ALXN1210-MG-306

This is a phase 3, randomized, double-blind, placebo-controlled, multicenter study that evaluates using ravulizumab infusions as treatment for patients with generalized Myasthenia Gravis. Participants will receive either ravulizumab for the duration of the study or placebo during the 26-week randomized-controlled period of the stufy and then enter the open-label extension period where they will receive ravulizumab. The main outcome will look at the change from baseline in Myasthenia Gravis-Activities of Daily Living (MG-ADL) score at week 26 (end of randomized period).

Inclusion Criteria

• Diagnosed with Myasthenia Gravis at least 6 months (180 days) prior to the date of the Screening Visit as confirmed by specific criteria.
• Myasthenia Gravis Foundation of America Clinical Classification Class II to IV at screening
• MG-ADL profile must be ≥ 6 at screening and randomization (Day 1)

Exclusion Criteria

• Any active or untreated thymoma. History of thymic carcinoma or thymic malignancy unless deemed cured by adequate treatment with no evidence of recurrence for ≥ 5 years before screening.
• Use of the following within the time period specified below:
• IV immunoglobulin within 4 weeks of randomization
• Use of plasma exchange within 4 weeks of randomization
• Use of rituximab within 6 months of screening
• Participants who have received previous treatment with complement inhibitors (ie eculizumab)

Study Requirements

1 screening visit, 12 study visits- 4 3.5hr infusion visits (includes observation period), 8 clinic visits for evaluations. Option to continue on through extension period which has 18 visits total- 14 infusion visits and 4 clinic evaluation visits. Each infusion visit will include two blood draws- pre infusion and post infusion.