Abstract Background: Patients (pts) with platinum-refractory R/M SCCHN have an extremely poor prognosis and no chemotherapy (CT) options to extend survival. Nivo, a fully human anti-programmed death-1 monoclonal antibody, is FDA-approved and improves survival in other tumor types. Methods: A randomized, open-label, phase 3 trial (NCT02105636) assigned pts (stratified by prior cetuximab) with SCCHN who progressed within 6 mo of platinum-based CT in a 2:1 ratio to nivo 3 mg/kg Q2W or weekly single-agent IC (methotrexate 40-60 mg/m2, docetaxel 30-40 mg/m2, or cetuximab 400-mg/m2 loading dose followed by 250 mg/m2 weekly). Pts must not have received systemic therapy subsequent to biopsy and prior to screening. Pts could receive nivo beyond disease progression if there was evidence of clinical benefit. The primary endpoint was OS. Secondary endpoints were PFS and objective response rate (ORR) by RECIST 1.1. Additional endpoints included safety and outcomes by PD-L1 and HPV (p16 IHC) status. An interim analysis (IA) was planned after at least 195 deaths. Results: Of 361 randomized pts, median age was 60.0 yr, 76.5% were current/former smokers, 54.8% had received ?2 prior lines of CT, 91.4% had prior radiotherapy, and 98.3% had ECOG score ?1. At IA, 133 of 240 pts (55.4%) on nivo and 85 of 121 pts (70.2%) on IC had died. Nivo-treated pts had a 30% reduction in risk of death (HR, 0.70; 97.73% CI, 0.51-0.96; P = 0.010); median OS was 7.5 mo (95% CI, 5.5-9.1) with nivo vs 5.1 mo (95% CI, 4.0-6.0) with IC. Tumor PD-L1 status was evaluable in 260 pts (72.0%). Median OS in pts with PD-L1 ?1% was 8.7 mo with nivo vs 4.6 mo with IC (HR, 0.55; 95% CI, 0.36-0.83) and, in pts with PD-L1 <1%, 5.7 vs 5.8 mo, respectively (HR, 0.89; 95% CI, 0.54-1.45). HPV status by IHC was available in 178 pts (49.3%). Median OS in HPV+ pts was 9.1 mo with nivo vs. 4.4 mo with IC (HR, 0.56; 95% CI, 0.32-0.99) and 7.5 mo vs. 5.8 mo, respectively, in HPV- pts (HR, 0.73; 95% CI, 0.42-1.25). Treatment-related adverse events (TRAEs) of any grade occurred in 58.9% of pts on nivo vs 77.5% of pts on IC; TRAEs Grade 3-4 were reported in 13.1% vs 35.1% of pts, respectively. Two treatment-related deaths on the nivo arm and one on the IC arm occurred. Conclusions: Nivo improved OS in pts with platinum-refractory R/M SCCHN compared to single-agent IC therapy. Pts with PD-L1 ?1% and HPV+ pts had significantly longer median OS with nivo than with IC, but nivo was effective regardless of PD-L1 or HPV status. As the first immunotherapy agent to increase survival in a randomized phase 3 study in R/M SCCHN, nivo is a new standard of care option for these pts. Citation Format: Maura L. Gillison, George Blumenschein, Jérôme Fayette, Joel Guigay, A. Dimitrios Colevas, Lisa Licitra, Kevin Harrington, Stefan Kasper, Everett E. Vokes, Caroline Even, Francis Worden, Nabil F. Saba, Lara Carmen Iglesias Docampo, Robert Haddad, Tamara Rordorf, Naomi Kiyota, Makoto Tahara, Manish Monga, Mark Lynch, William J. Geese, Mark Schactman, Justin Kopit, James W. Shaw, Robert L. Ferris. Nivolumab (nivo) vs investigator's choice (IC) for recurrent or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC): CheckMate-141. abstract. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT099.