FDA Approval Sought for Under-the-skin Efgartigimod for gMG

Developer Argenx aims to offer patients dosing, administration options

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Argenx has submitted an application to the U.S. Food and Drug Administration (FDA) requesting the approval of subcutaneous efgartigimod — an under-the-skin formulation of the active agent in Vyvgart — for the treatment of generalized myasthenia gravis (gMG).

FDA approval would provide gMG patients with an additional delivery option for efgartigimod, now given, as Vyvgart, as an intravenous (into-the-blood) infusion, according to Argenx.

“Our vision for the gMG program is to deliver the broadest treatment offering for people living with this debilitating, and often overlooked disease. Every individual experiences gMG differently, which is why we’re excited about the possibility of introducing multiple ways to meet the needs of patients, including with route of administration and dosing schedule,” Tim Van Hauwermeiren, CEO of Argenx, said in a press release.

“The submission of this BLA [biologics license application] is the latest milestone in honoring our commitment to the gMG patient community. We look forward to working closely with the agency through the BLA review process and to potentially bringing forth another first-in-class option for gMG patients,” Van Hauwermeiren said.

MG is caused by self-reactive antibodies that interfere with the communication between nerve and muscle cells. Efgartigimod is designed to lower the levels of disease-driving antibodies by blocking a protein that normally helps stabilize antibodies circulating in the bloodstream and prevent their degradation.

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Efgartigimod as Injection Similar to Vyvgart in Treating gMG, Trial Finds

Vyvgart is an FDA-approved formulation of efgartigimod that is administered via hour-long infusions into the bloodstream. In addition to the U.S., Vyvgart is approved to treat gMG in Europe and Japan. It also is under review in China for the same indication.

Testing subcutaneous efgartigimod

The subcutaneous or under-the-skin formulation of efgartigimod was created using a drug delivery technology developed by Halozyme Therapeutics. That technology facilitates the delivery of biologic therapies that are typically administered by infusion directly into the bloodstream.

Argenx’s application is supported by data from a Phase 3 trial called ADAPT-SC (NCT04735432). The study enrolled 110 adults with gMG at sites in North America, Europe, and Japan. Participants were randomly assigned to receive either 1,000 mg subcutaneous efgartigimod or 10 mg/kg Vyvgart, given once per week for four weeks.

Results showed that the reduction in IgG, a type of antibody implicated in gMG, was similar in both groups after 29 days of treatment. Specifically, the reduction was 66.4% with subcutaneous efgartigimod and 62.2% with Vyvgart.

Notably, the effect was similar regardless of whether or not patients were positive for anti-AChR, the most common type of MG-driving antibody.

Safety data also were comparable between the two formulations. The most common side effects associated with subcutaneous efgartigimod were injection site reactions, all of which were mild or moderate in severity and resolved with time.

More than two-thirds (69.1%) of patients on subcutaneous efgartigimod experienced a clinically significant improvement of at least two points on the Myasthenia Gravis Activities of Daily Living (MG-ADL) score, a measure of MG’s impact on daily life. That improvement lasted for at least four consecutive weeks. A similar proportion (65.5%) improved by at least three points on the Quantitative Myasthenia Gravis (QMG) score, a measure of disease severity, for four consecutive weeks.

Just over one in three patients (37%) on subcutaneous efgartigimod were symptom-free by the trial’s end.

Nearly all trial participants (95%) have now entered into an open-label extension study, called ADAPT-SC+ trial (NCT04818671), that will span an additional two years. All patients will now be treated with subcutaneous efgartigimod and monitored for safety and efficacy outcomes.