Steven B. Engle has been named president, chief executive officer and a member of the board of directors of Xoma Ltd. Mr. Engle succeeds Jack Castello, the company's former president and chief executive officer, who announced his retirement plans earlier this year. Mr. Castello will remain with the company as non-executive chairman of the board during a transition period, expected to run through October of 2007.

"On behalf of the Xoma Board, I couldn't be more pleased that Steve has joined Xoma to serve as the company's next president and chief executive officer," said Denny Van Ness, a member of Xoma's board of directors who led the succession search. "His leadership experience in our industry, together with his expertise in therapeutic products, operations and corporate development, make him the right person to lead Xoma forward. I am confident in Steve's ability to enhance and execute the company's strategic plan to create value for Xoma shareholders."

Mr. Van Ness added, "I also want to thank Jack Castello for his strong leadership and years of service at Xoma. It is due to his efforts that Xoma is so well-positioned today. We appreciate his many contributions to the company and wish him all the best in retirement."

Mr. Engle has more than 25 years of executive leadership and biotechnology and pharmaceutical industry experience. He previously served as chairman of the board and chief executive officer of La Jolla Pharmaceutical Co. Prior to joining La Jolla, he held executive-level positions at Cygnus Therapeutic Systems and Micro Power Systems, Inc. He began his professional career with the Strategic Decisions Group and the Stanford Research Institute.