Efgartigimod (Vyvgart) was approved to treat generalized myasthenia gravis in adults who test positive for the anti-acetylcholine receptor (AChR) antibody, the Friday.
The decision is the first approval in a new class of drugs, the agency said. Efgartigimod is an antibody fragment that binds to the neonatal Fc receptor (FcRn), preventing FcRn from recycling immunoglobulin G (IgG) back into the blood. The medication causes a reduction in overall levels of IgG, including abnormal AChR antibodies present in myasthenia gravis.
"The approval of Vyvgart represents many achievements: our first approved product; the first-and-only FDA-approved neonatal Fc receptor blocker; and the first approved therapy designed to reduce pathogenic IgGs, an underlying driver of generalized myasthenia gravis," said Tim Van Hauwermeiren, CEO of drug developer Argenx, in a .
In the phase III trial of people with generalized myasthenia gravis and AChR antibody positivity, achieved at least a 2-point improvement in the Myasthenia Gravis-Activities of Daily Living score, compared with 30% of those receiving placebo (P<0.0001).
"About 84% of the patients who responded to treatment did so in the first 2 weeks of treatment," said researcher James Howard, MD, of the University of North Carolina School of Medicine in Chapel Hill, when he presented the findings at the 2021 American Academy of Neurology meeting.
The most common side effects associated with using efgartigimod were respiratory tract infections, headache, and urinary tract infection. Hypersensitivity reactions -- eyelid swelling, shortness of breath, and rash -- also occurred.
Risk of infections may increase because efgartigimod lowers IgG levels, the FDA cautioned.
"Patients using Vyvgart should monitor for signs and symptoms of infections during treatment," the agency noted. "Health care professionals should administer appropriate treatment and consider delaying administration of Vyvgart to patients with an active infection until the infection is resolved."