, use, sell, and offer for sale Licensed Products in the
Co-Promotion Territory. Xoma covenants and agrees not to develop, make, have
made, use, sell, offer for sale, have sold or import any product using the
Genentech Patents or Know-how outside of the Field. Xoma's rights to sell
Licensed Products are subject to its having made the election to Co-Promote
under Section 5.1(b).

     9.2 License To Genentech Within the Field. Xoma grants to Genentech a
worldwide royalty-free license under the Xoma Patents and Xoma Know-how in the
Field to develop, make, use, sell, offer for sale, have sold and import Licensed
Products. Such license shall be co-exclusive with Xoma in the Co-Promotion
Territory and exclusive even as to Xoma in the Genentech Territory. Genentech
covenants and agrees not to develop, make, have made, use, sell, offer for sale,
have sold or import any product using the Xoma Patents or Know-how outside of
the Field.

     9.3 Sublicensing. Genentech may grant sublicenses *

     Unless otherwise agreed, each sublicensee shall be subject to all of the
obligations of Genentech hereunder applicable to that part of the territory
being licensed.

                                   ARTICLE 10.
                                   TRADEMARKS

     10.1 Product Trademarks. All Licensed Products shall be sold in the
Co-Promotion Territory under trademarks selected by the Project Core Team and
owned by Genentech. Genentech hereby grants Xoma a fully-paid up co-exclusive
license to use its trademarks in the Co-Promotion Territory for the Co-Promotion
activities provided for in this Agreement.

     10.2 Infringement of Trademarks. Xoma shall notify the Project Core Team
promptly upon learning of any actual, alleged or threatened infringement of a
trademark applicable to a Licensed Product (the "Trademark") in the Co-Promotion
Territory or of any unfair trade practices, trade dress imitation, passing off
of counterfeit goods, or like offenses in the Co-Promotion Territory. The
Project Core Team shall confer with Genentech regarding the defense of such
Trademark. The decision whether and how to defend such a Trademark will rest
with Genentech; provided, however that if Genentech fails to bring an action or
proceeding in the Co-Promotion Territory within a period of sixty (60) days of
notice by Xoma to Genentech requesting action, Xoma will have the right, at its
own expense, to bring and control any such action or proceeding in the
Co-Promotion Territory by counsel of its own choice.

     10.3 Costs of Defense for Solely Owned Trademarks. All of the costs,
expenses and legal fees in bringing, maintaining and prosecuting any action to
maintain, protect or defend a Trademark shall be borne solely by the Party
bringing the action and any recovery shall be solely for that Party's account.


<PAGE>
<PAGE>


                                      -18-


                                   ARTICLE 11.
                                 CONFIDENTIALITY

     11.1 Confidentiality; Exceptions. Except to the extent expressly authorized
by this Agreement or otherwise agreed in writing, the Parties agree that, for
the term of this Agreement and for * thereafter, the receiving Party shall keep
confidential and shall not publish or otherwise disclose or use for any purpose
other than as provided for in this Agreement any Information and other
information and materials furnished to it by the other Party pursuant to this
Agreement (collectively, "Confidential Information"), except to the extent that
it can be established by the receiving Party that such Confidential Information:

          (a) was already known to the receiving Party, other than under an
obligation of confidentiality, at the time of disclosure by the other Party;

          (b) was generally available to the public or otherwise part of the
public domain at the time of its disclosure to the receiving Party;

          (c) became generally available to the public or otherwise part of the
public domain after its disclosure and other than through any act or omission of
the receiving Party in breach of this Agreement;

          (d) was disclosed to the receiving Party, other than under an
obligation of confidentiality, by a Third Party who had no obligation to the
disclosing Party not to disclose such information to others; or.

          (e) was subsequently developed by the receiving Party without use of
the Confidential Information as demonstrated by competent written records.

     11.2 Authorized Disclosure. Each Party may disclose Confidential
Information hereunder to the extent such disclosure is reasonably necessary in
filing or prosecuting patent applications, prosecuting or defending litigation,
complying with applicable governmental regulations or conducting preclinical or
clinical trials, provided that if a Party is required by law or regulation to
make any such disclosure of the other Party's Confidential Information it will,
except where impracticable for necessary disclosures, for example in the event
of medical emergency, give reasonable advance notice to the other Party of such
disclosure requirement and, except to the extent inappropriate in the case of
patent applications, will use its reasonable efforts to secure confidential
treatment of such Confidential Information required to be disclosed. In
addition, each Party shall be entitled to disclose, under a binder of
confidentiality containing provisions as protective as those of this Article 11,
Confidential Information to consultants, potential sublicensees and other Third
Parties only for any purpose provided for in this Agreement. Nothing in this
Article 11 shall restrict any Party from using for any purpose any Information
developed by it during the course of the collaboration hereunder.


<PAGE>
<PAGE>


                                      -19-


     11.3 Survival. This Article 11 shall survive the termination or expiration
of this Agreement for a period of * .

     11.4 Termination of Prior Agreement. This Agreement supersedes the
Confidentiality Agreements between the Parties dated October 11, 1995, one of
which was last signed on October 20, 1995 and one of which was last signed on
January 11, 1996 and both of which were amended on April 11, 1996, except that
the Research Scientists, as defined in the Oxford Agreement, shall continue to
be third party beneficiaries under this Agreement to the extent such previous
Confidentiality Agreement is superseded. All Information exchanged between the
Parties under that Agreement shall be deemed Confidential Information and shall
be subject to the terms of this Article 11.

     11.5 Publications. Prior to the launch of any Licensed Product in the
Co-Promotion Territory, the Project Core Team will determine the overall
strategy for publication in support of such Licensed Products in the
Co-Promotion Territory. Except as required by law, each Party agrees that it
shall not publish or present the results of studies carried out as part of the
collaboration without the opportunity for prior review by the other Party. Each
Party shall provide to the other the opportunity to review any proposed
abstracts, manuscripts or presentations (including information to be presented
verbally) which relate to the Field at least forty-five (45) days prior to their
intended submission for publication and such submitting Party agrees, upon
written request from the other Party, not to submit such abstract or manuscript
for publication or to make such presentation until the other Party is given a
reasonable period of time to seek patent protection for any material in such
publication or presentation which it believes is patentable.

                                   ARTICLE 12.
              OWNERSHIP OF INTELLECTUAL PROPERTY AND PATENT RIGHTS

     12.1 Ownership of Intellectual Property. Xoma shall own all inventions made
under this Agreement solely by its employees. Genentech shall own all inventions
made under this Agreement solely by its employees. All inventions made under
this Agreement jointly by employees of Xoma and Genentech will be owned jointly
by Xoma and Genentech and each Party shall retain full ownership under any
Patents resulting therefrom, with full ownership rights in any field and the
right to sublicense without the consent of the other Party, without accounting.
The laws of the United States with respect to joint ownership of inventions
shall apply in all jurisdictions giving force and effect to this Agreement.

     12.2 Disclosure of Patentable Inventions. In addition to the disclosures
required under Article 14, each Party shall provide to the other any invention
disclosure submitted in the normal course and disclosing an invention useful in
the Field and relating to a Licensed Product. Such invention disclosures shall
be provided to the other Party within thirty (30) days after the Party
determines that an invention has been made.


<PAGE>
<PAGE>


                                      -20-


     12.3 Patent Filings. Each Party, at its sole discretion and responsibility
shall file, prosecute and maintain Patents to cover its own discoveries and
inventions relating to any Product in the Field and use reasonable efforts to
file initially all applications in the United States. The determination of the
countries in the Genentech Territory in which to file shall be made by
Genentech, which shall have the right to direct and control all material actions
relating to the prosecution or maintenance of patents in the Genentech Territory
that are being presented by Xoma, including patent interferences,
reexaminations, reissuances, oppositions and revocation proceedings. Genentech
shall file, prosecute and maintain Patents to cover any joint discoveries and
inventions relating to the Field in the United States. Genentech will also file,
prosecute and maintain Patents to cover any joint discoveries and inventions
relating to the Field in such countries in the Genentech Territory as it may
determine. If Genentech elects not to file a joint Patent, it shall so inform
Xoma. Xoma may then file, prosecute and maintain any such joint Patents. The
Party which is responsible for filing such a joint Patent will be termed the
"filing Party." The filing Party shall keep the other Party apprised of the
status of each Patent and shall seek the advice of the other Party with respect
to Patent strategy and draft applications and shall give reasonable
consideration to any suggestions or recommendations of the other party
concerning the preparation, filing, prosecution, maintenance and defense
thereof. The Parties shall cooperate reasonably in the prosecution of all
Patents covering joint inventions and covering Licensed Products and shall share
all material information relating thereto promptly after receipt of such
information. If, during the term of this Agreement, the filing Party intends to
allow any Patent covering a Licensed Product to lapse or become abandoned
without having first filed a substitute, the filing Party shall make reasonable
efforts to notify the other Party of such intention at least sixty (60) days
prior to the date upon which such Patent shall lapse or become abandoned, and
the other Party shall thereupon have the right, but not the obligation, to
assume responsibility for the prosecution, maintenance and defense thereof. Each
Party agrees to bring to the attention of the other Party any patent or patent
application it discovers, or has discovered, and which relates to the subject
matter of this Agreement.

     12.4 Initial Filings If Made Outside of the United States. The Parties
agree to use reasonable efforts to ensure that any Patent filed outside of the
United States prior to a U.S. filing will be in a form sufficient to establish
the date of original filing as a priority date for the purposes of a subsequent
U.S. filing.

     12.5 Patent Costs.

          (a) Patent Costs arising in the Co-Promotion Territory after the
election of Xoma under Section 5.1(b) shall be chargeable to the collaboration
as Other Operating Income/Expense.

          (b) Patent Costs arising in the Genentech Territory after the
Effective Date shall be borne by the Party responsible for filing, as will all
Patent Costs arising in the Co- Promotion Territory unless and until the
election of Xoma under Section 5.1(b).


<PAGE>
<PAGE>


                                      -21-


     12.6 Enforcement Rights.

          (a) Notification of Infringement. If either Party learns of any
infringement or threatened infringement by a Third Party of the Xoma Patents or
Genentech Patents, such Party shall promptly notify the other Party and shall
provide such other Party with available evidence of such infringement.

          (b) Enforcement. Genentech shall have the right, but not the
obligation, to institute, prosecute and control at its own expense any action or
proceeding with respect to infringement of any of the Genentech Patents, by
counsel of its own choice. Xoma shall have the right, at its own expense, to be
represented in any action by counsel of its own choice. Xoma shall have the
right, but not the obligation, to institute, prosecute and control at its own
expense any action or proceeding with respect to infringement of any of the Xoma
Patents, by counsel of its own choice. Genentech shall have the right, at its
own expense, to be represented in any action by counsel of its own choice. In
the event of an infringement of a Joint Patent, the Steering Committee shall
decide the best way for the Parties to proceed. If one Party brings any such
action or proceeding, the other Party agrees to be joined as a party plaintiff
if necessary to prosecute the action or proceeding and to give the first Party
reasonable assistance and authority to file and prosecute the suit. Any damages
or other monetary awards recovered pursuant to this Section 12.6(b) shall be
allocated first to the costs and expenses of the Party bringing suit, then to
the costs and expenses, if any, of the other Party. Any amounts remaining shall
be allocated three-quarters (3/4) to the Party bringing suit and one-quarter
(1/4) to the other Party.

          (c) Settlement with a Third Party. The Party that controls the
prosecution of a given claim with respect to a Licensed Product shall also have
the right to control settlement of such claim; provided, however, that if one
Party controls, no settlement shall be entered into without the written consent
of the other Party if such settlement would materially and adversely affect the
interests of such other Party. If there is no agreement between the Parties,
then the dispute will be resolved pursuant to Section 17. If the dispute is not
resolved pursuant to Section 17, then the case may not be settled.

     12.7 Infringement Defense.

     If a Third Party asserts that a patent or other right owned by it is
infringed by any Licensed Product, Genentech will be solely responsible for
deciding how and whether to defend against any such assertions at its cost and
expense. Xoma shall have the right, at its own expense, to be represented in any
such action by counsel of its choice. If Genentech is required to pay royalties
to such Third Party as a result of such action, it will be entitled to credit
such royalties against royalties owing to Xoma as described in Section 7.5(b).
No settlement of such an action shall be entered into by Genentech without
Xoma's written consent if such settlement would materially and adversely affect
Xoma's interests.


<PAGE>
<PAGE>


                                      -22-


                                   ARTICLE 13.
                         REPRESENTATIONS AND WARRANTIES

     13.1 Representations and Warranties. Each of the Parties hereby represents
and warrants as follows:

          (a) This Agreement is a legal and valid obligation binding upon such
Party and enforceable in accordance with its terms. The execution, delivery and
performance of the Agreement by such Party does not conflict with any agreement,
instrument or understanding, oral or written, to which it is a Party or by which
it is bound, nor violate any law or regulation of any court, governmental body
or administrative or other agency having jurisdiction over it.

          (b) Such Party has not, and during the term of the Agreement will not,
grant any right to any Third Party relating to its respective Patents and
Know-how in the Field which would conflict with the rights granted to the other
Party hereunder.

          (c) In addition, Genentech represents and warrants that it has the
right to grant the licenses granted herein.

     13.2 Performance by Affiliates. The Parties recognize that each may perform
some or all of its obligations under this Agreement through Affiliates,
provided, however, that each Party shall remain responsible and be guarantor of
the performance by its Affiliates and shall cause its Affiliates to comply with
the provisions of this Agreement in connection with such performance.

                                   ARTICLE 14.
                             INFORMATION AND REPORTS

     14.1 Information. Genentech and Xoma will disclose and make available to
each other all preclinical, clinical, regulatory, commercial and other
information, including without limitation all information relevant to the joint
promotion of Licensed Products, known by Genentech or Xoma concerning Licensed
Products at any time during co-development of Licensed Products by the Parties
and during Co-Promotion if Xoma elects the option set forth in Section 5.1(b).
Xoma will disclose any such information to Genentech at any time during the term
of this Agreement. Each Party will use commercially reasonable and diligent
efforts to disclose to the other Party all significant information promptly
after it is learned or its significance is appreciated. Each Party shall own and
maintain its own database of clinical trial data accumulated from all clinical
trials of Licensed Products for which it was responsible and of adverse drug
event information for all Licensed Products. At the option of the requesting
Party, such data shall be provided in a computer readable format by the
providing Party, to the extent available, which shall also assist in the
transfer and validation of such data to the receiving Party.


<PAGE>
<PAGE>


                                      -23-


     14.2 Complaints. Xoma shall maintain a record of all complaints it receives
with respect to any Licensed Product. Xoma shall notify Genentech of any
complaint received by Xoma in sufficient detail and within five (5) business
days after the event, and in any event in sufficient time to allow Genentech to
comply with any and all regulatory requirements imposed upon it in any country.
Genentech shall notify Xoma of any complaint received by Genentech in the
Co-Promotion Territory within forty-five (45) business days after the event.

     14.3 Adverse Drug Events. The Parties recognize that the holder of a Drug
Approval Application may be required to submit information and file reports to
various governmental agencies on compounds under clinical investigation,
compounds proposed for marketing, or marketed drugs. Information must be
submitted at the time of initial filing for investigational use in humans and at
the time of a request for market approval of a new drug. In addition,
supplemental information must be provided on compounds at periodic intervals and
adverse drug experiences must be reported at more frequent intervals depending
on the severity of the experience. Consequently, each Party agrees to:

          (a) provide to the other for initial and/or periodic submission to
government agencies significant information on the drug from preclinical
laboratory, animal toxicology and pharmacology studies, as well as adverse drug
experience reports from clinical trials and commercial experiences with the
compound;

          (b) in connection with investigational drugs, report to the other
within three (3) days of the initial receipt of a report of any unexpected or
serious experience with the drug, or sooner if required for either Party to
comply with regulatory requirements; and

          (c) in connection with marketed drugs, report to the other within five
(5) business days of the initial receipt of a report of any adverse experience
with the drug that is serious and unexpected or sooner if required for either
Party to comply with regulatory requirements. Serious adverse experiences mean
any experience that suggests a significant hazard, contraindication, side effect
or precaution, or any experience that is fatal or life threatening, is
permanently disabling, requires or prolongs inpatient hospitalization, or is a
congenital anomaly, cancer, or overdose. An unexpected adverse experience is one
not identified in nature, specificity, severity or frequency in the current
investigator brochure or the U.S. labeling for the drug. Each Party also agrees
that if it contracts with a Third Party for research to be performed by such
Third Party on the drug, that Party agrees to require such Third Party to report
to contracting Party the information set forth in subparagraph (i), (ii), and
(iii) above.

     14.4 Records of Net Sales and Costs. Each Party will maintain complete and
accurate records which are relevant to costs, expenses, sales and payments under
this Agreement and such records shall be open during reasonable business hours
for a period of five (5) years from creation of individual records for
examination at the other Party's expense and not more often than once each year
by an independent public accountant selected by the other Party as described in
A.6 of Exhibit A. Any records or accounting information received from the other
Party shall

<PAGE>
<PAGE>


                                      -24-


be Confidential Information for purposes of Article 11. Results of any such
audit shall be provided to both Parties, subject to Article 11.

     14.5 Contribution of Information. It is the intention of the Parties that
each will bring to the collaboration such information in its possession that is
useful to the development and commercialization of Licensed Products.

     14.6 Publicity Review. The Parties agree that the public announcement of
the execution of this Agreement shall be in the form of a press release to be
agreed upon on or before the Effective Date and thereafter each Party shall be
entitled to make or publish any public statement consistent with the contents
thereof. Thereafter, Xoma and Genentech will jointly discuss and agree, based on
the principles of this Section 14.6, on any statement to the public regarding
this Agreement or any aspect of this Agreement subject in each case to
disclosure otherwise required by law or regulation as determined in good faith
by each Party. The principles to be observed by Xoma and Genentech in such
public disclosures will be: accuracy, the requirements for confidentiality under
Article 10, the advantage a competitor of Xoma or Genentech may gain from any
public statements under this Section 14.6, and the standards and customs in the
biotechnology and pharmaceutical industries for such disclosures by companies
comparable to Xoma and Genentech. The terms of this Agreement may also be
disclosed to (i) government agencies where required by law, including filings
required to be made by law with the Securities and Exchange Commission, the New
York Stock Exchange, or any national exchange, or (ii) Third Parties with the
prior written consent of the other Party, which consent shall not be
unreasonably withheld, so long as such disclosure is made under a binder of
confidentiality (in the case of Third Parties), so long as highly sensitive
terms and conditions such as financial terms are extracted from the Agreement or
not disclosed upon the request of the other Party and the disclosing Party gives
reasonable advance notice of the disclosure under the circumstances requiring
the disclosure.

                                   ARTICLE 15.
                              TERM AND TERMINATION

     15.1 Term. This Agreement shall commence as of the Effective Date. The
Parties have specifically provided elsewhere in this Agreement the term during
which certain rights and obligations hereunder shall apply. Unless sooner
terminated as provided herein and except as provided in Section 15.4 below, (a)
the remaining provisions of this Agreement relating to activities in the
Co-Promotion Territory shall continue in effect until the date on which the
Parties are no longer entitled to receive a share of Operating Profits or Losses
on any Licensed Product and (b) the remaining provisions of this Agreement
relating to activities in the Genentech Territory shall continue in effect until
the date on which Genentech is no longer paying a royalty on Royalty-Bearing
Sales in the Genentech Territory. Those provisions shall govern the term of the
rights and obligations specifically covered thereby. Upon the expiration of the
term of this Agreement, all licenses granted to Genentech hereunder shall become
fully paid up and irrevocable.


