<PAGE>
EXHIBIT 10.31
[/\#/\] CERTAIN CONFIDENTIAL INFORMATION CONTAINED
IN THIS DOCUMENT, MARKED BY BRACKETS, HAS BEEN
OMITTED AND FILED SEPARATELY WITH THE SECURITIES
AND EXCHANGE COMMISSION PURSUANT TO RULE 24B-2
OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.
AMENDMENT NO. 1 TO PATENT AND TECHNOLOGY LICENSE AGREEMENT
This Amendment No. 1 to Patent and Technology License Agreement
(FIRST
AMENDMENT) is made and entered into as of
February 10, 2004 by and between
Myogen, Inc. (LICENSEE) and the Board of
Regents (BOARD) of the University of
Texas System (SYSTEM).
RECITALS
A. LICENSEE and BOARD entered into a Patent
and Technology License Agreement
effective as of January 1, 2002 (LICENSE
AGREEMENT).
B. LICENSEE and BOARD wish to further amend
the terms of the LICENSE AGREEMENT
as set forth below.
NOW, THEREFORE, it is hereby agreed as
follows:
1. Section 5.1c of the LICENSE AGREEMENT
shall be revised to read in its
entirety as follows:
"milestone fees according to the table below, due and payable
within 30
days of each milestone event for the first
LICENSED PRODUCT or IDENTIFIED
PRODUCT to achieve such milestone event,
[/\#/\], provided however, if LICENSEE
pays a milestone fee under the 1999
AGREEMENT for a milestone event listed
below, such payment is creditable toward
the milestone fee due for the same
milestone event for the same LICENSED
PRODUCT or IDENTIFIED PRODUCT pursuant to
this Section 5.1c:
<Table>
<Caption>
MILESTONE
EVENT
MILESTONE FEE
------------------------------------------------
-------------------
<S>
<C>
The date
the first patient is dosed in the first
[/\#/\]
Phase III
clinical trial
NDA
approval in the U.S. for a LICENSED
[/\#/\]
PRODUCT or
IDENTIFIED PRODUCT
