AMENDMENT NO. 1 to the Collaborative Agreement dated as of April 19, 1995 between Novartis Pharma AG and OSI Pharmaceuticals, Inc.

   1


                                 AMENDMENT NO. 1

                         to the Collaborative Agreement
                           dated as of April 19, 1995
                         between Novartis Pharma AG and
                            OSI Pharmaceuticals, Inc.

Novartis Pharma AG of Xxxxxxxxxxxx 00, XX-0000 Xxxxx, Xxxxxxxxxxx and OSI
Pharmaceuticals, Inc., of 000 Xxxxxxx Xxxxxxxxx Xxxxxxxxx, Xxxxxxxxx, Xxx Xxxx
00000-0000, XXX agree to amend the above mentioned agreement (hereinafter
referred to as "1995 Agreement") as follows:

The four year time limit to exercise the option set forth in Section 5.7 of the
1995 Agreement will be extended until the end of May and such option right will
therefore not expire until May 31, 1999.

BASEL      April 13, 1999               UNIONDALE        April 13, 1999
      -------------------------                   ------------------------------

Novartis Pharma AG                      OSI Pharmaceuticals, Inc.

              /s/                     /s/                    /s/
Xx. X. Xxxxxxx                   X. Xxxxxxxxx             Xx. X. Xxxxxxx
Head Licensing Drug Delivery     Legal Counsel            Vice President,
& Out-Licensing                                           Business Development