FDA Approves UPLIZNA as First CD19-Targeted B Cell Therapy for Generalized Myasthenia Gravis
Key Insights
The FDA has approved UPLIZNA (inebilizumab-cdon) for treating generalized myasthenia gravis (search) in adults with anti-AChR (search) or anti-MuSK (search) antibodies, marking the first CD19 (search)-targeted B cell therapy for this indication.
In the Phase 3 MINT trial, UPLIZNA demonstrated significant symptom improvement with a 1.9-point difference in MG-ADL scores compared to placebo at 26 weeks (p<0.0001).
The therapy offers convenient twice-yearly dosing after initial loading doses and allows for steroid tapering, with 87.4% of patients reducing steroid doses to 5 mg or less daily.
The U.S. Food and Drug Administration has approved UPLIZNA (inebilizumab-cdon) for the treatment of generalized myasthenia gravis (search) (gMG) in adults who are anti-acetylcholine receptor (search) (AChR (search)) and anti-muscle specific tyrosine kinase (search) (MuSK (search)) antibody positive. This approval establishes UPLIZNA as the first and only CD19 (search)-targeted B cell therapy approved for this rare autoimmune disorder, offering patients a new targeted treatment approach with twice-yearly dosing after initial loading doses.
Landmark Phase 3 Trial Results Drive Approval
The FDA approval is supported by data from the Myasthenia Gravis (search) Inebilizumab Trial (MINT), a randomized, double-blind, placebo-controlled study that enrolled 238 adults with gMG, including 190 AChR (search)-positive and 48 MuSK (search)-positive patients. MINT represents the largest Phase 3 biologic study to include both patient populations and the first to successfully incorporate a steroid taper protocol.
At the primary endpoint of 26 weeks, UPLIZNA demonstrated a statistically significant 1.9-point difference in the Myasthenia Gravis (search) Activities of Daily Living (MG-ADL) score compared with placebo (-4.2 vs. -2.2; p<0.0001). The MG-ADL scale assesses the impact of gMG on daily functions across 8 signs or symptoms, with scores ranging from 0 to 24 and higher scores indicating greater impairment.
"UPLIZNA showed strong efficacy at 26 weeks in both AChR (search)+ and MuSK (search)+ patients, with AChR+ patients continuing to improve through 52 weeks in MINT," said Richard J. Nowak, M.D., M.S., global principal investigator and director of the Myasthenia Gravis (search) Clinic at Yale University.
Sustained Benefits and Steroid Reduction
The trial's key secondary endpoints further demonstrated UPLIZNA's efficacy across multiple measures. For the combined study population, UPLIZNA showed a 2.5-point difference in the Quantitative Myasthenia Gravis (search) (QMG) score compared to placebo (-4.8 vs. -2.3; p=0.0002) at Week 26. The QMG is a 13-item system that quantitatively measures disease impairment by assessing muscle weakness, with scores ranging from 0 to 39.
In the AChR (search)-positive subgroup, which comprises approximately 85% of myasthenia gravis (search) patients, benefits continued through Week 52 - the longest randomized-controlled period for a Phase 3 trial in gMG. An exploratory analysis showed a 2.8-point difference in MG-ADL scores for UPLIZNA compared with placebo (-4.7 vs. -1.9; 95% CI: -3.9 to -1.7) at Week 52.
MINT uniquely required steroid tapering, with patients beginning to reduce doses at Week 4 to reach prednisone 5 mg per day by Week 24. By Week 26, 87.4% of UPLIZNA patients and 84.6% of those taking placebo had successfully reduced their steroid dose to 5 mg or less per day, addressing the significant burden of long-term steroid use in gMG management.
Addressing Unmet Medical Need
Generalized myasthenia gravis (search) is a rare, unpredictable, chronic, B-cell-mediated autoimmune disorder that impairs neuromuscular communication and can cause fluctuating muscle weakness, trouble breathing, difficulty swallowing, and impaired speech and vision. The disease affects between 80,000 and 100,000 patients in the U.S., with approximately 85% having the generalized form.
"By selectively targeting CD19 (search)-positive B cells, UPLIZNA offers a new approach to treatment that addresses a biological root cause of disease," said Jay Bradner, M.D., executive vice president of Research and Development at Amgen. "UPLIZNA is conveniently dosed twice a year and delivers durable efficacy, helping people manage debilitating symptoms that can compromise daily function."
The disease is thought to be primarily driven by AChR (search) and MuSK (search) autoantibodies produced by CD19 (search)+ B cells, particularly plasmablasts and some plasma cells. These antibodies target and disrupt critical proteins in the neuromuscular junction. UPLIZNA is a humanized monoclonal antibody that causes targeted and sustained depletion of these autoantibody-producing CD19+ B cells.
Safety Profile and Patient Impact
The most common adverse reactions in gMG patients were headache and infusion-related reactions. Infusion reactions were observed in 10.1% of patients treated with UPLIZNA during the randomized controlled period, most commonly with the first infusion but also during subsequent infusions.
"Managing a rare and chronic illness can mean facing unpredictable relapsing symptoms and demanding treatment schedules," said Samantha Masterson, president and chief executive officer of the Myasthenia Gravis Foundation of America (search). "This approval marks an important milestone, offering durable efficacy and a dosing schedule that provides people living with generalized myasthenia gravis (search) six months of treatment-free time between maintenance doses."
Expanding Treatment Portfolio
This approval represents the third indication for UPLIZNA, which was previously approved by the FDA for treating adult patients with anti-aquaporin-4 (search) (AQP4 (search)) antibody positive neuromyelitis optica spectrum disorder (search) (NMOSD) in June 2020, and for treating adult patients with Immunoglobulin G4-related disease (search) (IgG4-RD) in April 2025.
The global prevalence of myasthenia gravis (search) is estimated at 2-36 cases per 100,000, with the disease more frequently seen in young women (age 20-30) and men aged 50 years and older. The prevalence and incidence of gMG are increasing worldwide, highlighting the importance of new therapeutic options for this challenging condition.