APN421

APN421 is a preclinical-stage small molecule inhibitor developed by Apeiron Biologics (now invIOs) for the treatment of various solid tumors. The drug targets the E3 ubiquitin-protein ligase CBL-B (Cbl-b), which serves as a critical negative regulator of T-cell and NK-cell activation. By inhibiting Cbl-b, APN421 aims to lower the threshold for immune cell activation and prevent the degradation of key signaling molecules, thereby enhancing the body's natural anti-tumor immune response. This approach positions APN421 as an intracellular checkpoint inhibitor, potentially offering a novel mechanism to overcome immunosuppression in the tumor microenvironment. The program was part of Apeiron's broader focus on Cbl-b modulation, which includes both cellular therapies and small molecule inhibitors.