<PAGE>   1
                                                                   EXHIBIT 10(q)


                                SUPPLY AGREEMENT

     This Agreement is entered into the 24th day of December, 1993 by and
between DUSA Pharmaceuticals, Inc. (hereinafter, "DUSA"), a corporation
organized and existing under the laws of the State of New Jersey whose principal
offices are located at 337 Roncesvalles Avenue, Toronto, Ontario Canada MGR 2M7,
and Sochinaz S.A. (hereinafter, "SOCHINAZ"), a corporation registered under the
laws of the Canton of Valais, Switzerland whose principal offices are located at
Rte du Simplon, CH-1895 Vionnaz Switzerland.

                              W I T N E S S E T H:

     WHEREAS, DUSA is developing a porphyrin precursor generally known as
5-aminolevulinic acid (hereinafter "ALA"), which is useful as an active
ingredient in diagnosis and therapy; and

     WHEREAS, SOCHINAZ is an experienced manufacturer of ALA; and

     WHEREAS, DUSA needs a reliable supply of ALA and wishes to purchase ALA
from SOCHINAZ and SOCHINAZ wishes to sell ALA to DUSA for that purpose;

     NOW THEREFORE, in consideration of the foregoing and the mutual covenants
contained herein, the parties agree as follows:

     1.   Definitions. As used herein, the term

     1.1  "ALA" shall mean 5-aminolevulinic acid.

     1.2  "Product" or "Products" shall mean ALA meeting the specifications set
forth on Exhibit A, attached hereto and incorporated by reference herein, as
such specifications may be amended from time to time by DUSA.

     1.3  "Territory" shall mean the world.

     2.   Purchase and Sale of Products; Resale Restrictions.

     2.1  Subject to the terms of this Agreement, DUSA agrees to purchase from
SOCHINAZ, and SOCHINAZ agrees to sell to DUSA, all of DUSA's requirements for
Products for sale in the Territory, during the term of this Agreement.

     2.2  SOCHINAZ agrees not to manufacture, deal in or sell ALA for
pharmaceutical use, in or to any other party who to SOCHINAZ knowledge intends
to sell or resell the same for ultimate resale in the Territory. SOCHINAZ may
sell ALA for other uses with the prior written consent of DUSA.

<PAGE>   2

     2.3  Notwithstanding Paragraph 2.2 above, DUSA shall have the right to
secure an alternate supplier for [c.i.] of DUSA's requirements.

     2.4  Notwithstanding Paragraph 2.2 above, DUSA shall have the right to
purchase any or all of DUSA's requirements for Product from third parties in the
event SOCHINAZ is unable to supply in a timely manner all Products ordered in
three consecutive purchase orders, whether or not such orders are in excess of
DUSA's forecasts.

     2.5  Notwithstanding Paragraph 2.2 above, DUSA shall have the right to
purchase Product from third parties to the extent such other Product is (i) of
comparable quality; (ii) covered by a drug master file as required by the
relevant health regulatory authorities; and (iii) available in equivalent
quantities from third parties at prices which are [c.i.] lower than prices
available from SOCHINAZ hereunder, unless SOCHINAZ shall offer to meet such
lower price. If DUSA duly exercises this right, DUSA shall purchase from
SOCHINAZ a quantity equivalent to [c.i.] of the latest annual rolling forecast
referred to in Paragraph 3.2 below.

     2.6  Products shall be supplied in units and packaging specified by DUSA.

     3.   Supply of Products.

     3.1  All sales by SOCHINAZ to DUSA under this Agreement shall be governed
exclusively by the terms of this Agreement. No additional or different terms set
forth in any of either parties purchase order, acknowledgment or other forms or
correspondence shall be of any force or effect.

     3.2  DUSA shall provide to SOCHINAZ, on or before [c.i.] during the term of
this Agreement, a rolling forecast of the volume of its requirements for
Products during the following [c.i.]. Such forecast shall be deemed a planning
target and not constitute an order for the Products and shall not be binding on
DUSA. DUSA shall only be bound to purchase such quantities of Product as
referred to in Paragraph 3.3 below. SOCHINAZ shall inform DUSA within [c.i.] of
SOCHINAZ' receipt of any of DUSA'S rolling forecast should SOCHINAZ be unable to
ship the quantities set forth in DUSA'S estimates by the date and time
indicated.

