Alexion’s Dual-Binding Nanobody Demonstrates Statistically Significant Improvements in Generalized Myasthenia Gravis

Results from the Phase III PREVAIL trial showed that gefurulimab, a dual-binding nanobody developed by Alexion, AstraZeneca Rare Disease, led to statistically significant and clinically meaningful improvements in patients with generalized myasthenia gravis (gMG). According to the company, the therapy met its primary and all secondary endpoints, with meaningful gains observed in Myasthenia Gravis Activities of Daily Living (MG-ADL) scores at 26 weeks compared with placebo.¹

Can Gefurulimab Offer a New Standard of Care for Patients with gMG?

“Rapidly fluctuating symptoms and the unpredictable disability associated with gMG can affect nearly every aspect of a patient’s life, making early intervention and sustained disease control a critical treatment goal,” said Kelly Gwathmey, MD, associate professor, neurology, chief, neuromuscular division, Virginia Commonwealth University, in a press release. “A once-weekly, self-administered C5 treatment option would offer patients greater convenience and independence in managing their condition, empowering them to have more control over their therapy.”

PREVAIL Trial Design and Key Endpoints

• The global, randomized, double-blind, placebo-controlled, parallel, multicenter PREVAIL trial evaluated the safety and efficacy of gefurulimab in 260 adults with gMG.
• All patients were required to have a confirmed myasthenia gravis diagnosis at least three months prior to the screening visit with a positive serological test for autoantibodies against AChR and Myasthenia Gravis Foundation of America Clinical Classification Class II to IV at screening.
• Patients were randomly assigned 1:1 to receive either gefurulimab or placebo for a total of 26 weeks.
• The primary endpoint of the trial was the change from baseline in the MG-ADL total score.
• Key secondary endpoints included a change from baseline in quantitative myasthenia gravis (QMG) total score at week 26, percentage of responders based on reduction of the MG-ADL total score at week 26, percentage of responders based on reduction of the QMG total score at week 26, change from baseline in myasthenia gravis composite total score at week 26, and change from baseline in the QMG total score at week four.

Safety Results and Next Steps

• Gefurulimab was generally well-tolerated, with a safety profile in line with earlier studies of C5 inhibitors in generalized myasthenia gravis and no unexpected safety concerns identified.
• The full results will be presented at an upcoming medical conference and submitted to regulatory agencies worldwide.^1,2

Myasthenia Gravis Overview and Population Insights

According to the Myasthenia Gravis Foundation of America, around 150 to 200 out of every million people are affected by myasthenia gravis globally. In the United States, the estimated number is 37 out of every 100,000 people. While people of any age can be affected by it, it is most common in women under 50 years of age and men over 65 years of age. Overall, it is most common in people aged 50 years and older.

Myasthenia gravis can impact individuals across all racial and ethnic groups, though it appears to occur somewhat more frequently among people of African descent. Studies suggest that certain features of the disease may differ based on ethnicity—for instance, African Americans may be diagnosed at a younger age and are more likely to have muscle-specific tyrosine kinase antibodies compared to white individuals.³

Industry Perspective on Gefurulimab’s Promise

“Building on Alexion’s pioneering leadership in gMG, these positive results from the PREVAIL Phase III trial demonstrate the potential for gefurulimab to offer rapid and sustained disease control for this patient community,” said Marc Dunoyer, CEO, Alexion, AstraZeneca Rare Disease, in the press release. “These data, reflecting patient participation across 20 countries, reinforce the established safety profile and efficacy of C5 inhibition and show the potential for gefurulimab as a first line biologic, with the convenience of a self-administered option.”

References

1. Gefurulimab dual-binding nanobody demonstrated statistically significant and clinically meaningful improvement in functional activities of daily living in adults with generalised myasthenia gravis in PREVAIL Phase III trial. AstraZeneca. July 24, 2025. Accessed July 25, 2025. https://www.astrazeneca.com/media-centre/press-releases/2025/gefurulimab-nanobody-met-phase-iii-endpoints.html
2. Safety and Efficacy of ALXN1720 in Adults With Generalized Myasthenia Gravis. Clinicaltrials.gov. Accessed July 25, 2025. https://clinicaltrials.gov/study/NCT05556096?term=ALXN1720-MG-301&rank=1
3. Overview of MG. Myasthenia Gravis Foundation of America. Accessed July 25, 2025. https://myasthenia.org/understanding-mg/overview-mg/