Pembrolizumab With or Without Maintenance Olaparib for Metastatic Squamous Non-Small-Cell Lung Cancer That Responded to First-Line Pembrolizumab Plus Chemotherapy

Background: PARP inhibitors can upregulate PD-L1 expression and promote immune-mediated responses, and may improve efficacy of first-line anti‒PD-1‒based therapies in patients with metastatic squamous NSCLC.

Methods: In this randomized, double-blind, phase 3 trial (NCT03976362), adults with previously untreated stage IV squamous NSCLC received 4 cycles of induction therapy (pembrolizumab 200 mg Q3W plus carboplatin and paclitaxel or nab-paclitaxel). Patients with disease control were randomized to 31 cycles of pembrolizumab 200 mg Q3W plus olaparib 300 mg orally twice-daily or placebo. Dual primary endpoints were progression-free survival (PFS) and overall survival (OS). PFS was tested at interim analysis 2 (IA2; the final PFS analysis); OS was tested at final analysis.

Results: 851 patients received induction treatment; 296 were randomized to pembrolizumab plus olaparib and 295 to pembrolizumab plus placebo. At IA2, with median follow-up of 27.1 months, median (95% CI) PFS was 8.3 (6.7‒9.7) in the pembrolizumab plus olaparib group and 5.4 (4.1‒5.6) months in the pembrolizumab plus placebo group (HR, 0.77 [95% CI, 0.63‒0.93]; P=0.0040 [not significant at a 1-sided at superiority boundary of P=0.003). At final analysis, with median follow-up of 33.4 months, median (95% CI) OS was 19.1 (15.9‒22.2) and 18.6 (16.0‒21.6) months, respectively (HR, 1.01 [95% CI, 0.83‒1.24]; P=0.5481). Treatment-related adverse events occurred in 76.5% and 65.1% of patients, respectively.

Conclusion: Adding olaparib to pembrolizumab as maintenance therapy for metastatic squamous NSCLC did not significantly improve PFS versus pembrolizumab plus placebo, neither PFS nor OS met the prespecified statistical significance boundary. No new safety signals were identified.