SCHEDULE 13G

Amendment No. 5
XOMA CORP DEL
COMMON STOCK
Cusip #98419J107
Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:
[x] 	  Rule 13d-1(b)
[ ] 	  Rule 13d-1(c)
[ ] 	  Rule 13d-1(d)
Cusip #98419J107
Item 1: 	   	Reporting Person - FMR LLC
Item 2: 	   	(a)  	[ ]
   	   	(b)  	[ ]
Item 4: 	   	Delaware
Item 5: 	   	0
Item 6: 	   	0
Item 7: 	   	7,643,477
Item 8: 	   	0
Item 9: 	   	7,643,477
Item 11: 	   	6.390%
Item 12: 	   	HC
Cusip #98419J107
Item 1: 	   	Reporting Person - Abigail P. Johnson
Item 2: 	   	(a)  	[ ]
   	   	(b)  	[ ]
Item 4: 	   	United States of America
Item 5: 	   	0
Item 6: 	   	0
Item 7: 	   	7,643,477
Item 8: 	   	0
Item 9: 	   	7,643,477
Item 11: 	   	6.390%
Item 12: 	   	IN

Item 1(a). 	    	Name of Issuer:

  	  	          	XOMA CORP DEL

Item 1(b). 	    	Address of Issuer's Principal Executive Offices:

  	  	          	2910 Seventh St
  	  	          	Berkeley, CA 94710
  	  	          	USA

Item 2(a). 	     	 Name of Person Filing:

  	   	               	 FMR LLC

Item 2(b). 	     	 Address or Principal Business Office or, if None,
Residence:

  	   	               	 245 Summer Street, Boston, Massachusetts 02210

Item 2(c). 	     	 Citizenship:

  	   	               	 Not applicable

Item 2(d). 	     	 Title of Class of Securities:

  	   	               	 COMMON STOCK

Item 2(e). 	     	 CUSIP Number:

  	   	               	 98419J107

Item 3. 	    	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
or (c) and the
person filing, FMR LLC, is a parent holding company in accordance with
Section 240.13d-1(b)(1)(ii)(G).   (Note:  See Exhibit A).

Item 4. 	    	Ownership

  	  	     	(a)    Amount Beneficially Owned: 	7,643,477

  	  	     	(b)    Percent of Class: 	6.390%

  	  	     	(c)    Number of shares as to which such person has:

  	  	     	       (i)    sole power to vote or to direct the vote: 	0

  	  	     	       (ii)    shared power to vote or to direct the vote: 	0

  	  	     	       (iii)    sole power to dispose or to direct the
disposition of: 	7,643,477

  	  	     	       (iv)    shared power to dispose or to direct the
disposition of: 	0

Item 5. 	    	Ownership of Five Percent or Less of a Class.

  	    	     	Not applicable.

Item 6. 	    	Ownership of More than Five Percent on Behalf of Another
Person.

  	 Various persons have the right to receive or the power to direct the
receipt of dividends from, or the proceeds from the sale of, the COMMON
STOCK of XOMA CORP DEL. No one other person's interest in the COMMON STOCK
of XOMA CORP DEL is more than five percent of the total outstanding COMMON
STOCK.

Item 7. 	    	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent Holding Company.

  	    	     	See attached Exhibit A.

Item 8. 	    	Identification and Classification of Members of the Group.

  	    	     	Not applicable.

Item 9. 	    	Notice of Dissolution of Group.

  	    	  	Not applicable.

Item 10. 	    	Certifications.



By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired and are held in the ordinary
course of business and were not acquired and are not held for the purpose
of or with the effect of changing or influencing the control of the issuer
of the securities and were not acquired and are not held in connection with
or as a participant in any transaction having that purpose or effect.


Signature



After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete
and correct.

  	April 8, 2016
  	Date

  	/s/ Marc R. Bryant
  	Signature

  	Marc R. Bryant
  	 Duly authorized under Power of Attorney effective as of September 23,
2015, by and on behalf of FMR LLC and its direct and indirect subsidiaries*


* This power of attorney is incorporated herein by reference to Exhibit 24
to the Form 4 filed by FMR LLC on November 25, 2015, accession number:
0000315066-15-003312


Exhibit A


                 Pursuant to the instructions in Item 7 of Schedule 13G,
the following table lists the identity and Item 3 classification, if
applicable, of each relevant entity that beneficially owns shares of the
security class being reported on this Schedule 13G.


Entity 	ITEM 3 Classification
FMR CO., INC * 	IA


* Entity beneficially owns 5% or greater of the outstanding shares of the
security class being reported on this Schedule 13G.



                Abigail P. Johnson is a Director, the Vice Chairman, the
Chief Executive Officer and the President of FMR LLC.



                Members of the Johnson family, including Abigail P.
Johnson, are the predominant owners, directly or through trusts, of Series
B voting common shares of FMR LLC, representing 49% of the voting power of
FMR LLC. The Johnson family group and all other Series B shareholders have
entered into a shareholders' voting agreement under which all Series B
voting common shares will be voted in accordance with the majority vote of
Series B voting common shares. Accordingly, through their ownership of
voting common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed, under the
Investment Company Act of 1940, to form a controlling group with respect to
FMR LLC.



                Neither FMR LLC nor Abigail P. Johnson has the sole power
to vote or direct the voting of the shares owned directly by the various
investment companies registered under the Investment Company Act ("Fidelity
Funds") advised by Fidelity Management & Research Company ("FMR Co"), a
wholly owned subsidiary of FMR LLC, which power resides with the Fidelity
Funds' Boards of Trustees. Fidelity Management & Research Company carries
out the voting of the shares under written guidelines established by the
Fidelity Funds' Boards of Trustees.



                This filing reflects the securities beneficially owned, or
that may be deemed to be beneficially owned, by FMR LLC, certain of its
subsidiaries and affiliates, and other companies (collectively, the "FMR
Reporters"). This filing does not reflect securities, if any, beneficially
owned by certain other companies whose beneficial ownership of securities
is disaggregated from that of the FMR Reporters in accordance with
Securities and Exchange Commission Release No. 34-39538 (January 12, 1998).


RULE 13d-1(k)(1) AGREEMENT


                The undersigned persons, on April 8, 2016, agree and
consent to the joint filing on their behalf of this Schedule 13G in
connection with their beneficial ownership of the COMMON STOCK of XOMA CORP
DEL at March 31, 2016.


  	FMR LLC

  	By /s/ Marc R. Bryant
  	Marc R. Bryant
  	Duly authorized under Power of Attorney effective as of September 23,
2015, by and on behalf of FMR LLC and its direct and indirect subsidiaries*

  	Abigail P. Johnson

  	By /s/ Marc R. Bryant
  	Marc R. Bryant
  	Duly authorized under Power of Attorney effective as of October 12,
2015, by and on behalf of Abigail P. Johnson*


* This power of attorney is incorporated herein by reference to Exhibit 24
to the Form 4 filed by FMR LLC on November 25, 2015, accession number:
0000315066-15-003312