     3.3  DUSA will place firm orders with SOCHINAZ for its requirements for the
Products, giving (unless otherwise agreed) [c.i.] notice prior to the requested
date of delivery. All orders shall be promptly acknowledged by SOCHINAZ. Insofar
as these orders are not in excess of the latest forecast for the period during
which the Products are to be delivered then SOCHINAZ shall supply the Products
in accordance with DUSA's orders and meet the specific month requested by DUSA
for delivery. Orders being

                                       2
<PAGE>   3

[c.i.] in excess of DUSA's forecast for the period during which the Products are
to be delivered have to be confirmed in writing by SOCHINAZ indicating the
delivery date within the next sixty (60) days.

     3.4  Each batch of the Products supplied to DUSA by SOCHINAZ will comply
with the specifications for the Products as set out in Exhibit A to this
Agreement. SOCHINAZ will supply to DUSA along with each batch of the Products a
Certificate of Analysis stating the active ingredient percentages, the
analytical control method and specifications therefor, the shelf life of the
Product, and certifying that the particular batch complies with the
specification for the Products.

     3.5  Any dispute as to the analysis of any batch of the Products will be
settled by the decision of a mutually acceptable independent analytical
laboratory.

     3.6  SOCHINAZ will retain samples of raw materials as well as samples of
Products of each manufactured batch for a minimum period of the shelf life of
the Products plus one year, both during and after the term of this Agreement.

     3.7  DUSA and any regulatory authorities of the Territory shall be entitled
to inspect at normal office hours and upon prior notice the premises of SOCHINAZ
where the Products are manufactured and where the quality control is executed
and to inspect the process of manufacture.

     3.8  No alterations of any specification for the Products or the
manufacturing process of the Products can be made without the approval of DUSA.

     3.9  At DUSA's option, DUSA may order, and SOCHINAZ shall deliver, on a
consignment basis, up to three (3) months' supply of Product. Such supply shall
not be deemed to be part of SOCHINAZ's inventory for purposes of calculating the
amount to be purchased by DUSA under Paragraph 2.5 above.

     4.   Terms of Payment for Products.

     4.1  The prices at which SOCHINAZ agrees to sell the Products shall be as
set out in Exhibit B, and incorporated herein by reference, until the end of the
term of this Agreement. Such prices shall be at DUSA's option F.O.B. DUSA's
offices in Toronto, Ontario, Canada, Denville, New Jersey, or other place
designated by DUSA in the United States of America. The 1980 U.N. Convention of
Contracts for the International Sales of Goods shall not be applicable.

     4.2  Title and risk of loss to Product sold hereunder shall pass at DUSA's
option when delivered to DUSA in its offices in

                                       3
<PAGE>   4

Toronto, Ontario, Canada, or in the United States of America. Customs fees,
duties and the like shall be paid by [c.i.].

     4.3  Invoices for Products sold to DUSA shall be rendered and payable in
U.S. dollars. Products delivered to DUSA on consignment shall be paid for upon
resale by DUSA.

     5.   Relationship of the Parties.

     Both parties are independent contractors and not an agent or employee of
the other. Neither party is authorized to assume or create any obligation or
responsibility, including but not limited to obligations based on warranties or
guarantees or other contractual obligations, on behalf or in the name of the
other party. Neither party shall misrepresent its status or authority.

     6.   Regulatory Compliance.

     6.1  DUSA shall be responsible, at its own expense, to prepare, submit and
prosecute applications for all registrations and/or other regulatory approvals
required in connection with the sale and/or use of Products in the Territory.
Applications for approvals and registrations shall be in the name of DUSA.

