This is a multicenter, randomized, placebo-controlled, Phase 2 study to evaluate the pharmacologic effect, efficacy, and safety of SPI-62 in subjects with ACTH-dependent Cushing's syndrome. Each subject who provides consent and meets all inclusion and exclusion criteria will participate in a screening period (Days -35 to -8), a baseline period (Days -7 to -1), and a treatment period (Day 1 of Week 1 to Day 168 ± 3 days of Week 24) and, the option of long-term extension. Subjects have the option to continue with the study on active study drug and return to the site every 3 months for blood tests and study drug dispensing. The visits may be conducted remotely if testing can be arranged.