This is a study that will evaluate the ability of Tildacerfont to reduce the glucocorticoid steroid dose used by adult CAH subjects. The first 24-weeks will be a double-blind, placebo controlled, comparison of Tildacerfont vs Placebo. The following 52-weeks will allow all subjects to move to open label Tildacerfont to continue to reduce steroid dose where appropriate, and observe long term safety. Subjects will be offered a long term open label extension up to 240 weeks.
An investigation of the ability of Tildacerfont to reduce supraphysiologic glucocorticoid dosing in classic CAH subjects up to 76 weeks of treatment. Optional open label extension up to 240 weeks.