EXHIBIT 99.1

[OSI PHARMACEUTICALS LOGO]

OSI - INVESTOR INFORMATION

OSI Pharmaceuticals, Inc. (ticker: OSIP, exchange: NASDAQ) News Release -
28-Jan-2004

OSI PHARMACEUTICALS ANNOUNCES FIRST QUARTER FINANCIAL RESULTS; CONFERENCE CALL
AND WEBCAST TO FOLLOW

MELVILLE, N.Y.--(BUSINESS WIRE)--Jan. 28, 2004--OSI Pharmaceuticals, Inc.
(NASDAQ: OSIP) today announced its financial results for the Company's first
quarter ended December 31, 2003. The Company reported a net loss of $40.1
million (or $1.03 per share) for the first quarter of 2004, compared with the
net loss of $30.1 million (or $0.83 per share) in the prior year period.
Revenues for the quarter were $11.4 million, an increase of $6.9 million or 155%
compared to the three months ended December 31, 2002. Sales commissions and
product sales of approximately $10.1 million drove this increase in revenues.

Contributing to the increase in net loss was an increase in operating expenses
of $14.1 million or 39%. This increase in operating expenses was partially
attributed to increased selling, general and administrative expenses related to
Novantrone(R) and Gelclair(R), the associated expansion of the Company's
commercial operation and increased commercialization and marketing costs
relating to Tarceva(TM). Amortization expense also increased by $4.8 million
relating to the marketing rights for Novantrone(R) and Gelclair(R). Also
contributing to the increase in the net loss for the period was an increase in
other expense associated with the interest on convertible notes the Company
issued in September 2003, as well as a decrease in the rate of return on
investments. These increases were partially offset by a reduction in clinical
development cost. While there are multiple on-going clinical trials for
Tarceva(TM), the large-scale Phase III trials are completed or nearing
completion; all four Phase III trials were fully active in the same period a
year ago.

Product and Portfolio Highlights

Tarceva(TM)

Tarceva(TM), OSI's leading drug candidate, is designed to block tumor cell
growth by inhibiting the tyrosine kinase activity of the HER1/EGFR receptor
thereby blocking the HER1/EGFR signaling pathway inside the cell. Tarceva(TM) is
currently being evaluated in an extensive clinical development program together
with the Company's alliance partners, Genentech and Roche.

The principal registration study is a worldwide Phase III trial testing
monotherapy Tarceva(TM) versus placebo in a relapsed non-small cell lung cancer
(NSCLC) setting. In 2002, OSI was granted Fast Track status from the U.S. Food
and Drug Administration (FDA) for this indication. Therefore the Company
recently announced that it had initiated a "rolling" submission of an New Drug
Application (NDA) with the FDA. The primary endpoint in the study is improvement
in patient survival and key secondary endpoints include time to symptomatic
deterioration, progression-free survival and response rate. Top-line data are
expected in the second quarter


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calendar year (CY) 2004. Based upon this time-line and assuming success, the
Company would expect to complete an NDA filing by approximately CY2Q/3Q 2004 and
would project a possible approval (assuming a six month review) by the FDA late
in the fourth quarter of CY2004 or in the first quarter of CY2005.

In November, OSI announced it had initiated a Phase II dose-escalation study of
Tarceva(TM) in patients with advanced NSCLC who have failed prior chemotherapy.
The study is designed to evaluate the feasibility of dose escalation of
Tarceva(TM) to safely induce tolerable rash and to assess whether there is some
evidence of enhanced activity in patients who develop rash. Data previously
reported from the completed Phase II studies of Tarceva(TM) suggested that
patients who developed rash survived longer than those who did not experience
rash.

In November, a series of on-going Phase II studies on monotherapy Tarceva(TM) in
different tumor types were presented at the 2003 AACR-NCI-EORTC International
Conference on Molecular Targets and Cancer Therapies in Boston, MA. Partial
responses and disease stabilization were observed in studies of hepatocellular
carcinoma, metastatic endometrial cancer and metastatic biliary carcinoma. As in
previous monotherapy studies with Tarceva(TM) a reversible rash and generally
mild diarrhea were the principal side effects noted. These observations further
support the notion that Tarceva(TM) may demonstrate broad-based anti-tumor
activity in a wide variety of solid tumor types.

Marketed Products: Novantrone(R) & Gelclair(R)

At the American Society of Hematology 45th Annual Meeting in San Diego, CA held
in December 2003, over 100 abstracts for studies involving Novantrone(R) were
published and 12 of these were selected for discussion during the meeting's oral
presentation sessions. Among the highlighted findings presented at the
conference were encouraging preliminary data on the combination use of
Novantrone(R) and fludarabine-containing regimens with rituximab (Rituxan(R)) in
certain lymphoma.

The Company's second marketed product, Gelclair(R), was launched in the last
quarter of CY2003 and the Company estimates that the product has the potential
to grow to a revenue stream in excess of $25 million per year within five years
from launch. Gelclair(R) is a bioadherent oral gel indicated for the management
and relief of pain often associated with oral mucositis. An estimated 300,000
cancer patients in the United States suffer from oral mucositis, an inflammation
and ulceration of the surface of the mouth and throat commonly associated with
cancer treatments.

Additional Portfolio Highlights

OSI-7904L

In October, OSI announced that it had advanced the development of OSI-7904L, a
liposomal formulation of a potent thymidylate synthase inhibitor, by initiating
a Phase II clinical study in patients with previously untreated advanced gastric
or gastro esophageal junction cancer. Data from this Phase II study are
anticipated in the fourth quarter of CY2004. In addition, OSI previously
announced it had broadened the OSI-7904L development program by initiating two


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additional studies evaluating the use of OSI-7904L in combination with the
chemotherapy agents cisplatin and oxaliplatin commonly used in the treatment of
gastrointestinal malignancies.

