UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G 

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Item 1.

(a)          Name of Issuer: XOMA Corporation (the “Issuer”).

(b)          Address of the Issuer’s Principal Executive Offices: 2910 Seventh Street, Berkeley, California 94710.

Item 2.          

(a)          Name of Person Filing: This joint statement on Schedule 13G is being filed by Peter Kolchinsky, RA Capital Management, LLC, and RA Capital Healthcare Fund, L.P., who are collectively referred to herein as the “Reporting Persons.” Mr. Kolchinsky (the “Manager”) is the manager of RA Capital Management, LLC (“Capital”), which is the investment adviser and sole general partner of RA Capital Healthcare Fund, L.P. (“Fund”) and serves as the investment adviser to a separate discretionary account. The Reporting Persons have entered into a Joint Filing Agreement, dated as of the date hereof, a copy of which is filed with this Schedule 13G as Exhibit 1 (which is incorporated herein by reference), pursuant to which the Reporting Persons have agreed to file this statement jointly in accordance with the provisions of Rule 13d-1(k) under the Act.

(b)          Address of Principal Business Office: The principal business office of the Reporting Persons with respect to the shares reported hereunder is 20 Park Plaza, Suite 1200, Boston, MA 02116.

(c)          Citizenship: Capital is a Massachusetts limited liability company. The Fund is a Delaware limited partnership. The Manager is a United States citizen.

(d)          Title and Class of Securities: Common stock (“Common Stock”).

(e)          CUSIP Number: 98419J107.

Item 3.          If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

Not applicable.

Item 4.          Ownership:

As of January 31, 2013, the Reporting Persons, in the aggregate, beneficially own 6,698,558 shares of the Common Stock of the Issuer, representing approximately 8.2% of such class of securities. The Reporting Persons have the right to purchase an additional 687,879 shares of Common Stock pursuant to the terms of the Warrant to Purchase Common Stock issued on March 09, 2012, which are not exercisable to the extent that, following such exercise, the total number of shares of Common Stock then beneficially owned by the Reporting Persons does not exceed 4.999% of the total number of then issued and outstanding shares of Common Stock (including for such purpose the shares of Common Stock issuable upon such exercise). This 4.999% limitation shall cease to apply from and after the date fourteen days prior to the Expiration Date. The beneficial ownership of each Reporting Person is as follows: (i) Fund beneficially owns 3,921,042 shares of Common Stock, representing approximately 4.8% of the class and (ii) Capital, as the investment adviser and sole general partner of the Fund and investment adviser to an account owned by a separate investment vehicle which holds shares of the Issuer's Common Stock, and Mr. Kolchinsky as the manager of Capital, each beneficially own 6,698,558 shares of Common Stock of the Issuer, representing approximately 8.2% of the class. The percentage of Common Stock beneficially owned by each Reporting Person is based on a total of 81,555,931 shares of Common Stock of the Issuer outstanding as reported on Issuer’s Form 10-Q filed with the SEC on November 07, 2012.

The Fund has the power to vote and dispose of the shares of Common Stock beneficially owned by such entity (as described above). Capital, as the investment adviser and sole general partner of the Fund and as the investment adviser to an account owned by a separate investment vehicle which holds shares of the Issuer’s Common Stock, has the sole authority to vote and dispose of all of the shares of Common Stock reported in this Schedule 13G. The Manager, by virtue of his position as manager of Capital, has the sole authority to vote and dispose of all of the shares of Common Stock reported in this Schedule 13G.

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:

Not applicable.

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

Not applicable.

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

Not applicable.

Item 9.           Notice of Dissolution of Group:

Not applicable.

Item 10.         Certification:

By signing below I hereby certify that, to the best of my knowledge and belief, the securities referred to above 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.

Exhibit 1

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agrees, as of February 14, 2013, that only one statement containing the information required by Schedule 13G, and each amendment thereto, need be filed with respect to the ownership by each of the undersigned of shares of Common Stock of XOMA Corporation, and such statement to which this Joint Filing Agreement is attached as Exhibit 1 is filed on behalf of each of the undersigned.