argenx SE announced that Japan's Ministry of Health, Labour and Welfare (MHLW) has approved VYVGART™ (efgartigimod alfa) intravenous infusion for the treatment of adult patients with generalized myasthenia gravis (gMG) who do not have sufficient response to steroids or non-steroidal immunosuppressive therapies (ISTs). VYVGART is the first-and-only neonatal Fc receptor (FcRn) blocker approved in Japan. Generalized myasthenia gravis is a rare and chronic neuromuscular disease characterized by debilitating and potentially life-threatening muscle weakness.

VYVGART is a human IgG1 antibody fragment that binds to FcRn, resulting in the reduction of circulating immunoglobulin G (IgG) autoantibodies. The action of IgG autoantibodies at the neuromuscular junction is a key driver of gMG. The ADAPT trial met its primary endpoint, demonstrating that significantly more anti-acetylcholine receptor (AChR) antibody positive gMG patients were responders on the myasthenia gravis activities of daily living (MG-ADL) scale following treatment with VYVGART compared with placebo (68% vs.

30%; p<0.0001). Responders were defined as having at least a two-point reduction on the MG-ADL scale sustained for four or more consecutive weeks during the first treatment cycle. There were also significantly more responders on the Quantitative Myasthenia Gravis (QMG) scale following treatment with VYVGART compared with placebo (63% vs.

14%; p<0.0001). Responders were defined as having at least a three-point reduction on the QMG scale sustained for four or more consecutive weeks during the first treatment cycle. VYVGART had a demonstrated safety profile in the ADAPT clinical trial.

The most common adverse events in ADAPT were respiratory tract infection (33% vs. 29% placebo), headache (32% vs. 29% placebo), and urinary tract infection (10% vs.

5% placebo). VYVGART was approved by the U.S. Food and Drug Administration (FDA) on December 17, 2021 for the treatment of gMG in adult patients who are AChR antibody positive. A Marketing Authorization Application for efgartigimod for the treatment of gMG is currently under review by the European Medicines Agency (EMA), with a decision anticipated in the second half of 2022.

argenx is evaluating efgartigimod in six high-need autoimmune conditions, set to expand to ten conditions by the end of 2022.