<PAGE>

                                                                 EXECUTION COPY
                                                                 --------------

* The confidential material contained herein has been omitted and filed
separately wth the Commission.

                  COLLABORATIVE RESEARCH AND OPTION AGREEMENT

                               December 30, 1995

         THIS COLLABORATIVE RESEARCH AND OPTION AGREEMENT ("Agreement") is made
as of the date first written above ("Effective Date") by and between Magainin
Pharmaceuticals Inc., a Delaware corporation, having a place of business at 5110
Campus Drive, Plymouth Meeting, Pennsylvania 19462 ("Magainin") and Genentech
Inc., a Delaware corporation having a place of business at 1 DNA Way South San
Francisco, California 94080 ("Genentech").

                                   RECITALS

        WHEREAS, Magainin has undertaken certain research efforts relating to
the role of IL-9 in asthma, and

        WHEREAS, Genentech desires to conduct research to determine the role of
IL-9 in reducing the symptoms of asthma, and

        WHEREAS, Genentech desires to receive from Magainin an exclusive option
to negotiate a development and commercialization agreement, and

        WHEREAS, Magainin is interested in providing such an option to
Genentech,

        NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein, and intending to be legally bound hereby, the Parties hereto
agree as follows:

        1 DEFINITIONS

          1.1  "Compound" shall mean a protein that directly or indirectly
               ----------
inhibits the production, action or effect of IL-9.

          1.2  "Field" shall mean the prevention or treatment of human asthma
               -------
and bronchial hyperresponsiveness by the therapeutic use of a Compound.

          1.3  "Know-How" shall mean information, expertise and intellectual
               ----------
property that relates to Compound

          1.5  "Licensed Patent Rights" shall mean all current and future
               ------------------------
patents and patent applications throughout the world (including all extensions,
substitutions, reissues, and reexaminations of the foregoing) having claims
directed to any Compound in the Field (a) that Magainin owns (in whole or in
part) or controls and has the right to license or sublicense or (b) that result
from research performed under the Research Plan.

          1.6  "Reagents" shall mean reagents listed in Appendix B.
               ----------                               ----------
<PAGE>

           1.7  "Research" shall mean research work of the Parties on Compound.
                ----------
           1.8  "Research Plan" shall mean the research plan attached to this
                ---------------
Agreement as Appendix A.

           1.9  "Research Term" shall mean the period of time commencing upon
                ---------------
the Effective Date and terminating on December 31, 1999, unless the affinity of
Magainin's antibody is found to be worse than that specified in Research Plan,
in which case, the Parties agree to mutually extend the Research Term.

           1.10 "Results" shall mean any and all materials, information,
                ---------
discoveries, ideas, Know-How, data and techniques that are made, created or
reduced to practice in the course of, or as a result of, the Research.

           1.11 "Stock Purchase Agreement" shall mean the agreement attached as
                --------------------------
Appendix C.
----------
           1.12 "Third Party" shall mean any person other than a Party to this
                -------------
Agreement.

        2. RESEARCH

           2.1  Research Plan - During the Research Term, Magainin and
                -------------
Genentech shall jointly conduct Research pursuant to the Research Plan.

                Each of the Parties shall allocate sufficient resources,
including, without limitation, personnel, equipment, supplies, reagents and
facilities, to conduct Research as set forth in the Research Plan. Each Party
shall be responsible for its own expenses and costs incurred under the Research
Plan.

                Magainin shall provide to Genentech at no cost reasonable
quantities of Reagents that may be requested from time to time under the
Research Plan.

           2.2  Exclusive Research Relationship - During the Research Term,
                -------------------------------
neither Party may conduct research on Compound with any Third Party without the
prior written consent of the other Party.

