May 2, 2025 -- The FDA has approved a new treatment for generalized myasthenia gravis (gMG), a disease that causes severe muscle weakness, faster muscle fatigue, and difficulty in speaking and swallowing. It offers long-lasting option for symptom relief to about 100,000 patients living with the disorder in the United States.
The drug, known as nipocalimab but sold as Imaavy, is the first and only drug of its kind to target the root cause of gMG in adults and children aged 12 or older who have certain antibodies linked to this condition.
gMG is a long-term autoimmune disorder in which the body’s immune system makes harmful antibodies that mistakenly attack the connection points between nerves and muscles (called neuromuscular junctions). This interrupts the nerve signals that control muscle movement, making it difficult for muscles to work.
The FDA’s decision was based on an ongoing clinical study involving 199 gMG patients (including 153 with antibodies) who weren’t getting a good response from their current treatments, according to a news release from Johnson and Johnson, the drug’s maker. Over 24 weeks, they were given either Imaavy or a placebo, along with standard care. Results showed that Imaavy helped patients regain important daily abilities like chewing, swallowing, speaking, and breathing better than those taking the placebo. It also reduced levels of harmful autoantibodies by up to 75% from the first dose and kept them low throughout the study. Additionally, these benefits continued over 20 months as seen in an ongoing follow-up study.
In another ongoing clinical trial involving seven children aged 12 to 17 with antibody-positive gMG who were not getting enough help from standard care, adding Imaavy to standard treatments reduced the levels of harmful antibodies by 69% over 24 weeks and provided relief from symptoms.
Imaavy is a lab-made monoclonal antibody that works by selectively blocking a protein called FcRn. This helps reduce the levels of harmful antibodies that cause gMG symptoms without noticeably affecting the rest of the immune system functions. It is given as an IV infusion once every two weeks.
The most common side effects of Imaavy include airway infection; swelling in the hands, ankles, or feet; and muscle spasms. The drug may also cause serious side effects, including a higher risk for infections, allergic reactions, and infusion-related reactions. Patients are advised to contact their doctor right away if they have fever, chills, cough, a burning sensation while peeing, severe itching, hives, difficulty in breathing, chest pain, headache, dizziness, rash, or redness of skin during or a few days after Imaavy infusion. Before or during treatment, patients should also report any past allergic reactions, current or recent infections, and any recent or planned vaccinations — especially live vaccines, which should be avoided while on Imaavy. They must also share a full list of all the medicines, supplements, and vitamins they take to prevent any possible interactions. Women should inform their doctors if they are pregnant, planning to become pregnant, or breastfeeding as it’s not yet clear if Imaavy is safe for a baby.
