Congenital Myasthenic Syndrome

The purpose of this study is to assess efficacy and safety of adimanebart in participants at least 12 years of age with DOK7-, MUSK-, AGRN-, or LRP4- Congenital Myasthenic Syndromes (CMS). The study aims to determine whether adimanebart is safe and can help people with CMS feel better and perform daily activities more easily. The study includes a double-blinded treatment period (DBTP) and an Open- label extension period (OLE). In the DBTP, all participants will be randomized in a 1:1 ratio to adimanebart or placebo. Participants who complete the DBTP will continue to the OLE. Additionally, participants who complete part of the active-treatment period of ARGX-119-2302 study are eligible to enroll in the OLE of this study. In the OLE, all participants will receive open-label adimanebart. After final IMP dose, the participants will enter a follow-up period and their health will be monitored. The total duration of the study is up to approximately 152 weeks (2 years and 11 months). More information can be found here: clinicaltrials.argenx.com/Comets

Participants will attend up to 4 study visits to collect clinical assessments. The assessments will evaluate participants' symptoms and quality of life to understand disease activity in patients with CMS due to mutations in DOK7, MUSK, AGRN, or LRP4. More information can be found here: https://clinicaltrials.argenx.com/cms

Patients with Congenital Myasthenic Syndrome will be treated with Mesenchymal Stem Cell Exosome solution.

The Congenital Muscle Disease Patient and Proxy Reported Outcome Study (CMDPROS) is a longitudinal 10 year study to identify and trend care parameters, adverse events in the congenital muscle diseases using the Congenital Muscle Disease International Registry (CMDIR) to acquire necessary data for adverse event calculations (intake survey and medical records curation). To support this study and become a participant, we ask that you register in the CMDIR. You can do this by visiting www.cmdir.org. There is no travel required. The registry includes affected individuals with congenital muscular dystrophy, congenital myopathy, and congenital myasthenic syndrome and registers through the late onset spectrum for these disease groups. The CMDIR was created to identify the global congenital muscle disease population for the purpose of raising awareness, standards of care, clinical trials and in the future a treatment or cure. Simply put, we will not be successful in finding a treatment or cure unless we know who the affected individuals are, what the diagnosis is and how the disease is affecting the individual. Registering in the CMDIR means that you will enter demographic information and complete an intake survey. We would then ask that you provide records regarding the diagnosis and treatment of CMD, including genetic testing, muscle biopsy, pulmonary function testing, sleep studies, clinic visit notes, and hospital discharge summaries. Study hypothesis: 1. To use patient and proxy reported survey answers and medical reports to build a longitudinal care and outcomes database across the congenital muscle diseases. 2. To generate congenital muscle disease subtype specific adverse event rates and correlate with key care parameters.