Background: Camrelizumab plus gemcitabine and cisplatin (GP) showed promising preliminary anticancer activity as first line (1L) therapy in patients (pts) with recurrent or metastatic nasopharyngeal carcinoma (R/M NPC) in a phase 1 trial (W Fang et al; Lancet Oncol 2018). Here, we compared the efficacy and safety of camrelizumab with placebo plus GP as 1L therapy for pts with R/M NPC in a phase 3 trial. Methods: Eligible pts with previously untreated R/M NPC were randomized (1:1) to receive either camrelizumab (200 mg on day 1) plus gemcitabine (1000 mg/m² on days 1, 8) and cisplatin (80 mg/m² on day 1) or placebo plus the same chemotherapy regimens intravenously Q3W for a maximum of 6 cycles, followed by maintenance therapy with camrelizumab or placebo. The primary end point was progression-free survival (PFS) per independent review committee (IRC). Secondary end points included investigator-assessed PFS, objective response rate (ORR), disease control rate (DCR), duration of response (DOR), overall survival (OS) and tolerability. This trial is registered with ClinicalTrials.gov, number NCT03707509. Results: From Nov 2018 to Nov 2019, 263 pts from 28 centers were randomized to camrelizumab plus GP (n = 134, camrelizumab arm) or placebo plus GP (n = 129, placebo arm). At data cutoff on Dec 31, 2020 (67.7% maturity), 178 IRC-assessed PFS events occurred, and the median follow-up was 15.6 months (range 1.3-25.5). The median PFS per IRC was 10.8 months (95% CI 8.5-13.6) in the camrelizumab arm and 6.9 (95% CI 5.9-7.9) in the placebo arm (HR 0.51 [95% CI 0.37-0.69]; one-sided P< 0.0001). Investigator-assessed PFS showed similar results. IRC-assessed ORR was 88.1% (95% CI 81.3-93.0) in the camrelizumab arm and 80.6% (95% CI 72.7-87.1) in the placebo arm, with a median DOR of 9.9 (95% CI 7.7-12.5) and 5.7 months (95% CI 5.2-6.9; HR 0.48 [95% CI 0.34-0.68]), respectively. The DCR was 96.3% (95% CI 91.5-98.8) in the camrelizumab arm and 94.6% (95% CI 89.1-97.8) in the placebo arm. 18-month PFS rate was 34.8% (95% CI 25.7-44.1) vs 12.7% (95% CI 6.8-20.5), respectively. OS benefit was observed in the camrelizumab arm vs placebo arm (median not reached vs 22.6 months; HR 0.67 [95% CI 0.41-1.11]). Grade ≥3 treatment-related adverse events (TRAEs) occurred in 93% of pts in the camrelizumab arm and 90% in the placebo arm. The most common grade ≥3 TRAEs were decreased white blood cell count (66% vs 70%), decreased neutrophil count (64% vs 65%), decreased platelet count (40% vs 40%), and anemia (39% vs 43%). None of the differences were statistically significant. The safety profile was as expected, with no new signals observed. Conclusions: Addition of camrelizumab to GP significantly prolonged PFS as 1L therapy for R/M NPC, with a manageable safety profile. These data suggest that first line treatment with camrelizumab plus GP could be a standard of care for R/M NPC. Clinical trial information: NCT03707509