     6.2  SOCHINAZ shall provide DUSA with all information in SOCHINAZ
possession useful or necessary for any and all regulatory approvals relating to
the manufacture of Product. DUSA shall not use such information for purposes
other than obtaining regulatory approvals except to the extent SOCHINAZ is
unable to supply DUSA's requirements of Products. Products hereunder in which
case DUSA shall be entitled to use such information to make or have made its
requirements of Products under the provisions of Paragraph 7 hereof.

     6.3  Each party shall immediately notify the other of any regulatory or
other administrative actions which come to that party's attention and which
affect Product.

     6.4  Without limiting any language stated above, SOCHINAZ shall manufacture
 the Products according to the good manufacturing practices and good laboratory
practices established by the United States Foods and Drug Administration ("FDA")
from time to time. In addition, SOCHINAZ shall permit DUSA the right to
reference SOCHINAZ's drug master file as provided to the FDA to enable DUSA to
sell Products in the Territory.

     7.   Force Majeure; Inability to Supply.

     (a)  Neither party shall be responsible to the other for any failure or
delay in performing any of its obligations under this Agreement or for other
nonperformance hereof if such delay or nonperformance is caused by strike,
stoppage of labor, lockout or

                                       4
<PAGE>   5

other labor trouble, fire, flood, accident, act of God or of the Government of
any country or of any State or local government, or of the public enemy of
either, or by cause unavoidable or beyond the control of any party hereto.

     (b)  However, in the event a failure or delay occurs under subparagraph
7(a) above, or if SOCHINAZ is unable to supply Product as ordered for [c.i.],
then SOCHINAZ will immediately, but on a temporary basis only, provide to DUSA
or a third party mutually agreeable to DUSA and SOCHINAZ (and under the control
and responsibility of SOCHINAZ) with all technical information needed to produce
Product from commercially available starting materials, including, but not
limited to a copy of SOCHINAZ's drug master file, and shall permit the use of
such information to produce Product until SOCHINAZ is able to demonstrate to
DUSA that it is capable of producing product in the quantities and in the
timeliness required by DUSA on ongoing basis.

     8.   Warranties and Covenants.

     8.1  SOCHINAZ warrants that Product meets and will meet the specifications
set forth in Exhibit A, that the Product is and will be free from defects in
quality, material and workmanship and is and will be merchantable and fit for
its intended purpose. These warranties and covenants shall survive the
termination of this Agreement.

     8.2  SOCHINAZ warrants that it has title to and is the owner of all
information supplied hereunder related to the production of Product; that it
does not infringe any third parties' patents or trade secrets; and that it is
free to conduct the business contemplated by the parties hereto.

     8.3  SOCHINAZ warrants that Products and their production shall comply with
all applicable laws in the Territory including but not limited to the United
States Food, Drug and Cosmetic Act, as amended and will be manufactured in
accordance with good manufacturing practices, as defined therein.

     8.4  SOCHINAZ shall indemnify and hold DUSA harmless from and against any
and all expenses (including attorneys' fees), damages, claims, liabilities or
obligations whatsoever resulting from a defect in the Product or failure to meet
its specifications (a) any claim for personal injury or property damage arising
out of or resulting from the manufacture, supply contamination, adulteration, or
shipment of the Products delivered to DUSA, or (b) any claim for personal injury
or property damage arising out of or resulting from the representations or
warranties or breach thereof by SOCHINAZ as to the Product, or (c) any other act
or inaction of SOCHINAZ.

     9.   Term and Termination.

                                       5
<PAGE>   6

     9.1  This Agreement shall remain in effect for a period of five (5) years
from the date first the Product is first approved for any therapeutic use by the
United States Food and Drug Administration, unless sooner terminated in
accordance with Section 4.2 above or 9.2 or 9.3 below.

     9.2. SOCHINAZ may terminate this Agreement without further notice if any
one or more of the following events shall occur and shall not have been cured by
DUSA ninety (90) days after notice thereof from SOCHINAZ:

          (a)  DUSA shall fail to make any payment when due hereunder, or

          (b)  DUSA shall default in the performance or observance of any other
covenant, condition or agreement contained herein.

