Temporal profile of lymphocyte counts and relationship with infections with fingolimod therapy in paediatric patients with multiple sclerosis: Results from the PARADIGMS study

Background: Reduction in absolute lymphocyte count (ALC) is expected with fingolimod treatment. Objective: To evaluate the effect of fingolimod 0.5 mg versus intramuscular interferon β-1a (30 μg) on ALC and its relationship with infections in paediatric-onset multiple sclerosis (POMS) up to 4 years. Methods: We assessed ALC at baseline, monthly till 3 months, and every 3 months (core phase) and with variable periodicity (extension phase) of Phase 3 PARADIGMS study (N = 215). Incidence rates (IRs) of infection-related adverse events (infAEs)/100 patient-years were analysed by on-study nadir ALC. Results: With fingolimod, ALC rapidly reduced to 29.9%–34.4% of baseline values within 2 weeks and remained stable thereafter; no relevant changes observed with interferon. IRs of infAEs were 67.6 with fingolimod and 61.8 with interferon; IR ratios with respect to interferon, overall: 1.09, by nadir ALC 0.2–0.4 × 109/L: 1.13 and >0.4 × 109/L: 0.91. Three patients had a single episode of ALC