ADAPT Forward 2 - ISA2 - a Study to Evaluate the Safety, Tolerability and Efficacy of Empasiprubart IV Monotherapy in Participants With AChR-Ab Seropositive Generalized Myasthenia Gravis

ISA2 to Master Protocol ARGX-999-2-MG-2000 - an Exploratory, Phase 2a, Randomized, Double-Blinded, Placebo-Controlled Study to Evaluate the Safety, Tolerability, and Efficacy of Empasiprubart IV Monotherapy in Participants With AChR-Ab Seropositive Generalized Myasthenia Gravis

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 ISA2 is to investigate the effects of empasiprubart in participants with AChR-Ab seropositive generalized myasthenia gravis (gMG).

The ADAPT Forward master protocol is registered on https://clinicaltrials.gov/study/NCT07294170

More information can be found here: https://clinicaltrials.argenx.com/adaptforward2

Once the master protocol and ISA2 screening periods are completed, eligible participants will be randomized to receive empasiprubart IV or placebo in the double-blinded treatment period (DBTP). All participants will then receive open-label efgartigimod PH20 SC PFS in the safety follow-up period.

The study duration for each participant is approximately up to 45 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 before ISA screening or will complete immunization at least 14 days before the first IMP administration.

Exclusion Criteria:

• Clinical diagnosis of systemic lupus erythematosus (SLE).
• Is receiving concurrent complement inhibitors (eg, eculizumab, zilucoplan, ravulizumab, or others). Participants who received zilucoplan or eculizumab >2 months or ravulizumab >6 months before baseline are allowed to participate.
• Has received an FcRn antagonist, including efgartigimod, within 4 weeks before baseline.
• Had prior empasiprubart exposure.