<PAGE>   1

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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-K

         ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
                              EXCHANGE ACT OF 1934

FOR THE FISCAL YEAR ENDED DECEMBER 31, 1999       COMMISSION FILE NUMBER 0-19193
                                                                         -------

                          CAMBRIDGE NEUROSCIENCE, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                   DELAWARE                                     13-3319074
         (STATE OR OTHER JURISDICTION                        (I.R.S. EMPLOYER
       OF INCORPORATION OR ORGANIZATION)                    IDENTIFICATION NO.)

ONE KENDALL SQUARE, BUILDING 700, CAMBRIDGE, MA                    02139
   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                      (ZIP CODE)

       REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (617) 225-0600

           SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:

                                                           Name of each exchange
              Title of each class                           on which registered
              -------------------                          ---------------------
                     None                                           None

           SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:
                     Common Stock, par value $.001 per share
                                (Title of Class)

           Indicate by check mark whether the registrant (1) has filed all
reports required to be filed by Section 13 or 15(d) of the Securities Exchange
Act of 1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes [X] No [ ]

           Indicate by check mark if disclosure of delinquent filers pursuant to
Item 405 of Regulation S-K is not contained herein, and will not be contained,
to the best of registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this Form 10-K or any
amendment to this Form 10-K. [ ]

           The aggregate market value of Common Stock held by non affiliates of
the Registrant as of February 15, 2000, was $20,985,143 based on the last
reported sales price of the Common Stock. As of that date, there were issued and
outstanding 18,135,964 shares of Common Stock, par value $.001 per share.

           Documents incorporated by reference: Specifically identified portions
of the Registrant's Definitive Proxy Statement relating to the 2000 Annual
Meeting of Stockholders into Part III of Form 10-K.


          A list of all Exhibits to this Form 10-K begins on page 36.

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PART I

ITEM 1.     BUSINESS

OVERVIEW

      Cambridge NeuroScience, Inc. (the "Company") is a biopharmaceutical
company engaged in the discovery and development of proprietary pharmaceuticals
to prevent or treat severe disorders of, or injuries to, the nervous system. The
Company has not been profitable since inception and expects to continue to incur
operating losses for at least the next several years. To date, the Company has
funded its operations primarily through proceeds from public and private
offerings of equity securities, from payments received pursuant to
collaborations with pharmaceutical companies and from government grants.
Research and development revenue in 1999 was earned pursuant solely to
collaboration agreements with Allergan, Inc. (Allergan) and Bayer, AG (Bayer),
both of which comprised more than 10% of total revenue. Revenue earned pursuant
to the Allergan agreement totaled 71% of revenue in 1999, 23% in 1998 and 25% in
1997. Revenue earned pursuant to the Bayer agreement totaled 29% of revenue in
1999, 37% in 1998, and 0% in 1997. See "--Strategic Alliances." The Company has
not received any revenue from the sale of products. Research and development
expenses were $4.6 million, $6.0 million and $17.7 million for the years ended
December 31, 1999, 1998 and 1997, respectively. Research and development
expenses represented 80% of total operating expenses in 1999, 80% in 1998
(excluding restructuring costs), and 87% in 1997.

      The Company is concentrating its drug discovery and development efforts in
two main programs: ion-channel blockers to modify nerve cell signaling or to
prevent nerve cell death; and protein growth factors to prevent degeneration of,
or to regenerate, nerve and glial cells. The ion-channel blocker programs are
aimed at preventing or treating neuropathic pain, glaucoma, spinal cord injury,
Parkinson's disease, multiple sclerosis ("MS"), peripheral neuropathies, brain
damage resulting from stroke and other forms of brain ischemia. The growth
factor programs focus on treatments for MS and peripheral neuropathies.

      A summary of the Company's research, development and operating
activities in 1999 is as follows. For further details, see "Product Candidates,"
"Drug Discovery and Development" and "Strategic Alliances."

      Collaboration with Allergan, Inc. for glaucoma and other ophthalmic
disorders: The Company continued performing research, primarily chemistry and in
vitro assay screening, which is being funded by Allergan pursuant to a
collaboration agreement signed in 1996. In 1999, this collaboration was amended
to extend research funding for one year through November 2000.

      Collaboration with Bayer for the development of GGF2:  During 1999, the
Company substantially completed its research performance obligations with
respect to a research protocol covered by its 1998 agreement with Bayer. Such
research was funded by Bayer, and included a series of studies in animals
conducted by third parties under contract to the Company. At the time the
agreement was signed, Bayer and the Company selected MS as the primary
indication for GGF2. Currently, Bayer and the Company are in the process of
evaluating data from recent studies performed by Bayer. Based on results of
these studies, Bayer has indicated it is undertaking a comprehensive review
of all available options for further development of GGF2 before finalizing a
decision. No assurance can be given that there will not be a substantial delay
in the development of GGF2 or that Bayer will continue the development of GGF2.
See "Strategic Alliances" and "Important Factors Regarding Forward Looking
Statements."

      CNS 5161 for the treatment of chronic pain: During 1999, the Company
continued exploring drug formulations suitable for chronic drug administration,
and began advancing the clinical development of CNS 5161 towards Phase II
studies in patients suffering from chronic pain.

      CNS 1102 or aptiganel (formerly known as CERESTAT) for the treatment of
stroke: During 1999, the Company was unsuccessful in its efforts to obtain
public or private funds to continue the development of aptiganel in stroke
patients. The Company does not currently plan to resume clinical trials for
aptiganel without outside funding. CERESTAT is a registered trademark of
Boehringer Ingelheim International GmbH.

      Collaboration with The J. David Gladstone Institutes (Gladstone) for
treatments of Alzheimer's disease: During 1999, the Company completed its
funding obligation under this collaboration, and decided not to exercise a
license for this technology.



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      The Company is focusing its resources on later-stage or funded programs,
and is actively pursuing collaborations for its proprietary programs. The
Company continues to explore opportunities to maximize shareholder value,
including the possible sale or merger of the Company or sale of some or all of
its technology assets.

BACKGROUND

      The central nervous system, composed of the brain and spinal cord,
controls cognitive functions, interprets incoming sensory information and
organizes body movements. The peripheral nervous system, composed of nerve
fibers leading to and from the central nervous system, carries information from
body sensory receptors and commands to muscles and glands. Two main cell types
are found throughout the nervous system: nerve cells, which generate and
transmit electrical signals, and glial cells, which provide nutrition and
support functions to nerve cells.

      Nerve cells and glial cells communicate with one another through a wide
range of electrical and chemical signals to accomplish the normal development
and function of the nervous system. Disorders of the nervous system are
characterized by a change (usually a reduction) in an individual's ability to
perform normal voluntary or involuntary functions. These disorders result from
acute or chronic damage to nerve or glial cells or by abnormalities in the
electrical or chemical communication within and amongst nerve cells or glial
cells.

      Ion channels are membrane-bound proteins that are responsible for
generating nerve cell electrical signals in response to chemical signals
received from other cells or to chemical or electrical changes within a single
cell. Drugs which stimulate, enhance, reduce or suppress the activity of
specific ion channels have potential as treatments for nervous system disorders
because they can eliminate potentially damaging over-stimulation of nerve cells
or correct malfunctions in the processes of generating electrical signals in the
nervous system.

      Chronic degenerative disorders of the nervous system, such as MS and
peripheral neuropathies, also result from the death of nerve or glial cells.
Chronic nerve cell death does not necessarily result from ischemia but can
result from other metabolic causes, including the actions of endogenous and
exogenous toxic substances, some of which can mimic the effects of
over-stimulation of NMDA ion channels ("excitotoxins"). Chronic nerve and glial
cell death can also result from inflammatory processes in the nervous system,
including the autoimmune destruction of oligodendrocytes (a type of glial cell)
that is the hallmark of MS.

      As the nervous system develops, the proliferation, differentiation and
survival of nerve and glial cells are controlled by a variety of protein growth
factors. These growth factors are produced by cells of the nervous system and by
their target cells. Growth factors also play important roles during the normal
regeneration of the nervous system following damage. Animal studies suggest that
one attractive therapeutic approach to replacing damaged nerve and glial cells
is to re-initiate the processes of early development in the nervous system
through the introduction of protein growth factors. Therefore, protein growth
factors offer significant potential as treatments for a variety of neurological
disorders.




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PRODUCT CANDIDATES

      The following table summarizes the partnership status, indications,
development status and commercial rights of each of the Company's ("CNSI")
product candidates. This table is qualified in its entirety by reference to the
more detailed descriptions appearing elsewhere in this document.

<TABLE>
<CAPTION>
     -------------------------------------------------------------------------------------------------------------
                                                                              DEVELOPMENT            COMMERCIAL
          PRODUCT CANDIDATE                    INDICATIONS                     STATUS (1)              RIGHTS
          -----------------                    -----------                    -----------            ----------

     <S>                            <C>                                    <C>                     <C>
     PARTNERED PROGRAMS

     Sodium, NMDA, and combined     Glaucoma and other ophthalmic             Preclinical          Allergan (2)(6)
     ion-channel blockers           disorders

     Glial Growth Factor 2 (GGF2)   Multiple sclerosis and                    Preclinical             Bayer (3)
                                    peripheral neuropathies

     PROPRIETARY PROGRAMS

     CNS 5161 (NMDA ion-channel     Neuropathic pain                            Phase I                CNSI (4)
     blocker)

     CNS 1102 (NMDA ion-channel     Stroke                                  Phase III trials           CNSI (5)
     blocker)                                                              terminated in 1997

     NMDA, sodium, potassium and    Brain and spinal cord injury or             Research               CNSI (6)
     combined ion-channel           ischemia; MS; Pain; Peripheral
     blockers                       neuropathies; Parkinson's disease

     Neuregulin 2                   Neurodegenerative diseases                  Research                  (7)
     -------------------------------------------------------------------------------------------------------------
</TABLE>

(1)   "Research" refers to scientific activities to identify a specific molecule
      or to select a specific clinical indication. "Preclinical" refers to
      safety and efficacy studies conducted in animals. "Phase I" refers to
      smaller-scale trials in human volunteers designed to provide information
      about safety and dosage. "Phase III" refers to large-scale clinical
      trials designed to provide statistically valid proof of efficacy and
      safety in the target population. See "Government Regulation."

(2)   Allergan has the right to develop certain NMDA ion-channel blockers,
      sodium ion-channel blockers and combination ion-channel blockers for the
      treatment of ophthalmic disorders, including glaucoma. See "Strategic
      Alliances."

(3)   Pursuant to the collaboration agreement signed in December 1998, Bayer has
      acquired the worldwide manufacturing and marketing rights for GGF2. See
      "Strategic Alliances."

(4)   The Company has completed two Phase I trials of CNS 5161. The first trial
      was an escalating dose safety study. The second trial involved volunteers
      who were exposed to placebo, morphine and two doses of CNS 5161 in a pain
      model.

(5)   Phase III clinical trials were discontinued in 1997. Upon termination of a
      collaboration agreement with Boehringer Ingelheim International GmbH, in
      November 1998, rights to CNS 1102 were returned to the Company, in
      exchange for a royalty on future sales. See "Drug Discovery and
      Development - CNS 1102."

(6)   Allergan has the right to evaluate a limited number of the Company's
      ion-channel blocker compounds for the treatment of chronic pain. See
      "Strategic Alliances."

(7)   Research is being conducted pursuant to research rights received under an
      option agreement with Harvard University (Harvard), holder of the
      commercial rights. Until such time that the Company and Harvard agree to a
      commercial license, the Company will not have commercial rights.




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<PAGE>   5





DRUG DISCOVERY AND DEVELOPMENT

PARTNERED PROGRAMS

Ion-Channel Blockers for Ophthalmic Disorders: Collaboration with Allergan, Inc.

      Glaucoma is the second leading cause of preventable blindness in the
world, with almost four million patients in the United States alone. The disease
is usually associated with increased pressure within the eye that can damage the
retina and the optic nerve and eventually lead to blindness. In November 1996,
the Company entered into a research and development collaboration with Allergan,
a pharmaceutical company with interests in ophthalmology. The Company and
Allergan believe that it may be possible to treat glaucoma by blocking ion
channels and thereby protecting the retina and the optic nerve from damage. This
collaboration combines the Company's proprietary technology in the area of
ion-channel blockers and Allergan's expertise in the global marketing of
treatments for eye disease. In this collaboration, the Company's molecules that
block sodium ion channels, NMDA ion channels, or both ion channels
simultaneously are being evaluated for their ability to prevent vision loss in
animal models of retinal and optic nerve degeneration. In November 1999, the
collaboration between the two companies was extended for one year and expanded
to include pain management for a limited number of compounds on a non-exclusive
basis. See "Strategic Alliances."

Glial Growth Factor 2: Collaboration with Bayer

GGF2: Multiple Sclerosis

      Multiple sclerosis (MS) is a disease of the central nervous system that is
characterized by chronic inflammation and demyelination at multiple sites in the
brain and spinal cord. Approximately 350,000 people in the United States suffer
from MS. GGF2 is a trophic factor for the glial cells that form and maintain the
myelin sheath insulating nerve axons in the central nervous system. These cells
are primary targets involved early in the pathogenesis of MS. The Company has
developed a manufacturing process for producing GGF2 and has demonstrated its
efficacy in animal models believed to be reflective of MS, including
experimental autoimmune encephalomyelitis ("EAE"). In the acute phase of this
model, GGF2 significantly reduced and delayed the clinical symptoms. In the
chronic, relapsing-remitting phase of EAE, GGF2 significantly reduced the
clinical effects of the disease as well as the number of observed relapses. In
December 1998, the Company entered into a collaborative agreement with Bayer AG
(Bayer) for the development of GGF2 for multiple sclerosis and peripheral
neuropathies. See "Strategic Alliances."

      Currently, Bayer and the Company are in the process of evaluating data
from recent studies performed by Bayer. Based on results of these studies,
Bayer has indicated it is undertaking a comprehensive review of all available
options for further development of GGF2 before finalizing a decision. No
assurance can be given that there will not be a substantial delay in the
development of GGF2 or that Bayer will continue the development of GGF2. See
"Strategic Alliances" and "Important Factors Regarding Forward Looking
Statements."

GGF2: Peripheral Neuropathies

      The Company believes that GGF2 may also be a potential treatment for
peripheral neuropathies as a result of its activity on peripheral glial cells.
Peripheral neuropathies comprise a collection of disorders that are
characterized by the degeneration of sensory and/or motor nerves. This
degeneration may be caused by injury, diabetes, chemotherapy, inherited
disorders and other factors. It was estimated in 1991 that in excess of one
million individuals in the United States suffered from some form of peripheral
neuropathy. The largest segments of this population are those with diabetic
neuropathies and those with chemotherapy-induced neuropathies. There are, at
present, no FDA-approved therapeutic agents for the prevention, reduction or
reversal of the degeneration and atrophy caused by these disorders and injuries.

