A Study to Evaluate INCB099280 in Participants With Select Solid Tumors Who Are Immune Checkpoint Inhibitor Naive

Inclusion Criteria: * Immunotherapy naive and without access to approved and/or available immune checkpoint inhibitor (ICI) therapy. * Measurable disease per RECIST v1.1. * One of the following disease settings: * Unresectable or metastatic Child-Pugh Class A hepatocellular carcinoma (HCC) not eligible for surgical and/or locoregional therapy and have not received prior systemic therapy or had disease progression following primary therapy. * Unresectable or metastatic cutaneous melanoma and have not received more than 1 previous systemic therapy for advanced disease. * Unresectable Stage III PD-L1-positive (TPS ≥ 50% using the Dako PD-L1 IHC 22C3 assay) non-small cell lung cancer (NSCLC) without actionable molecular biomarkers and have not received prior systemic therapy and where chemoradiation is contraindicated; in addition, able to provide fresh or archival tumor tissue for central confirmation of PD-L1 expression. * Stage IV PD-L1-positive (TPS ≥ 50% using the Dako PD-L1 IHC 22C3 assay) NSCLC without actionable molecular biomarkers and have not received prior systemic therapy; in addition, able to provide fresh or archival tumor tissue for central confirmation of PD-L1 expression. * Relapsed or Stage IV clear cell renal cell carcinoma (RCC) after having received 1 prior systemic therapy for relapsed or Stage IV disease. * Cisplatin-ineligible, locally advanced or Stage IV urothelial cancer (UC) and have not received prior systemic therapy for locally advanc…