ADAPT Forward 1 - ISA1 - a Study to Evaluate Empasiprubart IV as add-on Therapy to Efgartigimod IV in Participants With AChR-Ab Seropositive Generalized Myasthenia Gravis With a Partial Clinical Response to Efgartigimod

This study is part of the ADAPT Forward platform study (NCT07294170). ADAPT Forward is a platform study with the aim to look at how safe different drugs are and how well they work for people with myasthenia gravis. The goal is to find the best therapeutic approach to reduce patients' side effects and improve their quality of life. The aim of this ISA1 is to evaluate the safety and therapeutic relevance of empasiprubart as add-on therapy to efgartigimod in participants with AChR-Ab seropositive generalized myasthenia gravis. The ADAPT Forward master protocol is registered on https://clinicaltrials.gov/study/NCT07294170

Once the master protocol and ISA1 screening periods are completed, eligible participants can enroll in the run-in period (part A) where they will receive efgartigimod IV. Eligible participants can then continue to the add-on period (part B) where they will receive both efgartigimod IV and empasiprubart IV. Participants who are not eligible for part B will continue directly to the safety follow-up period (part C) where they will receive efgartigimod IV only. The study duration for each participant is approximately up to 54 weeks.

Inclusion Criteria: * Is seropositive for anti-acetylcholine receptor antibodies (AChR-Ab) * Has confirmed diagnosis of gMG and is Myasthenia Gravis Foundation of America (MGFA) Class II, III, IVa, or IVb * Has documented immunization against encapsulated bacterial pathogens (Neisseria meningitidis and Streptococcus pneumoniae) within 5 years of ISA screening or is willing to receive immunization at least 14 days before the first study drug administration Exclusion Criteria: * Clinical diagnosis of systemic lupus erythematosus (SLE) * Any known complement deficiency * Current administration of a complement inhibitor or received zilucoplan or eculizumab \<2 months or ravulizumab \<6 months before the first study drug administration * Patients proven to be refractory to efgartigimod (ie, not achieving a clinically meaningful improvement in total Myasthenia Gravis Activities of Daily Living (MG-ADL) score defined as an improvement of ≥2 points)