Road trip to remission with CARs

What happens when a novel drug isn't a drug, but a replicating, cell-based product? In this issue of Blood, Mueller et al performed the first formal cellular kinetic analyses of tisagenlecleucel (CTL019) in patients with acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL) using pharmacokinetic principles to characterize the movement and persistence of cell-based therapies and examine its relationship to efficacy and safety. 1 Pharmacokinetics, the movement of a drug into, through, and out of a body, are vital to understanding the appropriate use of a novel drug, but the movement and persistence of living cellular therapy products cannot be expected to follow conventional rules. The recent US Food and Drug Administration approval of CTL019 for pediatric ALL is changing the landscape of treatment of hematologic malignancies, down to how we define a drug.