<PAGE>
FILED PURSUANT TO RULE 424(B)(5)REGISTRATION NO. 333-47594
PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED OCTOBER 16, 2000
<TABLE>
<S> <C>
2,300,000 SHARES
ALEXION PHARMACEUTICALS, INC. [LOGO]
COMMON STOCK
</TABLE>
--------------------------------------------------------------------------------
<TABLE>
<S> <C>
- ALEXION PHARMACEUTICALS, INC. IS OFFERING - CLOSING PRICE OF OUR COMMON STOCK ON
2,300,000 SHARES OF COMMON STOCK BY THIS OCTOBER 27, 2000: $94.375 PER SHARE
PROSPECTUS SUPPLEMENT.
- TRADING SYMBOL: NASDAQ NATIONAL MARKET--
ALXN
</TABLE>
------------------------
THIS INVESTMENT INVOLVES RISKS. SEE "RISK FACTORS" BEGINNING ON PAGE 3 OF THE
ACCOMPANYING PROSPECTUS AND PAGE S-3 OF THIS PROSPECTUS SUPPLEMENT.
The underwriter will purchase the common stock from Alexion at a price of $90.75
per share resulting in $208,725,000 aggregate proceeds to Alexion.
The underwriter may offer the common stock through negotiated transactions at
market prices prevailing at the time of sale, at prices relating to prevailing
market prices or at negotiated prices. See "Underwriting"
NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY OTHER REGULATORY BODY HAS
APPROVED OR DISAPPROVED THESE SECURITIES, OR PASSED UPON THE ACCURACY OR
ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL
OFFENSE.
U.S. BANCORP PIPER JAFFRAY
The date of this prospectus supplement is October 30, 2000.
<PAGE>
TABLE OF CONTENTS
<TABLE>
<CAPTION>
PROSPECTUS SUPPLEMENT PAGE
--------------------- --------
<S> <C>
About This Prospectus Supplement............................ S-3
Summary of the Offering..................................... S-3
Recent Developments......................................... S-3
Risk Factors................................................ S-3
Use Of Proceeds............................................. S-4
Dilution.................................................... S-5
Underwriting................................................ S-6
Legal Matters............................................... S-6
Experts..................................................... S-6
Where You Can Find More Information......................... S-7
<CAPTION>
PROSPECTUS
----------
Summary. 1
<S> <C>
ALEXION................................................... 1
RECENT DEVELOPMENTS....................................... 2
THE SECURITIES WE MAY OFFER............................... 2
Risk Factors................................................ 3
Special Note Regarding Forward-Looking Statements........... 10
Use of Proceeds............................................. 10
Description of Common Stock................................. 11
Description of Warrants..................................... 11
Plan of Distribution........................................ 13
Legal Matters............................................... 13
Experts..................................................... 14
Where You Can Find More Information......................... 14
</TABLE>
------------------------
You should rely only on the information contained in this prospectus
supplement, the accompanying prospectus and the documents incorporated by
reference. We have not authorized anyone to provide you with information
different from that contained in any of these documents. The information
contained in these documents is accurate only as of the date of each document,
as the case may be, regardless of the time of delivery of this prospectus
supplement and accompanying prospectus or of any sale of common stock. Our
business, financial condition, results of operations and prospects may change
after the date set forth in each document in which the information is presented.
------------------------
S-2
<PAGE>
ABOUT THIS PROSPECTUS SUPPLEMENT
We provide information to you about this offering of shares of our common
stock in two separate documents: (a) the accompanying prospectus, which provides
general information, some of which may not apply to this offering; and (b) this
prospectus supplement, which describes the specific details regarding this
offering. Generally, when we refer to this "prospectus," we are referring to
both documents combined.
If information in this prospectus supplement is inconsistent with the
accompanying prospectus, you should rely on this prospectus supplement.