          2.3   Intellectual Property - All patents and patent applications that
                ---------------------
result from sole Genentech inventions under the Research Plan, shall be
exclusively owned by Genentech. Any joint inventions shall be owned by the
Parties jointly. All title and interest in any Results obtained by Genentech
under the Research Plan will belong to Genentech, although Genentech shall
provide Magainin free access to and use of Results. If for any reason the
Parties do not enter into a research and development agreement as contemplated
by Section 3.1 hereof, Genentech shall negotiate in good faith with Magainin to
grant Magainin a license for any

                                       2
<PAGE>

Genentech intellectual property developed under the Research Plan either solely
or jointly with Magainin.

        3. OPTION

           3.1  Option Grant - Magainin hereby grants to Genentech an exclusive
                ------------
option to enter into an agreement to develop and commercialize any and all
Compounds in the Field, exercisable for one hundred twenty (120) days after the
end of the Research Term. Such agreement shall include: (a) the grant by
Magainin to Genentech of an exclusive worldwide sublicensable license (the
"License") under Magainin's Licensed Patent Rights and Know-How to make, have
made, use, sell, offer for sale and import Compound in the Field; (b) maximum
aggregate payments by Genentech under such agreement for any signing fee,
sponsored research and development, development and approval milestones, and all
other payments of any form except royalties, shall not exceed $35.0 million,
which may be paid in one or more of the following forms, a loan, equity
investment pursuant to the terms of the Stock Purchase Agreement or cash; and
(c) a royalty of up to ()% of net sales of Compound in the Fields prior to     *
Third Party royalty offsets to be negotiated. The precise royalty to be agreed
upon will depend on the relative intellectual property contribution (both Know-
How and patents) of Magainin to the development and commercial exclusivity of a
Compound in the Field. The Parties have discussed Genentech's standard deal
structure of off balance sheet financing and back-end loaded deals weighted
toward approval milestones. The Parties recognize that the final negotiated deal
must be fair to both Parties consistent with the facts (e.g., scope of
collaboration contemplated) and data (e.g., Research Plan results) available at
the time of the negotiation and conform to the broad deal outline and structure
noted above The Parties agree to negotiate in good faith the other terms of such
development and commercialization agreement.


           Magainin shall notify Genentech of any serious negotiations with
Third Parties involving
(                                                                          )   *
in the prevention or treatment of human asthma and bronchial
hyperresponsiveness, and will negotiate in good faith with Genentech to enter
into a collaboration in such area.

           3.2  Equity Purchase - Genentech shall make an equity investment in
                ---------------
Magainin as provided for in the Stock Purchase Agreement.

        4. LICENSES

           4.1  License Grant - During the Research Term, and only to the extent
                -------------
necessary to conduct its activities under the Research Plan,. Magainin grants to
Genentech a license under Licensed Patent Rights and Know-How in the Field


                                       3



                                         *  THE CONFIDENTIAL MATERIAL CONTAINED
                                            HEREIN HAS BEEN OMITTED AND HAS BEEN
                                            FILED SEPARATELY WITH THE COMMISSION

<PAGE>

        5. FUTURE RIGHTS

           5.1  To the extent Magainin obtains rights to a Compound outside of
the Field, and Genentech wishes to collaborate with Magainin, Magainin agrees to
negotiate in good faith with Genentech to enter into a collaboration in such
area.

        6. TERM AND TERMINATION

           6.1  Term - The Agreement shall commence upon the Effective Date and
                ----
shall expire at the end of the Research Term, unless extended by the written
agreement of the Parties.

           6.2  Termination - Genentech may terminate this Agreement at any time
                -----------
during the Research Term upon thirty (30) days written notice to Magainin

                Upon the termination of the Agreement, all licenses granted to
Genentech shall terminate.

