CHICAGO — Pembrolizumab demonstrated “promising” antitumor activity among patients with advanced small-cell lung cancer, particularly those with a PD-L1 expression of 1% or greater, according to findings from the phase 2 KEYNOTE-158 trial presented at the ASCO Annual Meeting.
The results build on previous findings from the phase 1b KEYNOTE-028 trial, which showed that pembrolizumab (Keytruda, Merck) was effective and well tolerated in patients with PD-L1-positive advanced small cell lung cancer.
Hyun Cheol Chung, MD, PhD, of the Yonsei Cancer Center at Yonsei University College of Medicine in Seoul, South Korea, and colleagues evaluated the safety and efficacy of pembrolizumab in both PD-L1-negative (n = 50; 47%) and PD-L1-positive (n = 42; 39%) patients with small cell lung cancer. Study participants received 200 mg of pembrolizumab every 3 weeks for 2 years or until progression, toxicity or withdrawal. The primary endpoint was objective response rate.
At the time of the analysis cutoff date — Jan. 15, 2018 — 15 patients continued to receive pembrolizumab and 92 patients discontinued treatment, mostly because of cancer progression. Median follow-up was 9.3 months (range, 0.5-22.3 months).
The ORR was 18.7% (95% CI, 11.8%-27.4%) in the overall study population, 35.7% (95% CI, 21.6%-52%) in the PD-L1-positive population and 6% (95% CI, 1.3%-16.5%) in the PD-L1-negative population.
Median PFS was 2 months in the overall study population (95% CI, 1.9-2.1 months), 2.1 months in the PD-L1-positive population (95% CI, 2-8.1 months) and 1.9 months in the PD-L1-negative population (95% CI, 1.6-2 months). OS was 8.7 months in the entire study population, 14.9 months in the PD-L1-positive population (95% CI, 5.6 months-not reached) and 5.9 months in the PD-L1-negative population (95% CI, 3.3-10.1 months).
Treatment-related adverse events occurred in 60% (n = 64) of patients. The most common adverse events were fatigue (14%), pruritus (12%), hypothyroidism (12%), decreased appetite (10%) and nausea (10%). Thirteen patients experienced grade 3 or 4 treatment-related adverse events. Two treatment-related deaths were reported, including one caused by pneumonia and the other by encephalopathy.
The safety outcomes were similar to findings from prior trials examining pembrolizumab monotherapy in other tumor types.
“These findings are consistent with those from the SCLC cohort of the phase 1b KEYNOTE-028 study evaluating pembrolizumab in patients with previously treated extensive-stage tumors expressing PD-L1,” Chung said. “Pembrolizumab plus standard of care chemotherapy, including etoposide plus platinum, is being evaluated in the ongoing phase 3 KEYNOTE-604 study in patients with newly diagnosed extensive stage SCLC.” – by Stephanie Viguers
Chung HC, et al. Abstract 8506. Presented at: ASCO Annual Meeting; June 1-5, 2018; Chicago.
Disclosures: Chung reports receiving consulting or advisory role fees from Bristol-Myers Squibb; Celltrion, Lilly, Merck Serono, MSD, Quintiles and Taiho Pharmaceutical; speakers’ bureau fees from Foundation Medicine, Lilly and Merck Serono; and research funding from Bristol-Myers Squibb, GlaxoSmithKline, Lilly, Merck Serono, MSD and Taiho Pharmaceutical.