Real-world data on siponimod-related lymphopenia among people with secondary progressive multiple sclerosis

Background: Siponimod-related lymphopenia in real-world clinical practice has implications for dose adjustment and infection risk.Objective: To characterise siponimod-related lymphopenia in people with secondary progressive multiple sclerosis (pwSPMS).Methods: This is a retrospective cohort of 188 pwSPMS. The development of grade 4 lymphopenia was interrogated with Kaplan-Meier survival analysis and binary logistic regression.Results: Lymphopenia develops soon after commencing siponimod. In total, 15 (8.5%) of 176 experienced grade 4 lymphopenia at 1 month after initiation. There were no clinically significant associations between patient characteristics and development of grade 4 lymphopenia.Conclusion: Grade 4 lymphopenia can occur soon after siponimod initiation and cannot be predicted.