Recurrent late-onset neutropenia following treatment with different B cell-depleting strategies in multiple sclerosis.

Background: As B cell-depleting therapies in multiple sclerosis (MS) have gained significant importance in the last several years, their long-term safety profile is of considerable clinical interest. Late-onset neutropenia (LON) is a rare, but potentially severe, adverse event that was first described in patients with rheumatic disorders under therapy with rituximab. Ofatumumab was approved in 2021 for the treatment of relapsing-remitting multiple sclerosis (RRMS). Neutropenia occurred in 0.2% of patients in clinical phase 3 trials, and to date, no cases of LON have been reported under ofatumumab treatment.

Methods: Here, we report a case of repetitive symptomatic LON under ocrelizumab as well as ofatumumab treatment. Additionally, we review the literature on rare occurrences of LON in patients with MS, neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) undergoing B cell-depleting therapies, including rituximab, ocrelizumab, ofatumumab, inebilizumab, and ublituximab.

Findings: In our case, the patient presented with repetitive symptomatic LON under ocrelizumab as well as ofatumumab treatment leading to febrile infections, subsequent use of antibiotics, and application of granulocyte-colony-stimulating factor. After repetitive episodes of LON under both B cell-depleting strategies, cladribine was subsequently initiated. A nine-month follow-up showed a normal neutrophil count and no evidence of disease activity.

Conclusions: This case highlights the significance of symptomatic late-onset blood count changes under both ocrelizumab and ofatumumab and emphasizes the importance of continuous monitoring of the differential blood count under B cell-depleting treatment.

Funding: This study was supported by the Deutsche Forschungsgemeinschaft (DFG; SFB CRC-TR-128 to F.Z., V.F., and S.B..; SFB 1080 and SFB CRC-1292 to F.Z..; and SFB/TRR 355 to S.B.) and the Hermann and Lilly Schilling Foundation (to S.B.).