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                                                                   Exhibit 10.26

                       CERTIFICATE OF CONTINGENT INTEREST
                       IN COMMON STOCK $0.001 PAR VALUE OF
                           ARGUS PHARMACEUTICALS, INC.

           ISSUED PURSUANT TO PLAN AND AGREEMENT OF MERGER DATED AS OF
                           FEBRUARY 22, 1995, BETWEEN

                       TRIPLEX PHARMACEUTICAL CORPORATION,
                        ARGUS PHARMACEUTICALS, INC., and
                          API ACQUISITION COMPANY NO. 1


                         READ THIS CERTIFICATE CAREFULLY

                             THIS CERTIFICATE IS NOT
              TRANSFERABLE OR ASSIGNABLE EXCEPT AS HEREIN PROVIDED


         This is to certify that __________________is the registered holder of
_________Units of Contingent Interest with respect to shares of Common stock,
$0.001 par value, of Argus Pharmaceuticals, Inc., a Delaware corporation ("Argus
Common Stock"), subject to adjustment as hereinafter provided, issued pursuant
to the provisions of the Plan and Agreement of Merger dated as of February 22,
1995. Each Unit of Contingent Interest represents the right to receive the
number of shares of Argus Common Stock, if any, that may be distributable upon
the terms and subject to the conditions hereinafter set forth.

                                     Argus Pharmaceuticals, Inc.



                                     By:_____________________

Dated: ____________, 1995
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This Certificate is one of the Contingent Interest Certificates for an aggregate
of 7,006,448 Units of Contingent Interest ("Contingent Stock Issue Rights")
issued pursuant to the Plan and Agreement of Merger (the "Merger Agreement)
dated as of February 22, 1995, among Argus Pharmaceuticals, Inc., a Delaware
corporation ("Argus"), API Acquisition Company No. 1, a Delaware corporation
("Merger Sub"), and Triplex Pharmaceutical Corporation, a Delaware corporation
("Triplex"), pursuant to which Merger Sub was merged with and into Triplex. The
terms and conditions upon which the registered holder of this Certificate may
become entitled to shares of common stock, $0.001 par value, of Argus ("Argus
Common Stock") are set forth below.

                     SECTION 1. RIGHTS TO ARGUS COMMON STOCK

         Subject to the terms hereof, and subject to the satisfaction of the
conditions provided herein, each Unit of Contingent Stock Issue Rights shall
entitle the holder thereof to receive, and shall automatically be converted into
that number of shares of Argus Common Stock determined as follows:

         (i)      if a Triplex Milestone Event (as hereinafter defined) has
                  occurred, each Contingent Stock Issue Right shall entitle the
                  holder thereof to receive the number of shares of Argus Common
                  Stock obtained by dividing .71363 by the Fair Market Value of
                  the Argus Common Stock on the date the Triplex Milestone Event
                  occurs;

         (ii)     if the Argus Milestone Event (as hereinafter defined) has not
                  occurred, each Contingent Stock Issue Right shall entitle the
                  holder thereof to receive the number of shares of Argus Common
                  Stock obtained by dividing .42818 by the Fair Market Value of
                  the Argus Common stock on the day after it is determined that
                  the Argus Milestone Event has not occurred.

         If neither of the conditions set forth in subparagraphs (i) and (ii)
above are met, then each Contingent Stock Issue Right shall not entitle the
holder to receive any shares of Argus Common Stock, and if both of said
conditions are met, each Contingent Stock Issue Right shall entitle the holder
to receive the sum of the number of shares of Argus Common Stock set forth in
said conditions.

For the purposes of this Section 1:

         A Triplex Milestone Event shall have occurred if (A) Argus or any
affiliate or subsidiary thereof shall have entered into an agreement (a
"Qualifying License Agreement") on or before the second anniversary of the date
of issuance of the Contingent Stock Issue Rights (the "Second Anniversary") with
respect to the licensing of Triplex's biopharmaceutical candidate known as
"T30177" whereby Argus or any affiliate or subsidiary thereof receives
consideration of at least $5,000,000 in cash or an unconditional (except for
customary closing conditions and deliveries not related to the achievement of
any milestones) binding commitment for not less than $5,000,000; provided that
to the extent such consideration consists in whole or in part of the
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purchase of Argus Common Stock, the conversion ratio in subparagraph (i) above
shall be multiplied by a fraction, (x) the numerator of which shall be the total
of all cash and unconditional (except for customary closing conditions and
deliveries not related to the achievement of any milestones) binding commitments
received by Argus under such Qualifying License Agreement less an amount equal
to the Fair Market Value (on the date of purchase) of the shares of Argus Common
Stock purchased pursuant to such Qualifying License Agreement, and (y) the
denominator of which shall be $5,000,000 provided that in no event shall such
numerator of such fraction exceed $5,000,000; or (B) on or before the Second
Anniversary the Board of Directors of Argus has determined to commit its
resources to actively pursue the clinical development of T30177 at Argus without
entering into a Qualifying License Event, and within three years after the
Second Anniversary, Argus shall have data from said clinical trials which is
determined in good faith by the Board of Directors of Argus to be sufficient to
file a new drug application with the U. S. Food and Drug Administration.

