Exhibit 10.319

AMENDMENT TO RESTRICTED STOCK AGREEMENT

THIS AMENDMENT TO RESTRICTED STOCK AGREEMENT (this “Amendment”) is made as of
January     , 2008, by and between LIGAND PHARMACEUTICALS INCORPORATED, a
Delaware corporation (the “Company”), and              (“Participant”).

WHEREAS, the Company and Participant are parties to that certain Restricted
Stock Award Grant Notice and Restricted Stock Award Agreement dated as of
            , 2007 (the “Original Agreement”); and

WHEREAS, the Company and Participant desire to amend the Original Agreement as
set forth herein; and

WHEREAS, the Board of Directors of the Company has approved the adoption of this
Amendment.

NOW, THEREFORE, BE IT RESOLVED, that the Original Agreement is hereby amended as
follows:

1. The Vesting Schedule set forth in the Restricted Stock Award Grant Notice set
forth in the Original Agreement is hereby amended to read as follows:

 

Vesting Schedule:    One-third (1/3) of the Shares shall vest on the date that
is three days following the Company’s public release of its audited financial
statements for the fiscal year ending December 31, 2007, one third (1/3) of the
Shares shall vest on February 15, 2009, and one third (1/3) of the Shares shall
vest on February 15, 2010, subject to Participant’s continuous service with the
Company through each such date.

2. Except as expressly provided for in this Amendment, no other term or
provision of the Original Agreement is amended or modified in any respect.

IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the date
first set forth above.

 

COMPANY:     PARTICIPANT:

LIGAND PHARMACEUTICALS INCORPORATED

a Delaware corporation

    By:                  Name:          [Name of Participant]   Title: