Neurocognitive and hypokinetic movement disorder with features of parkinsonism following BCMA-targeting CAR-T cell therapy

B-cell maturation antigen (BCMA) is a prominent tumor-associated target for chimeric antigen receptor (CAR)-T cell therapy in multiple myeloma (MM). We describe the case of a MM patient, enrolled in the CARTITUDE-1 trial ( NCT03548207 ), who developed a progressive movement disorder with features of parkinsonism approximately three months after BCMA-targeted ciltacabtagene autoleucel CAR-T cell infusion, associated with CAR-T cell persistence in the blood and cerebrospinal fluid, and basal ganglia lymphocytic infiltration. We demonstrate BCMA expression on neurons and astrocytes in the basal ganglia of the patient. Public transcriptomic datasets further confirm BCMA RNA expression in the caudate of normal human brains, suggesting this may be an on-target effect of anti-BCMA therapy. Given reports of three patients with grade ≥3 parkinsonism on the phase 2 cilta-cel trial and of grade 3 parkinsonism in the idecabtagene vicleucel (ide-cel) package insert, our findings support close neurological monitoring of patients on BCMA-targeted T cell therapies.