As filed with the Securities and Exchange Commission on October 15, 1998

Registration No. 333-
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SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

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FORM S-3

REGISTRATION STATEMENT UNDER
THE SECURITIES ACT OF 1933

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LEUKOSITE, INC.

(Exact name of registrant as specified in its charter)

DELAWARE 2834 04-3173859
(State or other jurisdiction of (Primary Standard Industrial (I.R.S. Employer
incorporation or organization) Classification Code Numbers) identification No.)

215 First Street
Cambridge, MA 02142
(617) 621-9350

(Address, including zip code, and telephone number, including area code, of
registrant's principal executive offices)

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Christopher K. Mirabelli, Ph.D.
Chairman of the Board of Directors
LEUKOSITE, INC.
215 First Street
Cambridge, MA 02142
(617) 621-9350

(Name, address, including zip code, and telephone number, including area code,
of agent for service)

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with copies to:
Justin P. Morreale, Esq.
Julio E. Vega, Esq.
Bingham Dana LLP
150 Federal Street
Boston, MA 02110
(617) 951-8000

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Approximate date of commencement of proposed sale to the public:
From time to time after this Registration Statement becomes effective

If the only securities being registered on this form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. / /

If any of the securities being registered on this form are to be
offered on a delayed or continuous basis pursuant to Rule 415 under the
Securities Act of 1933, check the following box. /X/

If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. / /

If this Form is a post-effective amendment filed pursuant to Rule
462(c) under the Securities Act, check the following box and list the Securities
Act registration statement number of the earlier effective registration
statement for the same offering. / /

If delivery of the prospectus is expected to be made pursuant to Rule
434, please check the following box. / /

CALCULATION OF REGISTRATION FEE

Proposed Maximum Proposed Maximum
Title of Securities Amount to Offering Price Aggregate Amount of
to be Registered be Registered Per Share(1) Offering Price(1) Registration Fee
---------------- ------------- ------------ ----------------- ----------------

Common Stock
Par Value $.01 per share 7,071,810 $7.13 $50,422,005 $14,874.49
--------------------------- ------------------ ------------------- --------------------- --------------------

(1) Estimated solely for the purpose of determining the registration
fee. Calculated in accordance with Rule 457(c), based on the offering of up to
7,071,810 shares at a purchase price of $7.13 per share, which is the average of
the high and low sale prices reported in the consolidated reporting system of
the Nasdaq National Market on October 12, 1998. It is not known how many shares
will be purchased under this Registration Statement or at what price such shares
will be purchased.

The Registrant hereby amends this Registration Statement on such date
or dates as may be necessary to delay its effective date until the Registrant
shall file a further amendment which specifically states that this Registration
Statement shall thereafter become effective in accordance with Section 8(a) of
the Securities Act of 1933 or until the Registration Statement shall become
effective on such date as the Commission, acting pursuant to Section 8(a), may
determine.

PROSPECTUS
- ----------

THE INFORMATION CONTAINED IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE
CHANGED. THESE SECURITIES MAY NOT BE SOLD UNTIL THE REGISTRATION STATEMENT FILED
WITH THE SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT
AN OFFER TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE
SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.

Subject to Completion, dated October 15, 1998

7,071,810 Shares

LEUKOSITE, INC.

Common Stock

Selling stockholders identified in this prospectus are selling
7,071,810 shares of common stock of LeukoSite, Inc. LeukoSite will not receive
any of the proceeds from the sale of shares by the selling stockholders.
LeukoSite's common stock is listed on the Nasdaq National Market under the
symbol "LKST". On October 13, 1998, the closing sale price of the common stock,
as reported on the Nasdaq National Market, was $7.13 per share.

Investing in the common stock involves a high degree of risk.
See "Risk Factors," beginning on page 3.

The LeukoSite shares offered or sold under this prospectus have not
been approved by the SEC or any state securities commission, nor have these
organizations determined that this prospectus is accurate or complete. Any
representation to the contrary is a criminal offense.

The selling stockholders may sell the shares of common stock described
in this prospectus in public or private transactions, on or off the National
Market System of the Nasdaq Stock Market, at prevailing market prices, or at
privately negotiated prices. The selling stockholders may sell shares directly
to purchasers or through brokers or dealers. Brokers or dealers may receive
compensation in the form of discounts, concessions or commissions from the
selling stockholders. More information is provided in the section titled "Plan
of Distribution."

The date of this prospectus is __________, 1998.

WHERE YOU CAN GET MORE INFORMATION

We are a reporting company and file annual, quarterly and current
reports, proxy statements and other information with the SEC. You may read and
copy these reports, proxy statements and other information at the SEC's public
reference rooms in Washington, DC, New York, NY and Chicago, IL. You can request
copies of these documents by writing to the SEC and paying a fee for the copying
cost. Please call the SEC at 1-800-SEC-0330 for more information about the
operation of the public reference rooms. Our SEC filings are also available at
the SEC's Web site at "http://www.sec.gov". In addition, you can read and copy
our SEC filings at the office of the National Association of Securities Dealers,
Inc. at 1735 K Street, Washington, DC 20006.

