• Royalty term on Ultomiris® sales in the United States anticipated to continue into year-end 2028, extending term by three years 
• Additional $100 million to $120 million in potential royalty revenue estimated to be received by Xencor, based on consensus sales forecasts 

PASADENA, Calif. / Dec 09, 2025 / Business Wire / Xencor, Inc. (NASDAQ:XNCR), a clinical-stage biopharmaceutical company developing engineered antibodies for the treatment of cancer and autoimmune diseases, today announced the issuance of U.S. Patent 12,492,253, which covers Xencor’s Xtend™ Fc domain for extending the half-life of antibodies targeting C5, with a term that extends into December 2028. The new patent term is approximately three years longer than the previous latest-to-expire U.S. patent covering the Xtend Fc domain.

Xencor now anticipates receiving low-single digit royalties on net sales of Ultomiris® (ravulizumab-cwvz), an anti-C5 antibody engineered with a licensed Xtend Fc domain, into December 2028 in the United States. Ultomiris is a drug being developed and commercialized by Alexion Pharmaceuticals, Inc., and is a registered trademark of Alexion. Xencor has also previously secured regulatory extensions of exclusivity in several EU countries, Japan and Australia.

“Xencor’s Xtend antibody half-life extension technology is one of several modular XmAb Fc domains that power Xencor’s XmAb medicines and drug candidates across internal and partner portfolios,” said Bassil Dahiyat, Ph.D., president and chief executive officer at Xencor. “Importantly, this patent term extension also extends the U.S. royalty term for Ultomiris by approximately three years. We anticipate the resulting additional revenue will support our internal pipeline as it advances into later stages of clinical development and will drive further innovation across our portfolio, continuing to fuel the cycle of value creation that has been central to our strategy.”

In 2023, OMERS, one of Canada’s largest defined benefit pension plans, acquired royalties due to Xencor on global Ultomiris sales subject to annual caps beginning in 2026. For potential sales related to Ultomiris occurring between 2026 and 2028, OMERS is entitled to receive up to $35 million annually with excess reverting to Xencor. For the nine-month period ending September 30, 2025, Xencor recognized non-cash royalty revenue of $51.0 million. Based upon consensus sales forecasts of Ultomiris, Xencor estimates recognizing potential royalty revenue in excess of the caps in the range of $100 million to $120 million in aggregate for the extended patent term through 2028.

About Xencor

Xencor is a clinical-stage biopharmaceutical company developing engineered antibodies for the treatment of patients with cancer and autoimmune diseases. More than 20 candidates engineered with Xencor's XmAb® technology are in clinical development, and multiple XmAb medicines are marketed by partners. Xencor's XmAb engineering technology enables small changes to a protein’s structure that result in new mechanisms of therapeutic action. For more information, please visit www.xencor.com.

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