PTT-4256

PTT-4256 is an orally administered, highly potent, and selective small molecule inhibitor of the pH-sensing G protein-coupled receptor 65 (GPR65). Developed by Pathios Therapeutics, it represents a first-in-class approach targeting GPR65 to counteract immunosuppressive polarization of immune cells within the tumor microenvironment. By inhibiting GPR65—which is exclusively expressed on immune cells and associated with driving an immunosuppressive phenotype—PTT-4256 aims to relieve acidic immune suppression in cancer. Preclinical studies have shown that PTT-4256 can reverse macrophage polarization induced by low pH, promote pro-inflammatory cytokine secretion (such as TNF-alpha and CXCL10), increase infiltration of T cells and NK cells into tumors, and demonstrate significant anti-tumor activity as monotherapy. The drug is currently being evaluated in a Phase 1/2 clinical trial (RAISIC-1) for patients with advanced solid tumors.