The SEC allows us to "incorporate by reference" information that we
file with them, which means that we can disclose important information to you by
referring you to those documents. The information incorporated by reference is
an important part of this prospectus, and information that we file later with
the SEC will automatically update and supersede this information. We incorporate
by reference the documents listed below and any future filings we will make with
the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act
of 1934:

- Annual Report on Form 10-K for the year ended December 31, 1997;

- Quarterly Reports on Form 10-Q for the quarters ended March 31,
1998 and June 30, 1998;

- Current Report on Form 8-K filed January 26, 1998; and

- The description of the common stock contained in LeukoSite's
Registration Statement on

Form 8-A filed with the SEC under the Securities Exchange Act of
1934.

You may request a copy of these filings at no cost, by writing,
telephoning or e-mailing us at the following address:

LeukoSite, Inc.
215 First Street
Cambridge, MA 02142
Attn: Investor Relations
(617) 621-9350
information@LeukoSite.com

This prospectus is part of a smaller Registration Statement we filed
with the SEC. You should rely only on the information incorporated by reference
or provided in this prospectus. We have not authorized anyone else to provide
you with different information. We are not making an offer of these securities
in any state where the offer is not permitted. You should not assume that the
information in this prospectus is accurate as of any date other than the date on
the front of the document.

FORWARD-LOOKING STATEMENTS

This prospectus contains forward-looking statements within the meaning
of Section 27A of the Securities Act of 1933 and Section 21E of the Securities
Exchange Act of 1934, including statements regarding LeukoSite's drug
development programs, clinical trials, receipt of regulatory approval, capital
needs, intellectual property, expectations and intentions. Forward-looking
statements necessarily involve risks and uncertainties, and LeukoSite's actual
results could differ materially from those anticipated in the forward-looking
statements, including those set forth below under "Risk Factors" and elsewhere
in this prospectus. The factors set forth below under "Risk Factors" and other
cautionary statements made in this prospectus should be read and understood as
being applicable to all related forward-looking statements wherever they appear
in this prospectus.

RISK FACTORS

Investing in LeukoSite's common stock is very risky. You should be able
to bear a complete loss of your investment. You should carefully consider the
following factors, in addition to the other information in this prospectus.

Uncertainty of Clinical Trial Outcomes. Clinical trials of drug
candidates involve the testing of potential therapeutic agents in humans to
determine the safety and efficacy of drug candidates. Many drugs in human
clinical trials fail to demonstrate desired safety and efficacy characteristics.
Drugs in later stages of development may fail despite having progressed through
initial human testing.

Early Stage Product Development Programs. Many of our research and
development programs are at an early stage. We have not completed clinical
development of any of our monoclonal antibody products or selected any small
molecule drug candidates. Any drug candidates that we develop will require
significant additional research and development efforts, extensive preclinical
(animal and laboratory) and clinical testing, as well as regulatory approval,
before we can begin testing in humans. In addition, encouraging results obtained
in laboratory testing alone do not necessarily mean that similar results will be
obtained in later stages of preclinical development or in human clinical
testing. Potential drug candidates are subject to inherent risks of failure.
These risks include the possibilities that no drug candidate will be found safe
or effective, meet applicable regulatory standards, or receive the necessary
regulatory clearances.

We cannot assure you that safe and effective drug candidates will be
developed into commercially successful drugs. There may be delays in receipt of
regulatory approvals. The drugs could be uneconomical to manufacture or produce
on a large scale. We could be unable to successfully market the new drugs or
achieve customer acceptance. The proprietary rights of others could stop us from
being able to market the drugs, or third parties could market superior or
equivalent drugs. If we were unable to develop safe, commercially viable drugs,
it would have a material adverse effect on our business, financial condition and
results of operations.

Dependence on Collaborative Partners. A key element of our strategy is
to accelerate drug discovery and development programs and to fund capital
requirements, in part, by entering into collaboration agreements with major
pharmaceutical companies. We have entered into collaboration agreements with
Warner-Lambert, Roche Bioscience, Kyowa Hakko Kogyo and Genentech. Under our
collaboration agreements with Warner-Lambert, Roche Bioscience and Kyowa, our
collaborative partners have the right, but not the obligation, to conduct
preclinical and clinical trials of compounds developed during our collaboration
and to develop and commercialize any drug candidates. Under the Genentech
collaboration agreement, Genentech has the right, but not the obligation, to
conduct Phase III clinical trials of LDP-02. Our receipt of revenues from
milestones, royalties, co-promotion rights or profit-sharing under the
collaboration agreements is dependent upon the activities and the development,
manufacturing and marketing resources of our collaborative partners. Our
collaborative partners have significant discretion in electing whether to pursue
the development of any potential drug candidates. As a result, we cannot control
the amount and timing of resources dedicated by our collaborative partners to
our collaborations.

