<PAGE>
 
                                                                   Exhibit 10.36
                              HOROSZIEWICZ-CYTOGEN

                                   AGREEMENT

This Agreement, effective the 20th day of April 1989, between Julius S.
Horosziewicz, M.D., DMSc., whose address is Millard Fillmore Hospital,
Department of Urology, 3 Gates Circle, Buffalo, New York, 14209, (hereinafter
"HOROSZIEWICZ") and Cytogen Corporation, with offices at 600 College Road East,
Princeton, New Jersey, 08540, (hereinafter "CYTOGEN").


                                   ARTICLE I

                                   BACKGROUND

1.01    Research conducted by HOROSZIEWICZ has resulted in the discovery of a
certain murine monoclonal antibody which detects an antigen associated with
human prostatic epithelium and reacts with serum of prostatic cancer patients,
and the hybridoma for producing this antibody.

1.02    HOROSZIEWICZ has filed a patent application in the United States Patent
and Trademark Office describing and claiming said murine monoclonal antibody and
the hybridoma which produces it.

1.03    HOROSZIEWICZ desires to assign said patent application in order to
expedite the commercialization of the murine antibody and its use in therapeutic
and diagnostic products.
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1.04    Since January, 1987 scientists at CYTOGEN have been collaborating with
HOROSZIEWICZ in evaluating the monoclonal antibody and have determined that it
has potential commercial value.

1.05    CYTOGEN wishes to take an assignment of said patent application and to
plan the commercialization of the monoclonal antibody and HOROSZIEWICZ is
willing to assign the patent application to CYTOGEN for that purpose.


                                   ARTICLE II

                                  DEFINITIONS

2.01    "Affiliate" shall mean any corporation, company, partnership, joint
venture and/or firm which controls, is controlled by or is under common control
with CYTOGEN.  Control shall mean (a) in the case of corporate entities, direct
or indirect ownership of at least forty percent (40%) of the stock or
participating shares entitled to vote for the election of directors; and (b) in
the case of non-corporate entities, direct or indirect ownership of at least
forty percent (40%) of the equity interest with the power to direct the
management and policies of such non-corporate entity.

2.02    "Agreement" shall mean this Agreement.

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2.03    "Antibody" shall mean that murine monoclonal antibody to prostatic
carcinoma cells designated as 7Ell-C5 antibody which is produced from the
corresponding Hybridoma, including its conjugates, derivatives, fragments and
covalently and genetically modified structures, including reclones.

2.04    "Assigned Application" shall mean United States Patent Application
Serial Number 07/202,869 entitled "Monoclonal Antibodies to a New Antigenic
Marker in Epithelial Prostatic Cells and Serum of Prostatic Cancer Patients"
filed in the United States Patent and Trademark Office on June 3, 1988 by
HOROSZIEWICZ.

2.05    "Effective Date" shall be the date first written above.

2.06    "Field of Use" shall mean any and all in vitro and in vivo uses of
                                              -- -----     -- ----        
Product in the diagnosis, prophylaxis and treatment of disease.

2.07    "Hybridoma" shall mean the cell line which is capable of producing the
Antibody, and genetically modified derivatives of the cell line, including
reclones.

2.08    "Improvements" shall mean any advances in or modifications to Product
and Hybridoma which HOROSZIEWICZ develops or acquires during the term of this
Agreement including, but not limited to, all scientific data developed by
HOROSZIEWICZ during

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his conduct of research sponsored by CYTOGEN as provided in sub-paragraph (iv),
paragraph 5.01, Article V hereinbelow.

