Phase 2 Study to Assess Efficacy & Safety of WP1302 Prevent Relapse of MMI w/Draw in Subj. w/ Graves' dz

This is a Phase 2, double-blind, placebo controlled, Methimazole (MMI) withdrawal study in subjects with Graves' disease. The study consists of up to 5 periods: a screening period of up to 2 weeks; a WP1302 or placebo titration with Methimazole period of 12 weeks; a full dose of WP1302 or placebo with Methimazole tapering period of 26 weeks; a follow-up period of 4 weeks; and an extended follow-up period of 6 months. After screening, eligible subjects will be randomized to treatment at a ratio (stratified by size of goiter \[grade 0 or 1; grade 2\], WHO classification) of 1:1:1:1 to either any group of Methimazole with WP1302 at a dose of 400 μg, 800 μg, or 1200 μg, or the group of Methimazole with placebo. Subjects who have a confirmed diagnosis of Graves' disease based on medical history and/or physical examination and laboratory evidence, well controlled, with normalized thyroid function tests, and have received stable background Methimazole (i.e., not requiring dose adjustments) not exceeding 20 mg daily for at least 8 weeks and no more than 24 weeks are eligible to this study. All subjects enrolled in this study will receive Methimazole treatment in titration period. During the titration period, subjects will receive WP1302 or placebo by subcutaneous (S.C.) injection every 2 weeks (Q2W) for 12 weeks while continuing MMI (see "Dosing" below). The dose of WP1302 will be titrated up to the target dose assigned to the subject during this period (see "Dosing" below). Thyroid symptoms and function tests will be evaluated every 2 weeks. The investigator may adjust the frequency of thyroid function tests based on safety considerations. If a subject does not maintain euthyroidism, which is defined as total T3 60-180 ng/dL, free T4 0.8-1.8 ng/dL, and TSH 0.5-5 mU/L, during the "WP1302 titration period", the subject will be discontinued from Investigational Medicinal Product (IMP) (i.e., WP1302 or placebo) and the subject is still required to complete the end-of study visit. During the 26-week full dose of WP1302 with Methimazole tapering period, subjects who have maintained euthyroidism during the "WP1302 titration period" will be dosed with WP1302 at 400, 800, or 1200 μg with down-titrated Methimazole. Thyroid symptoms and function tests will be evaluated every 2 weeks. The investigator may adjust the frequency of thyroid function tests based on safety considerations. Subjects who experience disease relapse will be treated with Methimazole as first-line therapy (see "Management of Relapse and Rescue Medication" below). At the end of the full dose of WP1302 with Methimazole tapering period, subjects will have 4 weeks of follow-up, and complete an end-of-study visit at Week 42. All the subjects will subsequently be enrolled in an extended safety follow-up period for an additional 6 months. Subjects who remain euthyroid will continue to be monitored for efficacy during the long-term follow-up.