Effects of Postponing Treatment in the Second Year of Cladribine Administration: Clinical Trial Simulation Analysis of Absolute Lymphocyte Counts and Relapse Rate in Patients with Relapsing-Remitting Multiple Sclerosis

INTRODUCTION: Cladribine Tablets (MAVENCLAD(®)) selectively reduce absolute lymphocyte counts (ALCs) in patients with multiple sclerosis. The recommended cumulative dose of Cladribine Tablets is 3.5 mg/kg over 4–5 days in months 1 and 2 of treatment years 1 and 2, followed by prolonged efficacy with no additional treatment. After the cladribine-induced reduction, ALCs recover to normal within each treatment year in most patients. Those patients with slow ALC recovery can develop Grade 3–4 lymphopenia, especially those patients with Grade ≥ 2 lymphopenia at the start of year 2. Guidelines allowing treatment postponements during year 2 have been proposed for patients with a low ALC, subsequent to CLARITY, the pivotal clinical trial. METHODS: A virtual population was generated using characteristics from CLARITY patients. A clinical trial simulation was performed to determine the impact of alternative treatment scenarios on ALC and relapse rate, by postponing treatment in year 2 to allow for longer ALC recovery time in patients who required it. Should a patient not recover to normal ALC (Grade 0) or Grade 1 lymphopenia within the period defined in the treatment algorithm, treatment in year 2 was suspended. RESULTS: Results were similar across considered scenarios, which implemented different postponement durations. Specifically, ~ 92% of virtual subjects did not require treatment postponement and < 1% discontinued due to Grade 2–4 lymphopenia at the end of the maximally permitted postponement. Less severe lymphopenia was observed during year 2 when a treatment algorithm was applied. The effect on relapse rate over 2 years was negligible. CONCLUSIONS: Results support treatment guidelines to decrease the risk of severe lymphopenia following treatment with Cladribine Tablets, while preserving efficacy. TRIAL REGISTRATION: CLARITY; ClinicalTrials.gov: NCT00213135. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40262-018-0693-y) contains supplementary material, which is available to authorized users.