RESEARCH COLLABORATION AND LICENSE AGREEMENT
This SECOND AMENDMENT TO RESEARCH COLLABORATION AND LICENSE
AGREEMENT (this “Second Amendment”) dated as of February 20, 2007 , is entered into by and between
Merck & Co., Inc. (“MERCK”) and ARENA PHARMACEUTICALS, INC., (“ARENA”) and amends that
certain Research Collaboration and License Agreement between MERCK and ARENA, effective as of
October 21, 2002, as subsequently amended by the First Amendment to the Research Collaboration and
License Agreement between MERCK and ARENA, dated October 20, 2004 (as so amended, the
MERCK and ARENA, for good and valuable consideration, the receipt and sufficiency of which are
hereby mutually acknowledged, and intending to be legally bound hereby, agree as follows:
1 DEFINITIONS AND GENERAL TERMS
1.1 All capitalized terms used and not defined in this Second Amendment shall have the meaning as set out
in the Agreement.
1.2 The term “Effective Date of this Second Amendment” shall be February 20, 2007.
1.3 Except as modified by this Second Amendment, the terms of the Agreement shall continue in full force
and effect without modification.
1.4 Notwithstanding anything else to the contrary in this Second Amendment, this Second Amendment
shall not be effective unless and until the transactions contemplated by the Common Stock Purchase Agreement
dated February 20, 2007, by and between MERCK and ARENA shall have closed.
2 AMENDMENTS TO THE AGREEMENT
As of the Effective Date of this Second Amendment, the Parties amend the Agreement as follows:
4.1 Section 2.2(e) of the Agreement is deleted in its entirety and replaced with the following:
“(e) From the second anniversary date of the Effective Date until February 20, 2007,
ARENA shall dedicate nineteen (19) FTEs to the Program to work directly and