Efficacy and Safety of Gefurulimab in Generalized Myasthenia Gravis

Importance: Gefurulimab is a novel dual-binding nanobody that blocks complement component 5 activation. Complement activation is a key pathogenic mechanism in anti-acetylcholine receptor antibody-positive (AChR-Ab+) generalized myasthenia gravis (gMG). Objective: To evaluate the efficacy and safety of gefurulimab in adults with AChR-Ab+ gMG. Design, Setting, and Participants: This randomized clinical trial, PREVAIL, was a phase 3, double-blind, placebo-controlled study conducted at 113 sites in 20 countries. Patients were screened and randomized from November 2022 to November 2024; the randomized controlled treatment period was 26 weeks. Participants were adults (aged ≥18 years) with AChR-Ab+ gMG, a Myasthenia Gravis Foundation of America classification II through IV, and a Myasthenia Gravis Activities of Daily Living (MG-ADL) total score of 5 or higher. Intervention: Gefurulimab or placebo via once-weekly subcutaneous self-injection. Main Outcomes and Measures: The primary end point was change from baseline in MG-ADL total score at week 26. The key secondary end point was change from baseline in Quantitative Myasthenia Gravis (QMG) total score at week 26. Safety was also assessed. Results: Of 405 patients screened, 145 were excluded; 260 met eligibility criteria and were randomized (gefurulimab, n = 131; placebo, n = 129); 249 patients completed the 26-week randomized controlled treatment period. The mean (SD) age was 52.8 (15.73) years; 157 (60.4%) patients were female and 103 (39.6%) were male. All primary and secondary end points were met with statistical significance. Improvements occurred within 1 week for MG-ADL score and 4 weeks for QMG score and were sustained through week 26. Least-squares mean change from baseline at week 26 for MG-ADL and QMG total scores for gefurulimab vs placebo were -4.2 vs -2.6 (treatment difference, -1.6; 95% CI, -2.4 to -0.8; P < .001) and -4.5 vs -2.4 (treatment difference, -2.1; 95% CI, -3.1 to -1.1; P < .001), respectively. The incidence of adverse events (AEs) was similar between groups. Most common treatment-emergent AEs with gefurulimab were injection site reactions, headache, back pain, and nasopharyngitis. No meningococcal infections were reported. Conclusions and Relevance: Gefurulimab demonstrated both early and sustained clinical benefit in AChR-Ab+ gMG and was well tolerated, supporting its potential as a convenient, once-weekly, self-administered treatment regimen. Trial Registration: ClinicalTrials.gov Identifier: NCT05556096.