8-K

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 8-K

                CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

                                 March 22, 2005

                             ----------------------
                Date of Report (Date of earliest event reported)

                            OSI PHARMACEUTICALS, INC.
                            -------------------------
             (Exact name of registrant as specified in its charter)

          DELAWARE                    0-15190                    13-3159796
     ------------------              ---------                 --------------
(State or other jurisdiction of     (Commission              (I.R.S. Employer
        incorporation)              File Number)             Identification No.)

                              58 SOUTH SERVICE ROAD
                               MELVILLE, NY 11747
                    ----------------------------------------
                    (Address of principal executive offices)

                                 (631)962-2000
                            --------------------------
              (Registrant's telephone number, including area code)

                                      N/A
                                -----------------
                        (Former name or former address,
                         if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions:

[ ]   Written communications pursuant to Rule 425 under the Securities Act (17
      CFR 230.425)

[ ]   Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17
      CFR 240.14a- 12)

[ ]   Pre-commencement communications pursuant to Rule 14d-2(b) under the
      Exchange Act (17 CFR 240.14d-2(b))

[ ]   Pre-commencement communications pursuant to Rule 13e-4(c) under the
      Exchange Act (17 CFR 240.13e-4(c))


ITEM 8.01 OTHER EVENTS

      On March 22, 2005, OSI Pharmaceuticals, Inc. (the "Company") issued a
press release relating to the approval of Tarceva(TM) by the Swiss health
authority, Swissmedic, for patients with advanced non-small cell lung cancer.
The Company's press release is attached as Exhibit 99.1 to this Current Report
on Form 8-K and is incorporated herein by reference.

ITEM 9.01 EXHIBITS



 EXHIBIT NO.                      DESCRIPTION
 -----------                      -----------
                  
    99.1             Press release, dated March 22, 2005.


                                       2


                                    SIGNATURE

      Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

      Date: March 29, 2005                             OSI PHARMACEUTICALS, INC.

                                       By: /s/ Robert L. Van Nostrand
                                           -------------------------------------
                                           Robert L. Van Nostrand
                                           Vice President and Chief Financial
                                           Officer (Principal Financial Officer)

                                       3


                                 EXHIBIT INDEX



EXHIBIT NO.                       DESCRIPTION
- -----------                       -----------
                  
    99.1             Press release, dated March 22, 2005.


                                       4

EX-99.1

                                                                    EXHIBIT 99.1

[OSI PHARMACEUTICALS LOGO]

                                                                    NEWS RELEASE

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

              OSI PHARMACEUTICALS ANNOUNCES TARCEVA GRANTED FIRST
                        EUROPEAN APPROVAL IN SWITZERLAND

   - FIRST AND ONLY AGENT APPROVED IN ITS CLASS TO SHOW A SURVIVAL BENEFIT -

MELVILLE, NEW YORK - MARCH 22, 2005 -- OSI Pharmaceuticals, Inc. (NASDAQ: OSIP)
announced today that the Swiss health authority, Swissmedic, has approved
Tarceva(TM) (erlotinib) for the treatment of patients with locally advanced or
metastatic non-small cell lung cancer (NSCLC) after failure of at least one
prior chemotherapy regimen. Tarceva is an oral tablet indicated for daily
administration. Tarceva is the only drug in the epidermal growth factor receptor
(EGFR) class to demonstrate in a Phase III clinical trial an increase in
survival in advanced NSCLC patients.

"Tarceva offers new hope to people who are suffering from this lung cancer,"
said William M. Burns, CEO of Roche's Pharmaceuticals Division. "Tarceva is the
first medicine in its class with a proven survival and without some of the
unpleasant side effects of chemotherapy."

"We would like to congratulate our colleagues at Roche on the first European
approval of Tarceva," stated Colin Goddard, Ph.D., Chief Executive Officer of
OSI Pharmaceuticals. "We are pleased with the launch of Tarceva in the U.S. to
date and we continue to believe that Tarceva will emerge as a fundamentally
important new agent in changing the paradigm for the treatment of cancer
patients around the world. With our partners, Genentech and Roche, we are
committed to executing a post-approval development plan, studying Tarceva in
earlier stage lung cancer patients, in patients with other tumor types and
combinations with other targeted therapies."

As with the U.S. label, Tarceva is indicated for all NSCLC patients after
failure of at least one

                                       5


prior chemotherapy regimen and contains no restrictions on its use regarding
EGFR status, mutation status, gender, smoking history, histology or ethnicity.
OSI was responsible for the U.S. filing of Tarceva in advanced NSCLC which
received U.S. FDA approval in November 2004. In addition, a Marketing
Authorization Application was submitted by Roche to the European Health
Authorities in August 2004.