This prospectus supplement, the accompanying prospectus and the documents
incorporated by reference contain some "forward-looking statements" as defined
in the Private Securities Litigation Reform Act of 1995 and information relating
to us that is based on the beliefs of our management, as well as assumptions
made by, and the information currently available to, our management. When used
in these documents, the words "estimate," "project," "believe," "anticipate,"
"intend," "expect" and similar expressions are intended to identify
forward-looking statements. These statements reflect our current views with
respect to future events and are subject to risks and uncertainties that could
cause actual results to differ materially from those contemplated in these
forward-looking statements, including those risks discussed in this prospectus.
You are cautioned not to place undue reliance on these forward-looking
statements, which speak only as of the date of this prospectus supplement, the
accompanying prospectus or the documents incorporated by reference, as the case
may be. Except for special circumstances in which a duty to update arises when
prior disclosure becomes materially misleading in light of subsequent events, we
do not intend to update any of these forward-looking statements to reflect
events or circumstances after the date of this prospectus or to reflect the
occurrence of unanticipated events.
RECENT DEVELOPMENTS
On October 25, 2000, we entered into an agreement granting an exclusive
worldwide license to commercialize our high throughput screening system to
Arradial, Inc., a newly-organized company formed for this purpose. In exchange
for the license, Arradial is paying us $200,000. Arradial is also obligated to
issue to us the greater of 525,000 Arradial shares or 15% of the equity
ownership of Arradial. We retained the right to use our high throughput
screening system for commercial development of therapeutic antibodies. We may
terminate this agreement if Arradial fails to attain specified development,
corporate and financing milestones.
RISK FACTORS
Before purchasing our common stock, you should carefully consider the risks
described below in this section, risks described under the heading "Risk
Factors" beginning on page 3 of the accompanying prospectus and the risks
described in the documents incorporated by reference into this prospectus
supplement and the accompanying prospectus.
THERE IS A LARGE NUMBER OF SHARES THAT MAY BE SOLD IN THE MARKET FOLLOWING THIS
OFFERING, WHICH MAY DEPRESS THE MARKET PRICE OF OUR COMMON STOCK.
Sales of a substantial number of shares of our common stock in the public
market following this offering could cause the market price of our common stock
to decline. Upon completion of this offering, we will have outstanding an
aggregate of 17,993,174 shares of common stock, assuming no exercise of
outstanding options or warrants or conversion of convertible notes. All of the
shares sold in this offering will be freely tradable without restriction or
further registration under the Securities Act of 1933 unless these shares are
purchased by affiliates. In addition, as of October 27, 2000, 2,528,518 shares
are issuable upon conversion of warrants and exercise of options granted by us,
which have also been registered for resale on registration statements filed with
the SEC. We also may issue up to 1,275,555 shares of common stock upon
conversion of 5 3/4% convertible subordinated notes due 2007, which have been
registered for resale pursuant to a registration statement filed with the SEC.
S-2
<PAGE>
OUR MANAGEMENT WILL HAVE BROAD DISCRETION WITH RESPECT TO THE USE OF THE
PROCEEDS OF THIS OFFERING, AND MAY NOT APPLY THE PROCEEDS TO USES THAT WILL
BENEFIT STOCKHOLDERS.
Our management will have broad discretion as to how to use the proceeds of
this offering. You will be relying on the judgment of our management regarding
the application of the proceeds of this offering. The results and effectiveness
of the use of the proceeds are uncertain.
USE OF PROCEEDS
We expect the net proceeds from this sale of common stock to be
approximately $208.5 million after deducting estimated expenses. We intend to
use the net proceeds from the sale of the common stock to fund research and
clinical development activities, manufacturing development, manufacturing and
commercialization of our product candidates; drug discovery; as well as for
working capital and general corporate purposes, including for potential
acquisitions of companies, additional technologies and compounds. Our management
will have broad discretion in the allocation of the net proceeds of the
offering. Pending such uses, we intend to invest the net proceeds in short-term,
investment grade, interest-bearing securities.
