MP: ADAPT Forward - Master protocol of a platform study to evaluate the safety and efficacy of multiple regimens in participants with Myasthenia Gravis. ISA1: 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.

Prior treatment

• ISA 1 Main 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).

Other illness

• MP Main exclusion criteria: - Known autoimmune disease or any medical condition other than the indication under study that would interfere with an accurate assessment of clinical symptoms of MG or puts the participant at undue risk. - Is MGFA (Myasthenia Gravis Foundation of America) Class V

• MP Main inclusion criteria: o Is at least 18 years of age and the local legal age of consent for clinical studies o Has been diagnosed with MG consistent with MG's clinical features and with symptom severity appropriate for currently enrolling ISAs, per the investigator’s clinical judgment o If receiving MG therapy, including nonsteroidal immunosuppressive drugs (NSIDs), corticosteroids, or acetylcholinesterase (AChE) inhibitors either in combination or alone, the participant should receive a stable dosage before master protocol screening
• ISA 1 Main 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.