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                                                                    EXHIBIT 99.1

                                  RISK FACTORS

         THIS QUARTERLY REPORT ON FORM 10-Q AND CERTAIN OTHER COMMUNICATIONS
MADE BY THE COMPANY CONTAIN "FORWARD-LOOKING STATEMENTS," INCLUDING MILLENNIUM'S
EXPECTATIONS OF FUTURE INDUSTRY CONDITIONS, STRATEGIC PLANS AND FORECASTS OF
OPERATIONAL RESULTS. VARIOUS RISKS MAY CAUSE MILLENNIUM'S ACTUAL RESULTS TO
DIFFER MATERIALLY. A LIST AND DESCRIPTION OF SOME OF THESE RISKS AND
UNCERTAINTIES FOLLOWS. MILLENNIUM DISCLAIMS ANY INTENTION OR OBLIGATION TO
UPDATE OR REVISE ANY FORWARD-LOOKING STATEMENTS, WHETHER AS A RESULT OF NEW
INFORMATION, FUTURE EVENTS OR OTHERWISE.

                                REGULATORY RISKS

WE HAVE NOT YET RECEIVED MARKETING APPROVAL FOR ANY PRODUCT OR SERVICE RESULTING
FROM OUR DEVELOPMENT EFFORTS AND MAY NOT BE ABLE TO OBTAIN ANY SUCH APPROVAL.

         We have completed development of only one product candidate,
CAMPATH-Registered Trademark- monoclonal antibody, which we developed in our
partnership with ILEX Oncology, Inc. This partnership only recently applied to
the U.S. Food and Drug Administration for approval to market this product. It is
possible that the FDA will not grant this marketing approval. As of September
30, 2000, we and our alliance partners were conducting clinical trials of six
product candidates resulting from our research and development programs,
including additional clinical trials of CAMPATH-Registered Trademark- monoclonal
antibody, and preclinical testing of approximately ten product candidates
resulting from these programs.

         All of the products that we are developing will require additional
research and development, extensive preclinical studies and clinical trials and
regulatory approval prior to any commercial sales. This process is lengthy,
often taking a number of years, and expensive. In some cases, the length of time
that it takes for us to achieve various regulatory approval milestones affects
the payments that we are eligible to receive under our strategic alliance
agreements.

         We may need to successfully address a number of technological
challenges in order to complete development of our products. Moreover, these
products may not be effective in treating any disease or may prove to have
undesirable or unintended side effects, toxicities or other characteristics that
may preclude our obtaining regulatory approval or prevent or limit commercial
use.

WE HAVE ONLY LIMITED EXPERIENCE IN REGULATORY AFFAIRS, AND SOME OF OUR PRODUCTS
MAY BE BASED ON NEW TECHNOLOGIES; THESE FACTORS MAY AFFECT OUR ABILITY OR THE
TIME WE REQUIRE TO OBTAIN NECESSARY REGULATORY APPROVALS.

         We have only limited experience in filing and prosecuting applications
necessary to gain regulatory approvals which may affect our ability to obtain
these approvals.



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Moreover, certain of the products that are likely to result from our research
and development programs may be based on new technologies and new therapeutic
approaches that have not been extensively tested in humans. The regulatory
requirements governing these types of products may be more rigorous than for
conventional products. As a result, we may experience a longer regulatory
process in connection with any products that we develop based on these new
technologies or new therapeutic approaches.

              RISKS RELATING TO OUR INDUSTRY, BUSINESS AND STRATEGY

BECAUSE DISCOVERING DRUGS BASED UPON GENOMICS IS NEW, IT IS POSSIBLE THAT THIS
DISCOVERY PROCESS WILL NOT RESULT IN COMMERCIAL PRODUCTS OR SERVICES.

         The process of discovering drugs based upon genomics is new and
evolving rapidly. We focus our genomics research primarily on diseases that may
be linked to several or many genes working in combination. Both we and the
general scientific and medical communities have only a limited understanding
relating to the role of genes and their products in these diseases. To date, we
have not commercialized any products or services, and we may not be successful
in doing so in the future. In addition, relatively few products based on gene
discoveries have been developed and commercialized by others. Rapid
technological development by us or others may result in compounds, products or
processes becoming obsolete before we recover our development expenses.

