Tremelimumab (T) + durvalumab (D) + chemotherapy (CT) vs pembrolizumab (P) + CT in 1L non-squamous (NSQ) metastatic NSCLC (mNSCLC) with STK11 , KEAP1 , and/or KRAS mutations (mut): Interim analysis (IA) of the phase 2b TRITON study.

8515 Background: Pts with STK11 , KEAP1 and/or KRAS -mutated mNSCLC may benefit from the addition of anti-CTLA-4 to anti-PD-(L)1-based chemo-immunotherapy. In the phase 3 POSEIDON study, 1L T+D+CT significantly improved OS vs CT in pts with mNSCLC. Exploratory analyses showed sustained OS improvement with T+D+CT vs CT in subgroups with STK11 , KEAP1 and/or KRAS mut; in each mut subgroup, magnitude of OS benefit with T+D+CT vs CT was numerically greater than with D+CT vs CT. The phase 2b, open-label, multicenter, US-based TRITON study is comparing 1L T+D+CT vs P+CT in pts with NSQ mNSCLC and STK11, KEAP1 and/or KRAS mut. Here we report results of a planned IA (data cutoff [DCO] 15 mo after 1st pt randomized) of objective response rate (ORR), duration of response (DoR) and safety. Methods: Pts with treatment [tx]-naïve, EGFR / ALK wild-type, NSQ mNSCLC and STK11 , KEAP1 and/or KRAS mut (ECOG PS 0/1) were randomized 1:1 to T+D+CT or P+CT. T+D+CT arm: T 75 mg + D 1500 mg + pemetrexed-platinum Q3W for 4 cycles, then maintenance D + pemetrexed Q4W until disease progression (PD); additional doses of T given at week 16 and, optionally, at mo 24. P+CT arm: P 200 mg + pemetrexed-platinum Q3W for 4 cycles, then maintenance P + pemetrexed Q3W until PD, for up to 24 mo. Randomization was stratified by mut type and tumor PD-L1 expression (≥1% vs