Alexion, AstraZeneca Rare Disease’s Klygefa (gefurulimab) has been recommended for approval in the European Union (EU) as an add-on to standard therapy for the treatment of generalised Myasthenia Gravis (gMG) in adults who are anti-Acetylcholine Receptor (AChR) antibody-positive.

If approved by the European Commission, Klygefa would be the first and only dual-binding nanobody C5 inhibitor for this patient population.

The positive opinion from the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) was based on results from the pivotal Phase 3 PREVAIL trial. The findings were presented at the Myasthenia Gravis Foundation of America (MGFA) Scientific Session during the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 2025 Annual Meeting and published in JAMA Neurology.

In the PREVAIL trial, Klygefa met its primary endpoint, demonstrating a statistically significant improvement from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) total score at week 26 compared with placebo. The treatment difference was -1.6 (95 percent CI: -2.4, -0.8; p<0.0001). A clinically meaningful improvement was observed as early as week one and was sustained through week 26.

Klygefa was generally well tolerated, with its safety profile consistent with previous clinical experience with the C5 inhibitors eculizumab and ravulizumab in gMG.

gMG is a rare autoimmune disorder characterised by reduced muscle function and severe muscle weakness. An estimated 82,500 people are diagnosed with gMG across Germany, France, the UK, Italy and Spain, of whom approximately 66,000 are AChR-positive.

Around 85 percent of people with gMG are AChR antibody-positive. In these patients, anti-AChR antibodies bind to receptors at the neuromuscular junction, activating the complement system and contributing to damage at the connection between nerves and muscles. Symptoms can include double vision, drooping eyelids, slurred speech, impaired swallowing, severe fatigue and respiratory complications.

The PREVAIL trial enrolled 260 adults with gMG across 20 countries in North America, Europe, Asia and the Pacific region. Participants were randomised 1:1 to receive Klygefa or placebo for 26 weeks. Treatment consisted of a weight-based loading dose on Day 1, followed by weight-based maintenance dosing from Day 8 and once weekly thereafter. Patients completing the randomised treatment period could enter an ongoing open-label extension study.

Klygefa is a complement C5 inhibitor and a dual-binding nanobody designed for subcutaneous self-administration. It binds to the C5 protein in the terminal complement pathway, while concurrent binding to serum albumin extends its half-life and enables once-weekly dosing.

Klygefa is already approved in Japan and other countries for certain adults with gMG. Regulatory submissions based on the PREVAIL results are also under review in the US, China and other markets.