OUR PLAN TO GROW THROUGH ACQUISITIONS OF OTHER COMPANIES WILL NOT BE SUCCESSFUL
IF WE ARE UNABLE TO INTEGRATE ACQUIRED COMPANIES WITH OUR OTHER OPERATIONS OR IF
THE TECHNOLOGY OR PERSONNEL OF ACQUIRED COMPANIES DO NOT MEET OUR EXPECTATIONS.

         We completed our merger with LeukoSite, Inc. on December 22, 1999. In
addition, on July 27, 2000 we acquired the business of Cambridge Discovery
Chemistry Limited, a subsidiary of Oxford Molecular Group plc. We may not be
able to successfully integrate or profitably manage these businesses. In
addition, the combination of our business with these businesses may not achieve
revenues, net income or loss levels, efficiencies or synergies that justify the
merger. The combined company may experience slower rates of growth as compared
to the historical rates of growth of Millennium and these businesses
independently. We plan to make additional acquisitions in the future, which will
entail similar risks.

COMPETITION FOR SCIENTIFIC AND MANAGERIAL PERSONNEL IN OUR INDUSTRY IS INTENSE;
WE WILL NOT BE ABLE TO SUSTAIN OUR OPERATIONS AND GROW IF WE ARE NOT ABLE TO
ATTRACT AND RETAIN KEY PERSONNEL.

         Our success substantially depends on the ability, experience and
performance of our senior management and other key personnel. If we lose one or
more of the members of our senior management or other key employees, our
business and operating results could be seriously harmed.


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         In addition, our future success will depend heavily on our ability to
continue to hire, train, retain and motivate additional skilled managerial and
scientific personnel. The pool of personnel with the skills that we require is
limited. Competition to hire from this limited pool is intense.

WE FACE SUBSTANTIAL COMPETITION, WHICH MAY RESULT IN OTHERS DISCOVERING,
DEVELOPING OR COMMERCIALIZING PRODUCTS AND SERVICES BEFORE OR MORE SUCCESSFULLY
THAN WE DO.

         The fields of genomics, biotechnology and pharmaceuticals are highly
competitive. Many of our competitors are substantially larger than we are and
have substantially greater capital resources, research and development staffs
and facilities than we have. Furthermore, many of our competitors are more
experienced than we are in drug discovery, development and commercialization,
obtaining regulatory approvals and product manufacturing and marketing. As a
result, our competitors may identify genes associated with diseases or discover,
develop and commercialize products or services based on such genes before we do.
In addition, our competitors may discover, develop and commercialize products or
services which render non-competitive or obsolete the products or services that
we or our strategic alliance partners are seeking to develop and commercialize.

WE MAY NOT BE ABLE TO OBTAIN BIOLOGICAL MATERIAL, INCLUDING HUMAN AND ANIMAL DNA
SAMPLES, REQUIRED FOR OUR GENETIC STUDIES, WHICH COULD DELAY OR IMPEDE OUR DRUG
DISCOVERY EFFORTS.

         Our gene identification strategy includes genetic studies of families
and populations prone to particular diseases. These studies require the
collection of large numbers of DNA samples from affected individuals, their
families and other suitable populations as well as animal models. The
availability of DNA samples and other biological material is important to our
ability to discover the genes responsible for human diseases through human
genetic approaches and other studies. Competition for these resources is
intense. Access to suitable populations, materials and samples could be limited
by forces beyond our control, including governmental actions. Some of our
competitors may have obtained access to significantly more family and population
resources and biological materials than we have obtained. As a result, we may
not be able to obtain access to DNA samples necessary to support our human gene
discovery programs.

  RISKS RELATING TO OUR FINANCIAL RESULTS AND STRUCTURE AND NEED FOR FINANCING

WE HAVE INCURRED SUBSTANTIAL LOSSES AND EXPECT TO CONTINUE TO INCUR LOSSES. WE
WILL NOT BE SUCCESSFUL UNLESS WE REVERSE THIS TREND.

         We have incurred losses in four of the last six years and in the nine
months ended September 30, 2000. We expect to continue to incur substantial
operating losses in future periods. To date, substantially all of our revenues
have resulted from payments from



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strategic alliance partners. We have not received any revenues from the sale of
products or clinical or diagnostic services.

