A phase 1b study evaluating the safety and preliminary efficacy of berzosertib in combination with gemcitabine in patients with advanced non-small cell lung cancer.

Objectives: Berzosertib (formerly M6620, VX-970) is an intravenous, highly potent and selective, first-in-class ataxia telangiectasia and Rad3-related (ATR) protein kinase inhibitor. We assessed the safety, tolerability, preliminary efficacy, and pharmacokinetics (PK) of berzosertib plus gemcitabine in an expansion cohort of patients with advanced non-small cell lung cancer (NSCLC). The association of efficacy with TP53 status and other tumor markers was also explored.

Materials And Methods: Adult patients with advanced histologically confirmed NSCLC received berzosertib 210 mg/m (days 2 and 9) and gemcitabine 1000 mg/m (days 1 and 8) at the recommended phase 2 dose established in the dose escalation part of the study.

Results: Thirty-eight patients received at least one dose of study treatment. The most common treatment-emergent adverse events were fatigue (55.3%), anemia (52.6%), and nausea (39.5%). Gemcitabine had no apparent effect on the PK of berzosertib. The objective response rate (ORR) was 10.5% (4/38, 90% confidence interval [CI]: 3.7-22.5%). In the exploratory analysis, the ORR was 30.0% (3/10, 90% CI: 9.0-61.0%) in patients with high loss of heterozygosity (LOH) and 11.0% (1/9, 90% CI: 1.0-43.0%) in patients with low LOH. The ORR was 33.0% (2/6, 90% CI: 6.0-73.0%) in patients with high tumor mutational burden (TMB), 12.5% (2/16, 90% CI: 2.0-34.0%) in patients with intermediate TMB, and 0% (0/3, 90% CI: 0.0-53.6%) in patients with low TMB.

Conclusions: Berzosertib plus gemcitabine was well tolerated in patients with advanced, pre-treated NSCLC. Based on the observed clinical efficacy, future clinical trials should involve genomically selected patients.