Exhibit 99.1



                           Investor Contact:                      Media Contact:
                             Carol A. Sexton       Joan Kureczka/Ellen M. Martin
            Cell Pathways Investor Relations          Kureczka/Martin Associates
                                215-706-3800                        415-821-2413

For Immediate Release

                 CELL PATHWAYS TO MERGE WITH OSI PHARMACEUTICALS
                        IN $32 MILLION STOCK TRANSACTION

HORSHAM, PA (FEBRUARY 10, 2003) - Cell Pathways, Inc. (Nasdaq:CLPA) announced
today that it has signed an agreement whereby Cell Pathways will be acquired by
OSI Pharmaceuticals (Nasdaq: OSIP) via a stock-for-stock merger valued at
approximately $32 million. OSI will exchange .0567 shares of OSI for every share
of Cell Pathways upon closing of the transaction, which is subject to the
approval of Cell Pathways' stockholders and is estimated to occur by late Spring
2003. Based on OSI's most recent closing share price, this represents $0.80 per
share, a 58% premium to Cell Pathways' last closing price. OSI will also provide
additional consideration in the form of a five-year contingent value right (CVR)
through which each share of Cell Pathways held by shareholders of record on the
date of the merger closure may be exchanged for an additional .040 share of OSI
in the event of a filing of a new drug application (NDA) for either of Cell
Pathways' two leading clinical candidates Aptosyn(R) (exisulind) or CP461. CIBC
World Markets served as the financial advisor to Cell Pathways on this
transaction.

"This transaction represents an excellent opportunity, both for our shareholders
and for realizing the full potential of our company's innovative drug discovery
platform and products," said Robert J. Towarnicki, Cell Pathways chairman,
president and chief executive officer. "OSI Pharmaceuticals is a leading
oncology-focused biotechnology company with a broad product pipeline and the
substantial clinical development and financial resources required to see our
novel Selective Apoptotic Antineoplastic Drugs (SAANDs) through to
commercialization."

"We believe this transaction represents a win-win for the shareholders of both
OSI and Cell Pathways," stated Colin Goddard, Ph.D., chief executive officer of
OSI. "We have identified apoptosis as one of the most important areas of
investigation in cancer research today. We believe the Cell Pathways' platform
represents an innovative and credible approach to the discovery and development
of pro-apoptotic anti-cancer drugs and we are convinced that OSI's financial
resources and deep clinical and regulatory expertise provide the best vehicle to
draw out the value we believe inherent in this asset. Further, we are adding to
our portfolio a marketed product recently launched that provides much needed
pain relief to cancer patients suffering


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                                 CELL PATHWAYS TO MERGE WITH OSI PHARMACEUTICALS
                                                IN $32 MILLION STOCK TRANSACTION
                                                                          PAGE 2


from oral mucositis. We believe this product has the potential to be grown into
a valuable niche product for OSI."

Cell Pathways invites you to listen to its analyst conference call, which will
be held today, February 10, 2003 beginning at 10:00 a.m. Eastern Time. Listeners
may access the live call by dialing within the U.S. 1-800-659-4363, or outside
the U.S. 1-816-650-0613. The call will also be broadcast live over the company's
web site at www.cellpathways.com. A replay of the conference call will be
available by telephone for 48 hours following the end of the call and can be
accessed by calling 1-800-252-6030, or international phone number
1-402-220-2491. The ID number for accessing the replay is 15475236. The webcast
of the call will be available until February 17, 2003.

OSI Pharmaceuticals, Inc. is a leading biotechnology company focused on the
discovery, development and commercialization of high-quality, next-generation
oncology products that both extend and improve the quality-of-life for cancer
patients worldwide. The company has a balanced pipeline of oncology drug
candidates that includes both next-generation cytotoxic agents and novel
mechanism-based, gene-targeted therapeutics. OSI's most advanced drug candidate,
Tarceva(TM) (erlotinib HCl), a small-molecule inhibitor of the EGFR gene, is
currently in Phase III clinical trials for lung and pancreatic cancers.

