UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 4, 2015

XOMA CORPORATION

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction

of incorporation)

Registrant’s telephone number, including area code (510) 204-7200

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

XOMA Corporation (the “Company”) received a letter from the staff (the “Staff”) of The NASDAQ Stock Market LLC (“NASDAQ”) on September 4, 2015 providing notification that, for the previous 30 consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued listing on The Nasdaq Global Market under NASDAQ’s Listing Rule 5450(a)(1), requiring a minimum bid price of $1.00 per share (the “Minimum Bid Price Requirement”).

The notification of noncompliance has no immediate effect on the listing or trading of the Company’s common stock on the NASDAQ Global Market. In accordance with Nasdaq Listing Rule 5810(c)(3)(A) , if during the 180 calendar days following the date of the notification, or prior to March 2, 2016, the closing bid price of the Company’s common stock is at or above $1.00 for a minimum of 10 consecutive business days, the Staff will provide the Company with written confirmation of compliance.

If the Company does not achieve compliance with the Minimum Bid Price Requirement by March 2, 2016, the Company may be eligible for an additional 180 calendar days compliance period if it elects to transfer to the Nasdaq Capital Market, so as to take advantage of the additional compliance period offered on that market. To qualify, the Company would be required to meet the continued listing requirement for market value of publicly held shares and all other initial listing standards for the Nasdaq Capital Market, with the exception of the bid price requirement, and would need to provide written notice of its intention to cure the deficiency during the second compliance period. However, if it appears to the Staff that the Company will not be able to cure the deficiency, or if the Company is otherwise not eligible, the Staff would notify the Company that its securities would be subject to delisting. In the event of such notification, the Company may appeal the Staff’s determination to delist its securities, but there can be no assurance the Staff would grant the Company’s request for continued listing.

The Company intends to monitor the closing bid price of its common stock and may, if appropriate, consider implementing available options to regain compliance with the Minimum Bid Price Requirement under the NASDAQ Listing Rules.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.