UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                    FORM 8-K




                                 CURRENT REPORT



                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934


       Date of Report (Date of Earliest Event Reported): December 18, 2003


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


                                     BERMUDA
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                 (State or other jurisdiction of incorporation)


              0-14710                                 52-2154066
     (Commission File Number)             (IRS Employer Identification No.)

2910 Seventh Street, Berkeley, California                        94710
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(Address of principal executive offices)                       (Zip code)

Registrant's telephone number, including area code          (510) 204-7200
                                                   -----------------------------


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          (Former name or former address, if changed since last report)







Item 5. Other Events

     As announced on December 18, 2003, Alexion Pharmaceuticals, Inc. and XOMA
Ltd. agreed to collaborate for the development and commercialization of an
antibody to treat chemotherapy-induced thrombocytopenia.

     A copy of the press release is attached hereto as Exhibit 1 and is
incorporated herein by reference.

Item 7. Exhibits

1.      Press Release dated December 18, 2003.








                                    SIGNATURE

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

Dated:  December 18, 2003             XOMA LTD.




                                      By:  /s/  Christopher J. Margolin
                                           ---------------------------------
                                           Christopher J. Margolin
                                           Vice President, General
                                           Counsel and Secretary









                                  EXHIBIT INDEX


Number   Description
------   -----------

1.       Press Release dated December 18, 2003.






                                                                       Exhibit 1

Alexion Pharmaceuticals Investor/Media Contacts:
Stephen P. Squinto, Ph.D.
Executive Vice President and Head of Research
(203) 272-2596

Rhonda Chiger (Investors)
Rx Communications Group
(917) 322-2569

Ernie Knewitz (Media)
Euro RSCG Life NRP
(212) 845-4253

XOMA Investor/Media Contacts:
Laura Zobkiw
Corporate Communications/Investor Relations
(510) 204-7273


               ALEXION PHARMACEUTICALS AND XOMA FORM COLLABORATION
              ****************************************************
       -- Product Development Efforts To Focus On TPO Mimetic Antibody --

CHESHIRE, CT and BERKELEY, CA, December 18, 2003 - Alexion Pharmaceuticals, Inc.
(Nasdaq: ALXN) and XOMA Ltd. (Nasdaq: XOMA) today announced a collaborative
agreement for the development and commercialization of a rationally designed
human c-MPL agonist antibody to treat chemotherapy-induced thrombocytopenia. The
compound was discovered at Alexion Antibody Technologies (AAT), a wholly owned
subsidiary of Alexion, and is in preclinical development. The c-MPL antibody was
designed to mimic the activity of human thrombopoietin (TPO), a naturally
occurring protein responsible for platelet production. Thrombocytopenia is an
abnormal blood condition in which the number of platelets is reduced,
potentially leading to bleeding complications.

"This collaboration combines XOMA's bacterial cell expression technology and its
strong process development and manufacturing capabilities with Alexion's
expertise in antibody engineering, providing the best development means for this
compound," said Stephen P. Squinto, Ph.D., Executive Vice President and Head of
Research. "This also marks a milestone for AAT and demonstrates the progression
of our pipeline; we are pleased to be moving this antibody forward jointly with
XOMA."

"We're enthusiastic about working with Alexion. By collaborating with them, we
gain access to a promising product candidate and Alexion's antibody engineering
and development expertise," John L. Castello, XOMA's Chief Executive Officer,
President and Chairman said. "The c-MPL agonist antibody is particularly well
suited to our process development capabilities, including our bacterial cell
expression system. By combining the strengths of our two companies, we hope to
accelerate getting this product into the clinic and ultimately potential
marketing approval."




