This is the phase 3 part of a multi-center, randomized, double-blind, placebo-controlled, group sequential designed, seamless phase 2/3 study to confirm the efficacy and safety of HBM9161 (HL161) subcutaneous injection for the treatment of gMG in patients with generalized myasthenia gravis.~Study drug will be administrated by cycle. Each cycle consists of 5-week treatment period, followed by a 4-week observation period (9 weeks in total). During the 5-week treatment period, subjects will receive 6 doses of study drug (HBM9161 680 mg or matching placebo) by subcutaneous injection, once a week (QW). After the 5-week treatment period, subjects will be followed up weekly to assess efficacy and safety. After the completion of first treatment cycle, subjects may start the second cycle of treatment if re-treatment criteria are met. Otherwise, subjects will be followed up weekly until they are eligible for the second cycle or the end of the study, whichever is earlier.
Primary study objective: To confirm the efficacy of HBM9161 subcutaneous injection for the treatment of gMG in Chinese patients