Clinical Features of Hemophagocytic Syndrome Following BCMA CAR-T Cell Therapy in Patients with Relapsed/refractory Multiple Myeloma

Objective: To analyze the clinical features of hemophagocytic syndrome (HLH) following B cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T cell therapy in patients with relapsed/refractory multiple myeloma.

Methods: Ninety-nine patients with relapsed/refractory multiple myeloma (including 3 cases of plasma cell leukemia) undergoing BCMA CAR-T cell therapy (monocentric phaseⅠclinical trial, ChiCTR1800017404) in the First Affiliated Hospital, Zhejiang University School of Medicine from July 2018 to December 2021 were enrolled in the study. The baseline features, laboratory findings, treatment, and clinical response of these patients were analyzed.

Results: CAR-T cell associated HLH (carHLH) occurred in 20 patients (20.20%), and the median onset time was 7(0-19) d after cytokine release syndrome (CRS). Patients with carHLH were maily male patients, and manifested as high percentage of abnormal plasma cells, higher incidence of severe CRS (grade 3-4), and robust expansion of CAR-T cells in the peripheral blood (all <0.05). The levels of interleukin (IL)-6, IL-10 and interferon (IFN)-γ, the peak value of international normalized ratio and D-dimer were elevated, and the valley value of fibrinogen was decreased in patients with carHLH (all <0.01). All carHLH patients resolved with proper intervention (including 7 cases with tocilizumab, 5 with steroids, 6 with both). The objective response rate in carHLH patients was slightly higher than that in non-carHLH patients [100.0% (17/17) vs. 94.87% (74/78), >0.05].

Conclusions: The incidence of carHLH is relatively high in BCMA CAR-T cell treated patients, which is closely related to pretreatment tumor cell percentage in bone marrow, expansion of CAR-T cells and the secretion of cytokines. Medication based on tocilizumab and steroids can achieve considerable therapeutic effects in patient with carHLH.