<PAGE>
<PAGE>


                                      -25-


     15.2 Termination by either Party.

          (a) Either Party shall have the right to terminate this Agreement
after December 31, 1998 (or such other date determined pursuant to Section 4.5),
and the rights and obligations of the Parties shall be as follows:

               (i) if either Party terminates this Agreement after the
          successful completion of a Phase II Clinical Trial for one of the
          Initial Indications as determined by the Steering Committee, and Xoma
          had previously selected Option A under Section 5.1, then the
          non-terminating Party may elect, on the date of termination,

                                                         *


               (ii) if Xoma terminates this Agreement after the successful
          completion of a Phase II Clinical Trial for one of the Initial
          Indications as determined by the Steering Committee, and Xoma had
          previously selected Option B under Section 5.1, then Genentech may
          elect, on the date of termination,

                                                         *


               (iii) if Genentech terminates this Agreement after the successful
          completion of a Phase II Clinical Trial for one of the Initial
          Indications as determined by the Steering Committee, and Xoma had
          previously selected Option B under Section 5.1, then Xoma may elect,
          on the date of termination,

                                                         *


               (iv) if Xoma terminates this Agreement and it has not yet
          successfully completed a Phase II Clinical Trial as determined by the
          Steering Committee, then Genentech may elect, on the date of
          termination,

                                                         *


               (v) if Genentech terminates this Agreement and Xoma has not yet
          successfully completed a Phase II Clinical Trial as determined by the
          Steering Committee, then Xoma may elect, on the date of termination,

                                                         *


<PAGE>
<PAGE>


                                      -26-


     Under any of (i) through (v) above, the provisions of the Note Agreement
shall remain in full force and effect. Any such termination shall be effective
six months after written notice thereof. The terminating Party shall reimburse
the other Party for any costs the other Party incurs due to non-cancelable
commitments made under this Agreement so long as the other Party does not make
any such commitments after receiving notice of termination.

          (b) In the event of termination by Xoma pursuant to Section 15.2 or by
Genentech pursuant to Section 15.2(a)(v) or Section 15.3 due to Xoma's material
breach, Xoma shall (i) remain responsible for (A) its share of Development Costs
in the Co-Promotion Territory and (B) for its supply obligations hereunder;
until, in the case of both (A) and (B), Xoma has fully transferred, and enabled
Genentech to perform, all of Xoma's responsibilities under this Agreement,
including but not limited to supplying Genentech's requirements for Anti- CD11a
for a reasonable period of time to allow Genentech to find an alternate source
of supply; and (ii) make its personnel and other resources reasonably available
to Genentech as necessary to effect an orderly transition of development and/or
commercialization responsibilities, with the cost of such personnel and
resources to be borne by Genentech after the effective date of termination.

          (c) In the event of termination by Xoma pursuant to Section 15.3 due
to Genentech's material breach, Genentech will make its personnel and other
resources reasonably available to Xoma as necessary to effect an orderly
transition of development and/or commercialization responsibilities, with the
cost of such personnel and resources to be borne by Xoma after the effective
date of termination.

          (d) Upon any termination under this Section 15.2, the Parties shall
have no further rights or obligations under this Agreement except as set forth
in Sections 15.4 and 15.5.

     15.3 Termination for Breach.  If either Party materially  breaches this
Agreement  at any time,  which  breach is not cured  within  sixty  (60) days of
written  notice thereof from the  non-breaching  Party (or if such breach is not
susceptible  of cure  within  such  period,  the  breaching  Party is not making
diligent good faith efforts to cure such breach),  the non-breaching Party shall
have the right to terminate this Agreement.  Upon such termination,  the Parties
shall have no further rights or obligations  under this Agreement  except as set
forth herein or in Section 15.5. The Parties  acknowledge and agree that failure
to exercise any right or option with respect to any Licensed  Product or to take
any action  expressly within the discretion of a Party shall not be deemed to be
material breach hereunder.

     15.4 Surviving Rights. Except as modified above in Sections 15.2 and 15.3,
the obligations and rights of the Parties under Articles 1, 11, 12, 16, 17 and
18 and Sections 14.4, 15.2 and 15.3 of this Agreement will survive termination
or expiration (in the case of Article 11 and Section 14.4 for the periods set
forth therein). If Genentech must continue to pay a royalty to Xoma after
termination, the provisions of Sections 7.5(b) through and including 7.12 shall
survive such termination.

<PAGE>
<PAGE>


                                      -27-


     15.5 Accrued Rights, Surviving Obligations. Termination, relinquishment or
expiration of the Agreement for any reason shall be without prejudice to any
rights which shall have accrued to the benefit of either party prior to such
termination (including paid up irrevocable licenses), relinquishment or
expiration, including damages arising from any breach hereunder. Such
termination, relinquishment or expiration shall not relieve either Party from
obligations which are expressly indicated to survive termination or expiration
of the Agreement.

                                   ARTICLE 16.
                                 INDEMNIFICATION

     16.1 Indemnification in the Genentech Territory.

          (a) Genentech hereby agrees to save, defend and hold Xoma and its
agents and employees harmless from and against any and all suits, claims,
actions, demands, liabilities, expenses and/or loss, including reasonable legal
expense and attorneys' fees ("Losses") resulting directly from the manufacture,
use, handling, storage, sale or other disposition of chemical agents or Licensed
Products sold or used in the Genentech Territory by Genentech, its Affiliates,
agents or sublicensees except to the extent such Losses result from the
negligence or willful misconduct of Xoma, and from any Losses resulting directly
from Xoma's use of technology supplied to Xoma by Genentech except to the extent
any such Losses result from modifications by Xoma (without Genentech's written
consent) or a Third Party of such technology.

          (b) In the event that Xoma is seeking indemnification under Section
16.1(a), it shall inform Genentech of a claim as soon as reasonably practicable
after it receives notice of the claim, shall permit Genentech to assume
direction and control of the defense of the claim (including the right to settle
the claim solely for monetary consideration), and shall cooperate as requested
(at the expense of Genentech) in the defense of the claim.

          (c) Xoma hereby agrees to save, defend and hold Genentech and its
agents and employees harmless from and against any and all suits, claims,
actions, demands, liabilities, expenses and/or loss, including reasonable legal
expense and attorneys' fees ("Losses") resulting directly from the manufacture
by Xoma of Licensed Products sold or used in the Genentech Territory by
Genentech, its Affiliates, agents or sublicensees or otherwise from the
negligence or willful misconduct of Xoma and from any Losses resulting directly
from Genentech's use of any technology supplied to Genentech by Xoma except to
the extent any such Losses result from modifications by Genentech (without
Xoma's written consent) or a Third Party of such technology.

          (d) In the event Genentech is seeking indemnification under Section
16.1(c), it shall inform Xoma of a claim as soon as reasonably practicable after
it receives notice of the claim, shall permit Xoma to assume direction and
control of the defense of the claim (including the right to settle the claim
solely for monetary consideration), and shall cooperate as requested (at the
expense of Xoma) in the defense of the claim.

<PAGE>
<PAGE>


                                      -28-



     16.2 Indemnification in the Co-Promotion Territory.

          (a) If the Parties Co-Promote Licensed Product, then each Party agrees
to save, defend and hold the other Party and its agents and employees harmless
from and against any and all losses resulting directly or indirectly from the
manufacture, use, handling, storage, sale or other disposition of chemical
agents or Licensed Products sold or used in the Co- Promotion Territory by the
indemnifying Party, its Affiliates, agents or sublicensees, but only to the
extent such losses result from the negligence or willful misconduct of the
indemnifying Party or its employees and agents and do not also result from the
negligence or willful misconduct of the Party seeking indemnification. Any other
losses resulting directly or indirectly from the manufacture, use, handling,
storage, sale or other disposition of chemical agents or Licensed Products in
the Co-Promotion Territory shall be charged to the collaboration as an Other
Operating Income/Expense at the time such claim is finally determined, whether
by judgment, award, decree or settlement.

          (b) In the event that either Party receives notice of a claim with
respect to a Licensed Product in the Co-Promotion Territory, such Party shall
inform the other Party as soon as reasonably practicable. The Parties shall
confer how to respond to the claim and how to handle the claim in an efficient
manner.

                                   ARTICLE 17.
                               DISPUTE RESOLUTION

     17.1 Disputes. The Parties recognize that disputes as to certain matters
may from time to time arise during the term of this Agreement which relate to
either Party's rights and/or obligations hereunder. It is the objective of the
Parties to establish procedures to facilitate the resolution of disputes arising
under this Agreement in an expedient manner by mutual cooperation and without
resort to litigation. To accomplish this objective, the Parties agree to follow
the procedures set forth in this Article 17 if and when a dispute arises under
this Agreement.

     Unless otherwise specifically recited in this Agreement, disputes among
members of the Project Core Team or the Finance Committee will be resolved as
recited in this Article 17. Any disputes relating to the collaboration shall be
first referred to the Steering Committee by either Party at any time after such
dispute has arisen and such Party believes that there has been sufficient
discussion of the matter at the Project Core Team level. If the Steering
Committee is unable to resolve such a dispute within ninety (90) days of being
requested by a Party to resolve the dispute or the Steering Committee is unable
to resolve a dispute among its members, any Party may, by written notice to the
other, invoke the provisions of Section 17.2 hereinafter.

     17.2 Mediation. The Parties agree that any dispute, controversy or claim
(except as to any issue relating to intellectual property owned in whole or in
part by Xoma or Genentech or any equitable claim) arising out of or relating to
this Agreement, or the breach, termination, or invalidity thereof, shall be
resolved through negotiation and mediation. If a dispute arises

<PAGE>
<PAGE>


                                      -29-


between the parties, and if said dispute cannot be resolved pursuant to
Section 17.1, the Parties agree to try in good faith to resolve such dispute by
mediation administered by the American Arbitration Association in accordance
with its Commercial Mediation Rules. The mediation proceeding shall be conducted
at the location of the party not originally requesting the resolution of the
dispute. The parties agree that they shall share equally the cost of the
mediation filing and hearing fees, and the cost of the mediator. Each party must
bear its own attorney's fees and associated costs and expenses.

     17.3 Jurisdiction. For the purposes of this Article 17, the Parties agree
to accept the jurisdiction of the federal courts located in the Northern
District of California for the purposes of enforcing the agreements reflected in
this Article.

     17.4 Determination of Patents and Other Intellectual Property. Any dispute
relating to the determination of validity of a Party's Patents or other issues
relating solely to a Party's intellectual property shall be submitted
exclusively to the federal courts located in San Francisco County, California,
and the Parties hereby consent to the jurisdiction and venue of such court.

                                   ARTICLE 18.
                                  MISCELLANEOUS

     18.1 Assignment.

          (a) Either Party may assign any of its rights under this Agreement in
any country to any Affiliates and, with the prior written consent of the other
Party, may delegate its obligations under this Agreement in any country to any
Affiliates; provided, however, that any such assignment shall not relieve the
assigning Party of its responsibilities for performance of its obligations under
this Agreement.

          (b) Either Party may assign all of its rights and obligations under
this Agreement in connection with a merger or similar reorganization or the sale
of all or substantially all of its assets, or otherwise with the prior written
consent of the other Party; provided, however, that Xoma may not so assign its
rights and obligations if it is not the surviving company and the acquiror of
Xoma is a direct competitor of Genentech. This Agreement shall survive any such
merger or reorganization of either Party with or into, or such sale of assets
to, another party and no consent (except as otherwise set forth above) for such
merger, reorganization or sale shall be required hereunder.

          (c) This Agreement shall be binding upon and inure to the benefit of
the successors and permitted assigns of the Parties. Any assignment not in
accordance with this Agreement shall be void.

     18.2 Non-Solicitation. The Parties recognize that each Party has a
substantial interest in preserving and maintaining confidential its Confidential
Information hereunder. Each Party recognizes that certain of the other Party's
employees, including those engaged in development,

<PAGE>
<PAGE>


                                      -30-


marketing and sale of any Licensed Product, may have access to such
Confidential Information of the other Party. The Parties therefore agree not to
solicit or otherwise induce or attempt to induce for purposes of employment, any
employees from the other Party involved in the development, marketing or sales
of any Licensed Product during the period in which any Party is developing or
commercializing a Licensed Product in the Co-Promotion Territory hereunder and
for a period of two years thereafter.

     18.3 Consents Not Unreasonably Withheld. Whenever provision is made in this
Agreement for either Party to secure the consent or approval of the other, that
consent or approval shall not unreasonably be withheld, and whenever in this
Agreement provision is made for one Party to object to or disapprove a matter,
such objection or disapproval shall not unreasonably be exercised.

     18.4 Retained Rights. Nothing in this Agreement shall limit in any respect
the right of either Party to conduct research and development with respect to
and market products outside the Field using such Party's technology.

     18.5 Force Majeure. Neither Party shall lose any rights hereunder or be
liable to the other Party for damages or losses on account of failure of
performance by the defaulting Party if the failure is occasioned by government
action, war, fire, explosion, flood, strike, lockout, embargo, act of God, or
any other cause beyond the control of the defaulting Party, provided that the
Party claiming force majeure has exerted all reasonable efforts to avoid or
remedy such force majeure; provided, however, that in no event shall a Party be
required to settle any labor dispute or disturbance.

     18.6 Further Actions. Each Party agrees to execute, acknowledge and deliver
such further instruments, and to do all such other acts, as may be necessary or
appropriate in order to carry out the purposes and intent of this Agreement.

     18.7 No Right to Use Names. Except as otherwise provided herein, no right,
express or implied, is granted by the Agreement to use in any manner the name
"Xoma," "Genentech" or any other trade name or trademark of the other Party or
its Affiliates in connection with the performance of the Agreement.

     18.8 Notices. All notices hereunder shall be in writing and shall be deemed
given if delivered personally or by facsimile transmission (receipt verified),
telexed, mailed by registered or certified mail (return receipt requested),
postage prepaid, or sent by express courier service, to the Parties at the
following addresses (or at such other address for a party as shall be specified
by like notice; provided, that notices of a change of address shall be effective
only upon receipt thereof).



<PAGE>
<PAGE>


                                      -31-


         If to XOMA,
         addressed to:              XOMA CORPORATION
                                    2910 7th Street, Berkeley
                                    California 94710
                                    Attention:  Corporate Secretary
                                    Telephone:  (510)  644-1170
                                    Telecopy:   (510)  649-7571
                                    with a copy to:  C.L. Dellio

         If to Genentech,
         addressed to:              GENENTECH, INC.
                                    460 Point San Bruno Boulevard
                                    South San Francisco, CA  94080
                                    Attention:  Corporate Secretary
                                    Telephone: (415) 225-1000
                                    Telecopy:  (415) 952-9881

     18.9 Waiver. Except as specifically provided for herein, the waiver from
time to time by either of the Parties of any of their rights or their failure to
exercise any remedy shall not operate or be construed as a continuing waiver of
same or of any other of such Party's rights or remedies provided in this
Agreement.

     18.10 Severability. If any term, covenant or condition of this Agreement or
the application thereof to any Party or circumstance shall, to any extent, be
held to be invalid or unenforceable, then (i) the remainder of this Agreement,
or the application of such term, covenant or condition to Parties or
circumstances other than those as to which it is held invalid or unenforceable,
shall not be affected thereby and each term, covenant or condition of this
Agreement shall be valid and be enforced to the fullest extent permitted by law;
and (ii) the Parties hereto covenant and agree to renegotiate any such term,
covenant or application thereof in good faith in order to provide a reasonably
acceptable alternative to the term, covenant or condition of this Agreement or
the application thereof that is invalid or unenforceable, it being the intent of
the Parties that the basic purposes of this Agreement are to be effectuated.

     18.11 Ambiguities. Ambiguities, if any, in this Agreement shall not be
construed against any Party, irrespective of which Party may be deemed to have
authorized the ambiguous provision.

     18.12 Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     18.13 Entire Agreement. This Agreement, including all Exhibits attached
hereto which are hereby incorporated herein by reference, sets forth all the
covenants, promises, agreements, warranties, representations, conditions and
understandings between the Parties hereto and

<PAGE>
<PAGE>


                                      -32-


supersedes and terminates all prior agreements and understandings between
the Parties. There are no covenants, promises, agreements, warranties,
representations, conditions or understandings, either oral or written, between
the Parties other than as set forth herein and therein. No subsequent
alteration, amendment, change or addition to this Agreement shall be binding
upon the Parties hereto unless reduced to writing and signed by the respective
authorized officers of the Parties.

     IN WITNESS WHEREOF, the Parties have executed this Agreement in duplicate
originals by their proper officers as of the date and year first above written.


XOMA CORPORATION                           GENENTECH, INC.



By:----------------------------------       By:---------------------------
     Clarence L. Dellio                       John P. McLaughlin
     Senior Vice President, Operation         Executive Vice President

<PAGE>
<PAGE>



                                    EXHIBIT A

                  FINANCIAL PLANNING, ACCOUNTING AND REPORTING
                 FOR THE XOMA/GENENTECH COLLABORATION AGREEMENT

     This Exhibit A to the Collaboration Agreement (the "Agreement") dated as of
April 22, 1996, between Xoma Corporation ("Xoma") and Genentech, Inc.
("Genentech") addresses the financial planning, accounting policies and
procedures to be followed in determining Operating Profits or Losses and related
sharing of revenue and expenses in the Co-Promotion Territory if Xoma elects the
option set forth in Section 5.1(b) of the Agreement. Terms not defined in this
Exhibit shall have the meanings set forth in the Agreement.

     This Exhibit sets forth the principles for reporting actual results and
budgeted plans of the combined operations in the Co-Promotion Territory, the
frequency of reporting, and the methods of determining payments to the parties
and auditing of accounts.

     For purposes of this Exhibit only, the consolidated accounting of
operations for the collaboration in the Co-Promotion Territory shall be referred
to as GenXoma. GenXoma is not a legal entity and has been defined for
identification purposes only.

A.1. Principles of Reporting

     The results of operations of GenXoma will be presented in the following
     format, with the categories as defined in Section A.4 below:

                                      Xoma            Genentech        Total

     Gross Sales
     less Sales Returns and Allowances
           = Net Sales
     less Cost of Sales
           = Gross Profits
     less Marketing Costs
     less Sales Costs
     less Development Costs chargeable to GenXoma
     less Other Operating Income/Expense
           = Contribution
     less Distribution Costs
     less Administration Costs
           = Operating Profit (Loss)

     It is the intention of the Parties that the interpretation of these
definitions will be consistent with generally accepted accounting principles in
the United States.


<PAGE>
<PAGE>


                                       -2-


A.2.   Frequency of Reporting

       The fiscal year of GenXoma will be a calendar year.

       Reporting by each Party for GenXoma  revenues and expenses will be
performed as follows:

Reporting Event               Frequency            Timing of Submission

Actuals                       Quarterly            Q1-Q3:            +30 days
                                                      Q4:            +45 days

Forecasts                     Quarterly            Mid Quarter
(rest of year - by quarter)

Budgets                       Annually             October 15th
(one year - by month)

Long Range Plan               Annually             May 1st
(current year plus 5 years)

Genentech will be responsible for the preparation of consolidated
reporting, calculation of the profit/loss sharing and determination of the cash
settlement. Genentech will provide the Finance Committee within five working
days of the submission date shown above, a statement showing the consolidated
results and calculations of the profit/loss sharing and cash settlement required
in a format agreed to by the Parties.

Reports of actual results compared to budget will be made to the Project
Core Team on a quarterly basis. After approval by the Finance Committee as to
amounts, the Finance Committee will forward the report to the Steering Committee
for its approval. Line item variances from budgets judged to be significant by
the Finance Commitee will only be included in calculation of Operating Profit
and Loss when approved by the Project Core Team and the Steering Committee.

On a monthly basis Genentech will supply Xoma with Gross Sales in units of
each month's sales according to Genentech's sales reporting system, which shall
be consistent with the definitions in Section A.4.

