Response details
There were 61 subjects evaluable for response, but all 70 patients were considered in the response rate. There were 5 complete responses and 14 partial responses, for a response rate of 27% (19/70). The median duration of response was 18.5 months.
“We did observe a substantially higher response rate among the PD-L1 negative subgroup, as compared to PD-L1-positive,” Dr. Olson said. “The responses observed in some of these higher-risk patients, and especially the responses we saw among many PD-L1-negative tumors, suggested that we might be capturing atypical responders with [pembrolizumab plus ipilimumab].”
“Most responses occurred in non-T-cell-inflamed or intermediate tumors,” Dr. Olson added. “Our trial enriched for non-T-cell inflamed tumor phenotypes, where we then observe[d] responses.”
“These patients responded across BRAF mutation status,” Dr. Johnson noted. “Patients who had elevated LDH, those who had liver metastases, brain metastases, also had comparable response rates to those lacking those more adverse prognostic features.”
Survival and safety
The median progression-free survival was 5 months, and the median overall survival was 24.7 months.
“The multiple durable responses we observed did translate into long-term survival for some patients,” Dr. Olson said.
Eighteen subjects (26%) had grade 3 adverse events at least possibly related to treatment. The most common were colitis/diarrhea in 9%, rash in 6%, and ALT/AST elevations in 6%. There was one grade 4 adverse event, a lipase elevation.
The median time to onset of high-grade adverse events was 55 days, which would fall between cycles 2 and 3 of ipilimumab “and is similar to the experience with [ipilimumab] in the front-line setting,” Dr. Olson said.
This study was funded by an investigator-initiated grant from Merck. Dr. Olson had no disclosures. Some of his coinvestigators reported ties to the company. Dr. Johnson is an advisor for Merck.
SOURCE: Olson D et al. ASCO 2020, Abstract 10004.