This study lasts about nine to twelve months and includes time to check if a person can join, time to receive treatment, and time for follow up visits. People will come to the clinic for regular visits. At these visits, they may receive medicine through a vein, have blood tests, physical exams, and heart checks, and answer questions about how they feel and what they can do each day. Everyone will first receive a medicine called efgartigimod, which is already approved for myasthenia gravis. If their symptoms only improve a little, they may then receive a second study medicine called empasiprubart along with the first medicine. This second medicine is being tested to help block parts of the immune system that may still be causing symptoms. After treatment, participants will keep having checkups to make sure the medicines are safe, even if they stop taking them.