The Finance Committee will meet as appropriate but at least quarterly to
review and approve the following:


<PAGE>
<PAGE>


                                       -3-


                -        Actual Results
                -        Forecasts
                -        Budget
                -        Inventory Levels
                -        Sales Returns and Allowances
                -        Other  financial  matters,   including  each
                         Party's methodologies for charging costs and
                         allocating Sales  Representatives to GenXoma
                         for  actuals,  forecasts,  budgets  and long
                         range plans and the results of applying such
                         methodologies.

A.3.     Budget and Long Range Plan

Responsibility for the Budget and Long Range Plan will rest with the
Project Core Team, who will develop budgets for development and
commercialization in coordination with the Finance Committee, subject to final
approval by the Steering Committee.

Budgets will be prepared annually. In addition, headcount chargeable to
GenXoma will be agreed to annually.

Budgets will be supplemented with detailed business plans for clinical
trials, registration applications, and detailed plans for product introduction,
sales efforts and promotion as determined by the Project Core Team. Budgets,
once approved by the Steering Committee, can only be changed with the approval
of the Steering Committee.

A five-year Long Range Plan for GenXoma will be established on a yearly
basis under the direction of the Steering Committee and submitted to Genentech
and Xoma by May 1st.

A.4. Definitions

     A.4.1 "Administration Costs" means costs chargeable to GenXoma equal to * %
of the sum of each party's own Marketing Costs and Sales Costs (both only to the
extent chargeable to GenXoma).

     A.4.2 "Allocable Overhead" means costs incurred by a Party or for its
account which are attributable to a Party's supervisory, services, occupancy
costs, corporate bonus (to the extent not charged directly to department), and
its payroll, information systems, human relations or purchasing functions and
which are allocated to company departments based on space occupied or headcount
or other activity-based method. Allocable Overhead shall not include any costs
attributable to general corporate activities including, by way of example,
executive management, investor relations, business development, legal affairs
and finance.
<PAGE>
<PAGE>


                                       -4-



     A.4.3. "Cost of Goods Sold" means the fully burdened cost of the Licensed
Product in final therapeutic form. The fully burdened cost of the Licensed
Product will be determined in accordance with generally accepted accounting
principles in the United States as applied by the Party performing or
contracting for each stage of the manufacturing process and will include direct
labor, material, product testing costs and Allocable Overhead.

     A.4.4. "Cost of Sales" means Cost of Goods Sold, Third Party Royalties *
(i.e., any allocable intellectual property acquisition and licensing costs) and
outbound freight on sales if borne by the seller.

     A.4.5. "Development Costs" means costs, including Allocable Overhead,
incurred in any phase of the activities required to obtain the authorization
and/or ability to manufacture, formulate, fill, ship and/or sell a Licensed
Product in the Field in commercial quantities in the Co-Promotion Territory.
Development Costs shall include but are not limited to the cost of studies on
the toxicological, pharmacokinetic, metabolic or clinical aspects of a Licensed
Product conducted internally or by individual investigators, or consultants
necessary for the purpose of obtaining and/or maintaining approval of a Licensed
Product in the Field by a government organization in a country of the
Co-Promotion Territory, and costs for preparing, submitting, reviewing or
developing data or information for the purpose of submission to a governmental
authority to obtain and/or maintain approval of a Licensed Product in the Field
in a country of the Co-Promotion Territory as well as costs of process
development scale-up and recovery (including allocable depreciation and plant
operating costs). In addition, Development Costs in the Co-Promotion Territory
shall include the cost of post-launch clinical studies in support of a Licensed
Product in the Field in the Co- Promotion Territory. Development Costs in the
Co-Promotion Territory shall include expenses for compensation, benefits and
travel and other employee-related expenses, as well as data management,
statistical designs and studies, document preparation, and other expenses
associated with the clinical testing program.

     A.4.6. "Distribution Costs" means the costs, including Allocable Overhead,
specifically identifiable to the distribution of a Licensed Product including
customer services, collection of data of sales to hospitals and other end users
(e.g. DDD sales data), order entry, billing, credit and collection and other
activities described in Section 5.3 of the Agreement. For the purpose of this
Agreement, only Genentech will charge GenXoma for Distribution Costs an amount
of * % of Net Sales in a lump sum.

     A.4.7. "Gross Sales" means the gross amount invoiced by either Party or
their Affiliates or permitted sublicensees for sales of a Licensed Product to
Third Parties in the Co- Promotion Territory.


<PAGE>
<PAGE>


                                       -5-


     A.4.8. "Marketing Costs" means the costs, excluding Allocable Overhead, of
marketing, promotion, advertising, professional education, product related
public relations, relationships with opinion leaders and professional societies,
market research, healthcare economics studies and other similar activities
directly related to the Licensed Products and approved by the Joint
Commercialization Committee. Such costs will include both internal costs (e.g.,
salaries, benefits, supplies and materials, etc.) as well as outside services
and expenses (e.g., consultants, agency fees, meeting costs, etc.). Marketing
Costs shall also include activities related to obtaining reimbursement from
payers and costs of sales and marketing data. Marketing Costs will specifically
exclude the costs of activities which promote either Party's business as a whole
without being product specific (such as corporate image advertising).

     A.4.9. "Net Sales" means Gross Sales less the sum of (a), (b) and (c) where
(a) is a provision, determined under generally accepted accounting principles in
the United States, for (i) trade, cash and quantity discounts or rebates (other
than price discounts granted at the time of invoicing and which are included in
the determination of Gross Sales), (ii) credits or allowances given or made for
rejection or return of, and for uncollectible amounts on, previously sold
products or for retroactive price reductions (including Medicare and similar
types of rebates), (iii) taxes, duties or other governmental charges levied on
or measured by the billing amount, as adjusted for rebates and refunds, (iv)
charges for freight and insurance directly related to the distribution of
Products, and (v) credits or allowances given or made for wastage replacement,
indigent patient and any other sales programs agreed to by the Parties, (b) is a
periodic adjustment of the provision determined in (a) to reflect amounts
actually incurred for (i), (ii), (iii), (iv) and (v), and (c) is the Combination
Product Adjustment as defined in the Agreement, if any. Provisions allowed in
(a) and adjustments made in (b) and (c) will be reviewed by the Finance
Committee.

     A.4.10. "Operating Profit or Loss" means GenXoma's Net Sales less the
following items: Cost of Sales, Marketing Costs, Sales Costs, Development Costs,
(to the extent chargeable to GenXoma), Other Operating Income/Expense,
Distribution Costs and Administrative Costs, for a given period.

     A.4.11. "Other Operating Income/Expense" means other operating income or
expense from or to third parties which is not part of the primary business
activity of GenXoma, but is considered and approved by the Finance Committee as
income or expense generated from GenXoma operations, and limited to the
following:

     -        Inventory Write-Offs
     -        Patent Costs (as limited byArticle 12 of the Agreement)
     -        Product liability insurance to the extent the Parties obtain a
              joint policy

<PAGE>
<PAGE>


                                       -6-


     -        Indemnification costs (as defined in Article 16 of the Agreement)
     -        Other (To be approved by Steering Committee)

     A.4.12. "Patent Costs" means the fees and expenses paid to outside legal
counsel and experts, and filing and maintenance expenses, incurred after the
Effective Date in connection with the establishment and maintenance of rights
under Patents covering any Licensed Product, including costs of patent
interference, reexamination, reissue, opposition and revocation proceedings.


     A.4.13. "Sales Costs" means costs, including Allocable Overhead, approved
by the Project Core Team and the annual budget and specifically identifiable to
the sales of Licensed Products to all markets in the Co-Promotion Territory
including the managed care market. Sales Costs shall include costs associated
with Sales Representatives, including compensation, benefits and travel,
supervision and training of the Sales Representatives, sales meetings, and other
sales expenses. Sales Costs will not include the start-up costs associated with
either Party's sales force, including recruiting, relocation and other similar
costs.

     A.4.14. "Sales Returns and Allowances" means Gross Sales less Net Sales.

A.5. Audits and Interim Reviews

Either Party shall have the right to request that the other Party's
independent accounting firm perform an audit or interim review of the other
Party's books in order to express an opinion regarding said Party's compliance
with generally accepted accounting principles. Such audits or review will be
conducted at the expense of the requesting Party.

Either Party shall have the right to request that its independent
accounting firm perform an audit of the other Party's books of accounts for the
sole purpose of verifying compliance with the Agreement. Such audits will be
conducted at the expense of the requesting Party; provided, however, that if the
audit results in an adjustment of greater that * % of Operating Losses or
Profits in any period, the cost of the audit will be borne by the Party audited.
Audit results will be shared with both Parties.

A.6. Payments between the Parties

Balancing payments between the Parties will be approved by the Steering
Committee based on Operating Profit or Loss. Payments will be made quarterly
based on actual results within 90 days after the end of each quarter, adjusted
for reimbursement of the net expenses or income incurred or received by each
Party.


<PAGE>
<PAGE>


                                       -7-


A.7. Accounting for Development Costs, Marketing Costs and Sales Costs

All Development Costs, Marketing Costs and Sales Costs will be based on the
appropriate costs definition stated in Section A.4 of this Exhibit.

Each party shall report Development Costs in a manner consistent with its
Project Cost System. In general, these project cost systems report actual time
spent on specific projects, apply the actual labor costs, capture actual costs
of specific projects and allocate other expenses to projects. For Marketing
Costs, the Parties will report costs based on spending in Marketing departments.
The Parties acknowledge that the methodologies used will be based on systems in
place and consistent with Section A.10 of this Exhibit.

For the purpose of determining actual and budgeted Sales Costs, the
Parties, through the Project Core Team and the Finance Committee shall determine
the number of Sales Representatives selling Licensed Products during the period
and develop a method consistent with Section A.4 and A.10 of this Exhibit to
allocate Sales Costs to those Sales Representatives.

A.8. Sharing of Operating Profits and Losses

The Parties agree to share the Operating Profit or loss resulting from the
collaborative arrangement in the Co-Promotion Territory according to the
following manner:

For each calendar year, Xoma shall receive * % of the Operating Profits. To
the extent there is an Operating Loss on sales of Licensed Product in the
Co-Promotion Territory in any calendar year, Xoma shall absorb * % of such loss.

A.9. Start of Operations

Operation of GenXoma will be deemed to commence on the date that Xoma
selects the option set forth in Section 5.1(b) of the Agreement. Costs incurred
prior to that date are not chargeable to GenXoma.

A.10. Guidelines for Charging Costs

     The following guidelines shall be used in determining amounts chargeable to
GenXoma.

     10.1      If an expense is specifically and exclusively (i.e., for no other
               product) used for the development or commercialization of a
               Licensed Product in

<PAGE>
<PAGE>


                                       -8-


               the Field in the Co-Promotion Territory, then 100% of the expense
               will be charged to GenXoma.

     10.2      If an expense is specifically and exclusively (i.e., for no other
               product) used for the development or commercialization of a
               Licensed Product in the Field in both the Co-Promotion Territory
               and the Genentech Territory, then the following shall apply:

          (a)  If the portion of that expense used for the development or
               commercialization of a Licensed Product in the Field in the
               Genentech Territory can be objectively determined through
               specific means (e.g., man hours of effort, amounts consumed,
               etc.), then the amount so used will be charged to Genentech and
               the remaining portion will be charged to GenXoma.

          (b)  If the portion of that expense used for the development or
               commercialization of a Licensed Product in the Field in the
               Genentech Territory cannot be objectively determined through
               specific means, then only the direct and incremental costs
               related to the Licensed Product in the Field in the Genentech
               Territory will be charged to Genentech and the remaining portion
               will be charged to GenXoma.

     10.3      If an expense within the Co-Promotion Territory is not
               specifically and exclusively (i.e., for other products in
               addition to a Licensed Product) used for the development or
               commercialization of a Licensed Product in the Field in the
               Co-Promotion Territory, then the following shall apply:

          (a)  If the portion of that expense used for the development or
               commercialization of a Licensed Product in the Field in the Co-
               Promotion Territory can be objectively determined through
               specific means (e.g., man hours of effort, amounts consumed,
               etc.), then the amount so used will be charged to GenXoma.

          (b)  If the portion of that expense used for the development or
               commercialization of a Licensed Product in the Field in the Co-
               Promotion Territory cannot be objectively determined through
               specific means, then only the direct and incremental costs
               related to the Licensed Product in the Field shall be charged to
               GenXoma.


<PAGE>
<PAGE>



                                                                  EXHIBIT B























                                        *



<PAGE>
<PAGE>



                                                                    EXHIBIT C























                                        *

<PAGE>
<PAGE>



























                                        *

                                       -2-
<PAGE>
<PAGE>



























                                        *

                                       -3-
<PAGE>
<PAGE>


























                                        *

                                       -4-


WHEREVER CONFIDENTIAL  INFORMATION
IS OMITTED HEREIN (SUCH OMISSIONS
ARE DENOTED BY AN ASTERISK), SUCH
CONFIDENTIAL INFORMATION HAS BEEN
SUBMITTED SEPARATELY TO THE SECURITIES
AND EXCHANGE  COMMISSION PURSUANT TO
A REQUEST FOR  CONFIDENTIAL TREATMENT


              COMMON STOCK AND CONVERTIBLE NOTE PURCHASE AGREEMENT


     THIS COMMON STOCK AND CONVERTIBLE  NOTE PURCHASE  AGREEMENT  ("Agreement"),
dated  as of April  22,  1996,  by and  between  XOMA  CORPORATION,  a  Delaware
corporation having its principal executive office at 2910 7th Street,  Berkeley,
California 94710 (the "Company"),  and GENENTECH,  INC., a Delaware  corporation
having its principal  executive office at 460 Point San Bruno  Boulevard,  South
San Francisco, California 94080 (the "Purchaser").

                                    RECITALS

     A. The parties are entering  into a  Collaboration  Agreement,  dated as of
April 22, 1996 (the "Collaboration Agreement"),  relating to the development and
marketing of a monoclonal antibody.

     B. In connection with the Collaboration  Agreement, the parties desire that
the  Purchaser  (i) make an  investment  in the Company  through the purchase of
Common Stock,  $.0005 par value per share,  of the Company (the "Common  Stock")
and (ii) fund the  Company's  development  obligations  under the  Collaboration
Agreement by making certain  interest  bearing loans to the Company which are to
be evidenced by a Convertible  Subordinated  Note Agreement in the form attached
hereto as Exhibit A (the "Convertible Note").

     C. Upon the  happening  of  certain  events,  the  Convertible  Note  shall
automatically  convert into shares of a nonvoting convertible preferred stock of
the  Company  which,  in turn,  shall be  convertible  into Common  Stock.  Such
preferred stock (the "Preferred  Stock") shall have the rights,  preferences and
privileges  as  provided  in  the  Certificate  of  Designation  of  Convertible
Preferred Stock,  Series E,  substantially in the form attached as Schedule A to
the form of Convertible  Note attached hereto as Exhibit A (the  "Certificate of
Designation").

     NOW, THEREFORE,  in consideration of the foregoing and the mutual covenants
and promises set forth in this Agreement, the parties agree as follows:

     1. Sale and Purchase of Common Stock.  Subject to the terms and  conditions
hereof and in reliance upon the representations and warranties contained herein,
the  Company  will  issue  and sell to the  Purchaser  at the  Closing,  and the
Purchaser  will  purchase from the Company at the Closing,  1,500,000  shares of
Common Stock (the  "Shares") for an aggregate  purchase price of $ * hereinafter
referred to as the "Stock Purchase Price."



<PAGE>
<PAGE>



     2. Sale and Purchase of Convertible Note;  Loans.  Subject to the terms and
conditions  hereof  and in  reliance  upon the  representations  and  warranties
contained  herein,  the  Purchaser  will  lend  at the  Closing  the  $5,000,000
contemplated to be loaned pursuant to Section 7.1 of the Collaboration Agreement
as the initial loan under the Collaboration  Agreement (the "Initial Loan"), and
the  Purchaser  and the Company  will execute and deliver to the  Purchaser  the
Convertible  Note (with the  initial  $5,000,000  loan  recorded  on  Schedule B
thereto and designated as "Tranche A" thereunder) to evidence such initial loan.
Subsequent  to the  Closing,  the  Purchaser  will  from  time to time make such
additional  loans  as are  contemplated  by  Section  7.2  of the  Collaboration
Agreement  and such loans will be evidenced by  recording  the date,  amount and
designation (i.e.,  "Tranche B," "Tranche C," etc.) thereof on Schedule B to the
Convertible  Note as contemplated by the provisions of the Convertible  Note, it
being  understood and agreed by the parties that in the event the  Collaboration
Agreement  shall be terminated in accordance  with its terms the Purchaser shall
have no further  obligation to make any such additional loans from and after the
date of notice of any such termination.

     3.  The  Closing.  The  Closing  of the  purchase  and  sale of the  Shares
hereunder  and the making of the Initial  Loan and  delivery of the  Convertible
Note to evidence  such loan (the  "Closing")  shall take place at the offices of
the Purchaser, 460 Point San Bruno Boulevard,  South San Francisco,  California,
on April 22,  1996 at 8 a.m.,  local  time,  or on such other date at such other
time as is mutually  agreed  upon by the  parties  (the day on which the Closing
occurs is  referenced  to herein as the "Closing  Date").  At the  Closing,  the
Company shall deliver to the Purchaser (i) a certificate representing the Shares
and (ii) the Convertible Note, dated as of the Closing Date,  against receipt of
the Stock  Purchase  Price and the Initial Loan by wire transfer of  immediately
available funds to the order of the Company.

     4.  Representations  and  Warranties  of the  Company.  The Company  hereby
represents and warrants to the Purchaser as follows:

          (a)  Corporate  Power.  The Company is a corporation  duly  organized,
     validly  existing  and in good  standing  under  the  laws of the  State of
     Delaware and is qualified to do business as a foreign  corporation  in each
     jurisdiction  where failure to qualify would have a material adverse effect
     on the  business  or  properties  of the  Company.  The  Company  has  full
     corporate power and authority to own its property, to carry on its business
     as  presently  conducted  and to carry  out the  transactions  contemplated
     hereby.

          (b)  Authorization.  The Company has full corporate  power to execute,
     deliver and perform this  Agreement,  the  Collaboration  Agreement and the
     Convertible  Note,  and each  such  agreement  has been duly  executed  and
     delivered  by the  Company  and is  the  legal,  valid  and,  assuming  due
     execution by the Purchaser,  binding obligation of the Company, enforceable
     in accordance with its terms, subject to applicable bankruptcy, insolvency,
     moratorium,  reorganization  or similar laws  affecting  creditors'  rights
     generally, and to general equitable principles. The execution, delivery and
     performance by the Company of this Agreement,  the Collaboration  Agreement
     and the  Convertible  Note,  including  the  borrowing of amounts under the
     loans contemplated by Section 2 hereof and the issuance,  sale and delivery
     of the Shares, the Convertible Note, the Preferred Stock and the Conversion
     Shares (as  defined  in  Section  4(c)  below)  have been duly and  validly
     authorized by all necessary corporate action of the Company.



                                       -2-
<PAGE>
<PAGE>



          (c) Valid  Issuance of Common  Stock,  Convertible  Note and Preferred
     Stock. The Shares,  when issued,  sold and delivered in accordance with the
     terms  hereof  for  the  consideration   expressed  herein,  will  be  duly
     authorized,  validly issued,  fully paid and non-assessable,  and, based in
     part upon the  representations of the Purchaser in this Agreement,  will be
     issued in compliance with all applicable federal and state securities laws.
     The Convertible  Note,  when issued,  sold and delivered in accordance with
     the terms  hereof  for the  consideration  expressed  herein,  will be duly
     authorized and validly issued,  and, based in part upon the representations
     of the Purchaser in this  Agreement,  will be issued in compliance with all
     applicable  federal and state securities  laws. The Preferred Stock,  after
     giving  effect to the filing of the  Certificate  of  Designation  with the
     Secretary of State of the State of Delaware as  contemplated  by Section 8,
     and any shares of Common Stock  issued upon  conversion  of such  Preferred
     Stock in accordance with the terms thereof (the "Conversion Shares"),  will
     be duly  authorized,  validly issued,  fully paid and  non-assessable  and,
     based in part upon the  representations of the Purchaser in this Agreement,
     will be  issued  in  compliance  with  all  applicable  federal  and  state
     securities laws.

