• Male or female, between ≥18 to \<75 years of age at the time of signing the ICF.

• Willing and able to understand and adhere to the study procedures as specified in the protocol and comply with the study treatment.

• Have classic CAH due to 21-OHD confirmed by the Investigator and approved by the Medical Monitor.

• Participants with levels of morning serum A4 as follows:

‣ A4 \>ULN and treated with \<11 mg/m2/day (physiologic) GC doses

⁃ OR normal A4 (above mid-range to ≤ULN) and treated with ≥15 mg/m2/day GC doses

⁃ OR A4 \>ULN and treated with ≥11 mg/m2/day GC doses.

• On a stable (defined as no dose change of \>5 mg/day hydrocortisone equivalent within 2 months prior to Screening) regimen of GC replacement (e.g., hydrocortisone, prednisolone, prednisone, methylprednisolone, meprednisone, dexamethasone, cortisone acetate) at the time of informed consent.

• If treated with mineralocorticoids (fludrocortisone), the dose should be stable for at least 2 months prior to Screening without orthostatic hypotension, and with serum sodium and potassium in the normal range.

• If on estrogen therapy (any route), the dose must be stable for at least 3 months prior to Screening.