        7. CONFIDENTIAL INFORMATION, PUBLICITY

           7.1  Requirement of Confidentiality -- This Agreement contemplates
                ------------------------------
the exchange of certain confidential and proprietary information by one Party
(the "Disclosing Party") to the other Party (the "Receiving Party") during the
term of this Agreement (the "Confidential Information) and the development of
certain confidential and proprietary information in the course of the
collaboration by the Parties hereunder, including, without limitation, Know-How
and Results (the "Research Information") (the Confidential Information and
Research Information are collectively referred to hereinafter as the
"Information"). With respect to the Information, each Party, shall:

                      (a) use such Information only for the purpose of
           performing its duties or exercising its rights under this Agreement
           and for no other purpose, subject to the terms and conditions of this
           Agreement;

                      (b) safeguard such Information against disclosure to
           others with the same degree of care as it exercises with its own data
           of a similar nature, but not less than a reasonable degree of care;
           and

                      (c) not disclose such Information to others (except to its
           employees, or consultants, who are bound to the Receiving Party by a
           like obligation of confidentiality and restriction on use) without
           the express written consent of the other Party.



                                       4
<PAGE>

           7.2  Confidential Information - The commitments set forth in Section
                ------------------------
7.1 shall be of five (5) years' duration from date of disclosure and shall not
impose any obligation upon a Party with respect to any portion of the
Information which such Patty can establish:

                (a) Was known to the Receiving Party prior to the receipt of the
        same directly or indirectly from the Disclosing Party; or

                (b) Is now, or becomes in the figure, public knowledge other
        than through acts or omissions of the Receiving Party; or

                (c) Is disclosed at any time to the Receiving Party by a Third
        Party that had a lawful right to disclose it; or

                (d) Is subsequently developed by either Party independent of the
        Information received hereunder; or

                (e) Has been or is subsequently disclosed by the Disclosing
        Party to any Third Party on a non-confidential basis.

          7.3  Publicity and News Releases -- Except as may be required by
               ---------------------------
applicable laws, rules or regulations, neither Party will originate any
publicity, news release, or other public announcement, written or oral, whether
to the public press or otherwise, relating to any amendment hereto or to
performance hereunder or the existence of this Agreement or an arrangement
between the Parties relating to this Agreement, without the prior written
approval of the other Party. In the event disclosure is required by applicable
law, rules or regulations, then the Party required to so disclose such
information shall, to the extent possible, provide to the other Party for its
approval (such approval not to be unreasonably withheld), a written copy of such
public announcement at least five (5) business days prior to disclosure.
Notwithstanding the foregoing, Magainin shall have the right to make a press
release with respect to its entering into this Agreement. Magainin shall provide
to Genentech a copy of the proposed press release no less than three (3)
business days prior to its proposed release. The contents of such press release
shall be subject to Genentech's consent, such consent not to be unreasonably
withheld.

        8 MISCELLANEOUS

          8.1  Entire Agreement Amendment - This Agreement, together with the
               --------------------------
Stock Purchase Agreement attached hereto as Appendix C and the documents
                                            ----------
contemplated thereby, constitute the entire Agreement between the Parties
relating to the subject matter hereof and supersede all previous writings and
understandings whether oral or written, relating to such subject matter. This
Agreement may not be amended, supplemented or otherwise modified except by an
instrument in writing signed by both Parties that specifically refers to this
Agreement.


                                       5
<PAGE>

          8.2  Notices -- Any notice or other communication required or
               -------
permitted under this Agreement shall be sent by certified mail or courier
service, charges prepaid, or by facsimile transmission, to the address or
facsimile number specified below:

               If to Magainin:

                      Magainin Pharmaceuticals Inc
                      5110 Campus Drive
                      Plymouth Meeting, PA 19462
                      Fax No: 610-941-5399
                      Attention: Corporate Secretary

               If to Genentech:

                      Genentech, Inc
                      1 DNA Way
                      South San Francisco, CA 94080
                      Fax No: 650-952-9881
                      Attention: Corporate Secretary

or to such other address or facsimile number as the person may specify in a
notice duly given to the sender as provided herein. A notice will be deemed to
have been given upon its deposit in the United States mail or with a courier
service, or, in the case of facsimile transmission, upon machine confirmation
that such transmission has been received.

