The ongoing study, with planned enrollment of 37 patients, includes patients aged 18-70 years with relapsed/refractory AML (median age of first 20 enrolled is 54 years). Those under age 60 years receive 2 g/m2 of intravenous HiDAC every 12 hours on days 1-5, and those over age 60 years receive 1.5 g/m2 every 12 hours on days 1-5. In both age groups, this is followed by intravenous pembrolizumab given at 200 mg on day 14.
Overall responders receive maintenance phase intravenous pembrolizumab at 200 mg every 3 weeks for up to 2 years until relapse or progression. Patients are allowed to proceed to stem cell transplant before or after the maintenance phase.
A number of correlative studies, including serial peripheral blood and bone marrow flow cytometry and T-cell receptor clonality studies, also are being conducted to look for predictive biomarkers of response, Dr. Zeidner said.
The study population to date is a relatively young, very-high-risk subgroup of AML patients; European LeukemiaNet-2017 genetic risk status was favorable in only 3 of the first 20 patients (15%), intermediate in 7 (35%), and adverse in 10 (50%). Treatment has been well tolerated; toxicities have been rare and manageable. “Overall, there have been no unexpected toxicities,” he said.