Aptosyn(R)

Aptosyn(R) is currently in a Phase III clinical trial comparing a combination of
Aptosyn(R) and Taxotere(R) versus Taxotere(R) and placebo in second-line NSCLC.
The 610-patient trial was based primarily on pre-clinical data and enrollment
was completed prior to the completion of OSI's acquisition of Cell Pathways in
June 2003. Based on the absence of clinical data in NSCLC and the lack of
potency exhibited by Aptosyn(R) in pre-clinical model systems, the Company is
not optimistic of a positive outcome for the preliminary survival endpoint in
this study. The Company anticipates top-line data from this study to be
available in the second half of CY2004. Additionally, there are nine
investigator sponsored trials on-going in a variety of solid tumors including
prostate, lung, breast and colorectal. Enrollment is on-going in these studies
and we anticipate that several abstracts from this program will be presented at
this year's Annual Meeting of the American Society of Clinical Oncology.

OSI-461

OSI-461 is more potent in preclinical models and a promising second-generation
follow-on candidate to Aptosyn(R). OSI-461 is currently being evaluated for a
series of preliminary Phase II studies in chronic lymphocytic leukemia, renal
cell carcinoma and prostate cancer. The Company is also seeking to further
optimize dose in an expanded dose ranging Phase I study. Data from this study
are expected in the fourth quarter of CY2004. In addition, data from the Phase
II study of OSI-461 in patients with moderate to severe Crohn's disease are
anticipated in mid-CY2004.

Research

The Company advanced its proprietary c-kit/KDR dual inhibitor, OSI-930, to IND
(Investigational New Drug)-track status of development. C-kit and KDR are both
receptor tyrosine kinases which function as key regulators in the control of
tumor growth and angiogenesis. The Company anticipates filing an IND with the
FDA by year-end of CY2004.

Conference Call

The Company will host a conference call reviewing the Company's year-end
financial results, product portfolio and business developments on January 29,
2004 at 10:00am (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 access 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 February 5, 2004. To access the
replay, please call 1-800-428-6051 (U.S.) or 1-973-709-2089 (international). The
conference ID number is 333619.


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About OSI Pharmaceuticals

OSI Pharmaceuticals is a leading biotechnology company focused on the discovery,
development and commercialization of high-quality, next-generation oncology
products that both extend life and improve the quality-of-life for cancer
patients worldwide. OSI has a balanced pipeline of oncology drug candidates that
includes both novel mechanism-based, gene-targeted therapies focused in the
areas of signal transduction and apoptosis and next-generation cytotoxic
chemotherapy agents. OSI's most advanced drug candidate, Tarceva(TM), a
small-molecule inhibitor of the HER1 gene, is currently in Phase III clinical
trials for lung and pancreatic cancers. OSI has a commercial presence in the
U.S. oncology market where it exclusively markets Novantrone(R) (mitoxantrone
concentrate for injection) for approved oncology indications and Gelclair(R) for
the relief of pain associated with oral mucositis.

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 successful
marketing of products, product pricing and third-party reimbursement, the
completion of clinical trials, the FDA review process and other governmental
regulation, OSI's and its collaborators' abilities 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), OSI-7904L, OSI-461, Aptosyn(R) and OSI-930
are investigational compounds and have not yet been determined safe or
efficacious in humans for their ultimate intended use.

CONTACT:
OSI Pharmaceuticals, Inc.
Investor & Public Relations:
Kathy Galante, 631-962-2000
or
Burns McClellan (representing OSI)
Kathy Jones, Ph.D. (media)
E. Blair Schoeb (investors)
212-213-0006

SOURCE: OSI Pharmaceuticals, Inc.


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OSI Pharmaceuticals, Inc. and Subsidiaries
Selected Financial Information



Consolidated Statements of Operations                             Three Months Ended
                                                                     December 31,
                                                             ---------------------------
                                                               2003               2002
                                                             --------           --------
                                                         (In Thousands, except per share data)
                                                                     (Unaudited)
                                                                          
Revenues:
      Sales commissions and product sales ............       $ 10,141           $     --
      License and other revenues .....................          1,250              1,490
      Collaborative program revenues .................             --              2,982
                                                             --------           --------
         Total revenues ..............................         11,391              4,472
                                                             --------           --------
Expenses:
      Cost of product sales ..........................            110                 --
      Research and development .......................         24,105             28,223
      Selling, general and administrative ............         20,820              7,500
      Amortization of intangibles ....................          4,838                 54
                                                             --------           --------
            Total expenses ...........................         49,873             35,777
                                                             --------           --------
            Loss from operations .....................       $(38,482)          $(31,305)

Other income (expense):
      Investment income - net ........................          1,487              2,669
      Interest expense ...............................         (2,820)            (1,607)
      Other income (expense) - net ...................           (318)               143
                                                             --------           --------
Net loss .............................................       $(40,133)          $(30,100)
                                                             ========           ========
Basic and diluted net loss per common share ..........       $  (1.03)          $  (0.83)
                                                             ========           ========
Weighted average shares of common stock outstanding...         38,884             36,414
                                                             ========           ========




Condensed Consolidated Balance Sheet       December 31      September 30
                                              2003              2002
                                            --------          --------
                                                 (In Thousands)
                                                   (unaudited)
                                                      
Cash and investments securities
(including restricted investments)...       $378,754          $404,147
                                            ========          ========
Total assets ........................       $556,395          $591,502
                                            ========          ========
Total stockholders' equity ...........      $179,972          $218,057
                                            ========          ========



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