A Study to Evaluate the Safety, Tolerability, and Antitumor Activity of INCB001158 Plus Epacadostat, With or Without Pembrolizumab, in Advanced Solid Tumors

Inclusion Criteria: * For Phase 1, subjects with histologically or cytologically confirmed advanced or metastatic solid tumors that have failed prior standard therapy (disease progression; subject intolerance is also allowable). * For Phase 2, subjects with the following tumor types who meet protocol-defined criteria: advanced or metastatic NSCLC, melanoma, urothelial carcinoma, SCCHN, SCLC, and CRC. * Presence of at least 1 measurable lesion by computed tomography or magnetic resonance imaging per RECIST v1.1. * Eastern Cooperative Oncology Group (ECOG) performance status 0 to 1. * Resolution of all toxicities and any toxic effect(s) of the most recent prior therapy to Grade 1 or less (except alopecia). Subjects with ≤ Grade 2 neuropathy are an exception and may enroll. * Adequate renal, hepatic, and hematologic functions per protocol-defined laboratory parameters within ≤ 7 days before treatment initiation. Exclusion Criteria: * Participation in any other study in which receipt of an investigational study drug or device occurred within 2 weeks or 5 half-lives (whichever is longer) before first dose. * Has received a prior monoclonal antibody within 4 weeks or 5 half-lives (whichever is shorter) before administration of study drug. * Prior chemotherapy or targeted small molecule therapy within 2 weeks before administration of study treatment. * Prior therapy with an IDO1 or arginase 1 inhibitor. * Active autoimmune disease that has required systemic treatment in past 2 years. Replacement therapy (eg, thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment. * Receipt of a live vaccine within 30 days before the first dose of study treatment. * Any history of serotonin syndrome after receiving serotonergic drugs. * Use of protocol-defined prior/concomitant therapy. * Known or suspected defect in the function of the urea cycle. * History of gastrointestinal condition that may affect drug absorption.