This is a Phase 1, multicenter, open-label, single-dose study to evaluate the safety and tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of NBI-77860 in subjects with congenital adrenal hyperplasia (CAH). The study will be conducted in approximately 15 adolescent females (12-18 years of age) with a documented medical diagnosis of classic 21-hydroxylase deficiency CAH. The study will include three independent dose cohorts of NBI-77860 (approximately 5 subjects per dose cohort). Ascending doses will be evaluated as part of a sequential-cohort design.