A fully human monoclonal antibody directed against programmed cell death-1 ligand 1 (PD-L1) with immune checkpoint inhibitory and potential antineoplastic activities. Anti-PD-L1 monoclonal antibody MDX-1105 binds to PD-L1, blocking its binding to and activation of its receptor programmed death 1 (PD-1), which may enhance the T-cell-mediated immune response to neoplasms and reverse T-cell inactivation. PD-L1 is overexpressed by many human cancer cell types. PD-L1 binding to PD-1 on T-cells suppresses the immune system and results in immune evasion. PD-1, a transmembrane protein expressed on activated T-cells, is a negative regulator of the immune system that limits the expansion and survival of CD8+ T cells.