Alpha-4 integrin-targeted monoclonal antibody therapy, which prevents lymphocyte trafficking across the blood-brain barrier, remains among the most efficacious therapies for relapsing-remitting multiple sclerosis (RRMS). Its benefit is counterbalanced by the risk of progressive multifocal leukoencephalopathy, stratified by anti-JCV antibody index, treatment duration, and prior immunosuppressant exposure.

A decade-spanning real-world cohort (104 RRMS patients; median follow-up 5.2 years) shows persistent seropositivity in 51.9%, seronegativity in 37.5%, and seroconversion of only 6.7%, with no PML cases. Treatment-naïve patients showed fewer relapses, lower MRI activity, and higher NEDA-3 rates (64.6% vs 32.7%) versus previously treated patients, confirming early high-efficacy therapy benefit. These real-world findings reinforce the value of sustained anti-JCV antibody index surveillance, extended-interval dosing consideration in high-index patients, and the benefit of early versus late high-efficacy therapy initiation. Neurologists and MS specialists managing RRMS will benefit from peer discussion of JCV surveillance strategies, benefit-risk optimization, and approaches to treatment duration and switching.

How do you incorporate anti-JCV antibody index trends into your long-term benefit-risk discussions, and at what threshold or pattern do you consider treatment modification or switching? What factors most influence your decision to initiate alpha-4 integrin antagonism as an early high-efficacy strategy versus a step-up approach in newly diagnosed or treatment-naïve RRMS patients?