Severe Immune Effector Cell-Associated Neurotoxicity Syndrome in a Patient With Multiple Myeloma Treated With Elranatamab

Elranatamab is an effective drug for triple-class-exposed relapsed/refractory multiple myeloma (TCE-RRMM). In the pivotal study, only grade 1 or 2 immune effector cell-associated neurotoxicity syndrome (ICANS) were reported, and the risk factors for immune effector cell-associated neurotoxicity syndrome have not yet been clearly elucidated. This case report documents the first case of grade 4 ICANS in a patient treated with elranatamab, presenting alongside grade 1 cytokine release syndrome (CRS). The patient had a history of cerebral hemorrhage without residual neurological deficits, but its association with ICANS was unclear. High-dose methylprednisolone therapy was required to manage the condition. Magnetic resonance imaging (MRI) findings were negative for new abnormalities, indicating that previous cerebral events could contribute to the risk of ICANS. This case emphasizes the importance of close monitoring of neurological parameters and prompt intervention for patients receiving elranatamab, regardless of a history of neurological conditions or the presence of neurological symptoms at the time of treatment. As more patients are treated with elranatamab, understanding the risk factors for severe immune effector cell-associated neurotoxicity syndrome (ICANS) will be crucial to ensure timely management and improved patient outcomes. Clinicians should be aware of the potential for severe neurotoxicity, even in patients without current neurological deficits, and pay attention to detecting early symptoms and initiate appropriate treatment promptly.