A human monoclonal antibody against the protein V-domain immunoglobulin (Ig) suppressor of T-cell activation (VISTA; programmed death 1 homolog; PD1H; PD-1H), with potential negative checkpoint regulatory and antineoplastic activities. Upon administration, onvatilimab targets and binds to VISTA. This inhibits VISTA signaling, abrogates the VISTA-induced suppression of T-lymphocyte-mediated immune responses, enhances cytotoxic T-cell responses against tumor cells and inhibits tumor cell growth. VISTA, mainly expressed on hematopoietic cells, plays a key role in immunosuppression.