<PAGE>

                                                                    EXHIBIT 10.3

                                            *** CERTAIN CONFIDENTIAL INFORMATION
                                            CONTAINED IN THIS DOCUMENT
                                            (INDICATED BY ASTERISKS) HAS BEEN
                                            OMITTED AND FILED SEPARATELY WITH
                                            THE SECURITIES AND EXCHANGE
                                            COMMISSION PURSUANT TO A REQUEST FOR
                                            CONFIDENTIAL TREATMENT UNDER 17
                                            C.F.R. SECTIONS 200.80(B)(4), 200.83
                                            AND 230.406.

                               AMENDMENT NO. 1 TO
                           EXCLUSIVE LICENSE AGREEMENT
                                     BETWEEN
                         THE UNIVERSITY OF MISSOURI AND
                                 SANTARUS, INC.

         This Amendment No. 1 (the "Amendment") to the Exclusive License
Agreement dated January 26, 2001 (the "License") between The Curators of the
University of Missouri (the "University") and Santarus, Inc. ("Santarus") is
made as of February 21, 2003 (the "Effective Date").

                                    RECITALS

         WHEREAS, the University and Santarus desire to amend certain terms of
the License as set forth herein.

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the covenants set forth herein, and
for other good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, the parties agree as follows:

         1.       AMENDMENT OF ARTICLE 15. Article 15 (including Sections 15.1
and 15.2) of the License is hereby amended in its entirety to read as follows:

                  "15. Project Status Reports.              ***

                                      ***
                                      ***
                                      ***
                                      ***                               Such
                  progress report shall also include any material deviations
                  from the Schedule of Events attached as Exhibit C."

         2.       AMENDMENT OF EXHIBIT C. Exhibit C to the License is hereby
replaced in its entirety with the revised Schedule of Events set forth on
Exhibit A hereto.

         3.       ACKNOWLEDGMENT. The University acknowledges and agrees that,
as of the Effective Date, Santarus has used commercially reasonable efforts to
develop and manufacture Licensed Products in accordance with Exhibit C of the
License and has to date otherwise satisfied all of the requirements of Section
5.1 of the License. In addition, the University waives any obligation on the
part of Santarus arising prior to the Effective Date to

*** Portions of this page have been omitted pursuant to a request for
Confidential Treatment and filed separately with the Commission.

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adhere to, or notify the University of any material deviations from, the
Schedule of Events in the original Exhibit C to the License.

         4.       MISCELLANEOUS.

                  a.       Except for the amendments set forth herein, all other
terms and conditions of the License shall remain in full force and effect.

                  b.       Capitalized terms used but not otherwise defined
herein shall have the meanings assigned to them in the License.

                  c.       This Amendment will be interpreted and construed in
accordance with the laws of the State of *** , excluding any choice of law rules
that would direct the application of the laws of another jurisdiction.

*** Portions of this page have been omitted pursuant to a request for
Confidential Treatment and filed separately with the Commission.

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IN WITNESS WHEREOF, both the University and Santarus have executed this
Amendment as of the date set forth above.

SANTARUS, INC.

By: /s/ Gerald T. Proehl
    -----------------------------------

Name: Gerald T. Proehl

Title: President and CEO

THE CURATORS OF THE UNIVERSITY OF MISSOURI

By: /s/ Thomas R. Sharpe
    -----------------------------------

Name:  Thomas R. Sharpe, Ph.D.
Title: Executive Director Office of Technology & Special Projects
<PAGE>

                                    Exhibit A


                                    Exhibit C

                               Schedule of Events


January 26, 2001  Sign definitive licensing agreement


Qtr 1 2001        Transfer IND


Qtr 2 2001        Develop formulation alternatives, place on stability

                  Begin sublicense negotiations with other PPI company(ies)


Qtr 3 2001        Identify and select contract manufacturing organization
                  for omeprazole active pharmaceutical ingredient (API)

                  Identify and select contract manufacturing organization
                  for drug product


Qtr 4 2001        Prototype formulation placed on feasibility stability

                  Establish analytical lab for quality control


Qtr 1 2002        Determine optimal formulation


Qtr 2 2002        Sign sublicense agreement

                  Begin discussions with various pharmaceutical companies on
                  co-development/co-promotion agreement


Qtr 3 2002        ***


Qtr 4 2002        ***


Qtr 1 2003        ***


Qtr 2 2003        ***


Qtr 3 2003        ***


Qtr 4 2003        ***


Qtr 1 2004        ***


Qtr 2 2004        ***


Qtr 3 2005        ***


Qtr 4 2005        ***



*** Portions of this page have been omitted pursuant to a request for
Confidential Treatment and filed separately with the Commission.