2.09    "Know-How" shall mean all data, information, technology or special
ability on the part of HOROSZIEWICZ relating to the research, development,
manufacture, testing or use of Hybridoma or Antibody, which are reasonably
related to Product for use in the Field of Use and which are useful in seeking
approval from appropriate governmental health authorities to market Product for
the diagnosis, prophylaxis and treatment of diseases including all animal,
laboratory and human clinical data, technical information, knowledge,
inventions, techniques, processes, systems, formulae, results of
experimentation, designs, statistics and records pertaining to Hybridoma and
Antibody; characterization of Antibody; and all methods of making and using
Hybridoma and Antibody in the detection, evaluation, prevention and treatment of
any disease or condition, whether conducted for experimental or clinical
purposes, owned or controlled by HOROSZIEWICZ.

2.10    "Net Sales" shall mean [Information omitted and filed separately with
 he Commission under Rule 24b-2.
 
 
 

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                                                  ]

2.11    "Patent Assets" shall mean the Assigned Application, any division,
continuation or continuation-in-part of the Assigned Application and any patent
which shall issue based on the Assigned Application, division, continuation or
continuation-in-part; any

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patent which is a reissue or extension of, or a patent of addition to, any
patent issuing from Assigned Application, or any division, continuation or
continuation-in-part of Assigned Application; any patent application or patent
identified hereinbefore which is hereafter filed or issued in any country of the
Territory; and any patent application which is related to or based on any of
HOROSZIEWICZ's Know-How developed during the performance of this
Agreement,including, but not limited to, the performance of research by
HOROSZIEWICZ which shall be sponsored by CYTOGEN as provided in sub-paragraph
(iv), paragraph 5.01, Article V, hereinbelow, and any division, continuation and
continuation-in-part of said patent application; and any patent which is a
reissue or extension of, or a patent of addition to, any such patent.

2.12    "Payment Product" shall mean and include any Product for use in the
Field of Use (i) which is within the scope of a Valid Claim of a Patent Asset;
or (ii) whose use is within the scope of a Valid Claim of a Patent Asset; or
(iii) which is manufactured or packaged within the scope of a Valid Claim of a
Patent Asset.

2.13    "Product" shall mean any one or more of the following:  (a) ascites or
culture supernatant fluid which contains Antibody, (b) purified Antibody, (c)
chemically, biochemically and genetically modified Antibody, and (d) a
composition which incorporates (i) Antibody or (ii) chemically, biochemically,

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genetically, including covalently, modified Antibody in physical admixture with
inert or active ingredients.

2.14    "Valid Claim" shall mean and include a claim in an issued patent of a
Patent Asset which has not lapsed or become abandoned and which claim has not
been declared invalid by an unreversed or unappealable decision or judgment of a
court of competent jurisdiction.

2.15    "Territory" shall mean the entire world.


                                  ARTICLE III

                    ASSIGNMENT, WARRANTY AND INDEMNIFICATION

3.01    Attached hereto and made part of this Agreement is an Assignment of
Assigned Application dated April 20, 1989, by HOROSZIEWICZ conveying all right,
title and interest in and to said Assigned Application and to all inventions and
discoveries disclosed in said Assigned Application to CYTOGEN.

3.02    HOROSZIEWICZ warrants and represents that he has full right, title and
interest in and to the Assigned Application, Hybridoma, Antibody and Know-How;
that he has the power to make the assignment provided for in paragraph 3.01
hereinabove and to enter into this Agreement without burdens, encumbrances,
restraints or limitations of any kind which could adversely affect the right and

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<PAGE>
 
title of CYTOGEN under this Agreement; and that there exist no outstanding
written or oral agreements or commitments of any kind inconsistent with this
Agreement to which HOROSZIEWICZ is a party.

3.03    HOROSZIEWICZ shall indemnify and hold harmless CYTOGEN against any and
all actions, suits, claims, demands, prosecutions, liabilities or judgments that
may be brought, instituted or arise against CYTOGEN based on the ownership by
CYTOGEN of the Assigned Application and its progeny as defined under "Patent
Assets" in Article I hereinabove, Know How and Improvements and the practice by
CYTOGEN, or any licensee of CYTOGEN, of the inventions disclosed in the Patent
Assets, Know How and Improvements.


