X0306 4/A 2013-10-18 2013-10-21 0 0000791908 XOMA Corp XOMA 0001210905 RUBIN PAUL D C/O XOMA CORPORATION 2910 SEVENTH STREET BERKELEY CA 94710 0 1 0 0 Sr. VP Clinical Dev. & CMO Common Shares 2013-10-18 4 S 0 5254 4.706 D 3534 D This transaction was made pursuant to Rule 10b5-1 trading plan adopted by the reporting person on 3/20/2013. Due to an error in the information that was provided to the reporting person by the issuer, the original Form 4 that was filed on October 21, 2013 neglected to report a sale of 5,254 shares of Common Stock on October 18, 2013. This Form 4 amends the original Form 4 by reporting that sale and by adjusting accordingly the shares reported as beneficially owned in Table I, Column 5. This transaction was executed in multiple trades ranging at prices from $4.65 to $4.81.The price reported reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transactions were effected. By: Russell Wood For: Paul D. Rubin 2013-11-01