Under the terms of the agreement, Alexion and XOMA will jointly develop and
commercialize the c-MPL agonist antibody for chemotherapy-induced
thrombocytopenia. The parties will share development and commercialization
expenses, including preclinical and clinical development, manufacturing and
marketing costs world-wide, as well as revenues, generally on a 70-30 basis,
with Alexion retaining the larger portion. In addition, Alexion will receive
payments tied to initiation of the collaboration and achievement of a regulatory
milestone. XOMA will be entitled to royalty payments and milestones related to
its bacterial expression technology. Specific financial terms were not
disclosed. The collaboration will initially focus on preclinical, process
development and scale-up work, with initial clinical testing anticipated in
2005.

About the TPO Mimetic Antibodies

The rationally designed human c-MPL agonist antibody is part of a new class of
therapeutic antibodies that function as receptor agonists that can stimulate
their cell target, rather than blocking it, and were created using a rational
design and selection process proprietary to AAT. The first rationally designed
human antibody of this new class was designed to accelerate the return of blood
platelet levels to normal following a toxic assault on the bone marrow, which
commonly results in cancer patients undergoing chemotherapy. The TPO agonist
antibody has been designed to bind to and stimulate the c-MPL receptor on the
surface of platelet precursors and then to stimulate platelet-specific
proliferation with a specificity and activity similar to the body's own natural
platelet hormone, thrombopoietin. However, this antibody lacks any protein
sequences related to native thrombopoietin, providing additional therapeutic
benefit by potentially eliminating the harmful immune responses that have been
associated with recombinant thrombopoietin. Alexion recently presented the
status of its rationally designed human c-MPL agonist program at the American
Society of Hematology Meeting held in December 2003 in San Diego. Administration
of the antibody showed an increase in platelets to normal levels in an animal
model following chemotherapy, without production of neutralizing antibodies
against native thrombopoeitin. An abstract of the presentation, made by Dr. Yi
Wang, PhD., Senior Director of Preclinical sciences at Alexion, is available at
the Society's website, www.hematology.org

About Chemotherapy-induced thrombocytopenia

Chemotherapy-induced thrombocytopenia is a disease state where a patient's clot
forming platelets are depleted as a byproduct of treatment with chemotherapeutic
agents. Certain drugs used as chemotherapeutic agents are known to eliminate
cells that are a part of the pathway that leads to formation of platelets.

These cells, known as megakaryocytes, are found in the bone marrow and are the
precursor cells to platelets. Platelets play a critical role in the formation of
blood clots and act by sticking together at the site of a wound to help stop the
blood flow out of the wound. The normal level of platelets usually is in excess
of the level required to support normal clot formation. However, following
chemotherapy, these levels can fall to a level that requires blood transfusions
to protect the patient from excessive bleeding.

About XOMA

XOMA develops and manufactures antibody and other protein-based
biopharmaceuticals for disease targets that include cancer, immunological and
inflammatory disorders, and infectious diseases. XOMA's programs include
collaborations with Genentech, Inc. on the RAPTIVA(TM) antibody for psoriasis
(being marketed), psoriatic arthritis (Phase II) and other indications and with
Millennium Pharmaceuticals, Inc. on a recombinant protein, MLN 2222 for reducing
the incidence of post-operative events in coronary artery bypass graft surgery
patients employing cardiopulmonary bypass (Phase I).


                                      -2-


Bactericidal/permeability-increasing protein (BPI)-derived programs include
NEUPREX(R) in a Phase I/II study to limit complications following pediatric
cardiopulmonary bypass surgery, and XMP.629, a topical formulation of a
BPI-derived compound for acne (Phase I). Other development programs focus on
antibodies and other compounds developed by XOMA for the treatment of cancer and
retinopathies. For more information about XOMA's pipeline and activities, please
visit XOMA's website at http://www.xoma.com/.