                                   ARTICLE IV

                            DELIVERY AND MAINTENANCE

4.01    CYTOGEN acknowledges delivery by HOROSZIEWICZ of samples of Hybridoma
and Antibody which, except for the expression by the Hybridoma of retroviral
reverse transcriptase, were delivered free of other immunoglobulins and non-
immunoglobulin contaminants and possessed the physical and chemical properties
stated in the KnowHow which was delivered to CYTOGEN simultaneously with the
delivery of Hybridoma and Antibody.

4.02    During the term of this Agreement and at the expense of Cytogen,
HOROSZIEWICZ and CYTOGEN shall maintain repositories of

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Hybridoma to ensure a supply of said Hybridoma to CYTOGEN and HOROSZIEWICZ in
the event of death or unfavorable modification of either party's supplies of
said Hybridoma.  The details of said repositories (including quantities,
specific clones and sister clones to be maintained) shall be agreed to by the
parties in each instance.  HOROSZIEWICZ may use the Hybridoma only to perform
research for CYTOGEN under this Agreement and for his own private, non-
transferrable research; HOROSZIEWICZ may not make the Hybridoma available to any
third party.

4.03    HOROSZIEWICZ shall forthwith and from time to time during the term of
this Agreement make available to CYTOGEN all Know-How relevant to the production
of Antibody from Hybridoma, including prompt notification to CYTOGEN of any data
or results which relate to a change in the characteristics or performance of
Hybridoma or Antibody.


                                   ARTICLE V

                       CONSIDERATION, GRANT AND PAYMENTS

5.01    In consideration for,

        (i)   The Assignment provided for in paragraph 3.01 hereinabove; and,

        (ii)  The delivery of the Hybridoma, Antibody and Know-How; the
maintenance of the Hybridoma, and the availability of

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Know-How as provided for in Article IV hereinabove, the right and title to all
of which HOROSZIEWICZ hereby grants, assigns and transfers to CYTOGEN; and,

        (iii) The right to possess and use the Hybridoma, Antibody and Know-
How in the Territory; and the right to make, have made, use and sell any and all
Payment Products under Patent Assets in the Field of Use throughout the
Territory, the right and title to all of which HOROSZIEWICZ hereby grants,
assigns and transfers to CYTOGEN; and,

        (iv)   Research to be performed by HOROSZIEWICZ in the field of
monoclonal antibodies useful in the treatment of prostatic cancer, under the
sponsorship of CYTOGEN in accordance with a protocol to be agreed to by the
parties and to be made part of this Agreement, and the Improvements and Know-How
developed by HOROSZIEWICZ during the course of said research, the right and
title to all of which HOROSZIEWICZ hereby grants, assigns and transfers to
CYTOGEN;

        CYTOGEN shall pay HOROSZIEWICZ and/or his designee(s) the following 
compensation:

        (a) The sum of [Information omitted and filed separately with the
Commission under Rule 24b-2.] upon the Effective Date of this Agreement, which
sum shall be paid directly to Mr. S. Leslie Misrock, 1155 Avenue of the
Americas, New

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York, New York 10036, to reimburse Mr. Misrock for his prior sponsorship of
HOROSZIEWICZ's research;

        (b) The sum of [Information omitted and filed separately with the
Commission under Rule 24b-2.] said payment to be made directly to HOROSZIEWICZ
in four (4) equal quarterly installments of [Information omitted and filed
separately with the Commission under Rule 24b-2.], the first payment to be made
on a date within thirty (30) days from the Effective Date of this Agreement.

        (c) A payment of [Information omitted and filed separately with the
Commission under Rule 24b-2.]

        (d) In the event CYTOGEN licenses Payment Products to a non-affiliated
third party and receives a royalty on Net Sales by such non-affiliated third
party of such Payment Product, the payments due HOROSZIEWICZ under Section
5.01(c) of this Agreement shall be superceded and the net royalty actually
received by CYTOGEN from such third party shall be shared between CYTOGEN and
HOROSZIEWICZ as follows: [Information omitted and filed separately with the
ommission under Rule 24b-2.
 
