FDA Clears Efgartigimod for All Adult Patients With Myasthenia Gravis

Adult patients with all serotypes of generalized myasthenia gravis (gMG) could soon benefit from the FDA’s latest approval of efgartigimod alfa-fcab (Vyvgart) and efgartigimod alfa and hyaluronidase-qvfc (Vyvgart Hytrulo), both from argenx, following a label expansion announced on Friday, May 8.¹

This decision clears both formulations for use in patients who are anti–acetylcholine receptor (AChR-Ab)–positive, anti–muscle-specific tyrosine kinase (MuSK)–antibody positive, anti–low-density lipoprotein receptor-related protein 4 (LRP4)–antibody positive, and triple seronegative.

These treatments are now the first and only regimens approved to treat adult patients with all serotypes of gMG, regardless of antibody status, according to the news release announcing the approvals. Argenx filed the supplemental biologics license application on January 13, 2026, and it was accepted for priority review,² following a similar path to the original biologics license application filed in November 2022.³ Data from the phase 3 ADAPT SERON study (NCT06298552) and the phase 3 ADAPT-SC study (NCT04735432), respectively, supported these applications.

A Disease That Hides in Plain Sight

Approximately 80% of patients have detectable antibodies against AChR, making diagnosis relatively straightforward, but the path to answers for the remaining patients has been far longer and harder.¹

“MG leads to debilitating muscle weakness, causing challenges with vision, movement, speech, swallowing, and even breathing,” James F. Howard Jr, MD, of The University of North Carolina at Chapel Hill School of Medicine, said in a statement. “Although many MG patients have detectable AChR-Ab, roughly 20% do not, making diagnosis and management especially difficult. The expanded indication of efgartigimod for use in all adult gMG patients enables health care providers to prescribe this targeted treatment more readily upon clinical diagnosis, irrespective of serotype.”

He added that this 20% of patients has historically been excluded from clinical trials.

What the ADAPT SERON Study Found

ADAPT SERON is the largest study to date of patients with gMG who do not have detectable anti-AChR antibodies, enrolling 119 adults across North America, Europe, China, and the Middle East. This randomized, double-blind, placebo-controlled investigation had 2 parts. In Part A, participants received 4 once-weekly intravenous (IV) infusions of efgartigimod or placebo, with the primary end point being improvement in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score at week 4; the follow-up was 5 weeks.

In Part B, the open-label period, there were two 4-week cycles of 4 once-weekly infusions, with 4 weeks in between each cycle; based on clinical status, beginning with cycle 3, additional treatment cycles were permitted and could be initiated at least 1 week after the final administration of the previous cycle.

The primary end point was met (P = .0068), with patients who received efgartigimod achieving a statistically significant improvement in MG-ADL total score vs placebo. Overall, across all serotypes in the study, there was a clinically meaningful 3.35-point improvement in the MG-ADL score at week 4, as well as clinically improved disease activity. Gains were also seen in Quantitative Myasthenia Gravis scores across subsequent treatment cycles. Efgartigimod was well tolerated, with a safety profile consistent with its established use in AChR-Ab–positive patients.^1-3

What Comes Next

Efgartigimod now has 3 treatment modalities: IV administration by a health care professional and subcutaneous injection by a health care provider or self.⁴ For an approval welcomed by researchers and patients alike, this label expansion is both a milestone and a tool to help streamline decision-making, according to Luc Truyen, MD, PhD, chief medical officer at argenx.¹

At present, the phase 3 ADAPT OCULUS study (NCT06558279) is evaluating the efficacy and safety of IV efgartigimod among patients with AChR-Ab seronegative gMG,⁵ and phase 2/3 ADAPT Jr study (NCT04833894) is evaluating the pharmacokinetics, pharmacodynamics, safety, and activity of efgartigimod in children aged 2 to younger than 18.⁶ Pediatric patients living with gMG currently have no approved treatments.

References

1. Argenx announces U.S. FDA approval expanding Vyvgart and Vyvgart Hytrulo for use in all adult patients living with gMG. News release. Argenx. May 8, 2026. Accessed May 11, 2026. https://argenx.com/news/2026/press-release-3291372
2. Argenx announces FDA acceptance of supplemental biologics license application with priority review for Vyvgart in AChR-Ab seronegative gMG. News release. Argenx. January 13, 2026. Accessed May 11, 2026. https://argenx.com/news/2026/press-release-3217457
3. Argenx announces U.S. FDA acceptance of biologics license application for subcutaneous efgartigimod in generalized myasthenia gravis with priority review. News release. Argenx. November 22, 2022. Accessed May 11, 2026. https://argenx.com/news/2022/argenx-announces-us-fda-acceptance-biologics-license-application-subcutaneous-efgartigimod
4. Vyvgart Hytrulo/Vyvgart. Prescribing information. Argenx; 2025. Accessed May 11, 2026. https://vyvgarthcp.com/gmg/dosing/overview
5. A study to assess efficacy and safety of efgartigimod PH20 SC in adults with ocular myasthenia gravis (ADAPT oculus). Clinicaltrials.gov. Updated December 12, 2025. Accessed May 11, 2026. https://clinicaltrials.gov/study/NCT06558279
6. Evaluating the pharmacokinetics, pharmacodynamics, and safety of efgartigimod administered intravenously in children with generalized myasthenia gravis (ADAPT Jr). Clinicaltrials.gov. Updated February 18, 2026. Accessed May 11, 2026. https://clinicaltrials.gov/study/NCT04833894