This is a Phase 2 multicenter, single-blind, multiple dose study to evaluate the safety and efficacy of orally administered ATR-101 in subjects with classic congenital adrenal hyperplasia (CAH). Treatment duration will range from a minimum of approximately 2 months to 6 months per subject. A subject may receive a minimum of one dose level or up to a maximum of 5 dose levels, in sequentially increasing dose strengths. Each dose level will last 28 days.

Inclusion Criteria:

• Documented historical diagnosis of classic CAH due to 21-hydroxylase deficiency based on: Documented genetic mutation in the CYP21A2 enzyme consistent with a diagnosis of classic CAH, or historical documentation of elevated 17-hydroxyprogesterone
• Biochemical marker of disease status of 17-hydroxyprogesterone ≥ 4 times the upper limit of normal
• Chronic glucocorticoid replacement therapy for at least 6 consecutive months
• Stable glucocorticoid and mineralocorticoid regimen for at least 1 month

Exclusion Criteria:

• Non-classic CAH
• Other causes of adrenal insufficiency
• Surgery within the previous 3 months prior to screening or planned surgery during study participation
• History of active cancer requiring medical or surgical therapy within the past 6 months

Adverse events were collected from the time the patient signed informed consent until 4 weeks after the last dose of active drug.

The small number of subjects analyzed as a result of the rarity of the disease (congenital adrenal hyperplasia).and the stage of the study (phase 2a)