A Ph2b to Evaluate Clinical Efficacy and Safety of Tildacerfont in Adult CAH

Inclusion Criteria:

1. Male and female subjects ≥18 years old at screening

2. Has a known childhood diagnosis of classic CAH due to 21-hydroxylase deficiencybased on genetic mutation in CYP21A2 and/or documented (at any time) elevated 17-OHPand currently treated with HC, HC acetate, prednisone, prednisolone,methylprednisolone (or a combination of the aforementioned GCs)

3. Has been on a stable, supraphysiologic dose of GC replacement (defined as ≥15 mg/dayand ≤60 mg/day in HCe) for ≥1 month before screening

4. Has A4 >ULN at both screening and Week 4 (measured before any AM GC dose) if dailyGC dose <30 mg OR has A4 >2.5x ULN at both screening and Week 4 (measured before anyAM GC dose)

5. For subjects with the salt-wasting form of CAH, subject has been on a stable dose ofmineralocorticoid replacement for ≥1 month before screening

6. Agrees to follow contraception guidelines. Male subjects must also agree to refrainfrom donating sperm throughout the treatment period and for 90 days after the lastdose of study drug.

7. Is able to understand all study procedures and risks involved and provides writteninformed consent indicating willingness to comply with all aspects of the protocol.

Exclusion Criteria:

1. Has a known or suspected diagnosis of any other known form of classic CAH (not dueto 21 hydroxylase deficiency)

2. Has a history that includes bilateral adrenalectomy or hypopituitarism

3. Has a history of allergy or hypersensitivity to tildacerfont, any of its excipients,or any other CRF1 receptor antagonist

4. Current treatment with dexamethasone as GC therapy for CAH a. Prior treatment with dexamethasone is allowed as long as the transition to analternative GC regimen (eg, HC, prednisone, or prednisolone) has resulted in astable dose of GC replacement for ≥1 month before screening.

5. Is not adherent to GC or study drug dosing regimen during the Run-in Period (definedas taking <80% of expected doses based on drug accountability)

6. Shows clinical signs or symptoms of adrenal insufficiency

7. Has had a clinically significant unstable medical condition, medically significantillness, or chronic disease occurring within 30 days of screening, including but notlimited to:

8. An ongoing malignancy or <3 years of remission history from any malignancy,other than successfully treated localized skin cancer

9. eGFR of <45 mL/min/1.73 m2

10. Current or history of liver disease (with the exception of Gilbert's syndrome).

11. History of alcohol or substance abuse within the last year, or any significanthistory of alcohol or substance abuse that would likely prevent the subjectfrom reliably participating in the study, based on the opinion of theInvestigator

12. Active hepatitis B, hepatitis C, or HIV at screening

13. Subjects who plan to undergo bariatric surgery during the study are excluded.

14. Any other condition that would impact subject safety or confound interpretationof study results

15. Psychiatric conditions, including but not limited to bipolar disorder,schizophrenia, or schizoaffective disorders that are not effectively controlled onmedication and may have an adverse impact on study compliance. Symptoms includinghallucinations, delusions, and psychosis are exclusionary. Additionally:

16. Increased risk of suicide based on the Investigator's judgment or the resultsof the C-SSRS conducted at screening and Week 6 (eg, C-SSRS Type 3, 4, or 5ideation within the past 6 months or any suicidal behavior within the past 12months)

17. HADS score >12 for either depression or anxiety at screening or Week 6

18. Has clinically significant abnormal ECG or clinical laboratory results. Abnormalresults that must be reviewed and discussed with the Medical Monitor to determineeligibility for this study include but are not limited to:

19. Any clinically meaningful abnormal ECG results, including QTcF >450 ms for maleparticipants or >470 ms for female participants

20. ALT >2x ULN

21. Total bilirubin >1.5x ULN

22. Total bile acids >5x ULN

23. Routinely works overnight shifts

24. Subjects with travel plans/work schedules that result in significant and frequentchanges in time zones (>2 hours) will require Medical Monitor approval forenrollment.

25. Females who are pregnant or nursing

26. Use of any other investigational drug from 30 days or 5 half-lives (whichever islonger) before screening to the end of the study

27. Use of the following drugs from 30 days or 5 half-lives (whichever is longer) beforeDay 1 to the end of the study:

28. Rosiglitazone, aromatase inhibitors, testosterone, growth hormones, or anyother medication or supplement that could impact subject safety or confoundinterpretation of study results

29. The following drugs: i. Moderate to strong inhibitors and/or inducers of CYP3A4 ii. Sensitive substratesor narrow-therapeutic-range substrates of CYP3A4 (except hormonal contraceptioncontaining ≤35 μg ethinyl estradiol) iii. Sensitive substrates ornarrow-therapeutic-range substrates of BCRP (except those that can be administeredQD in the morning, separated by approximately 10 hours from evening administrationof study drug)

30. Donation or receipt of blood from 90 days before Screening to the end of the study;donation or receipt of platelets, white blood cells, or plasma from 30 days beforeScreening to the end of the study