          (d) Governmental Approvals.  Based in part on the representations made
     by the Purchaser in Sections 5 and 6, no authorization,  consent, approval,
     license,  exemption  of  or  filing  or  registration  with  any  court  or
     governmental   department,    commission,    board,   bureau,   agency   or
     instrumentality,  domestic or foreign,  under any applicable laws, rules or
     regulations  presently  in effect,  is or will be  necessary  to be made or
     obtained by the Company  for, or in  connection  with,  the  execution  and
     delivery of this Agreement,  the Collaboration Agreement or the Convertible
     Note or consummation of the transactions  contemplated hereby or thereby or
     performance  by the Purchaser of its  obligations  hereunder or thereunder,
     except for (i) the filing of the Certificate of Designation as contemplated
     by Section 8, (ii) such other  filings  under  applicable  securities  laws
     which will be made by the Company within the prescribed periods,  including
     the  filing  by the  Company  of a notice  under  Section  25102(f)  of the
     California Codes, as amended,  and the payment of any fee relating thereto,
     (iii)  any  of  the  foregoing  required  or  contemplated  to be  made  in
     accordance  with  Section  9 and  (iv)  any of the  foregoing  required  in
     connection with the conversion of the Preferred Stock.

          (e) Litigation.  Except as disclosed in the SEC Reports (as defined in
     Section 4(j) below),  there is no litigation or governmental  proceeding or
     investigation  pending  or, to the  knowledge  of the  Company,  threatened
     against the Company which would  materially  and  adversely  affect (i) the
     execution and delivery of this Agreement,  the  Collaboration  Agreement or
     the  Convertible  Note,  or (ii)  the  performance  by the  Company  of its
     obligations hereunder or thereunder.

          (f) Subsidiaries.  The Company has no active subsidiaries and does not
     otherwise  directly or indirectly  control any other business  entity.  The
     Company has furnished the Purchaser with true,  correct and complete copies
     of its  Amended  and  Restated  Certificate  of  Incorporation  and Bylaws,
     together with any amendments thereto as of the date hereof.

          (g) Absence of Certain Developments. Since the date of its most recent
     report filed with the Securities and Exchange Commission (the "Commission")
     pursuant to the  Securities  and Exchange Act of 1934, as amended from time
     to time  (such act,  together  with the rules and  regulations  promulgated
     thereunder,  the "Exchange Act"),  except as disclosed  therein,  there has
     been  no (i)  material  adverse  change  in  the  condition,  financial  or
     otherwise,


                                       -3-
<PAGE>
<PAGE>



     of the  Company  or its  assets,  liabilities,  properties,  business,
     operations  or prospects  generally,  (ii)  declaration,  setting  aside or
     payment of any dividend or other  distribution  with respect to the capital
     stock of the Company, or (iii) loss,  destruction or damage to any property
     of the Company,  whether or not  insured,  which has or may have a material
     adverse effect on the Company.

          (h) Absence of  Undisclosed  Liabilities.  Except as and to the extent
     reflected  or stated in the SEC Reports and except for the  issuance of the
     Company's Non-Voting Cumulative  Convertible Preferred Stock, Series D, the
     Company has no material accrued or contingent  liability of a type required
     to be reflected on a balance sheet in accordance  with  generally  accepted
     accounting  principles  or described in the footnotes  thereto,  other than
     liabilities  arising in the ordinary  course of its business  since the SEC
     Reports, arising out of any transaction or state of facts existing prior to
     the date hereof.

          (i) Non-Contravention.  The execution, delivery and performance by the
     Company of this Agreement,  the Collaboration Agreement and the Convertible
     Note (i) do not and will not  contravene  or conflict  with the Amended and
     Restated  Certificate of Incorporation or Bylaws of the Company and (ii) do
     not  contravene or conflict  with or, based in part on the  representations
     made by the Purchaser in Sections 5 and 6 and assuming  satisfaction of the
     requirements  referenced  in Section  4(d),  constitute  a violation of any
     provision of any law,  regulation,  judgment,  injunction,  order or decree
     binding  upon or  applicable  to the  Company,  or result in a breach of or
     constitute a default under any material  agreement of the Company  (whether
     upon notice or passage of time),  in any manner which would  materially and
     adversely  affect the  Purchaser's  rights or its  ability  to realize  the
     intended benefits to it under this Agreement,  the Collaboration  Agreement
     or the Convertible Note.

          (j)  Filings.  The  Company  has  filed  in a timely  manner,  and has
     delivered to the Purchaser copies of, the following  reports required to be
     filed with the Commission  under the Exchange Act: (i) the Company's annual
     report on Form 10-K for the fiscal year ended December 31, 1995, as amended
     by  Amendment  No. 1 on Form  10-K/A,  and (ii)  all of its  other  reports
     (including without limitation reports on Form 8-K),  statements,  schedules
     and  registration  statements  filed with the Commission since December 31,
     1995. As of its filing date, no such report or statement  filed pursuant to
     the  Exchange Act  contained  any untrue  statement  of a material  fact or
     omitted  to  state  any  material  fact  necessary  in  order  to make  the
     statements made therein, in the light of the circumstances under which they
     were made, not misleading.  The Company has also delivered to the Purchaser
     a copy  of the  Company's  preliminary  Proxy  Statement  (filed  with  the
     Commission on April 12, 1996)  prepared in connection  with its 1996 annual
     meeting of stockholders (such preliminary Proxy Statement and the Company's
     annual  report  on Form  10-K for the year  ended  December  31,  1995,  as
     amended, are referred to herein as the "SEC Reports").

          (k) No Brokers.  The Company has not directly or  indirectly  employed
     any broker,  finder or other person  (including any employee) that might be
     entitled to a fee,  commission or other  compensation upon the execution of
     this Agreement,  the Collaboration Agreement or the Convertible Note or the
     consummation  of the  transactions  contemplated  by  this  Agreement,  the
     Collaboration  Agreement or the Convertible Note for which the Purchaser or
     the Company is or may be liable.


                                       -4-
<PAGE>
<PAGE>




          (l)  Registration  Rights.  The  Company  is not,  and will not become
     during the term of this  Agreement,  a party to any contract,  agreement or
     understanding  providing  for  the  registration  of its  securities  under
     federal or state  securities  laws that  restricts,  limits,  prohibits  or
     conflicts  or  would  restrict,   limit,  prohibit  or  conflict  with  the
     registration rights granted to the Purchaser pursuant to Section 10 hereof.

     5.  Representations  and Warranties of the Purchaser.  The Purchaser hereby
represents and warrants to the Company as follows:

          (a) Corporate  Power.  The Purchaser is a corporation  duly organized,
     validly  existing  and in good  standing  under  the  laws of the  State of
     Delaware.  The Purchaser has full corporate power and authority to carry on
     its  business  as  presently  conducted  and to carry out the  transactions
     contemplated hereby.

          (b) Authorization.  The Purchaser has full corporate power to execute,
     deliver and perform this  Agreement,  the  Collaboration  Agreement and the
     Convertible  Note,  and each  such  agreement  has been duly  executed  and
     delivered  by the  Purchaser  and is the  legal,  valid and,  assuming  due
     execution by the Company, binding obligation of the Purchaser,  enforceable
     in accordance with its terms, subject to applicable bankruptcy, insolvency,
     moratorium,  reorganization  or similar laws  affecting  creditors'  rights
     generally, and to general equitable principles. The execution, delivery and
     performance by the Purchaser of this Agreement, the Collaboration Agreement
     and the  Convertible  Note,  including  the  purchase of the Shares and the
     loans  contemplated by Section 2 hereof  pursuant to the Convertible  Note,
     have been duly and validly authorized by all necessary  corporate action of
     the Purchaser.

          (c) Litigation.  There is no litigation or governmental  proceeding or
     investigation  pending or, to the  knowledge of the  Purchaser,  threatened
     against the Purchaser which would  materially and adversely  affect (i) the
     execution   and  delivery  by  the   Purchaser  of  this   Agreement,   the
     Collaboration Agreement or the Convertible Note, or (ii) the performance by
     the Purchaser of its obligations hereunder or thereunder.

          (d) No Brokers.  The Purchaser has not directly or indirectly employed
     any broker,  finder or other person  (including any employee) that might be
     entitled to a fee,  commission or other  compensation upon the execution of
     this Agreement,  the Collaboration Agreement or the Convertible Note or the
     consummation  of the  transactions  contemplated  by  this  Agreement,  the
     Collaboration  Agreement or the Convertible Note for which the Purchaser or
     the Company is or may be liable.


     6.  Compliance  with  Securities  Laws  and  Restrictions  on  Transfer  of
Securities.

          (a) The Purchaser hereby  represents and warrants to, and agrees with,
     the Company as follows:

               (i)  The  Purchaser   (A)  is  purchasing   the  Shares  and  the
          Convertible  Note  (including  the making of the Initial Loan and each
          subsequent   loan  pursuant  to  Section  7.2  of  the   Collaboration
          Agreement),  (B) will acquire the Preferred  Stock upon  conversion of
          the Convertible  Note (in the event of any such  conversion),  and (C)
          will


                                       -5-
<PAGE>
<PAGE>



          acquire the  Conversion  Shares upon  conversion of the Preferred
          Stock (in the event of any such conversion)  (the Shares,  Convertible
          Note,  Preferred  Stock and Conversion  Shares are referred to herein,
          collectively,  as the "Securities") for its own account for investment
          only and not with a view to any resale or distribution thereof, except
          pursuant to an effective  registration  statement under the Securities
          Act of 1933, as amended from time to time (such act, together with the
          rules and regulations promulgated  thereunder,  the "Securities Act"),
          covering the sale,  assignment or transfer or an opinion of counsel in
          form and substance  satisfactory to the Company that such registration
          is not required.

               (ii) The Purchaser  has received and  carefully  reviewed the SEC
          Reports,  and has had the opportunity to obtain and receive such other
          information  as it deems  necessary  to  understand  the  business and
          financial condition of the Company and to make the investment decision
          to purchase the Securities.

               (iii)  As an  investor  in  companies  in  the  biopharmaceutical
          industry and a participant  in such  industry,  the Purchaser has such
          knowledge and experience in financial and business  matters that it is
          capable  of  evaluating   the  merits  and  risks  of  the  investment
          represented  by the  Securities,  and it is able to bear the  economic
          risk of such investment.

               (iv) The Purchaser  understands that the Securities are being, or
          will be,  sold or issued  in a  transaction  which is exempt  from the
          registration  requirements  of the  Securities  Act by  reason  of the
          provisions of Section 4(2) of the Securities  Act (or Section  3(a)(9)
          of the  Securities  Act in the case of the  issuance of the  Preferred
          Stock and the  Conversion  Shares upon  conversion of the  Convertible
          Note and the Preferred Stock, respectively),  and that such Securities
          will be subject to transfer restrictions and must be held indefinitely
          unless  subsequently   registered  under  the  Securities  Act  or  an
          exemption from such registration is available.

               The certificates representing the Securities will be affixed with
          a legend reading as follows:

               "THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER
          THE  SECURITIES  ACT OF 1933 AND MAY NOT BE SOLD,  OFFERED  FOR  SALE,
          PLEDGED,  HYPOTHECATED,  ASSIGNED  OR  OTHERWISE  TRANSFERRED  IN  THE
          ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT UNDER SAID ACT COVERING
          THE  TRANSFER  OR  AN  OPINION  OF  COUNSEL  IN  FORM  AND   SUBSTANCE
          SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED."

               Except as set forth in  Section 14 hereof,  the  restrictions  on
          sale,  assignment and transfer of the Shares,  the Preferred Stock and
          the  Conversion  Shares  contained  in  this  Section  6(a)(iv)  shall
          terminate  at such time as there shall be delivered to the Company and
          the  Purchaser  an opinion of  counsel to the  Purchaser,  in form and
          substance  satisfactory to the Company, to the effect that, due to the
          lapse of time or  otherwise,  no  registration  of such  securities is
          required under the Securities Act in connection with any  distribution
          of such securities to the public in the United States.


                                       -6-
<PAGE>
<PAGE>



          In addition,  at any time after (A) the delivery of such opinion;
          (B) such  securities  are sold pursuant to and in  accordance  with an
          effective  registration  statement  under the  Securities Act covering
          such sale; or (C) the Purchaser  shall have delivered to the Company a
          written  undertaking,  executed by the Purchaser  and any  institution
          currently  executing or proposing to execute sales of such securities,
          to the effect  that such sales shall be made only in  compliance  with
          all applicable provisions of Rule 144 under the Securities Act (or any
          applicable  similar rule which may be promulgated  from time to time),
          the   Purchaser   shall  be  entitled  to  exchange  its   certificate
          representing  such securities (or any portion thereof as to which (A),
          (B) or (C) above applies) for new  certificates not bearing the legend
          set forth in Section 6(a)(iv).

          (b) The Purchaser  may only sell,  assign or transfer all or a portion
     of  the   Convertible   Note  to  a   wholly-owned   subsidiary  or  to  F.
     Hoffmann-LaRoche  Ltd or any of its Affiliates (as defined in Section 7(b))
     (the "Roche Affiliates") which are directly or indirectly  controlled by it
     (collectively,  with such Roche Affiliates, "Roche") (so long as Roche owns
     at least a  majority  of the  outstanding  Voting  Stock  (as such  term is
     defined in Section 7(a)) of the  Purchaser,  provided that (i), in the case
     of a wholly-owned subsidiary, such subsidiary agrees with the Purchaser and
     the Company in writing to rescind such  transaction  in the event it ceases
     to be a wholly-owned subsidiary of the Purchaser and agrees in writing with
     the Company to comply with all the provisions of this Agreement  applicable
     to the Purchaser and, in the case of the  Convertible  Note, to be bound by
     the  obligations of the "Lender"  thereunder  (including the  corresponding
     obligations  under the Collaboration  Agreement),  and (ii), in the case of
     Roche,  Roche  agrees  with the  Purchaser  and the  Company  in writing to
     rescind such transaction in the event it ceases to be the owner of at least
     a majority of the  outstanding  Voting Stock of the Purchaser and agrees in
     writing  with the  Company  to comply  with all of the  provisions  of this
     Agreement  applicable to the Purchaser and, in the case of the  Convertible
     Note, to be bound by the obligations of the "Lender" thereunder  (including
     the  corresponding   obligations   under  the   Collaboration   Agreement).
     Notwithstanding any such sale, assignment or transfer,  the Purchaser shall
     not be relieved of its obligations  hereunder or under the Convertible Note
     or the  Collaboration  Agreement.  The Purchaser  agrees that the Preferred
     Stock  shall not be sold,  assigned or  transferred  (either in whole or in
     part) to a third party who is not an Affiliate  (as such term is defined in
     Section  7(b)  hereof) and is not Roche,  except if as a condition  of such
     sale,  assignment or transfer the Preferred  Stock shall  automatically  be
     converted into Conversion Shares.

          (c)  Notwithstanding  any provision of this Agreement to the contrary,
     other than as permitted  by, and in  accordance  with,  the  provisions  of
     Section  6(b),  without  the prior  written  consent  of the  Company,  the
     Purchaser may not sell, assign,  convey,  pledge,  hypothecate or otherwise
     dispose of the Convertible Note (representing any and all loans outstanding
     as contemplated  by Section 2) or any interest  therein.  Accordingly,  the
     Convertible Note will be affixed with a legend reading as follows:

               "THE SECURITIES REPRESENTED HEREBY ARE SUBJECT TO RESTRICTIONS ON
          SALE, ASSIGNMENT OR TRANSFER PURSUANT TO THAT CERTAIN COMMON STOCK AND
          CONVERTIBLE  NOTE  PURCHASE  AGREEMENT,  DATED AS OF APRIL  22,  1996,
          BETWEEN  THE  COMPANY AND  GENENTECH,  INC.,  AND MAY NOT (NOR MAY ANY
          INTEREST THEREIN) BE SOLD, ASSIGNED, CONVEYED,


                                       -7-
<PAGE>
<PAGE>



          PLEDGED,  HYPOTHECATED  OR  OTHERWISE  DISPOSED  OF OTHER THAN IN
          ACCORDANCE WITH THE PROVISIONS THEREOF."

          (d) The Purchaser  understands that notations restricting the transfer
     of the Securities  will be made on the transfer  records of the Company and
     that a stop  transfer  order will be entered  with the  Company's  transfer
     agent.

          (e) None of the Securities  (nor any interest  therein) shall be sold,
     assigned  or  offered  except in  accordance  with the  provisions  of this
     Section 6.

     7. Additional Covenants of Purchaser Regarding Securities.

          (a)  Effectiveness  and  Termination.  The provisions of Sections 7(b)
     through 7(d) shall become effective at such time (if any), and from time to
     time, as the Purchaser and its Affiliates, taken together, own Voting Stock
     of the Company (which includes the Common Stock)  representing  ten percent
     (10%) or more of the total  outstanding  Voting Stock of the  Company,  and
     shall continue in effect until the earlier of (i) the fifteenth anniversary
     of the date of this  Agreement or (ii) such time as the  Purchaser  and its
     Affiliates,  taken  together,  own less than ten percent (10%) of the total
     outstanding Voting Stock of the Company,  provided that such Sections shall
     again become  effective if, and at such time, and from time to time, as the
     Purchaser and its Affiliates, taken together, own such percentage of Voting
     Stock of the Company within the fifteen year period  commencing on the date
     hereof.  For purposes of this Agreement,  the term "Voting Stock" means the
     equity  securities  (as such term is used in the  Exchange  Act) having the
     ordinary  power to vote in the election of directors of the issuer  thereof
     (other  than  securities  having  such power only upon the  happening  of a
     contingency).  For  purposes of this  Section 7, owned  Voting  Stock shall
     include Voting Stock, securities directly or indirectly convertible into or
     exchangeable  for Voting Stock  (whether or not subject to a  contingency),
     and rights to acquire any of the foregoing. The provisions of Sections 7(b)
     through 7(d) shall have no effect  unless and until they become  effective,
     and only so long as they are  effective,  pursuant  to this  Section  7(a),
     other than for purposes of defining  certain  terms used  elsewhere in this
     Agreement.  Notwithstanding  any  provision  hereof to the  contrary,  this
     Section 7 shall  not apply to any  Preferred  Stock,  Shares or  Conversion
     Shares assigned,  sold or transferred in accordance with Section  6(a)(iv),
     and the legend required to be affixed to the certificates representing such
     shares pursuant to Section 7(d) shall be removed upon any such  assignment,
     sale or transfer of such shares.

          (b)  Additional  Stock  Purchases by Purchaser.  The Purchaser  hereby
     agrees that  neither the  Purchaser  nor any of its  Affiliates  nor anyone
     acting on its or their behalf will acquire any equity  securities  (as such
     term is used in the  Exchange  Act) of the Company  without  the  Company's
     prior  written  approval,  except  as  contemplated  by this  Agreement  or
     pursuant to the Convertible  Note or the Preferred  Stock.  For purposes of
     this Agreement,  the term "Affiliate"  means, when used with respect to any
     specified  person,  any other person  directly or indirectly  controlled by
     such specified person. For the purposes of this definition, "control," when
     used with respect to any person,  means the power to direct the  management
     and policies of such person,  directly or indirectly,  whether  through the
     ownership of voting  securities,  by contract or  otherwise,  and the terms
     "affiliated" and "controlled"  have meanings  correlative to the foregoing.
     The  obligations of this Section 7(b) shall  terminate if another person or
     group has acquired Voting Stock of the Company (or rights to acquire Voting
     Stock


                                       -8-
<PAGE>
<PAGE>



     of the Company) which results in such person or group owning or having
     the right to acquire  Voting  Stock of the Company  with  aggregate  voting
     power of more than 50% of the total  voting  power of the  Company  then in
     effect.

