The binding of Programmed Cell Death Protein 1 (PD-1), a receptor expressed on activated T-cells, to its ligands, PD-L1 and PD-L2, negatively regulates immune responses. The PD-1 ligands are found on most cancers, and PD-1:PD-L1/2 interaction inhibits T cell activity and allows cancer cells to escape immune surveillance. diabetes.

Human CD137 (4-1BB; TNFRS9) is an inducible costimulatory molecule that activates T cells. CD137-CD137L mediated signaling has been shown to be important for proliferation, effector functions and survival of T cells. CD137 is also expressed in NK and NKT cells. Antibodies targeting CD137 activation in immune cells have demonstrated potent anti-tumor effects in cancer patients.

Figure 1. Dose Response of Blocking Antibodies in PD-1/41BB Dual Effector Reporter Cells (C64) With PD-L1 aAPC Cells.