Global Phase 3 MG Trial of argenx’s Efgartigimod on Track Following FDA Meeting

The clinical-stage biotech company argenx is planning to start a pivotal Phase 3 trial of efgartigimod (ARGX-113) for generalized myasthenia gravis (gMG) before the end of the year.

The company announced it has received guidance from the U.S. Food and Drug Administration following an End-of-Phase 2 meeting.

The Phase 3 program is expected to support an FDA biologics license application to commercialize the investigative therapy.

argenx expects to enroll 150 patients with generalized MG in a placebo-controlled trial that should last 26 weeks. Patients will then be eligible to participate in a one-year extension study.

The trial will include myasthenia gravis patients with or without antibodies to the postsynaptic nicotinic acetylcholine receptor, a protein that plays a role in nerve-to-muscle signaling.

Most cases of gMG involve an antibody called IgG that interferes with these receptors. They are thought to cause the defect in the transmission of signals from nerves to muscles seen in the disease.

Efgartigimod is an antibody fragment designed for the treatment of patients with severe autoimmune diseases, including myasthenia gravis, that are characterized by high levels of harmful antibodies. It was engineered to degrade circulating disease-causing autoimmune antibodies by blocking them from binding to cells.

Normally, antibodies bind to a receptor called FcRn on the surface of cells. Efgartigimod binds FcRn receptors better than naturally occurring antibodies, preventing harmful antibodies from being attached to cells.

The therapy candidate has received orphan drug status in both Europe and the United States.

In December 2017, the company announced key results of a Phase 2 clinical trial  (NCT02965573) of efgartigimod in 24 MG patients with muscle weakness. Efgartigimod in addition to standard of care improved patients’ symptoms as early as one week after the first intravenous infusion, and the treatment was well tolerated.

After six weeks, efgartigimod was found to be beneficial in 75 percent of the patients, compared to 25 percent of patients on placebo.

“The outcome of the End-of-Phase 2 meeting is an important step in our strategic plan to advance efgartigimod in gMG patients. We plan to proceed with one study and one dose for our path to approval, and to include AChR autoantibody-negative patients in our recruitment plan as this subset represents a particular high unmet need among the MG population,” Nicolas Leupin, chief medical officer of argenx, said in a press release.

“We believe our Phase 3 clinical trial, in combination with the positive Phase 2 data, has the potential to support a BLA submission,” he added. “We will continue to work very closely with the regulatory authorities as we advance efgartigimod towards approval to help patients suffering from this severe autoimmune disease.”

argenx is developing a pipeline of antibody-based therapies for the treatment of severe autoimmune diseases and cancer, especially in cases where there are no effective treatments.