 
 

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                         ]

5.02    The payment provided for in sub-paragraph (c) of the paragraph 5.01,
Article V hereinabove due under Patent Assets shall continue until the date of
expiration of the last to expire of the Patent Assets in each country, whereupon
all further payments to HOROSZIEWICZ on Net sales under sub-paragraph (c),
paragraph 5.01, Article V in said country shall cease and no further payments
shall be due; provided however, (i) in those countries of the Territory wherein
a patent application as defined under "Patent Assets" in paragraph 2.11, Article
II hereinabove has been filed but shall not have issued into a corresponding,
valid and subsisting patent ten (10) years from the date of first
commercialization of a Payment Product in a given country of the Territory then,
in that event, no further royalties shall be due and payable to HOROSZIEWICZ
effective upon the date of expiration of said ten (10)-year period with respect
to each applicable country, and (ii) in those countries wherein an Assigned
Application or corresponding patent application has been filed and abandoned, no
further royalties shall be due and payable to HOROSZIEWICZ effective upon the
date of such abandonment; provided further, in those countries of the Territory
wherein a patent application as defined under "Patent Assets" in paragraph 2.11,
Article II hereinabove is pending and one or more of the Payment Products become
subject to substantial competition, the payment provided for in sub-paragraph
(c),

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paragraph 5.01, Article V shall be suspended for so long as such competition
subsists.  Substantial competition, as used herein, is intended to mean the sale
by any third party of a Product in excess of One Million Dollars ($1,000,000.00)
in each affected country.


                                   ARTICLE VI

                         PAYMENT REMITTANCE AND RECORDS

6.01    Payments based on Net Sales as required under subparagraph (c),
paragraph 5.01, Article V to be made by CYTOGEN to HOROSZIEWICZ shall be made in
United States Dollars for each calendar quarter and each such payment shall
include the payments which shall have accrued during the subject calendar
quarter and shall be accompanied by a report setting forth separately the Net
Sales of Payment Products sold under Patent Assets during said calendar quarter
in each country of the Territory and the calculation of payments payable for
such calendar quarter.  Payments based on United States sales shall be made
within sixty (60) days following the end of each calendar quarter, while
payments based on Net Sales outside the United States shall be made within
ninety (90) days following the end of each calendar quarter.

6.02    No payments shall be due on sales between CYTOGEN and its Affiliates;
between Affiliates, or between CYTOGEN and its licensees.

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6.03    The remittance of payments payable under sub-paragraph (c), paragraph
5.01, Article V on Net Sales of Payment Products outside the United States shall
be made to HOROSZIEWICZ at the official rate of exchange of the currency of the
country from which the payments are payable (as quoted by the Citibank of New
York City) for the last business day of the calendar quarter in which the
payments were payable (less any withholding or transfer taxes which are
applicable).  CYTOGEN shall supply HOROSZIEWIcz with proof of payment of such
taxes paid on CYTOGEN's behalf.

6.04    CYTOGEN shall keep and maintain records of sales made pursuant to the
rights granted hereunder.  Such records shall be open to inspection at any
reasonable time during normal business hours within three (3) years after the
payment period to which such records relate by an independent Certified Public
Accountant (or equivalent in a foreign country) selected and paid for by
HOROSZIEWICZ, who shall have the right to examine the records kept pursuant to
this Agreement and to report findings of said examination of records to
HOROSZIEWICZ insofar as it is necessary to evidence any mistake or underpayment
on the part of CYTOGEN.


                                  ARTICLE VII

                                    PATENTS

7.01    CYTOGEN shall have full responsibility for the prosecution of the
Assigned Application in the United States Patent

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and Trademark Office, including the payment of expenses, attorney fees related
thereto, and maintenance fees.