      The Company has tested GGF2 in animal models of chemotherapy-induced
peripheral neuropathy. In two different experimental paradigms
(cisplatin-induced and vincristine-induced neuropathies), GGF2 administration



                                       5
<PAGE>   6

protected peripheral nerves from the effects of these chemotherapies. The
Company believes that GGF2 may also be a potential treatment of other
degenerative diseases of the peripheral nerves.

PROPRIETARY PROGRAMS

CNS 5161: Neuropathic Pain and Other Neuropathic Disorders

      Despite the availability of a variety of therapeutic approaches to pain
relief, certain disorders are characterized by persistent pathological pain that
is refractory to conventional treatments. Persistent pain associated with
peripheral nerve trauma, neuropathies secondary to diabetes or acquired immune
deficiency syndrome ("AIDS"), amputations and shingles is classified as
neuropathic pain. Drug treatments for neuropathic pain represent a significant
area of unmet medical need and a growing market opportunity. Glutamate
(particularly NMDA) receptors have been implicated in the induction and
maintenance of neuropathic pain in animal models and NMDA antagonists have been
shown to be effective in animal models of persistent pain.

      CNS 5161 is a blocker of the NMDA ion channel that was designed and
synthesized by the Company's chemists. Based on its method of action and its
pharmacokinetic profile in animals, CNS 5161 was advanced toward clinical
evaluation for the treatment of neuropathic pain. Studies have shown that CNS
5161 can prevent the development of a delayed pain response in an animal model,
which is thought to be related to the development of chronic neuropathic pain in
humans.

      The Company has completed two Phase I studies of CNS 5161. Both studies
were conducted in male volunteers. The first demonstrated the safety and
tolerability of selected doses of CNS 5161 given intravenously. Data from the
first study were used to choose potentially effective doses that produced little
in the way of side effects in the volunteers. The second study examined the
reduction in pain experienced after placebo, morphine and two separate doses of
CNS 5161 (0.25mg and 0.5mg), administered on separate occasions to sixteen male
volunteers. CNS 5161 at 0.5mg was found to produce a statistically significant
reduction in perceived pain as compared to either morphine or placebo.

      The Company is currently advancing the clinical development of CNS 5161
towards Phase II studies in patients suffering from chronic pain. The Company's
development plan includes conducting a preliminary Phase II study using an
intravenous formulation of CNS 5161, and to continue exploring drug formulations
suitable for chronic drug administration. Preliminary in vitro studies
undertaken by two leading drug delivery manufacturers have shown that CNS 5161
can be effectively administered through the skin and is suitable for
incorporation into a patch.

CNS 1102 (aptiganel): Background and Clinical Trial Status

      The Company believes that aptiganel has the potential to improve outcome
for stroke victims by preventing glutamate-induced nerve cell death through the
blockade of the NMDA ion channel. Aptiganel has been the subject of Phase III
clinical trials for stroke and traumatic brain injury (TBI). The Company and a
former collaborator, Boehringer Ingelheim International GmbH, initiated Phase
III trials in both of these indications in 1996. Enrollment of patients in both
studies was stopped in 1997, prior to completion, based on the results of
scheduled interim analyses of the data in each trial. In TBI, the interim
analysis of the data showed insufficient evidence of positive clinical impact.
In stroke, the data raised concerns over the benefit-to-risk ratio of drug
treatment. In March 1998, the Company reported that further analysis of the
Phase III data indicated that aptiganel had: (i) an attractive safety profile at
relatively high doses in the TBI patient population, and (ii) a potential
therapeutic benefit in a subset of the stroke patient population.

      Based on input from an independent panel of stroke experts, which convened
in October 1998, and the Company's review and analysis of the trial data, the
Company has been pursuing options for funding further development of aptiganel
in a subset of the stroke population. However, the Company has not been
successful in obtaining either private or public funds for this purpose, and
does not currently plan to resume the study of aptiganel without outside
funding.



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<PAGE>   7

Other Ion-Channel Blockers for Nervous System Disorders

      The Company has applied its expertise in discovering and developing NMDA
ion-channel blockers to the synthesis and testing of compounds that block other
ion channels, such as sodium and potassium ion channels, which can contribute to
nerve cell death or abnormal nerve cell electrical activity. The Company
believes that such molecules may have therapeutic utility in a number of acute
and chronic neurological disorders, including glaucoma, stroke, brain and spinal
cord injury, Parkinson's disease, MS and peripheral neuropathies.

      To discover new treatments for preventing disorders of the central nervous
system which arise from brain or spinal cord ischemia and trauma, the Company
has synthesized ion-channel blockers with enhanced potency in the environment of
ischemic tissues relative to their potency in the environment of normal tissues.
The Company believes that such targeted ion-channel blockers could achieve
efficacy with fewer unwanted side effects.

      In addition to molecules which block NMDA ion channels, the Company has
created a library of small organic molecules which block the sodium ion channels
of nerve cells. In vitro and in vivo studies have demonstrated that sodium
ion-channel blockers can protect nerve cells from ischemic and traumatic damage
and can exert other beneficial effects, such as reducing responses to painful
stimuli and limiting the consequences of damage to nerve fiber bundles. The
Company believes that molecules which block neuronal sodium ion channels have
potential as treatments for various forms of acute and chronic disorders of the
nervous system, including stroke, brain and spinal cord injury and pain.

      As an extension of its work in NMDA and sodium ion-channel blockers, the
Company has synthesized molecules which have the capacity to block both NMDA ion
channels and sodium ion channels. The Company is currently conducting in vitro
and in vivo studies to test the hypothesis that such combination compounds have
enhanced efficacy in treating neurological disorders when compared to the
efficacy of compounds which block only one of these classes of ion channels. In
addition, the Company is conducting studies with potassium channel blockers in
the area of peripheral neuropathies.

      OTHER PROTEIN GROWTH FACTORS

      The Company has conducted research on novel protein growth factors other
than GGF2. Growth/Differentiation Factor-1 ("GDF-1") is a
nervous-system-specific member of the Transforming Growth Factor-(beta)
("TGF-(beta)") protein family. The Company believes that GDF-1 is likely to play
a role in responses to injury, ischemia and demyelination. The Company has shown
that GDF-1 enhances the neurite outgrowth activity of another known growth
factor and also proliferated cerebellar granule cells. Several members of the
TGF-(beta) gene family have biological activities that potentially can be
employed for therapeutic effects in the nervous system, including: the promotion
of dopaminergic neuron survival, which may be applicable as a treatment for
Parkinson's disease; the promotion of motor neuron survival, which may be
applicable as a treatment for amyotrophic lateral sclerosis; and
immunosuppression, which may be applicable as a treatment for MS. In 1998, the
Company entered into a technology licensing agreement with Creative
Biomolecules, Inc., ("CBMI") whereby the Company outlicensed its rights in GDF-1
to CBMI in exchange for an upfront licensing fee and future royalties on sales.

      The Company has an option to license technology related to Cerebellum
Derived Growth Factor (Neuregulin-2) from Harvard University. The Company has
applied for a National Institutes of Health research grant. If the grant is
awarded, the Company will pursue research with the proceeds of such grant and a
minimal amount of the Company's financial resources. There can be no assurance
that the Company will be able to obtain a research grant or license this
technology.

STRATEGIC ALLIANCES

      The Company has formed collaborations with pharmaceutical companies to
support the development of its product candidates, provide capital for such
development, and share development risk. The Company is actively pursuing
discussions with additional companies regarding collaborations, mergers,
acquisitions or product-licensing arrangements. No assurance can be given,
however, that any collaborations, mergers, acquisitions or licensing
arrangements will be completed in the foreseeable future or on terms that would
be favorable to the Company.



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<PAGE>   8

Allergan

      In November 1996, the Company entered into a collaboration with Vision
Pharmaceuticals L.P., d/b/a Allergan Inc. ("Allergan") to jointly develop NMDA
ion-channel blockers, sodium ion-channel blockers and combination ion-channel
blockers, initially for the treatment of ophthalmic disorders, including
glaucoma. Upon signing the agreement, Allergan purchased 175,103 shares of
Common Stock from the Company for $3.0 million, and provided an additional $3.0
million in research funding over a three-year period through November 1999. In
December 1999, the Company and Allergan amended the collaboration agreement to
add an additional year of research funding for the period November 1999 to
November 2000. This fourth year of funding is in the amount of $1.25 million.
Additionally, the amendment expanded the treatment field to include pain
management for a limited number of compounds on a non-exclusive basis.

      Pursuant to this collaboration, Allergan will be responsible for
development, manufacturing and marketing and will bear all costs associated
therewith. The Company may receive up to an additional $18.5 million upon the
achievement of certain milestones as well as royalties on any product sales.
There can be no assurance, however, as to when or if these milestones will be
met. Allergan has certain termination rights under the terms of the agreement,
and either party may, in its sole discretion, terminate the agreement upon 90
days prior written notice of a material breach by the other party.

Bayer AG

      In December 1998, the Company entered into a collaborative agreement with
Bayer for the development of GGF2 for the treatment of neurodegenerative
diseases such as MS. In exchange for the exclusive worldwide manufacturing and
marketing rights to the compound, the Company received an up front licensing fee
of $1.0 million and received reimbursement for $1.0 million of the Company's
research costs for GGF2 pursuant to a protocol covered by the agreement. The
Company may receive up to $24.0 million in milestone payments, as well as
royalties on sales of GGF2 products. There can be no assurance, however, as to
when or if these milestones will be met. Bayer will provide all material needed
in the conduct of the research and development activities and shall be
responsible for all associated costs.

      Currently, Bayer and the Company are in the process of evaluating data
from recent studies performed by Bayer. Based on results of these studies,
Bayer has indicated it is undertaking a comprehensive review of all available
options for further development of GGF2 before finalizing a decision. No
assurance can be given that there will not be a substantial delay in the
development of GGF2 or that Bayer will continue the development of GGF2. In the
event Bayer elects to terminate the collaboration, it is doubtful the Company
could obtain sufficient financial and technical resources to continue GGF2
development. Either party may terminate this agreement at any time for cause.
Bayer may terminate this agreement at any time, upon 120 days written notice.
See "Important Factors Regarding Forward Looking Statements."

Algos

      In December 1999, the Company and Algos Pharmaceuticals Corporation
(Algos) entered into a license agreement whereby the Company was granted a
non-exclusive sub-license to certain Algos patent rights in the field of pain
management. In exchange, Algos received the non-exclusive right to negotiate
commercial licenses with respect to certain of the Company's research and
development compounds. There was no cash or equity consideration associated with
this transaction.

The J. David Gladstone Institutes

      In December 1996, the Company, The J. David Gladstone Institutes
("Gladstone") and The Regents of the University of California (the "University")
entered into a three year collaboration for the development of treatments for
Alzheimer's disease and certain other neurological diseases, disorders or
injuries. The collaboration focused on novel pharmaceuticals that inhibit the
activity of a form of apolipoprotein E ("apoE"), a molecule that has been widely
linked to Alzheimer's disease. In conjunction with this agreement, in 1996 the
Company formed a subsidiary, Cambridge NeuroScience Partners, Inc. ("CNPI"), of
which the Company owned 80% of the outstanding common stock and Gladstone and
the University owned 15% and 5%, respectively.



                                       8
<PAGE>   9

      Pursuant to the collaboration agreement: Gladstone conducted research over
a three-year period through December 1999, for which CNPI provided funding of
$1.25 million per year; the Company provided CNPI, interest-free, all amounts
necessary to enable CNPI to make such payments; and the University granted CNPI
an exclusive three-year option to negotiate an exclusive worldwide,
royalty-bearing license for patentable rights in intellectual property covered
by or arising from the research program within the field, subject to certain
terms and conditions set forth in the option agreement.

      In December 1999, the Company and CNPI completed their funding obligations
under this collaboration, and the Company decided not to exercise a license for
this technology. As a result, the Company expects to dissolve CNPI during 2000.

Creative Biomolecules, Inc.

      In December 1998, the Company entered into a technology licensing
agreement with CBMI whereby CBMI acquired the exclusive rights to GDF-1 in
exchange for a cash payment and future royalties on product sales. Either party
may terminate this agreement upon a material breach which is not cured within 60
days of written notice of such breach.

Boehringer Ingelheim International GmbH

      In March 1995, Cambridge NeuroScience and BI entered into agreements to
collaborate on the worldwide development and commercialization of aptiganel.
Under terms of the agreements, BI was obligated to fund 75% of the development
costs for aptiganel in the United States and Europe and all of the development
costs in Japan. The Company received $15.0 million on signing these agreements,
consisting of $5.0 million for expense reimbursement and $10.0 million for
1,250,000 shares of Common Stock. In September 1996, and in connection with the
commencement of a Phase III stroke trial by BI, the Company received a
milestone payment of $10.0 million for 1,237,624 shares of Common Stock. The
Company and BI conducted two Phase III trials of aptiganel. In the second half
of 1997, the companies announced the discontinuation of patient enrollment into
both trials after interim analyses indicated that continuation of the trials was
not justified. In November 1998, the Company and BI terminated the collaboration
and license rights were returned to the Company, subject to a royalty of 3% of
direct sales or 10% to 20% of royalties on sales by third parties. See "Drug
Discovery and Development - CNS 1102 (aptiganel): Background and Clinical Trial
Status."

MARKETING AND SALES

      The Company does not currently sell any products nor does it plan to in
the foreseeable future, and therefore has no marketing, sales, or distribution
organization. The Company's strategy is to rely on its collaborative partners
for marketing, sales and distribution.

MANUFACTURING

      The Company has no manufacturing facilities and plans to rely upon outside
manufacturers to produce any near- or intermediate-term products. To date, the
Company has contracted with chemical synthesis companies to produce kilogram
quantities of several of its product candidates. The Company intends to
establish and maintain its own quality-control program for each line of
products. Such program will include a set of standard operating procedures
designed not only to assure that the Company's products are manufactured in
accordance with Good Manufacturing Practices ("GMP") guidelines and other
applicable regulations, but also to maintain consistent product quality.
However, no specific arrangements have been made, and there can be no assurance
that the Company will be able to establish such capabilities. Pursuant to the
research collaboration and licensing agreement for the development of GGF2,
Bayer is responsible for the manufacture of all material needed in the
conduct of the development activities and for all associated costs. Pursuant to
the termination of the collaboration with BI, the Company has the right to
purchase 56kg of aptiganel from BI within two years from the date of termination
of the agreement.



                                       9
<PAGE>   10

COMPETITION

      The fields in which the Company is involved are characterized by rapid
technological progress. New developments are expected to continue at a rapid
pace in both industry and academia. There are many companies, both public and
private, including large pharmaceutical companies, chemical companies and
specialized genetic engineering companies, engaged in developing products
competitive with products under development by the Company. Many of these
companies have greater capital, human resources, research, development,
manufacturing, and marketing experience than the Company. Such companies may
succeed in developing products that are more effective or less costly than any
that may be developed by the Company and may also prove to be more successful
than the Company in production and marketing. Competition may increase further
as a result of potential advances in the commercial applicability of
biotechnology and greater availability of capital for investment in these
fields. In addition, academic, government and industry-based research is
intense, resulting in considerable competition in obtaining qualified research
personnel, submitting patent filings for protection of intellectual property
rights and establishing corporate strategic alliances. There can be no assurance
that research, discoveries and commercial developments by others will not render
any of the Company's programs or potential products noncompetitive.