          (c)  Solicitation  of  Proxies;  Participation  in  Control  Contests.
     Without the Company's  prior written  consent,  (i) the Purchaser shall not
     solicit proxies with respect to any Voting Stock of the Company,  nor shall
     it become a "participant" in any "election contest" (as such terms are used
     under  Regulation  14A of the  Exchange  Act)  relating to the  election of
     directors of the Company; and (ii) the Purchaser shall not, and shall cause
     its  Affiliates  not to (and the  Purchaser and such  Affiliates  shall not
     together or in conjunction with third parties who are not Affiliates form a
     "group"  (as used  under  Regulation  13D/G of the  Exchange  Act),  act in
     concert, or encourage other persons to), directly or indirectly, acquire or
     offer to acquire, seek, propose or agree to acquire,  whether by means of a
     purchase,  agreement,  business combination or any other manner, beneficial
     ownership of any securities or assets of the Company  (including options to
     acquire such ownership) seeking or proposing to influence,  advise,  change
     or control the  management,  Board of Directors,  governing  instruments or
     policies or affairs of the Company.  Subject only to this Section 7(c), the
     Purchaser  shall be  entitled  to vote its  shares of  Voting  Stock of the
     Company in its discretion.

          (d)  Restrictive  Legends.  In  addition  to any  restrictive  legends
     required by Section 6,  subject to the  penultimate  and last  sentences of
     Section 7(a), the certificates  representing the Securities will be affixed
     with a legend reading as follows:

               "THE  SECURITIES  REPRESENTED  HEREBY (AND,  IF  APPLICABLE,  ANY
          SECURITIES  ISSUED  UPON  CONVERSION  THEREOF)  MAY BE  SUBJECT TO THE
          RESTRICTIONS  SET FORTH IN THAT CERTAIN  COMMON STOCK AND  CONVERTIBLE
          NOTE  PURCHASE  AGREEMENT,  DATED AS OF APRIL 22,  1996,  BETWEEN  THE
          COMPANY AND GENENTECH, INC."

     8. Additional Covenants of the Company.

          (a) Filing of Certificate of Designation.  The Company shall file with
     the  Secretary  of  State of the  State  of  Delaware  the  Certificate  of
     Designation not later than the Closing Date.

          (b) Stockholders' Rights Plan. The Company agrees that, as long as the
     Purchaser is  substantially in compliance with the terms of this Agreement,
     the Collaboration Agreement and the Securities,  (i) the Purchaser will not
     be  declared  an Adverse  Person for  purposes  of the  Stockholder  Rights
     Agreement  dated as of October  27,  1993  between  the  Company  and First
     Interstate  Bank of California,  as rights agent (the "Rights  Agreement"),
     and (ii) the  Company  will take all  commercially  reasonable  efforts  to
     redeem the preferred stock purchase  rights which may be distributed  under
     the Rights  Agreement  if the  Purchaser  becomes an  Acquiring  Person (as
     defined in the Rights Agreement) and the Stock Acquisition Date (as defined
     in the Rights Agreement) has occurred.

     9. Conditions to Closing.


                                       -9-
<PAGE>
<PAGE>




          (a)  Conditions  to  Purchaser's   Obligations  at  the  Closing.  The
     Purchaser's  obligation  to  purchase  and pay for the  Shares and make the
     Initial  Loan at the Closing is subject to the  fulfillment  on or prior to
     the Closing of the  following  conditions,  any one or more of which may be
     waived in whole or in part by the Purchaser:

               (i)  Compliance  with Laws.  At the Closing,  the purchase of the
          Shares hereunder and the loans to be made by the Purchaser pursuant to
          the  Convertible  Note  shall  be  legally  permitted  by all laws and
          regulations to which the Purchaser or the Company is subject.

               (ii) Representations and Warranties.  Each of the representations
          and warranties of the Company set forth in Section 4 shall be true and
          correct as if made on the Closing Date.

               (iii) Performance.  The Company shall have performed and complied
          with all  agreements,  obligations  and  conditions  contained in this
          Agreement  that are required to be performed or complied with by it on
          or before the Closing Date, including delivery of the Shares.

               (iv)   Compliance   Certificate.   The  Senior  Vice   President,
          Operations  of the  Company  shall  deliver  to the  Purchaser  on the
          Closing Date a certificate certifying that the conditions set forth in
          clauses (ii) and (iii) of this Section 9(a) have been fulfilled.

               (v)  Other  Agreements.  The  Company  shall  have  executed  and
          delivered  to  the  Purchaser  the  Collaboration  Agreement  and  the
          Convertible Note.

               (vi) Consents.  The Company and the Purchaser shall have obtained
          all consents  (including all  governmental  and  regulatory  consents,
          approvals,  or  authorizations  required in connection  with the valid
          execution and delivery of this Agreement,  the Collaboration Agreement
          and the Convertible  Note),  permits and waivers necessary or required
          to be obtained on or prior to the Closing Date for consummation of the
          transactions contemplated hereby.

               (vii) Opinion of Counsel to the Company. The Purchaser shall have
          received  from  Cahill  Gordon  &  Reindel,  special  counsel  for the
          Company, an opinion dated as of the Closing Date, substantially in the
          form set forth in Exhibit B attached hereto.

               (viii)  Proceedings  and  Documents.   All  corporate  and  other
          proceedings  in  connection  with  the  transactions  contemplated  in
          connection  with the  purchase of the Shares and the Initial  Loan and
          all  documents   incident  thereto  (including  the  issuance  of  the
          Preferred  Stock  and  the  Conversion  Shares)  shall  be  reasonably
          satisfactory   in  form  and   substance  to  the  Purchaser  and  the
          Purchaser's counsel, and they shall have received all such counterpart
          original and  certified or other copies of such  documents as they may
          reasonably request.



                                      -10-
<PAGE>
<PAGE>



          (b) Conditions to Company's  Obligations at the Closing. The Company's
     obligation  to sell and  issue the  Shares  and  execute  and  deliver  the
     Convertible  Note at the Closing is subject to the  fulfillment on or prior
     to the Closing of the following conditions, any one or more of which may be
     waived in whole or in part by the Company:

               (i)  Compliance  with Laws.  At the Closing,  the purchase of the
          Shares  hereunder and the loans to be made by the  Purchaser  shall be
          legally  permitted by all laws and  regulations to which the Purchaser
          or the Company is subject.

               (ii) Representations and Warranties.  Each of the representations
          and warranties of the Purchaser set forth in Sections 5 and 6 shall be
          true and correct as if made on the Closing Date.

               (iii)  Payment  of  Purchase  Price.  The  Purchaser  shall  have
          delivered to the Company  payment of the Stock  Purchase Price and the
          Initial Loan in accordance with Section 3 hereof.

               (iv) Performance. The Purchaser shall have performed and complied
          with all  agreements,  obligations  and  conditions  contained in this
          Agreement  that are required to be  performed  or complied  with on or
          before the Closing Date.

               (v) Other  Agreements.  The  Purchaser  shall have  executed  and
          delivered  to  the  Company  the   Collaboration   Agreement  and  the
          Convertible Note.

               (vi) Consents.  The Company and the Purchaser shall have obtained
          all consents  (including all  governmental  and  regulatory  consents,
          approvals,  or  authorizations  required in connection  with the valid
          execution and delivery of this Agreement,  the Collaboration Agreement
          and the Convertible  Note),  permits and waivers necessary or required
          to be obtained on or prior to the Closing Date for consummation of the
          transactions contemplated hereby.

               (vii)   Proceedings  and  Documents.   All  corporate  and  other
          proceedings  in  connection  with  the  transactions  contemplated  in
          connection  with the  purchase of the Shares and the Initial  Loan and
          all  documents   incident  thereto  (including  the  issuance  of  the
          Preferred  Stock  and  the  Conversion  Shares)  shall  be  reasonably
          satisfactory  in form and  substance to the Company and the  Company's
          counsel,  and they shall have received all such  counterpart  original
          and certified or other copies of such documents as they may reasonably
          request.

     10. Registration Rights.

          (a) Certain  Definitions.  As used in this  Agreement,  the  following
     terms shall have the following respective meanings:

          "Holder" shall mean the Purchaser or transferee of the Purchaser which
     is  a  holder  of  Registrable  Securities  and  acquired  such  shares  in
     accordance with Section 6(b).



                                      -11-
<PAGE>
<PAGE>



     "Prospectus"  shall  mean  the  prospectus  included  in  any  Registration
Statement   (including,   without   limitation,   a  prospectus  that  discloses
information  previously  omitted from a prospectus filed as part of an effective
registration  statement in reliance upon Rule 430A  promulgated  pursuant to the
Securities Act), as amended or supplemented by any prospectus  supplement,  with
respect  to  the  terms  of  the  offering  of any  portion  of the  Registrable
Securities covered by such Registration Statement,  and all other amendments and
supplements to any such prospectus, including post-effective amendments, and all
materials  incorporated  by reference or deemed to be incorporated by reference,
if any, in such prospectus.

     "Registrable  Securities" shall mean (i) the Shares issued to the Purchaser
at the Closing, (ii) the Conversion Shares of the Company issued upon conversion
of the Preferred Stock issued upon conversion of the Convertible  Note and (iii)
any Common Stock of the Company  issued in respect of such shares as a result of
any stock split, stock dividend or recapitalization.

     "Registration  Expenses" shall mean all expenses incurred by the Company in
complying with Sections 10(b) through (d), including,  without  limitation,  all
registration,  qualification and filing fees,  printing  expenses,  escrow fees,
fees and  disbursements of counsel for the Company,  blue sky fees and expenses,
and the  expense of any  special  audits  incident  to or  required  by any such
registration (but excluding the compensation of regular employees of the Company
which shall be paid in any event by the Company).

     "Registration  Statement"  shall  mean any  registration  statement  of the
Company that covers any of the Registrable Securities pursuant to the provisions
of this Agreement, including the Prospectus,  amendments and supplements to such
registration   statement  or  Prospectus,   including  pre-  and  post-effective
amendments,  all exhibits thereto, and all material incorporated by reference or
deemed to be incorporated by reference, if any, in such registration statement.

          (b) Shelf Registration Statements.

               (i) The  Company  agrees  to file with the  Commission,  promptly
          following  the  Closing,  but in no event later than 45 days after the
          Closing,  a  Registration  Statement  for an  offering to be made on a
          continuous  basis pursuant to Rule 415 of the Securities Act (a "Shelf
          Registration   Statement")   covering   all  of  the  Shares  and  any
          Registrable  Securities  issued in respect of such Shares.  Such Shelf
          Registration  Statement  shall be on Form S-3 under the Securities Act
          or another appropriate form permitting registration of such Shares and
          any Registrable Securities issued in respect of such Shares for resale
          by the Holder in the manner or manners  reasonably  designated  by the
          Holder.  The Company shall use its commercially  reasonable efforts to
          cause such  Shelf  Registration  Statement  to be  declared  effective
          pursuant to the Securities  Act as promptly as  practicable  following
          the filing  thereof and to keep it  continuously  effective  under the
          Securities  Act  until  termination  of such  obligation  pursuant  to
          Section 10(f)(i).

               (ii) The  Company  agrees to file with the  Commission,  promptly
          following  the  Conversion  Date  (as  such  term  is  defined  in the
          Convertible Note Agreement) first


                                      -12-
<PAGE>
<PAGE>



          occurring,  but  in  no  event  later  than  45  days  after  the
          Conversion Date, a Shelf  Registration  Statement  covering all of the
          Conversion Shares and any Registrable  Securities issued in respect of
          such Conversion Shares. Such Shelf Registration  Statement shall be on
          Form  S-3  under  the  Securities  Act  or  another  appropriate  form
          permitting  registration of such Conversion Shares and any Registrable
          Securities  issued in respect of such Conversion  Shares for resale by
          the  Holder in the  manner or  manners  reasonably  designated  by the
          Holder.  The Company shall use its commercially  reasonable efforts to
          cause such  Shelf  Registration  Statement  to be  declared  effective
          pursuant to the Securities  Act as promptly as  practicable  following
          the filing  thereof and to keep it  continuously  effective  under the
          Securities  Act  until  termination  of such  obligation  pursuant  to
          Section 10(f)(ii).

          (c) Certain Notices; Suspension of Sales. The Holder agrees that, upon
     receipt of any notice from the Company of the happening of any event of the
     kind  described  in any of clauses (w)  through  (z) of Section  10(d)(iii)
     (with,  if requested by the Holder,  a  description  in  reasonable  detail
     thereof),  the such Holder will  forthwith  discontinue  disposition of the
     Registrable Securities covered by such Registration Statement or Prospectus
     until  the  Holder's  receipt  of  copies of the  supplemented  or  amended
     Prospectus  contemplated  by  Section  10(d)(v),  or until it is advised in
     writing  (the  "Advice")  by the  Company  that  the use of the  applicable
     Prospectus may be resumed,  and, in either case, has received copies of any
     additional or  supplemental  filings that are  incorporated or deemed to be
     incorporated by reference in such Prospectus.

          (d)  Registration   Procedures.   In  connection  with  the  Company's
     registration  obligations  under  Section  10(b),  the  Company  shall with
     respect to each Shelf Registration Statement:

               (i)  Prepare  and  file  with  the  Commission  such  amendments,
          including post-effective amendments, to each Registration Statement as
          may be  necessary  to keep such  Registration  Statement  continuously
          effective for the applicable time period set forth in, and subject to,
          Section 10(b);  cause the related Prospectus to be supplemented by any
          required  Prospectus  supplement,  and as so  supplemented to be filed
          pursuant to Rule 424 (or any similar  provisions  then in force) under
          the   Securities  Act  and  the  Exchange  Act  with  respect  to  the
          disposition of all securities  covered by such Registration  Statement
          during  such  period  in  accordance  with  the  intended  methods  of
          disposition by the Holder set forth in such Registration  Statement as
          so amended or in such  Prospectus  as so  supplemented,  provided such
          Holder complies with the information requirements of Section 10(h).

               (ii) Deliver to the Holder, without charge, as many copies of the
          Prospectus or  Prospectuses  (including  each form of prospectus)  and
          each  amendment or  supplement  thereto it reasonably  requests;  and,
          subject to Section 10(c),  the Company  hereby  consents to the use of
          such Prospectus and each amendment or supplement thereto by the Holder
          in  connection  with  the  offering  and sale of the  covered  Shares,
          Conversion  Shares  or  Registrable  Securities,  as the  case may be,
          covered by such  Prospectus  and any amendment or supplement  thereto,
          provided that no Holder shall be entitled to use the Prospectus unless
          and until such Holder shall have furnished to the Company any required
          information pursuant to Section 10(h).


                                      -13-
<PAGE>
<PAGE>




               (iii) Notify the Holder (v) when a Prospectus  or any  Prospectus
          supplement or  post-effective  amendment is proposed to be filed, and,
          with  respect  to  a  Registration  Statement  or  any  post-effective
          amendment,  when the same has become effective,  (w) of any request of
          the  Commission or any other Federal or state  governmental  authority
          for amendments or  supplements to a Registration  Statement or related
          Prospectus or for additional  information related thereto,  (x) of the
          issuance by the Commission, any state securities commission, any other
          governmental  agency  or  any  court  of  any  stop  order,  order  or
          injunction  suspending or enjoining the use or the  effectiveness of a
          Registration  Statement or the initiation of any  proceedings for that
          purpose,  (y) of the receipt by the Company of any  notification  with
          respect to the  suspension  of the  qualification  or  exemption  from
          qualification of any of the Shares,  Conversion  Shares or Registrable
          Securities,  as the case may be, for sale in any jurisdiction,  or the
          initiation or threatening of any proceeding for such purpose,  and (z)
          of the existence of any fact and the happening of any event that makes
          any  statement  made  in  such   Registration   Statement  or  related
          Prospectus or any document  incorporated  or deemed to be incorporated
          therein by reference untrue in any material respect,  or that requires
          the making of any changes in such Registration  Statement,  Prospectus
          or document so that in the case of the Registration Statement, it will
          not contain any untrue  statement of a material  fact or omit to state
          any material fact  required to be stated  therein or necessary to make
          the  statements  therein not  misleading  and that, in the case of the
          Prospectus, such Prospectus will not contain any untrue statement of a
          material fact or omit to state any material fact required to be stated
          therein or necessary to make the statements  therein,  in light of the
          circumstances under which they were made, not misleading.

               (iv) Use its commercially reasonable efforts (which shall include
          appropriate  responses to any requests of the type described in clause
          (w) of Section  10(d)(iii))  to avoid the  issuance of, or, if issued,
          obtain the withdrawal of any order  enjoining or suspending the use or
          effectiveness  of a  Registration  Statement  or  the  lifting  of any
          suspension of the qualification  (or exemption from  qualification) of
          any  of  the   covered   Registrable   Securities   for  sale  in  any
          jurisdiction, at the earliest practicable moment.

               (v) Upon the occurrence of any event  contemplated  by clause (z)
          of Section  10(d)(iii),  as  promptly as  practicable  but in no event
          later than 60 days  thereafter,  prepare a  supplement  or  amendment,
          including,  if  appropriate,   a  post-effective  amendment,  to  each
          Registration  Statement or a supplement  to the related  Prospectus or
          any  document  incorporated  or deemed to be  incorporated  therein by
          reference, and file any other required document so that, as thereafter
          delivered,  such Prospectus will not contain an untrue  statement of a
          material  fact or omit to state a material  fact required to be stated
          therein or necessary to make the statements  therein,  in light of the
          circumstances   under   which   they  were   made,   not   misleading.
          Notwithstanding anything herein to the contrary,  nothing herein shall
          require  the  Company  to  prepare  and file any  such  supplement  or
          amendment if the Company shall  determine in its  reasonable  judgment
          that  compliance  with  the  requirements  hereof  would  require  the
          disclosure  of  non-public   material  corporate   developments,   the
          disclosure of which in the reasonable judgment of the Company would be
          adverse to the interests of the Company,  and the  obligations  of the
          Company to prepare and file


                                      -14-
<PAGE>
<PAGE>



          any such  supplements or amendments shall be suspended until such
          time as such non-public  developments  otherwise become publicly known
          or announced or would not be required to be so disclosed in connection
          therewith,  provided  that if as a  consequence  of any  delay  in the
          filing of any  supplement or amendment,  the Holder is prevented  from
          effecting sales under the Registration  Statement for more than thirty
          (30)  consecutive  days,  if  requested by the Holder,  the  Company's
          determination  shall have been  confirmed  by a  determination  by the
          Board of Directors of the Company.

               (vi) Use its  commercially  reasonable  efforts  to  register  or
          qualify,   or  cooperate  with  the  Holder  in  connection  with  the
          registration or qualification  (or exemption from such registration or
          qualification),  of  the  Shares,  Conversion  Shares  or  Registrable
          Securities,  as the  case  may  be,  for  offer  and  sale  under  the
          securities  or Blue Sky laws of such  jurisdictions  within the United
          States as the Holder  reasonably  requests in writing,  keep each such
          registration  or  qualification  (or  exemption  therefrom)  effective
          during the period such  Registration  Statement is required to be kept
          effective  and do any  and  all  other  acts or  things  necessary  or
          advisable  to enable  the  disposition  in such  jurisdictions  of the
          Shares,  Conversion Shares or Registrable Securities,  as the case may
          be,  covered  by  the  applicable  Registration  Statement;  provided,
          however,  that the Company shall not be required to qualify  generally
          to do business in any  jurisdiction  where it is not then so qualified
          or take any action that would subject it to general service of process
          in any such  jurisdiction  where it is not then so  subject or subject
          the Company to any tax in any such  jurisdiction  where it is not then
          so subject.

