CHMP Backs AstraZeneca’s Klygefa for Rare Disorder

The European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion on 17 September 2026 recommending EU marketing authorisation for Klygefa (gefurulimab), developed by Alexion, AstraZeneca Rare Disease, as an add-on therapy for adults with generalised myasthenia gravis (gMG) who test positive for anti-acetylcholine receptor (AChR) antibodies. The opinion came out of CHMP's 14-17 September plenary in Amsterdam, one of twelve new medicines the committee recommended at that single meeting.

What a dual-binding nanobody changes

Complement inhibition is not new in generalised myasthenia gravis — eculizumab and ravulizumab, both C5 inhibitors, are already established options — but both require intravenous infusion at a clinic. Gefurulimab's mechanism is what makes home dosing possible: as a nanobody, it is a fraction of the size of a full antibody, and engineering it to bind serum albumin alongside its complement target gives it a long enough half-life in circulation to hold C5 inhibition for a full week between subcutaneous injections. AstraZeneca has described it as the first dual-binding nanobody C5 inhibitor authorised for gMG in the EU, though that framing is the company's own and has not been independently adjudicated; what is independently verifiable is that the delivery route — a once-weekly injection a patient can give themselves — is new to this drug class in this indication.

The PREVAIL data

PREVAIL was a randomized, double-blind, placebo-controlled phase 3 trial. Its primary endpoint, change from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score at week 26, showed a 1.6-point treatment difference favoring gefurulimab (95% CI -2.4 to -0.8, p<0.0001) — MG-ADL is a patient-reported measure of everyday function, so that gap reflects a difference patients can feel, not just a lab value. A key secondary endpoint, the Quantitative Myasthenia Gravis (QMG) score, moved in the same direction and showed a measurable treatment effect as early as week 4 that held through week 26. The trial data were first presented at the Myasthenia Gravis Foundation of America's scientific session in October 2025 and have since been published in the peer-reviewed literature.

What a positive opinion is, and isn't

A CHMP positive opinion is a recommendation, not an authorisation. The European Commission makes the final, legally binding decision, and under the centralised procedure's standard timeline that decision typically follows within roughly 67 days of the CHMP vote — putting a Klygefa decision plausibly in mid-November, though AstraZeneca has not confirmed a specific date and the estimate is procedural rather than product-specific. Once the Commission decides, EMA will publish the full European Public Assessment Report (EPAR), including the summary of product characteristics and risk-management plan, neither of which is yet available. For RA teams tracking rare-disease neurology, the practical marker to watch is the EC decision itself, not this opinion; that is the date the authorisation, and any post-marketing commitments attached to it, actually takes effect.

Frequently asked questions

What did CHMP recommend on 17 September 2026?

A positive opinion for Klygefa (gefurulimab), from Alexion, AstraZeneca Rare Disease, as an add-on to standard therapy for adults with AChR-antibody-positive generalised myasthenia gravis.

What is gefurulimab, and how is it different from existing complement inhibitors?

A nanobody that binds both the C5 complement protein and serum albumin, extending its half-life enough to allow once-weekly, self-administered subcutaneous dosing rather than infusion.

What evidence supported the opinion?

The phase 3 PREVAIL trial. Its primary endpoint, MG-ADL score at week 26, favored gefurulimab by 1.6 points over placebo (95% CI -2.4 to -0.8, p<0.0001).

What happens next?

The European Commission must issue the final marketing authorisation decision, typically within about 67 days of a CHMP opinion under the standard procedure. No specific date has been confirmed for Klygefa.