EXHIBIT 10.4

                        [OSI PHARMACEUTICALS LETTERHEAD]

                          ADDENDUM TO EMPLOYMENT OFFER
                                FOR BARBARA WOOD

                           CHANGE OF CONTROL AGREEMENT

This Agreement dated, October 4, 2001, between OSI Pharmaceuticals and Barbara
Wood:

In the event OSI is sold or merged with another Company resulting in a change of
control (CHANGE OF CONTROL), and your employment with the Controlling Company is
terminated (including if you voluntarily terminate your employment for "Good
reason"*) at any time within six (6) months following a CHANGE OF CONTROL
transaction, unless such termination is for "cause", death, disability or you
voluntarily leave without "Good Reason", you will be entitled to receive the
benefits described below.

      1. In lieu of any further salary and bonus payments to you for periods
subsequent to the date of termination, the Controlling Company shall pay you the
following benefits:

            (a) A lump sum severance payment equal to your annual salary for a
period of twelve (12) months; and,

            (b) All unpaid, accrued vacation through the date of termination.

      2. After the termination, the Controlling Company shall arrange to provide
you and your dependents, as may be the case, with health benefits substantially
similar to those which you and your dependents were receiving immediately prior
to the sale or Change of Control and up to one (1) years after the sale or
Change of Control.

*Good Reason for termination of employment includes (i) a decrease in your total
compensation package, (ii) the assignment of duties or responsibilities which
are not commensurate with your position immediately prior to the sale or Change
of Control, or (iii) you are required to relocate to an office or facility more
than forty (40) miles from your present location or forty (40) miles from your
home.

OSI Pharmaceuticals, Inc.

By:  /s/ COLIN GODDARD                       /s/ BARBARA WOOD
     -------------------------------         -----------------------------------
         Colin Goddard                       Barbara Wood
         CEO and Chairman