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                                                                    Exhibit 10.1

   [Note: Certain portions of this document have been marked with "[c.i.]" to
 indicate confidential information for which confidentiality has been requested.
    The confidential portions have been omitted and filed separately with the
                      Securities and Exchange Commission.]

                      FIRST AMENDMENT TO LICENSE AGREEMENT

         Amendatory Agreement, dated April 1, 1997 between National Jewish
Center for Immunology and Respiratory Medicine ("NJC"), a non-profit educational
research organization organized under the laws of Colorado and having its
principal office at 1400 Jackson Street, Denver, Colorado 80206, and Cadus
Pharmaceutical Corporation ("CADUS"), a corporation organized under the laws of
Delaware, and having its principal place of business at 777 Old Saw Mill River
Road, Tarrytown, New York 10591-6705.

                              W I T N E S S E T H:

         WHEREAS, NJC and CADUS are parties to a License Agreement dated
November 1, 1994 (the "License Agreement");

         WHEREAS, NJC and CADUS wish to amend the License Agreement in certain
respects;

         NOW THEREFORE, in consideration of the premises and the mutual
covenants set forth herein, the parties hereto hereby agree as follows:

         1. Section 1.7 of the License Agreement is hereby amended in its
entirety to read as follows: 

                  "1.7. "Cambier Future Technologies" shall mean all
proprietary information

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owned or possessed by NJC (without restriction from any third party which would
preclude a license to CADUS) relating to products, processes, know-how and
inventions that relate to mammalian cell and/or enzyme-based assays useful in
identifying compounds that regulate cellular transduction pathways, that is
conceived of or reduced to practice during the term of this Agreement and that
is either solely invented by Dr. John Cambier or jointly invented by Dr. Cambier
and any third party or parties (including Dr. Gary Johnson), and further that
does not infringe one or more claims, as they may be amended and as they may
issue, as set forth in any of the [c.i.] U.S. patent applications listed in
Exhibit A."

         2. Section 1.10 of the License Agreement is hereby amended in its
entirety to read as follows: 

                 "1.10. "Johnson Future Technologies" shall mean all
proprietary information owned or possessed by NJC (without restriction from any

third party which would preclude a license to CADUS) relating to products,
processes, know-how and inventions that relate to mammalian cell and/or
enzyme-based assays useful in identifying compounds that regulate cellular
transduction pathways, that is conceived of or reduced to practice during the
term of this Agreement and that is either solely invented by Dr. Gary Johnson or
jointly invented by Dr. Johnson and any third party or parties (including Dr.
John Cambier), and further that does not infringe one or more claims, as they
may be amended and as they may issue, as set forth in any of the [c.i.] U.S.
patent applications listed in Exhibit A."

         3. Sections 1.12 through 1.18 are hereby added to the License
Agreement, which read as follows:

                  "1.12 "Exclusive Cambier Future Technologies" shall mean
Cambier Future

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Technologies with respect to which no employees of NJC (other than Drs. Cambier
and Johnson) were co-inventors.

                  1.13. "Non-Exclusive Cambier Future Technologies" shall mean
Cambier Future Technologies with respect to which employees of NJC (other than
Drs. Cambier and Johnson) were co-inventors.

                  1.14. "Exclusive Johnson Future Technologies" shall mean
Johnson Future Technologies with respect to which no employees of NJC (other
than Drs. Cambier and Johnson) were co-inventors.

                  1.15. "Non-Exclusive Johnson Future Technologies" shall mean
Johnson Future Technologies with respect to which employees of NJC (other than
Drs. Cambier and Johnson) were co-inventors.

                  1.16. "Cambier Option Period" shall mean the period commencing
on the Effective Date and ending on [c.i.].

                  1.17. "Johnson Option Period" shall mean the period commencing
on the Effective Date and ending on [c.i.].

                  1.18. "Future Technologies" shall mean Cambier Future
Technologies and Johnson Future Technologies."

         4. ARTICLE 5 of the License Agreement is hereby amended in its entirety
to read as follows:

                      "ARTICLE 5 - FUTURE TECHNOLOGIES

                  5.1 Notice of Future Technologies. NJC shall provide to CADUS
notice of (i) each Cambier Future Technology conceived of or reduced to practice
during the Cambier Option

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Period and (ii) each Johnson Future Technology conceived of or reduced to
practice during the Johnson Option Period, together with an invention disclosure
relating thereto, within fifteen (15) days after receiving an invention
disclosure with respect thereto. Within thirty (30) days after the date hereof,
NJC shall provide to CADUS notice of each Future Technology conceived of or
reduced to practice prior to the date hereof, together with an invention
disclosure relating thereto.

                  5.2 Option to License Future Technologies. NJC hereby grants
to CADUS an option to acquire an exclusive, worldwide license to each (i)
Exclusive Cambier Future Technology conceived of or reduced to practice during
the Cambier Option Period and (ii) Exclusive Johnson Future Technology conceived
of or reduced to practice during the Johnson Option Period. NJC hereby grants to
CADUS an option to acquire a non-exclusive, worldwide license to each (i)
NonExclusive Cambier Future Technology conceived of or reduced to practice
during the Cambier Option Period and (ii) each Non-Exclusive Johnson Future
Technology conceived of or reduced to practice during the Johnson Option Period.
The term of each such option grant shall be for a period of [c.i.] commencing on
the date NJC provides CADUS with a notice pursuant to Section 5.1 with respect
to the particular Future Technology, together with an invention disclosure
relating thereto. CADUS shall be deemed to have effectively exercised any such
option if CADUS sends written notice of its exercise of such option to NJC
within the [c.i.] option period. Upon the exercise by CADUS of such an option
with respect to a particular Future Technology, such Future Technology shall be
deemed NJC Technical Information for purposes of this Agreement.

