Phase 3 RCT (PREVAIL) evaluating gefurulimab — a once-weekly subcutaneous complement C5-blocking nanobody — vs. placebo in 260 adults with AChR-Ab+ generalized myasthenia gravis over 26 weeks.
Gefurulimab met all primary and secondary endpoints: MG-ADL improved by −4.2 vs −2.6 (treatment difference −1.6; 95% CI −2.4 to −0.8; P<.001) and QMG by −4.5 vs −2.4 (treatment difference −2.1; 95% CI −3.1 to −1.1; P<.001) at week 26. Benefits appeared within 1 week (MG-ADL) and 4 weeks (QMG) and were sustained. No meningococcal infections occurred; adverse event rates were similar between arms.
- Trial duration was only 26 weeks; long-term efficacy and safety beyond this window are unknown. - Study was restricted to AChR-Ab+ patients, limiting generalizability to MuSK-Ab+ or seronegative gMG. - The absolute treatment difference on MG-ADL (−1.6 points) is modest and its clinical meaningfulness relative to established thresholds warrants consideration.
Gefurulimab offers a self-administered, once-weekly subcutaneous option for AChR-Ab+ gMG with rapid onset (within 1 week) and a favorable short-term safety profile. Clinicians should note its complement-blocking mechanism still requires meningococcal vaccination vigilance despite no infections in this trial.
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