Diagnosis of any form of CAH other than classic 21-OHD.
Treated with other GC formulations as defined by the following: unstable doses of inhaled GCs, and/or injectable or oral betamethasone or triamcinolone use within 30 days of first Screening Visit.
Stress dose of GC therapy within 1 week of start of Screening, defined as any dose above the normal maintenance dose, including but not limited to IV or IM hydrocortisone.
History of bilateral adrenalectomy, hypopituitarism, or other condition requiring chronic GC therapy.
Clinically significant medical condition or abnormal laboratory tests, as judged by the Investigator, other than CAH.
History of major surgery/surgical therapy for any cause within 30 days prior to first Screening Visit.
Diabetes mellitus treated with insulin for less than 6 weeks prior to Screening, or with change in total daily insulin dose by >30% within 6 weeks prior to Screening.
Poorly controlled diabetes mellitus defined as having an HbA1c ≥8.5% (≥69 mmol/mL) or estimated HbA1c based on fructosamine if HbA1c is not evaluable (eg, due to hemoglobinopathies).
Participants with hypothyroidism who are not receiving adequate hormone replacement therapy based on thyroid hormone levels measured at the time of Screening, as determined by the Investigator.
History of unstable angina or acute myocardial infarction within 12 weeks prior to Screening or other clinically significant cardiac disease at the time of Screening as judged by the Investigator.
Participants with polycythemia and prior thrombotic events as judged by the Investigator.
Concomitant mental condition rendering him/her unable to understand the nature, scope, and possible consequences of the study, and/or evidence of poor compliance with medical instructions.
History of cancer excluding cured/treated dermal squamous or basal cell carcinoma or cervical carcinoma in situ.
Women who are pregnant or lactating or, if of childbearing potential, who are unwilling to use highly effective contraception as described in this study. Male participants who are unwilling to use highly effective contraception as described in this study.
Known history of illicit drug or alcohol abuse within the last year.
Chronic use of antiandrogen therapy in the past 3 months (eg, spironolactone, finasteride, cyproterone acetate, flutamide) prior to Day 1.
Use of testosterone, androgen-containing supplements, aromatase inhibitors, or growth hormone.
Use of medications that are strong or moderate inducers of CYP3A4 within 30 days prior to Day 1 of the study. These include but are not limited to apalutamide, carbamazepine, enzalutamide, mitotane, phenytoin, rifampin, or St. John’s wort.
Use of medications (all routes of administration; ie, oral, topical, and inhaled) or ingestion of food (eg, grapefruit juice) that are strong or moderate inhibitors of CYP3A4 within 7 days prior to Day 1 of the study. Examples include but are not limited to protease inhibitors and NNRTIs for HIV or HCV, antifungals (eg, ketoconazole), some antibiotics (eg, ciprofloxacin) and calcium channel blockers (eg, diltiazem), and antidepressants (eg, fluvoxamine).
Use of medications that are strong or moderate inducers of P-gp within 30 days prior to Day 1 of the study. These include but are not limited to apalutamide, carbamazepine, fosphenytoin, lorlatinib, phenytoin, rifampicin, or St. John's wort.
Use of medications that are strong or moderate inhibitors of P-gp within 14 days prior to Day 1 of the study. These include but are not limited to amiodarone, carvedilol, clarithromycin, dronedarone, itraconazole, lapatinib, protease inhibitors and NNRTIs for HIV or HCV (lopinavir and ritonavir, propafenone, quinidine, ranolazine, ritonavir, saquinavir and ritonavir, telaprevir, tipranavir and ritonavir), or verapamil, propafenone, quinidine, or ranolazine.
Use of P-gp substrates, such as digoxin, edoxaban, fexofenadine, and dabigatran extexilate, as they may be subject to enhanced absorption and increased exposure when given concomitantly with atumelnant.
Use of any investigational drug within the past 60 days or 5 half-lives (whichever is longer) prior to the first dose; or plan to use an investigational drug in another study.
Average (of 3 ECGs) QTcF interval >450 msec (men) or >470 msec (women), PR interval >220 msec, QRS interval >120 msec, second- or third-degree atrioventricular block, left bundle branch block, or hemiblock at Screening.
Renal insufficiency as measured by eGFR rate using the CKD-EPI formula <40 mL/min/1.73m2 .
Significant liver disease or ALT and/or AST >3×ULN, and/or TBil >1.5×ULN during Screening. Participants with previously diagnosed Gilbert’s syndrome not accompanied by other hepatobiliary disorders and associated with TBil <3.5 mg/dL (<51.3 μmol/L) will be permitted.
Known history of, or concern for, risk of hypersensitivity reaction to atumelnant or any of its excipients.
Participants who are committed to an institution by virtue of an order issued either by the judicial or administrative authorities.
Participants with an increased risk of developing adrenal insufficiency as judged by the Investigator.
Use of oral betamethasone or budesonide within 30 days of Screening.
Severe erythrocytosis as judged by the Investigator.
Use of a corticotropin-releasing factor receptor antagonist within 14 days of Screening.