A Single-Arm Phase 2 Study of Sotorasib Plus Carboplatin and Pemetrexed in Patients With Advanced Nonsquamous NSCLC With KRAS G12C Mutation (WJOG14821L, SCARLET).

Introduction: The efficacy and safety of sotorasib plus platinum doublet chemotherapy in KRAS G12C-mutated nonsquamous NSCLC (nonsq NSCLC) have been previously reported with a limited follow-up period.

Methods: SCARLET is a single-arm phase 2 study involving chemotherapy-naive patients with KRAS G12C-mutated nonsq NSCLC. The participants received 960 mg daily plus four cycles of carboplatin (area under the curve = 5)/pemetrexed 500 mg/m, followed by sotorasib/pemetrexed until disease progression. The primary end point was the overall response rate (ORR) and the secondary end points were progression-free survival (PFS), overall survival, and safety. Using plasma samples, next-generation sequencing was performed at baseline, 3 weeks, and during disease progression (the Japan Registry of Clinical Trials number 2051210086).

Results: Thirty patients were enrolled between October 2021 and July 2022 with a median follow-up of 14.8 months. ORR was 88.9% (80% confidence interval [CI]: 78.5%-94.8%, 95% CI: 70.8%-97.6%), median PFS was 6.6 months (95% CI: 5.3-16.7 mo), and median overall survival was 20.6 months (95% CI: 8.1 mo-not estimated). Among patients with programmed death-ligand 1 expression levels of 1% or higher and less than 1%, the ORRs were 82.3 and 100%, respectively, and the median PFS was 7.6 and 9.7 months, respectively. Using plasma samples, patients without KRAS G12C at baseline, without KRAS-related pathway co-alterations, or who cleared KRAS G12C at 3 weeks had better median PFS (16.7, 13.9, 8.7 mo, respectively). Tumor protein 53 mutations and EGFR and MET amplification were detected as acquired resistance.

Conclusions: In patients with KRAS G12C-mutated nonsq NSCLC, sotorasib plus carboplatin/pemetrexed reported favorable efficacy, particularly for patients with less than 1% programmed death-ligand 1, with manageable toxicity.