      The Company will, for the foreseeable future, rely on strategic partners
for certain preclinical evaluation and clinical development of its product
candidates and manufacturing and marketing of any products. In addition, the
Company relies on its strategic partners, in part, for support in its drug
discovery operations. The pharmaceutical companies with which the Company has
collaborations are in some cases attempting to develop other products to treat
diseases within the fields of the collaborations with the Company. Generally,
the Company's agreements with its strategic partners do not prohibit the
strategic partners from engaging in competitive activities with the Company.

      Biotechnology and related pharmaceutical technology have undergone rapid
and significant change. The Company expects the technology associated with the
Company's research and development will continue to develop rapidly, and the
Company's future success will depend in large part on its ability to maintain a
competitive position with respect to this technology. Rapid technological
development by the Company or others may result in compounds, products or
processes becoming obsolete before the Company recovers any expenses it incurs
in connection with developing such products.

PATENTS AND PROPRIETARY TECHNOLOGY

      Proprietary protection for the Company's products, technology and
processes is essential to its business. The Company's policy is to protect its
technology by, among other things, filing or causing to be filed patent
applications for technology that it considers important to the development of
its business. As of December 31, 1999, Cambridge NeuroScience had licensed or
owned rights in 54 issued U.S. patents. Research and development efforts by the
Company and its collaborators led to the issuance of four U.S. patents and the
allowance of five others in 1999. In addition, eight U.S. patent applications
were filed in 1999 on behalf of the Company and its collaborators, bringing the
total number of pending U.S. applications to 34. These U.S. filings have
corresponding patent filings in other countries as well. The Company is awaiting
action on various patent applications that have either been filed by it or by
academic institutions with which it collaborates.

      The Company intends to file, or cause to be filed, additional patent
applications, where appropriate, relating to new product discoveries or
improvements. The use of patents to protect proprietary positions for synthetic
chemicals is well established within the pharmaceutical industry. While the
precedents for gaining patent protection for biologically derived or produced
products through recombinant DNA technology are not as well developed, many
patents have been issued for products of this technology. There can be no
assurance, however, that patents will provide meaningful proprietary protection
to the Company, given the uncertain and complex legal and factual questions
relating to their breadth and enforceability.



                                       10
<PAGE>   11

      There are patents held by third parties that relate to the manufacture,
development and use of the Company's product candidates for which the Company
has licenses. There can be no assurance that the Company will not in the future
require licenses to additional patents or that such licenses will be available
on commercially reasonable terms, if at all. In addition, there can be no
assurance that existing or future licenses will not be terminated or that any
such termination or failure to obtain a license will not have a material adverse
effect on the Company's business, financial condition or results of operations.

      The Company has licensed rights to inventions relating to GGF2, which are
covered by nine issued U.S. patents, several allowed U.S. patent applications
and other pending patent applications in the United States and foreign
countries. The Company believes that its employees and those of its licensor are
the original inventors and that the Company and its licensor are entitled to
patent protection in the United States. However, the Company is aware of a
third-party patent and pending patent applications in the United States and
corresponding patent applications pending in some foreign countries that, if
issued and valid, may be construed to cover aspects of the Company's GGF2
product candidates. There can be no assurance that the Company will not infringe
any such issued U.S. third-party patents, and that the claims of future patents
issuing from the third-party patent applications, if any, will not be infringed
by the Company's proposed manufacture, use or sale of products based on the GGF2
technology. There can be no assurance that the Company would prevail in any
legal action seeking damages or injunctive relief for infringement of the
existing third-party patent or any patent that might issue from such third-party
applications or that any license required under such patent would be available
or, if available, would be available on commercially reasonable terms. Failure
to obtain a required license or to successfully establish non-infringement of,
or the invalidity or unenforceability of, such third-party patents could
preclude the manufacture, sale and use of the Company's products based on such
GGF2 technology.

      Patents granted to the Company in any areas of the Company's technology
may be subject to interference proceedings in the United States or opposition
proceedings in foreign countries brought by third parties. There can be no
assurance that the Company would prevail in any such proceedings or that such
proceedings would not result in a material adverse effect on the Company's
business, financial condition or results of operations. An unfavorable decision
in an interference or opposition proceeding may have a material adverse effect
on the business, financial condition and results of operations of the Company.

      The Company also relies upon trade secrets, know-how and continuing
technological advances to develop and maintain its competitive position. To
maintain the confidentiality of trade secrets and proprietary information, the
Company maintains a policy of requiring employees, Science Advisory Board
members, consultants and collaborators to execute confidentiality and invention
assignment agreements upon commencement of a relationship with the Company.
These agreements are designed both to enable the Company to protect its
proprietary information by controlling the disclosure and use of technology to
which it has rights and to provide for ownership by the Company of proprietary
technology developed at the Company. There can be no assurance, however, that
these agreements will provide meaningful protection for the Company's trade
secrets in the event of unauthorized use or disclosure of such information. In
addition, whenever the U.S. government funds research programs, it may obtain
nonexclusive rights to patented subject matter otherwise subject to exclusive
rights.

      In December 1999, the Company and Algos Pharmaceuticals Corporation
(Algos) entered into a license agreement whereby the Company was granted a
non-exclusive sub-license to certain Algos patent rights in the field of pain
management. In exchange, Algos received non-exclusive rights to negotiate
commercial licenses with respect to certain of the Company's research and
development compounds.


                                       11
<PAGE>   12
GOVERNMENT REGULATION

      The clinical development, manufacture and marketing of pharmaceutical
products in the United States require the approval of the FDA under the
Federal Food, Drug and Cosmetic Act. Similar approvals by comparable
agencies are required in most foreign countries. The FDA has established
substantial requirements on the testing, manufacture, quality control,
safety, effectiveness, labeling, storage, record keeping, approval
advertising, and promotion of pharmaceutical products. Pharmaceutical
manufacturing facilities are also subject to the regulations of state, local
and other authorities.

      As an initial step in the FDA regulatory approval process, preclinical
studies are typically conducted in animal models to assess a drug's efficacy
and to identify potential safety problems. The results of these studies
must be submitted to the FDA as part of an Investigational New Drug
application ("IND"). The IND automatically becomes effective 30 days after
receipt by the FDA, unless the FDA, within the 30-day time period, raises
concerns or questions about the conduct of the planned trials. In that
case, the IND sponsor and the FDA must resolve any outstanding concerns or
questions before a trial can begin. Typically, clinical trials are
conducted in three-sequential phases that may overlap. Phase I clinical
trials are conducted with a small number of healthy human subjects and are
designed to provide information about safety, dosage tolerance, metabolism,
and distribution of the drug. Phase II clinical trials are designed to
provide efficacy of the product for a specific targeted disease, as well as
additional information on dosing and safety in a limited patient population.
Phase III clinical trials are large-scale studies designed to provide
additional information about dosage, clinical efficacy and to further test
for safety in an expanded patient population. The results of the
preclinical testing and clinical trials of a pharmaceutical product are then
submitted to the FDA in the form of a New Drug Application ("NDA"), or for a
biological product in the form of a Biologics License Application ("BLA"),
for approval to commence commercial sales. Preparing such applications
involves considerable data collection, verification, analysis, and expense.
In responding to an NDA or a BLA, the FDA may grant marketing approval,
request additional information, or deny the application if it determines
that the application does not satisfy its regulatory criteria.

      Once issued, the FDA may withdraw product approval if compliance with
regulatory standards is not maintained or if problems occur after the
product is on the market. In addition, the FDA may require testing and
surveillance programs to monitor the effects of approved products which have
been commercialized, and the FDA has the right to prevent or limit further
marketing based on the results of these post marketing programs. The
regulatory process can require many years and the expenditure of substantial
resources. Data obtained from preclinical testing and clinical trials are
subject to varying interpretations, which can delay, limit, or prevent FDA
approval. In addition, changes in FDA approval policies or requirements may
occur or new regulations may be promulgated that may result in delay or
failure to receive FDA approval. Similar delays or failures may be
encountered in foreign countries. Delays and costs in obtaining regulatory
approvals would have a material adverse effect on the Company's business,
financial condition and results of operations.

      Among the conditions for NDA or BLA approval is the requirement that the
prospective manufacturer's quality-control and manufacturing procedures
conform on an ongoing basis with GMP. In complying with GMP, manufacturers
must continue to expend time, money, and effort in the area of production
and quality control to ensure full technical compliance. After NDA or BLA
approval, the manufacturing facility is subject to periodic inspections by
the FDA.

      The requirements which the Company must satisfy to obtain regulatory
approval by governmental agencies in other countries prior to
commercialization of its products in such countries can be as rigorous and
costly as those described above.

<PAGE>   13
      The Company is also subject to various laws and regulations relating to
safe working conditions, laboratory and manufacturing practices, the
experimental use of animals, and the use and disposal of hazardous or
potentially hazardous substances, including radioactive compounds and infectious
disease agents used in connection with the Company's research. Compliance with
laws and regulations relating to the protection of the environment has not had a
material effect on capital expenditures or the competitive position of the
Company. However, the extent of government regulation, which might result from
any legislative or administrative action, cannot be accurately predicted.

REIMBURSEMENT

      The Company's ability to commercialize pharmaceutical products may depend
in part on the extent to which reimbursement for the costs of such products and
related treatments will be available from governmental, private health insurers,
managed care organizations and other third-party payors. Significant uncertainty
exists as to the reimbursement status of newly approved health care products,
and third-party payors are increasingly challenging the prices charged for
medical products and services. There can be no assurance that coverage by
third-party payors for any products developed by the Company will be available
to patients. Government and other third-party payors are increasingly
attempting to contain health care costs by limiting both coverage and the level
of reimbursement for new therapeutic products. In some cases, such payors are
refusing to provide coverage for uses of approved products for disease
indications for which the FDA has not granted marketing approval.



                                       12
<PAGE>   14


      The Company's business may be materially adversely affected by the
continuing efforts of governmental and third-party payors to contain or reduce
the costs of health care through various means. For example, in certain foreign
markets, pricing or profitability of prescription pharmaceuticals is subject to
government control. In the United States, there have been, and the Company
expects that there will continue to be, a number of federal and state proposals
to implement similar government control. In addition, an increasing emphasis on
managed care in the United States has and will continue to put pressure on
pharmaceutical pricing. Such initiatives and proposals, if adopted, could
decrease the price that the Company receives for any products it may develop and
sell in the future and thereby have a material adverse effect on the Company's
business, financial condition and results of operations. Further, to the extent
that such proposals or initiatives have a material adverse effect on other
pharmaceutical companies that are collaborators or prospective collaborators for
certain of the Company's potential products, the Company's ability to
commercialize its potential products may be adversely affected.

EMPLOYEES

As of December 31, 1999 the Company had 17 full-time employees, of whom 13 were
engaged in research and development and 4 in administration and finance.
Doctorates or other advanced degrees are held by 10 of the Company's employees.
All of the Company's employees have signed confidentiality agreements, and none
of the employees are covered by collective bargaining agreements. The Company
considers its employee relations to be good.

ITEM 1 (a).       EXECUTIVE OFFICERS OF THE COMPANY

      The executive officers of the Company are as follows:

      Name                    Age   Position
      ----                    ---   --------

      Harry W. Wilcox, III    45    President; Chief Executive Officer; Director

      Robert N. McBurney      52    Senior Vice President, Research; Chief
                                    Scientific Officer

      David I. Gwynne         48    Vice President, Biotechnology and Business
                                    Development

      Laima I. Mathews        52    Vice President, Drug Development

      Glenn A. Shane          37    Controller; Treasurer; Chief Accounting
                                    Officer

      HARRY W. WILCOX, III joined the Company as Senior Vice President, Finance
and Business Development and Chief Financial Officer in December 1995 and was
named President and Chief Executive Officer and Director of the Company in May
1998. Prior to joining the Company, Mr. Wilcox served as Vice President, Finance
and Chief Financial Officer of Cellcor, Inc., a biotechnology company, since
1990. While at Cellcor, Mr. Wilcox was also named Treasurer and Senior Vice
President of Business Development. From 1988 to 1990, he was a founder and
general partner and Chief Financial Officer of Highland Capital Partners, L.P.,
a venture capital firm. From 1983 to 1987, Mr. Wilcox was Controller, Vice
President of Finance and Chief Financial Officer at Charles River Ventures, Inc.
a venture capital firm. Mr. Wilcox earned an M.B.A. degree from Boston
University and a B.A. degree in Finance from the University of Arizona. Mr.
Wilcox is a Certified Public Accountant.

      ROBERT N. MCBURNEY, PH.D. joined the Company as Director of
Electrophysiology and Cell Biophysics in December 1987, and served as Vice
President, Research from June 1990 through December 1993, at which time he
became Senior Vice President, Research and Chief Scientific Officer. Prior to
joining Cambridge NeuroScience, Dr. McBurney served from 1984 to 1987 as the
Assistant Director of the Medical Research Council Neuroendocrinology Unit in
Newcastle upon Tyne, England. Dr. McBurney earned B.Sc. and Ph.D. degrees in
Physiology from the University of New South Wales, and conducted postdoctoral
studies in Neurophysiology at



                                       13
<PAGE>   15

Cambridge University and the National Institutes of Health. Dr. McBurney has had
numerous articles published on neurophysiology in various scientific journals.

      DAVID I. GWYNNE, PH.D. joined the Company in 1991 as Director,
Biotechnology and became Senior Director of Biotechnology in 1996. In May 1998
he was named Vice President of Biotechnology and Business Development. Dr.
Gwynne leads the Company in the development of growth factors for the treatment
of neurological disorders. Prior to joining the Company, Dr. Gwynne served as
Director of Scientific Affairs at Allelix Biopharmaceuticals, Inc. where he led
the development effort for growth factors in the treatment of inflammatory
disorders and tissue repair. Dr. Gwynne earned a B.Sc. and an M.Sc. in biology
from the University of Toronto. He completed a Ph.D. in molecular biology at
McGill University and conducted post-doctoral studies at the University of
California, Davis in the area of regulation of gene expression.

      LAIMA I. MATHEWS joined the Company in September 1992 as Director of
Regulatory Affairs and served in that capacity until March 1997, when she was
appointed Vice President of Drug Development. Prior to joining the Company, Mrs.
Mathews held various positions at G.D. Searle/The NutraSweet Company (Monsanto
Companies) from 1972 through 1992. Her experience includes all aspects of
international development and registration for ethical and consumer
pharmaceutical products, medical devices and food additives. She earned a B.A.
from Loyola University of Chicago.

      GLENN A. SHANE joined the Company as Accounting Manager in April 1992 and
served in that capacity until May 1998, at which time he was appointed
Controller and Treasurer of the Company. Prior to joining the Company, Mr. Shane
was Accounting Manager at Boston Business Group from 1989 to 1991. From 1985 to
1989, Mr. Shane was employed in the audit department of Deloitte & Touche LLP,
an international accounting firm. Mr. Shane earned a Bachelors of Business
Administration from the University of Massachusetts, Amherst and is a Certified
Public Accountant.