         We expect to increase our spending significantly as we continue to
expand our infrastructure, research and development programs and
commercialization activities. As a result, we will need to generate significant
revenues to pay these costs and achieve profitability. We cannot be certain
whether or when we will become profitable because of the significant
uncertainties with respect to our ability to generate revenues from the sale of
products and services and from existing and potential future strategic
alliances.

OUR SUBSTANTIAL INDEBTEDNESS MAY ADVERSELY AFFECT OUR CASH FLOW AND OPERATIONS
AND BE DIFFICULT FOR US TO REPAY, WHICH COULD ADVERSELY AFFECT THE VALUE OF YOUR
INVESTMENT IN US.

         We have substantial amounts of outstanding indebtedness, primarily
$124,907,000 of 5.50% convertible subordinated notes due January 15, 2007. We
also may obtain additional long-term debt and working capital lines of credit.
As a result of this indebtedness, we have substantial principal and interest
payment obligations. We may be unable to generate cash sufficient to pay the
principal of, interest on and other amounts due in respect of our indebtedness
when due.

         Our substantial leverage could have significant negative consequences,
including:

          -    increasing our vulnerability to general adverse economic and
               industry conditions;

          -    limiting our ability to obtain additional financing;

          -    requiring the dedication of a substantial portion of our cash
               from operations to service our indebtedness, thereby reducing the
               amount of our cash available for other purposes, including
               capital expenditures;

          -    limiting our flexibility in planning for, or reacting to, changes
               in our business and the industry in which we compete; and

          -    placing us at a possible competitive disadvantage vis-a-vis less
               leveraged competitors and competitors that have better access to
               capital resources.

WE MAY NEED ADDITIONAL FINANCING, WHICH MAY BE DIFFICULT TO OBTAIN. OUR FAILURE
TO OBTAIN NECESSARY FINANCING OR DOING SO ON UNATTRACTIVE TERMS COULD ADVERSELY
AFFECT OUR DISCOVERY AND DEVELOPMENT PROGRAMS AND OTHER OPERATIONS.

         We will require substantial funds to conduct research and development,
including preclinical testing and clinical trials of our potential products. We
will also require substantial funds to meet our obligations to our strategic
alliance partners and maximize the prospective benefits to us from these
alliances, manufacture and market any products



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and services that are approved for commercial sale and meet our debt service
obligations. Additional financing may not be available when we need it or may
not be available on terms that are favorable to us.

         If we are unable to obtain adequate funding on a timely basis, we may
be required to significantly curtail one or more of our discovery or development
programs. We could be required to seek funds through arrangements with
collaborative partners or others that may require us to relinquish rights to
certain of our technologies, product candidates or products which we would
otherwise pursue on our own.

                  RISKS RELATING TO STRATEGIC ALLIANCE PARTNERS

WE DEPEND SIGNIFICANTLY ON OUR STRATEGIC ALLIANCE PARTNERS TO DEVELOP AND
COMMERCIALIZE PRODUCTS AND SERVICES BASED ON OUR WORK. OUR BUSINESS MAY SUFFER
IF ANY OF OUR STRATEGIC ALLIANCE PARTNERS BREACHES ITS AGREEMENT OR FAILS TO
SUPPORT OR TERMINATES ITS ALLIANCE WITH US.

         We conduct most of our discovery and development activities through
strategic alliances. The success of these programs depends heavily on the
efforts and activities of our strategic alliance partners. Each of our alliance
partners has significant discretion in determining the efforts and resources
that they will apply to the alliance. Our existing and any future alliances may
not be scientifically or commercially successful.

         The risks that we face in connection with these alliances include:

          -    All of our strategic alliance agreements are subject to
               termination under various circumstances, including, in many
               cases, on short notice without cause.

          -    In our strategic alliance agreements, we generally agree not to
               conduct specified types of research and development in the field
               that is the subject of the alliance. These agreements may have
               the effect of limiting the areas of research and development we
               may pursue, either alone or in collaboration with third parties.

          -    Our alliance partners may develop and commercialize, either alone
               or with others, products and services that are similar to or
               competitive with the products and services that are the subject
               of the alliance with us.

          -    Our alliance partners may change the focus of their development
               and commercialization efforts. Pharmaceutical and biotechnology
               companies historically have re-evaluated their priorities
               following mergers and consolidations, which have been common in
               recent years in these industries.

