Inebilizumab Shows Durable Benefit in MuSK+ Generalized Myasthenia Gravis at AANEM 2026

New analyses from the phase 3 MINT trial of inebilizumab (Uplizna; Amgen) in generalized myasthenia gravis (gMG) showed that clinical improvements in the anti-muscle-specific kinase antibody-positive (MuSK+) subgroup continued through 52 weeks, and that treatment benefit did not appear to depend on how long patients had been living with the disease. Amgen presented both analyses at the 2026 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting and MGFA Scientific Session, held this week in Orlando, Florida.^1,2

MuSK+ subgroup results through 52 weeks

MINT (NCT04524273) randomized 48 participants with MuSK+ gMG 1:1 to 300-mg intravenous inebilizumab or placebo for a 26-week randomized controlled period, during which patients underwent a protocol-specified steroid taper to 5 mg/day or less by week 24. Of those participants, 46 entered a subsequent 26-week open-label period in which all received inebilizumab, and 44 completed it; baseline Myasthenia Gravis-Activites of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores were similar between the original randomized groups.^1,3

During the randomized period, mean MG-ADL and QMG scores decreased from baseline by week 26 in both groups, though more with inebilizumab (-4.1 and -5.0, respectively) than placebo (-3.1 and -4.2). By week 52, after 26 weeks of open-label inebilizumab, scores continued to decrease from baseline regardless of initial assignment: -5.6 on MG-ADL and -6.1 on QMG for patients who received inebilizumab throughout, and -5.1 and -7.4, respectively, for patients who switched from placebo to inebilizumab. Amgen described this as a descriptive, interim analysis, and no statistical testing was performed on these comparisons.

“In this descriptive analysis, inebilizumab demonstrated ongoing improvement in MG-ADL and QMG scores compared to baseline irrespective of initial randomization,” concluded Richard Nowak, MD, MS, global principal investigator of MINT and director of the Yale Myasthenia Gravis Clinic at Yale University, and colleagues.¹

Efficacy independent of time since diagnosis

A separate post hoc analysis examined whether inebilizumab's effect varied by time since gMG diagnosis, grouping the trial's 238 participants (190 AChR-antibody-positive [AChR+], 48 MuSK+) into those diagnosed less than 1 year, 1 to less than 4 years, or 4 or more years before their first dose. At week 26, the least-squares mean change from baseline in MG-ADL score was numerically greater with inebilizumab than placebo across all 3 subgroups (less than 1 year, -5.4 vs -3.0; 1 to less than 4 years, -4.3 vs -1.8; 4 or more years, -3.7 vs -2.5).²

The change in QMG score followed the same pattern (less than 1 year, -5.2 vs -4.0; 1 to less than 4 years, -6.4 vs -2.2; 4 or more years, -4.0 vs -1.9).

Among AChR+ participants followed to week 52, the pattern held: MG-ADL improved by -5.7 versus -2.3 in patients diagnosed less than 1 year earlier, -5.0 versus -2.7 for 1 to less than 4 years, and -4.0 versus -1.5 for 4 or more years, with a similar advantage for inebilizumab on QMG scores across all 3 groups. No formal statistical comparisons between subgroups were reported.

“Inebilizumab's efficacy appears independent of time since diagnosis, although the small size of subgroups limits firm conclusions,” Ali A. Habib, MD, associate professor of neurology at the University of California, Irvine School of Medicine, and colleagues wrote.²

From pivotal trial to clinical use

The FDA approved inebilizumab in December 2025 for AChR+ and MuSK+ gMG based on MINT's primary 26-week results, in which the drug reduced MG-ADL score by 4.2 points versus 2.2 with placebo (P <.0001) and QMG score by 4.8 points versus 2.3 (P =.0002); it is dosed as 2 initial loading doses followed by a single maintenance infusion every 6 months.³

A prespecified analysis published in August 2026 in JAMA Neurology found that inebilizumab also reduced exacerbations and rescue therapy use through week 26, with exacerbations occurring in 16% of inebilizumab-treated patients versus 35% on placebo (hazard ratio, 0.41; P =.001) and rescue therapy required by 8.4% versus 23.9% (hazard ratio, 0.34; P =.003).⁴

Click here for more AANEM 2026 coverage.

REFERENCES
1. Nowak R, Leite MI, Benatar M, Ciafaloni E, Vissing J, Utsugisawa K, Bray S, Bhambri A, Kanchi AK, Cheng S, Howard JF Jr. Myasthenia gravis inebilizumab trial: 26-week randomized placebo-controlled and 26-week open-label results in anti-muscle-specific kinase subgroup. Presented at: 2026 AANEM Annual Meeting and MGFA Scientific Session; September 29-October 2, 2026; Orlando, FL.
2. Habib A, Howard JF Jr, Benatar M, Ciafaloni E, Leite MI, Utsugisawa K, Vissing J, Bray S, Schlader-Ratzinger M, Najem C, Cheng S, Nowak R. Impact of time since diagnosis on efficacy of inebilizumab: post hoc analysis of phase 3 Myasthenia Gravis Inebilizumab Trial data. Presented at: 2026 AANEM Annual Meeting and MGFA Scientific Session; September 29-October 2, 2026; Orlando, FL.
3 FDA approves Uplizna for adults with generalized myasthenia gravis. News release. Published December 11, 2025. Accessed September 28, 2026. https://www.amgen.com/newsroom/press-releases/2025/12/fda-approves-uplizna-for-adults-with-generalized-myasthenia-gravis
4. Nowak RJ, Habib AA, Howard JF Jr, et al. Management of exacerbations and rescue therapy in the phase 3 myasthenia gravis inebilizumab trial: a prespecified analysis of a randomized clinical trial. JAMA Neurol. Published online August 10, 2026. doi:10.1001/jamaneurol.2026.2558