ITEM 2. PROPERTIES

      The Company's sole facility is located in Cambridge, Massachusetts, where
it leases approximately 41,000 square feet of space. In June 1998, the Company
sub-leased to a third party approximately half of its facility. The Company
currently occupies approximately 20,000 square feet of space, including
approximately 13,000 square feet of laboratory space. The description of the
lease terms is incorporated by reference from Note I to the Consolidated
Financial Statements. The current lease expires in July 2000. The Company is
currently evaluating its leasing options.

ITEM 3. LEGAL PROCEEDINGS

      Neither the Company nor its subsidiary is a party to any legal proceeding.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

      No matters were submitted to a vote of security holders during the fourth
quarter of the year ended December 31, 1999.



                                       14
<PAGE>   16

PART II

ITEM 5. MARKET FOR REGISTRANT'S COMMON EQUITY AND RELATED STOCKHOLDER MATTERS

      Since January 1999, the Company's Common Stock, $.001 par value ("Common
Stock"), trades on the OTC Bulletin Board ("OTC") under the symbol "CNSI". From
June 1991 until January 1999, the Common Stock was listed on the Nasdaq National
Market under the symbol "CNSI". The following table sets forth the high and low
sales prices for the Company's Common Stock for the periods indicated:

                                                       High          Low
                                                      ------        -----

            January 1  -  March 31, 1998               2-5/8        1-5/8
              April 1  -  June 30, 1998                2-1/2        19/32
               July 1  -  September 30, 1998          1-3/16        13/32
            October 1  -  December 31, 1998                2          3/8

            January 1  -  March 31, 1999               29/32        21/32
              April 1  -  June 30, 1999                1-1/8        43/64
               July 1  -  September 30, 1999          1-1/32        27/32
            October 1  -  December 31, 1999           1-1/64        57/64

      There were approximately 165 holders of record of Common Stock and
approximately 3,000 beneficial owners as of February 15, 2000. Prior to March 9,
1998, the Company had never declared nor paid any cash dividends on its capital
stock. On March 9, 1998 the Company's Board of Directors declared an
extraordinary dividend on its capital stock of $1.00 per share of outstanding
Common Stock, which was paid on April 14, 1998. Future cash dividends, if any,
will be paid at the discretion of the Company's Board of Directors and will
depend, among other things, upon the Company's future operations, capital
requirements, general financial condition and such other factors as the Board of
Directors may deem relevant.




                                       15

<PAGE>   17

ITEM 6.  SELECTED FINANCIAL DATA

The selected financial data set forth below should be read in conjunction with
the consolidated financial statements of the Company and related notes thereto
and "Management's Discussion and Analysis of Financial Condition and Results of
Operations" included elsewhere in this document.

                            SELECTED FINANCIAL DATA

<TABLE>
<CAPTION>
                                                                  YEAR ENDED DECEMBER 31,
                                           ---------------------------------------------------------------------
                                             1999           1998           1997            1996            1995
                                           -------        -------        --------        --------        -------
<S>                                        <C>            <C>            <C>             <C>             <C>
STATEMENT OF OPERATIONS DATA:                             (in thousands, except per-share amounts)

Revenues                                   $ 1,443        $ 4,303        $  4,035        $  2,396        $ 8,218
Operating expenses:
    Research and development                 4,616          5,984          17,650          13,978         13,850
    General and administrative               1,159          1,472           2,616           2,585          2,158
    Restructuring costs                         --            921              --              --             --
                                           -------        -------        --------        --------        -------
Total operating expenses                     5,775          8,377          20,266          16,563         16,008
                                           -------        -------        --------        --------        -------
Loss from operations                        (4,332)        (4,074)        (16,231)        (14,167)        (7,790)
Interest income                                588          1,180           2,393           1,178            736
                                           -------        -------        --------        --------        -------
Net loss                                   $(3,744)       $(2,894)       $(13,838)       $(12,989)       $(7,054)
                                           =======        =======        ========        ========        =======
Net loss per common share                  $ (0.21)       $ (0.16)       $  (0.79)       $  (0.93)       $ (0.59)

Cash dividends declared per
  common share                                  --        $  1.00              --              --             --

Weighted average common shares
  outstanding                               18,118         17,976          17,518          13,980         11,927
</TABLE>

<TABLE>
<CAPTION>
                                                                      DECEMBER 31,
                                          ----------------------------------------------------------------------
                                             1999           1998           1997            1996            1995
                                          ---------      ---------      ---------        --------        -------
<S>                                       <C>            <C>            <C>              <C>             <C>
BALANCE SHEET DATA:                                                    (in thousands)

Cash and cash equivalents                 $   3,333      $   4,863      $  12,020        $ 26,664        $ 21,937
Marketable Securities                         6,489          7,037         26,561              --              --
Working capital                               9,731         13,353         33,588          18,362          17,651
Total assets                                 10,769         15,617         40,891          29,220          24,321
Total liabilities                               753          1,887          6,568           9,573           4,793
Accumulated deficit                        (110,120)      (106,376)      (103,482)        (89,644)        (76,655)
Stockholders' equity                         10,016         13,730         34,323          19,647          19,528
</TABLE>


                                       16
<PAGE>   18




ITEM 7. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

OVERVIEW

      Since inception, the Company has been primarily engaged in research and
development. The Company has not received any revenue from the sale of products.
The Company has not been profitable since inception and expects to incur
substantial operating losses for at least the next several years.

      The Company has financed its operations through private placements of
preferred equity securities, an initial public offering in 1991, follow-on
public offerings in 1991 and 1997, a private placement of common stock to
institutional investors in 1994 and two directed public offerings in 1995. The
Company has also received funding pursuant to its research and development
collaborations, research grants and from investment income earned on its cash
and short-term investments.

      In November 1996, the Company entered into a collaboration with Allergan
for the development of NMDA ion-channel blockers, sodium ion-channel blockers
and combination ion-channel blockers for the treatment of ophthalmic disorders,
including glaucoma. Under the agreement, Allergan purchased 175,103 shares of
the Company's Common Stock for $3.0 million, and provided $1.0 million per year
in research funding through November 1999. In December 1999, the collaboration
was amended to extend the research funding for an additional year in the amount
of $1.25 million for the period November 1999 through November 2000. Allergan
will bear all of the development costs for potential products arising from the
collaboration, and the Company will be entitled to royalties on any product
sales.

      In December 1998, the Company entered into a collaborative agreement with
Bayer AG ("Bayer") for the development of recombinant human Glial Growth Factor
2 ("GGF2") for the treatment of neurodegenerative diseases such as multiple
sclerosis ("MS"). In exchange for the exclusive worldwide manufacturing and
marketing rights to the compound, the Company received a $1.0 million up front
licensing fee and $1.0 million for research costs incurred pursuant to a
research protocol covered by the agreement.

      In December 1996, the Company entered into a collaboration with the J.
David Gladstone Institutes ("Gladstone") and the Regents of the University of
California, for the development of treatments for Alzheimer's disease and other
neurological disorders. In connection with this collaboration, the Company
formed a subsidiary, Cambridge NeuroScience Partners, Inc. ("CNPI"). Pursuant to
the terms of the collaboration, Gladstone conducted a research program over a
three-year period, through 1999, for which CNPI provided funding of $1.25
million per year. As of December 31, 1999, CNPI and the Company have completed
their funding obligations associated with this collaboration, and do not
anticipate incurring additional research costs associated therewith.

      In November 1998, the Company and Boehringer Ingelheim International GmbH
("BI") terminated their collaboration for the development of aptiganel, which
commenced in 1995, and commercial rights to aptiganel were returned to the
Company, subject to a royalty on future sales. After November 1998, this
collaboration will result in no further revenue.

      RESULTS OF OPERATIONS

YEARS ENDED DECEMBER 31, 1999 AND 1998

Revenues

      Research and development revenue decreased by $2.9 million for the year
ended December 31, 1999, compared to 1998. Revenue in 1999 consisted of $1.0
million and $420,000 in research funding from Allergan and Bayer, respectively.
In the prior year, revenue consisted of $1.0 million and $580,000 in research
funding from Allergan and Bayer, respectively; $1.5 million in upfront licensing
fees, primarily from Bayer, and $1.2 million associated with the termination in
1998 of a collaboration agreement with BI. In addition, in 1998 the Company
earned $50,000 from a government grant.




                                       17
<PAGE>   19



Operating Expenses

      Operating expenses in 1999 decreased by $2.6 million compared to 1998.
This decrease represents decreases of $1.4 million in research and development
expenses and $313,000 in general and administrative expenses, and was primarily
the result of lower wage and facility costs due to a restructuring plan
implemented in 1998. Operating expenses in 1998 also included a restructuring
charge of $921,000, consisting of salaries and benefits relating to the
restructuring in 1998.

Interest Income

      Interest income decreased in 1999 by $592,000. This was due primarily to
lower cash, cash equivalents and marketable securities as a result of the
payment in April 1998 of a dividend totaling $17.9 million and due to cash used
for operating purposes.

Net Loss per Share

      For the year ended December 31, 1999 the Company had a net loss of $3.7
million, or ($0.21) per share, compared to a net loss of $2.9 million or ($0.16)
per share for the year ended December 31, 1998. This increase in net loss and
net loss per share reflects lower research and development revenue and interest
income in 1999, partly offset by lower operating expenses, all as described
above.

YEARS ENDED DECEMBER 31, 1998 AND 1997

Revenues

      Revenue increased by $268,000 for the year ended December 31, 1998,
compared to the same period in 1997. This increase was due to the recognition of
revenue in 1998 relating to the agreements signed in December 1998 with Bayer
and Creative Biomolecules. Offsetting in part the revenue recognized in 1998
under these two new agreements, revenue earned pursuant to the BI agreement
decreased to $1.2 million, compared to $2.9 million in 1997.

      In 1998, the Company earned $50,000 from a government grant which expired
in the first quarter of 1998. In 1997, the Company had $150,000 of revenue from
two government grants, which expired in 1997 and the first quarter of 1998.

Operating Expenses

      Operating expenses decreased by $11.9 million to $8.4 million in 1998.
This decrease reflects the discontinuation of the clinical trials of aptiganel
in the second half of 1997 and the impact of the restructuring plan that was
implemented in March 1998. Research and development expenses decreased by $11.7
million to $6.0 million in 1998, compared to $17.7 million in 1997. General and
administrative expenses decreased by $1.1 million, to $1.5 million in 1998,
compared to $2.6 million in 1997. These decreases reflect a $7.7 million
reduction in costs associated with the discontinuation of the clinical trials of
aptiganel and a decrease of $5.1 million in other operating costs as a result of
the workforce reduction and other cost containment measures implemented in March
1998 as part of the restructuring plan. Operating expenses in 1998 also included
a one-time restructuring cost of $921,000, consisting of salaries and benefits
relating to the reduction in workforce in March 1998, which were paid in full in
1998.

Interest Income

      The Company had interest income in 1998 of $1.2 million, compared to $2.4
million in 1997. Interest income decreased in 1998 due to a decrease in the
funds available for investment during the year, primarily as a result of the
payment of the dividend totaling $17.9 million in April 1998, as well as the use
of funds for operating purposes during the year, including the repayment to BI
of excess advances received of $1.5 million.



                                       18
<PAGE>   20

Net Loss per Share

      For the year ended December 31, 1998, the Company had a net loss of $2.9
million, or ($0.16) per share, compared to $13.8 million or ($0.79) per share
for the year ended December 31, 1997. This decrease in net loss and net loss per
share reflects the decrease in total operating expenses in 1998, as a result of
the discontinuation of the clinical trials of aptiganel in the second half of
1997 and the restructuring plan implemented in March 1998.

LIQUIDITY AND CAPITAL RESOURCES

      At December 31, 1999, the Company had cash, cash equivalents and
investments in marketable securities of $9.8 million, compared to $11.9 million
at December 31, 1998 and $38.6 million at December 31, 1997. The decrease of
$2.1 million in 1999 was due primarily to the use of cash for operating purposes
of $2.0 million and the purchase of equipment furniture and fixtures totaling
$105,000. At January 31, 2000, the Company had cash, cash equivalents and
investments in marketable securities of $9.7 million.

      In 1999, pursuant to the collaboration agreement with Bayer, the Company
received $1.0 million in upfront license fees and $1.0 million in reimbursements
for research costs incurred in 1998 and 1999 under a research protocol covered
by the agreement. Of the total $2.0 million received, $420,000 was recognized as
revenue in 1999, representing research reimbursements, and approximately $1.6
million was recognized in 1998, representing the $1.0 million upfront fee and
$580,000 in reimbursements of research costs. This $1.6 million of revenue in
1998 was included in receivables from collaboration agreements as of December
31, 1998. The $1.0 million upfront license fee represented a one time payment
for certain existing patents. The $1.0 million in reimbursement of research
expenses represented reimbursements for specific research tasks. The Company has
substantially completed its obligations with respect to this revenue, and has no
material performance or financial obligations with respect to either the upfront
fee or the research reimbursements. Bayer is responsible for all manufacturing
and development activities and associated costs. The Company may receive up to
$24.0 million in milestone payments as well as royalties on sales of GGF2
products. There can be no assurance, however, as to when or if these milestones
will be achieved.

      Pursuant to a collaboration agreement with Allergan signed in 1996 and
amended in 1999, the Company received $1.0 million per year in research funding
through 1999, and will receive $1.25 million for research funding for the twelve
month period ending November 2000. Under the agreement, Allergan is responsible
for the development of potential products and will bear all associated costs.
The collaboration also provides that the Company may receive up to an additional
$18.5 million upon the achievement of certain milestones. However, there can be
no assurance as to when or if these milestones will be achieved.

      Pursuant to a 1996 collaboration agreement between the Company's
subsidiary, CNPI, and Gladstone, CNPI provided Gladstone $1.25 million per year
in research funding over three years. As of December 31, 1999, CNPI and the
Company had completed their funding obligations under this agreement, and do not
anticipate incurring additional research costs related therewith. The Company
owns 80% of CNPI. The minority shareholders have not made equity investments in
the subsidiary, as such, the entire net loss from CNPI has been attributed to
the Company.

      In December 1998, the Company entered into a technology licensing
agreement with CBMI whereby CBMI acquired the exclusive rights to GDF-1 in
exchange for an up front cash payment and future royalties on product sales. The
Company has no further performance or financial obligations with respect to this
agreement.

      The Company believes that its cash, cash equivalents and investments
totaling $9.7 million at January 31, 2000 will be sufficient to maintain
operations through 2001. The Company anticipates that thereafter it will require
substantial additional funds from collaborative partners, public offerings or
private offerings to further its research and development programs and for other
operating activities. The Company's primary expenditures are expected to be in
the areas of research and development and general and administrative expenses.
At January 31, 2000, the Company did not have any material commitments for
capital expenditures.