          -    We will rely on our alliance partners to manufacture most
               products covered by our alliances. For example, Becton Dickinson
               has the sole right to develop,


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manufacture and commercialize our Melastatin-TM- gene detection product.
Therefore, we cannot control the timing of the introduction of this product.

WE MAY NOT BE SUCCESSFUL IN ESTABLISHING ADDITIONAL STRATEGIC ALLIANCES, WHICH
COULD ADVERSELY AFFECT OUR ABILITY TO DEVELOP AND COMMERCIALIZE PRODUCTS AND
SERVICES.

         An important element of our business strategy is entering into
strategic alliances for the development and commercialization of products and
services based on our discoveries. We face significant competition in seeking
appropriate alliance partners. Moreover, these alliance arrangements are complex
to negotiate and time-consuming to document. We may not be successful in our
efforts to establish additional strategic alliances or other alternative
arrangements. The terms of any additional strategic alliances or other
arrangements that we establish may not be favorable to us. Moreover, such
strategic alliances or other arrangements may not be successful.

                     RISKS RELATING TO INTELLECTUAL PROPERTY

IF WE ARE UNABLE TO OBTAIN PATENT PROTECTION FOR OUR DISCOVERIES, THE VALUE OF
OUR TECHNOLOGY AND PRODUCTS WILL BE ADVERSELY AFFECTED. IF WE INFRINGE PATENT OR
OTHER INTELLECTUAL PROPERTY RIGHTS OF THIRD PARTIES, WE MAY NOT BE ABLE TO
DEVELOP AND COMMERCIALIZE OUR PRODUCTS AND SERVICES OR THE COST OF DOING SO MAY
INCREASE.

         Our patent positions, and those of other pharmaceutical and
biotechnology companies, are generally uncertain and involve complex legal,
scientific and factual questions.

         Our ability to develop and commercialize products and services depends
in significant part on our ability to:

          -    obtain patents;

          -    obtain licenses to the proprietary rights of others on
               commercially reasonable terms;

          -    operate without infringing upon the proprietary rights of others;

          -    prevent others from infringing on our proprietary rights; and

          -    protect trade secrets.

THERE IS SIGNIFICANT UNCERTAINTY ABOUT THE VALIDITY AND PERMISSIBLE SCOPE OF
GENOMICS PATENTS IN OUR INDUSTRY, WHICH MAY MAKE IT DIFFICULT FOR US TO OBTAIN
PATENT PROTECTION FOR OUR DISCOVERIES.

         The validity and permissible scope of patent claims in the
pharmaceutical and biotechnology fields, including the genomics field, involve
important unresolved legal



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principles and are the subject of public policy debate in the United States and
abroad. For example, there is significant uncertainty both in the United States
and abroad regarding the patentability of gene sequences in the absence of
functional data and the scope of patent protection available for full-length
genes and partial gene sequences. Moreover, certain groups have made certain
gene sequences available in publicly accessible databases. These and other
disclosures may adversely affect our ability to obtain patent protection for
gene sequences claimed by us in patent applications that we file subsequent to
such disclosures. There is also some uncertainty as to whether human clinical
data will be required for issuance of patents for human therapeutics. If such
data are required, our ability to obtain patent protection could be delayed or
otherwise adversely affected.

THIRD PARTIES MAY OWN OR CONTROL PATENTS OR PATENT APPLICATIONS AND REQUIRE US
TO SEEK LICENSES, WHICH COULD INCREASE OUR DEVELOPMENT AND COMMERCIALIZATION
COSTS, OR PREVENT US FROM DEVELOPING OR MARKETING OUR PRODUCTS OR SERVICES.

         We may not have rights under some patents or patent applications
related to our proposed products, processes or services. Third parties may own
or control these patents and patent applications in the United States and
abroad. Therefore, in some cases, such as those described below, to develop,
manufacture, sell or import certain of our proposed products, processes or
services, we or our alliance partners may choose to seek, or be required to
seek, licenses under third party patents issued in the United States and abroad
or those that might issue from United States and foreign patent applications. In
such event, we would be required to pay license fees or royalties or both to the
licensor. If licenses are not available to us on acceptable terms, we or our
alliance partners may not be able to develop, manufacture, sell or import these
products, processes or services.