               (vii)  Comply  with  applicable  rules  and  regulations  of  the
          Commission  and  make  generally  available  to its  security  holders
          earning  statements  satisfying the provisions of Section 11(a) of the
          Securities   Act  and  Rule  158   thereunder  (or  any  similar  rule
          promulgated under the Securities Act), no later than 60 days after the
          end of any  12-month  period (or 90 days after the end of any 12-month
          period if such period is a fiscal  year),  commencing on the first day
          of the first fiscal quarter after the effective date of a Registration
          Statement,  which statement  shall cover said period,  consistent with
          the requirements of Rule 158.

               (viii)  List  all  Shares,   Conversion  Shares  and  Registrable
          Securities  covered by such  Registration  Statement on any securities
          exchange  on which the Common  Stock is then listed or  authorize  for
          quotation on the National  Association of Securities Dealers Automated
          Quotation System  ("Nasdaq") or the Nasdaq National Market all Shares,
          Conversion   Shares  and  Registrable   Securities   covered  by  such
          Registration  Statement if the Common Stock is then so authorized  for
          quotation.

          (e) Expenses of Registration.  All Registration  Expenses  incurred in
     connection  with  any  registration,  qualification  or  compliance  by the
     Company  pursuant to Sections 10(b),  (c) or (d) of this Agreement shall be
     borne by the Company.

          (f) Termination of Registration Rights.

               (i) The  registration  obligations  of the  Company  pursuant  to
          Sections  10(b) through (d) of this  Agreement  shall  terminate  with
          respect to the Shelf Registration


                                      -15-
<PAGE>
<PAGE>



          Statement  contemplated by Section  10(b)(i) at the time at which
          all  of the  Shares,  Conversion  Shares  and  Registrable  Securities
          required  to be covered  by such  Registration  Statement  can be sold
          within  a  given  three-month   period  without  compliance  with  the
          registration  requirements  of the Securities Act pursuant to Rule 144
          or other applicable  exemption supported by a written opinion of legal
          counsel for the Company which shall be reasonably satisfactory in form
          and substance to legal counsel for Holder.

               (ii) The  registration  obligations  of the  Company  pursuant to
          Sections  10(b) through (d) of this  Agreement  shall  terminate  with
          respect to the Shelf  Registration  Statement  contemplated by Section
          10(b)(ii)  at the  time at  which  all of the  Registrable  Securities
          required  to be covered  by such  Registration  Statement  may be sold
          within  a  given  three-month   period  without  compliance  with  the
          registration  requirements  of the Securities Act pursuant to Rule 144
          or other applicable  exemption supported by a written opinion of legal
          counsel for the Company which shall be reasonably satisfactory in form
          and substance to legal counsel for Holder.

          (g) Indemnification.

               (i) The Company  agrees to  indemnify  and hold  harmless (A) the
          Holder,  (B) each person,  if any, who controls (within the meaning of
          Section 15 of the  Securities  Act or Section 20 of the Exchange  Act)
          the Holder  (any of the  persons  referred to in this clause (B) being
          hereinafter  referred  to as a  "controlling  person"),  and  (C)  the
          respective officers, directors,  partners, employees,  representatives
          and  agents of the  Holder,  or any  controlling  person  (any  person
          referred to in clause (A), (B) or (C) may  hereinafter  be referred to
          as an  "Indemnified  Person"),  from and  against  any and all losses,
          claims,  damages,  liabilities,  expenses and judgments  caused by any
          untrue  statement  or alleged  untrue  statement  of a  material  fact
          contained  in  any  Registration  Statement,  Prospectus  or  form  of
          Prospectus  or in  any  amendment  or  supplement  thereto  or in  any
          preliminary Prospectus,  or caused by any omission or alleged omission
          to state  therein a material  fact  required  to be stated  therein or
          necessary  to  make  the  statements  therein  (in  the  case  of  any
          Prospectus or form of Prospectus  or supplement  thereto,  in light of
          the circumstances  under which they were made) not misleading,  except
          insofar as such  losses,  claims,  damages,  liabilities,  expenses or
          judgments  are caused by any such  untrue  statement  or  omission  or
          alleged untrue statement or omission based upon  information  relating
          to any Indemnified Person furnished in writing to the Company by or on
          behalf of such Indemnified Person expressly for use therein;  provided
          that the foregoing  indemnity with respect to any Prospectus shall not
          inure to the  benefit of any  Indemnified  Person from whom the person
          asserting  such losses,  claims,  damages,  liabilities,  expenses and
          judgments purchased securities if such untrue statement or omission or
          alleged  untrue  statement  or  omission  made in such  Prospectus  is
          eliminated  or remedied by an  amendment or  supplement  thereto and a
          copy of such amended or  supplemented  Prospectus  shall not have been
          furnished to such person in a timely manner due to the wrongful action
          or wrongful inaction of such Indemnified  Person,  whether as a result
          of negligence or otherwise.



                                      -16-
<PAGE>
<PAGE>



               (ii) In case any action shall be brought  against any Indemnified
          Person,  based upon any Registration  Statement or any such Prospectus
          or any  amendment  or  supplement  thereto  and with  respect to which
          indemnity may be sought against the Company,  such Indemnified  Person
          shall  promptly  notify the Company in writing  and the Company  shall
          assume  the  defense  thereof,  including  the  employment  of counsel
          reasonably  satisfactory to such Indemnified Person and payment of all
          reasonable fees and expenses.  Any  Indemnified  Person shall have the
          right to employ separate counsel in any such action,  but the fees and
          expenses of such counsel  shall be at the expense of such  Indemnified
          Person,  unless (A) the  employment  of such  counsel  shall have been
          specifically  authorized  in writing by the  Company,  (B) the Company
          shall have failed to assume the defense and employ counsel or (C) such
          Indemnified  Person or Persons shall have been advised by counsel that
          there may be a conflict  between  the  positions  of the  indemnifying
          party or parties and of the indemnified party or parties in conducting
          the  defense of such action or  proceeding  or that there may be legal
          defenses  available to such  Indemnified  Person or Persons  different
          from or in addition to those  available to the  indemnifying  party or
          parties (in which case the Company  shall not have the right to assume
          the defense of such action on behalf of such Indemnified  Person),  it
          being understood,  however,  that the Company shall not, in connection
          with any one such  action or  separate  but  substantially  similar or
          related  actions  in the  same  jurisdiction  arising  out of the same
          general  allegations  or  circumstances,  be liable for the reasonable
          fees and  expenses of more than one  separate  firm of  attorneys  (in
          addition to any local counsel) for all such Indemnified Persons, which
          firm shall be designated in writing by such Indemnified  Persons.  The
          Company  shall not be liable  for any  settlement  of any such  action
          effected without its written consent,  but if settled with the written
          consent of the  Company,  the  Company  agrees to  indemnify  and hold
          harmless any Indemnified Person from and against any loss or liability
          by reason of such settlement. No indemnifying party shall, without the
          prior written consent of the Indemnified Person, effect any settlement
          of any  pending  or  threatened  proceeding  in  respect  of which any
          Indemnified  Person is or could have been a party and indemnity  could
          have been sought  hereunder by such  Indemnified  Person,  unless such
          settlement  includes  an  unconditional  release  of such  Indemnified
          Person from all  liability  on claims  that are the subject  matter of
          such proceeding.

               (iii) In connection with any Registration  Statement in which the
          Holder is participating, the Holder agrees, severally and not jointly,
          to  indemnify  and hold  harmless  the  Company,  its  directors,  its
          officers and any person  controlling the Company within the meaning of
          Section 15 of the Securities Act or Section 20 of the Exchange Act, to
          the same extent as the  foregoing  indemnity  from the Company to each
          Indemnified Person but only with reference to information  relating to
          such  Indemnified  Person furnished in writing by or on behalf of such
          Indemnified  Person expressly for use in such Registration  Statement.
          In case any action shall be brought  against the  Company,  any of its
          directors,  any such  officer or any person  controlling  the  Company
          based on such Registration Statement and in respect of which indemnity
          may be sought against any Indemnified  Person,  the Indemnified Person
          shall have the rights and duties given to the Company  (except that if
          the Company shall have assumed the defense  thereof,  such Indemnified
          Person shall not be required to do so, but may employ separate counsel
          therein but the fees and expenses of such counsel


                                      -17-
<PAGE>
<PAGE>



          shall be at the  expense  of such  Indemnified  Person),  and the
          Company,  its directors,  any such officers and any person controlling
          the Company shall have the rights and duties given to the  Indemnified
          Person by Section 10(g)(ii).

               (iv) If the indemnification provided for in this Section 10(g) is
          unavailable to an indemnified party in respect of any losses,  claims,
          damages, liabilities,  expenses or judgments referred to therein, then
          each  indemnifying  party,  in lieu of indemnifying  such  Indemnified
          Person,  shall  contribute  to the  amount  paid  or  payable  by such
          Indemnified  Person  as a  result  of such  losses,  claims,  damages,
          liabilities,   expenses  and  judgments  in  such   proportion  as  is
          appropriate to reflect the relative fault of the Company and each such
          Indemnified  Person in  connection  with the  statements  or omissions
          which resulted in such losses, claims, damages, liabilities,  expenses
          or judgments, as well as any other relevant equitable  considerations.
          The  relative  fault of the Company and each such  Indemnified  Person
          shall be determined  by reference to, among other things,  whether the
          untrue or alleged untrue  statement of a material fact or the omission
          to state a  material  fact  relates  to  information  supplied  by the
          Company or such Indemnified  Person and the parties'  relative intent,
          knowledge, access to information and opportunity to correct or prevent
          such statement or omission.

               The  Company  and the Holder  agree that it would not be just and
          equitable  if  contribution  pursuant to this Section  10(g)(iv)  were
          determined by pro rata allocation (even if the Indemnified Person were
          treated  as one  entity for such  purpose)  or by any other  method of
          allocation which does not take account of the equitable considerations
          referred to in the immediately preceding paragraph. The amount paid or
          payable by an  Indemnified  Person as a result of the losses,  claims,
          damages,  liabilities,  expenses  or  judgments  referred  to  in  the
          immediately preceding paragraph shall be deemed to include, subject to
          the  limitations  set  forth  above,   any  legal  or  other  expenses
          reasonably  incurred  by such  indemnified  party in  connection  with
          investigating  or defending any such action or claim. No person guilty
          of fraudulent  misrepresentation  (within the meaning of Section 11(f)
          of the  Securities  Act) shall be  entitled to  contribution  from any
          person who was not guilty of such fraudulent misrepresentation.

          (h)  Information  by Holder.  The Holder shall  furnish to the Company
     such information regarding such Holder and any distribution proposed by the
     Holder as the  Company  may  request in writing or as shall be  required in
     connection with any registration,  qualification or compliance  referred to
     in this Agreement.

          (i) Rule 144 Reporting.  With a view to making available to the Holder
     the benefits of certain rules and  regulations of the Commission  which may
     permit  the  sale of the  Shares,  Conversion  Shares  and the  Registrable
     Securities to the public  without  registration,  the Company agrees to use
     commercially  reasonable  efforts to (a) make and keep  public  information
     available,  as those terms are understood  and defined in the  Commission's
     Rule 144, at all times, and (b) file with the Commission in a timely manner
     all reports and other documents  required of the Company under the Exchange
     Act.

     11. Notices. All notices and other communication required or appropriate to
be given  hereunder shall be in writing and shall be delivered by hand or mailed
by certified mail, return


                                      -18-
<PAGE>
<PAGE>



receipt  requested,  or  sent  by  telex  or  facsimile  (in  which  case a
confirming  copy  shall  also be  sent by  certified  mail or  courier),  to the
following respective addresses or to such other addresses as may be specified in
any notice delivered or mailed as above provided:

                  (a)      If to the Purchaser, to:

                           Genentech, Inc.
                           460 Point San Bruno Boulevard
                           South San Francisco, CA 94080
                           Telephone:  (415) 225-1000
                           Facsimile:  (415) 952-9881

                           Attention:  Corporate Secretary

                  (b)      If to the Company to:

                           Xoma Corporation
                           2910 7th Street
                           Berkeley, CA 94080
                           Telephone:  (510) 644-1170
                           Facsimile:  (510) 649-7571

                           Attention:  General Counsel

Any  notice or other  communication  delivered  by hand or mailed  shall be
deemed to have been delivered on the date on which such notice or  communication
is  delivered  by hand,  or in the case of  certified  mail  deposited  with the
appropriate  postal authorities on the date when such notice or communication is
actually received,  and in any other case shall be deemed to have been delivered
on the date on which such notice or communication is actually received.

     12.  Governing  Law.  The parties have agreed that this  Agreement  will be
governed by and construed in accordance with the laws of the State of Delaware.

     13.  Amendments.  No provision of this Agreement may be waived,  changed or
modified, or the discharge thereof acknowledged orally, but only by an agreement
in writing  signed by the party  against  which the  enforcement  of any waiver,
change, modification or discharge is sought.

     14. Assignment.

          (a)  Except as set forth in this  Section  14,  none of the  rights or
     obligations of either party hereto may be assigned or  transferred  without
     the prior  written  consent of the other party  hereto,  provided  that the
     rights of the Purchaser and the obligations of the Company under Section 10
     hereof may be  transferred  to an  Affiliate,  to Roche or to any bona fide
     purchaser for value of at least 500,000 shares of  Registrable  Securities,
     which  transfer  shall  otherwise  be in  compliance  with this  Agreement,
     without the prior written consent of the Company.



                                      -19-
<PAGE>
<PAGE>



          (b) Neither party may assign any of its rights and  obligations  under
     this Agreement in connection with a merger or similar reorganization or the
     sale of all or substantially all of its assets; provided, however, that the
     Purchaser may assign such rights and  obligations  under this  Agreement to
     Roche  (so  long as  Roche  continues  to own at  least a  majority  of the
     outstanding Voting Stock of the Purchaser).

          (c) This  Agreement  shall be binding upon and inure to the benefit of
     the successors and permitted assigns of the parties.  Any assignment not in
     accordance with this Agreement shall be void.

     15.   Counterparts.   This  Agreement  may  be  executed  in  two  or  more
counterparts,  each of  which  will be  deemed  an  original,  but all of  which
together will constitute one and the same instrument.

     16. Entire Agreement.  This Agreement,  the Collaboration Agreement and the
Convertible  Note,  together  with the Exhibits,  Schedules and other  documents
attached  thereto,  constitute  the entire  contract  between the  parties  with
respect to the subject matter hereof and thereof, and no party will be liable or
bound to the other in any manner by any representations, warranties or covenants
except as specifically set forth herein and therein.

     17. Term and Termination.  This Agreement is effective as of the date first
written above and, except as otherwise  expressly provided herein, will continue
in effect  until  the later of the date  neither  the  Purchaser  nor any of its
Affiliates  owns any of the  Securities  and  termination  of the  Collaboration
Agreement, unless earlier terminated by mutual written consent of both parties.

     18.  Titles.  The titles of the Sections of this Agreement are inserted for
reference  only,  and are not to be  considered  as  part of this  Agreement  in
construing this Agreement.

     19.  Disputes.  Any disputes  under this  Agreement will be governed by the
provisions of Article 17 of the Collaboration Agreement.



                                      -20-
<PAGE>
<PAGE>


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


"COMPANY"                              XOMA CORPORATION




                                       By:-----------------------------------
                                           Clarence L. Dellio
                                           Senior Vice President, Operations


"PURCHASER"                            GENENTECH, INC.




                                       By:-----------------------------------
                                          John P. McLaughlin
                                          Executive Vice President






                                      -21-


WHEREVER CONFIDENTIAL  INFORMATION IS
OMITTED HEREIN (SUCH OMISSIONS ARE
DENOTED BY AN ASTERISK), SUCH
CONFIDENTIAL INFORMATION HAS BEEN
SUBMITTED SEPARATELY TO THE SECURITIES
AND EXCHANGE COMMISSION PURSUANT TO
A REQUEST FOR  CONFIDENTIAL TREATMENT




THE SECURITIES  REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933  AND MAY NOT BE  SOLD,  OFFERED  FOR  SALE,  PLEDGED,  HYPOTHECATED,
ASSIGNED OR OTHERWISE  TRANSFERRED  IN THE ABSENCE OF AN EFFECTIVE  REGISTRATION
STATEMENT  UNDER SAID ACT COVERING THE TRANSFER OR AN OPINION OF COUNSEL IN FORM
AND  SUBSTANCE  SATISFACTORY  TO  THE  COMPANY  THAT  SUCH  REGISTRATION  IS NOT
REQUIRED.

THE  SECURITIES   REPRESENTED  HEREBY  ARE  SUBJECT  TO  RESTRICTIONS  ON  SALE,
ASSIGNMENT  OR TRANSFER  PURSUANT TO THAT CERTAIN  COMMON STOCK AND  CONVERTIBLE
NOTE  PURCHASE  AGREEMENT,  DATED AS OF APRIL 22, 1996,  BETWEEN THE COMPANY AND
GENENTECH,  INC., AND MAY NOT (NOR MAY ANY INTEREST THEREIN) BE SOLD,  ASSIGNED,
CONVEYED,  PLEDGED,   HYPOTHECATED  OR  OTHERWISE  DISPOSED  OF  OTHER  THAN  IN
ACCORDANCE WITH THE PROVISIONS THEREOF.

THE SECURITIES  REPRESENTED  HEREBY (AND, IF APPLICABLE,  ANY SECURITIES  ISSUED
UPON CONVERSION  THEREOF) MAY BE SUBJECT TO THE  RESTRICTIONS  SET FORTH IN THAT
CERTAIN COMMON STOCK AND CONVERTIBLE NOTE PURCHASE AGREEMENT,  DATED AS OF APRIL
22, 1996, BETWEEN THE COMPANY AND GENENTECH, INC.

                                                       Berkeley, California
                                                       April 22, 1996

                                XOMA CORPORATION

                     CONVERTIBLE SUBORDINATED NOTE AGREEMENT


     WHEREAS,  XOMA  CORPORATION,  a Delaware  corporation  having its principal
executive office at 2910 7th Street,  Berkeley California 94710 (the "Company"),
and  GENENTECH,  INC., a Delaware  corporation  having its  principal  executive
office at 460 Point San Bruno Boulevard,  South San Francisco,  California 94080
(the "Lender"),  desire to further their corporate collaboration arrangements as
embodied in that certain Common Stock and  Convertible  Note Purchase  Agreement
(the  "Purchase  Agreement")  and  that  certain  Collaboration  Agreement  (the
"Collaboration Agreement"), each dated as of April 22, 1996; and

     WHEREAS,  Lender has agreed  from time to time to make loans to the Company
pursuant to Sections 7.1 and 7.2 of the Collaboration  Agreement,  such loans to
be  evidenced  by  this  Convertible  Subordinated  Note  Agreement  (the  "Note
Agreement" or "Note"); and

<PAGE>
<PAGE>




     WHEREAS,  the Company has agreed to repay any such loans in accordance with
terms of this Note Agreement; and

     WHEREAS,  the parties  contemplate  that,  unless  previously repaid by the
Company,  the aggregate  principal  amount of and accrued interest on such loans
shall be  automatically  converted  upon the  occurrence of certain  events into
Convertible  Preferred Stock,  Series E, of the Company (the "Series E Preferred
Stock"),  having the  preferences  and  rights  (including  conversion  into the
Company's  Common  Stock,  par value  $.0005  per share  (the  "Common  Stock"))
substantially  as set forth in the  Certificate  of  Designation  of Convertible
Preferred  Stock,  Series E, attached hereto as Schedule A (the  "Certificate of
Designation");

     NOW,  THEREFORE,  FOR VALUE  RECEIVED,  the Lender promises to from time to
time make loans to the Company in the amounts  contemplated  by Sections 7.1 and
7.2 of the Collaboration  Agreement and the Company promises to pay to the order
of the Lender the amounts borrowed thereunder, plus accrued interest, all as set
forth below.