Cell Pathways, Inc., headquartered in Horsham, Pennsylvania, is an emerging
biopharmaceutical company focused on the discovery, development and
commercialization of novel and unique medications to treat and prevent cancer
and to treat certain autoimmune diseases. The company's investigational drugs
are orally active small molecules designed to selectively induce apoptosis, or
programmed cell death, in precancerous and cancerous cells. Cell Pathways has
two drug candidates in clinical development: Aptosyn(R), which is currently in
Phase III trials in combination with Taxotere(R) for the treatment of advanced
non-small cell lung cancer, and CP461, a more potent, second-generation molecule
that is currently being evaluated in dose ranging Phase I studies and a series
of exploratory Phase II studies in chronic lymphocytic leukemia, renal cell
carcinoma and prostate cancer. In addition, CP461 is being evaluated in a Phase
II study for inflammatory bowel disease. In addition to the apoptosis platform,
Cell Pathways markets Gelclair(TM) Concentrated Oral Gel manufactured by
Sinclair Pharma, Ltd. of the United Kingdom. Gelclair(TM) is an FDA approved
product for the treatment of pain associated with oral mucositis, a debilitating
side effect often seen in cancer patients undergoing radiation treatment and
chemotherapy. For additional information on Cell Pathways, Inc., visit the
company's web site at http://www.cellpathways.com.

This news release contains forward-looking statements, including among others,
statements regarding the expected timing and benefits of the merger, the value
of the transaction and the potential market for certain of Cell Pathways'
products. These statements are subject to known and unknown risks and
uncertainties that may cause actual future experience and results to differ
materially from the statements made. Factors that might cause such a difference
include, among others, the ability of Cell Pathways to obtain shareholder
approval, any fluctuations in the trading price of OSI Pharmaceuticals' common
stock, delays in completing the merger, difficulties in integrating the
businesses of OSI and Cell Pathways, costs related to the merger, the success of
research and development activities and of pre-clinical development thereof, the
completion of clinical trials, the FDA review process and other governmental
regulation, Cell Pathways' and pharmaceutical collaborators' abilities to
successfully develop and commercialize drug candidates, competition from other
pharmaceutical companies, product pricing and third party reimbursement, and
other factors described in the filings of Cell Pathways and OSI Pharmaceuticals
with the Securities and Exchange Commission.


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                                 CELL PATHWAYS TO MERGE WITH OSI PHARMACEUTICALS
                                                IN $32 MILLION STOCK TRANSACTION
                                                                          PAGE 3


          Additional Information About the Merger and Where to Find It

In connection with the proposed merger, OSI will file with the Securities and
Exchange Commission (SEC) a registration statement on Form S-4. The registration
statement will include a proxy statement of Cell Pathways for a meeting of its
stockholders to consider and vote upon the proposed merger. The registration
statement will also serve as a prospectus of OSI with respect to the shares of
OSI to be distributed to stockholders of Cell Pathways in the proposed
transaction. OSI and Cell Pathways will file the proxy statement/prospectus with
the SEC as soon as practicable. INVESTORS AND SECURITY HOLDERS ARE URGED TO
CAREFULLY READ THE PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED MERGER
TRANSACTION, WHEN IT BECOMES AVAILABLE, AND ANY OTHER DOCUMENTS FILED WITH THE
SEC, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT OSI, CELL PATHWAYS,
THE MERGER AND RELATED MATTERS.

Investors and security holders will be able to obtain a free copy of the proxy
statement/prospectus (when it is available) and other documents filed by OSI and
Cell Pathways at the SEC's web site at http://www.sec.gov. In addition, you may
obtain such documents from OSI or from Cell Pathways free of charge by
requesting them in writing from OSI Pharmaceuticals, Inc., 58 South Service
Road, Suite 110, Melville, New York 11747, Attention: Investor Relations,
telephone: (631) 962-2000, or from Cell Pathways, Inc., 702 Electronic Drive,
Horsham, Pennsylvania 19044, Attention: Investor Relations, telephone: (215)
706-3800.

OSI, Cell Pathways, their respective officers and directors and certain other
members of management or employees may be deemed to be participants in the
solicitation of proxies from stockholders of Cell Pathways with respect to the
transactions contemplated by the merger agreement. A description of any
interests that OSI's or Cell Pathways' directors and executive officers have in
the proposed merger will be available in the proxy statement/prospectus when it
becomes available.

This press release is not an offer to purchase shares of Cell Pathways, nor is
it an offer to sell shares of OSI's common stock, which may be issued in any
proposed merger with Cell Pathways. Any issuance of OSI common stock in any
proposed merger with Cell Pathways must be registered under the Securities Act
of 1933, as amended, and such OSI common stock would be offered only by means of
a prospectus complying with such act.


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