Vyvgart may fill gap in medications for juvenile MG: Real-world study

Vyvgart (efgartigimod alfa-fcab) may be a safe and effective treatment for children and adolescents with juvenile myasthenia gravis (JMG), according to new real-world data from China.

The study found that the therapy, developed by Argenx and currently approved for certain adults with generalized myasthenia gravis (gMG), drastically reduced symptom severity and improved daily life for pediatric patients, with the majority experiencing either mild or no symptoms within one month.

The multicenter study highlights Vyvgart’s potential to fill a critical gap in pediatric care, where treatment options are currently limited. Researchers observed “clinically meaningful” improvements in more than 90% of participants, including those with severe disease and those whose cases had previously resisted standard treatments.

While larger clinical trials are still ongoing to confirm these findings, this real-world evidence suggests that Vyvgart can rapidly stabilize JMG and provide a “robust intervention” for even the most complex pediatric cases.

“Our study suggests [Vyvgart] is an effective therapeutic option for JMG, with favorable efficacy and safety profiles,” researchers wrote.

The real-world study, “Experience Using Efgartigimod to Treat Juvenile Myasthenia Gravis in China: A Multicenter Retrospective Study,” was published in Muscle & Nerve.

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Addressing the shortage of pediatric treatments

Myasthenia gravis (MG) is an autoimmune disease usually caused by self-reactive antibodies targeting proteins involved in nerve-muscle communication, more commonly acetylcholine receptors (AChRs). JMG is a rare disease type that affects children and adolescents younger than 18 years.

Currently, Vyvgart is being tested in children and adolescents with juvenile gMG in two separate Phase/2 clinical trials, ADAPT Jr (NCT04833894) and ADAPT Jr SC (NCT06392386), and an open-label extension study, ADAPT Jr+ (NCT05374590). So far, data show that the therapy safely reduced disease severity in adolescent participants.

Vyvgart, given via weekly intravenous infusions in four-week cycles, is approved in the U.S., Europe, and China for adults with gMG who are positive for anti-AChR antibodies. The therapy works by blocking FcRn, a protein that normally helps prevent the breakdown of antibodies circulating in the bloodstream. It is therefore expected to increase the rate at which antibodies, including those driving MG, are broken down, ultimately easing disease symptoms.

To assess Vyvgart’s safety and efficacy in JMG patients in a real-world setting, a team of researchers retrospectively analyzed data from 17 children and adolescents who received the therapy, along with standard immunosuppressive treatments, at 12 centers in China.

Participants were mainly girls (82.4%) and had been living with the disease for a median of nearly two years. Their mean age was 8.59 years at disease onset and 13.4 years before starting Vyvgart (baseline).

At disease onset, more than half had ocular MG, where only the eye muscles are affected, and most progressed to generalized MG. All but one started Vyvgart due to sudden symptom worsening or insufficient response to previous treatments, including pyridostigmine (sold as Mestinon, with generics available) and several immunomodulatory drugs.

Following the first Vyvgart dose, 70.6% of the participants experienced a clinically meaningful improvement (CMI), and this proportion rose to 91.7% after a month. CMI was defined as a reduction of at least two points in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score, which assesses the disease’s impact on activities of daily living.

More than half (66.7%) of patients had “minimal symptom expression” one month after starting treatment, meaning they had an MG-ADL score of zero or one. Consistent symptom reduction was also reflected in progressive score declines in the Quantitative MG (QMG) test, which measures muscle weakness. After four weeks, MG-ADL scores had decreased by 87.6% and QMG scores by 71.8%.

“Six patients did not complete one cycle of treatment due to symptom relief and economic considerations,” the researchers wrote, adding that all “demonstrated clinical improvement after one or two treatments, leading to discontinuation of [Vyvgart] therapy.”

Success in treatment-resistant and complex cases

Treatment efficacy was consistent regardless of symptoms at disease onset, disease duration, or prior treatment resistance. All 11 participants with treatment-resistant disease before Vyvgart achieved significant reductions in MG-ADL scores after four weeks, and half attained minimal symptom expression.

Vyvgart was also effective in participants without self-reactive antibodies and provided rapid stabilization for those in myasthenic crisis, when respiratory muscle weakness causes severe breathing problems that may require hospitalization.

No patient reported treatment-related allergic reactions, infections, or serious adverse events during the treatment or follow-up. This favorable safety profile is a key finding for a population that often relies on long-term immunosuppressants with significant side effects.

“In conclusion, [Vyvgart] has a favorable safety profile and potential clinical efficacy in patients with JMG, including those with [treatment-resistant] disease,” the team wrote. Data from the ongoing Vyvgart trials in children and adolescents will help to further confirm these results for global regulatory approvals.