Xencor Inc

Recent Partnership Developments

•Amgen: Amgen is advancing two Phase 3 studies of xaluritamig, a STEAP1 x CD3 XmAb 2+1 bispecific T-cell engager, in patients with metastatic castration-resistant prostate cancer (mCRPC). In August 2026, Amgen announced the completion of enrollment in XALute, a Phase 3 study evaluating xaluritamig as a monotherapy in patients with mCRPC previously treated with taxane-based chemotherapy. The Phase 3 XALience study is evaluating xaluritamig in combination with abiraterone versus investigator's choice therapy in patients with chemotherapy-naive mCRPC. Multiple earlier-phase studies are also evaluating xaluritamig as a monotherapy or in combination across additional prostate cancer treatment settings. At the ESMO 2026 Congress, Amgen presented results from a Phase 1 study of xaluritamig monotherapy and xaluritamig in combination with abiraterone in patients with mCRPC who have not yet received taxane-based chemotherapy. Amgen demonstrated that four- to six-hour fully outpatient monitoring after cycle 1 step-up dosing was feasible, supporting the potential for a more convenient administration setting. Xencor is eligible to receive up to $225 million in future milestone payments and tiered royalties on net sales that range from mid- to high-single digit percentages.

•Astellas: In August 2026, Astellas announced that the first patient had been dosed in a Phase 3 clinical trial evaluating ASP2138 in combination with chemotherapy and pembrolizumab as a first-line treatment in adults with locally advanced unresectable or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma, whose tumors are Claudin 18.2 (CLDN18.2)- positive and HER2-negative, which triggered a $25.0 million milestone payment. ASP2138 is an investigational subcutaneously administered bispecific antibody designed to bind to CLDN18.2, a protein expressed on certain tumor cells, and CD3-positive T cells. ASP2138 utilizes Xencor’s XmAb 2+1 multivalent format. Xencor is eligible to receive up to $207.5 million in future milestone payments and tiered royalties on net sales that range from high-single to low-double digit percentages.

•Zenas BioPharma: Zenas submitted a Biologics License Application (BLA) to the FDA for obexelimab for the treatment of IgG4-related disease (IgG4-RD) in May 2026, which was accepted for review in August 2026. In the third quarter of 2026, Zenas’ partner Bristol Myers Squibb submitted a marketing authorization application for obexelimab in IgG4-RD in Japan, which triggered a $2.5 million milestone payment. Obexelimab targets CD19 with its variable domain and uses an XmAb Immune Inhibitor Fc Domain. In November 2021, Xencor licensed obexelimab to Zenas, and under the license agreement, Xencor is eligible to receive up to $447.5 million in future milestone payments and tiered royalties on net sales that range from mid-single-digit to mid-teen percentages, dependent on geography. As of September 30, 2026, Xencor owned 1.0 million shares of common stock in Zenas.

Financial Guidance: Based on current operating plans, Xencor expects to end 2026 with between $480 million and $500 million in cash, cash equivalents and marketable debt securities, and to have sufficient cash resources to fund research and development programs and operations into 2029.