Changes in CAR19 copy number and percentage of CAR T cells after pembrolizumab. (A) CAR19 transgene copies/ug DNA for each patient after administration of pembrolizumab (n = 11). Pembrolizumab was started at day 0. Each diamond indicates a subsequent dose of pembrolizumab. Data are classified based on 3-month ORR. One patient with a PR did not have longitudinal data for CAR19 transgene copies available. (B) CAR19 transgene copies per μg DNA for patient 4, who had a complete response to pembrolizumab. (C) Gating strategy for identifying CAR T cells. Live cells were identified as CD45⁺Cisplatin⁻. T cells are gated as CD3⁺ live cells. CAR T cells are identified using a CAR19 antibody and gating the CAR T cells as CAR19⁺CD3⁺ live cells. (D) Percentage of CAR T cells among total T cells as a function of days from pembrolizumab infusion, separated by clinical response (n = 11). Patients with progressive lymphoma after pembrolizumab are indicated in red (“nonresponders,” which includes PD). Patients with clinical benefit after pembrolizumab are indicated in blue (“responders,” which includes SD, PR, and CR). (E) Cumulative dot plot showing the change (difference) in CAR T-cell percentage between the first measurement after pembrolizumab and pre-pembrolizumab baseline in patients with PD, SD, PR, and CR (n = 10).