The main objective of this study is to assess the safety and tolerability of crinecerfont in pediatric participants 3 months to <4 years of age with CAH.

Key Inclusion Criteria:

• Have a medically confirmed diagnosis of classic CAH (salt wasting or simple virilizing) due to 21-hydroxylase deficiency (21-OHD)
• Have received at least 3 months of hydrocortisone treatment before Day 1, with a stable dose for at least 4 weeks before screening.
• Have a body weight of at least 4.5 kilograms (kg) at screening.
• Have a newborn screen that is otherwise normal except for elevated 17-OHP or any other abnormality on newborn screen that was cleared upon evaluation by a pediatric specialist.

Key Exclusion Criteria:

• Have a known or suspected diagnosis of any of the other forms of classic CAH.
• Have any condition besides CAH that requires chronic daily therapy with orally administered steroids.
• Have any other clinically significant medical condition or chronic disease.

Note: Other protocol-defined inclusion and exclusion criteria may apply.