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Open-label ADAPT SERON data suggest that some people with generalized myasthenia gravis who lack detectable AChR antibodies may respond more slowly to intravenous efgartigimod than patients who responded in the original ADAPT trial. James F. Howard Jr. said clinicians may need to allow three or four treatment cycles before deciding the drug is not helping, while weighing the risk of delaying another treatment.
Some patients with generalized myasthenia gravis who have no detectable acetylcholine receptor (AChR) antibodies may need more time to respond to intravenous efgartigimod, according to open-label findings from the ADAPT SERON trial discussed at the American Association of Neuromuscular & Electrodiagnostic Medicine annual meeting. James F. Howard Jr., MD, of the University of North Carolina at Chapel Hill, said clinicians may need to consider three or four treatment cycles before concluding the drug is not working for these patients.
The ADAPT SERON data indicate that efgartigimod continued to show efficacy and a safety profile with no new signals reported among patients with generalized myasthenia gravis who did not have detectable AChR antibodies. The findings were described as open-label data at the annual meeting; the source report does not provide numerical response rates, the number of patients, or detailed safety figures.
Howard contrasted the possible response timing in this group with results from the original ADAPT trial, where most patients who responded experienced meaningful improvement within the first treatment cycle. In patients without AChR antibodies, he said, improvement may take two or three cycles to become apparent. He suggested it could be appropriate to wait as long as three or four cycles, or about six months, before judging treatment ineffective, depending on the patient’s course.
That is not a direction to continue treatment for every patient. Howard stressed that clinicians also need to identify people who are not responding, to avoid losing time or exposing them to potential adverse effects without benefit. The practical message is to avoid making an early decision based only on the response pattern seen in patients who improve quickly, while continuing to assess each patient’s response and safety.
Allowing Time to See a Response
The findings could affect how clinicians judge treatment response in a group with limited targeted options. Howard described people without detectable AChR, muscle-specific tyrosine kinase (MuSK), or lipoprotein receptor-related protein 4 (LRP4) antibodies as a small minority—about 10% of the myasthenia gravis population—who have had fewer opportunities to use newer targeted therapies. The estimate and characterization come from Howard’s remarks in the report.
If some patients respond later than those in the original ADAPT trial, stopping after two cycles could mean ending treatment before its potential benefit becomes clear. But waiting longer also has costs: symptoms may remain inadequately controlled, and patients may continue a therapy that is not helping. The report does not establish a single waiting period suitable for everyone; it highlights a clinical judgment problem that must balance time to response against the need to change ineffective treatment.
The data may also influence research interest in AChR-negative disease. Howard said other companies are studying the seronegative or AChR-negative population in trial designs. The findings therefore matter both to current treatment decisions and to how future studies account for a population that may respond on a different timeline.
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The ADAPT SERON Findings
Efgartigimod, sold as Vyvgart, is an intravenous treatment studied in generalized myasthenia gravis. The report focuses on ADAPT SERON, an open-label trial involving patients without detectable AChR antibodies. The findings were presented at the American Association of Neuromuscular & Electrodiagnostic Medicine annual meeting and discussed by Howard in an interview published by MedPage Today on October 27, 2026.
Antibody status is relevant because myasthenia gravis is an autoimmune disease, and different antibodies can be associated with different disease mechanisms. Howard said the response observed in patients without detectable antibodies to AChR, MuSK, or LRP4 supports the possibility that antibodies remain involved in the disease process, but he also described the underlying biology as unresolved. He noted that complement activation is established in AChR-associated disease, while its role in people with no detectable antibodies remains uncertain.
The timing issue arises from a contrast: many responders in the original ADAPT trial improved during the first cycle, while the ADAPT SERON subgroup may take longer. The report does not give enough trial detail to compare response rates directly or determine how often delayed improvement occurred.
“We don’t want to waste time. We don’t want to subject them to potential adverse events of a therapeutic that’s not going to be of benefit.”
— James F. Howard Jr., MD
Response Timing and Trial Limits
The report does not specify how many participants were included, what proportion responded, how large or durable improvements were, or how results differed among antibody subgroups. Because the findings are described as open-label, the information provided here does not establish how the results compare with a control group. The available account also does not define a formal response threshold or show that waiting three or four cycles improves outcomes.
It remains unclear why some AChR-negative patients may respond more slowly. Howard said the mechanism is still being studied. He discussed possible antibody involvement and complement activity, but said the role of complement in people with no detectable antibodies is not known for sure. The claim that antibody may drive disease in these patients is a proposed interpretation, not a settled explanation.
The report also does not identify which patients are most likely to benefit from a longer trial of treatment, or what clinical signs should prompt an earlier change. The safety comments are Howard’s summary; detailed adverse-event data were not included in the source material.
Further Data and Clinical Decisions
More detailed results from ADAPT SERON would be needed to clarify response rates, timing, durability, and safety across the antibody subgroups. Any additional trial reports or publications could help establish whether delayed responses are common enough to guide treatment decisions and whether particular patient characteristics predict them.
For now, Howard’s remarks point to individualized monitoring rather than a fixed rule to continue or stop after a set number of cycles. Clinicians and patients will need to weigh observed improvement, ongoing disease burden, potential adverse effects, and available alternatives. The source report does not identify a specific next publication date or regulatory decision related to these findings.
Key Questions
What did the ADAPT SERON findings suggest?
The open-label findings suggest that intravenous efgartigimod continued to show efficacy and no new safety signals in the reported group with generalized myasthenia gravis and no detectable AChR antibodies. Some patients may take longer to show meaningful improvement.
How many treatment cycles might be needed before judging a response?
Howard said some patients may need three or four cycles, potentially about six months, before clinicians decide the treatment is not working. This was his interpretation of the findings, not a universal rule established by the report.
Why might these patients respond more slowly?
The reason is not known. Howard discussed possible antibody-related disease activity, but said the biology—particularly the role of complement in people with no detectable AChR, MuSK, or LRP4 antibodies—remains under study.
Does the report show that efgartigimod is safe for every patient?
No. Howard said the subgroup data showed no new safety signals, but the report did not provide detailed adverse-event rates. Individual treatment decisions require clinical monitoring and assessment of risks and benefits.
Source: medpagetoday.com