We cannot assure you that our collaborative partners will pursue the
development and commercialization of compounds resulting from our collaboration
or that we will successfully derive any revenue from the sales of drugs. Certain
drug candidates discovered by us may be competitive with our collaborative
partners' drugs or drug candidates. Accordingly, we cannot assure you that our
collaborative partners will proceed with the development of

our drug candidates or that they will not pursue their existing or alternative
technologies in preference to our drug candidates. Disagreements between us and
our collaborative partners could lead to delays in research or in the
development and commercialization of certain drug candidates or in litigation.
Any of these factors could have a material adverse effect on our business,
financial condition and results of operations.

We are relying on our collaborative partners to fund a significant
portion of our research operations and clinical trials over the next several
years. Although each of the collaboration agreements may be extended past its
current term, we cannot assure you that these contracts will be extended or
renewed. Each of the collaboration agreements is terminable by either party upon
breach by the other party. Moreover, Warner-Lambert may terminate the
collaboration agreements upon six months written notice. Kyowa may terminate its
collaboration agreement with 60 days notice. Genentech may terminate its
collaboration agreement after December 1998, upon nine months notice. We cannot
assure you that any of the collaboration agreements will remain in effect for
its expected term. The delay or termination of a collaboration agreement could
force us to undertake unforeseen additional responsibilities or to devote
unbudgeted additional resources to development or commercialization of a drug
candidate. Those events and could have a material adverse effect on our
business, financial condition and results of operations.

History of Losses and Expectation of Future Losses; Uncertainty of
Future Profitability. LeukoSite was incorporated in May 1992 and has incurred a
net operating loss every year. Our accumulated deficit was approximately $ 39.6
million through June 30, 1998. We expect to incur significant additional
operating losses over the next several years due to expanded research and
development efforts, preclinical and clinical trials and the funding of
development activities under the joint venture with Ilex Oncology, Inc.

In the next few years, we expect our revenues to be limited to any
research support and milestone payments under the current collaboration
agreements and any future collaboration agreements that we may establish. We
cannot assure you that we will achieve the milestones that are required to
receive additional funds from our current collaborative partners or that we will
be able to maintain the collaboration agreements in effect. In addition, we can
not assure you that we will be able to establish any additional collaborative
relationships on acceptable terms, if at all. We cannot assure you that
LeukoSite will operate profitably.

Substantial Additional Financing Requirements; Uncertainty of Available
Funding. We will require substantial additional funds in order to finance our
drug discovery and development programs, fund operating expenses, pursue
regulatory clearances, develop manufacturing, marketing and sales capabilities,
and prosecute and defend our intellectual property rights. We depend upon our
collaborative partners for research and clinical trials funding. We cannot give
any assurance that funding will continue under our existing collaboration
agreements, or that existing and potential collaboration agreements will be
sufficient to fund our operating expenses.

We intend to seek additional funding through public or private
financing or through collaboration arrangements with collaborative partners. If
we raise funds by selling equity securities, sales may dilute your share
ownership and future investors may be granted rights superior to yours. We
cannot give any assurance, however, that additional financing will be available
on acceptable terms, if at all.

Impact of Extensive Government Regulation. The LeukoSite products under
development are subject to regulation by the federal government, including the
Food and Drug Administration, and by state and local governments. If our
products are marketed abroad, they will also be subject to export requirements
and to regulation by foreign governments. The applicable regulatory approval
process is lengthy and expensive and must be completed prior to the
commercialization of a product. We cannot give any assurance that we will be
able to obtain necessary regulatory approvals on a timely basis, if at all, for
any of our products under development. Delays in receipt or failure to receive
such approvals or failure to comply with existing or future regulatory
requirements could have a material adverse effect on our business, financial
condition and results of operations.

Product development and approval to meet FDA regulatory requirements
takes a number of years, involves the expenditure of substantial resources and
is uncertain. Many products that initially appear promising ultimately do not
reach the market because they are not found to be safe or effective. In
addition, the current regulatory framework could change and additional
regulations may arise at any stage of product development that may affect
approval, delay the submission or review of an application or require additional
expenditures.

We cannot be certain if and when we or our collaborative partners will
submit any marketing applications for any of our product candidates for any
indications. We cannot provide any assurance that any clinical studies will be
completed or, if completed, will demonstrate that the products are safe and
effective. We cannot provide any assurance that required approvals will be
granted by FDA on a timely basis, or at all, for any of these products for any
indications.

All of our product candidates will require FDA and foreign government
approvals for commercialization. As yet, no approvals have been obtained. We
have completed enrollment in our licensing trial of CAMPATH (LDP-03) but have
not completed analysis of the results of the trial. We cannot be certain as to
the clinical efficacy and safety characteristics of CAMPATH at this time. We
have commenced trials of our LDP-01 and LDP-02 product candidates in abroad and
intend to continue to perform preclinical and clinical trials abroad, subject to
receipt of required United Kingdom regulatory approvals. FDA may require us to
repeat certain or all U.K. clinical trials in the United States, which would
increase the time and expense required to obtain FDA approval.

