Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2,F5,F6	Jul 22, 2015	S	1,359,253	$1.0925	D	467,436	I	See footnote
Common Stock^F1,F3,F5,F6	Jul 22, 2015	S	9,411,311	$1.0925	D	3,153,539	I	See footnote
Common Stock^F1,F4,F5,F6	Jul 22, 2015	S	229,436	$1.0925	D	90,538	I	See footnote

Table II — derivative securities

No Table II lines on this filing.

Explanation of responses

F1The price reported in Column 4 is a weighted average price. These shares were sold by each of Baker Brothers Life Sciences, L.P. ("Life Sciences"), 14159, L.P. ("14159"), and 667, L.P. ("667", and together with Life Sciences and 14159, the "Funds") in multiple transactions at prices ranging from $0.83 to $1.41, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.
F2After giving effect to the transactions reported herein and as a result of their ownership interest in Baker Biotech Capital (GP), LLC, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.
F3After giving effect to the transactions reported herein and as a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.
F4After giving effect to the transactions reported herein and as a result of their ownership interest in 14159 Capital (GP), LLC, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by 14159, a limited partnership of which the sole general partner is 14159 Capital, L.P., a limited partnership of which the sole general partner is 14159 Capital (GP), LLC, due to 14159 Capital, L.P.'s right to receive an allocation of a portion of the profits from 14159.
F5Includes beneficial ownership of 14,000 total shares of common stock received upon vesting of restricted stock units issued to Dr. Kelvin M. Neu in his capacity as a previous director of the Issuer. Dr. Neu, pursuant to the policies of the Adviser, does not have any right to the pecuniary interest in the restricted stock units issued for his previous service on the Board of Directors of the Issuer (the "Board"). These shares are reported for each of the Funds as each has an indirect proportionate pecuniary interest in the shares of common stock received upon vesting of the restricted stock units issued in connection with Dr. Neu's service on the Board. Solely as a result of their ownership interest in the general partners of the general partners of the Funds, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the shares issued upon vesting of the restricted stock units (i.e. no direct pecuniary interest). The previous Form 4 filed on January 6, 2015 included 39,100 shares shares of common stock underlying restricted stock units, 25,100 of which were cancelled upon Dr. Neu's termination of service from the Board on May 20, 2015.
F6Baker Bros. Advisors LP ("the Adviser") serves as the Investment Adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are principals of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds have relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds. Pursuant to agreements between Dr. Neu and the Adviser, the Adviser has investment and dispositive power over the stock options and restricted stock units received by Dr. Neu related to his service on the Board and any shares received as a result of the exercise of stock options or the vesting of restricted stock units that were received related to such service. Pursuant to the policies of the Adviser, Dr. Neu does not have any right to any of the Issuer's securities issued as part of his service on the Board, and the Funds are entitled to receive all the pecuniary interest in the securities issued. Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

Remarks

Dr. Kelvin M. Neu, an employee of Baker Bros. Advisors LP, ceased to be a director of Xoma Corporation (the "Issuer") on May 20, 2015 by not standing for re-election to the Issuer's Board.