Gefurulimab Meets All Endpoints in Phase III Global Trial for Generalised Myasthenia Gravis

AstraZeneca’s rare disease division, Alexion, has announced promising high-level results from its global Phase III trial evaluating gefurulimab in adults with anti-acetylcholine receptor (AChR) antibody-positive generalised myasthenia gravis (gMG). The investigational drug met its primary and all secondary endpoints, showing statistically significant and clinically meaningful improvements in disease activity compared to placebo.

Key Highlights from the PREVAIL Trial

• Trial Design: Global, randomised, double-blind, placebo-controlled Phase III study
• Patient Population: Adults with AChR-Ab+ gMG from 20 countries
• Sample Size: 260 patients
• Duration: 26 weeks
• Primary Endpoint: Improvement from baseline in Myasthenia Gravis Activities of Daily Living (MG-ADL) score at week 26
• Result: Gefurulimab significantly outperformed placebo on all clinical endpoints

A Debilitating Autoimmune Condition

Generalised myasthenia gravis is a rare, chronic autoimmune neuromuscular disorder that causes severe muscle weakness. It affects the neuromuscular junction (NMJ), leading to symptoms such as:

• Slurred speech
• Double vision
• Drooping eyelids
• Difficulty swallowing
• Choking
• Respiratory failure

Approximately 85% of gMG patients are AChR antibody-positive, meaning their immune system produces antibodies that trigger a complement-mediated attack on the NMJ. This disrupts communication between nerves and muscles, resulting in fluctuating and potentially life-threatening symptoms.

A Patient-Centric Approach to Treatment

Dr. Kelly Gwathmey, principal investigator and Associate Professor of Neurology at Virginia Commonwealth University, stated:

“Rapidly fluctuating symptoms and the unpredictable disability associated with gMG can affect nearly every aspect of a patient's life. A once-weekly, self-administered C5 treatment would offer patients greater convenience and independence in managing their condition.”

Mechanism of Action and Dosing

Gefurulimab is a novel dual-binding nanobody and C5 complement inhibitor:

• Binds to C5 protein in the terminal complement cascade
• Co-binds to serum albumin, enabling extended half-life
• Designed for once-weekly subcutaneous self-administration

This design allows for both rapid disease control and reduced treatment burden. No new safety signals were observed, and the drug was well tolerated in line with prior C5 inhibitor studies.

Company Leadership on the Breakthrough

Marc Dunoyer, CEO of Alexion, commented:

“These results from the PREVAIL trial demonstrate the potential for gefurulimab to offer rapid and sustained disease control. With data from 20 countries, this reinforces gefurulimab’s safety and supports its potential as a first-line biologic.”

What’s Next?

Participants who completed the 26-week treatment are now entering an open-label extension to further assess the long-term safety and efficacy of gefurulimab. The full data set will be shared at an upcoming medical meeting and submitted to regulatory authorities worldwide.

Gefurulimab has already received Orphan Drug Designation in the US for treating myasthenia gravis.

About the PREVAIL Study

• Name: ALXN1720-MG-301
• Type: Global, multicentre, Phase III trial
• Eligibility: Patients with confirmed AChR-Ab+ gMG, MGFA Class II–IV
• Design: 1:1 randomisation to gefurulimab or placebo
• Treatment Regimen: One-time weight-based loading dose (Day 1), followed by weekly maintenance dosing (from Day 8 onward)

About Alexion, AstraZeneca Rare Disease

Alexion is a global leader in rare diseases, known for pioneering complement inhibition therapies. The company continues to build a diverse pipeline using advanced modalities to address diseases with high unmet medical need.

About AstraZeneca

AstraZeneca is a science-led biopharmaceutical company focused on prescription medicines across oncology, rare diseases, and major therapy areas including cardiovascular, renal, metabolism, respiratory, and immunology.

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