VISTA (V-domain Ig suppressor of T-cell activation)

Class

Anti-VISTA monoclonal antibody, pH-selective (conditionally active in acidic tumor microenvironment)

Pathway

Immune checkpoint blockade restoring T-cell activation and reducing myeloid-derived suppressor cells

VISTA (V-domain immunoglobulin suppressor of T-cell activation, also called VSIR or PD-1H) is an inhibitory checkpoint receptor expressed on T cells and myeloid cells, including myeloid-derived suppressor cells that accumulate in tumors. By dampening T-cell activation and reinforcing suppressive myeloid populations, VISTA helps tumors evade immune attack, often in cancers with dense myeloid infiltration that respond poorly to more established checkpoint blockers such as PD-1 or PD-L1 inhibitors. Antibodies that block VISTA aim to restore T-cell activity and reduce myeloid-mediated suppression, broadening the population of tumors that might respond to checkpoint blockade. A distinguishing feature of some anti-VISTA antibodies is pH-selectivity: they are engineered to bind VISTA preferentially in the acidic conditions characteristic of tumor tissue, rather than at the neutral pH found in normal blood and organs. Because VISTA also contributes to keeping the peripheral immune system in check outside of tumors, this conditional binding is intended to concentrate the drug's activity within the tumor microenvironment while minimizing disruption of normal immune tolerance elsewhere. This mechanism sits within the broader field of immune checkpoint blockade, which spans multiple diseases where cancers or chronic infections exploit inhibitory receptors to escape immune surveillance.