Letter relating to Notice under and Amendment to the Collaboration Agreement



 [ * ] = 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. 
 EXHIBIT 10.4 
 August 20, 2007 (the “Letter Effective Date”) 
 Pamela A. Simonton 
 Senior Vice President, Patents and Licensing 

Exelixis, Inc. 
 170 Harbor Way 
 P.O. Box 511 
 South San Francisco, CA94083-0511 
  

	Re:	Extension of Collaborative Research Period; BMS Option to Further Extend Collaborative Research Period 

 Dear Ms. Simonton: 
 Reference is hereby made to that certain
Collaboration Agreement (the “Agreement”) dated as of December 5, 2005, by and between Exelixis, Inc., a Delaware corporation having its principal place of business at 170 Harbor Way, P.O. Box 511, South San Francisco,
California 94083-0511 (“Exelixis”), and Bristol-Myers Squibb Company, a Delaware corporation headquartered at 345 Park Avenue, New York, NY 10154 (“BMS”). Capitalized terms used in this letter
agreement (this “Letter”) that are not otherwise defined herein shall have the meanings given to them in the Agreement. 
 In
connection with the Collaboration between the Parties conducted pursuant to the Agreement, this Letter is intended to (a) provide notice to Exelixis of BMS’ desire to extend the Collaborative Research Period for an additional one-year
period (i.e., through January 11, 2009) pursuant to Section 2.5 of the Agreement, and (b) set forth the Parties’ mutual understandings with respect to BMS’ option to extend the Collaborative Research Period by an additional
one-year period from January 12, 2009 through January 11, 2010. 
  

	 	1.	BMS hereby notifies Exelixis that the Collaborative Research Period shall be extended by one additional year (i.e. through January 11, 2009) pursuant to Section 2.5 of the
Agreement. A revised Research Plan, which includes activities that will be performed by the Parties in the period from January 12, 2008 through January 11, 2009, has been approved by the JRC in accordance with Section 2.6 of the
Agreement. 

  

	 	2.	 Exelixis hereby agrees that, notwithstanding the last sentence of Section 2.5 of the Agreement, BMS shall have the unilateral option to extend the
Collaborative Research Period by an additional one-year period, from January 12, 2009 through January 11, 2010, with a level of research funding to be determined by the JRC pursuant to Section 2.6, and with research support payments
to be made to Exelixis pursuant to Section 7.2 in the same manner as for the period from January 12, 2008 through January 11, 2009; provided that, in such event, the FTE Rate shall increase on January 1, 2010 by an amount equal
to the Consumer Price Index (for the San Francisco, California 











	 	 
area as reported as of January 1st in such year when compared to the comparable statistic for January 1st of the preceding year).



  

	 	3.	BMS hereby agrees that, notwithstanding the language in [ * ] of the Agreement to the contrary, as of the Letter Effective Date, Exelixis shall not have any obligation to
[ * ]; provided, however, that: (i) in the event that Exelixis desires to [ * ], (A) Exelixis shall notify BMS, no later than ninety (90) days prior to the proposed date of such [ * ], of the [ * ], as well
as the rationale for such [ * ], in order to allow BMS the opportunity to assess the effects of any such [ * ] (and any benefits or obligations associated therewith), subject to [ * ], and (B) in the event that BMS desires
[ * ], Exelixis shall use commercially reasonable efforts (without the necessity of providing any consideration) to facilitate any such [ * ] by BMS; (ii) Exelixis shall also notify BMS if Exelixis [ * ]; and
(iii) where any such [ * ] provides for a [ * ], Exelixis shall not, without BMS’ prior written consent, [ * ]. 

 If you are in agreement with the terms and conditions of this Letter, please execute and return the enclosed duplicate copy of this Letter. 
  


			
	Sincerely,
	
	BRISTOL-MYERS SQUIBB COMPANY
		
	By:	 	/s/ Michael Levy
	Title:	 	VP, Alliance Management


 ACKNOWLEDGED AND AGREED 
 as of August 20, 2007 
  

			
	EXELIXIS, INC.
		
	By:	 	/s/ George Scangos
	Title:	 	President & CEO

  

 [ * ] = 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.