7.02    The selection of countries outside the United States in which the
Assigned Application and its progeny, as defined under "Patent Assets" in
Article I hereinabove shall be filed prior to the expiration of the Convention
Date under the Paris Convention in countries outside the United States; the
filing thereof, and the expenses relating to the prosecution and maintenance
thereof, including attorney fees, annuities and taxes, shall be the
responsibility of CYTOGEN.  CYTOGEN shall promptly advise HOROSZIEWICZ of its
decisions relating to filing in countries outside the United States.  In the
event HOROSZIEWICZ determines that certain countries of the world outside the
United States should be added to the list of those wherein filing of the progeny
of Assigned Application has been decided upon by CYTOGEN then, in that event,
HOROSZIEWICZ shall be free to effectuate such filing, including payment for
subsequent prosecution, maintenance, taxes and annuities, at his own expense.
CYTOGEN shall aid HOROSZIEWICZ by providing him with all documents necessary to
accomplish such filing.

7.03    CYTOGEN shall have sole responsibility for the selection of patent
counsel to file, prosecute and maintain the Patent Assets in all countries of
the Territory.

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                                 ARTICLE VIII

                                     CREDIT

8.01    All payments made by CYTOGEN to HOROSZIEWICZ under subparagraphs (a) and
(b), paragraph 5.01, Article V hereinabove and all payments made by CYTOGEN to
HOROSZIEWICZ relating to expenses applicable to filing, prosecution, attorney
fees, maintenance, taxes and annuities under paragraphs 7.01 and 7.02, Article
VII hereinabove, shall be credited against payments due and payable under sub-
paragraph (c), paragraph 5.01, Article V and paragraph 6.01, Article Vi
hereinabove.


                                   ARTICLE IX

                                  INFRINGEMENT

9.01    In the event CYTOGEN is sued by a third party charging infringement of a
patent resulting from the manufacture, use or sale by CYTOGEN of a Payment
Product, CYTOGEN shall promptly notify HOROSZIEWICZ and may, at its option and
in its sole discretion, discontinue the manufacture, use or sale of a Payment
Product in the applicable country.  In the event the suit is continued, CYTOGEN
shall have the right, during the period in which any such suit is pending, to
apply all of its litigation expenses in such suit against the payments due
HOROSZIEWICZ under sub-paragraph (c), paragraph 5.01, Article V and paragraph
6.01, Article VI hereinabove.

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9.02    In the event of a judgment in any suit requiring CYTOGEN to (a) pay
royalty to (b) grant a sublicense to or (c) enter into a cross-licensing
arrangement with a third party, or in the event of a settlement of such suit
requiring royalty payments to be made, licenses granted, or cross-licensing
entered into, payments due HOROSZIEWICZ under sub-paragraph (c), paragraph 5.01,
Article V hereinabove shall be correspondingly reduced by the amounts due under
the requirement of such judgment or under the terms of such settlement; provided
however, that such reduction shall not reduce the payments due HOROSZIEWICZ
under sub-paragraph (c), paragraph 5.01, Article V to an amount less than one-
half (1/2) of the amount which would otherwise be due HOROSZIEWICZ thereunder.

9.03    In the event CYTOGEN shall be compelled by a governmental agency to
grant a compulsory license to a third party in any country of the Territory
wherein Patent Assets are subsisting, under laws applicable to such country, on
terms more favorable than those granted CYTOGEN under this Agreement, including,
but not limited to the payments due HOROSZIEWICZ under sub-paragraph (c),
paragraph 5.01, Article V and paragraph 6.01, Article VI hereinabove, at a rate
lower than those required to be paid by CYTOGEN, then CYTOGEN shall promptly
notify HOROSZIEWICZ of such compulsory license and the terms applicable under
such compulsory license shall supersede the corresponding terms under this
Agreement as at the date on which such compulsory license shall have become
effective.

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9.04    Each party shall promptly notify the other party if it becomes aware of
any infringement of Patent Assets.  CYTOGEN shall have no obligation to
HOROSZIEWICZ to initiate litigation or otherwise protect any patent or
proprietary right assigned under this Agreement and shall be free to pursue any
course of action it elects to take in connection with such acts of infringement
by third parties.  In the event CYTOGEN decides to initiate or to fully
participate in any legal action initiated by a third party to protect its
interests, HOROSZIEWICZ shall cooperate with CYTOGEN in such action.  If CYTOGEN
elects to institute suit against a third party to protect any patent or
proprietary rights assigned under this Agreement, all associated costs
(including reasonable attorney fees) which have been paid by CYTOGEN shall be
offset against any payments due and payable to HOROSZIEWICZ under subparagraph
(c), paragraph 5.01, Article V and paragraph 6.01, Article VI hereinabove.


                                   ARTICLE X

                    COMMERCIAL DEVELOPMENT AND RE-ASSIGNMENT

10.01  CYTOGEN agrees to use reasonable efforts to commercialize the Antibody as
soon as reasonably practicable, consistent with its sound and reasonable
business practices and judgment.  CYTOGEN shall advise HOROSZIEWICZ in writing
on an annual basis regarding its efforts toward commercial development of the
Antibody.  Such progress reports by CYTOGEN shall continue until either (a) the

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Antibody shall have been commercialized by CYTOGEN or (b) CYTOGEN, in its
judgment, shall conclude that the marketing and commercialization of the
Antibody is impracticable, inadvisable or not feasible, and shall so advise
HOROSZIEWICZ in writing.

10.02  In the event that CYTOGEN (a) fails to continue reasonable efforts toward
commercial development of the Antibody, or (b) decides against marketing the
Antibody as described in paragraph 10.01 of this Article X within five (5) years
from the Effective Date of this Agreement, CYTOGEN shall re-assign the Assigned
Application and its progeny, as defined in "Patent Assets" under Article I
hereinabove to HOROSZIEWICZ and the assignments made to CYTOGEN by HOROSZIEWICZ
hereunder shall automatically be converted to non-exclusive license rights.  In
the event of such automatic conversion, (i) the payment rate provided for in
subparagraph (c), paragraph 5.01, Article V hereinabove shall be reduced from
[Information omitted and filed separately with the Commission under Rule 24b-
2.], which payment shall be payable for the periods of time provided for in
paragraph 5.02, Article V hereinabove commencing with the date of such automatic
conversion, and (ii) all further responsibility by CYTOGEN under Article VII
shall cease.


                                   ARTICLE XI

                              TERM AND TERMINATION

11.01    Unless sooner terminated as herein provided, this Agreement shall
continue in full force and effect for the time

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commencing with the Effective Date and continuing (a) as to those countries of
the Territory wherein issued and valid patents as defined under "Patent Assets"
are subsisting, until the date of expiration of the last such patent in such
country, and (b) as to those countries of the Territory wherein the Assigned
Application or a corresponding patent application has been filed and (i) is
pending, until the date ten (10) years following the date of first commercial
sale in the applicable country, for so long as said patent application is
pending, or (ii) has been abandoned, until the date of abandonment.  Upon the
expiration of any of the applicable dates provided for in (a) and (b) of this
paragraph 11.01, the payments required under sub-paragraph (c), paragraph 5.01,
Article V shall be fully paid upon such date and, as provided in paragraph 5.02.
Article V hereinabove, no further payments shall be due HOROSZIEWICZ as to the
applicable country.


                                  ARTICLE XII

                                 ASSIGNABILITY

12.01  This Agreement is not assignable by either party except with the prior
written consent of the other and except that it may be assigned without consent
(i) by HOROSZIEWICZ in whole or in part to a private charitable trust and/or
public foundation (qualifying under Section 501(c) (3) of the Internal Revenue
Code) for cancer research, and (ii) by CYTOGEN to the successor of CYTOGEN or to
a

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person acquiring all or substantially all of the business and/or assets of
CYTOGEN.