About Alexion

Alexion is engaged in the discovery and development of therapeutic products
aimed at treating patients with a wide array of severe disease states, including
cardiovascular and autoimmune disorders, inflammation and cancer. Alexion's two
lead product candidates, pexelizumab and eculizumab, are currently undergoing
evaluation in several clinical development programs. Alexion has completed a
Phase III clinical study with pexelizumab in coronary artery bypass graft
surgery patients undergoing cardiopulmonary bypass, and two large Phase II
studies with pexelizumab in acute myocardial infarction patients. The Phase III
trial and Phase II trials were conducted in collaboration with Procter & Gamble
Pharmaceuticals. In addition, eculizumab is in Phase II clinical trials in
rheumatoid arthritis and membranous nephritis, and has completed pilot programs
for the treatment of paroxysmal nocturnal hemoglobinuria and dermatomyositis.
Alexion is engaged in discovering and developing a pipeline of additional
antibody therapeutics targeting severe unmet medical needs, through its wholly
owned subsidiary, Alexion Antibody Technologies, Inc. This press release and
further information about Alexion Pharmaceuticals, Inc. can be found on the
World Wide Web at: www.alexionpharm.com.


Re: XOMA

Certain statements contained herein related to the development of the c-MPL
antibody and XOMA's collaborative arrangement with Alexion, or that otherwise
relate to future periods, are forward-looking statements within the meaning of
Section 27A of the Securities Act of 1933 and Section 21E of the Securities
Exchange Act of 1934. These statements are based on assumptions that may not
prove accurate. Actual results could differ materially from those anticipated
due to certain risks inherent in the biotechnology industry and for companies
engaged in the development of new products in a regulated market. These and
other risks, including those related to the results of pre-clinical testing, the
timing or results of future clinical trials (including the design and progress
of clinical trials; safety and efficacy of products being tested; action,
inaction or delay by the FDA, European or other regulators or their advisory
bodies; and analysis or interpretation by, or submission to, these entities or
others of scientific data), changes in the status of existing collaborative
relationships, the ability of collaborators and other partners to meet their
obligations, market demand for products, scale-up and marketing capabilities,
competition, XOMA's financing needs and opportunities, share price volatility,
international operations, uncertainties regarding the status of biotechnology
patents, uncertainties as to the cost of protecting intellectual property and
risks associated with XOMA's status as a Bermuda company, are described in more
detail in XOMA's most recent annual report on Form 10-K and in its other SEC
filings.


Re: Alexion

This news release contains forward-looking statements. Such statements are
subject to factors that may cause Alexion's results and plans to differ from
those expected, including the results of pre-clinical or clinical studies
(including termination or delay in clinical programs), the need for additional
research and testing, delays in arranging satisfactory manufacturing capability,
inability to acquire funding on timely and satisfactory terms, de-


                                      -3-


lays in developing or adverse changes in commercial relationships, the
possibility that results of earlier clinical trials are not predictive of safety
and efficacy results in later clinical trials, dependence on Procter & Gamble
Pharmaceuticals for development and commercialization of pexelizumab, the risk
that third parties won't agree to license any necessary intellectual property to
us on reasonable terms, and a variety of other risks set forth from time to time
in Alexion's filings with the Securities and Exchange Commission, including but
not limited to the risks discussed in Alexion's Annual Report on Form 10-K for
the year ended July 31, 2003 and in our other filings with the Securities and
Exchange Commission. In particular, Alexion is not currently able to predict the
determination of the United States Food and Drug Administration (FDA) and other
regulatory agencies regarding the results of the PRIMO-CABG trial. Such
determinations may include, but not be limited to, the view that the results may
be sufficient for filing and approval of a Biologics License Application (BLA),
supportive of the filing and approval of a BLA together with additional studies,
or not supportive of the filing or approval of a BLA. Further, Alexion is not
currently able to predict the reaction of P&GP to the results of the PRIMO-CABG
trial, including how those results may affect P&GP's views of pexelizumab for
CABG or other indications. P&GP retains the development rights and the
termination rights discussed in Alexion's Form 10-K referred to above. Alexion
does not intend to update any of these forward-looking statements to reflect
events or circumstances after the date hereof, except when a duty arises under
law.


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