The effect of government regulation may be to delay marketing of our
products for a considerable or indefinite time, impose costly procedural
requirements and furnish a competitive advantage to larger companies or
companies more experienced in regulatory affairs. Delays in obtaining
governmental regulatory approval could adversely affect our marketing strategy
as well as our ability to generate revenue from product sales. The failure to
obtain marketing approval of our products on a timely basis, or at all, would
have a material adverse effect on our business, financial condition and results
of operations.

Uncertainties Relating to Patents and Proprietary Rights. Our success
will depend in part on our ability to obtain United States and foreign patent
protection for our drug candidates and processes, preserve our trade secrets,
and operate without infringing the proprietary rights of third parties. We place
considerable importance on obtaining patent protection for significant new
technologies, products and processes. Legal standards relating to the validity
of patents covering pharmaceutical and biotechnological inventions and the scope
of claims made under such patents are still developing. Our patent position is
highly uncertain and involves complex legal and factual questions. We cannot be
certain that the applicants or inventors of subject matter covered by patent
applications or patents owned by or licensed to us were the first to invent or
the first to file patent applications for such inventions. We cannot give any
assurance that any patents will issue from any of the pending or future patent
applications we own or have licensed. Existing or future patents owned by or
licensed to us may be challenged, infringed upon, invalidated, found to be
unenforceable or circumvented by others. Further, we cannot give any assurance
that any rights we may have under any issued patents will provide us with
sufficient protection against competitive products or otherwise cover
commercially valuable products or processes.

If another party claims the same subject matter or subject matter
overlapping with subject matter that we have claimed in a United States patent
application or patent, we may decide or be required to participate in
interference proceedings in the United States Patent and Trademark Office in
order to determine priority of invention. Loss of such an interference
proceeding would deprive us of patent protection sought or previously obtained.
Participation in such proceedings could result in substantial costs, whether or
not the eventual outcome is favorable.

In addition to patent protection, we rely on trade secrets, proprietary
know-how, and confidentiality provisions in agreements with our collaborative
partners, employees and consultants to protect our intellectual property. We
also rely on invention assignment provisions in agreements with employees and
certain consultants. We cannot give any assurance that these agreements will not
be breached or that we would have adequate remedies for any such breach. We
cannot give any assurance that our trade secrets, proprietary know-how and
intellectual property will not become known or be independently discovered by
others.

Our product candidates LDP-01, LDP-02 and LDP-03 are humanized
monoclonal antibodies. We are aware that patents have been issued in the United
States and abroad to third parties that relate to certain humanized antibodies,
products useful for making humanized antibodies, and processes for making and
using humanized antibodies. We may choose to seek or be required to seek
licenses under certain of these patents.

We are also aware of other third party applications in the United
States and abroad relating to certain humanized monoclonal antibodies, products
useful for making humanized antibodies, and processes for making and using
humanized antibodies. We may choose to seek or be required to seek licenses
under some or all of the patents which might issue from these patent
applications.

Litigation in the pharmaceutical and biotechnology industry regarding
patents and other proprietary rights has been significant and widespread.
Litigation or other proceedings may be necessary to assert claims of
infringement, to enforce patents owned by or licensed to us, to protect trade
secrets, know-how or other intellectual property rights owned by or licensed to
us, or to determine the scope or validity of proprietary rights of third parties
and defend against claims of infringement thereof. There can be no assurance
that any of the patents owned by or licensed to us will ultimately be held valid
or that efforts to assert or defend any patents, trade secrets, know-how or
other intellectual property rights would be successful. Similarly, there can be
no assurance that the products or processes we use will not be held to infringe
patents or other intellectual property rights of others. The expenses of
intellectual property litigation or other proceedings are likely to be
substantial, and could have a material adverse effect on our business, operating
results and financial condition. An adverse outcome in such litigation or
proceeding could subject us to significant liabilities or require us to cease
certain activities. If any of our present or future products or processes is
alleged or determined to infringe upon the patents or impermissibly use the
intellectual property of others, we may choose or be required to obtain licenses
from third parties under their patents or proprietary rights. We cannot give any
assurance that we will be able to obtain those licenses on acceptable terms, or
at all. In such event, the development, manufacture and sale of our drug
candidates or products could be severely restricted or prohibited.

Intense Competition. The biotechnology and pharmaceutical industries
are intensely competitive. We have numerous competitors in the United States and
elsewhere. Our competitors include major, multinational pharmaceutical and
chemical companies, specialized biotechnology firms and universities and other
research institutions. Many of these competitors have greater financial and
other resources, larger research and development staffs and more effective
marketing and manufacturing organizations, than we do. In addition, academic and
government institutions have become increasingly aware of the commercial value
of their research findings. These institutions are now more likely to enter into
exclusive licensing agreements with commercial enterprises, including our
competitors, to market commercial products.

We cannot give any assurance that our competitors will not succeed in
developing or licensing technologies and drugs that are more effective or less
costly than any we are developing. Our competitors may succeed in obtaining FDA
or other regulatory approvals for drug candidates before we do. We cannot give
any assurance that drugs resulting from our research and development efforts, if
approved for sale, will be able to compete successfully with our competitors'
existing products or products under development.

