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Vyvgart Improves Daily Function for Seronegative MG in Phase 3 Trial

Written by Ted Samson
Posted on September 24, 2025

A new study found that efgartigimod alfa-fcab (sold under the brand name Vyvgart) may help more people living with myasthenia gravis (MG), including those who have tested negative for the most common MG antibodies. Results from this study could lead to expanded treatment options for people who previously had limited therapy choices.

🗳️ In the past year, have you talked with your doctor about new treatment options for myasthenia gravis?
Yes, I have, and we made a change to my treatment plan.
Yes, I have, but we didn’t make any changes to my plan.
No, but I plan to.
No, and I don’t plan to

What Is Efgartigimod?

Efgartigimod is a type of targeted therapy called an FcRn blocker. It works by lowering levels of certain harmful antibodies (immune proteins) in the body. The drug is already approved to treat adults with generalized myasthenia gravis who test positive for antibodies against the acetylcholine receptor (AChR). These antibodies interfere with communication between nerves and muscles, causing muscle weakness and fatigue.

About 80 percent of people with MG test positive for these AChR antibodies in blood tests. However, up to 20 percent are “seronegative” — meaning they test negative for AChR antibodies but may have other antibodies, like MuSK or LRP4. They may not test positive for any of these antibodies, which is called triple seronegative MG. Until now, people in seronegative groups have had fewer proven treatment options.

What Did the Study Find?

The phase 3 study tested people with seronegative MG, including all three major subtypes: MuSK-positive, LRP4-positive, and triple seronegative. The study included 119 participants across North America, Europe, China, and the Middle East. Participants received either efgartigimod or a placebo (inactive treatment, also known as a sugar pill).

Those Who Took Efgartigimod Had Improved Daily Function

People who received efgartigimod saw a “statistically significant and clinically meaningful” improvement in how symptoms affected their ability to do daily activities, such as speaking, chewing, and swallowing.

Efgartigimod Was Well Tolerated

Efgartigimod was well tolerated, and no new safety issues were found. Side effects were similar to those of previous studies, including possible risk of infection and allergic reactions. The most common side effects include respiratory tract infection, headache, and urinary tract infection.

Based on these results, drugmaker Argenx plans to ask the U.S. Food and Drug Administration (FDA) to expand approval for the drug so more people with seronegative MG can access the treatment. The company aims to submit this application by the end of 2025.

Why This Matters for People With Myasthenia Gravis

Until recently, treatment advances mainly focused on people with myasthenia gravis who test positive for AChR or MuSK antibodies. In 2023, the FDA approved rozanolixizumab (Rystiggo) for adults with generalized MG who are AChR- or MuSK-positive. More recently, in April 2025, the FcRn blocker nipocalimab-aahu (Imaavy) was approved for people 12 and older with generalized MG who are AChR- or MuSK-positive. These new options expand the treatment landscape for some people with MG.

However, there are currently no FDA-approved treatments for people with anti-LRP4 antibodies or those who are triple seronegative — two groups with high unmet need and sometimes more severe disease. If Vyvgart is approved for these subtypes, it could become the only FcRn blocker with such a broad label, filling an important treatment gap.

If you’re living with MG and struggling to find a treatment plan that meets your needs, talk with your healthcare provider. Together, you can explore the available options — including newly approved therapies — to find an approach that works best for you.

Learn about nine treatment options for MG, including medications, surgery, and lifestyle changes.

Connect With Others Who Understand

On MGteam, people share their experiences with myasthenia gravis, get advice, and find support.

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I took Vyvgart as IV for a 6 month period, one infusion every month
I got no improvement.

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