DILUTION
Our net tangible book value as of July 31, 2000 was approximately
$57.7 million or $3.81 per share of common stock. Net tangible book value per
share is determined by dividing our net tangible book value, which consists of
tangible assets less total liabilities, by the number of shares of common stock
outstanding at that date. Without taking into account any other changes in the
net tangible book value after July 31, 2000, other than to give effect to our
receipt of the estimated net proceeds from the sale of the 2,300,000 shares of
common stock from the offering at an offering price of $90.75 per share, less
estimated offering expenses, our net tangible book value as of July 31, 2000
after giving effect to the items above would have been approximately
$266.2 million or $15.27 per share. This represents an immediate increase in the
net tangible book value per share of $11.46 per share to existing stockholders
and an immediate dilution of $75.48 per share to new investors. The following
table illustrates this per share dilution:
<TABLE>
<S> <C> <C>
Offering price.............................................. $90.75
Net tangible book value per share........................... $ 3.81
Increase in net tangible book value per share after the
offering.................................................. $11.46
Net tangible book value per share after the offering........ $15.27
------
Dilution per share to new investors......................... $75.48
======
</TABLE>
This table is based on the number of outstanding shares as of July 31, 2000
and does not include the following:
- 1,275,555 shares of common stock issuable upon conversion of our 5 3/4%
convertible subordinated notes;
- 2,684,215 shares of common stock issuable upon exercise of outstanding
stock options as of July 31, 2000 at a weighted average exercise price of
$21.09 per share;
- 18,117 shares of common stock issuable upon exercise of outstanding
warrants as of July 31, 2000 at an exercise price of $9.90;
- 355,594 shares of common stock issued in connection with the acquisition
of Proliferon, Inc. on September 22, 2000; and
- 44,364 shares of common stock issuable upon exercise of stock options,
granted in connection with our acquisition of Proliferon, Inc. on
September 22, 2000, at a weighted average exercise price of $44.35 per
share.
S-3
<PAGE>
As of October 27, 2000, there were 2,510,401 shares of common stock issuable
upon the exercise of outstanding stock options at a weighted average exercise
price of $24.38 per share and 18,117 shares of common stock issuable upon
exercise of outstanding warrants.
UNDERWRITING
We have entered into a purchase agreement with U.S. Bancorp Piper
Jaffray Inc. with respect to the shares being offered by this prospectus
supplement. Subject to certain conditions, we have agreed to sell to U.S.
Bancorp Piper Jaffray Inc., and U.S. Bancorp Piper Jaffray Inc. has agreed to
purchase from us, the 2,300,000 shares of common stock offered hereby.
U.S. Bancorp Piper Jaffray Inc. proposes to offer the shares of common stock
from time to time for sale in one or more negotiated transactions or otherwise
at market prices prevailing at the time of saleor at negotiated prices, subject
to receipt and acceptance by it and subject to its right to reject any order in
whole or in part. In connection with the sale of the shares of common stock
offered hereby, U.S. Bancorp Piper Jaffray Inc. may be deemed to have received
compensation in the form of underwriting discounts.
In connection with the offering, U.S. Bancorp Piper Jaffray Inc. may
purchase or sell shares of common stock in the open market. These may include
short sales and stabilizing transactions that stabilize, maintain, or otherwise
affect the price of the common stock during and after the offering.
Specifically, U.S. Bancorp Piper Jaffray Inc. may over-allot or otherwise create
a short position in the common stock for their own account by selling more
shares of common stock than we have sold to it. U.S. Bancorp Piper Jaffray Inc.
may close out any short position by purchasing shares in the open market.
These activities by U.S. Bancorp Piper Jaffray Inc. may maintain or
otherwise affect the market price of the common stock. As a result, the price of
the common stock may be higher than the price that otherwise might exist in the
open market. If these activities are commenced, they may be discontinued at any
time. These transactions may be effected on the Nasdaq National Market.
We estimate that our share of the total expenses for the offering will be
approximately $225,000. This amount includes approximately $55,103 for the SEC
registration fee, $65,000 in legal fees and expenses, $35,000 in accounting fees
and expenses and $69,897 in miscellaneous, based upon estimates more fully set
forth in Item 14 of our Registration Statement on Form S-3, effective
October 16, 2000 of which this prospectus supplement is a part.
