Background: NIVO demonstrated superior overall survival (OS) vs chemo in previously treated patients (pts) with ESCC (ATTRACTION-3). We report OS and progression-free survival (PFS) from CheckMate 648, the first global phase III study to evaluate both an immuno-oncology (I-O)/chemo combination and an I-O/I-O combination in advanced ESCC. Methods: Adults with previously untreated, unresectable advanced, recurrent or metastatic ESCC were enrolled regardless of tumor cell PD-L1 expression. Pts were randomized to NIVO (240 mg Q2W) + chemo (fluorouracil + cisplatin Q4W), NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W), or chemo alone. Primary endpoints for both comparisons were OS and PFS per blinded independent central review (BICR) in pts with tumor cell PD-L1 ≥ 1%. Hierarchically tested secondary endpoints included OS and PFS in all randomized pts. Results: 970 pts were randomized to NIVO + chemo, NIVO + IPI, and chemo arms (49% with tumor cell PD-L1 ≥ 1%). With 13 months (mo) minimum follow-up, NIVO + chemo and NIVO + IPI led to statistically significant improvement in OS vs chemo in pts with tumor cell PD-L1 ≥ 1% and all randomized pts (Table). Statistically significant PFS benefit was also observed for NIVO + chemo vs chemo (HR 0.65 [98.5% CI 0.46–0.92]; P = 0.0023) in pts with tumor cell PD-L1 ≥ 1%. PFS in NIVO + IPI vs chemo in pts with tumor cell PD-L1 ≥ 1% did not meet the prespecified boundary for significance. The objective response rate (per BICR) was 53% (NIVO + chemo), 35% (NIVO + IPI), and 20% (chemo) in pts with tumor cell PD-L1 ≥ 1% and in all randomized pts was 47%, 28%, and 27%, respectively; longer median (95% CI) duration of response was observed vs chemo for pts with tumor cell PD-L1 ≥ 1%: 8.4 (6.9–12.4), 11.8 (7.1–27.4), and 5.7 (4.4–8.7) mo and for all randomized pts: 8.2 (6.9–9.7), 11.1 (8.3–14.0), and 7.1 (5.7–8.2) mo, respectively. No new safety signals were identified (Table). Conclusions: NIVO plus chemo and NIVO plus IPI both demonstrated superior OS vs chemo, along with durable objective responses and acceptable safety, in pts with advanced ESCC, and each represents a potential new 1L treatment option. Clinical trial information: NCT03143153

^aDue to any component of the regimen.