RNS Number:5349P
Antisoma PLC
09 September 2003



              Antisoma Acquires Cytogen's Royalty Rights To R1549


09 September 2003, London, UK and Princeton, New Jersey USA: Antisoma plc (LSE:
ASM; Nasdaq Europe: ASOM), a United Kingdom-based biopharmaceutical company, and
Cytogen Corporation (Nasdaq: CYTO), a United States-based, product-driven,
oncology-focused biopharmaceutical company, today announced that Antisoma has
acquired certain royalty rights to Antisoma's lead product, R1549 (formerly
Pemtumomab), from Cytogen.

In connection with Antisoma's acquisition of such rights, Antisoma made a cash
payment to Cytogen of USD $500,000, and has agreed to make an additional payment
of USD $500,000 upon the first commercial sale, if any, of its R1549 product. In
return, Cytogen relinquished its right to receive royalties equivalent to 1.65%
of net sales revenues, if any, of Antisoma's R1549 product.  Cytogen was
entitled to such royalties pursuant to its grant of a licence to certain
technology, upon which R1549 is based, to Antisoma and Imperial Cancer Research
Technology Limited (now Cancer Research Technology Ltd).

R1549 is being co-developed by Antisoma and Roche.  Roche has worldwide
marketing rights under an agreement between the companies signed in November
2002. R1549 is expected to complete a pivotal phase III study in ovarian cancer
between December 2003 and February 2004, and the major findings of the trial are
expected to be released during the first half of 2004.

Michael D. Becker, President and Chief Executive Officer of Cytogen Corporation,
stated, "We believe that our transfer of royalty rights relating to R1549 to
Antisoma will benefit both Cytogen and Antisoma.  We expect to utilize the
additional working capital to further enhance our focused business plan,
primarily by continuing to develop our sales and marketing efforts for Quadramet
(R), for which we recently reacquired marketing rights in August 2003 from
Berlex Laboratories, Inc."

Commenting on the transaction, Glyn Edwards, CEO of Antisoma, said, "This will
increase our net income from future sales of R1549, and adds to the potential
upside for our shareholders as we await the results from the pivotal study."



Enquiries:

Antisoma plc:
Glyn Edwards, Chief Executive Officer                Tel: +44 20 8799 8200

Financial Dynamics:
Jonathan Birt                                        Tel: +44 207 269 7187

Cytogen Corporation:
Michael D. Becker, Chief Executive Officer           Tel: +1 (609) 750-8289



About Antisoma

Based in London, UK, Antisoma is a biopharmaceutical company that develops novel
products for the treatment of cancer. Antisoma fills its development pipeline by
acquiring promising new product candidates from internationally recognised
academic or cancer research institutions.  Its core activity is the pre-clinical
and clinical development of these drug candidates. Antisoma forms partnerships
with pharmaceutical companies to bring its products to market.  In November
2002, Antisoma signed a ground-breaking collaboration agreement with Roche to
develop and commercialise products from Antisoma's pipeline. For more
information about Antisoma, visit the website at

www.antisoma.com



Antisoma Disclaimer

Except for the historical information presented, certain matters discussed in
this statement are forward looking statements that are subject to a number of
risks and uncertainties that could cause actual results to differ materially
from results, performance or achievements expressed or implied by such
statements. These risks and uncertainties may be associated with product
discovery and development, including statements regarding the company's clinical
development programmes, the expected timing of clinical trials and regulatory
filings. Such statements are based on management's current expectations, but
actual results may differ materially.



About Cytogen

Cytogen Corporation of Princeton, NJ is a product-driven, oncology-focused
biopharmaceutical company. Cytogen markets proprietary and licensed oncology
products through its in-house specialty sales force: Quadramet(R) (a skeletal
targeting therapeutic radiopharmaceutical for the relief of pain due to bone
metastases); ProstaScint(R) (a monoclonal antibody-based imaging agent used to
image the extent and spread of prostate cancer); and NMP22(R) BladderChekTM (a
point-of-care, in vitro diagnostic test for bladder cancer). Cytogen has
exclusive U.S. marketing rights to Combidex(R), an ultrasmall superparamagnetic
iron oxide contrast agent for magnetic resonance imaging of lymph nodes that is
pending clearance by the U.S. Food and Drug Administration. Cytogen's pipeline
comprises product candidates at various stages of clinical development,
including fully human monoclonal antibodies and cancer vaccines based on PSMA
(prostate specific membrane antigen) technology, which was exclusively licensed
from Memorial Sloan-Kettering Cancer Center. Cytogen also conducts research in
cellular signaling through its AxCell Biosciences research division in Newtown,
PA. For more information, please visit the Company's website at www.cytogen.com,
which is not part of this press release.

ProstaScint(R) is a registered United States trademark of Cytogen Corporation.
All other trade names, trademarks or service marks appearing in this press
release are the property of their respective owners, and not the property of
Cytogen or any of our subsidiaries. Quadramet(R) is a trademark of The Dow
Chemical Company used under license by Cytogen.



Cytogen Disclaimer

This press release contains certain "forward-looking" statements within the
meaning of the Private Securities Litigation Reform Act of 1995 and Section 21E
of the Securities Exchange Act of 1934, as amended. All statements, other than
statements of historical facts, included in this press release regarding our
strategy, future operations, financial position, future revenues, projected
costs, prospects, plans and objectives of management are forward-looking
statements. The words "anticipates," "believes," "estimates," "expects," "
intends," "may," "plans," "projects," "will," "would" and similar expressions
are intended to identify forward-looking statements, although not all
forward-looking statements contain these identifying words. Such forward-
looking statements involve a number of risks and uncertainties and investors are
cautioned not to put any undue reliance on any forward-looking statement. There
are a number of important factors that could cause Cytogen's results to differ
materially from those indicated by such forward-looking statements. Such factors
are discussed in Cytogen's Form 10-K for the year ended December 31, 2002, as
amended, and from time-to-time in Cytogen's other filings with the Securities
and Exchange Commission. Any forward-looking statements made by Cytogen do not
reflect the potential impact of any future acquisitions, mergers, dispositions,
joint ventures or investments Cytogen may make. Cytogen does not assume, and
specifically disclaims, any obligation to update any forward-looking statements,
and these statements represent Cytogen's current outlook only as of the date
given.




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