FDA Reviewing Efgartigimod as Possible Treatment for Generalized MG

The U.S. Food and Drug Administration (FDA) is now reviewing an application from Argenx that seeks approval of efgartigimod (ARGX-113) to treat people with generalized myasthenia gravis (gMG).

An agency decision is expected on or before Dec. 17.

“This is an important milestone for argenx in our transition to a commercial-stage company and brings us closer to our mission to reach patients living with gMG, a debilitating neuromuscular disease,” Tim Van Hauwermeiren, CEO of Argenx, said in a press release. “We look forward to closely collaborating with the FDA through the [application] review process and to potentially making our first medicine available.”

Argenx also announced the opening of an early access program in the U.S., allowing eligible gMG patients to be treated with efgartigimod prior to the FDA’s decision. These programs make investigational treatments available to people with a high degree of unmet clinical need but unable to participate in a clinical trial.

More information on the access program is available on this webpage, the company reported.

The company added that remains on track to file an application for efgartigimod’s approval  to treat gMG in Japan by June. A similar request to the European Medicines Agency is expected in the second half of this year.

Efgartigimod works by blocking the activity of neonatal Fc receptor (FcRn), a protein that normally helps to protect certain antibodies from being broken down. MG is caused by an antibody-driven immune response that damages healthy muscle cells; by blocking FcRn, efgartigimod is designed to lower levels of disease-driving antibodies in the body.

Its application is supported by data from the Phase 3 ADAPT clinical trial (NCT03669588). This Argenx-sponsored study enrolled 167 adults with gMG, of whom 129 were positive for antibodies against acetylcholine receptor (AChR), which are the most common cause of gMG.

Trial results demonstrated that treatment with efgartigimod led to significant and early reductions in disease severity. For example, among participants with anti-AChR antibodies, significantly more patients given efgartigimod than a placebo experienced a two-point improvement in the Myasthenia Gravis Activities of Daily Living, with gains lasting at least four weeks (67.7% vs. 29.7%). Such improvements were the study’s main measure of efficacy.

Similar results were found regardless of the presence of AChR antibodies, and efgartigimod was seen to be well-tolerated — safety data were similar among participants on the investigational therapy or a placebo.

About 90% of people who completed the ADAPT trial elected to enroll in ADAPT+ (NCT03770403), a three-year extension study assessing efgartigimod’s long-term safety and tolerability. Currently, 118 people are enrolled in ADAPT+, according to Argenx; all are being treated with efgartigimod in this open-label extension.

Should the FDA favor approval, efgartigimod would be the first FcRn blocker available in the U.S., Argenx said in its release.