Filed by: OSI Pharmaceuticals, Inc.
Pursuant to Rule 425 Under the Securities Act of 1933

Subject Company: Cell Pathways, Inc.
Commission File No.: 000-24889

The following press release was filed as an exhibit to a Current Report on Form
8-K filed by OSI, today May 14, 2003, with the Securities and Exchange
Commission.

[GRAPHIC OMITTED]

NEWS RELEASE

Contact: OSI Pharmaceuticals, Inc. Burns McClellan (representing OSI)
Kathy Galante Jonathan Nuggent (investors)
Director Kathy Jones, Ph.D. (media)
Investor & Public Relations (212) 213-0006
(631) 962-2000

OSI PHARMACEUTICALS ANNOUNCES SECOND QUARTER FINANCIAL RESULTS

MELVILLE, NEW YORK - MAY 14, 2003 -- OSI Pharmaceuticals, Inc. (NASDAQ: OSIP)
today announced its financial results for the Company's second quarter ended
March 31, 2003. The Company reported net losses for the second quarter and
six-month period of $27.2 million ($0.75 net loss per share) and $57.3 million
($1.57 net loss per share), respectively, compared to net losses of $24.5
million ($0.68 net loss per share) and $166.9 million ($4.68 net loss per share)
for the second quarter and six-month period, respectively, in the prior year.
Adjusted for an in-process research and development charge of $130.2 million (or
$3.65 per share) related to the acquisition of the oncology assets of Gilead
Sciences, Inc. in December 2001, the net loss for the six-month period in the
prior year would have been $36.7 million ($1.03 net loss per share). Increased
investments in the Company's clinical development program, most notably for the
Company's most advanced clinical candidate, Tarceva(TM) (erlotinib HCl), are the
principal factors for the increased net loss for the six-month period versus the
adjusted prior year numbers excluding the in-process research and development
charge. These increased development costs have been incurred according to plan
and are in-line with prior guidance.

The Company also announced two major transactions during the quarter: an
agreement to acquire Cell Pathways, Inc. in a stock for stock merger valued at
approximately $32 million based upon the closing price of the Company's stock on
February 7, 2003, and a co-promotion agreement with Serono, S.A., giving the
Company exclusive rights to market the drug Novantrone(R) (mitoxantrone for
injection concentrate) to cancer patients in the United States. In connection
with this latter transaction, the Company paid Serono $45 million in signing
fees and $10 million in transition service fees upon execution of the agreement.
Both payments are reflected in the approximately $362 million in cash and
investments the Company retained on its balance sheet at the end of the quarter.

"The second quarter of our Fiscal 2003 represented a period of significant
progress for our organization," stated Colin Goddard, Ph.D., Chief Executive
Officer of the Company. "On the Tarceva(TM) front we completed accrual to our
second- /third-line non-small cell lung cancer and

our front-line pancreatic cancer Phase III studies. We anticipate top-line
data for this lung study at the end of the calendar year. We believe
that successfully meeting the study's survival end-point would give us,
and our alliance partners, Genentech and Roche, a very competitive
position in the monotherapy setting for this exciting new class of
anti-cancer treatments. Meanwhile, the Novantrone(R) deal with Serono has given
us a quality anti-cancer drug around which to begin strategically building a
full commercial organization and closing the pending transaction with Cell
Pathways will give us both a second marketed product in Gelclair(TM) and
supplement our R&D pipeline, with an intriguing platform of pro-apoptotic drug
candidates. Taken together with the potential success for Tarceva(TM) and the
progress of our overall pipeline, we believe these transactions will help to
transform OSI into one of the leading oncology franchises in the industry."

For the second quarter and six months ended March 31, 2003, revenues were $7.6
million and $12.0 million, respectively, compared to revenues of $6.8 million
and $12.7 million for the prior year periods. The increase in the second quarter
reflects both the final payment received pursuant to the wind down of our
collaboration with Anaderm as well as the recognition of approximately $900,000
of commissions on U.S. oncology sales of Novantrone(R). These sales commissions
relate to the Company's co-promotion agreement with Serono, which became
effective March 11, 2003, and represent the estimated commissions earned through
the end of March. Operating expenses for the second quarter and six-month period
ended March 31, 2003 were $35.1 million and $70.9 million, respectively,
compared to $33.1 million and $56.5 million (excluding the in-process research
and development charge recorded in the prior year six month period) in the prior
year periods. The increases in operating expenses primarily reflect increased
Tarceva(TM) clinical costs as all four Phase III trials are now fully enrolled
and increased commercialization and marketing costs associated with Tarceva(TM)
and Novantrone(R).

CORPORATE HIGHLIGHTS
- ---------------------
The Company achieved several key corporate goals this quarter. These goals
included: gaining access to a high-quality, marketed oncology product,
Novantrone(R) (mitoxantrone for injection concentrate); the pending expansion of
OSI's anti-cancer platform by the signing of a merger agreement whereby the
Company has agreed to acquire Cell Pathways, Inc., including its apoptosis
technology and clinical candidates, and the marketed cancer care product
Gelclair(TM); and the appointment of Robert A. Ingram as Chairman of the Board.