      Despite potential future milestones under collaborative agreements,
adequate funds for these purposes may not be available when needed on terms
acceptable to the Company. Insufficient funds may require the Company to delay,
scale back or eliminate certain of its research and product development programs
or to license to third parties the rights to commercialize products or
technologies that the Company might otherwise undertake itself. The



                                       19
<PAGE>   21

Company is continuing to evaluate alternatives for maximizing shareholder value
including the sale or merger of the Company.

      In January 1999, the Company's common stock was delisted from the Nasdaq
National Market System due to a failure to maintain a minimum price per share of
$1.00. Immediately following the delisting, the Company began trading on the
Over the Counter Bulletin Board ("OTCBB"). The delisting of the Company's stock
could have an adverse effect on the liquidity of the common stock held by
investors and on the Company's ability to raise equity.

      At December 31, 1998, the Company had cash, cash equivalents and
investments in marketable securities of $11.9 million. The decrease of $26.7
million from December 31, 1997 was due primarily to the payment in April 1998 of
a dividend of $1.00 per share, totaling $17.9 million. In addition, the Company
used $8.9 million for operating purposes, including a repayment of $1.5 million
of excess advances received under a collaboration with BI.

      The Company does not believe that inflation has had a material impact on
its results of operations.

YEAR 2000 READINESS

      In prior years, the Company discussed the nature and progress of its plans
to become Year 2000 ready. In late 1999, the Company completed its remediation
and testing of systems. As a result of those planning and implementation
efforts, the Company experienced no significant disruptions in mission critical
information technology and non-information technology systems and believes those
systems successfully responded to the Year 2000 date change. The Company
expensed approximately $25,000 during 1999 in connection with remediating its
systems. The Company is not aware of any material problems resulting from Year
2000 issues, either with its internal systems or the products and
services of third parties. The Company will continue to monitor its mission
critical computer applications and those of its suppliers and vendors throughout
the year 2000 to ensure that any latent Year 2000 matters that may arise are
addressed promptly.

ITEM 7A.    QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

      The information required by Item 7A is not provided as the disclosure
requirements are not applicable to the Company pursuant to Item 305(e) of
Regulation S-K.





                                       20
<PAGE>   22
ITEM 8.     FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA


                          CAMBRIDGE NEUROSCIENCE, INC.
                   INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

                                                                         PAGE
                                                                         ----

Report of Independent Auditors                                            22

Consolidated Balance Sheets                                               23

Consolidated Statements of Operations                                     24

Consolidated Statements of Changes in Stockholders' Equity                25

Consolidated Statements of Cash Flows                                     26

Notes to Consolidated Financial Statements                                27





                                       21
<PAGE>   23



                         REPORT OF INDEPENDENT AUDITORS



Board of Directors and Stockholders
Cambridge NeuroScience, Inc.

We have audited the accompanying consolidated balance sheets of Cambridge
NeuroScience, Inc. as of December 31, 1999 and 1998, and the related
consolidated statements of operations, stockholders' equity, and cash flows for
each of the three years in the period ended December 31, 1999. These financial
statements are the responsibility of the Company's management. Our
responsibility is to express an opinion on these financial statements based on
our audits.

We conducted our audits in accordance with auditing standards generally accepted
in the United States. Those standards require that we plan and perform the audit
to obtain reasonable assurance about whether the financial statements are free
of material misstatement. An audit includes examining, on a test basis, evidence
supporting the amounts and disclosures in the financial statements. An audit
also includes assessing the accounting principles used and significant estimates
made by management, as well as evaluating the overall financial statement
presentation. We believe that our audits provide a reasonable basis for our
opinion.

In our opinion, the financial statements referred to above present fairly, in
all material respects, the consolidated financial position of Cambridge
NeuroScience, Inc. at December 31, 1999 and 1998, and the consolidated results
of its operations and its cash flows for each of the three years in the period
ended December 31, 1999, in conformity with accounting principles generally
accepted in the United States.





                                          /s/ ERNST & YOUNG LLP


Boston, Massachusetts
February 2, 2000




                                       22


<PAGE>   24
                          CAMBRIDGE NEUROSCIENCE, INC.
                           CONSOLIDATED BALANCE SHEETS
                      (in thousands, except per share data)

<TABLE>
<CAPTION>

                                                                  DECEMBER 31,
                                                           --------------------------
                                                              1999             1998
                                                           ---------        ---------
<S>                                                        <C>              <C>

ASSETS

Current Assets
    Cash and cash equivalents                              $   3,333        $   4,863
    Marketable securities                                      6,489            7,037
    Receivables from collaboration agreements                    171            2,080
    Prepaid expenses and other current assets                    491            1,260
                                                           ---------        ---------
Total Current Assets                                          10,484           15,240

Equipment, furniture and fixtures, net                           285              377
                                                           ---------        ---------
Total Assets                                               $  10,769        $  15,617
                                                           =========        =========


LIABILITIES AND STOCKHOLDERS' EQUITY

Current Liabilities
    Accounts payable and accrued expenses                  $     753        $   1,637
    Research and development advances                             --              250
                                                           ---------        ---------
Total Current Liabilities                                        753            1,887

Stockholders' Equity
    Preferred stock, par value $.01, 10,000
      shares authorized; none issued                              --               --
    Common stock, par value $.001, 30,000
      shares authorized; 18,136 shares issued
      and outstanding at December 31, 1999;
      18,085 at December 31, 1998                                 18               18
    Additional paid-in capital                               120,118          120,088
    Accumulated deficit                                     (110,120)        (106,376)
                                                           ---------        ---------
Total Stockholders' Equity                                    10,016           13,730
                                                           ---------        ---------
Total Liabilities and Stockholders' Equity                 $  10,769        $  15,617
                                                           =========        =========
</TABLE>

                             See accompanying notes.

                                       23

<PAGE>   25

                          CAMBRIDGE NEUROSCIENCE, INC.
                      CONSOLIDATED STATEMENTS OF OPERATIONS
                      (in thousands, except per share data)

<TABLE>
<CAPTION>
                                                                YEAR ENDED DECEMBER 31,
                                                         --------------------------------------
                                                           1999           1998           1997
                                                         -------        -------        --------
<S>                                                      <C>            <C>            <C>
Revenues
     Research and development                            $ 1,443        $ 4,253        $  3,885
     Government grants                                        --             50             150
                                                         -------        -------        --------
                                                           1,443          4,303           4,035

Operating expenses
     Research and development                              4,616          5,984          17,650
     General and administrative                            1,159          1,472           2,616
     Restructuring cost                                       --            921              --
                                                         -------        -------        --------
                                                           5,775          8,377          20,266
                                                         -------        -------        --------
Loss from operations                                      (4,332)        (4,074)        (16,231)

Interest income                                              588          1,180           2,393
                                                         -------        -------        --------
Net loss                                                 $(3,744)       $(2,894)       $(13,838)
                                                         =======        =======        ========

Basic and diluted net loss per common share              $ (0.21)       $ (0.16)       $  (0.79)
                                                         =======        =======        ========

Shares used in computing basic and diluted net
 loss per common share                                    18,118         17,976          17,518
                                                         =======        =======        ========
</TABLE>




                             See accompanying notes.

                                       24


<PAGE>   26

                          CAMBRIDGE NEUROSCIENCE, INC.
           CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY
                                 (in thousands)

<TABLE>
<CAPTION>
                                                COMMON STOCK               ADDITIONAL                           TOTAL
                                          -----------------------           PAID-IN         ACCUMULATED      STOCKHOLDERS'
                                           SHARES          AMOUNT           CAPITAL           DEFICIT           EQUITY
                                          -------          ------          ----------       -----------      -------------

<S>                                       <C>             <C>              <C>               <C>               <C>
Balance at December 31, 1996               15,010            $15           $ 109,276         $ (89,644)        $ 19,647

  Sale of common stock, net of
   offering costs of $2,221                 2,760              3              28,136                --           28,139
  Common stock issued pursuant to                                                                                    --
   employee benefit plans                      77             --                 321                --              321
  Exercise of stock options                    11             --                  54                --               54
  Net loss                                     --             --                  --           (13,838)         (13,838)
                                           ------            ---           ---------         ---------         --------
Balance at December 31, 1997               17,858             18             137,787          (103,482)          34,323

  Common stock issued pursuant to
   employee benefit plans                     227             --                 208                --              208
  Cash dividend ($1.00 per share)              --             --             (17,907)               --          (17,907)
  Net loss                                     --             --                  --            (2,894)          (2,894)
                                           ------            ---           ---------         ---------         --------
Balance at December 31, 1998               18,085             18             120,088          (106,376)          13,730

  Common stock issued pursuant to
   employee stock purchase plan                51             --                  30                --               30
  Net loss                                     --             --                  --            (3,744)          (3,744)
                                           ------            ---           ---------         ---------         --------
Balance at December 31, 1999               18,136            $18           $ 120,118         $(110,120)        $ 10,016
                                           ======            ===           =========         =========         ========
</TABLE>




                             See accompanying notes.


                                       25
<PAGE>   27

                          CAMBRIDGE NEUROSCIENCE, INC.
                      CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (in thousands)

<TABLE>
<CAPTION>
                                                                             YEAR ENDED DECEMBER 31,
                                                                   ---------------------------------------------
                                                                     1999              1998               1997
                                                                   -------           --------           --------
<S>                                                                <C>               <C>                <C>
Operating Activities
   Net loss                                                        $(3,744)          $ (2,894)          $(13,838)
   Items not requiring cash:
     Gain on sale of equipment, furniture and fixtures                  --                (38)                --
     Depreciation and amortization                                     197                337                851
     Common stock issued pursuant to an
      employee benefit plan                                             --                151                230
                                                                   -------           --------           --------
                                                                    (3,547)            (2,444)           (12,757)
Changes in operating assets and liabilities:
   Receivables from collaboration agreements                         1,909             (2,080)                --
   Prepaid expenses and other current assets                           769                315               (304)
   Accounts payable and accrued expenses                              (884)            (2,031)              (121)
   Research and development advances                                  (250)            (2,650)            (2,884)
                                                                   -------           --------           --------
                                                                     1,544             (6,446)            (3,309)
                                                                   -------           --------           --------
     Cash used for operating activities                             (2,003)            (8,890)           (16,066)

Investing Activities
   Purchases of marketable securities                               (7,503)           (13,670)           (35,561)
   Sales of marketable securities                                    8,051             33,194              9,000
   Purchase of equipment, furniture and fixtures                      (105)               (18)              (301)
   Disposals of equipment, furniture and fixtures                       --                 77                 --
                                                                   -------           --------           --------
     Cash provided by (used for) investing activities                  443             19,583            (26,862)

Financing Activities
   Dividend Paid                                                        --            (17,907)                --
   Sales of common stock, net of offering
     costs of $2,221 in 1997                                            30                 57             28,284
                                                                   -------           --------           --------
     Cash provided by (used for) financing activities                   30            (17,850)            28,284

Net decrease in Cash and Cash Equivalents                           (1,530)            (7,157)           (14,644)

Cash and Cash Equivalents at beginning of year                       4,863             12,020             26,664
                                                                   -------           --------           --------
Cash and Cash Equivalents at end of year                           $ 3,333           $  4,863           $ 12,020
                                                                   =======           ========           ========
</TABLE>


                             See accompanying notes.


                                       26
<PAGE>   28


                          CAMBRIDGE NEUROSCIENCE, INC.
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

NOTE A - BUSINESS

      Cambridge NeuroScience, Inc. (the "Company") is a biopharmaceutical
company engaged in the discovery and development of pharmaceuticals to prevent
or treat severe disorders of, or injuries to, the nervous system. The Company is
focused in two areas of research and development: (i) ion-channel blockers to
prevent or treat brain damage resulting from stroke and other forms of brain
ischemia, as well as for the treatment or prevention of neuropathic pain,
glaucoma, spinal cord injury, Parkinson's disease, multiple sclerosis ("MS") and
peripheral neuropathies, and (ii) growth factors for the treatment of MS and
peripheral neuropathies. To date, the Company has funded its operations
primarily through proceeds from public and private offerings of equity
securities and from payments received pursuant to research and development
collaborations. The Company has not been profitable since inception and has not
received any revenue from the sale of products.

NOTE B - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

      Principles of Consolidation. The consolidated financial statements include
the accounts of Cambridge NeuroScience, Inc. and its wholly-owned and
majority-owned subsidiaries. Minority shareholders have not made equity
investments in the majority-owned subsidiary. As a result, the entire net loss
of the majority-owned subsidiary has been attributed to the Company. All
inter-company accounts and transactions have been eliminated in consolidation.
(See Note H).

      Use of Estimates. The preparation of the financial statements in
conformity with accounting principles generally accepted in the United States
requires management to make estimates and assumptions that affect the amounts
reported in the financial statements and accompanying notes. Actual results
could differ from those estimates.

      Adoption of New Accounting Principles

      In December 1999, the staff of the Securities and Exchange Commission
issued Staff Accounting Bulletin No. 101, Revenue Recognition in Financial
Statements (SAB 101). SAB 101 summarizes certain of the staff's views in
applying generally accepted accounting principles to revenue recognition in
financial statements. SAB 101 requires a company to follow its guidance no later
than the first quarter of its fiscal year beginning after December 15, 1999
through a cumulative effect of a change in accounting principle. The Company has
evaluated its revenue recognition policies in consideration of SAB 101, and does
not expect adoption of this standard to have a material effect on its financial
statements.

      In June 1998, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards No. 133, (FAS 133) "Accounting for Derivative
Instruments and Hedging Activities", which required adoption in periods
beginning after June 15, 1999. FAS 133 was subsequently amended by FAS 137
"Accounting for Derivative Instruments and Hedging Activities--Deferral of the
Effective Date of FASB Statement No. 133" and will now be effective for fiscal
years beginning after June 15, 2000, with earlier adoption permitted. The
Company believes the adoption of this new accounting standard will not have a
significant effect on its financial statements.

      Cash Equivalents. The Company's policy regarding investments is to ensure
safety, liquidity, and capital preservation while obtaining a reasonable rate of
return. The Company considers all highly liquid instruments with a maturity of
90 days or less at the date of purchase to be cash equivalents. Such monies are
invested primarily in high quality corporate bonds and commercial paper, U.S.
Government and agency obligations and repurchase agreements. At December 31,
1999 and 1998, the cost of these investments approximated fair market value.

      Marketable Securities. At December 31, 1999 and 1998, the Company had $6.5
million and $7.0 million, respectively, invested in marketable securities with
original maturities between 90 days and one year, consisting of high quality
corporate bonds, commercial paper and certificates of deposit (see Note C). As
the Company intends that these investments be available for use in the Company's
current operations, these amounts are classified as "available-for-sale" and are
included in current assets. Management determines the appropriate classification
of its securities at the time of purchase and



                                       27
<PAGE>   29
reevaluates such classification at each balance sheet date. Available-for-sale
securities are carried at amortized cost, which approximated fair market value,
based on quoted market prices, at December 31, 1999 and 1998.  Unrealized gains
or losses, if material, are reported as a separate component of stockholders'
equity. As of December 31, 1999 and 1998, unrealized gains or losses were not
material. The cost of securities is adjusted for amortization of premiums and
accretion of discounts to maturity. Such amortizations, interest income and
realized gains and losses are included in interest income. The cost of
securities sold is based on specific identification. Gross realized gains or
losses for the years ended December 31, 1999, 1998 and 1997 were not material.