     1. Principal.

          (a) General. The amount and date of any borrowing by the Company under
Section  7.1 or 7.2 of the  Collaboration  Agreement  shall be  recorded  by the
Lender and endorsed by the Lender and the Company on Schedule B attached hereto,
which is hereby  made a part of this Note.  Each such loan shall be treated as a
separate loan hereunder,  and, as such,  shall be treated as, and designated,  a
separate "Tranche"  hereunder.  The first loan, being made concurrently with the
execution and delivery of this Note Agreement as contemplated by Section 1(b) is
hereby  designated  "Tranche  A" and  recorded  as such on  Schedule  B attached
hereto.  Each  subsequent  loan made hereunder as  contemplated  by Section 1(c)
shall be similarly  designated with  consecutive  letter  designations,  such as
"Tranche B," "Tranche C," etc., and the applicable designation shall be recorded
by the Lender and  endorsed by the Lender and the Company on Schedule B attached
hereto  at the time any such  loan is made.  The  loans  made  from time to time
hereunder are hereinafter collectively referred to as "Tranches",  and each such
loan is individually referred to as a "Tranche."

          (b) Initial Loan. Under Section 7.1 of the Collaboration Agreement, an
initial loan in an aggregate  principal  amount of  $5,000,000 is required to be
made by the Lender to the Company. Such loan is being made concurrently with the
execution and delivery of this Note Agreement, and, accordingly, is recorded and
endorsed on Schedule B attached hereto and designated as Tranche A thereon.

          (c)  Additional   Loans.   Under  Section  7.2  of  the  Collaboration
Agreement,  the Company also may, at its election,  borrow from the Lender,  and
require  the  Lender to lend to the  Company,  additional  amounts  as set forth
therein  or as  determined  as  provided  therein,  which  amounts  shall  be in
accordance  with the applicable  budgets as  contemplated  by Section 7.2 of the
Collaboration  Agreement. The Lender's obligation to lend any additional amounts
to the Company pursuant to Section 7.2 of the Collaboration Agreement is subject
to the fulfillment on or prior to the date such additional  loans are to be made
of the conditions set forth in paragraphs (i) through (vi) and (viii) of Section
9(a) of the Purchase Agreement (as if such date were the "Closing Date" referred
to therein and it being  understood  that any of the President,  the Senior Vice
President or any Vice President of the Company shall be permitted to execute the
compliance  certificate required by paragraph (iv) thereof),  any one or more of
which may be waived, in whole or part, by the Lender.

                                       -2-
<PAGE>
<PAGE>




          (d) Borrowing and Funding Procedures.  The procedure for borrowing any
such  additional  amounts  shall be as set  forth  in this  Section  1(d).  Upon
approval by the Steering Committee (as such term is defined in the Collaboration
Agreement) of any annual budget (an "Approved Budget") formulated by the Project
Core  Team (as such  term is  defined  in the  Collaboration  Agreement)  all in
accordance  with Article 3 of the  Collaboration  Agreement and  satisfaction or
waiver of the  conditions  referred to in Section 1(c), the Lender shall pay the
dollar  amount  of any  such  Approved  Budget  to  the  Company  at an  account
designated  by the  Company by wire  transfer  of  immediately  available  funds
denominated  in the  currency  of the  United  States  of  America  on the first
business  day  of  the  month  immediately  succeeding  such  approval  and  the
satisfaction or waiver of all such conditions.  Upon receipt thereof, the Lender
shall record such loan as of such date on Schedule B attached hereto as required
by this Section 1 and the Lender and the Company shall endorse such entry.

          (e) Maturity Date. Any unpaid  principal amount of any Tranche owed by
the Company to the Lender as a result of the Company's borrowings under Sections
7.1 and 7.2 of the  Collaboration  Agreement shall be due and payable in full on
April 22, 2005, provided that no unpaid principal amount of any Tranche shall be
due and  payable  sooner  than  the  second  anniversary  from  the  date  funds
represented by such Tranche were advanced to the Company.

          (f) Use of  Proceeds.  The  proceeds of the loans shall be used by the
Company only in connection  with the  development  of the Licensed  Products (as
such  term is  defined  in the  Collaboration  Agreement).  Notwithstanding  the
foregoing, in the event the Collaboration Agreement is terminated, any remaining
proceeds  shall be applied by the  Company to  repayment  of  principal  amounts
outstanding hereunder and accrued interest thereon.

          (g)








                                        *










     2. Interest.


                                       -3-
<PAGE>
<PAGE>



          (a)  Interest on the unpaid  balance of the  principal  amount of each
Tranche  hereunder  and on  any  unpaid  interest  thereon  from  time  to  time
outstanding shall accrue and compound on the last day of each Interest Period at
a rate of interest equal to the LIBOR Rate plus one percent (1%)  (calculated on
the basis of a year of 360 days and actual days  elapsed).  Any unpaid  interest
with respect to any Tranche  shall be due and payable in full on April 22, 2005,
provided that no interest accrued on any Tranche shall be due and payable sooner
than the second  anniversary  from the date funds  represented by the applicable
Tranche were advanced to the Company.

          (b) "LIBOR  Rate"  shall mean,  for each  Interest  Period,  a rate of
interest  equal to the London  Interbank  Offered  Rate (LIBOR) for loans with a
maturity  most closely  approximating  the duration of such  Interest  Period as
published in Bloomberg or The Wall Street Journal on the  applicable  LIBOR Rate
Determination  Date. The Lender shall determine the applicable interest rate for
each Interest  Period on each LIBOR Rate  Determination  Date in accordance with
Section 2(a) and shall notify the Company  promptly  thereafter.  If LIBOR rates
cease to be available as  contemplated  hereby,  the parties agree to discuss in
good faith a comparable interest rate on each Tranche.

          (c)  "Interest  Period"  shall  mean,  with  respect  to a  particular
Tranche,  each six month (or shorter) period beginning on each January 1 or July
1 and ending on June 30 or  December  31 (or  sooner in the event  such  Tranche
matures  prior  to such  date),  respectively,  during  which  such  Tranche  is
outstanding;  provided that, for any Tranche funded on a date other than January
1 or July 1, the first Interest  Period with respect to such Tranche shall begin
on the date of such funding and shall end on the immediately  succeeding June 30
or December 31.

          (d)  "LIBOR  Rate  Determination   Date"  shall  mean  each  date  for
calculating  the LIBOR  Rate for  purposes  of  determining  the  interest  rate
applicable to any Tranche.  The LIBOR Rate Determination Date shall be the first
business day following the first day of the related Interest Period.

     3. Payment.

          (a) Form of Payment.  The principal  amount of and accrued interest on
each Tranche  hereunder  (which shall be reduced by the amount thereof,  if any,
converted  to  Series E  Preferred  Stock  pursuant  to  Section  4) when due or
otherwise paid hereunder shall be payable,  at the option of the Company, by any
of the following means or any combination  thereof:  (i) in cash  denominated in
the currency of the United States of America; or (ii) by set off against amounts
representing profit sharing or royalty payments otherwise payable to the Company
by the Lender  pursuant to Sections 7.3,  7.4, 7.5 or 7.12 of the  Collaboration
Agreement.

          (b) Method;  Application.  Payments of principal and accrued  interest
shall be made at the  address  of the  Lender  set  forth  in the  Collaboration
Agreement,  or at such other place as the Lender shall have notified the Company
in writing at least five  business days before such payment is due. All payments
in respect of any Tranche  under this Note shall be applied first to accrued and
unpaid interest thereon, and thereafter to the unpaid principal amount thereof.

          (c) Recordation.  All payments of interest and principal in respect of
each  Tranche  hereunder  shall be recorded by Lender and endorsed by the Lender
and the  Company on Schedule B attached  hereto,  which is hereby made a part of
this Note. Upon payment in full of all

                                       -4-
<PAGE>
<PAGE>



principal  of and  interest on this Note and each  Tranche  hereunder,
Lender shall return this Note to the Company for cancellation.

          (d)  Prepayments.  (i) This  Note  and any  Tranche  hereunder  may be
prepaid by the Company at any time without penalty,  in whole or in part, by any
of the means described  above.  This Note and any Tranche  hereunder may also be
prepaid by the  Company,  in whole or in part,  through the issuance of Series E
Preferred  Stock at a rate of one  share of  Series E  Preferred  Stock for each
$10,000  aggregate unpaid principal amount and accrued unpaid interest under the
Tranche proposed by the Company to be prepaid.  The Company may not issue Series
E  Preferred  Stock to  prepay  all or a  portion  of this  Note or any  Tranche
hereunder (A) unless at the time of such prepayment a Registration Statement (as
such term is defined in the  Purchase  Agreement)  covering the shares of Common
Stock issuable upon  conversion of the shares of Series E Preferred  Stock to be
issued in connection  with such  prepayment  (such shares of Common  Stock,  the
"Prepayment  Shares")  is  effective  and (B) at any time that the  Company  has
provided  the Lender  with a notice  pursuant  to Section  10(d)(iii)(z)  of the
Purchase Agreement (a "Section 10(d)(iii)(z)  Notice"). In addition, the Company
agrees  that it will not invoke the  provisions  of  Section  10(d)(iii)(z)  and
10(d)(v) of the Purchase  Agreement  during the twenty (20)  business day period
immediately  following  the  issuance of shares of Series E  Preferred  Stock in
connection with any such prepayment  unless either (i) the Company agrees in the
relevant Section  10(d)(iii)(z)  Notice to repurchase the Prepayment  Shares, at
the  option  of the  Purchaser,  for  cash at a price  per  share  equal  to the
aggregate  amount of the Note or Tranche  so prepaid  through  the  issuance  of
Series E Preferred Stock divided by the number of Prepayment  Shares or (ii) the
event or fact the existence or happening of which is referred to in the relevant
Section  10(d)(iii)(z)  Notice is the result of a Force  Majeure.  Force Majeure
means a cause beyond the control of the Company, including,  without limitation,
acts of God, acts, regulations or laws of any government,  war, civil commotion,
damage to facilities or materials by fire,  earthquake or storm, labor disputes,
epidemic and failure of public utilities or common carriers.

          (ii) In the event of any  prepayment  of less than all of the  amounts
outstanding  under this Note,  the Company may designate the Tranche or Tranches
to which such payment shall apply.

     4. Conversion.

          (a) Automatic  Conversion.  The entire unpaid  principal amount of the
Note and each Tranche under this Note and all unpaid  accrued  interest  thereon
shall be  automatically  converted into shares of Series E Preferred  Stock upon
the earliest of (i) the date of receipt of Regulatory  Approval (as such term is
defined in the Collaboration  Agreement) in the United States, (ii) * (iii) with
respect to any Tranche (but only that Tranche),  the date that is ten days after
the date that the  unpaid  principal  of and  unpaid  accrued  interest  on such
Tranche becomes due and payable (such date, the "Conversion  Date").  The number
of shares of Series E  Preferred  Stock into  which this Note or the  applicable
Tranche, as the case may be, shall be converted (the "Conversion  Shares") shall
be determined by dividing the sum of the aggregate  unpaid  principal  amount of
this Note or the applicable  Tranche, as the case may be, and the unpaid accrued
interest  on this  Note or the  applicable  Tranche,  as the case may be, by the
Conversion Price (as defined below) and rounding the result to the nearest whole
integer. The "Conversion Price" shall be equal to $10,000.00.

          (b)  Conversion  Procedure.  If this Note or any Tranche  hereunder is
automatically  converted,  written  notice  shall be delivered by the Company to
Lender at the address

                                       -5-
<PAGE>
<PAGE>



last shown on the records of the Company for Lender or given by Lender
to the Company for the  purpose of notice or, if no such  address  appears or is
given,  at the place  where the  principal  executive  office of the  Company is
located,  notifying Lender of the conversion,  specifying the Conversion  Price,
the  unpaid  principal  amount of and  unpaid  accrued  interest  on the Note or
Tranche  converted,  as the case  may be,  the  date on  which  such  conversion
occurred  and,  if such  conversion  is of the Note in full,  calling  upon such
Lender to surrender to the Company,  in the manner and at the place  designated,
the Note. Upon any such conversion of this Note in full,  Lender shall surrender
this Note, duly endorsed,  at the principal  executive office of the Company. At
its expense,  the Company shall,  as soon as practicable  thereafter,  issue and
deliver to the Lender at such principal office a certificate or certificates for
the number of  Conversion  Shares to which  Lender  shall be entitled  upon such
conversion (bearing such legends as are required by the Purchase Agreement). Any
conversion of this Note or any Tranche hereunder  pursuant to Section 4(a) shall
be deemed to have been made at the close of business,  California  time,  on the
applicable  Conversion  Date, and at and after such time the persons entitled to
receive the Conversion Shares issuable upon such conversion shall be treated for
all purposes as the record holder of such  Conversion  Shares and shall be bound
by the applicable terms of the Purchase Agreement.

          (c) Effect of  Conversion.  Upon  conversion of this Note in full, the
Company shall be forever released from all its obligations and liabilities under
this Note.  Upon any  conversion  of this Note in part,  the  conversion  of the
aggregate  principal amount of the applicable  Tranche and accrued interest with
respect  thereto  shall be recorded by Lender and endorsed by the Lender and the
Company on Schedule B attached hereto, and the Company shall be forever released
from all  obligations  and  liabilities  under  this  Note with  respect  to the
principal amount of such Tranche and accrued interest with respect thereto.

          (d) Reservation of Stock Issuable Upon Conversion.  From and after the
date that the Company files the  Certificate of  Designation in accordance  with
Section 8 of the Purchase Agreement,  the Company shall at all times reserve and
keep  available out of its  authorized  but not  outstanding  shares of Series E
Preferred  Stock,  solely for the purpose of effecting  the  conversion  of this
Note,  such number of its shares of Series E Preferred  Stock (and shares of its
Common Stock issuable upon conversion of such Series E Preferred Stock) as shall
from time to time be  sufficient  to effect the  conversion of the Note (and the
conversion of such shares of Series E Preferred  Stock);  and if at any time the
number of authorized but not outstanding shares of Series E Preferred Stock (and
shares of its Common  Stock  issuable on  conversion  of such Series E Preferred
Stock)  shall  not  be  sufficient  to  effect  the  conversion  of  the  entire
outstanding  principal  amount  of and  accrued  interest  on this Note (and the
conversion  of the  shares  of  Series E  Preferred  Stock  issuable  upon  such
conversion),  without limitation of such other remedies as shall be available to
the Lender,  the Company will use its  commercially  reasonable  efforts to take
such  corporate  action as may,  in the  opinion of  counsel,  be  necessary  to
increase its authorized but not  outstanding  shares of Series E Preferred Stock
(and  shares  of its  Common  Stock  issuable  on  conversion  of such  Series E
Preferred  Stock)  to such  number of  shares  as shall be  sufficient  for such
purposes.

     5.  Subordination.  The  indebtedness  evidenced  by this  Note  is  hereby
expressly  subordinated,  to the extent and in the manner hereinafter set forth,
in  right  of  payment  to the  prior  payment  in full  in  cash of all  Senior
Indebtedness (as defined in Section 5(i) below) of the Company.

          (a)  Insolvency  Proceedings.  If there shall occur any  receivership,
insolvency,  assignment for the benefit of creditors,  bankruptcy  (voluntary or
involuntary), reorganization, or

                                       -6-
<PAGE>
<PAGE>



arrangements with creditors (whether or not pursuant to bankruptcy or other
insolvency  laws), sale of all or substantially all of the assets (other than in
the form of a merger not resulting in insolvency),  dissolution, liquidation, or
any other  marshaling  of the assets and  liabilities  of the  Company,  (i) the
holder(s) of Senior Indebtedness shall be entitled to receive payment in full in
cash of all Senior Indebtedness then outstanding before Lender shall be entitled
to receive any payment or  distribution,  whether in cash,  securities  or other
property,  in respect of the principal of, interest on or other amounts due with
respect  to  this  Note  at the  time  outstanding,  and  (ii)  any  payment  or
distribution,  whether  in  cash,  securities  or  other  property  (other  than
securities  of the Company or any other  corporation  provided  for by a plan of
reorganization or readjustment,  the payment of which is subordinated,  at least
to the  extent  provided  in  this  Section  5,  to the  payment  of all  Senior
Indebtedness  at the time  outstanding  and to any securities  issued in respect
thereof  under any such plan of  reorganization  or  readjustment)  which  would
otherwise  (but for this Section 5) be payable or  deliverable in respect of the
amounts due under this Note shall be paid or delivered directly to the holder(s)
of the Senior Indebtedness (ratably according to the aggregate amounts remaining
unpaid on account of the  Senior  Indebtedness  held by each) or to a trustee or
other representative for holder(s) of Senior Indebtedness.

          (b) Permitted  Payments;  Default on Senior  Indebtedness.  Subject to
Section  5(a),  so long as there shall not have  occurred and be  continuing  an
event of  default  which  has been  declared  in  writing,  or is  automatically
effective in the case of bankruptcy or  insolvency  events,  with respect to any
Senior  Indebtedness  (as such event of  default  is  defined  therein or in the
instrument  under which it is  outstanding),  which event of default permits the
holder or its  representative  to  accelerate  the  maturity  thereof (a "Senior
Default"),  the Company  shall be  permitted  to make,  and Lender to accept and
receive,   payments  of  principal  and  accrued   interest   under  this  Note.
Notwithstanding  anything  to the  contrary  contained  in this  Section  5, the
Company  shall not make and Lender  shall not receive any payment of any kind of
amounts   payable  under  this  Note  after  delivery  by  a  holder  of  Senior
Indebtedness  to the Company and Lender of written  notice that a Senior Default
has occurred;  provided,  however,  that such payments may thereafter be made if
such  holder of Senior  Indebtedness  consents  to such  payments  in writing or
agrees in writing that such Senior Default has been cured or waived.

          (c)  Acceleration;  Enforcement  Rights.  Except for any  acceleration
pursuant to Section 1(g) hereunder,  prior to the payment in full in cash of the
Senior  Indebtedness,  Lender shall have no right to accelerate  the maturity of
the amounts due under this Note or otherwise demand payment thereof, enforce any
claim with  respect to the amounts due under this Note,  institute or attempt to
institute  any  bankruptcy  or  insolvency  proceedings  against  the Company or
otherwise  to take any action  against  the  Company or the  Company's  property
without the prior written consent of each holder of Senior Indebtedness.

          (d) Turnover of Payments.  Except for payments permitted under Section
5(a) or 5(b), should any payment or distribution, whether in cash, securities or
other  property,  be  received  by Lender  upon or with  respect to the  amounts
payable under this Note by any means,  including,  without limitation,  set off,
prior to the payment in full in cash of the Senior  Indebtedness,  Lender  shall
receive and hold the same in trust, as trustee, for the benefit of the holder(s)
of the  Senior  Indebtedness,  and  shall  forthwith  deliver  the  same  to the
holder(s) of the Senior Indebtedness (ratably according to the aggregate amounts
remaining  unpaid on account of the  Senior  Indebtedness  held by each) or to a
trustee  or  other  representative  for  holder(s)  of  Senior  Indebtedness  in
precisely the form received for application to the Senior Indebtedness  (whether
or not it is then due).

