Balstilimab (AGEN2034) is a fully human IgG4 monoclonal antibody that specifically targets Programmed Cell Death Protein 1 (PD-1). As an immune checkpoint inhibitor, Balstilimab effectively blocks the binding of PD-1 to its ligands, PD-L1 and PD-L2. In functional assays using primary human T cells, Balstilimab significantly enhances T cell activation, proliferation, and cytokine production (e.g., IL-2 and IFN-γ) by abrogating PD-1 pathway suppression. Studies demonstrate that when combined with an anti-CTLA-4 antibody (e.g., AGEN1884), Balstilimab exhibits synergistic effects in boosting T cell responsiveness, superior to monotherapy.