The investigational monoclonal antibody batoclimab led to significant improvement in activities of daily living in people with generalized myasthenia gravis (gMG), a multicenter phase III trial found.
The rate of sustained improvement on Myasthenia Gravis Activities of Daily Living (MG-ADL) scores for antibody-positive patients in the first treatment cycle was 58.2% in the batoclimab group and 31.3% in the placebo group (OR 3.45, 95% CI 1.62-7.35, P=0.001), reported Chongbo Zhao, MD, of Fudan University in Shanghai, China, and colleagues.
The MG-ADL score diverged between the two groups as early as week 2, the researchers wrote in JAMA Neurology. The mean maximum difference in MG-ADL score reduction occurred 1 week after the last dose.
Batoclimab is a neonatal fragment crystallizable receptor (FcRn) antagonist. Two other FcRn blockers — efgartigimod (Vyvgart) and rozanolixizumab (Rystiggo) — recently were approved for gMG.
“The publication of this study provides more potential treatment options for patients with gMG, further driving a profound transformation in the treatment landscape of gMG, accelerating the evolution of MG treatment towards the era of evidence-based medicine, and demonstrating the robustness of FcRn antagonists in treating MG,” Zhao told MedPage Today in an email.
Myasthenia gravis is a rare autoimmune disorder caused by autoantibodies that disrupt the neuromuscular junction. Treatments that reduce immunoglobulin G (IgG) levels in circulation, such as plasma exchange and high-dose IV immunoglobulin and immunoadsorption, are used for symptom relief.
FcRn inhibitors like batoclimab, efgartigimod, or rozanolixizumab increase the half-life of IgG to reduce its concentration. “In terms of treating gMG, these three FcRn antagonists show similarities in rapid onset of action, significant symptom improvement, and minimal adverse reactions, indicating good robustness in gMG treatment,” Zhao said.
The trial included adult gMG patients from 27 centers in China. Study participants were positive for acetylcholine receptor (AChR) or muscle-specific kinase (MuSK) antibodies.
Eligible patients had MG-ADL scores of 5 or greater (on a scale of 0 to 24, with higher scores representing greater symptom severity), among other criteria. Patients who had thymectomy within 3 months of screening or needed one during the trial and those on certain therapies were excluded.
Participants were randomized to receive either batoclimab or placebo. One treatment cycle included six injections of 680 mg of batoclimab or placebo weekly, followed by 4 weeks of observation without treatment. A second treatment cycle was started in patients who required continuing treatment. Eight of 67 participants (11.9%) in the batoclimab group did not receive cycle 2 treatment.
The primary outcome was sustained MG-ADL improvement, defined as a reduction of 3 or more points from baseline for at least 4 consecutive weeks, in the first cycle. Follow-up was until week 24 or 5 weeks after the last dose, whichever was later. All patients also received standard of care.
Overall, 131 gMG patients were included in the study. Their mean age was about 47, and 67.2% were women.
Treatment-related or severe treatment-emergent adverse events emerged in 70.1% and 3%, respectively, of the batoclimab group and 36.9% and 7.7% of the placebo group. The most common adverse events in the batoclimab group were peripheral edema in 38.8%, upper respiratory tract infection in 35.8%, and urinary tract infection in 19.4%.
Subgroup analyses also showed symptom relief and quality of life improvement, as assessed by MG-ADL scores of 0 or 1 or sustained Quantitative Myasthenia Gravis score reductions.
The authors acknowledged that the trial included only two treatment cycles, and its design did not allow for long-term safety data on infections and cardiovascular events to be collected.
“An open-label extension trial is currently ongoing to monitor long-term safety,” Zhao and colleagues noted.
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Disclosures
Funding for this trial came from Nona Biosciences (Suzhou), a subsidiary of Harbour Biomed Inc.
Zhao reported financial relationships with Nona Biosciences, Roche, Sanofi, and Zailab. Several co-authors reported being employees of Nona Biosciences (Suzhou).
Primary Source
JAMA Neurology
Source Reference: Yan C, et al “Batoclimab vs placebo for generalized myasthenia gravis” JAMA Neurol 2024; DOI: 10.1001/jamaneurol.2024.0044.
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