      Equipment, Furniture and Fixtures. Equipment, furniture and fixtures are
recorded at cost. Depreciation is provided using the straight-line method over
the following estimated useful lives:

      Equipment, furniture
        and fixtures ................. 3 - 5 years
      Leasehold improvements ......... Useful life or term of the lease,
                                       whichever is shorter

      Stock-Based Compensation. The Company accounts for its stock-based
employee compensation arrangements under the provisions of Accounting Principles
Board Opinion 25, Accounting for Stock Issued to Employees and related
interpretations (see Note G).

      Revenue Recognition. Research and development revenue is earned
pursuant to licensing agreements and reimbursements of the Company's
expenditures pursuant to the terms of research and development collaborations.
Revenue from government grants is recorded as earned based on the performance
requirements of the grant. Revenue is deemed earned when all of the following
have occurred: all obligations of the Company relating to the revenue have been
met and the earnings process has been culminated; the monies received or
receivable are not refundable irrespective of research results; and there are
neither future obligations nor future milestones to be met by the Company with
respect to such revenue. Expenses relating to research and development
collaborations and government grants are recorded as research and development
expenses. Amounts received in advance of research and development performed are
designated as research and development advances and are included in current
liabilities. (See Note H).

      Income Taxes. The liability method is used to account for income taxes.
Deferred tax assets and liabilities are determined based on differences between
financial reporting and income tax bases of assets and liabilities as well as
net operating loss carryforwards and are measured using the enacted tax rates
and laws that will be in effect when the differences are expected to reverse.
Deferred tax assets may be reduced by a valuation allowance to reflect the
uncertainty associated with their ultimate realization.

      Significant Customers. Revenue in 1999, 1998 and 1997 consisted primarily
of revenue arising from collaborative agreements. Revenue from these sources in
1999 was earned pursuant to agreements with Allergan, Bayer and BI. Revenue
earned pursuant to the Allergan agreement totaled 71%, 23% and 25% of revenue in
1999, 1998 and 1997, respectively. Revenue earned pursuant to the Bayer
agreement totaled 29%, 37% and 0% in 1999, 1998 and 1997, respectively, and
revenue earned pursuant to the BI agreement, which was terminated in 1998,
totaled 0%, 27% and 71% in 1999, 1998 and 1997, respectively. (See Note H).

      Net loss per share. Net loss per share is based on the weighted-average
number of common shares outstanding during each of the periods presented. Due to
the fact that the Company is in a net loss position, common equivalent shares
from stock options are excluded as their effect is antidilutive.




                                       28
<PAGE>   30

                          CAMBRIDGE NEUROSCIENCE, INC.
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (continued)

NOTE C - MARKETABLE SECURITIES

Investments in marketable securities consist of the following at December 31
(in thousands):

                                                   CONTRACTUAL MATURITIES
                                                   ----------------------
                                                      1999        1998
                                                   ---------    ---------
                                                   Less than    Less than
                                                    one year     one year
                                                   ---------    ---------
Corporate bonds                                      $4,508       $6,037
Commercial paper                                      1,981           --
Certificates of deposit                                  --        1,000
                                                     ------       ------
                                                     $6,489       $7,037
                                                     ======       ======

NOTE D - EQUIPMENT, FURNITURE AND FIXTURES

Equipment, furniture and fixtures
 consist of the following (in thousands):               DECEMBER 31,
                                                    --------------------
                                                      1999         1998
                                                    -------      -------
Equipment                                           $ 4,178      $ 4,181
Furniture and fixtures                                  151          151
Leasehold improvements                                2,264        2,264
                                                    -------      -------
                                                      6,593        6,596
Less accumulated depreciation and amortization       (6,308)      (6,219)
                                                    -------      -------
Equipment, furniture and fixtures, net              $   285      $   377
                                                    =======      =======


NOTE E - ACCOUNTS PAYABLE AND ACCRUED EXPENSES

Accounts payable and accrued expenses
 consist of the following (in thousands):                 DECEMBER 31,
                                                       -----------------
                                                       1999        1998
                                                       ----       ------
Accounts payable                                       $100       $  454
Accrued salaries and benefits                            98          293
Accrued research and development expense                 71          290
Accrued professional fees                               145          150
Sublease advances                                       268          234
Accrued other                                            71          216
                                                       ----       ------
                                                       $753       $1,637
                                                       ====       ======




                                       29
<PAGE>   31

NOTE F - INCOME TAXES

      At December 31, 1999, the Company had a potential tax benefit of
approximately $45.7 million, resulting primarily from approximately $108.2
million in net operating loss carryforwards and $5.1 million of tax credits,
which expire through 2019. Since the Company has incurred only losses since
inception and due to the degree of uncertainty related to the ultimate
utilization of the loss and credit carryforwards, the Company has fully reserved
this tax benefit. Additionally, the future utilization of net operating loss
carryforwards may be subject to limitations under the change in stock ownership
rules of the Internal Revenue Code of 1986, as amended. During 1999, the
valuation allowance increased by approximately $1.9 million due primarily to the
increase in federal and state net operating loss carryforwards and research and
development credits, partially offset by the expiration of state net operating
loss carryforwards.

      Significant components of the Company's deferred tax assets are as follows
(in thousands):

                                                        DECEMBER 31,
                                                   ----------------------
                                                     1999          1998
                                                   --------      --------

      Deferred tax assets
         Net operating loss carryforwards          $ 40,605      $ 39,600
         Tax credits                                  5,089         4,175
                                                   --------      --------
      Total deferred tax assets                      45,694        43,775
         Valuation allowance                        (45,694)      (43,775)
                                                   --------      --------
      Net deferred tax assets                      $     --      $     --
                                                   ========      ========


NOTE G - STOCKHOLDERS' EQUITY

      Preferred Stock. The Board of Directors is authorized to fix designations,
relative rights, preferences and limitations on the preferred stock at the time
of issuance.

      Equity Incentive Plans. The Company has a 1991 Equity Incentive Plan (the
"Plan"), which provides for the granting of options to purchase 2,100,000 shares
of the Company's Common Stock. The Plan provides for the issuance or award of
incentive stock options at no less than the fair market value at the date of the
grant, non-qualified stock options, stock appreciation rights, performance
shares, restricted Common Stock, and stock units at prices to be determined by
the Board of Directors. All employees and, in the case of awards other than
incentive stock options, consultants to the Company are eligible for awards
under the Plan. At December 31, 1999, options to purchase 1,305,930 shares were
outstanding under the plan, of which 821,421 were exercisable.

      In addition, the Company has a 1992 Director Stock Option Plan (the
"Director Plan"), pursuant to which non-qualified stock options to purchase
20,000 shares of the Company's Common Stock are automatically granted to outside
directors at fair market value upon their initial election to the Board of
Directors. Additional grants of options may be made to eligible directors at the
discretion of the Board of Directors. The Director Plan has reserved an
aggregate of 100,000 shares for this purpose. At December 31, 1999, options to
purchase 98,000 were outstanding under the plan, of which 68,375 were
exercisable.

      The term of all stock options granted may not exceed ten years, and
vesting generally is over a four-year period.



                                       30

<PAGE>   32

                          CAMBRIDGE NEUROSCIENCE, INC.
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (continued)

         The following table presents the combined activity of the two option
plans for the years ended December 31:

<TABLE>
<CAPTION>
                                                   1999                       1998                       1997
                                          ----------------------     ----------------------    -------------------------
                                                        Weighted                   Weighted                     Weighted
                                                         Average                    Average                      Average
                                                        Exercise                   Exercise                     Exercise
                                           Options        Price       Options        Price        Options         Price
                                          ---------     --------     ---------     --------      ---------      --------
<S>                                       <C>             <C>        <C>             <C>         <C>             <C>
Outstanding at
beginning of year                         1,183,256       $5.20      1,662,727       $7.71       1,493,953       $ 6.92

Granted                                     262,750        0.71        432,000        0.84         293,450        11.56

Exercised                                        --          --             --          --         (10,684)        5.03

Canceled                                    (42,076)       4.28       (911,471)       7.72        (113,992)        7.51
                                          ---------       -----      ---------       -----      ----------       ------
Outstanding at year end                   1,403,930       $4.39      1,183,256       $5.20       1,662,727       $ 7.71
                                          =========       =====      =========       =====      ==========       ======
Exercisable at year end                     889,796       $6.02        686,204       $6.87       1,079,048       $ 7.09
                                          =========       =====      =========       =====      ==========       ======
Weighted average grant date fair
value per share of options
granted during the year                                   $0.59                      $0.66                       $ 8.15
                                                          =====                      =====                       ======
</TABLE>

         The following table presents weighted average price and life
information about significant option groups outstanding at December 31, 1999:

<TABLE>
<CAPTION>
                                          Options Outstanding                              Options Exercisable
                            -------------------------------------------------        --------------------------------
                                              Weighted
                                               Average           Weighted                                Weighted
Range of                        Number        Remaining           Average              Number             Average
Exercise Prices              Outstanding     Life (years)      Exercise price        Exercisable       Exercise Price
----------------             -----------     ------------      --------------        -----------       --------------
<S>                           <C>                 <C>              <C>                 <C>                 <C>
$ 0.69  -  1.00                 669,750           8.7             $ 0.79               198,375            $ 0.81
  3.13  -  6.13                 235,750           4.3               5.36               233,562              5.38
  6.50  -  8.00                 226,680           4.6               7.27               210,879              7.21
  8.13  -  9.75                 171,500           3.8               8.70               171,500              8.70
 11.25  - 13.00                 100,250           6.1              12.25                75,480             12.22
                              ---------                                                -------
                              1,403,930                                                889,796
                              =========                                                =======
</TABLE>

         Employee Stock Purchase Plan. The 1993 Employee Stock Purchase Plan
(the "ESPP") provides for the grant of rights to eligible employees to purchase
shares of the Company's Common Stock at the lesser of 85% of the fair market
value at the beginning or the end of an established offering period. 250,000
shares have been authorized for issuance under this plan, of which 143,956 have
been issued as of December 31, 1999.  During 1999, 14,313 shares were issued at
$.50 per share and 36,180 were issued at $.64 per share. During 1998, 23,065
shares were issued at $1.67 per share and 37,222 were issued at $0.50 per share.
During 1997, 6,570 shares were issued at $6.59 per share and 13,762 were issued
at $3.51 per share.

         FAS 123 Disclosures. The Company has adopted the disclosure provisions
of Statement of Financial Accounting Standards No. 123, Accounting for
Stock-based Compensation ("FAS 123"), and accounts for its stock option plans in
accordance with the provisions of APB 25, Accounting for Stock Issued to
Employees. The exercise price of grant awards made under the Company's stock
option plans is equal to the fair market value at the date of grant.


                                       31
<PAGE>   33


      Pursuant to APB 25, the Company applies the intrinsic value method to
grant awards. Accordingly, no compensation cost has been recognized in relation
to the stock option plans or the ESPP.

      Pursuant to the requirements of FAS 123, the following are the pro forma
net loss and net loss per share for 1999, 1998 and 1997, as if the compensation
cost for the option plans and the ESPP had been determined based on the fair
value at the grant date for grants in 1999, 1998 and 1997, consistent with the
provisions of FAS 123:


<TABLE>
<CAPTION>
                                                 1999                        1998                         1997
                                      ------------------------    ------------------------     -------------------------
                                      As Reported    Pro Forma    As Reported    Pro Forma     As Reported     Pro Forma
                                      -----------    ---------    -----------    ---------     -----------     ---------

<S>                                     <C>           <C>           <C>           <C>           <C>            <C>
Net loss (in thousands)                 $(3,744)      $(4,102)      $(2,894)      $(2,777)      $(13,838)      $(15,583)

Net loss per share                      $ (0.21)      $ (0.23)      $ (0.16)      $ (0.16)      $  (0.79)      $  (0.89)
</TABLE>


      The grant-date fair values of options granted and shares issued pursuant
to the ESPP were estimated using the Black-Scholes model with the following
(table below) weighted average assumptions. The Black-Scholes model was
developed for use in estimating the fair value of traded options, which have no
vesting restrictions and are fully transferable. This  model requires the use of
subjective assumptions, including expected stock price volatility. In
management's opinion, such valuation models do not necessarily provide a
reliable single measure of the fair value of its employee stock options.:


<TABLE>
<CAPTION>
                                              Options                                      ESPP
                                 ---------------------------------          ---------------------------------
                                  1999          1998          1997           1999          1998          1997
                                 -----          ----          ----          -----          ----          ----

<S>                              <C>            <C>           <C>           <C>            <C>           <C>
Expected life (years)              6.5           6.5           5.2             .5            .5            .5
Interest rate                      4.9%          5.6%          6.3%           5.1%          5.4%          5.5%
Volatility                       103.0%         90.0%         83.0%         110.0%         92.0%         83.0%
</TABLE>


      In April 1998, the Company paid a $1.00 per share dividend representing a
return of capital to shareholders. Prior thereto and since then, the Company has
not declared nor paid dividends on any of its common stock. Future cash
dividends will be paid at the discretion of the Board of Directors and will
depend, among other things, upon the Company's future operations, capital
requirements, general financial condition and such other factors as the Board of
Directors may deem relevant. For the purposes of calculating fair value pursuant
to FAS 123, the Company has assumed that no dividends will be paid.

      The pro forma adjustments to net loss under FAS 123 in 1999, 1998 and
1997 were an increase in net loss of $358,000, decrease in net loss of $117,000,
and an increase in net loss of $1.7 million, respectively. The pro forma
adjustments for those years varied from year to year as a result of differences
each year in the factors affecting the calculation of the pro forma adjustment.
Those factors are: the number of options granted and cancelled; expected life of
options; interest rate; and volatility. In 1998, the pro forma decrease in net
loss resulted primarily from the cancellation of a substantial number of options
which had been held by employees who were terminated in 1998 as part of a
reduction of the Company's workforce. The pro forma effect of FAS 123 in future
years may fluctuate based on the factors described above.

      Benefit Plan. The Company has an employee savings plan that qualifies
under Section 401(k) of the Internal Revenue Code of 1986, as amended, in which
all eligible employees may participate. For the plan years ended December 31,
1998 and 1997, the Company matched 100% of all qualified employee contributions
with Company Common Stock. 330,000 shares were authorized and available for
issuance under the 401(k) plan. Through December 31, 1998, 329,115 shares had
been issued. Effective in 1999, the Company no longer utilizes Company stock in
its 401(k) plan, and instead has a cash match of 50% of all qualified employee
contributions.  401(k) match expense totaled $40,616, $151,329 and $229,269 for
the years ended December 31, 1999, 1998 and 1997, respectively.