                  5.3. Patent Administration Expenses. CADUS shall reimburse NJC
for (i) all patent administration expenses ("Patent Costs"), including legal
expenses, incurred through March 31, 1997, for all patent applications for
Future Technologies licensed by CADUS hereunder and (ii)

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the costs associated with the transfer of patent files related to Future
Technologies licensed by CADUS hereunder. NJC hereby represents that the total
patent administration expenses for all patent applications for all Future
Technologies incurred through January 31, 1997 was $44,711.50. If NJC enters
into an agreement with a third party pursuant to which NJC licenses a
Non-Exclusive Cambier Future Technology or a Non-Exclusive Johnson Future
Technology to such third party, NJC shall promptly notify CADUS and shall, at
NJC's option, either (a) pay to CADUS within thirty (30) days of the effective
date of such license agreement the new licensee's proportional share of all
Patent Costs paid by CADUS up to that date, or (b) grant CADUS a credit
applicable to any payments due from CADUS to NJC after such date equal to the
new licensee's proportional share of all Patent Costs paid by CADUS up to that
date. In addition, NJC shall ensure that the new licensee shall be obligated,
under its license agreement with NJC, to pay, from and after the effective date
of such license agreement, its proportional share of all Patent Costs for the
licensed NonExclusive Cambier Future Technology or Non-Exclusive Johnson Future

Technology, as the case may be. For purposes of this Section 5.3, a licensee's
"proportional share" shall be calculated by multiplying the Patent Costs
incurred by NJC or CADUS by a fraction, the numerator of which is one and the
denominator of which is the number of licensees of NJC with respect to the
licensed Non-Exclusive Cambier Future Technology or Non-Exclusive Johnson Future
Technology, as the case may be.

                  5.4. Patent Administration. After March 31, 1997, NJC shall
not prepare or file patent applications with respect to any Future Technology
until the [c.i.] option period with respect to such Future Technology has
expired without CADUS exercising its option with respect thereto. If a patent
application must be filed on an expedited basis to preserve intellectual
property rights

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with respect to a Future Technology, NJC shall notify CADUS thereof as soon as
practicable after it becomes aware of the need to file the same. Notwithstanding
anything to the contrary in this Section 5.4, if CADUS does not exercise its
option to license any such Future Technology at least [c.i.] prior to the date
such patent application must be filed, NJC shall have the right to file a patent
application with respect to such Future Technology to preserve intellectual
property rights relating thereto and CADUS shall pay the Patent Costs with
respect thereto if CADUS exercises its option to license such Future Technology;
provided, however, that Section 9.1 hereof shall apply with respect to such
Future Technology if CADUS exercises its option to license such Future
Technology.

                  5.5. Publication. If NJC intends to publish or present its
work relating to a Future Technology, it shall so notify CADUS as soon as
practicable after it becomes aware of such proposed publication or presentation.
If CADUS exercises its option to license such Future Technology, such Future
Technology shall be deemed NJC Technical Information and its publication or
presentation shall be governed by Section 23.2 hereof."

         5. Section 6.2 of the License Agreement is hereby amended in its
entirety to read as follows:

                  "6.2. Payments Credited Against Royalties. Payments made by
CADUS to NJC pursuant to Sections 6.1, 8.1(c) and 8.1(e) shall be credited
against amounts payable pursuant to Section 8.1(a) hereof, except that the first
[c.i.] paid under Section 8.1(c) shall not be credited."

         6. A Section 8.1(e) is hereby added to the License Agreement, which
reads as follows:

                  "8.1(e) On April 1, 1997 and on April 1, 1998, CADUS shall pay
to NJC (i) [c.i.] if both Gary Johnson and John Cambier are then consultants to
CADUS and also employed by

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NJC and both of their laboratories at NJC are operating or (ii) [c.i.] if only
one of Gary Johnson or John Cambier is then a consultant to CADUS and also
employed by NJC and his laboratory at NJC is operating."

         7. Section 22.1 of the License Agreement is hereby amended by replacing
the phrase "NJC Technical Information" in the caption and in the text thereof
with the phrase "NJC Technical Information and Future Technologies."

         8. Except as amended hereby, the terms and conditions of the License
Agreement are confirmed. The License Agreement, as so amended, shall continue in
full force and effect.

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the date first above written.

                     NATIONAL JEWISH CENTER FOR
                     IMMUNOLOGY AND RESPIRATORY MEDICINE

                     By: /s/ Judith A. Baskett
                         ---------------------------------
                          Judith A. Baskett,
                          Director Research Administration
                          and Technology Transfer

                     CADUS PHARMACEUTICAL CORPORATION

                     BY: /s/ Philip N. Sussman
                         ---------------------------------
                          Philip N. Sussman,
                          Vice President, Corporate Development

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