ARTIOS was a 96-week, phase 3b, open-label, single-arm study evaluating the efficacy (primary endpoint: ARR) and safety of ofatumumab 20 mg SC monthly in 562 adults with RMS who had breakthrough disease on fingolimod (n=181) or fumarates (n=381).
The primary endpoint was met: overall adjusted ARR was 0.06 (95% CI: 0.05–0.08; p<0.0001), declining further from Year 1 (0.10) to Year 2 (0.02). Gd+ T1 lesions were suppressed by 98.1% at Week 96 vs. baseline. NEDA-3 was achieved by 90.9% of participants in Year 2. Only 7.3% experienced 6-month confirmed disability worsening. Serious TEAEs occurred in 5.9%; no deaths were reported.
- Single-arm, non-comparative design prevents definitive conclusions about superiority over other high-efficacy therapies or direct DMT-subgroup comparisons. - Enrollment during the COVID-19 pandemic inflated infection rates, complicating safety interpretation. - Regression to the mean cannot be excluded, as participants were enrolled during active breakthrough disease.
For RMS patients failing fingolimod or fumarates, switching to ofatumumab produces a very low relapse rate and near-complete MRI suppression, with >90% achieving NEDA-3 by Year 2 and a manageable safety profile. A washout of <30 days from fingolimod may reduce rebound risk and appears safe based on post hoc data.
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