Vyvgart is a prescription medication used to treat two autoimmune nerve and muscle conditions: generalized myasthenia gravis (gMG) and chronic inflammatory demyelinating polyneuropathy (CIDP). Both diseases are caused by the immune system producing harmful antibodies that attack the body’s own tissues, and Vyvgart works by lowering the levels of those antibodies in the bloodstream.
Generalized Myasthenia Gravis
Vyvgart’s first and most established use is for generalized myasthenia gravis, a condition where the immune system attacks the connection between nerves and muscles. This causes muscle weakness that can affect the eyes, face, throat, limbs, and in serious cases, breathing. Specifically, Vyvgart is approved for adults who test positive for acetylcholine receptor (AChR) antibodies, which are the harmful immune proteins driving the disease in the majority of gMG patients. Insurance coverage typically requires a positive blood test confirming these antibodies before approving treatment.
In clinical trials, Vyvgart produced meaningful improvements in daily functioning for most patients. Over 90% of AChR antibody-positive participants experienced a clinically significant improvement in their ability to perform everyday activities like chewing, talking, breathing, and gripping objects during the first 10 treatment cycles. That level of response held consistently across repeated cycles of treatment.
Chronic Inflammatory Demyelinating Polyneuropathy
Vyvgart’s subcutaneous form (Vyvgart Hytrulo) is also approved for CIDP, a condition where the immune system damages the protective coating around peripheral nerves. This leads to progressive weakness and numbness, usually in the legs and arms, that develops over weeks to months. CIDP is much rarer than myasthenia gravis, and treatment options have historically been limited.
The clinical trial for CIDP used a two-stage design. In the first stage, 66% of patients showed confirmed clinical improvement after up to 12 weeks of weekly treatment. Those responders then entered a second stage where they were randomly assigned to continue Vyvgart or switch to placebo. The results were striking: only 28% of patients who stayed on Vyvgart relapsed, compared to 54% of those on placebo. That translates to a 61% reduction in the risk of relapse.
How Vyvgart Works
In autoimmune diseases like gMG and CIDP, the immune system produces antibodies (a type called IgG) that mistakenly attack healthy tissue. Normally, a recycling protein in the body called FcRn protects IgG antibodies from being broken down, keeping them circulating in the blood for weeks. Vyvgart blocks this recycling protein. Without that protection, IgG antibodies, including the harmful ones causing disease, are cleared from the body much faster. The result is a rapid drop in the antibodies responsible for nerve and muscle damage.
This mechanism is different from older immunosuppressive treatments, which broadly dampen the entire immune system. Vyvgart targets one specific part of immune function, which is why its side effect profile is relatively focused.
IV vs. Subcutaneous Versions
Vyvgart comes in two forms, and the practical difference between them is significant for patients.
- Vyvgart (IV): Given as a one-hour intravenous infusion in a clinical setting. The dose is weight-based at 10 mg/kg, with a cap of 1,200 mg for patients weighing 120 kg or more.
- Vyvgart Hytrulo (subcutaneous): A fixed-dose injection given under the skin in 30 to 90 seconds. It combines the same active ingredient with an enzyme that helps the medication absorb into tissue, eliminating the need for an IV line.
Both versions are given once weekly for four weeks per treatment cycle. After completing a cycle, the next one is scheduled based on how the patient is doing clinically, with a minimum gap of 50 days from the start of the previous cycle. For many patients, this means treatment is not continuous but comes in periodic bursts as symptoms return.
Common Side Effects
Because Vyvgart lowers a portion of immune antibodies, infections are the most notable side effect. In the gMG clinical trial, respiratory tract infections occurred in 33% of patients on Vyvgart compared to 29% on placebo, and urinary tract infections occurred in 10% versus 5%. Headache was also common, reported by more than 10% of treated patients.
These infection rates are worth putting in context. The difference between Vyvgart and placebo for respiratory infections was relatively small (4 percentage points), suggesting the drug modestly increases susceptibility rather than dramatically suppressing immune defense. Still, patients receiving Vyvgart should be aware of infection signs and stay current on vaccinations before starting treatment.
Who Is Eligible for Treatment
For gMG, eligibility centers on antibody status. You need a confirmed positive blood test for AChR antibodies. Patients with other subtypes of myasthenia gravis, such as those driven by MuSK antibodies, are not covered under the current approval, though research in those populations continues. For CIDP, the approval is broader and does not hinge on a specific antibody subtype, since CIDP diagnosis relies more on nerve conduction studies and clinical evaluation than on a single blood marker.
In both conditions, Vyvgart is generally used in adults who have not responded well enough to standard treatments, or who need an alternative to therapies like plasma exchange or intravenous immunoglobulin that can be burdensome to receive repeatedly.