Androgen Reduction in Congenital Adrenal Hyperplasia

Inclusion Criteria: * Pre-pubescent girls (age 2 years \[12 kg\] to 8 years inclusive; skeletal age ≤9 years) or boys (age 2 years \[12 kg\] to 9 years inclusive; skeletal age ≤10 years). * Confirmed classic 21-hydroxylase deficiency evident by genotype groups A, A1 or B, or by clinical course. * Requirement for standard of care fludrocortisone (any dose) and ≥10 mg/m2/day of hydrocortisone for at least 1 month prior to the study consent. * Morning serum androstenedione concentrations \>1.5 x ULN after 7 days of dosing with doses of hydrocortisone required for physiologic replacement. * Informed consent . Exclusion Criteria: * Evidence of central puberty: Tanner Stage \>2 for breast development in girls or testicular volume \>4 mL in boys, or random LH \>0.3 mIU/mL. * Current or history of hepatitis from any etiology. * Abnormal liver function tests (transaminases\>3X ULN). * Abnormal renal function tests (BUN or creatinine \>1.5 ULN). * Significant anemia (hemoglobin \< 12 g/dl). * Clinically significant ECG abnormality * A history of a malabsorption syndrome. * Evidence of active malignancy. * Co-existent disease that may interfere with linear growth or that requires concomitant therapy that is likely to interfere with study procedures or results. * Treatment with potentially hepatotoxic medications, CYP2D6, strong inhibitors or inducers of CYP3A4 * Treatment with medications to affect puberty or synthesis of sex steroids, including gonadotropin releasing hormone agonist…