                                       -7-
<PAGE>
<PAGE>




          (e) Subrogation.  Subject to the payment in full in cash of all Senior
Indebtedness and the termination of any commitments to lend under the agreements
or instruments governing such Senior Indebtedness, Lender shall be subrogated to
the rights of the  holder(s) of such Senior  Indebtedness  (to the extent of the
payments or  distributions  made to the  holder(s)  of such Senior  Indebtedness
pursuant  to  the  provisions  of  this  Section  5)  to  receive  payments  and
distributions of assets of the Company applicable to the Senior Indebtedness. No
such payments or distributions  applicable to the Senior  Indebtedness shall, as
between  the  Company  and its  creditors,  other than the  holder(s)  of Senior
Indebtedness  and  Lender,  be deemed to be a payment  by the  Company  to or on
account of this Note;  and for  purposes  of such  subrogation,  no  payments or
distributions  to the holder(s) of Senior  Indebtedness to which Lender would be
entitled  except for the  provisions  of this  Section 5 shall,  as between  the
Company and its creditors,  other than the holder(s) of Senior  Indebtedness and
Lender,  be deemed to be a payment by the Company to or on account of the Senior
Indebtedness.

          (f)  Continuing  Subordination.  The  subordination  effected by these
provisions is a continuing  subordination  and may not be modified or terminated
by Lender until payment in full in cash of the Senior Indebtedness.  At any time
and from time to time,  without  consent  of or notice  to  Lender  and  without
impairing or affecting the obligations of Lender hereunder: (i) the time for the
Company's  performance of, or compliance  with any agreement  relating to Senior
Indebtedness may be modified or extended or such performance may be waived; (ii)
a holder of Senior  Indebtedness  may  exercise or refrain from  exercising  any
rights  under any  agreement  relating  to the  Senior  Indebtedness;  (iii) any
agreement  relating  to the  Senior  Indebtedness  may be  revised,  amended  or
otherwise  modified for the purpose of adding or changing any provision  thereof
or  changing  in any  manner  the  rights of the  Company,  any holder of Senior
Indebtedness or any guarantor thereunder; (iv) payment of Senior Indebtedness or
any  portion  thereof  may  be  accelerated  or  extended  or  refunded  or  any
instruments  evidencing  the Senior  Indebtedness  may be renewed in whole or in
part; (v) any person liable in any manner for payment of the Senior Indebtedness
may be  released  by a holder  of Senior  Indebtedness;  (vi) a holder of Senior
Indebtedness may make loans or otherwise extend credit to the Company whether or
not any  default  or  event  of  default  exists  with  respect  to such  Senior
Indebtedness;  and (vii) a holder of Senior Indebtedness may take and/or release
any lien at any time on any  collateral  now or  hereafter  securing  the Senior
Indebtedness and take or fail to take any action to perfect any lien at any time
granted  therefor,  and take or fail to take any action to enforce  such  liens.
Notwithstanding  the  occurrence of any of the  foregoing,  these  subordination
provisions  shall  remain in full  force and effect  with  respect to the Senior
Indebtedness.

          (g) Lender's  Waivers.  Lender hereby expressly waives for the benefit
of the  holder(s)  of  Senior  Indebtedness  (i) all  notices  not  specifically
required  pursuant  to the  terms  of  this  Note  (other  than  notices  of the
incurrence  of  Senior  Indebtedness,  which  shall be  provided  to the  Lender
substantially  concurrently  with the  incurrence of such Senior  Indebtedness);
(ii) any claim which Lender may now or hereafter have against a holder of Senior
Indebtedness  arising  out of any  and all  actions  which a  holder  of  Senior
Indebtedness  in good faith,  takes or omits to take with  respect to the Senior
Indebtedness  (including,  without  limitation,  (A) actions with respect to the
creation,  perfection or continuation of liens in or on any collateral  security
for the Senior  Indebtedness,  (B) actions with respect to the  occurrence of an
event of default under any Senior Indebtedness,  (C) actions with respect to the
foreclosure upon, sale, release, or depreciation of, or failure to realize upon,
any of the collateral  security for the Senior Indebtedness and (D) actions with
respect  to the  collection  of any  claim  for all or any  part  of the  Senior
Indebtedness or the valuation,

                                       -8-
<PAGE>
<PAGE>



use,  protection or release of any collateral  security for the Senior
Indebtedness);  and (iii) any right to require holders of Senior Indebtedness to
exhaust any collateral or marshal any assets.

          (h)  Reliance of  Holder(s)  of Senior  Indebtedness.  Lender,  by its
acceptance  hereof,  shall be deemed to acknowledge and agree that the foregoing
subordination  provisions  are, and are intended to be, an  inducement  to and a
consideration  of each  holder  of  Senior  Indebtedness,  whether  such  Senior
Indebtedness  was  created  or  acquired  before  or after the  creation  of the
indebtedness evidenced by this Note, and each such holder of Senior Indebtedness
shall be deemed conclusively to have relied on such subordination  provisions in
acquiring and holding, or in continuing to hold, such Senior Indebtedness.

          (i) Definition of Senior Indebtedness. For purposes of this Section 5,
"Senior Indebtedness" means the principal of, premium, if any, interest and rent
and royalties  payable on or in connection with, and all fees,  costs,  expenses
and other amounts  accrued or due on or in  connection  with,  Indebtedness  (as
defined  below)  of the  Company,  whether  outstanding  on the date  hereof  or
hereafter created, incurred,  assumed, guaranteed or in effect guaranteed by the
Company  (including  all  deferrals,  renewals,  extensions or refundings of, or
amendments,  modifications or supplements to, the foregoing), unless in the case
of any particular Indebtedness the instrument creating or evidencing the same or
the assumption or guarantee  thereof  expressly  provides that such Indebtedness
shall not be senior in right of payment to the Note or expressly  provides  that
such   Indebtedness   is  "pari  passu"  or  "junior"  to  the  Note.  The  term
"Indebtedness"  means, with respect to any person, and without duplication,  (a)
all indebtedness, obligations and other liabilities (contingent or otherwise) of
such person for borrowed money  (including  obligations in respect of overdrafts
and any  loans or  advances,  whether  or not  evidenced  by  notes  or  similar
instruments)  or evidenced by bonds,  debentures,  notes or similar  instruments
(whether or not the recourse of the lender is to the whole of the assets of such
person  or to only a  portion  thereof)  (other  than  (i) any  account  payable
incurred in the ordinary  course of business in connection with the obtaining of
materials  or  services,  (ii) any loans or  advances  from  unaffiliated  third
parties or  biopharmaceutical  companies in connection  with product or research
and  development  collaborations  or (iii) any personal  loans or advances  from
affiliated third parties who are individuals), (b) all reimbursement obligations
and other  liabilities  (contingent or otherwise) of such person with respect to
letters of credit, bank guaranties or bankers' acceptances,  (c) all obligations
and  liabilities  (contingent  or otherwise) in respect of leases of such person
required,  in conformity with generally accepted  accounting  principles,  to be
accounted  for as  capitalized  lease  obligations  on the balance sheet of such
person and all obligations and other liabilities (contingent or otherwise) under
any lease or related  document  (including a purchase  agreement)  in connection
with the lease of property  which  provides  that such  person is  contractually
obligated to purchase or cause a third party to purchase the leased property and
thereby  guarantee a minimum residual value of the leased property to the lessor
and the  obligations  of the person  under such  lease or  related  document  to
purchase  or to cause a third party to purchase  such leased  property,  (d) all
obligations of such person (contingent or otherwise) with respect to an interest
rate or other swap,  cap or collar  agreement  or other  similar  instrument  or
agreement or foreign currency hedge, exchange, purchase or similar instrument or
agreement,  (e) all  royalty  and  other  payment  obligations  of  such  person
(contingent or otherwise)  under licenses to or other  contractual  arrangements
with biotechnology or pharmaceutical companies not in effect on the date hereof,
(f) all direct or indirect  guaranties  or similar  agreements by such person in
respect of, and  obligations  or  liabilities  (contingent or otherwise) of such
person to purchase or otherwise  acquire or otherwise  assure a creditor against
loss in respect of,  indebtedness,  obligations or liabilities of another person
of the kind described in clauses (a) through (e), (g) any indebtedness or other

                                       -9-
<PAGE>
<PAGE>



obligations  described  in  clauses  (a)  through  (e)  secured by any
mortgage,  pledge, lien or other encumbrance existing on property which is owned
or held by  such  person,  regardless  of  whether  the  indebtedness  or  other
obligation  secured  thereby  shall have been assumed by such person and (h) any
and all  deferrals,  renewals,  extensions  and  refundings  of, or  amendments,
modifications  or supplements to, any  indebtedness,  obligation or liability of
the kind described in any of clauses (a) through (g).

     6. Lost Documents.  Upon receipt by the Company of evidence satisfactory to
it of the loss,  theft,  destruction or mutilation of this Note  Agreement,  and
indemnity   satisfactory  to  the  Company  (in  the  case  of  loss,  theft  or
destruction) or surrender and cancellation of the Note Agreement (in the case of
mutilation),  the  Company  will  make  and  deliver  to the  Lender  a new Note
Agreement of like tenor and unpaid  principal amount and dated as of the date to
which interest has been paid on the unpaid principal balance hereunder.

     7. Notices. All notices and other communications required or appropriate to
be given  hereunder shall be in writing and shall be delivered by hand or mailed
by certified mail, return receipt  requested,  or sent by telex or facsimile (in
which case a confirming  copy shall also be sent by certified  mail or courier),
to the  following  respective  addresses  or to such other  addresses  as may be
specified in any notice delivered or mailed as above provided:

                  (a)    If to the Lender, to:

                         Genentech, Inc.
                         460 Point San Bruno Boulevard
                         South San Francisco, CA  94080
                         Telephone: (415) 225-1000
                         Facsimile: (415) 952-9881

                         Attention:  Corporate Secretary

                  (b)    If to the Company to:

                         Xoma Corporation
                         2910 7th Street
                         Berkeley, CA  94710
                         Telephone: (510) 644-1170
                         Facsimile: (510) 649-7571

                         Attention:  General Counsel

Any  notice of other  communication  delivered  by hand or mailed  shall be
deemed to have been delivered on the date on which such notice or  communication
is  delivered  by hand,  or in the case of  certified  mail  deposited  with the
appropriate  postal authorities on the date when such notice of communication is
actually received,  and in any other case shall be deemed to have been delivered
on the date on which such notice or communication is actually received.

     8. Amendments.  No provision of this Note Agreement may be waived,  changed
or  modified,  or the  discharge  thereof  acknowledged  orally,  but only by an
agreement in writing signed

                                      -10-
<PAGE>
<PAGE>



by  the  party  against  which  the  enforcement  of  any  waiver,  change,
modification or discharge is sought.

     9. Assignment.

          (a)  Except as set  forth in this  Section  9,  none of the  rights or
obligations  of either party hereto may be assigned or  transferred  without the
prior written consent of the other party hereto.

          (b) Neither party may assign any of its rights and  obligations  under
this Note Agreement in connection with a merger or similar reorganization or the
sale of all or  substantially  all of its assets;  provided,  however,  that the
Lender may assign such rights and  obligations  under this Note  Agreement to F.
Hoffmann-LaRoche Ltd or any of its affiliates (the "Roche Affiliates") which are
directly  or  indirectly   controlled  by  it  (collectively,   with  the  Roche
Affiliates,  "Roche") so long as Roche  continues  to own at least a majority of
the voting capital stock  entitled to  participate  generally in the election of
directors of the Lender.

          (c) The Lender may sell,  assign or  transfer  all or a portion of its
interest herein in accordance with, and with the effect provided for in, Section
6(b) of the Purchase Agreement.

          (d) This Note Agreement shall be binding upon and inure to the benefit
of the  successors and permitted  assigns of the parties.  Any assignment not in
accordance with this Note Agreement shall be void.

     10.  Presentment,  Demand,  Etc. Except as otherwise  provided herein,  the
Company hereby waives  presentment  for payment,  demand,  protest and notice of
protest for nonpayment of this Note Agreement,  and consents to any extension or
postponement of the time of payment or any other indulgence.

     11. Governing Law. The parties have agreed that this Note Agreement will be
governed by and construed in accordance with the laws of the State of Delaware.

     12.  Counterparts.  This  Note  Agreement  may be  executed  in two or more
counterparts,  each of  which  will be  deemed  an  original,  but all of  which
together will constitute one and the same instrument.

     13. Titles.  The titles of the Sections of this Note Agreement are inserted
for reference  only, and are not to be considered as part of this Note Agreement
in construing this Note Agreement.

     14.  Disputes.  Any disputes  under this  Agreement will be governed by the
provisions of Article 17 of the Collaboration Agreement.


                                      -11-
<PAGE>
<PAGE>



     IN WITNESS WHEREOF,  this Note Agreement has been executed and delivered on
the date first above written by duly authorized  representatives  of the Company
and the Lender.


                                       XOMA CORPORATION



                                       By:
                                          Clarence L. Dellio
                                          Senior Vice President, Operations


                                       GENENTECH, INC.

                                       By:
                                          John P. McLaughlin
                                          Executive Vice President

                                      -12-
<PAGE>
<PAGE>
<TABLE>
<CAPTION>



                                   SCHEDULE B

                  LOANS AND PAYMENTS OF PRINCIPAL AND INTEREST




Applicable                  Principal Amount    Principal Amount
  Tranche         Date           Borrowed            Repaid           Interest Paid      Amount Converted    Notation By
- - ----------    -----------   -----------------   ----------------    -----------------    ----------------   ------------
<S>            <C>           <C>                <C>                 <C>                  <C>                <C>









</TABLE>
<PAGE>






WHEREVER CONFIDENTIAL INFORMATION IS OMITTED HEREIN (SUCH
OMISSIONS ARE DENOTED BY AN ASTERISK), SUCH CONFIDENTIAL
INFORMATION HAS BEEN SUBMITTED SEPARATELY TO THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL
TREATMENT.

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933 AND MAY NOT BE SOLD, OFFERED
FOR SALE, PLEDGED, HYPOTHECATED, ASSIGNED OR OTHERWISE
TRANSFERRED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION
STATEMENT UNDER SAID ACT COVERING THE TRANSFER OR AN OPINION OF
COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE COMPANY THAT
SUCH REGISTRATION IS NOT REQUIRED.

THE SECURITIES REPRESENTED HEREBY ARE SUBJECT TO RESTRICTIONS
ON SALE, ASSIGNMENT OR TRANSFER PURSUANT TO THAT CERTAIN COMMON
STOCK AND CONVERTIBLE NOTE PURCHASE AGREEMENT, DATED AS OF
APRIL 22, 1996, BETWEEN THE COMPANY AND GENENTECH, INC., AND
MAY NOT (NOR MAY ANY INTEREST THEREIN) BE SOLD, ASSIGNED,
CONVEYED, PLEDGED, HYPOTHECATED OR OTHERWISE DISPOSED OF OTHER
THAN IN ACCORDANCE WITH THE PROVISIONS THEREOF.

THE SECURITIES REPRESENTED HEREBY (AND, IF APPLICABLE, ANY
SECURITIES ISSUED UPON CONVERSION THEREOF) MAY BE SUBJECT TO
THE RESTRICTIONS SET FORTH IN THAT CERTAIN COMMON STOCK AND
CONVERTIBLE NOTE PURCHASE AGREEMENT, DATED AS OF APRIL 22,
1996, BETWEEN THE COMPANY AND GENENTECH, INC.

                                           Berkeley, California
                                                  June 13, 1996


                       XOMA CORPORATION

                           AMENDMENT

                              TO

            CONVERTIBLE SUBORDINATED NOTE AGREEMENT


          WHEREAS, XOMA CORPORATION (the "Company") and
GENENTECH, INC. (the "Lender") are parties to that certain
Convertible Subordinated Note Agreement dated April 22, 1996
(the "Original Note Agreement"); and
<PAGE>
                              -2-



          WHEREAS, the Company and the Lender desire to amend
the Original Note Agreement as set forth herein;

          NOW, THEREFORE, FOR VALUE RECEIVED, the parties agree
to amend the Original Note Agreement as set forth below.

          1.   Definitions.  Capitalized terms used and not
otherwise defined herein shall have the meanings ascribed to
them in the Original Note Agreement.

          2.   When Certain Loans Payable.  The Original Note
Agreement is hereby amended by adding as a new Section 1(h) the
following:

          (h)  When Certain Loans Payable.  *












          3.   Certain Issuances Treated as Prepayments.  The
Original Note Agreement is hereby amended by deleting the
heading of Section 3(d) thereof and substituting therefor the
heading "Prepayments and Certain Issuances Under Section 4(a)"
and by adding as a new third sentence of Section 3(d) thereof
the following:

     As used herein, prepayments through the issuance of
     Series E Preferred Stock shall include any such
     issuance pursuant to clause * of Section 4(a).

          4.   Automatic Conversion.  The Original Note
Agreement is hereby amended by deleting the first sentence of
Section 4(a) thereof in its entirety and substituting therefor
the following:

          The entire unpaid principal amount of the Note and
     each Tranche under this Note and all unpaid accrued
     interest thereon shall be automatically converted into
     shares of Series E Preferred Stock upon the earliest of
<PAGE>
                              -3-



     (i) the date of receipt of Regulatory Approval (as such
     term is defined in the Collaboration Agreement) in the
     United States, (ii) *,

     (iii) with respect to any Tranche (but only that
     Tranche), the date that is ten days after the date that
     the unpaid principal of and unpaid accrued interest on
     such Tranche becomes due and payable, or (iv) *.








          5.   Effect of Amendment.  Except as expressly
amended or modified hereby, the provisions of the Original Note
Agreement shall remain in full force and effect.

          6.   Governing Law.  The parties have agreed that
this amendment will be governed by and construed in accordance
with the laws of the State of Delaware.

          7.   Counterparts.  This amendment may be executed in
two or more counterparts, each of which will be deemed an
original, but all of which together will constitute one and the
same instrument.

          8.   Titles.  The titles of the Sections of this
amendment are inserted for reference only, and are not to be
considered as part of this amendment in construing this
amendment.

          9.   Disputes.  Any disputes under this amendment
will be governed by the provisions of Article 17 of the
Collaboration Agreement.
<PAGE>
                              -4-



          IN WITNESS WHEREOF, this amendment has been executed
and delivered on the date first above written by duly
authorized representatives of the Company and the Lender.

                              XOMA CORPORATION



                              By:-------------------------------
                                 Clarence L. Dellio
                                 Senior Vice President,
                                   Operations


                              GENENTECH, INC.



                              By:-------------------------------
                                 Name:
                                 Title:




                                                   EXHIBIT 23.1



           CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


          As independent public accountants, we hereby consent
to the incorporation by reference in this Registration State-
ment of our report dated February 14, 1996 included in XOMA
Corporation's Form 10-K for the year ended December 31, 1995,
and to all references to our Firm included in this Registration
Statement.


                              ARTHUR ANDERSEN LLP

San Francisco, California
June 28, 1996





































                                                   EXHIBIT 23.2


  [LETTERHEAD OF MARSHALL, O'TOOLE, GERSTEIN, MURRAY & BORUN]



                         June 27, 1996


Board of Directors
XOMA Corporation
2910 Seventh Street
Berkeley, CA 94710

            Re:  Registration Statement on Form S-3

Gentlemen:

          Marshall, O'Toole, Gerstein, Murray & Borun hereby
consents to the disclosure of our relationship as patent coun-
sel to XOMA Corporation (the "Company") in the Company's Regis-
tration Statement on Form S-3 (the "Registration Statement"),
and in particular the references to us under the headings "Risk
Factors - No Assurance of Patent Protection/Avoidance of Patent
Infringement" and "Legal Opinions," and to the filing of this
consent as an exhibit to the Registration Statement.

                              Very truly yours,



                              Marshall, O'Toole, Gerstein,
                                Murray & Borun





















     




© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission