FIRST AMENDMENT TO MERGER AGREEMENT
THIS FIRST AMENDMENT TO MERGER AGREEMENT (this "First Amendment") is made on the 6th day
of February, 2006, by and among DUSA Pharmaceuticals, Inc., a publicly traded pharmaceutical company
incorporated in the State of New Jersey, with principal offices at 25 Upton Drive, Wilmington, Massachusetts
("DUSA"), Sirius Laboratories, Inc., a privately held specialty pharmaceutical company incorporated in the State
of Illinois, with principal offices at 100 Fairway Drive, Suite 130, Vernon Hills, Illinois ("Sirius"), and those
shareholders of Sirius set forth on the signature pages hereto (each a "Principal Shareholder" and collectively the
"Principal Shareholders"). DUSA, Sirius and the Principal Shareholders are at times referred to each as a "Party"
and collectively as the "Parties." All capitalized terms used, but not specifically defined herein, shall have the
meaning provided for such terms in the Merger Agreement (as defined below).
R E C I T A L S
WHEREAS, the Parties entered into that certain Merger Agreement, dated December 30, 2005 (as the same
may be amended from time to time, the "Merger Agreement") whereby the Parties have agreed to effect a merger
of Sirius with and into a wholly-owned subsidiary of DUSA ("DUSA Sub"), resulting in DUSA Sub being the
surviving entity, the Sirius Shareholders receiving the consideration provided for therein, and DUSA owning all of
the issued and outstanding common stock of DUSA Sub; and
WHEREAS, the Parties wish to amend certain terms of the Merger Agreement in accordance with Section 15.8
of the Merger Agreement, as provided for herein.
NOW, THEREFORE, the Parties, in furtherance of the foregoing and for good and valuable consideration, the
receipt and adequacy of which are hereby acknowledged, intending to be legally bound, agree as follows:
1. The following is added as a new Section 1.50a:
1.50a "First Amendment" means the First Amendment to Merger Agreement between the Parties dated Februar