New data from the Phase 2/3 VIBRANCE-MG study indicates that nipocalimab, an investigational agent by Johnson & Johnson, is both safe and efficacious in treating adolescents with generalized myasthenia gravis (gMG). The study, presented at the 2024 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) meeting, addresses a critical gap in treatment options for this patient population, which constitutes approximately 10% of new gMG cases and has historically been excluded from drug trials.
The VIBRANCE-MG study included seven adolescents aged 12-18 with seropositive gMG. Led by Jonathan Strober, MD, the study administered nipocalimab as a 30 mg/kg intravenous (IV) loading dose, followed by 15 mg/kg IV every two weeks. Five patients completed the 24-week treatment period. The primary endpoint was the change in total serum immunoglobulin G (IgG) levels.
Significant Reduction in IgG Levels
The study demonstrated a statistically significant reduction in total serum IgG levels at week 24. The mean percent change from baseline to week 24 for total serum IgG was -68.98% (SD, 7.561). According to Dr. Strober, the focus on IgG levels as the primary endpoint was driven by safety considerations in this smaller population, ensuring the drug performs as expected in adolescents, similar to its effects in adults.
Improvements in Clinical Outcomes
At baseline, the mean scores on Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) were 4.29 (SD, 2.430) and 12.50 (SD, 3.708), respectively. After 24 weeks of nipocalimab treatment, the mean change in MG-ADL was -2.40 (SD, 0.418), and the mean change in QMG was -3.80 (SD, 2.683). Notably, four of the five patients who completed the study achieved minimal symptom expression, defined as MG-ADL scores of 0-1.
While the improvements in MG-ADL and QMG scores were not as pronounced as those observed in adult populations, Dr. Strober noted that the smaller sample size and the relatively better baseline condition of the adolescent patients might account for this difference. "Almost all the kids in the study had very low functional abnormalities at the end of the initial period that we evaluated them," he stated.
Favorable Safety Profile
Nipocalimab was well-tolerated among the adolescent participants, with no serious adverse events reported and no discontinuations due to adverse events. The safety profile was consistent with expectations, with the most frequent adverse event being nasopharyngitis, followed by COVID-19, which was deemed unrelated to the study drug. Patients who contracted COVID-19 during the trial did not experience significant adverse events while on nipocalimab.
Mechanism of Action and Regulatory Context
Nipocalimab is designed to selectively block the binding of IgG to the neonatal fragment crystallizable (Fc) receptor, leading to reduced levels of circulating IgG, including IgG autoantibodies. Johnson & Johnson submitted a biologics license application for nipocalimab for the treatment of adults with gMG, supported by data from the Phase 3 Vivacity-MG study, which demonstrated the superiority of nipocalimab plus standard of care over placebo plus standard of care in improving MG-ADL scores over a 24-week period.
