CAR T-Cell Expansion and Persistence
CRS
MYELOMA, AMPLIFICATION
The presence of anti-GPRC5D CAR T cells in patients' peripheral blood was evaluated by quantitative polymerase chain reaction (Data Supplement). Amplification of GPRC5D-CARs peaked between days 14 and 28 postinfusion followed by a gradual decrease. The expansion was durable, with 89% and 48% of 33 patients having detectable CAR T cells at 1 and 3 months, respectively (Data Supplement). The patients with clinical responses showed a tendency to higher peak levels than those without responses (Data Supplement), including two patients having detectable CAR T cells for more than 7 months. Peak levels of GPRC5D-CARs in patients with CRS were significantly higher than those without CRS (Data Supplement). No association of initial GPRC5D expression on myeloma cells with GPRC5D-CARs expansion was observed; also, there was no significant difference in CARs expansion between patients treated with ATRA and those without exposure to ATRA.