         With respect to our product candidate LDP-01, we are aware of third
party patents and patent applications which relate to certain anti-CD18
antibodies and their use in various methods of treatment including methods of
reperfusion therapy and methods of treating focal ischemic stroke. In addition,
our LDP-01, LDP-02, and CAMPATH-Registered Trademark- product candidates are
humanized monoclonal antibodies. We are aware of third party patents and patent
applications which relate to certain humanized or modified antibodies, products
useful for making humanized or modified antibodies, and processes for making and
using humanized or modified antibodies. We are also aware of third party patents
and patent applications relating to certain manufacturing processes, products
thereof and materials useful in such processes.

         Our product candidates LDP-341 and LDP-519 are small molecule drug
candidates. With respect to LDP-341, we are aware of third party patents or
patent applications which relate to either intermediates or synthetic processes
used in the synthesis of this compound. Additionally, for the use of LDP-341 and
LDP-519 in the treatment of infarctions we are aware of the existence of a
potentially interfering patent application filed by one of our former
consultants.

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WE MAY BECOME INVOLVED IN EXPENSIVE PATENT LITIGATION OR OTHER PROCEEDINGS,
WHICH COULD RESULT IN OUR INCURRING SUBSTANTIAL COSTS AND EXPENSES OR
SUBSTANTIAL LIABILITY FOR DAMAGES OR REQUIRE US TO STOP OUR DEVELOPMENT AND
COMMERCIALIZATION EFFORTS.

         There has been substantial litigation and other proceedings regarding
the patent and other intellectual property rights in the pharmaceutical and
biotechnology industries. We may become a party to patent litigation or other
proceedings regarding intellectual property rights. For example, we believe that
we hold patent applications that cover genes that are also claimed in patent
applications filed by others. Interference proceedings before the United States
Patent and Trademark Office may be necessary to establish which party was the
first to invent these genes.

         The cost to us of any patent litigation or other proceeding, even if
resolved in our favor, could be substantial. Some of our competitors may be able
to sustain the cost of such litigation or proceedings more effectively than we
can because of their substantially greater financial resources. If a patent
litigation or other proceeding is resolved against us, we or our alliance
partners may be enjoined from developing, manufacturing, selling or importing
our products, processes or services without a license from the other party and
we may be held liable for significant damages. We may not be able to obtain any
required license on commercially acceptable terms or at all.

         Uncertainties resulting from the initiation and continuation of patent
litigation or other proceedings could have a material adverse effect on our
ability to compete in the marketplace. Patent litigation and other proceedings
may also absorb significant management time.

          RISKS RELATING TO PRODUCT MANUFACTURING, MARKETING AND SALES

BECAUSE MANY OF THE PRODUCTS AND SERVICES THAT WE DEVELOP WILL BE BASED ON NEW
TECHNOLOGIES AND THERAPEUTIC APPROACHES, THE MARKET MAY NOT BE RECEPTIVE TO
THESE PRODUCTS AND SERVICES UPON THEIR INTRODUCTION.

         The commercial success of our products and services that are approved
for marketing will depend upon their acceptance by the medical community and
third party payors as clinically useful, cost effective and safe. Many of the
products and services that we are developing are based upon new technologies or
therapeutic approaches. As a result, it may be more difficult for us to achieve
market acceptance of our products and services, particularly the first products
and services that we introduce to the market based on new technologies and
therapeutic approaches.

BECAUSE WE HAVE NO SALES, MARKETING OR DISTRIBUTION EXPERIENCE AND CAPABILITIES,
WE WILL DEPEND ON THIRD PARTIES TO SUCCESSFULLY PERFORM THESE FUNCTIONS ON OUR
BEHALF OR WILL BE REQUIRED TO INCUR SIGNIFICANT COSTS AND DEVOTE SIGNIFICANT
EFFORTS TO DEVELOP THESE CAPABILITIES.

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         We have no sales, marketing or distribution experience and
capabilities. We plan to rely significantly on sales, marketing and distribution
arrangements with our strategic alliance partners and other third parties for
the products and services that we are developing. For example, our partnership
that holds CAMPATH-Registered Trademark- monoclonal antibody will rely solely
upon Schering AG and its U.S. affiliate, Berlex Laboratories, for the marketing,
distribution and sale of the CAMPATH-Registered Trademark- product throughout
the world other than the Far East. If in the future we elect to perform sales,
marketing and distribution functions ourselves, we would face a number of
additional risks, including the need to recruit experienced marketing and sales
personnel.