Rapid Technological Change. Biotechnology and related pharmaceutical
technology have undergone and are subject to rapid and significant change. We
expect that the technologies associated with biotechnology research and
development will continue to develop rapidly. Our future will depend in large
part on our ability to maintain a competitive position with respect to these
technologies. Any compounds, products or processes that we develop may become
obsolete before we recover any expenses incurred in connection with developing
those products.

Reliance on Contract Manufacturers; Lack of Manufacturing Experience.
We are dependent on other people for the manufacture of our product candidates.
We are aware of only a limited number of manufacturers who we believe have the
ability and capacity to manufacture our drug candidates for preclinical and
clinical trials. We have entered into an agreement with Karl Thomae, a contract
manufacturer, for the production of CAMPATH (LDP-03) for clinical trials. We
have been relying on the Therapeutic Antibody Centre for the manufacture of
LDP-01 and LDP-02 for preclinical testing. We intend to employ the manufacturing
capability of the TAC through other early clinical trials. If we were required
to transfer manufacturing processes to other manufacturers, we could experience
significant delays in supply. If, at any time, we were unable to maintain,
develop or contract for manufacturing capabilities on acceptable terms, our
ability to conduct preclinical and clinical trials will be adversely affected
and there would be delays in the submission of drug candidates for regulatory
approvals.

Our collaborative partners generally have the exclusive right to
manufacture products resulting from our collaborations. We have no experience in
manufacturing and currently lack the facilities and personnel to

manufacture products in accordance with Good Manufacturing Practices as
prescribed by the FDA or to produce an adequate supply of compounds to meet
future requirements.

Risks Associated with Ilex Joint Venture. We have entered into a joint
venture with Ilex for the development and commercialization of CAMPATH (LDP-03)
for the treatment of chronic lymphocytic leukemia. As part of the joint venture,
we are obligated to share fifty percent of the development costs of CAMPATH
(LDP-03). We cannot give any assurance that we will have the cash available or
will desire to maintain our commitment to the joint venture. In the event that
we fail for any reason to make a required capital contribution to the joint
venture, Ilex may gain control of the management of the joint venture and become
entitled to a greater share of the profits derived from product sales of LDP-03.

We can also give no assurance that Ilex will have the cash available or
will desire to maintain its commitment to the joint venture. In the event that
Ilex fails for any reason to make a required capital contribution to the joint
venture, we may be required to make additional capital contributions to the
joint venture to maintain the desired level of development activities by the
joint venture. We can give no assurance that we will be able to compensate for
any failure by Ilex to make any capital contribution or that the joint venture
would be able to continue operations with lesser funding. In addition, after the
earlier of a change in control of Ilex or LeukoSite or October 2, 2000, either
company has the right to purchase the other company's ownership of the joint
venture in the event of an unresolved deadlock. As a result, we can give no
assurance that we will be able to recoup our investment in the joint venture.

Dependence on Key Personnel. We believe that our ability to
successfully implement our business strategy is highly dependent on our
management and scientific team. None of our executive officers has entered into
an employment agreement. The loss of services of one or more of these
individuals might hinder the achievement of our development objectives. We are
highly dependent on our ability to hire and retain qualified scientific and
technical personnel. The competition for these employees is intense. We cannot
give any assurance that we will continue to be able to hire and retain the
qualified personnel needed for our business. Loss of the services of or the
failure to recruit key scientific and technical personnel could adversely affect
our business, operating results and financial condition.

Control by Existing Stockholders. LeukoSite's officers, directors and
principal stockholders own or control approximately 47.25% of the outstanding
common stock. As a result, these stockholders, acting together, will have the
ability to control most matters requiring approval by the stockholders.

Absence of Dividends. We have never declared or paid cash dividends. We
do not intend to declare or pay any cash dividends in the foreseeable future.

Year 2000 Issues. We are evaluating Year 2000 issues and their
potential impact on our information systems and computer technologies. All
evaluation costs will be expensed as incurred. Year 2000 issues are not expected
to have a significant impact on our ongoing results of operations.

THE COMPANY

LeukoSite is a biotechnology company developing proprietary drugs
designed to block the disease-promoting action of white blood cells. The focus
of LeukoSite's research and development is on drugs for the treatment of cancer,
autoimmune and inflammatory diseases. The mailing address and telephone number
of our principal executive office is 215 First Street, Cambridge, MA 02142 (617)
631-9350.

RECENT DEVELOPMENTS

On July 1, 1998, LeukoSite raised approximately $11.8 million in a
private placement of common stock. LeukoSite issued approximately 1,970,000
shares of common stock.

USE OF PROCEEDS

LeukoSite will not receive any proceeds from the sale of the shares of
common stock offered by the selling stockholders.

