Progressive multifocal leukoencephalopathy in patients treated with chimeric antigen receptor T cells.

Using 2 global postmarketing surveillance databases, Goldman and colleagues report that progressive multifocal leukoencephalopathy (PML), a viral disease associated with profound immunosuppression, occurs in approximately 0.9 cases per 1000 recipients of CD19-directed CAR T-cell therapy. The risk of PML appears higher with CAR T-cell therapy than other cancer therapies, but its precise role cannot be distinguished from antecedent therapies that these patients receive.