Long-Term Safety and Efficacy of Subcutaneous Cladribine Used in Increased Dosage in Patients with Relapsing Multiple Sclerosis: 20-Year Observational Study

Cladribine is currently registered as a 10-milligram tablet formulation with a fixed cumulative dosage of 3.5 mg/kg over 2 years. It is important to investigate if an increased dosage may lead to further clinical stability with preserved safety. This study used an off-label subcutaneous (s.c.) formulation of cladribine and compared outcomes (Expanded Disability Status Scale (EDSS) scores and disease progression) between 52 relapsing multiple sclerosis (RMS) patients receiving different s.c. dosing regimens with up to 20 years of follow-up. The study group received induction therapy with s.c. cladribine (1.8 mg/kg cumulative dose; consistent with 3.5 mg/kg of cladribine tablets). Patients were subsequently offered maintenance therapy (repeated courses of 0.3 mg/kg s.c. cladribine during 5-20-year follow-up). Forty-one patients received an increased cumulative dose (higher than the induction dose of 1.8 mg/kg); 11 received the standard induction dose. Risk of progression on the EDSS correlated with lower cumulative dose (p < 0.05) and more advanced disability at treatment initiation (p < 0.05) as assessed by EDSS change between year 1 and years 5 and 10 as the last follow-up. Maintenance treatment was safe and well-tolerated, based on limited source data. Subcutaneous cladribine with increased cumulative maintenance dosage was associated with disease stability and favorable safety over a prolonged period of follow-up (up to 20 years) in RMS patients.