A Study to Assess Pharmacokinetics, Safety, and Tolerability of Atumelnant in Healthy Japanese and Caucasian Participants

Inclusion Criteria: * Healthy male or female participants, 18 to 55 years old, inclusive, at the Screening Visit. * Healthy status as defined by the absence of evidence of any clinically significant, in the opinion of the Investigator, active or chronic disease following a detailed medical and surgical history, a complete physical examination including vital signs, 12-lead electrocardiogram (ECG), hematology, clinical chemistry, coagulation, serology, and urinalysis. The tests may be repeated once at Screening and at admission on Day -1 if necessary and deemed appropriate by the Investigator or designee. * Body mass index (BMI) between 18.0 and 30.0 kg/m2, inclusive, at the Screening Visit and at admission on Day -1. * Meeting the criteria at the time of consent for one of the following ethnic groups: * Japanese participants must have been born in Japan to parents and grandparents of Japanese ethnic descent as evidenced by verbal confirmation and documented in a self-reported family tree form, have lived less than 10 years outside of Japan, and have no significant change in lifestyle, including diet, since leaving Japan. * Caucasian participants must be considered White of European descent. * Participant has a peak 30- or 60-minute ACTH stimulated serum cortisol ≥18 μg/dL during 250 μg high-dose ACTH/cosyntropin stimulation test conducted at Screening. * Participant has normal morning serum cortisol collected at approximately 08:00 AM (±2 hours) at admission on Day -1 and does not have signs and symptoms of adrenal insufficiency as deemed by the Investigator or designee. Exclusion Criteria: * Participant is breastfeeding or has a positive serum pregnancy test at Screening or at admission on Day -1. * Participant has a blood loss ≥500 mL or donated blood within 3 months prior to admission on Day -1. * Participant has received atumelnant previously or has previously been enrolled in this clinical study. * Participant has received any investigational drug within the past 30 days or 5 half lives, whichever is longer, prior to the first dose of study intervention on Day 1. * Participant is unwilling to refrain from strenuous, unaccustomed exercise and sports, defined as greater than 30 minutes per day, 3 days prior to admission on Day -1. * Participant has history of hypersensitivity to study intervention or any of the excipients or to medicinal products with similar chemical structures. * Participant has used any prescription medication without approval of the Investigator or designee within 14 days prior to admission on Day -1. By exception, hormonal contraceptives are permitted throughout the study and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines are allowed up to 14 days prior to admission on Day -1. * Venous access considered inadequate for sample collection.