      The aggregate number of shares of Common Stock available for issuance
under all stock plans was 753,240 at December 31, 1999.


                                       32
<PAGE>   34


NOTE H - COLLABORATIVE AGREEMENTS

      The Company has collaborative agreements with certain strategic partners.
These arrangements are as follows:

      Allergan. In November 1996, the Company entered into a collaboration
agreement with Allergan Inc. ("Allergan") to develop certain of the Company's
NMDA ion-channel blockers, sodium ion-channel blockers and combination
ion-channel blockers for the treatment of ophthalmic disorders, including
glaucoma. Upon signing the agreement, Allergan purchased 175,103 shares of the
Company's Common Stock for $3.0 million, and Allergan provided an additional
$3.0 million in research funding through November 1999. The agreement with
Allergan was amended in December 1999 to extend research funding for an
additional year and to expand the potential indications to include pain
treatment. Pursuant to the amendment, the Company will receive research funding
for the period November 1999 to November 2000 in the amount of $1.25 million.

      Allergan is responsible for developing and marketing potential products
and will bear all such costs. The Company may receive up to an additional $18.5
million in cash upon the achievement of certain milestones and will receive a
royalty on product sales. There can be no assurance as to when or if these
milestones will be achieved. Allergan has certain termination rights, including
the right, which is shared by the Company, to terminate the agreement upon 90
days' prior written notice of an uncured material breach by the other party.
Pursuant to the funding agreement, Allergan has provided $3.1 million to the
Company as of December 31, 1999, of which $1.0 million was included in research
and development revenue in 1999, 1998 and 1997. The Company is not obligated to
meet future milestones to earn this revenue and the monies received are not
refundable in the event research efforts are not successful.

      Bayer AG. In December 1998, the Company entered into a collaborative
agreement with Bayer AG ("Bayer") for the development of recombinant Glial
Growth Factor 2 ("GGF2") for the treatment of neurodegenerative diseases such as
multiple sclerosis ("MS"). In exchange for exclusive worldwide manufacturing and
marketing rights to the compound, the Company received an up front licensing fee
of $1.0 million and $1.0 million in reimbursements for research costs relating
to a research protocol covered by the agreement. Of this total $2.0 million
received, $420,000 and $1.6 million were recognized as revenue in 1999 and 1998,
respectively. The Company has substantially completed its research
responsibilities with respect to this agreement, and therefore does not
anticipate receiving any additional research funding from Bayer. Bayer is
responsible for development and marketing and all costs related thereto. The
Company may receive up to $24.0 million in milestone payments, and may receive
royalties on sales of GGF2 products. There can be no assurance, however, as to
when or if any milestones will be achieved or whether GGF2 will become a
marketed product. Either party may terminate this agreement at any time for
cause, and Bayer may terminate without cause by providing 120 days written
notice.

      Boehringer Ingelheim International, GmbH. In March 1995, the Company
entered into license and stock purchase agreements with Boehringer Ingelheim
International GmbH ("BI") to collaborate on the development and
commercialization of the Company's product candidate, aptiganel. The Company and
BI collaborated on two Phase III trials of aptiganel. In the second half of
1997, the Company announced the discontinuation of patient enrollment into both
trials after interim analyses indicated that continuation of the trials was not
justified. In November, 1998, the Company and BI terminated the collaboration
and licensing agreements for aptiganel and commercial rights were returned to
the Company, subject to a royalty on future sales.

      Under terms of the agreement, BI was responsible for generally 75% of all
costs incurred in the development of aptiganel. Revenue earned pursuant to this
agreement represented BI's reimbursement of the Company's research and
development expenditures in excess of the Company's 25% obligation. The
agreement provided that BI would advance cash to the Company in the event the
Company's expenditures were expected to exceed its contractual obligation. Such
advances were received by the Company in 1995 and 1996. Pursuant to the
termination of the collaboration in 1998, the Company and BI finalized their
accountings of research and development expenses incurred pursuant to the
agreement. As a result of the final accounting, the Company repaid to BI $1.5
million in excess advances received in prior years. The Company recognized $1.2
million in revenue in 1998, representing the remainder of excess advances
received in prior periods. Revenue recognized in 1997 pursuant to this agreement
totaled $2.9 million. The Company will recognize no further revenue pursuant to
this collaboration.

      Cambridge NeuroScience Partners, Inc. In December 1996, the Company
entered into a collaboration agreement



                                       33
<PAGE>   35

with The J. David Gladstone Institutes ("Gladstone") and The Regents of the
University of California (the "University") for the development of treatments
for Alzheimer's disease and other neurological diseases, disorders or injuries.
In connection with the collaboration, the Company formed a subsidiary, Cambridge
NeuroScience Partners, Inc. ("CNPI"). Cambridge NeuroScience made a $1.25
million equity investment in CNPI upon the consummation of the collaboration and
owns 80% of the outstanding common stock of CNPI, with Gladstone and the
University owning 15% and 5%, respectively, of the remaining outstanding shares
of CNPI common stock.

      Pursuant to the terms of the collaboration, Gladstone conducted a research
program over a three-year period through December 1999, for which CNPI provided
funding of $1.25 million per year. Pursuant to the agreement, Cambridge
NeuroScience provided CNPI, interest-free, all amounts necessary for CNPI to
make such payments. CNPI had a three-year option to acquire an exclusive
royalty-bearing license to intellectual property developed in the field of
research under the collaboration. Expenses relating to this agreement included
in research and development expense totaled $1.3 million in 1999 and $1.4
million in 1998 and 1997. As of December 31, 1999, the Company and CNPI had
completed their funding obligation pursuant to this agreement and decided not
to exercise a license to the intellectual property. As such, the Company does
not anticipate incurring additional research costs for this program.

      Creative Biomolecules, Inc. On December 31, 1998, the Company entered into
a technology licensing agreement with Creative Biomolecules, Inc. ("CBMI")
whereby CBMI has acquired the exclusive rights to GDF-1 in exchange for an up
front cash payment and future royalties on product sales. Either party may
terminate this agreement upon a material breach which is not cured within 60
days of written notice of such breach. The Company has no future obligations
with respect to this agreement.

NOTE I - COMMITMENTS

         The Company leases its office and research facilities under the terms
of an agreement, which expires in July 2000. Under terms of this lease, the
Company pays property taxes, insurance, maintenance, and expenses related to the
leased property. Rent expense relating to this lease was approximately $1.6
million in the year ended December 31, 1999, $1.3 million in 1998 and $1.1
million in 1997. The Company's lease expires in July 2000. In anticipation of
this expiration, the Company is evaluating a number of potential facility lease
opportunities, and expects to lease approximately 10,000 square feet of space.
The Company cannot currently estimate the amounts of minimum rental commitments
for future years with respect to such potential lease.

      In June 1998, the Company sub-leased approximately half of its office and
laboratory facilities to a third party. Under terms of the sublease agreement,
which expires in July 2000, the sub-lessee pays a base rent amount and a
pro-rata share of insurance, maintenance, utilities and other operating expenses
relating to the facility. In 1999 and 1998, the Company received $864,000 and
$392,000, respectively, in minimum sub-lease rentals pursuant to this agreement.

Minimum future obligations and rentals under the terms of the facilities lease
and sub-lease agreement are (in thousands):

                                              Future         Future
                                          Minimum Lease     Minimum
                                           Obligations      Rentals
                                          -------------     -------

               2000                            $645           $504
                                               ----           ----
               Total                           $645           $504
                                               ====           ====


      The Company has no material, non-cancelable commitments as of December 31,
1999.

NOTE J - RESTRUCTURING

      In March 1998, the Company implemented a restructuring plan that included
a reduction in staff by 34 employees, consisting of 22 research, four drug
development and eight administrative and support employees. Included in
operating expenses for the year ended December 31, 1998 was a one-time cost of
$921,000 associated with this reduction in staff, consisting primarily of
severance and related benefits, which were paid in full in 1998. Following the
reduction in headcount, in June 1998, the Company sub-leased approximately half
of its office and laboratories facilities to a third party thereby reducing
facilities related operating expenses. (See Note I)



                                       34
<PAGE>   36

ITEM 9.     CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND
FINANCIAL DISCLOSURE

      None.

PART III

ITEM 10.    DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

      The response to this item is contained in part under the caption
"Executive Officers of the Company" in Part I, Item 1(a) hereof, and the
remainder is incorporated herein by reference from the discussion responsive
thereto under the caption "Election of Directors" in the Company's definitive
Proxy Statement relating to the 2000 Annual Meeting of Stockholders (the "2000
Proxy Statement"), to be filed with the Securities and Exchange Commission not
later than April 30, 2000.

ITEM 11.    EXECUTIVE COMPENSATION

      The response to this item is incorporated herein by reference from the
discussion responsive thereto under the caption "Executive Compensation" in the
2000 Proxy Statement.

                                       35
<PAGE>   37

ITEM 12.    SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

          The response to this item is incorporated herein by reference from the
discussion responsive thereto under the caption "Principal Stockholders" in the
2000 Proxy Statement.

ITEM 13.    CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

          The response to this item is incorporated by reference from the
discussion responsive thereto under the captions "Employment Agreements" and
"Compensatory Arrangements" in the 2000 Proxy Statement.

PART IV

ITEM 14.    EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K

(a)(1)      FINANCIAL STATEMENTS

          The following Financial Statements of the Company are included in
response to Item 8 of this report:

                                                                           PAGE
                                                                           ----

          Index to Consolidated Financial Statements                        21

          Report of Independent Auditors                                    22

          Consolidated Balance Sheets                                       23

          Consolidated Statements of Operations                             24

          Consolidated Statements of Changes in Stockholders' Equity        25

          Consolidated Statements of Cash Flows                             26

          Notes to Consolidated Financial Statements                        27

(a)(2)      FINANCIAL STATEMENT SCHEDULES

          No financial statement schedules are included since they are either
not required, not applicable, or the information is otherwise included.

(a)(3)      EXHIBITS

 3.1      Restated Certificate of Incorporation of Registrant. Filed as Exhibit
          4.1 to Registration Statement on Form S-8, File No. 33-42933, and
          incorporated herein by reference.

 3.2      Amended and Restated By-laws of Registrant. Filed as Exhibit 3.1 to
          Quarterly Report on Form 10-Q for the quarter ended June 30, 1999, as
          filed with the Commission August 11, 1999, and incorporated herein by
          reference.

 4.1      Specimen Stock Certificate for Common Stock, $.001 par value. Filed as
          Exhibit 4.1 to Registration Statement on Form S-1, File No. 33-40078,
          and incorporated herein by reference.

10.1      Stockholders' Agreement dated December 29, 1988 among the Company and
          certain investors, as amended by Waiver and Consent dated as of
          February 5, 1991. Filed as Exhibit 10.3 to Registration Statement on
          Form S-1, File No. 33-40078, and incorporated herein by reference.



                                       36
<PAGE>   38

10.2      Scientific Advisor Agreement dated September 10, 1986 and amendment
          dated December 6, 1986 between the Company and Dr. Joseph Martin.
          Filed as Exhibit 10.5 to Registration Statement on Form S-1, File No.
          33-40078, and incorporated herein by reference.

10.3      Form of Stockholders' Agreement dated March 19, 1987 among the Company
          and certain stockholders. Filed as Exhibit 10.6 to Registration
          Statement on Form S-1, File No. 33-40078, and incorporated herein by
          reference.

10.4      Form of Restricted Stock Purchase Agreement with a certain Director
          and executive officers. Filed as Exhibit 10.8 to Registration
          Statement on Form S-1, File No. 33-40078, and incorporated herein by
          reference.

10.5      Common Stock Purchase Warrant dated February 15, 1991 with Aeneas
          Venture Corporation. Filed as Exhibit 10.9 to Registration Statement
          on Form S-1, File No. 33-40078, and incorporated herein by reference.

10.6      Form of Waiver, Consent and Agreement dated as of April 22, 1991
          between the Company and certain investors. Filed as Exhibit 10.10 to
          Registration Statement on Form S-1, File No. 33-40078, and
          incorporated herein by reference.

10.9*     Letter Agreement dated June 5, 1990 between the Company and Elkan R.
          Gamzu, Ph.D. Filed as Exhibit 10.13 to Registration Statement on Form
          S-1, File No. 33-40078, and incorporated herein by reference.

10.11*    1991 Equity Incentive Plan, as amended. Filed as Exhibit 99.1 to the
          Registration Statement on Form S-8, File No. 333-05431, as filed with
          the Commission on June 7, 1996, and incorporated herein by reference.

10.12*    1992 Director Stock Option Plan, as amended. Filed as exhibit 10.12 to
          the Annual Report on Form 10-K for the period ended December 31, 1997,
          as filed with the Commission on March 30, 1998, and incorporated
          herein by reference.

10.13     Lease for One Kendall Square dated July 16, 1992 between the Company
          and the Trustees of Old Kendall Realty Trust and addendum dated as of
          September 22, 1992 (the "Lease"). Filed as Exhibit 10.13 to the Annual
          Report on Form 10-K for the period ended December 31, 1992, as filed
          with the Commission on March 28, 1993, and incorporated herein by
          reference. Addendum dated September 22, 1993, filed as Exhibit 10.13
          to the Annual Report on Form 10-K for the period ended December 31,
          1993, as filed with the Commission on February 14, 1994, and
          incorporated herein by reference. Addendum dated March 11, 1996, as
          filed with the Commission on March 24, 1997, and incorporated herein
          by reference. Addendum dated June 17, 1997, filed as Exhibit 10.13 to
          the Annual Report on Form 10-K for the period ended December 31, 1997,
          as filed with the Commission on March 30, 1998 and incorporated herein
          by reference.

10.15*    Form of Indemnification agreement between the Company and Directors
          and executive officers. Filed as Exhibit 10.15 to the Annual Report on
          Form 10-K for the period ended December 31, 1992, as filed with the
          Commission on March 28, 1993, and incorporated herein by reference.

10.16+    Stock Purchase Agreement dated as of March 21, 1995 between the
          Company and Boehringer Ingelheim International GmbH. Filed as Exhibit
          10.16 to the Annual Report on Form 10-K for the period ended December
          31, 1994, as filed with the Commission on March 31, 1995, and
          incorporated herein by reference.

10.17+    License Agreement dated as of March 21, 1995 between the Company and
          Boehringer Ingelheim International GmbH. Filed as Exhibit 10.17 to the
          Annual Report on Form 10-K for the period ended December 31, 1994, as
          filed with the Commission on March 31, 1995, and incorporated herein
          by reference.



                                       37
<PAGE>   39

10.18+    Amendment to Stock Purchase Agreement and License Agreement between
          the Company and Boehringer Ingelheim International GmbH dated as of
          August 19, 1996. Filed as Exhibit 99.4 to Amendment No. 1 to the
          Current Report on Form 8-K/A dated August 19, 1996, as filed with the
          Commission on January 29, 1997, and incorporated herein by reference.