         The Argus Milestone Event shall have occurred if Argus or its
subsidiaries or affiliates has received a minimum of $5,000,000 in equity
milestone payments from Genzyme Corporation or any successor on or before the
Second Anniversary with respect to the development of Argus's product known as
"Tretinoin" or any pharmaceutical composition incorporating AR- 623.

         The "Fair Market Value" of one share of Argus Common Stock shall mean,
for any day, (x) the price determined by averaging over a period of twenty (20)
consecutive trading days immediately prior to the Issuance Date the last
reported sale price for the Argus Common Stock on each such trading day on the
principal securities exchange on which the Argus Common Stock is listed or
admitted to trading or if no such sales takes place on any such dates, the
average of the closing bid and asked prices thereof as officially reported, or,
if not so listed or admitted to trading on any securities exchange, the last
sale price for the Argus Common Stock on the National Association of Securities
Dealers National Market System on such date, or, if there shall have been no
trading on such or if the Common Stock shall not be listed on such system, the
average of the closing bid and asked prices in the over-the-counter market as
furnished by any New York Stock Exchange member firm selected from time to time
by Argus for such purpose, or (y) if the Argus Common Stock shall not be listed
or admitted to trading as provided in clause (x) above, the fair market value of
the Argus Common Stock as determined in good faith by the Board of Directors of
Argus; provided, in no event shall the Fair Market Value be less than $l.l4181
for one share of Argus Common Stock such that the Units shall never be
convertible into more shares of Argus Common Stock than are issued at closing of
the Merger Agreement; and

         Upon satisfaction of the conditions specified in subparagraph (i)
and/or (ii) above of Section 1, the registered holder of this Certificate shall
be considered a record holder of the number of shares of Argus Common Stock
specified in such subparagraph. Upon satisfaction of the conditions specified in
subparagraph (i) and/or (ii) of Section 1, Argus shall issue to the holder of
this Certificate, upon surrender of this Certificate to Argus or an agent
designated by Argus, that number of shares of Argus Common Stock issuable upon
conversion of the number of Contingent Stock Issue Rights represented by this
Certificate; provided, that, if any of the conditions set forth in subparagraph
(i) and/or (ii) may still be met and have not expired in
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accordance with their terms, then the Certificate will be returned to the holder
with a proper notation indicating that shares of Argus Common Stock have been
issued and may still be issued in the future.

                              SECTION 2. DIVIDENDS

         No dividends shall be payable with respect to the Argus Common Stock
represented by this Certificate until a record date has occurred after the
issuance thereof.

                     SECTION 3. REPLACEMENT OF CERTIFICATES

         Upon receipt of evidence satisfactory to Argus or its agent of the
loss, theft, destruction, or mutilation of any Certificate and upon receipt of
indemnity reasonable satisfactory to Argus or its agent, Argus shall deliver a
new Certificate for the number of Contingent Stock Issue Rights represented by
the Certificate so lost, stolen, destroyed, or mutilated.

                        SECTION 4. HOLDER NOT SHAREHOLDER

         This Certificate does not entitle the holder thereof to any voting or
other rights as a shareholder of Argus.

                   SECTION 5. ADJUSTMENT OF ARGUS COMMON STOCK

         5.1      Stock Dividends, Etc. In case Argus shall (1) pay a dividend
                  in shares of argus Common Stock; (2) subdivide outstanding
                  shares of Argus Common Stock; (3) combine outstanding shares
                  of Argus Common Stock into a smaller number of shares; or (4)
                  issue by reclassification any shares of Common Stock, the
                  number of shares of Argus Common Stock issuable upon
                  conversion of the Contingent Stock Issue Rights represented by
                  this Certificate shall be proportionately adjusted.

