FDA Approves Inebilizumab for AChR- and MuSK-Positive Generalized Myasthenia Gravis

The FDA has approved inebilizumab (Uplizna; Amgen) for the treatment of generalized myasthenia gravis (gMG) in adults who are antiacetylcholine receptor (AChR) and antimuscle specific tyrosine kinase (MuSK) antibody positive, administered twice yearly after 2 initial loading doses. This marks the third FDA-approved indication for inebilizumab, which is also approved for antiaquaporin-4 antibody positive neuromyelitis optica spectrum disorder and immunoglobulin G4–related disease.¹

The approval of inebilizumab for gMG is supported by data from the phase 3 MINT trial (NCT04524273). In the trial, researchers 238 patients with gMG were randomly assigned 1:1 to either intravenous ineblizumab 300 mg (n = 119) or placebo (n = 119) for a 12-month period. Change from baseline in Myasthenia Gravis Activities of Daily Living (MD-ADL), the study’s primary end point, was statistically significant for inebilizumab-treated patients, with scores of –4.2 compared with –1.9 for those on placebo (P <.0001). The therapy showed a safe and well tolerated profile, consistent with prior safety findings.

"UPLIZNA showed strong efficacy at 26 weeks in both AChR+ and MuSK+ patients, with AChR+ patients continuing to improve through 52 weeks in MINT," global principal investigator Richard J. Nowak, MD, MS, director of the Myasthenia Gravis Clinic and associate professor of neurology at Yale School of Medicine, said in a statement.¹ "MINT also uniquely required steroid tapering, recognizing that long-term steroid use adds to the overall burden of disease. This approval brings a new first-in-class approach to gMG, expanding treatment options for clinicians and patients."

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The trial is considered the largest placebo-controlled study testing a biologic therapy in gMG. In addition to enrolling those with AChR-Ab+ positive gMG, the study included the most patients with MuSK-Ab+ (n = 48) gMG recorded in a therapeutic trial. Coming into the study, patients had an MG-ADL score of 6 or greater and a Quantitative Myasthenia Gravis (QMG) score of 11 or greater.

Results from the study showed that inebilizumab achieved clinically meaningful and statistically significant benefit in change in MG-ADL score for both AChR+ and MuSK+ cohorts. At week 26, investigators recorded statistically significant QMG score improvement with inebilizumab compared with placebo (inebilizumab: –4.8 overall improvement; placebo: –2.5; P = .0002). In terms of safety, the most common adverse reactions in patients treated with inebilizumab included headache and infusion-related reactions.

"Managing a rare and chronic illness can mean facing unpredictable relapsing symptoms and demanding treatment schedules," Samantha Masterson, president and chief executive officer at the Myasthenia Gravis Foundation of America, said in a statement.¹ "This approval marks an important milestone, offering durable efficacy and a dosing schedule that provides people living with generalized myasthenia gravis six months of treatment-free time between maintenance doses."

"This approval marks a significant advancement for people living with gMG," Jay Bradner, MD, executive vice president of Research and Development at Amgen, said in a statement.¹ "By selectively targeting CD19-positive B cells, UPLIZNA offers a new approach to treatment that addresses a biological root cause of disease. UPLIZNA is conveniently dosed twice a year and delivers durable efficacy, helping people manage debilitating symptoms that can compromise daily function – including trouble breathing, speaking and seeing."

New results from the phase 3 MINT trial, presented at the 2025 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) meeting, held October 29 to November 1, in San Francisco, California, revealed that inebilizumab selectively depleted B-cells and provided durable improvement through 52 weeks in patients with AChR+ gMG.³ In an interview with CGTLive^®, our sister publication, Nowak discussed the 52-week follow-up data presented at AANEM 2025 from the phase 3 MINT trial evaluating inebilizumab for gMG.

He noted that the results showed continued clinical improvement across MG-ADL and QMG scores. Nowak emphasized the treatment’s dual evidence for efficacy and safety, as well as its twice-yearly dosing schedule and associated corticosteroid taper. He also underscored the need for predictive biomarkers to better guide treatment response and disease progression in gMG. Additionally, he noted that ongoing open-label extension and biomarker studies are expected to provide additional insights into long-term outcomes and mechanisms of response.

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REFERENCES
1. FDA Approves UPLIZNA^® For Adults With Generalized Myasthenia Gravis. News release. Amgen. December 11, 2025. Accessed December 12, 2025. https://investors.amgen.com/news-releases/news-release-details/fda-approves-upliznar-adults-generalized-myasthenia-gravis
2. Amgen Conference Call to Discuss New Topline Data in Inflammation and Rare Disease. News release. Amgen. September 24, 2024. Accessed December 12, 2025. https://amgen2.rev.vbrick.com/#/videos/750c4b9d-5c91-4634-8906-a16b53f346bf.
3. Nowak RJ, Utsugisawa K, Benatar M, et al. Myasthenia Gravis Inebilizumab Trial (MINT): Efficacy, Pharmacodynamics, and Immunogenicity in AChR+ Cohort (Week 52). Presented at: 2025 AANEM; October 29 to November 1; San Francisco, California. Abstract 61. Accessed October 31, 2025. https://qrcodedochub.com/prd/index.html?content-id=776&doc-id=1021&action=view