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                      SECOND AMENDMENT TO SUPPLY AGREEMENT

         THIS SECOND AMENDMENT ("Second Amendment") is entered into as of the
20th day of June, 2000 (the "Effective Date") by and between DUSA
PHARMACEUTICALS, INC. ("DUSA"), a corporation organized and existing under the
laws of the State of New Jersey, USA, whose principal offices are at 25 Upton
Drive, Wilmington, Massachusetts, 01887, U.S.A., and SOCHINAZ S.A. ("SOCHINAZ"),
a corporation registered under the laws of the Canton of Valais, Switzerland,
whose principal offices are at 22, rte du Simplon, CH-1895 Vionnaz, Switzerland.

         WHEREAS, DUSA and SOCHINAZ entered into a Supply Agreement, dated
December 24, 1993, which was amended pursuant to the First Amendment to Supply
Agreement, dated July 7, 1994 (collectively the "Agreement"), pursuant to which
SOCHINAZ sells to DUSA and DUSA purchases from SOCHINAZ, a porphyrin precursor
generally known as 5-aminolevulinic acid ("ALA") meeting certain specifications
(the "Product"); and

         WHEREAS, pursuant to the Agreement, SOCHINAZ is required to manufacture
the Product in accordance with the current Good Manufacturing Practices ("cGMP")
established by the United States Food and Drug Administration (the "FDA"); and

         WHEREAS, DUSA believes that in consideration of the parties agreement
to amend the terms and conditions of the Agreement for the purpose of providing
DUSA with an option to renew the Agreement after the expiration of the Term
specified in the Agreement and to correct certain typographical and clerical
errors contained within the Agreement, and it is in its best interests of both
parties to reimburse SOCHINAZ for a portion of the costs SOCHINAZ incurred to
bring its manufacturing facility into compliance with cGMP, under the terms of
this Second Amendment.

         NOW, THEREFORE, in consideration of the foregoing, and other good and
valuable consideration, the receipt and sufficiency of which the parties
acknowledge, the parties hereby agree as follows:

         1.       DUSA shall pay to SOCHINAZ an aggregate of $1.0 Million U.S.
Dollars, as follows:

                  (a)   $250,000 in cash, by wire transfer of immediately
                        available funds to Credit Suisse - CH - 1870  Monthey /
                        Account No.: 192649-42-780 / SWIFT CRESCHZZ18L; and


                  (b)   DUSA shall issue to SOCHINAZ that number of shares of
                        DUSA common stock, no par value, (hereinafter
                        referred to as the "Shares") having, as of the
                        Effective Date, a fair market value of $750,000, the
                        actual number of Shares and the terms and conditions
                        of such issuance to be set forth in a certain Stock
                        Subscription Agreement being entered into by the
                        parties contemporaneously with the signing of this
                        Second Amendment.


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         2.       Sections 2.3, 2.4 and 2.5 of the Agreement, which currently
begin "Notwithstanding Paragraph 2.2 above...", shall be amended to correctly
refer to Paragraph 2.1, as follows: "Notwithstanding Paragraph 2.1 above..."

         3.       Section 6.2 of the Agreement, which in relevant part
currently states " ... SOCHINAZ is unable to supply DUSA's requirement of
Products. Products hereunder in which case DUSA...", shall be amended, deleting
the repetition of the word Products, as follows: " ... SOCHINAZ is unable to
supply DUSA's requirement of Products hereunder in which case DUSA...".

         4.       Section 9.1 shall be amended to state as follows: "This
Agreement shall have an initial term of five (5) years from the date the
Product is first approved for any therapeutic use by the U.S. Food and Drug
Administration (i.e., December 3, 1999) unless sooner terminated in accordance
with Section 9.2 or 9.3 below. DUSA shall have an option to renew this
Agreement on the same terms and conditions for a period of three (3) additional
years, provided that DUSA notifies SOCHINAZ no later that June 3, 2003 of its
intention to renew this Agreement."

         5.       Except as expressly provided in this Amendment, the Agreement
shall remain unmodified and in full force and effect and is hereby ratified and
affirmed. The execution, delivery, and effectiveness of this Second Amendment
shall not, except as expressly provided herein, operate as a waiver of any
right, power, or remedy of DUSA or SOCHINAZ under the Agreement.

         IN WITNESS WHEREOF, the parties execute this Agreement.


SOCHINAZ S.A.                               DUSA PHARMACEUTICALS, INC.



By:   /s/ Christian A. Borgeaud             By:   /s/ D.Geoffrey Shulman, MD
      -------------------------             -----------------------------------
      Christian A. Borgeaud                 D. Geoffrey Shulman, MD, FRCPC
      Chief Executive Officer               President & Chief Executive Officer