                                  ARTICLE XIII

                                     NOTICE

13.01    Any notice required under this Agreement shall be in writing and shall
be considered given one day after such notice, properly addressed and shipped
overnight service, is sent by either party to the other.  Proper address for
notice is as follows:

     if to HOROSZIEWICZ:

          Julius S. Horosziewicz, M.D., DMSC.                                 
          Senior Research Scientist                                           
          Department of Urology                                               
          Millard Fillmore Hospital                                           
          3 Gates Circle                                                      
          Buffalo, New York 14209 c/o Ms. Ramena Bober                         


     with copies to:

          S. Leslie Misrock, Esq-                            
          Pennie & Edmonds                                  
          1155 Avenue of the Americas                       
          New York, New York 10036                           


     if to CYTOGEN:

          Thomas J. McKearn, M.D., PhD.
          Senior Vice President
          Scientific Affairs
          Cytogen Corporation
          201 College Road East
          Princeton, New Jersey 08540

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<PAGE>
 
     with copies to:

          William J. Ryan, Esq.
          Vice President & General Counsel
          Cytogen Corporation
          600 College Road East
          Princeton, New Jersey 08540


                                  ARTICLE XIV

                                 MISCELLANEOUS

14.01          This Agreement constitutes the entire Agreement between the
parties and supersedes all written and oral prior agreements or understandings.
No variation or modification of the terms or provisions of this Agreement shall
be valid unless in writing and signed by both parties.

14.02          Waiver by CYTOGEN or HOROSZIEWICZ of any single default or breach
or succession of defaults or breaches by the other shall not deprive the waiving
party of any right to terminate this Agreement arising out of any subsequent
breach.

14.03          All matters affecting the interpretation, validity and
performance of this Agreement shall be governed by the laws of the State of New
York.

14.04          (a) CYTOGEN shall indemnify and hold harmless HOROSZIEWICZ
against any and all actions, suits, claims, demands, prosecutions, liabilities
or judgments that may be brought,

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instituted or arise against HOROSZIEWICZ based on or arising out of an action by
CYTOGEN under this Agreement relating to the following:

               (i) the use by third parties of Antibody sold or supplied by
CYTOGEN;

               (ii) the manufacture, packaging, use, sale, or other distribution
of products containing Antibody by CYTOGEN;

               (iii) any representation made or warranty given by CYTOGEN with
respect to the Hybridoma or Antibody;

               (iv) the distribution or the use by CYTOGEN of the Hybridoma or
Antibody.

          (b) Upon the filing of any suit or claim, HOROSZIEWICZ shall permit
CYTOGEN's attorneys, at CYTOGEN's discretion and cost, to handle and control the
defense of any such claim or suit, provided that attorneys retained by
HOROSZIEWICZ at his own expense shall be permitted to join in any such defense.
No party shall settle any such claim or suit without the prior written consent
of the other party, which shall not be unreasonably withheld.

          (c) CYTOGEN shall not indemnify or hold harmless HOROSZIEWICZ against
any action, suit, claim, demand prosecution,

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liability or judgment that may be brought, instituted or arise against
HOROSZIEWICZ based on or arising out of any negligence or action of
HOROSZIEWICZ, including further research on Hybridoma or on Antibody.

          IN WITNESS WHEREOF, HOROSZIEWICZ and CYTOGEN have caused this
Agreement to be executed in duplicate; HOROSZIEWICZ personally and CYTOGEN by
its duly authorized officer.


/s/  Julius S. Horosziewicz, M.D., D.Msc
----------------------------------------
Julius S. Horosziewicz, M.D., DMSc.



April 20, 1989
----------------------------------------
Date



CYTOGEN CORPORATION



By:/s/  W.J. Ryan
   --------------------

Name:  W.J. Ryan
     ------------------

Title:  Vice President
      -----------------

April 18, 1989
-----------------------
Date

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