BECAUSE WE HAVE LIMITED MANUFACTURING CAPABILITIES, WE WILL BE DEPENDENT ON
THIRD-PARTY MANUFACTURERS TO MANUFACTURE PRODUCTS FOR US OR WILL BE REQUIRED TO
INCUR SIGNIFICANT COSTS AND DEVOTE SIGNIFICANT EFFORTS TO ESTABLISH OUR OWN
MANUFACTURING FACILITIES AND CAPABILITIES.

         We have limited manufacturing experience and no commercial scale
manufacturing capabilities. In order to continue to develop products and
services, apply for regulatory approvals and, ultimately, commercialize any
products and services, we will need to develop, contract for or otherwise
arrange for the necessary manufacturing capabilities.

         We currently rely upon third parties to produce material for
preclinical testing purposes and expect to continue to do so in the future. We
also expect to rely upon other third parties, including our strategic alliance
partners, to produce materials required for clinical trials and for the
commercial production of certain of our products if we succeed in obtaining
necessary regulatory approvals. Our partnership with ILEX Oncology relies on
Boehringer Ingelheim as the sole source manufacturer of CAMPATH-Registered
Trademark- monoclonal antibody.

         There are a limited number of manufacturers that operate under the
FDA's good manufacturing practices regulations capable of manufacturing for us.
As a result, we have experienced some difficulty finding manufacturers for our
products with adequate capacity for our anticipated future needs. If we are
unable to arrange for third party manufacturing of our products, or to do so on
commercially reasonable terms, we may not be able to complete development of our
products or market them.

         Reliance on third party manufacturers entails risks to which we would
not be subject if we manufactured products ourselves, including reliance on the
third party for regulatory compliance and quality assurance, the possibility of
breach of the manufacturing agreement by the third party because of factors
beyond our control and the possibility of termination or nonrenewal of the
agreement by the third party, based on its own business priorities, at a time
that is costly or inconvenient for us.

         We may in the future elect to manufacture certain of our products in
our own manufacturing facilities. We will require substantial additional funds
and need to recruit qualified personnel in order to build or lease and operate
any manufacturing facilities.

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IF WE FAIL TO OBTAIN AN ADEQUATE LEVEL OF REIMBURSEMENT FOR OUR FUTURE PRODUCTS
OR SERVICES BY THIRD PARTY PAYORS, THERE MAY BE NO COMMERCIALLY VIABLE MARKETS
FOR OUR PRODUCTS OR SERVICES.

         The availability and levels of reimbursement by governmental and other
third party payors affect the market for any pharmaceutical product or
healthcare service. These third party payors continually attempt to contain or
reduce the costs of healthcare by challenging the prices charged for medical
products and services. In certain foreign countries, particularly the countries
of the European Union, the pricing of prescription pharmaceuticals is subject to
governmental control. We may not be able to sell our products and services
profitably if reimbursement is unavailable or limited in scope or amount.

         In both the United States and certain foreign jurisdictions, there have
been a number of legislative and regulatory proposals to change the healthcare
system. Further proposals are likely. The potential for adoption of these
proposals affects or will affect our ability to raise capital, obtain additional
collaborative partners and market our products.

         If we or our alliance partners obtain marketing approvals for our
products and services, we expect to experience pricing pressure due to the trend
toward managed health care, the increasing influence of health maintenance
organizations and additional legislative proposals.

ETHICAL, LEGAL AND SOCIAL ISSUES RELATED TO GENETIC TESTING MAY CAUSE OUR
DIAGNOSTIC PRODUCTS TO BE REJECTED BY CUSTOMERS OR PROHIBITED OR CURTAILED BY
GOVERNMENTAL AUTHORITIES.

         Diagnostic tests that evaluate genetic predisposition to disease raise
issues regarding the use and confidentiality of the information provided by such
tests. Insurance carriers and employers might discriminate on the basis of such
information, resulting in a significant barrier to the acceptance of such tests
by customers. This type of discrimination could cause governmental authorities
to prohibit or limit the use of such tests.