A Study to Assess Efficacy and Safety of Efgartigimod PH20 SC in Adults With Ocular Myasthenia Gravis

The purpose of this study is to evaluate the efficacy and safety of efgartigimod PH20 SC given by a pre-filled syringe in adult patients with ocular myasthenia gravis. The study consists of a part A (approximately 7 weeks) and a part B (up to 2 years). In part A, half of the participants will receive efgartigimod PH20 SC and the other half will receive placebo. In part B, all participants will receive efgartigimod PH20 SC. The participants will be in the study for about up to 2 years and 12 weeks.

Inclusion Criteria: * Is at least 18 years of age and the local legal age of consent for clinical studies * Has been diagnosed with myasthenia gravis and supported by seropositivity for AChR-Ab; or abnormal neuromuscular transmission demonstrated by abnormal neurophysiology testing and history on positive edrophonium chloride testing or demonstrated improvement on MG therapy" * Is MGFA Class I (any ocular muscle weakness) * Has a screening and baseline MGII (PRO) ocular score of at least 6 with at least 2 ocular items with a score of at least 2 Exclusion Criteria: * Other diseases that lead to eyelid drooping, peripheral muscle weakness, or diplopia * Known autoimmune disease or any medical condition other than indication under study that would interfere with an accurate assessment of clinical symptoms of ocular myasthenia gravis or puts the participant at undue risk