Delayed access and adherence are real-world challenges that compromises effectiveness of natalizumab in multiple...

High efficacy therapy can prevent disability in multiple sclerosis patients, but timing and adherence are imperative. This study assessed the impact of delayed access and non-adherence in the treatment of multiple sclerosis using natalizumab in a tertiary Brazilian center.

We conducted a retrospective, single-center observational study using medical records of multiple sclerosis patients treated at a public tertiary center in São Paulo, Brazil. Data collected included demographics, disease course, treatment history, relapses, clinical and radiological activity, adherence, adverse events, and disability progression. A sample size of 88 was estimated to detect differences in the frequency of Expanded Disability Status Scale (EDSS) ≥ 6 between early and late natalizumab treatment groups, defined by a 48-month cutoff from symptom onset to natalizumab initiation. Statistical analyses included Mann-Whitney, Fisher's, and Chi-squared tests.

A total of 88 patients were included in this study. The majority of patients (n = 69, 78 %) initiated natalizumab late in the disease course. The late-treatment group had a higher frequency of EDSS ≥ 6 at the last follow-up compared to the early-treatment group (32 % vs. 11 %, p = 0.024). One-fourth of patients were non-adherent, with a threefold higher risk of experiencing a relapse during treatment (55 % vs. 17 %, p < 0.001). The primary reason for natalizumab discontinuation was the perceived risk of progressive multifocal leukoencephalopathy (72 %), though no cases were reported.

Enhancing early access and adherence to natalizumab is essential to maximize its real-world benefits for multiple sclerosis patients.