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CONTACTS FOR CAMBRIDGE NEUROSCIENCE:                          CONTACT FOR BAYER:

Harry W. Wilcox                                               Rob Kloppenburg
President and Chief Executive Officer                         Bayer Corporation
Cambridge NeuroScience, Inc.                                  203-812-6545
(617) 225-0600



Theresa McNeely
Director
Feinstein Kean Partners Inc.
(617) 577-8110


FOR IMMEDIATE RELEASE


       CAMBRIDGE NEUROSCIENCE AND BAYER TO COLLABORATE IN THE DEVELOPMENT
                     OF GGF2 FOR NEURODEGENERATIVE DISEASES


               -- BAYER TO PAY UP TO $26 MILLION PLUS ROYALTIES --


CAMBRIDGE, MASS., DECEMBER 21, 1998 -- Cambridge NeuroScience, Inc. (Nasdaq:
CNSI) and Bayer today announced an agreement worth up to $26 million plus
royalties to develop Cambridge NeuroScience's recombinant Glial Growth Factor 2
(GGF2), for the treatment of neurodegenerative diseases such as Multiple
Sclerosis (MS).

Under terms of the agreement, Bayer will be responsible for all development
costs, including reimbursement of Cambridge NeuroScience's research costs for
GGF2 and will receive exclusive worldwide manufacturing and marketing rights to
the compound. In exchange, Cambridge NeuroScience may receive up to $26 million
in cash and milestone payments, as well as royalties on sales of GGF2 products.

"Cambridge NeuroScience and its academic collaborators have generated impressive
data demonstrating the unique mechanism by which GGF2 stimulates the
remyelination of nerve cells," said David Lowe, Ph.D., head of CNS research at
Bayer. "The companies have worked together in developing a manufacturing process
for the molecule."

"We are pleased to be joining forces with Bayer, whose proven capabilities
should accelerate the development of GGF2," said Harry Wilcox, President and
Chief Executive Officer of Cambridge NeuroScience. "The two teams have worked
together in developing a manufacturing process for the molecule, and in the last
year have begun production of GGF2 in anticipation of initiating clinical
trials. The partnering of GGF2 is in line with our corporate strategy of
focusing our internal efforts on our small molecule and ion-channel blocker
programs."

GGF2, a member of the neuregulin family of growth factors, is known to stimulate
the growth and differentiation of glial cells, the support cells of the nervous
system. These glial cells form the myelin sheath that insulates nerve cells and
is essential for their survival and proper functioning. In demyelinating
diseases such as multiple sclerosis, the myelin sheath is damaged or lost,
leading to the degeneration of the nerve cells. Experiments in animal models
have demonstrated that GGF2 can stimulate the cell growth necessary to protect
and potentially regenerate the damaged myelin sheath.

                                     -more-


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Recent data on GGF2 in multiple sclerosis was published in the August 18, 1998
issue of Proceedings of the National Academy of Sciences. The study, conducted
by CNSI in conjunction with Drs. Cedric Raine and Barbara Cannella at Albert
Einstein College of Medicine in New York, demonstrated that treatment in an
animal model of MS with recombinant human GGF2 leads to delayed onset and
decreased disease severity, as well as a statistically significant reduction in
relapse rate.

Cambridge NeuroScience, Inc. is a neuroscience company engaged in the discovery
and development of proprietary pharmaceuticals focusing on nerve cell survival.
The Company is developing products to treat stroke and chronic neurodegenerative
disorders such as multiple sclerosis, peripheral neuropathies and other
degenerative diseases.

Bayer Corporation is a research-based company with major businesses in
healthcare and life sciences, chemicals and imaging technologies. The company
had 1997 sales of $9 billion and employs 24,000 people. Bayer Corporation is
investing approximately $9 billion in capital expenditures and research and
development in the U.S. operations from 1995 through the year 2000. Bayer
Corporation, with headquarters in Pittsburgh, is a member of the worldwide Bayer
group, a $32.4 billion pharmaceutical and chemical company based in Leverkusen,
Germany.

This press release may contain forward-looking statements based on the current
expectations of management. There are certain important factors that could cause
results to differ from those anticipated by the statements made above,
including, but not limited to, the results of the ongoing pre-clinical studies
of GGF2 and the acceptance by regulatory authorities of the Company's
pre-clinical data as a basis for IND approval.

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