We have agreed to indemnify U.S. Bancorp Piper Jaffray Inc. against some
liabilities, including liabilities under the Securities Act.
U.S. Bancorp Piper Jaffray Inc. has performed some investment banking and
advisory services for us from time to time for which it has received customary
fees and expenses. U.S. Bancorp Piper Jaffray Inc. may, from time to time,
engage in transactions with, and perform services for, us and our affiliates in
the ordinary course of business.
LEGAL MATTERS
Fulbright & Jaworski L.L.P., New York, New York, will pass upon the validity
of the securities offered hereby and some other legal matters on behalf of
Alexion. Legal matters in connection with the offering will be passed upon for
the underwriter by Morgan, Lewis & Bockius, LLP.
EXPERTS
The audited consolidated financial statements incorporated by reference in
this prospectus supplement and accompanying prospectus and elsewhere in the
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 in
accounting and auditing in giving said report.
S-4
<PAGE>
WHERE YOU CAN FIND MORE INFORMATION
We file annual, quarterly and special reports, proxy statements and other
information with the Securities and Exchange Commission. You may read and copy
any reports, statements or other information filed by us at the Commission's
public reference room at Room 1024, Judiciary Plaza, 450 Fifth Street, N.W.,
Washington, D.C. 20549 and the regional offices of the Commission located at
Seven World Trade Center, 13th Floor, New York, New York 10048, and 500 West
Madison Street, Chicago, Illinois 60661. Copies of such material can be also
obtained from the Public Reference Section of the Commission at 450 Fifth
Street, N.W., Washington, D.C. 20549, and its public reference rooms in New
York, New York and Chicago, Illinois, at prescribed rates. Please call the
Commission at 1-800-SEC-0330 for further information on the public reference
rooms. Copies of such information may also be inspected at the reading room of
the library of the National Association of Securities Dealers, Inc., 1735
K Street, N.W., Washington, D.C. 20006. Our filings with the Commission are also
available to the public from commercial document retrieval services and at the
Commission's web site at "http://www.sec.gov."
We "incorporate by reference" the information we file with the Commission
(File No. 0-27756), which means that we can disclose important information to
you by referring you to another document we filed with the Commission. The
information incorporated by reference is an important part of this prospectus
supplement and accompanying prospectus, and information that we file later with
the Commission will automatically update and supersede this information. We
incorporate by reference the documents listed below and any filings made with
the Commission under Sections 13(a), 13(c), 14 or 15(d) of the Securities
Exchange Act of 1934, as amended, after the date of this prospectus but before
the end of any offering made under this prospectus supplement and accompanying
prospectus:
- our current reports on Form 8-K, filed on September 25, 2000, October 3,
2000 and October 27, 2000;
- our annual report on Form 10-K for the fiscal year ended July 31, 2000,
filed on October 6, 2000;
- our registration statement on Form 8-A, filed on February 21, 1997, as
amended on October 6, 2000; and
- our registration statement on Form 8-A, filed on February 12, 1996.
You should read the information relating to us in this prospectus supplement
and accompanying prospectus together with the information in the documents
incorporated by reference.
Any statement contained in a document incorporated by reference herein,
unless otherwise indicated therein, speaks as of the date of the document.
Statements contained in this prospectus may modify or replace statements
contained in the documents incorporated by reference.
We will furnish without charge to you, upon written or oral request, a copy
of any or all of the documents described above, except for exhibits to such
documents, unless such exhibits are specifically incorporated by reference into
such documents. Requests should be addressed to: Alexion Pharmaceuticals, Inc.,
25 Science Park, New Haven, Connecticut 06511, (203) 776-1790, Attention: David
W. Keiser, Executive Vice President and Chief Operating Officer.
S-5
<PAGE>
2,300,000 SHARES
ALEXION PHARMACEUTICALS, INC.
COMMON STOCK
[LOGO]
---------------------
PROSPECTUS SUPPLEMENT
---------------------
U.S. BANCORP PIPER JAFFRAY
OCTOBER 30, 2000
