245 Background: Inhibition of TIGIT, a novel checkpoint inhibitor, may further amplify immune responses by complementing the PD-L1/PD-1 pathway. Anti-tumor activity has been demonstrated with cancer immunotherapy in ESCC. SKYSCRAPER-08 (NCT04540211) is evaluating the efficacy and safety of tira (anti-TIGIT) + atezo (anti-PD-L1) in combination with CT compared with placebo + CT as 1L treatment (tx) in an Asian population with unresectable locally advanced (LA), unresectable recurrent, or metastatic (R/M) ESCC. Methods: Eligible pts (confirmed LA or R/M ESCC; ECOG PS 0–1; no prior systemic tx) were randomized 1:1 to receive tira 600mg + atezo 1200mg + CT (paclitaxel 175mg/m2 + cisplatin 60–80mg/m2, local standard of care) or placebo + CT on Day 1 of each 21-day cycle (cycles 1–6); followed by tira + atezo or placebo maintenance until loss of clinical benefit/unacceptable toxicity. Primary endpoints: independent review facility (IRF)-assessed progression-free survival (PFS) and overall survival (OS). Secondary endpoints: investigator (INV)-assessed PFS, objective response rate (ORR), duration of response (DoR), and safety. Results: Overall, 461 pts were randomized (tira + atezo + CT, n= 229; placebo + CT, n=232). Pt characteristics were generally balanced between arms. As of 15 June 2022 (minimum survival follow-up 6.5 months [mo]; PFS primary analysis), median IRF-assessed PFS was 6.2 mo for tira + atezo + CT vs 5.4 mo for placebo + CT (HR 0.56; 95% CI: 0.45, 0.70; P<0.0001). As of 13 Feb 2023 (minimum survival follow-up 14.5 mo; OS final analysis), median OS was 15.7 mo for tira + atezo + CT vs 11.1 mo for placebo + CT (HR: 0.70; 95% CI: 0.55, 0.88; P= 0.0024). INV-assessed PFS, IRF-assessed ORR and DoR are presented in Table. Treatment-related adverse events (TRAEs) occurred in 98.2% of pts (both arms); Grade 3/4 TRAEs in 59.6% (tira + atezo + CT) and 56.4% (placebo + CT) of pts; Grade 5 TRAEs in 2.6% (tira + atezo + CT) and 0.9% (placebo + CT) of pts. Conclusions: The study met both primary endpoints of IRF-assessed PFS and OS, demonstrating statistically significant and clinically meaningful improvements in PFS and OS for tira + atezo + CT over placebo + CT. Generally consistent benefit was observed across subgroups, including PD-L1 status. The safety profile was consistent with the known risks of the individual tx. Clinical trial information: NCT04540211 . [Table: see text]
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