Design: Phase 3, double-blind, placebo-controlled RCT, 113 sites
Population: 260 adults with AChR-Ab+ generalised myasthenia gravis
Primary outcome: Change in MG-ADL at week 26
Effect: −4.2 vs −2.6; difference −1.6 (95% CI −2.4 to −0.8)

PREVAIL was a phase 3, double-blind, placebo-controlled trial at 113 sites in 20 countries. It randomised 260 adults with acetylcholine receptor antibody-positive generalised myasthenia gravis (MGFA class II to IV, MG-ADL 5 or more) to once-weekly subcutaneous gefurulimab, a dual-binding nanobody that blocks complement C5, or placebo for 26 weeks. It was published in JAMA Neurology in September.

MG-ADL fell by 4.2 points with gefurulimab and 2.6 with placebo (difference −1.6, 95% CI −2.4 to −0.8). QMG fell by 4.5 versus 2.4 (difference −2.1, −3.1 to −1.1). MG-ADL improvement was seen within a week. Adverse events were similar; no meningococcal infections occurred.

The advance is convenience: a self-administered weekly injection rather than intravenous infusions. The treatment effect is in the range of existing C5 inhibitors. Its regulatory status with FDA or CDSCO is not stated in this record.

Complement inhibition applies only to AChR-antibody-positive disease.
Meningococcal vaccination remains mandatory with any C5 inhibitor.
Reserve for refractory disease despite standard immunosuppression.
Check regulatory status before discussing with patients.

Why it matters

Complement inhibition may move from infusion units to home self-injection.

The statistics, in plain English

A 1.6-point MG-ADL difference is modest; the placebo group also improved by 2.6 points, typical of myasthenia trials. The interval excludes zero, so the effect is real, but its size is similar to, not larger than, other C5 inhibitors. Twenty-six weeks says nothing about long-term infection risk.