Safety and efficacy of oral cladribine in relapsing multiple sclerosis: a systematic review and meta-analysis

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system through persistent inflammation and demyelination. Cladribine, an immunosuppressive agent, has emerged as a promising high-efficacy disease-modifying therapy. However, concerns remain regarding its long-term safety, particularly the risks of lymphopenia, infections, and malignancy. This study aimed to evaluate the efficacy and safety of oral cladribine, including a control group defined by placebo, fingolimod, and natalizumab, by analyzing the impact of cladribine on the annualized relapse rate, relapse-free rate, expanded disability status, and adverse outcomes, such as malignancy, infections, and persistent lymphopenia.

This systematic review and meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. The databases PubMed, Web of Science, and Google Scholar were comprehensively searched to identify randomized controlled trials and observational studies comparing oral cladribine with other MS treatments or placebo.

This study included 24,976 patients with MS. Cladribine significantly reduced annualized relapse rates (mean difference [MD] = - 0.09; P = 0.0004), especially versus placebo (MD = - 0.15; P = 0.0002). No overall difference in Expanded Disability Status Scale was identified, although fingolimod showed better post-treatment outcomes (MD = 0.40; P < 0.00001). Relapse-free rates were similar, except in the placebo subgroup favoring cladribine (MD = 2.46; P < 0.00001). Cladribine was associated with an increased risk of persistent lymphopenia (odds ratio [OR] = 20.20; P < 0.00001), whereas infection (OR = 1.18; P = 0.78) and malignancy rates (OR = 1.87; P = 0.63) were comparable to those of the controls. The interpretation was limited by study heterogeneity and the absence of a pooled analysis of several secondary outcomes.

Cladribine may be a valuable therapeutic option for relapsing-remitting MS with a strong efficacy profile. The lymphopenia incidence highlights the need for regular hematological monitoring to ensure the safety of cladribine.