Kinetics of CAR T cells after CT103A infusion. (A) Kinetics of the CAR T cells in the patients are shown by the CAR copies per microgram of genomic DNA (copies/μg gDNA) at serial time points post-infusion using digital droplet polymerase chain reaction. The data were obtained until the latest follow-up of each patient. The horizontal line denotes the lower limit of quantitation (LLQ: 20 CAR copies/μg gDNA). Red, light green, and blue lines represent patients receiving infusion doses of 1, 3, and 6 × 10⁶ cells/kg, respectively. By the end of the last follow-up, expansion of CT103A was not detected in 4 patients only. (B) Four patients had relapsed from a prior murine BCMA CAR T-cell therapy. Copy numbers of CT103A and previous murine BCMA CARs were simultaneously monitored by digital droplet polymerase chain reaction in these patients. In each panel, the upper red curve is CT103A, and the lower light green curve is the murine BCMA CAR.