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In the open-label extension of the phase III PREVAIL trial, participants with anti-AChR antibody-positive generalized myasthenia gravis maintained improvements on three disease scales through 52 weeks of gefurulimab treatment. The longer-term results were reported at an AANEM meeting; the drug is investigational in the United States, where it remains under FDA review.
People with anti-AChR antibody-positive generalized myasthenia gravis maintained improvements on three measures of disease-related function through 52 weeks of gefurulimab treatment, according to results from the open-label extension of the phase III PREVAIL trial. Tuan Vu, MD, of the University of South Florida presented the findings at an American Association of Neuromuscular and Electrodiagnostic Medicine meeting; gefurulimab remains investigational in the United States.
At one year, scores had improved from baseline by 5.3 points on the MG-ADL scale, which ranges from 0 to 24; by 5.3 points on the QMG scale, which ranges from 0 to 39; and by 9.4 points on the MGC scale, which ranges from 0 to 50, Vu reported. Lower scores on these measures reflect fewer or less severe symptoms and functional limitations. The results describe changes in trial scores, not a guarantee that every participant experienced the same benefit.
Participants originally assigned to placebo for the 26-week randomized phase began gefurulimab in the extension. By week 52, their scores had improved from the original baseline by 4.9 points on MG-ADL, 4.6 points on QMG and 8.3 points on MGC. Vu said improvements appeared at the first assessments after the switch and were maintained through the end of the reported period.
Of 249 people who completed PREVAIL’s randomized phase, all entered the extension. At the November 2025 data cutoff, 211 remained on treatment. Median treatment duration among patients receiving gefurulimab was 575 days. Vu said the safety profile was consistent with the randomized phase and that no new safety signals had emerged.
One-Year Results Across Three Scales
The extension offers evidence about whether measured benefits continued beyond PREVAIL’s initial 26-week controlled period. Sustained changes on MG-ADL, QMG and MGC may matter to patients and clinicians evaluating a treatment intended to reduce the effects of generalized myasthenia gravis on daily activities and muscle function.
However, the extension was open-label: participants knew they were receiving gefurulimab, and there was no placebo comparison during this longer period. The findings support continued improvement among those treated but cannot establish from this phase alone how outcomes compare with no treatment or another therapy over a year. Longer follow-up and regulatory decisions will help determine the drug’s place among complement inhibitors.
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From Controlled Trial to Extension
PREVAIL randomized 260 adults with anti-AChR antibody-positive generalized myasthenia gravis to weekly self-administered under-the-skin gefurulimab or placebo for 26 weeks. The primary endpoint was change in MG-ADL score at week 26, with QMG change a key secondary endpoint. The trial met its primary and secondary endpoints, and reported improvements appeared within one week on MG-ADL and within four weeks on QMG, then continued through week 26.
Gefurulimab is an investigational C5-blocking nanobody that also binds serum albumin, a feature intended to extend its half-life and support weekly dosing. C5 inhibitors are used to treat anti-AChR-positive generalized myasthenia gravis; eculizumab, ravulizumab and zilucoplan are approved by the FDA for the condition. These medicines carry a boxed warning about meningococcal infection risk, and vaccination recommendations apply. No meningococcal infections were reported in the randomized PREVAIL period.
“The safety profile was consistent with the randomized controlled period of the study, with no emerging safety signals.”
— Tuan Vu, MD, University of South Florida, presenting PREVAIL extension results
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Limits of the Extension Evidence
The reported one-year results come from an open-label extension, not a continued randomized comparison. The supplied report does not provide detailed results for every participant who entered the extension, reasons some patients were no longer receiving treatment by the cutoff, or a full breakdown of adverse events over the longer follow-up. It also does not establish whether the score changes translated into the same degree of benefit for all participants.
Regulatory status is also unsettled. The European Medicines Agency’s Committee for Medicinal Products for Human Use recommended gefurulimab for EU approval in September, while the drug is under FDA review. The source material does not specify a final decision date or approval outcome.
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Regulatory Review and Longer Follow-Up
The next major developments are the FDA’s decision on gefurulimab and any final European Union authorization following the committee recommendation. Until regulators act, the drug remains investigational in the United States. Additional published data may clarify longer-term safety, how many participants continued treatment, and how the therapy compares with other options.
For now, PREVAIL’s extension adds follow-up beyond the controlled trial period but does not answer all questions about comparative effectiveness or the treatment’s eventual place in care. Any future claims about those issues will depend on regulatory assessments and further evidence.
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Key Questions
What did the gefurulimab extension results show?
Participants maintained improvements through 52 weeks on MG-ADL, QMG and MGC scales. The figures reported are average score changes from baseline, not a promise of an individual outcome.
How many participants entered the extension?
All 249 participants who completed PREVAIL’s randomized 26-week period entered the open-label extension. At the November 2025 cutoff, 211 had continued treatment.
Is gefurulimab approved for myasthenia gravis?
It remains investigational in the United States and is under FDA review. In Europe, the EMA’s medicines committee recommended it for approval in September, but the supplied material does not report a final authorization.
Does the extension prove gefurulimab is better than other treatments?
No. The extension was open-label and did not continue a placebo comparison. Its results show sustained score improvements among treated participants but do not establish superiority over another treatment.
What safety information was reported?
Investigators said the extension’s safety profile was consistent with the randomized phase, with no emerging safety signals. The earlier phase reported injection-site reactions, headache, back pain and nasopharyngitis among common treatment-emergent events; the report says no meningococcal infections occurred in that phase.
Source: rss
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