Japanese pharmaceutical company Astellas Pharma Inc (TSE:4503) announced on Monday 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.

The company says that 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. Recognising the importance of continued research into new treatments, Astellas says that it 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 tumour cells, and CD3-positive T cells, a type of white blood cell with the ability to kill cancer cells. By binding to both targets, ASP2138 is intended to bring these T cells closer to CLDN18.2-expressing tumour cells and activate their anti-tumour response.