On August 25, 2026 Astellas Pharma Inc. (TSE: 4503, President and CEO: Naoki Okamura, "Astellas") reported that the first patient has been dosed in a Phase 3 study evaluating ASP2138 in combination with chemotherapy and pembrolizumab as 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.1

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This milestone marks an important step in Astellas’ commitment to advancing CLDN18.2 science through a portfolio of approved treatments and investigational assets.

Despite recent advances, many people with advanced gastric and GEJ cancers continue to face poor outcomes, with median progression-free survival of 6 to 7 months with non-CLDN18.2 directed current standard of care.2 Recognizing the importance of continued research into new treatments, Astellas is working to deepen understanding of CLDN18.2 and exploring multiple scientific approaches that may help address different patient needs.

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, a type of white blood cell with the ability to kill cancer cells.1,3 By binding to both targets, ASP2138 is intended to bring these T cells closer to CLDN18.2-expressing tumor cells and activate their anti-tumor response.4

Tadaaki Taniguchi, M.D., Ph.D., Chief Research and Development Officer, Astellas:
"The first patient dosed in this Phase 3 study is an important milestone for ASP2138 and for our broader work in CLDN18.2. By advancing multiple scientific approaches, we are building the evidence needed to better understand how CLDN18.2-targeted innovation may help address patient needs."

As Astellas’ lead program within its Immuno-Oncology Primary Focus, the ASP2138 Phase 3 study supports the Company’s execution of its Corporate Strategic Plan, including its ambition to initiate five or more Phase 3 or pivotal studies by fiscal year 2027. Astellas will share updates as the study progresses, in line with applicable disclosure requirements and company practice.

(Press release, Astellas, AUG 25, 2026, View Source [SID1234670297])