     9.3  DUSA may terminate this Agreement without further notice if any one or
more of the following events shall occur and shall not have been cured by
SOCHINAZ within ninety (90) days after notice thereof from DUSA:

          (a)  SOCHINAZ shall fail to provide to DUSA under this Agreement
Products which meet the specifications for such Products or shall fail to ship
such Products as required by this Agreement, or

          (b)  SOCHINAZ shall default in the performance or observance of any
other covenant, condition or agreement contained herein.

     10.  Confidentiality.

     10.1 The recipient of any proprietary information which is marked as such
if written, or which is confirmed in writing to be proprietary within thirty
(30) days after disclosure, if oral, shall at all times during the continuance
of this Agreement and for a period of seven (7) years after its termination:

          -    use such proprietary information exclusively for the purpose of
               and in accordance with the terms of this Agreement; and

          -    maintain such proprietary information confidential

and the recipient will accordingly not disclose any of such proprietary
information in whole or in part save for the purposes of and in accordance with
this Agreement.

     10.2 The foregoing restrictions on the recipient shall not apply:

                                       6
<PAGE>   7

          -    to any proprietary information which the recipient can show was
               already in its possession and at its free disposal before the
               disclosure by the other party.

          -    to any proprietary information which is hereafter disclosed to
               the recipient without any obligation of confidence by a third
               party who has not derived it directly or indirectly from DUSA or,
               as applicable, SOCHINAZ.

          -    to any proprietary information which is or becomes generally
               available to the public in printed publications in general
               circulation through no act or default on the part of the
               recipient or of the recipients' agents or employees.

     11.  Miscellaneous.

     11.1 This Agreement may not be assigned by either party, without the prior
written consent of the other party, except to the acquirer of substantially all
of the securities or assets of a party hereto, in conjunction with such
acquisition.

     11.2 This Agreement, including the exhibits attached hereto, constitutes
the entire agreement, superseding all prior oral or written agreements,
understandings, negotiations, conditions and warranties, between the parties
hereto on the subject hereof; and there are no conditions to this Agreement
which are not expressed herein.

     11.3 This Agreement may be modified or amended only by a writing signed by
both of the parties hereto.

     11.4 Notification required or permitted hereby shall be deemed given only
upon enclosure thereof in an envelope, sent by courier whose contract requires
that delivery be made within three (3) business days and which provides to the
sender a written acknowledgment of receipt by the addressee, and addressed to
the party to be given notification at the address to which that party has
previously notified the party giving notice that notices are to be sent or,
otherwise, to the address listed in conjunction with that party's name first set
forth above.

     11.5 This Agreement shall be governed by and construed in accordance with
the law of the State of New Jersey, United States of America. The court of
jurisdiction for all controversies shall be the U.S. District Court for New
Jersey.

     11.6 If any one or more provisions of this agreement shall be held to be
invalid, illegal or unenforceable, the validity, legality, or enforceability of
the remaining provisions shall not

                                       7
<PAGE>   8

in any way be affected or impaired thereby. In the event any provision shall be
held invalid, illegal or unenforceable, the parties shall use best efforts to
substitute a valid, legal and enforceable provision, which insofar as possible
implements the purposes thereof.

     IN WITNESS WHEREOF, the parties have caused their authorized officers to
execute this Agreement on the date first above written.


                                       SOCHINAZ S.A.


                                       By:  /s/ Christian Borgeaud
                                          --------------------------------------

                                       Title:  CEO
                                             -----------------------------------

                                       DUSA PHARMACEUTICALS, INC.


                                       By: /s/D. Geoffrey Shulman
                                          --------------------------------------

                                       Title:  President and CEO
                                             -----------------------------------

                                       8
<PAGE>   9


                                    EXHIBIT A

                                     to the

     DUSA Pharmaceuticals, Inc./Sochinaz S.A. Supply Agreement

     [c.i.]


<PAGE>   10


                                    EXHIBIT B

                                     to the

     DUSA Pharmaceuticals, Inc./Sochinaz S.A. Supply Agreement

     [c.i.]