         5.2      Merger, Etc. In case of (1) any consolidation or merger of
                  Argus with or into another corporation or (2) any sale,
                  transfer, or other disposition of all or substantially all of
                  the property, assets, or business of Argus as a result of
                  which property (cash or otherwise) shall be payable or
                  distributable to the holders of Argus Common Stock, the
                  Certificate shall thereafter represent the number and class of
                  shares or other securities or property of Argus, or of the
                  corporation or other entity resulting from such consolidation
                  or merger or to which such sale, transfer, or other
                  disposition shall have been made for or into which the Argus
                  Common Stock underlying this Certificate would have been
                  exchanged or converted upon such event if outstanding at the
                  time thereof. The terms of any such consolidation, merger,
                  sale, transfer, or other disposition shall include appropriate
                  provisions in accordance with the provisions of this Section
                  5.2. The provisions of this Section 5.2 shall similarly apply
                  to successive consolidations, mergers, sales, transfers, or
                  other dispositions as aforesaid.
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         5.3      Notice. Whenever an adjustment is made as provided in this
                  Section 5, Argus shall promptly mail to the holder of this
                  Certificate, at the address appearing below unless changed by
                  written notice by the holder, a statement setting forth the
                  adjustment and the facts giving rise thereto.

                       SECTION 6. TRANSFER OF CERTIFICATES

         This Certificate is not transferable or assignable except by the laws
of descent and distribution, by will or by operation of law.

                      SECTION 7. INITIAL ADDRESS FOR NOTICE

         Notice may be given at the following address:

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                        SECTION 8. RESERVATION OF SHARES

         The Company agrees and covenants that at all times while shares of
         Argus Common Stock are issuable hereunder it will reserve for issuance
         a number of shares of its authorized but unissued Argus Common stock
         sufficient to perform its obligations under this Certificate and the
         Contingent Stock Issue Rights.

                            SECTION 9. GOVERNING LAW

         This Certificate shall be governed by and construed in accordance with
         the laws of the State of Delaware.
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                               AFFILIATE'S LETTER



Argus Pharmaceuticals, Inc.
3600 Research Forest Drive
The Woodlands, Texas 77380

Gentlemen:

         The undersigned, a holder of shares of common stock, par value $.001
per share ("Triplex Common Stock"), of Triplex Pharmaceuticals Corporation, a
Delaware corporation ("triples", is entitled to receive in connection with the
merger (the "Merger") into Triplex of Argus Acquisition Company No. 1, a
Delaware corporation (the "Company"), shares of common stock, par value $.001
per share (the "Argus Common Stock"), of Argus Pharmaceuticals, Inc., stock, par
value $.001 per share (the "Argus Common stock"), of argus Pharmaceuticals, Inc.
a Delaware corporation ("Argus"), and Contingent Stock Issue rights in Argus
Common Stock The undersigned acknowledges that he may be deemed an "affiliate"
of Triplex within the meaning of Rule 145 ("Rule 145") promulgated under the
Securities Act of 1933, as amended (the "Act"), although nothing contained
herein is to be construed as an admission of such fact Capitalized terms used
but not defined herein will have the meaning set forth in the Plan and agreement
of Merger dated February ____, 1995 regarding the Merger.

         If in fact the undersigned were an affiliate under the Act, the
undersigned's ability to sell, assign or transfer the Argus Issued Stock and the
Contingent Issue stock Rights and the shares of Argus Common Stock issuable on
their conversion issued to him pursuant to the Merger may be restricted unless
such transaction is registered under the Act or an exemption from such
registration is available. The undersigned understands that such exemptions are
limited and, to the extent the undersigned felt necessary, has obtained advise
of counsel as to the nature and conditions of such exemptions, including
information with respect to the applicability to the sale of such securities of
Rule 145 (d) promulgated under the Act.

         The undersigned hereby represents to and covenants with the Company and
Argus that he will not sell, assign or transfer any of the shares of Argus
Issued Stock, and the Contingent Issue stock rights and the shares of Argus
Common Stock issuable on their conversion issued to him pursuant to the Merger
except (1) pursuant to an effective Registration Statement under the Act, (ii)
in conformity with the volume and other limitations of rule 145(d) promulgated
under the Act and/or (iii) in a transaction which, in the opinion of independent
counsel reasonably satisfactory to Argus or as described in a "no-action" or
interpretive letter from the Staff of the Securities and Exchange Commission, is
not required to be registered under the Act. In the event of a sale or other
disposition pursuant to Rule 145(d), the undersigned will supply Argus with
evidence of compliance with such Rule, in the form of a letter satisfactory to
Argus.

         The undersigned acknowledges and agrees that appropriate restrictive
legends will be placed on certificates representing argus Common Stock received
by the undersigned in the
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Merger or upon conversion of the Continent Stock Issue Rights. Argus agrees to
remove said legends on receipt of evidence reasonably satisfactory to it,
including an opinion of counsel, that the legends may be removed in accordance
with applicable laws, including Rule 144 (k) promulgated under the Act.

                                Very truly yours,



                                By:____________________
                                Name:__________________
                                Title:_________________

Dated:________________

Accepted and Agreed to:

ARGUS PHARMACEUTICALS, INC.



By:___________________________

Name:_________________________

Title:________________________

Date:_________________________