YBL-003

YBL-003 is a preclinical IgG-based monoclonal antibody immune checkpoint inhibitor being developed for the treatment of solid tumors. It was originally discovered by Y-Biologics using its antibody discovery platforms and subsequently licensed to Pierre Fabre for global development.[6][13] Public disclosures from Y-Biologics describe YBL-003 as a macrophage‑modulating checkpoint inhibitor, and external analyses classify it as a VSIG4‑modulating antibody, targeting the V-set and immunoglobulin domain-containing 4 protein expressed on macrophages and other myeloid cells.[5][3] By blocking VSIG4‑mediated inhibitory signaling, the antibody is intended to reprogram tumor‑associated macrophages and enhance antitumor immune responses in solid cancers. As of the latest reports, the program remains in preclinical development.[3]