Study of Relacorilant in Combination With Pembrolizumab for Patients With Adrenocortical Carcinoma Which Produces Too Much Stress Hormone (Cortisol)

Inclusion Criteria: * Histologically or cytologically confirmed ACC (advanced unresectable and/or metastatic) * Measurable disease based upon RECIST v1.1 as determined by the Investigator. * Documented GC excess (too much cortisol). * For patients who have received mitotane within 3 months prior to screening, mitotane levels must be \<4 mg/L at screening. * Eastern Cooperative Oncology Group (ECOG) performance status ≤2. * Adequate organ and bone marrow function (determined through blood and urine tests) * Negative pregnancy test for patients of childbearing potential at the Screening and every 6 weeks (+ or - 7 days) in female patients of childbearing potential. Exclusion Criteria: * Major surgery within 4 weeks prior to enrollment. If the participant underwent major surgery, they must have recovered adequately prior to starting study treatment. * Have received and responded (complete response \[CR\] or partial response \[PR\]) to prior treatment with any prior checkpoint inhibitor or any other agents targeting T-cell stimulation pathways * Taking a concomitant medication that is a strong Cytochrome P450 3A (CYP3A) inducer, or that is a substrate of CYP3A with a narrow therapeutic index * Known untreated parenchymal brain metastasis or have uncontrolled central nervous system (CNS) metastases. Patients must not require steroids and must be neurologically stable without corticosteroids for a minimum of 3 weeks prior to the commencement of the study. Patients with neurologic symptoms must undergo a CT/MRI to rule out occult CNS metastases. * Requirement for chronic systemic GC treatment, such as active autoimmune disease requiring systemic treatment (corticosteroids or other immunosuppressive medication) * Patients requiring inhaled glucocorticoids but have no other alternative treatment option if their condition deteriorates during the study. * Clinically relevant toxicity from prior systemic cytotoxic therapies or radiotherapy that in the opinion of the Investigator has not resolved to NCI-CTCAE v5.0 Grade 1 or less prior to the first dose of relacorilant. * Treated with the following prior to the first dose of relacorilant: 1. Any investigational product, systemic anticancer therapy, or radiation therapy within 21 days 2. Antibodies or anticancer vaccines within 60 days 3. Mifepristone or other GR antagonists within 5 half-lives of these medications 4. Adrenostatic medications within 5 half-lives of these medications * History of severe hypersensitivity to another monoclonal antibody * Other concurrent cancer or a history of another invasive malignancy within the last 3 years that has a likelihood of recurrence of \>30% within the next 5 years. Adequately treated basal and squamous skin cancers, ductal carcinoma in situ, cervical cancer, prostate cancer, non-muscle invasive urothelial cancer or other tumors curatively treated with no evidence of disease are permissible. * Human immunodeficiency virus (HIV) or current chronic/active infection with hepatitis C virus or hepatitis B virus including: Chronic or active hepatitis B as diagnosed by serologic tests. In equivocal cases, hepatitis B or C polymerase chain reaction may be performed and must be negative for enrollment. * Clinically significant uncontrolled condition(s) or a condition which, in the opinion of the Investigator, may confound the results of the trial or interfere with the patient's participation, including but not limited to: 1. Unstable angina pectoris, angioplasty, cardiac stenting, or myocardial infarction 3 months before study entry. 2. Active infection that requires parenteral antibiotics. 3. Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.