In January 2003, OSI announced the appointment of Mr. Robert Ingram as Chairman
of the Board of Directors. Mr. Ingram recently retired as Chief Operating
Officer and President of Pharmaceutical Operations at GlaxoSmithKline and is the
current Vice Chairman, Pharmaceutials at GlaxoSmithKline. Mr. Ingram's long and
successful career in the pharmaceutical industry provides OSI with a tremendous
resource of experience and knowledge in helping guide the Company's next stage
of growth in the commercial arena.

In February 2003 OSI entered into a merger agreement whereby it has agreed to
acquire Cell Pathways which will add to the Company's commercial presence and
expanding pipeline in oncology. The transaction is subject to Pathway's
shareholder approval and a shareholder meeting has been scheduled for June 10,
2003 to consider the unanimous recommendation by

Cell Pathways' Board of Directors to approve the merger.

The transaction will add Cell Pathways' innovative platform approach to the
discovery and development of small molecule drugs designed to selectively induce
apoptosis, or programmed cell death, in pre-cancerous and cancerous cells,
including Cell Pathways' two leading clinical candidates, Aptosyn(R) and CP461,
and the marketed product Gelclair(TM), a bioadherent oral gel that provides
rapid and durable oral pain management, to the OSI portfolio. This transaction
is a stock-for-stock merger valued at approximately $32 million based on the
closing price of the Company's stock on February 7, 2003. Upon closing of the
transaction, the Company will exchange one share of Cell Pathways' common stock
for .0567 shares of the Company's common stock. In addition, Cell Pathways'
shareholders will also receive additional consideration in the form of a
five-year contingent value right through which each share of Cell Pathways'
common stock may be eligible for an additional .040 shares of the Company's
common stock in the event of a filing of a New Drug Application for either
Aptosyn(R) or CP461.

In March 2003, OSI entered into an agreement by which OSI will market and
promote the drug Novantrone(R) for the approved oncology indications in the
United States. In consideration for these exclusive rights, OSI paid Serono S.A.
initial fees totaling $55 million and pays maintenance fees in return for
commissions on net sales in oncology. OSI has begun building a commercial
operation, including a sales force and an associated marketing and management
infrastructure. The transaction allows OSI to deliver on the strategic goal of
building a full commercial operation around a quality product. The Company
projects sale commissions to be between $20 - $30 million in fiscal 2004, which
will off-set maintenance fees and the costs of the initial commercial operation
in a manner that the Company projects will allow this strategic investment to be
cash flow positive from 2004 onwards.

TARCEVA(TM) HIGHLIGHTS
- ----------------------
The Company made steady progress in its Tarceva(TM) (erlotinib HCl)
program in all three main disease settings, non-small cell lung, pancreatic
cancer and glioblastoma. Tarceva(TM) is a small molecule HER1/EGFR inhibitor
being developed through a tripartite alliance between OSI, Genentech, Inc. and
Roche.

In January 2003, OSI, in collaboration with the National Cancer Institute of
Canada Clinical Trials Group (NCIC CTG), reached its target enrollment goal of
700 patients in the international Phase III clinical trial evaluating
Tarceva(TM) as a monotherapy for the treatment of second-/third-line patients
with incurable stage IIIB/IV non-small cell lung cancer (NSCLC) for whom the
standard chemotherapy has failed. The FDA designated Tarceva(TM) a Fast Track
Product in this indication earlier in September 2002. As the only ongoing single
agent, randomized placebo-controlled study of an HER1/EGFR targeted agent
designed to detect a survival advantage in advanced NSCLC, this study remains
OSI's highest clinical priority.

In January 2003, OSI announced that the international Phase III clinical trial
evaluating Tarceva(TM) in combination with gemcitabine in patients with
advanced, previously untreated pancreatic cancer had reached its target
enrollment of 450 patients. This Phase III randomized,

placebo-controlled study with improvement in patient survival as its primary
end-point, is also being conducted in collaboration with the NCIC CTG.

In April, 2003, based on data from a Phase I study in glioblastoma,
a decision was made to continue with a comprehensive Phase II program for
this indication. The data from glioblastoma have been submitted to this
year's American Society of Clinical Oncology Meeting (ASCO) to be held May 31 -
June 3, 2003 in Chicago, IL. In addition, multiple Tarceva(TM) abstracts
have been submitted to ASCO including data on the correlation of rash with
survival.

CONFERENCE CALL
- ---------------
The Company will host a conference call reviewing the Company's second quarter
financial results for the period ended March 31, 2003, product portfolio and
recent business developments. The call is scheduled for tomorrow, May 15, 2003,
at 10:00 A.M. Eastern Time. To access the live call or the seven-day archive via
the Internet, log on to www.osip.com. Please connect to the Company's website at
least 15 minutes prior to the conference call to ensure adequate time for any
software download that may be needed to view the webcast. Alternatively, please
call 1-800-915-4836 (U.S.) or 1-973-317-5319 (international) to listen to the
call. Telephone replay is available approximately two hours after the call
through May 22, 2003. To access the replay, please call 1-800-428-6051 (U.S.) or
1-973-709-2089 (international). The conference ID number is 291945.