SELLING STOCKHOLDERS

Under a Registration Rights Agreement dated July 1, 1998 among
LeukoSite and certain selling stockholders, we agreed to register the LeukoSite
common stock sold to those selling stockholders in the private placement and to
use our best efforts to keep the Registration Statement effective for two years,
or until all of the shares are sold under the Registration Statement, whichever
comes first. Our registration of the shares of common stock does not necessarily
mean that the selling shareholders will sell all or any of the shares.

The following table sets forth certain information regarding the
beneficial ownership of the common stock as of September 30, 1998, by each of
the selling stockholders.

The information provided in the table below with respect to each
selling stockholder has been obtained from such selling stockholder. Except as
otherwise disclosed below, none of the selling stockholders has, or within the
past three years has had, any position, office or other material relationship
with the Company. Because the selling stockholders may sell all or some portion
of the shares of common stock beneficially owned by them, only an estimate
(assuming each selling stockholder sells all of their shares offered hereby) can
be given as to the number of shares of common stock that will be beneficially
owned by the selling stockholders after this offering. In addition, the selling
stockholders may have sold, transferred or otherwise disposed of, or may sell,
transfer or otherwise dispose of, at any time or from time to time since the
date on which they provided the information regarding the shares of common stock
beneficially owned by them, all or a portion of the shares of common stock
beneficially owned by them in transactions exempt from the registration
requirements of the Securities Act of 1933.

Shares
Beneficially Number
Owned Of Shares Shares
Prior to Being Beneficially Owned
Name and Address of Beneficial Owner Offering (1) Offered After Offering (1)
- ------------------------------------ ------------ --------- ------------------
Number Percent

Entities Affiliated with HealthCare 2,482,343 2,479,093 3,250 *
Ventures LLC
44 Nassau Street
Princeton, New Jersey 08542

Timothy Springer 773,741 770,825 2,916 *
Center for Blood Research
200 Longwood Avenue
Boston, Massachusetts 02115

Entities Affiliated with Schroders PLC 756,451 291,667 464,784 4.9
120 Cheapside
London EC2V 6DS
England

Warner-Lambert 618,466 618,466 -- *
201 Tabor Road
Morris Plains, New Jersey 07950

Roche Finance Ltd 610,301 610,301 -- *
c/o Hoffman-La Roche, Ltd.
124 Grensacherstrasse
CH-4002 Basel
Switzerland

Entities Affiliated with Rho Management 548,307 548,307 -- *
Co., Inc.
767 Fifth Avenue
New York, New York 10153

Lombard Odier & Cie 425,325 425,325 -- *
Toedistrasse 36
CH8027

Zurich, Switzerland

Perseus Capital, LLC 416,667 416,667 -- *
The Army and Navy Club Building
1627 I Street NW
Suite 610
Washington, DC 20006

S.R. One Ltd 222,222 222,222 -- *
Bay Colony Executive Park, Suite 315
565 East Swedesford Road
Wayne, Pennsylvania 19087

Goldman Sachs & Co. 166,667 166,667 -- *
One New York Plaza
New York, New York 10004

Springer Family Trust 134,067 134,067 -- *
245 Walcott Road
Chestnut Hill, Massachusetts

Peretz Family Investment 119,008 115,758 3,250 *
20 Larchwood Drive
Cambridge, MA 02138

New Day Investment Partnership 111,111 111,111 -- *
6690 LaJolla Scenic South
LaJolla, California 92037

Entities Affiliated with Weiss Peck & 71,111 71,111 -- *
Greer LLC
One New York Plaza
New York, New York 10004

YK Capital L.P. 52,750 50,000 2,750 *
509 Rochampton Road
Hillsborough, California 94010

Four Partners 33,334 33,334 -- *
667 Madison Avenue
7th Floor
New York, New York 10021

Christopher Walsh 10,898 945 9,953 *
Harvard Medical School
45 Shattuck Street
Boston, Massachusetts 02115

Daniel Kisner 5,444 5,444 -- *
1849 Montgomery Avenue
Cardiff, California 92007

Todd Noonan 500 500 -- *
International Creative
Management, Inc.
40 West 57th Street, 18th Floor
New York, New York 10019

- --------------------------------------------------------------------------------
* Less than 1% of the outstanding shares of common stock.

(1) Beneficial ownership is determined in accordance with Rule 13d-3(d)
promulgated by the Commission under the Securities Exchange Act of
1934, as amended. Shares of common stock issuable pursuant to options,
warrants and convertible securities, to the extent such securities are
currently exercisable or convertible within 60 days of September 30,
1998, are treated as outstanding for computing the percentage of the
person holding such securities but are not treated as outstanding for
computing the percentage of any other person. Unless otherwise noted,
each person or group identified possesses sole voting and investment
power with respect to shares, subject to community property laws where
applicable. Shares not outstanding but deemed beneficially owned by
virtue of the right of a person or group to acquire them within 60 days
are treated as outstanding only for purposes of determining the number
of and percent owned by such person or group.

