Antibodies are proteins that the immune system produces in response to foreign molecules invading the body. They fall into five classes (IgG, IgA, IgM, IgD, and IgE) where each class acts slightly differently and responds to different threats. Most antibodies in the blood and fluid that surround tissues and cells belong to the IgG class. The antibodies that contribute to MG development and progression also belong to the IgG class.
These IgC antibodies target a protein called the acetylcholine receptor, which binds to the neurotransmitter acetylcholine and plays a key role in nerve-muscle communication. Normally, the binding of acetylcholine to its receptor signals muscles to contract. However, because the immune system attacks acetylcholine receptors in MG, acetylcholine cannot bind to them efficiently and nerve cells cannot send a strong signal to muscles, resulting in muscle weakness.
Normally, IgG antibodies circulating in the bloodstream are eventually broken down and recycled. A protein called neonatal Fc receptor (FcRn) helps to stabilize IgG antibodies and prevent this process. Vyvgart works by blocking this receptor, thereby increasing the rate at which IgG antibodies, including those driving MG, are broken down. By lowering the levels of disease-driving antibodies, the therapy is expected to ease MG symptoms.
Vyvgart is administered via hour-long infusions into the bloodstream. Patients initially receive four weekly infusions over the course of four weeks, with additional treatment cycles administered based on clinical response.
The treatment is currently being reviewed by NICE. MDUK took part in a NICE scoping appraisal in April 2022, ahead of which we liaised with specialist neuromuscular clinicians. We are awaiting next steps and aim to work in partnership with people with myasthenia gravis to submit the patient voice as part of any future consultation/appraisal.
Vyvgart is available through an Early Access to Medicines Scheme (EAMS). For more information on the scheme, please read through our FAQ for vyvgart (efgartigimod alfa) in the treatment of myasthenia gravis (gMG) here.