<qa>  What is the primary endpoint of pembrolizumab?Single center, phase III trial of pembrolizumab after CTL019 for CD19 lymphomas. Patients will have CD19 diffuse large B-cell, follicular, or mantle cell lymphomas relapsedrefractory after CTL019. 12 total patients will be enrolled. Safety of pembrolizumab primary endpoint will be determined using a Bayesian monitoring rule for treatment-related adverse events causing drug discontinuation. Secondary efficacy endpoints include overall response rate and progression-free survival. 