PLAN OF DISTRIBUTION

The shares of common stock may be sold from time to time by the selling
stockholders in one or more transactions at fixed prices, at market prices at
the time of sale, at varying prices determined at the time of sale or at
negotiated prices. The selling stockholders may offer their shares of common
stock in one or more of the following transactions:

- on any national securities exchange or quotation service on
which the common stock may be listed or quoted at the time of
sale, including the Nasdaq National Stock Market,

- in the over-the-counter market,
- in private transactions,
- through options,
- by pledge to secure debts and other obligations, or
- a combination of any of the above transactions.

If required, we will distribute a supplement to this prospectus to
describe material changes in the terms of the offering.

The shares of common stock described in this prospectus may be sold
from time to time directly by the selling stockholders. Alternatively, the
selling stockholders may from time to time offer shares of common stock to or
through underwriters, broker/dealers or agents. The selling stockholders and any
underwriters, broker/dealers or agents that participate in the distribution of
the shares of common stock may be deemed to be "underwriters" within the meaning
of the Securities Act of 1933. Any profits on the resale of shares of common
stock and any compensation received by any underwriter, broker/dealer or agent
may be deemed to be underwriting discounts and commissions under the Securities
Act of 1933.

Any shares covered by this prospectus which qualify for sale pursuant
to Rule 144 under the Securities Act of 1933 may be sold under Rule 144 rather
than pursuant to this prospectus. The selling stockholders may not sell all of
the shares. The selling stockholders may transfer, devise or gift such shares by
other means not described in this prospectus.

To comply with the securities laws of certain jurisdictions the common
stock must be offered or sold only through registered or licensed brokers or
dealers. In addition, in certain jurisdictions, the common stock may not be
offered or sold unless they have been registered or qualified for sale or an
exemption is available and complied with.

Under the Securities Exchange Act of 1934, any person engaged in a
distribution of the common stock may not simultaneously engage in market-making
activities with respect to the common stock for nine business days prior to the
start of the distribution. In addition, each selling stockholder and any other
person participating in a distribution will be subject to the Securities
Exchange Act of 1934 which may limit the timing of purchases and sales of common
stock by the selling stockholders or any such other person. These factors may
affect the marketability of the common stock and the ability of brokers or
dealers to engage in market-making activities.

All expenses of this registration will be paid by LeukoSite. These
expenses include the SEC's filing fees and fees under state securities or "blue
sky" laws. The selling stockholders will pay all underwriting discounts and
selling commissions, if any.

LEGAL MATTERS

Bingham Dana LLP, Boston, Massachusetts will give its opinion that the
shares offered in this prospectus have been validly issued and are fully paid
and non-assessable. Justin P. Morreale, a partner at Bingham Dana LLP, is the
Secretary of LeukoSite. Other partners and associates at Bingham Dana LLP own a
total of approximately 1,600 shares of common stock.

EXPERTS

The consolidated financial statements of LeukoSite as of and for the
year ended December 31, 1997, incorporated by reference into this prospectus and
this Registration Statement, have been audited by Arthur Andersen LLP,
independent public accountants, as indicated in their report with respect
thereto, and are included herein in reliance upon the authority of said firm as
experts as giving said report.

- --------------------------------------------- -------------------------------
- --------------------------------------------- -------------------------------

We have not authorized any dealer,
salesperson or other person to give any
information or to make any representations
not contained in this prospectus or any
Prospectus Supplement. You must not rely on
any unauthorized information. This
prospectus is not an offer of these 7,071,810 Shares
securities in any state where an offer is
not permitted. The information in this LeukoSite, Inc.
prospectus is current as of October 15,
1998. You should not assume that this Common Stock
prospectus is accurate as of any other date.
------------------
Table of Contents

Page

Where You Can Get More
Information................ 2

Forward-looking Statements... 3

Risk Factors................. 3 PROSPECTUS

The Company.................. 7 ____________ , 1998

Recent Developments.......... 7 -------------------

Use of Proceeds.............. 8

Selling Stockholders......... 8

Plan of Distribution......... 10

Legal Matters................ 11

Experts...................... 11

- --------------------------------------------- -------------------------------
- --------------------------------------------- -------------------------------

PART II
INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The expenses in connection with the issuance and distribution of the
securities being registered are set forth in the following table (all amounts
except the registration fee and the listing fee are estimated):

SEC Registration Fee........................ $ 14,874.49
Nasdaq National Market Listing Fees......... 0
Legal Fees and Expenses..................... 20,000
Accountants' Fees and Expenses.............. 1,500
Miscellaneous Costs......................... 0
Total................................. 36,374.49

All expenses in connection with the issuance and distribution of the
securities being offered shall be borne by the Company.

Item 15. Indemnification of Directors and Officers

Section 145 of the Delaware General Corporation Law empowers a Delaware
corporation to indemnify its officers and directors and certain other persons to
the extent and under the circumstances set forth therein.

The Restated Certificate of Incorporation and the Amended and Restated
By-Laws of the Company, copies of which are filed herein as Exhibit 3.3 and 3.4,
provide for advancement of expenses and indemnification of officers and
directors of the Registrant and certain other persons against liabilities and
expenses incurred by any of them in certain stated proceedings and under certain
stated conditions to the fullest extent permissible under Delaware law.

