FIRST AMENDMENT TO THE RESEARCH AND DEVELOPMENT AND LICENSE AGREEMENT This Amendment No. 1 (the "Amendment") is made as of the 3rd day of October, 1997, by and between Apollon, Inc., a Pennsylvania corporation (the "Company") and American Cyanamid...

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT 
REQUEST. REDACTED MATERIAL IS BRACKETED ON PAGE 1 AND HAS BEEN FILED 
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                FIRST AMENDMENT TO THE
                    RESEARCH AND DEVELOPMENT AND LICENSE AGREEMENT


    This Amendment No. 1 (the "Amendment") is made as of the 3rd day of
October, 1997, by and between Apollon, Inc., a Pennsylvania corporation (the
"Company") and American Cyanamid Company, a Maine corporation ("ACY"), the
signatories to the Research and Development and License Agreement, dated as of
July 19, 1995 (the "Agreement"). 

    WHEREAS, ACY is an indirect majority owned subsidiary of American Home
Products Corporation and the Company and an affiliate of American Home Products
Corporation have entered into a Securities Purchase Agreement dated as of the
date hereof pursuant to which the Company has agreed to amend the Agreement as
hereinafter set forth;

    WHEREAS, the Company and ACY wish to amend the Agreement as hereinafter
provided; and

    WHEREAS, pursuant to Section 15.08 of the Agreement, the Agreement may only
be modified or amended in writing signed by duly authorized representatives of
the Company and ACY.

    NOW, THEREFORE, in consideration of the mutual covenants contained herein,
and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto, each intending to be legally
bound, hereby agree as follows:

         1.   All terms used herein and not defined shall have the meanings set
forth in the Agreement.

         2. Section 6.01 of the Agreement is hereby amended to add a new
provision, Section 6.01(a) to read as follows:

    "(a)      Notwithstanding the foregoing or any other provision of this
    Agreement, the $[      ] R&D Payment due to Apollon at the time of the
    [                                                                      ]
    (the "[   ] Second R&D Payment") shall be paid on the date arising [   ]
    following the date on which such [   ] Second R&D Payment otherwise becomes
    due and payable.  Apollon shall notify and provide supporting documentation
    to ACY in accordance with Sections 6.03 and 2.03 hereof at the time the [  ]
    Second R&D Payment otherwise becomes due and payable and shall send another
    notice to ACY 30 days prior to the payment date."






         3.   The address for notices to be sent to ACY pursuant to Section
15.01 of the Agreement shall be as set forth following the signature line below,
attention:  President.

         4.   All other terms and provisions of the Agreement remain in full
force and effect.

         5.   This Amendment may be executed in counterparts, each of which
shall be deemed an original and all of which shall constitute together one and
the same instrument.

    IN WITNESS WHEREOF, the parties hereto have executed this Amendment No. 1
as of the day and year first above written.

                             APOLLON, INC.


                             By: /S/Xxxxxxx X. Xxxxxxxx
                                 ______________________________
                                 Xxxxxxx X. Xxxxxxxx, Xx.
                                 President

                             Notices to be sent to:
                             Xxxxxxx X. Xxxxxxxx, Xx. Ph.D
                             President and CEO
                             Xxx Xxxxx Xxxxxx Xxxxxxx
                             Xxxxxxx, XX  00000-0000
                             Fax:      (000) 000-0000


                             AMERICAN CYANAMID COMPANY


                             By: /s/Xxxxxx X. Xxxxxxxx
                                 _____________________
                                 Name: Xxxxxx X. Xxxxxxxx
                                 Title: Vice President

                             Notices to be sent to:
                             Xxxxxx X. Xxxxxxxxx, Ph.D.
                             President
                             c/o Wyeth-Ayerst
                             000 Xxxx xx Xxxxxxx Xxxx
                             Xxxxxx, XX  00000
                             Fax:      (000) 000-0000


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