The Swiss health authority's decision to approve Tarceva was based on the
pivotal BR.21 study in 731 patients with advanced NSCLC. Tarceva demonstrated a
survival benefit in essentially all subsets of patients examined including males
and females, patients of Asian and non-Asian origins, patients with
adenocarcinoma and squamous cell histology, patients with good as well as
impaired performance status and both smokers and non-smokers. Median and
one-year survival of the overall population in the BR.21 study was improved by
42.5 (6.7 versus 4.7 months) and 45 percent (31.2 versus 21.5 percent),
respectively, and patients were treated with Tarceva for an average of just over
four months in the study (23% of patients were on therapy for more than 6
months). Certain subsets of patients, including never smokers and patients who
had tumors determined to be EGFR positive, were seen to have a large survival
benefit in response to treatment with Tarceva. The sub-group of patients who
never smoked had a substantial survival benefit with a hazard ratio of 0.42
(hazard ratio is a measure of the risk of death and a hazard ratio of <1
indicates a survival benefit). The sub-group of smokers also had a survival
benefit (hazard ratio = 0.87) despite the fact that this group was also seen to
have a 24 percent higher rate of Tarceva clearance (higher clearance rates lead
to lower levels of exposure to drug).

In the pivotal NSCLC trial, the most common adverse reactions in patients
receiving Tarceva were rash and diarrhea. Grade three/four rash and diarrhea
occurred in nine and six percent of Tarceva-treated patients, respectively. Rash
and diarrhea each resulted in discontinuation of one percent of Tarceva-treated
patients. Six and one percent of patients needed dose reduction for rash and
diarrhea, respectively. Historically, there have been infrequent reports of
serious interstitial lung disease (ILD), including fatalities, in patients
receiving Tarceva for treatment of NSCLC or other advanced solid tumors. In the
Phase III trial, severe pulmonary reactions, including potential cases of
interstitial lung disease, were infrequent (0.8 percent) and were equally
distributed between treatment arms. The overall incidence of ILD in
Tarceva-treated patients from all studies was approximately 0.6 percent.

Results from two earlier large, randomized, placebo-controlled clinical trials
in first-line advanced NSCLC patients showed no clinical benefit with concurrent
administration of Tarceva with doublet platinum-based chemotherapy (carboplatin
and paclitaxel or gemcitabine and cisplatin) and its use is not recommended in
that setting.

ABOUT TARCEVA

Tarceva is a small molecule designed to target the human epidermal growth factor
receptor 1 (HER1) pathway, which is one of the factors critical to cell growth
in NSCLC. HER1, also known as EGFR, is a component of the HER signaling pathway,
which plays a role in the formation and growth of numerous cancers. Tarceva is
designed to inhibit the tyrosine kinase activity of the HER1 signaling pathway
inside the cell, which may block tumor cell growth. A Phase III clinical trial
of Tarceva has been completed in pancreatic cancer, and additional early-stage
trials of Tarceva are being conducted in other solid tumors. Tarceva is
currently being

                                       6


evaluated in an extensive clinical program by a global alliance among OSI
Pharmaceuticals, Genentech and Roche.

ABOUT LUNG CANCER

According to the World Health Organization, there are more than 1.2 million
cases worldwide of lung and bronchial cancer each year, causing approximately
1.1 million deaths annually. It is estimated that more than 173,000 people will
be diagnosed with lung cancer in the United States in 2004. According to the
National Cancer Institute, lung cancer is the single largest cause of cancer
deaths in the United States and is responsible for nearly 30 percent of cancer
deaths in this country. NSCLC is the most common form of the disease and
accounts for almost 80 percent of all lung cancers.

ABOUT OSI PHARMACEUTICALS

OSI Pharmaceuticals is a leading biotechnology company primarily focused on the
discovery, development and commercialization of high-quality pharmaceutical
products that extend life or improve the quality of life for cancer and diabetes
patients worldwide. OSI's primary business remains oncology, but the Company has
a second business interest in the area of diabetes through its Prosidion
subsidiary based in the United Kingdom. Tarceva(TM), OSI's flagship product, is
the first OSI drug discovered and developed by OSI to obtain FDA approval and
the only EGFR inhibitor to have demonstrated the ability to improve survival in
non-small cell lung cancer and pancreatic cancer. OSI exclusively markets
Novantrone(R) (mitoxantrone concentrate for injection) for the approved oncology
indications and markets Gelclair(R) for the relief of pain associated with oral
mucositis.

                                      ###

                                       7