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[ * ] = 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 10.12
 AMENDMENT TO COLLABORATION AGREEMENT
BETWEEN
ONYX PHARMACEUTICALS, INC. AND BAYER CORPORATION
  Recitals
 Whereas,
 Whereas,
 Now Therefore,
 1. Capitalized Terms Previously Defined.
 2. Amendment of Defined Term: Collaboration Compound.
 1.9 Collaboration Compound
 [
* ] = 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.
 1.




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(a)
 (b)
 (c) [ * ] [ * ]
 3. Amendment of Defined Term: Post-Collaboration Compound.
 1.39 Post-Collaboration Compound
 (a)
 (b) [ * ]
 4. Additional Defined Term.
 1.55 Residual Field of Collaborative Research [ * ] [ * ] [ * ] [ * ] [ * ] [ * ]
 [
* ] = 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.
 2.




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##### 



[ * ]
 5. Additional Defined Term.
 1.56 Synteni Project
 6. Designation of Synteni Genes.
 7. Amendment to Paragraph 9. 6(d) .
 8. [ * ] Collaboration Compounds. [ * ] [ * ] [ * ]
 [
* ] = 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.
 3.




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[ * ]
 9. Development Guidelines.
 (a) [ * ] [ * ] [ * ] [ * ] [ * ] [
* ]
 (b) [ * ] [ * ] [ * ] [ * ]
 10. Acquisition of Compounds From [ * ]. [ * ] [ * ] [ * ] [ * ]
 11. Onyx and Bayers Rights to Conduct Independent Discovery.
 [
* ] = 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.
 4.




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##### 



12. Targets Removed from the Residual Field of Collaborative Research.
 13. Remaining Onyx Research Obligations. [ * ] [ * ] [ * ]
 14. New Name and Address for Notice for Bayer Corporation.
 
  [
* ] = 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.
 5.




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15. Full Force and Effect of Agreement.
 Onyx Pharmaceuticals, Inc.
    
    Bayer CorporationBy:
    
    /s/ Hollings C. Renton
    
    By:
    
    /s/ Michael J. BerendtName: Hollings C. Renton
    
    Name: Michael J. Berendt, Ph.D.Title: President and Chief Executive Officer
    
    Title: Sr. VP, Pharmaceutical ResearchDate: February 10, 1999
    
    Date: March 1, 1999
 [
* ] = 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.
 6.




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EXHIBIT E
 Assays and Materials
To be Delivered to Bayer by Onyx
 [ * ]
 [ * ]
 [ * ]
 [ * ]
 [ * ]
  [
* ] = 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.
 1.