Definition

A human immunoglobulin G1 (IgG1) monoclonal antibody directed against HERV-H LTR-associating protein 2 (HHLA2; HHLA-2; B7 homolog 7; B7-H7), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-HHLA2 monoclonal antibody NPX887 targets and binds to HHLA2, and blocks the interaction between HHLA2 and its receptors. This abrogates the HHLA2-mediated inhibition of T-cell and nature killer (NK) cell activation, which may lead to enhanced cytotoxic T-lymphocyte (CTL)-mediated immune response and NK cell cytotoxicity against cancer cells. HHLA2, a member of the B7 family of immune modulators, is upregulated in a variety of tumor cell types and a negative regulator of T-cell and NK cell activation.