Treatment-emergent adverse events occurring early in the treatment course of cladribine tablets in two phase 3 trials in multiple sclerosis

Background Treatment-emergent adverse events (TEAEs) that occur close to treatment initiation may negatively affect overall tolerability and adherence. It is important to develop a clear understanding of potential early TEAEs after initiating treatment with cladribine tablets. Objective To identify TEAEs that begin early in the course of treatment in patients enrolled in CLARITY and ORACLE-MS studies. Methods This post hoc analysis of CLARITY and ORACLE-MS safety populations assessed the incidence of TEAEs, serious TEAEs, drug-related TEAEs, and TEAEs leading to discontinuation in patients receiving cladribine tablets or placebo within 2, 6, and 12 weeks after treatment initiation. Results By Week 12, 61.3% of patients treated with cladribine tablets 3.5 mg/kg and 55.2% treated with placebo experienced a TEAE. More patients receiving cladribine tablets versus placebo experienced a drug-related TEAE by Week 12 (34.7% vs. 23.2%). The most common TEAEs reported with cladribine tablets were: headache (7.2%), lymphopenia (6.8%), and nausea (6.0%). Patients receiving cladribine tablets and placebo reported similar proportions of serious TEAEs (2.2% vs. 1.7%) and TEAEs leading to treatment discontinuation (1.6% vs. 1.4%). Conclusion Cladribine tablets were well tolerated during the first 12 weeks as evidenced by a low incidence of TEAEs leading to treatment discontinuation.