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. OSI has a balanced pipeline of oncology drug candidates that
includes both next-generation cytotoxic agents and novel mechanism-based,
gene-targeted therapeutics focused in the areas of signal transduction and
apoptosis. The Company's most advanced drug candidate, Tarceva(TM) (erlotinib
HCl), a small-molecule inhibitor of the HER1 gene, is currently in Phase III
clinical trials for lung and pancreatic cancers. OSI's oncology product
portfolio includes Novantrone(R) (mitoxantrone concentrate for injection), a
U.S. FDA approved treatment of acute nonlymphocytic leukemia and the relief of
pain associated with advanced hormone-refractory prostate cancer.

This news release contains forward-looking statements. 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 completion
of clinical trials, the FDA review process and other governmental regulation,
pharmaceutical collaborators' ability to successfully develop and commercialize
drug candidates, competition from other pharmaceutical companies, and other
factors described in OSI Pharmaceuticals' filings with the Securities and
Exchange Commission. Tarceva(TM) (erlotinib HCl) is an investigational compound
and has not yet been determined safe or efficacious in humans for its ultimate
intended use.

Additional Information About the Merger and Where to Find It

In connection with the proposed merger referred to above, OSI Pharmaceuticals
has filed with the Securities and Exchange Commission (SEC) a registration
statement on Form S-4. The registration statement has been declared effective,
and it contains the proxy statement of Cell Pathways for the meeting of its
stockholders scheduled for June 10, 2003 to consider and vote upon the proposed
merger. The proxy statement also serves as a prospectus of OSI Pharmaceuticals
with respect to the shares of OSI Pharmaceuticals to be distributed to
stockholders of Cell Pathways in the proposed transaction. INVESTORS AND
SECURITY HOLDERS ARE URGED TO CAREFULLY READ THE PROXY STATEMENT/PROSPECTUS
REGARDING THE PROPOSED MERGER TRANSACTION 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 may obtain a free copy of the proxy
statement/prospectus and other documents filed by OSI Pharmaceuticals and Cell
Pathways at the SEC's web site at http://www.sec.gov. In addition, they may
obtain such documents from OSI Pharmaceuticals 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 Pharmaceuticals' or Cell Pathways' directors and executive
officers have in the proposed merger is available in the proxy
statement/prospectus.

This press release is not an offer to sell shares of OSI Pharmaceuticals common
stock which may be issued in the proposed merger with Cell Pathways. Such OSI
Pharmaceuticals common stock is offered only by means of the proxy
statement/prospectus referred to herein.

# # #

OSI PHARMACEUTICALS, INC. AND SUBSIDIARIES
SELECTED FINANCIAL INFORMATION
CONSOLIDATED STATEMENTS OF OPERATIONS
(UNAUDITED)

<Table>
<Caption>
(IN THOUSANDS, EXCEPT PER SHARE DATA)

THREE MONTHS ENDED MARCH SIX MONTHS ENDED MARCH
31, 31,
-------------------------- -----------------------
2003 2002 2003 2002
--------- ---- ---- ----

Revenues:
Sales commissions......................... $ 887 $ -- $ 887 $ --
Collaborative program revenues............ 5,236 4,041 8,218 7,157
License and other revenues................ 1,469 2,729 2,959 5,505
-------- -------- -------- ---------
Total revenues............................ 7,592 6,770 12,064 12,662
-------- -------- -------- ---------
Expenses:
Research and development.................. 23,773 26,525 51,996 43,779
Acquired in-process research and
development............................. -- -- -- 130,200
Selling, general and administrative....... 10,660 6,272 18,160 12,128
Amortization of intangibles............... 690 306 744 615
-------- -------- -------- ---------
Total expenses............................ 35,123 33,103 70,900 186,722
-------- -------- -------- ---------
Loss from operations...................... $(27,531) $(26,333) $(58,836) (174,060)
Other income (expense):
Investment income -- net.................. 2,233 3,465 4,902 8,039
Interest expense.......................... (1,605) (1,346) (3,212) (1,348)
Other expense -- net...................... (266) (301) (123) 472
-------- -------- -------- ---------
Net loss.................................. $(27,169) $(24,515) $(57,269) $(166,897)
Basic and diluted net loss per common
share................................... $ (0.75) $ (0.68) $ (1.57) $ (4.68)
======== ======== ======== =========
Weighted average shares of common stock
outstanding............................. 36,448 36,147 36,431 35,637
======== ======== ======== =========

CONDENSED CONSOLIDATED BALANCE SHEET(IN THOUSANDS)
<Caption>
MARCH 31, SEPTEMBER 30,

2003 2002
--------- -------------
(UNAUDITED)

Cash and investments...................... $362,370 $476,277
======== ========
Total assets.............................. $521,341 $579,044
======== ========
Total stockholders' equity................ $321,998 $379,108
======== ========
</Table>