The Registration Rights Agreement, dated as of July 1, 1998, provides
for indemnification by the Registrant of each of the Selling Stockholders
against certain liabilities under the Securities Act of 1933, the Securities
Exchange Act of 1934, state securities laws or otherwise, and provides for
indemnification by the Selling Stockholders of the Registrant and its directors,
its officers and certain control persons against certain liabilities under the
Securities Act of 1933, the Securities Exchange Act of 1934, state securities
laws or otherwise.

Item 16. Exhibits

Exhibits
- --------

*3.3 Restated Certificate of Incorporation of the Registrant.
*3.4 Amended and Restated By-Laws of the Registrant, as amended to date.
*4.1 Specimen certificate for shares of common stock.
5 Opinion of Bingham Dana LLP
23.1 Consent of Bingham Dana LLP (included in Exhibit 5.1)
23.2 Consent of Arthur Andersen LLP

- -----------

* Incorporated by reference from the Registrant's Registration
Statement on Form S-1 (Registration No. 333-30213).

Item 17. Undertakings

The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or
sales are being made pursuant to this Registration Statement,
a post-effective amendment to this Registration Statement to
include any material information with respect to the plan of
distribution not previously disclosed in this Registration
Statement or any material change to such information in this
Registration Statement;

(2) That, for the purpose of determining any
liability under the Securities Act of 1933, each such
post-effective amendment shall be deemed to be a new
Registration Statement relating to the securities offered
therein, and the offering of such securities at that time
shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a
post-effective amendment any of the securities being
registered which remain unsold at the termination of the
offering.

The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or 15 (d) of the Securities
Exchange Act of 1934 (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of
1934) that is incorporated by reference in the registration statement shall be
deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the Registrant pursuant to the foregoing provisions described in Item 15 above,
or otherwise, the Registrant has been advised that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the Securities Act and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act and will be governed by the final adjudication of such issue.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant, LeukoSite, Inc., certifies that it has reasonable grounds to
believe that it meets all of the requirements for filing on Form S-3 and has
duly caused this Registration Statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Cambridge, Commonwealth
of Massachusetts, on this 15th day of October, 1998.

LEUKOSITE, INC.

By:

/s/ Christopher K. Mirabelli
-------------------------------------
Christopher K. Mirabelli

Chairman of the Board of Directors,
President and Chief Executive Officer

POWER OF ATTORNEY

Each person whose signature appears below hereby appoint each of
Christopher K. Mirabelli and Augustine Lawlor severally, acting alone and
without the other, his/her true and lawful attorney-in-fact with the authority
to execute in the name of each such person, any and all amendments (including
without limitation, post-effective amendments) to this Registration Statement on
Form S-3, to sign any and all additional registration statements relating to the
same offering of securities as this Registration Statement that are filed
pursuant to Rule 462(b) of the Securities Act, and to file such registration
statements with the Securities and Exchange Commission, together with any
exhibits thereto and other documents therewith, necessary or advisable to enable
the Registrant to comply with the Securities Act, and any rules, regulations and
requirements of the Securities and Exchange Commission in respect thereof, which
amendments may make such other changes in the Registration Statement as the
aforesaid attorney-in-fact executing the same deems appropriate.

Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated:

Signature Title Date
--------- ----- ----

/s/ Christopher K. Mirabelli
- -------------------------------------------- Chairman of the Board of Directors, President, Chief October 15, 1998
Christopher K. Mirabelli and Executive Officer (Principal Executive Officer)

/s/ Augustine Lawlor Vice President, Business Development, Chief October 15, 1998
- -------------------------------------------- Financial Office and Treasurer (Principal Financial
Augustine Lawlor and Accounting Officer)

/s/ Kate Bingham Director October 15, 1998
- --------------------------------------------
Kate Bingham

/s/ John W. Littlechild Director October 15, 1998
- ---------------------------------------------
John W. Littlechild

/s/ Martin Peretz Director October 15, 1998
- --------------------------------------------
Martin Peretz

/s/ Mark Skaletsky Director October 15, 1998
- --------------------------------------------
Mark Skaletsky

/s/ Timothy A. Springer Director October 15, 1998
- --------------------------------------------
Timothy A. Springer

Signature Title Date
--------- ----- ----

/s/ Christopher T. Walsh Director October 15, 1998
- --------------------------------------------
Christopher T. Walsh

/s/ Yasunori Kaneko Director October 15, 1998
- --------------------------------------------
Yasunori Kaneko

EXHIBIT INDEX

Exhibits
--------

*3.3 Restated Certificate of Incorporation of the Registrant.
*3.4 Amended and Restated By-Laws of the Registrant, as amended to date.
*4.1 Specimen certificate for shares of common stock.

5 Opinion of Bingham Dana LLP

23.1 Consent of Bingham Dana LLP (included in Exhibit 5.1)
23.2 Consent of Arthur Andersen LLP

- -----------

* Incorporated by reference from the Registrant's Registration
Statement on Form S-1 (Registration No. 333-30213).