Phase II randomized study of maintenance atezolizumab (A) versus atezolizumab + talazoparib (AT) in patients with SLFN11 positive extensive stage small cell lung cancer. S1929

Abstract

To evaluate whether the addition of a poly (ADP-ribose) polymerase inhibitor (PARPi) talazoparib to maintenance immune checkpoint inhibitor (ICI) atezolizumab following frontline chemoimmunotherapy improved outcomes in patients with Schlafen 11 (SLFN11)-positive extensive stage small cell lung cancer (ES-SCLC). Patients with newly diagnosed SLFN11 expressing (H-score ≥ 1, evaluated centrally) ES-SCLC were randomized to maintenance atezolizumab (A) versus atezolizumab plus talazoparib (AT) following frontline chemotherapy plus atezolizumab. The primary objective was to compare progression-free survival (PFS) using a 1-sided 10% level stratified log-rank test. Secondary endpoints included objective response rate (ORR), overall survival (OS), and toxicity. Target sample size was 84 eligible patients. From June 15, 2020 to December 15, 2022, 106 eligible patients were randomized (54 to AT and 52 to A). PFS was improved with AT versus A (hazard ratio [HR], 0.66; 80% confidence interval [CI]: 0.50-0.86; 1-sided P = 0.019) with a median PFS of 2.9 and 2.4 months; OS was not different between groups (HR, 0.98; 80% CI: 0.71-1.36; 1-sided P = 0.47). Grade ≥ 3 non-hematologic treatment-related adverse events (TRAEs) occurred in 17% of patients with AT and 14% of patients with A. Grade ≥ 3 hematological TRAEs were more common in AT (50%) than in A (4%) (P < 0.001). Maintenance AT improved PFS in patients with SLFN11-positive ES-SCLC that did not progress following initial chemo-immunotherapy. Hematologic toxicity, primarily grade 3 anemia, was increased with AT, as expected. Prospective biomarker-selection was demonstrated, paving the way for future evaluation of novel therapies in molecularly defined SCLC populations.