           8.3 Headings and Reference -- All section headings contained in this
               ----------------------
Agreement are for convenience of reference only and shall not affect the meaning
or interpretation of this Agreement. Unless the context requires otherwise, all
references in this Agreement to any section, exhibit or appendix shall be deemed
and construed as reference to a section of, or an exhibit or appendix to, this
Agreement, any such exhibits and appendices are hereby incorporated in this
Agreement by such reference.

           8.4 Assignment and Binding Effect -- This Agreement and the licenses
               -----------------------------
herein granted shall be binding upon and inure to the benefit of the successors
and assigns of the Parties hereto. Neither Party may assign any of its rights,
or delegate any of its obligations, under this Agreement without the written
consent of the other Party. Notwithstanding the foregoing, either Party may,
without obtaining the consent of the other Party, assign this Agreement to any
Affiliate or to any corporation with which it may merge or consolidate, or to
which it may transfer all or substantially all of its assets to which this
Agreement relates.

           8.5 Severability -- In the event that any provision of this
               ------------
Agreement shall be held illegal, void or ineffective, the remaining portions
hereof shall remain in full force and effect so long as such remaining portions
do not materially change the intent of this Agreement or the right or
obligations of the Parties hereunder. If any provision of this Agreement is in
conflict with any applicable statute or law in any jurisdiction, then such
provision shall be

                                       6
<PAGE>

deemed inoperative in such jurisdiction to the extent of such conflict and the
Parties will renegotiate the affected provisions of this Agreement to resolve
any inequities. It is the intention of the Parties that, if any court or other
tribunal construes any provision or clause of this Agreement, or any portion
thereof, to be illegal, void or unenforceable because of the duration of such
provision or the area or matter covered thereby, such court shall reduce the
duration, area or matter of such provision and enforce such provision in its
reduced form.

           8.6  No Conflicts -- Each Party represents and warrants to the other
                ------------
that it has the lawful right to enter into and perform its obligations under
this Agreement, and that the terms of the Agreement do not conflict with any
other obligations of such Party.

           8.7  Governing Law - This Agreement shall be governed in all respects
                -------------
by the laws of the State of New York applicable to contracts between New York
residents entered into and to be performed entirely within the State of New
York.

           8.8  Counterparts; Facsimile -- This Agreement may be executed in any
                -----------------------
number of counterparts and by facsimile, each of which may be executed by fewer
than all of Parties hereto, each of which shall be enforceable against the
Parties actually executing such counterparts, and all of which together shall
constitute one instrument.


                           [signature page follows]



                                       7
<PAGE>

        IN WITNESS WHEREOF, the Parties, through their authorized officers, have
duly executed this Agreement as of the date first written above.



MAGAININ PHARMACEUTICALS INC                 GENENTECH, INC.



By: /s/   Michael R. Dougherty               By: /s/   W. D. Young
   ---------------------------                  ------------------------------
   Name:  Michael R. Dougherty                  Name:  William D. Young
   Title: President and Chief                   Title: Chief Operating Officer
          Executive Officer
<PAGE>

                                                                      APPENDIX A
                                                                      ----------


        Genentech Program to Evaluate the Role of IL-9 in Murine Asthma

***














                                       1


                                        *  THE CONFIDENTIAL MATERIAL CONTAINED
                                           HEREIN HAS BEEN OMITTED AND HAS BEEN
                                           FILED SEPARATELY WITH THE COMMISSION


<PAGE>

                                                                      Appendix B



                             Reagent List 12-29-98
                             ---------------------

***


















                                        *  THE CONFIDENTIAL MATERIAL CONTAINED
                                           HEREIN HAS BEEN OMITTED AND HAS BEEN
                                           FILED SEPARATELY WITH THE COMMISSION
<PAGE>

                                  APPENDIX C
                                  ----------
                   Stock Purchase Agreement between Magainin
       Pharmaceuticals Inc. and Genentech Inc., dated December 30, 1998





*This agreement is being filed separately as Exhibit 10.33 to the Registrant's
Form 10-K405/A.