ARGX-113, an Investigational Therapy for Myasthenia Gravis, Shows Promise in Phase 2 Trial

An investigational treatment for myasthenia gravis, ARGX-113 (efgartigimod), being developed by the Dutch pharmaceutical firm argenx, was found to be well-tolerated and effective at improving disease symptoms as early as one week after the first infusion, trial data show.

The company recently revealed top-line data from its proof-of-concept Phase 2 trial of the compound, tested in myasthenia gravis patients with confirmed generalized muscle weakness.

Argenx plans to present complete study data at the American Academy of Neurology Annual Meeting in April 2018.

“There remains a clear unmet need for a safe and fast-acting treatment for patients with generalized MG, who continue to face serious, potentially life-threatening symptoms associated with their disease,” James F. Howard Jr., MD, Distinguished Professor of Neuromuscular Disease at the University of North Carolina School of Medicine, said in a press release.

The study (NCT02965573) included 24 patients who had generalized muscle weakness and symptoms not dominated by eye problems. Participants were randomly assigned to treatment with ARGX-113 or a placebo in addition to standard of care.

While safety and tolerability of the treatment were the study’s primary objective, researchers also evaluated ARGX-113’s effectiveness. Using four tools to measure the treatment’s impact on disease severity, it became clear that ARGX-113 improved scores on all four compared to placebo. Specifically, 75% of patients treated with the investigational therapy had clinically and statistically significant improvement through at least six weeks compared to 25% of patients on placebo.

Improvements already were seen after one week of the four weekly infusions. The treatment also lowered the levels of antibodies, a measure that correlated with patients’ disease severity.

Meanwhile, researchers reported that most adverse events were mild and unrelated to treatment. No severe adverse events were reported during the trial.

“These data demonstrate a rapid and sustained benefit in disease score after treatment with ARGX-113, supporting further development of the drug as a potential new option to fill the current treatment gap for MG patients,” said Howard, who also is a professor of neurology, medicine, and allied health and chief of the Neuromuscular Disorders Section at UNC’s School of Medicine.

“These results strengthen our conviction that reducing pathogenic autoantibodies may offer an innovative approach to treat myasthenia gravis and could give rise to potential therapeutic benefits in other neuromuscular conditions that are similarly mediated, said Nicolas Leupin, chief medical officer at argenx.

The company had earlier tested ARGX-113 in a Phase 1 trial in healthy volunteers and is currently exploring a subcutaneous version of the drug in another Phase 1 trial  (NCT03334084) in healthy volunteers.

In October, the U.S. Food and Drug Administration granted ARGX-113 orphan drug status for myasthenia gravis, a designation that intends to make it easier and less costly to develop therapies for rare diseases.