Further development of abemaciclib, pembrolizumab combo not supported
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Data showed manageable and consistent side effects with combination abemaciclib and pembrolizumab, but produced a higher rate of transaminase elevations than individual treatments, according to a presentation at the virtual ASCO20 Annual Meeting.
“The combination of abemaciclib and pembrolizumab appeared to be relatively well tolerated, but a higher rate of transaminase elevation was reported than has been seen with each individual agent alone,” Hope Rugo, MD, professor of medicine and director of Breast Oncology and Clinical Trials Education at University of California, San Francisco Comprehensive Cancer Center, said.
This multicenter, multicohort phase 1b study of abemaciclib plus pembrolizumab enrolled patients with endocrine resistant HR positive, HER2 negative metastatic breast cancer and had received 1 to 2 previous chemotherapy regimens for metastatic breast cancer. No prior CDK4/6 inhibitor was allowed. Patients received 150 mg abemaciclib orally every 12 hours plus pembrolizumab 200 mg IV for 21 days.
The primary objective was to characterize the safety of combination abemaciclib plus pembrolizumab while secondary objectives involved objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) in patients.
Of the 28 enrolled patients, 15 (54%) received one line and 10 (36%) patients received two lines of prior systemic chemotherapy in the locally advanced or metastatic setting. Safety of combination abemaciclib and pembrolizumab was generally consistent with known side effects and found to be manageable.
Notable adverse events included neutropenia, aspartate aminotransferase increase, diarrhea and alanine aminotransferase increase. Eight patients had confirmed partial response (29% ORR), and disease control rate was 82%.
Clinical benefit rate (CR+PR+SD persisting for ≥6 months) was 46%. Median progression-free survival and overall survival was about 8.9 months.
Abemaciclib plus pembrolizumab as a combination showed a generally tolerable safety profile with a numerically higher rate of transaminase elevations than reported for the treatments separately. Results in ORR, PFS and OS were numerically higher but not significantly different compared with historical data for abemaciclib monotherapy in a similar patient population.“
The benefit/risk assessment of this cohort…do not support further development of abemaciclib plus pembrolizumab,” Rugo said.
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