Updates on immunosuppressant safety and malignancy risk in patients with multiple sclerosis.

[INTRODUCTION] Multiple sclerosis (MS) is a chronic, immune-mediated disease of the central nervous system, characterized by relapses or progressive neurological decline. Over recent decades, high-efficacy immunosuppressive therapies have dramatically reduced relapse rates and curtailed new MRI lesion activity in MS, but also raise safety concerns regarding infections, malignancy, and other serious adverse events.

[AREAS COVERED] This review discusses immunosuppressants in MS, from older cytotoxic agents (azathioprine, cyclophosphamide, mitoxantrone) to newer therapies (cladribine, alemtuzumab, and anti-CD20 monoclonal antibodies). Key efficacy data are summarized, alongside risks of hematologic, hepatic, and autoimmune toxicities. Emerging evidence on malignancy risk is highlighted, including therapy-related acute leukemias (mitoxantrone), urothelial tumors (cyclophosphamide), and potential neoplasms linked to newer agents. Strategies for patient selection, screening, and long-term vigilance are examined to balance high-efficacy disease control with acceptable safety margins.

[EXPERT OPINION] Immunosuppressants remain vital for certain MS phenotypes, especially those with highly active or refractory disease. Although novel agents offer more selective mechanisms, they still pose notable risks demanding careful monitoring and individualized care. Ongoing research, including predictive biomarkers and post-marketing surveillance, will refine patient selection and mitigate adverse events. With judicious use and robust safety protocols, clinicians can achieve durable disease control while minimizing long-term toxicities.