A Study of KH607 as Monotherpy in Adults Participants With Major Depressive Disorder

This trial consists of two parts: a short-term study and a long-term study. The short-term study adopts a multicenter, randomized, double-blind, placebo-controlled parallel-group design, including a 14-day screening period；a 3-week double-blind treatment period, and a 3-week off-drug follow-up period. The long-term study uses a multicenter, open-label, single-arm design. Subjects who complete all study procedures of the short-term study and achieve a ≥50% reduction in the 17-item Hamilton Depression Rating Scale (HAM-D17) score at the end of the short-term study will be eligible to enter the long-term study. All enrolled subjects will receive repeated treatment with KH607 Tablets. The dosing regimen is 20 mg KH607 Tablets administered orally once every night before bedtime. A treatment course consists of 21 consecutive days of dosing, with an interval of no less than 6 weeks between two courses. Subjects may receive a maximum of 3 treatment cycles, and the maximum duration of the long-term study is 27 weeks.