SUMMARY:Durable tumor responses have been demonstrated in previous clinical studies using high dose interleukin 2 and anti-CTLA 4 antibody YERVOY® (Ipilimumab), for advanced malignancies such as metastatic melanoma. The programmed death 1 (PD-1) receptor is an inhibitory receptor expressed on activated T-cells in the tumor micro environment. It has two known ligands, PD-L1 and PD-L2 which can turn off the immune system when they combine with the PD-1 receptor. BMS-936558 is an anti-PD-1 targeted, fully human, monoclonal antibody which acts similar to the anti CTLA 4 antibody YERVOY®, thereby unleashing the T cell response against cancer cells. Results from a Phase 1 study in which 296 patients were enrolled demonstrated a durable response rate of 18% among patients with advanced non- small cell lung cancer, 28% among patients with advanced melanoma and 27% among patients with advanced renal cell carcinoma. PD-L1 was identified as a potential biomarker for response, with no responses seen in PD-L1 negative tumors. Topalian SL, Hodi S, Brahmer JR, et al. NEJM June 2, 2012.