argenx SE and Zai Lab Limited announced that China?s National Medical Products Administration (NMPA) approved the Biologics License Application (BLA) on July 16, 2024 for efgartigimod alfa injection (subcutaneous injection) (efgartigimod SC), 1,000mg (5.6ml)/vial indicated as an add on to standard therapy for the treatment of adult patients with generalized myasthenia gravis (gMG) who are anti-acetylcholine receptor (AChR) antibody positive. The BLA approval is supported by positive results from the global Phase 3 ADAPT-SC study, a bridging study to the Phase 3 ADAPT study, which formed the basis for approval of intravenous VYVGART in adult gMG patients. In the ADAPT-SC study, the primary endpoint of noninferiority was met (p< 0.0001), and efgartigimod SC demonstrated mean total IgG reduction of 66.4% from baseline at day 29, compared to 62.2% with efgartigimod IV.

Additional key secondary endpoints were also met, which were consistent with efficacy measures from the ADAPT study identifying the correlation between total IgG reduction and clinical benefit in gMG. The safety profile for efgartigimod SC was also consistent with the ADAPT study. Efgartigimod SC was generally well-tolerated; the most frequent adverse event being injection site reactions (ISRs), commonly observed with biologics administered subcutaneously.

All ISRs were mild to moderate and resolved over time. Efgartigimod SC is also being evaluated for the potential treatment of additional autoimmune disorders. In May 2024, the NMPA accepted a supplemental Biologics License Application (sBLA) with priority review for efgartigimod SC in chronic inflammatory demyelinating polyneuropathy (CIDP).

The U.S. Food and Drug Administration (FDA) approved efgartigimod SC in June 2024 for adults with CIDP. VYVGART (efgartigimod alfa injection) is a human IgG1 antibody fragment that binds to the neonatal Fc receptor (FcRn), resulting in the reduction of circulating IgG autoantibodies. It is the first approved FcRn blocker for the treatment of adults with generalized myasthenia gravis (gMG) who are anti-AChR antibody positive.

Efgartigimod SC is a subcutaneous product including efgartigimod alfa injection, a human IgG1 antibody fragment, and recombinant human hyaluronidase PH20 (rHuPH20), Halozyme?s ENHANZE® drug delivery technology to facilitate subcutaneous delivery of biologics. The product is to be administered subcutaneously as a single injection (1,000 mg fixed dose) over 30-to-90 seconds in cycles of once weekly injections for four weeks. Efgartigimod SC is approved in the United States (marketed as VYVGART® Hytrulo), EU (marketed as VYVGART® SC) and Japan (marketed as VYVDURA®).

Efgartigimod has the potential to address a multitude of severe autoimmune diseases where pathogenic IgGs are believed to be mediators of disease and is being evaluated in several autoimmune indications. Zai Lab has an exclusive license agreement with argenx to develop and commercialize efgartigimod in mainland China, Hong Kong, Macau, and Taiwan (collectively, Greater China). Myasthenia gravis (MG) is a chronic autoimmune disease, characterized by debilitating and potentially life-threatening muscle weakness.

There are approximately 170,000 people in China living with gMG1, and of those patients, 85% are estimated to have confirmed AChR antibodies; in this generalized form of the disease, skeletal muscles throughout the body may be affected, resulting in weakness and early fatigue. Difficulties with double vision, facial expression, speech, swallowing, and ambulation are frequent and difficult to manage for patients and treating physicians. In more life-threatening cases, gMG can affect the muscles responsible for breathing, which can be fatal.

Acetylcholinesterase (AChE) inhibitors, steroids, immunosuppressants, and IVIg are the mainstay of treatment in China. These drugs often achieve only partial restoration of strength.