10.19+    Collaborative Research, Development and Marketing Agreement dated as
          of November 20, 1996 between the Company and Vision Pharmaceuticals
          L.P., d/b/a Allergan, Inc. Filed as Exhibit 99.1 to Amendment No. 1 to
          the Current Report on Form 8-K/A dated August 19, 1996, as filed with
          the Commission on January 29, 1997, and incorporated herein by
          reference.

10.20+    Stock Purchase Agreement dated as of November 20, 1996 between the
          Company and Vision Pharmaceuticals L.P., d/b/a Allergan, Inc. Filed as
          Exhibit 99.2 to Amendment No. 1 to the Current Report on Form 8-K/A
          dated August 19, 1996, as filed with the Commission on January 29,
          1997, and incorporated herein by reference.

10.21+    Credit Agreement dated as of November 20, 1996 between the Company and
          Vision Pharmaceuticals L.P, d/b/a Allergan, Inc. Filed as Exhibit 99.3
          to Amendment No. 1 to the Current Report on Form 8-K/A dated August
          19, 1996, as filed with the Commission on January 29, 1997, and
          incorporated herein by reference.

10.22+    Sponsored Research and Collaborative Agreement dated as of December
          23, 1996 between Cambridge NeuroScience Partners, Inc. and The J.
          David Gladstone Institutes. Filed as Exhibit 99.1 to Amendment No. 1
          to the Current Report on Form 8-K/A dated December 23, 1996, as filed
          with the Commission on January 29, 1997, and incorporated herein by
          reference.

10.23+    Option Agreement dated as of December 23, 1996 by and among The
          Regents of the University of California, Cambridge NeuroScience
          Partners, Inc., and the Company. Filed as Exhibit 99.2 to Amendment
          No. 1 to the Current Report on Form 8-K/A dated December 23, 1996, as
          filed with the Commission on January 29, 1997, and incorporated herein
          by reference.

10.24+    Stockholders' Rights Agreement dated as of December 23, 1996 by and
          among the Company, Cambridge NeuroScience Partners, Inc., The J. David
          Gladstone Institutes and The Regents of the University of California.
          Filed as Exhibit 99.3 to Amendment No. 1 to the Current Report on Form
          8-K/A dated December 23, 1996, as filed with the Commission on January
          29, 1997, and incorporated herein by reference.

10.25*    Compensatory arrangement with certain executive officers and other
          members of management. Filed as Exhibit 10.25 to the Annual Report on
          Form 10-K for the period ended December 31, 1997, filed with the
          Commission on March 30, 1998 and incorporated herein by reference.

10.26     Termination agreement dated November 4, 1998, between the Company and
          Boehringer Ingelheim International, GmbH. Filed as exhibit 10.28 to
          the Quarterly Report on Form 10-Q for the quarter ended September 30,
          1998, as filed with the Commission on November 12, 1998, and
          incorporated herein by reference.

10.27+    Research Collaboration and License Agreement dated as of December 23,
          1998 between the Company and Bayer AG. Filed as exhibit 10.27 to the
          Annual Report on Form 10-K for the period ended December 31, 1998,
          filed with the Commission on March 31, 1999, and incorporated herein
          by reference.

10.28#    Amendment to Collaborative Research, Development and Marketing
          Agreement dated December 1999, between the Company and Vision
          Pharmaceuticals L.P, d/b/a Allergan, Inc.

21.1#     Subsidiaries of the Company. Filed herewith.



                                       38
<PAGE>   40

23.1#     Consent of Ernst & Young LLP, independent auditors. Filed herewith.

24.1      Powers of Attorney. Contained on signature page hereto.

27.1#     Financial Data Schedule for the year ended December 31, 1999.

99.1      Important Factors Regarding Forward-Looking Statements. Filed
          herewith.

------------------
      * Identifies a management contract or compensatory plan or agreement in
        which an executive officer or Director of the Company participates.

      + Confidential information contained in this Exhibit has been omitted and
        filed separately with the Securities and Exchange Commission.

      # Filed electronically in connection with the Annual Report on Form 10-K
        for the year ended December 31, 1999.

(b)         REPORTS ON FORM 8-K

      None.





                                       39

<PAGE>   41


                                   SIGNATURES

           Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.

           Date: March 8, 2000              CAMBRIDGE NEUROSCIENCE, INC.

                                       By: /s/ Harry W. Wilcox
                                           -------------------------------------
                                           Harry W. Wilcox, III
                                           President and Chief Executive Officer

                                       By: /s/ Glenn A. Shane
                                           -------------------------------------
                                           Glenn A. Shane
                                           Controller and Treasure

                                POWER OF ATTORNEY

           We, the undersigned Directors of Cambridge NeuroScience, Inc., hereby
severally constitute and appoint Robert N. McBurney, Harry W. Wilcox, III and
William T. Whelan and each of them singly, our true and lawful
attorneys-in-fact, with full power to them and each of them to sign for us, in
our names and in the capacity indicated below, the Annual Report on Form 10-K of
Cambridge NeuroScience, Inc., for fiscal year 1999, and any and all amendments
thereto, and to file the same, with exhibits thereto and other documents in
connection therewith, with the Securities and Exchange Commission hereby
ratifying and confirming all that each of said attorneys-in-fact may lawfully do
or cause to be done by virtue hereof.

           Pursuant to the requirements of the Securities Exchange Act of 1934,
this report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.

           WITNESS our hands on the dates set forth below:

           SIGNATURE         TITLE                             DATE
           ---------         -----                             ----

/s/ Harry W. Wilcox          President, Chief                  March 8, 2000
-------------------------    Executive Officer and Director
Harry W. Wilcox, III         (Principal Financial Officer)

/s/ Nancy S. Amer            Director                          March 8, 2000
-------------------------
Nancy S. Amer

/s/ Burkhard Blank           Director                          March 8, 2000
-------------------------
Burkhard Blank

/s/ Ira A. Jackson           Director                          March 8, 2000
-------------------------
Ira A. Jackson

/s/ Joseph B. Martin         Director                          March 8, 2000
-------------------------
Joseph B. Martin

/s/ Paul C. O'Brien          Director                          March 8, 2000
-------------------------
Paul C. O'Brien




                                       40
<PAGE>   42


                                  EXHIBIT INDEX


NUMBER                              DESCRIPTION
------                              -----------

 3.1       Restated Certificate of Incorporation of Registrant. Filed as Exhibit
           4.1 to Registration Statement on Form S-8, File No. 33-42933, and
           incorporated herein by reference.

 3.2       Amended and Restated By-Laws of Registrant.  Filed as Exhibit 3.1 to
           Quarterly Report on Form 10-Q for the quarter ended June 30, 1999 as
           filed with the Commission August 11, 1999, and incorporated herein by
           reference.

 4.1       Specimen Stock Certificate for Common Stock, $.001 par value. Filed
           as Exhibit 4.1 to Registration Statement on Form S-1, File No.
           33-40078, and incorporated herein by reference.

10.1       Stockholders' Agreement dated December 29, 1988 among the Company and
           certain investors, as amended by Waiver and Consent dated as of
           February 5, 1991. Filed as Exhibit 10.3 to Registration Statement on
           Form S-1, File No. 33-40078, and incorporated herein by reference.

10.2       Scientific Advisor Agreement dated September 10, 1986 and amendment
           dated December 6, 1986 between the Company and Dr. Joseph Martin.
           Filed as Exhibit 10.5 to Registration Statement on Form S-1, File No.
           33-40078, and incorporated herein by reference.

10.3       Form of Stockholders' Agreement dated March 19, 1987 among the
           Company and certain stockholders. Filed as Exhibit 10.6 to
           Registration Statement on Form S-1, File No. 33-40078, and
           incorporated herein by reference.

10.4       Form of Restricted Stock Purchase Agreement with a certain Director
           and executive officers. Filed as Exhibit 10.8 to Registration
           Statement on Form S-1, File No. 33-40078, and incorporated herein by
           reference.

10.5       Common Stock Purchase Warrant dated February 15, 1991 with Aeneas
           Venture Corporation. Filed as Exhibit 10.9 to Registration Statement
           on Form S-1, File No. 33-40078, and incorporated herein by reference.

10.6       Form of Waiver, Consent and Agreement dated as of April 22, 1991
           between the Company and certain investors. Filed as Exhibit 10.10 to
           Registration Statement on Form S-1, File No. 33-40078, and
           incorporated herein by reference.

10.9*      Letter Agreement dated June 5, 1990 between the Company and Elkan R.
           Gamzu, Ph.D. Filed as Exhibit 10.13 to Registration Statement on Form
           S-1, File No. 33-40078, and incorporated herein by reference.

10.11*     1991 Equity Incentive Plan, as amended. Filed as Exhibit 99.1 to the
           Registration Statement on Form S-8, File No. 333-05431, as filed with
           the Commission on June 7, 1996, and incorporated herein by reference.

10.12*     1992 Director Stock Option Plan, as amended. Filed as exhibit 10.12
           to the Annual Report on Form 10-K for the period ended December 31,
           1997, as filed with the Commission on March 30, 1998, and
           incorporated herein by reference.

10.13      Lease for One Kendall Square dated July 16, 1992 between the Company
           and the Trustees of Old Kendall Realty Trust and addendum dated as of
           September 22, 1992 (the "Lease"). Filed as Exhibit 10.13 to the
           Annual Report on Form 10-K for the period ended December 31, 1992, as
           filed with the Commission on March 28, 1993, and incorporated herein
           by reference. Addendum dated September 22, 1993, filed as Exhibit
           10.13 to the Annual Report on Form 10-K for the period ended December
           31, 1993, as filed with the Commission on February 14, 1994, and
           incorporated herein by reference. Addendum dated March 11, 1996, as
           filed with the Commission on March 24, 1997, and incorporated herein
           by reference. Addendum dated June 17, 1997, filed as Exhibit 10.13 to
           the Annual Report on Form 10-K for the period ended





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<PAGE>   43

           December 31, 1997, as filed with the Commission on March 30, 1998 and
           incorporated herein by reference.

10.15*     Form of Indemnification agreement between the Company and Directors
           and executive officers. Filed as Exhibit 10.15 to the Annual Report
           on Form 10-K for the period ended December 31, 1992, as filed with
           the Commission on March 28, 1993, and incorporated herein by
           reference.

10.16+     Stock Purchase Agreement dated as of March 21, 1995 between the
           Company and Boehringer Ingelheim International GmbH. Filed as Exhibit
           10.16 to the Annual Report on Form 10-K for the period ended December
           31, 1994, as filed with the Commission on March 31, 1995, and
           incorporated herein by reference.

10.17+     License Agreement dated as of March 21, 1995 between the Company and
           Boehringer Ingelheim International GmbH. Filed as Exhibit 10.17 to
           the Annual Report on Form 10-K for the period ended December 31,
           1994, as filed with the Commission on March 31, 1995, and
           incorporated herein by reference.

10.18+     Amendment to Stock Purchase Agreement and License Agreement between
           the Company and Boehringer Ingelheim International GmbH dated as of
           August 19, 1996. Filed as Exhibit 99.4 to Amendment No. 1 to the
           Current Report on Form 8-K/A dated August 19, 1996, as filed with the
           Commission on January 29, 1997, and incorporated herein by reference.

10.19+     Collaborative Research, Development and Marketing Agreement dated as
           of November 20, 1996 between the Company and Vision Pharmaceuticals
           L.P., d/b/a Allergan, Inc. Filed as Exhibit 99.1 to Amendment No. 1
           to the Current Report on Form 8-K/A dated August 19, 1996, as filed
           with the Commission on January 29, 1997, and incorporated herein by
           reference.

10.20+     Stock Purchase Agreement dated as of November 20, 1996 between the
           Company and Vision Pharmaceuticals L.P., d/b/a Allergan, Inc. Filed
           as Exhibit 99.2 to Amendment No. 1 to the Current Report on Form
           8-K/A dated August 19, 1996, as filed with the Commission on January
           29, 1997, and incorporated herein by reference.

10.21+     Credit Agreement dated as of November 20, 1996 between the Company
           and Vision Pharmaceuticals L.P., d/b/a Allergan, Inc. Filed as
           Exhibit 99.3 to Amendment No. 1 to the Current Report on Form 8-K/A
           dated August 19, 1996, as filed with the Commission on January 29,
           1997, and incorporated herein by reference.

10.22+     Sponsored Research and Collaborative Agreement dated as of December
           23, 1996 between Cambridge NeuroScience Partners, Inc. and The J.
           David Gladstone Institutes. Filed as Exhibit 99.1 to Amendment No. 1
           to the Current Report on Form 8-K/A dated December 23, 1996, as filed
           with the Commission on January 29, 1997, and incorporated herein by
           reference.

10.23+     Option Agreement dated as of December 23, 1996 by and among The
           Regents of the University of California, Cambridge NeuroScience
           Partners, Inc., and the Company. Filed as Exhibit 99.2 to Amendment
           No. 1 to the Current Report on Form 8-K/A dated December 23, 1996, as
           filed with the Commission on January 29, 1997, and incorporated
           herein by reference.

10.24+     Stockholders' Rights Agreement dated as of December 23, 1996 by and
           among the Company, Cambridge NeuroScience Partners, Inc., The J.
           David Gladstone Institutes and The Regents of the University of
           California. Filed as Exhibit 99.3 to Amendment No. 1 to the Current
           Report on Form 8-K/A dated December 23, 1996, as filed with the
           Commission on January 29, 1997, and incorporated herein by reference.





                                       42
<PAGE>   44

10.25*     Compensatory arrangement with certain executive officers and other
           members of management. Filed as Exhibit 10.25 to the Annual Report on
           Form 10-K for the period ended December 31, 1997, filed with the
           Commission on March 30, 1998 and incorporated herein by reference.

10.26      Termination agreement, dated November 4, 1998, between the Company
           and Boehringer Ingelheim International, GmbH. Filed as exhibit 10.28
           to the Quarterly Report on Form 10-Q for the quarter ended September
           30, 1998, as filed with the Commission on November 12, 1998, and
           incorporated herein by reference.

10.27+     Research Collaboration and License Agreement dated as of December 23,
           1998 between the Company and Bayer AG. Filed as Exhibit 10.27 to the
           Annual Report on Form 10-K for the period ended December 31, 1998,
           filed with the Commission on March 31, 1999, and incorporated herein
           by reference.

10.28      Amendment to Collaborative Research, Development and Marketing
           Agreement dated December 1, 1999 between the Company and Vision
           Pharmaceuticals L.P., d/b/a Allergan, Inc. Filed herewith.

21.1       Subsidiaries of the Company.  Filed herewith.

23.1       Consent of Ernst & Young LLP, independent auditors. Filed herewith.

24.1       Powers of Attorney. Contained on signature page hereto.

27.1       Financial Data Schedule for the year ended December 31, 1999. Filed
           herewith.

99.1       Important Factors Regarding Forward-Looking Statements. Filed
           herewith.


------------------------
      * Identifies a management contract or compensatory plan or agreement in
        which an executive officer or Director of the Company participates.
      + Confidential information contained in this Exhibit has been omitted and
        filed separately with the Securities and Exchange Commission.



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