Interventional Study of INCB 99280 With Ipilimumab in Participants With Select Solid Tumors

Inclusion Criteria: * Prior systemic therapy, diagnoses and disease setting as follows: * For Part 1 (dose escalation), and no history of treatment with anti-CTLA-4 or anti-PD-(L)1 therapy and one of the following, * Unresectable or metastatic cutaneous melanoma, or * Unresectable of metastatic Child-Pugh Class A NDD not eligible for surgical and/or locoregional therapy, or * Intermediate or poor-risk advanced clear cell RCC, or * MSI-H or dMMR metastatic CRC and able to provide fresh or archival tumor tissue for central confirmation of MSI-H or dMMR. * For Part 2 (dose expansion), IO treatment -naïve, e.g., no prior receipt of an anti PD-1, anti-PD-L1 or PD-L1, anti-CTLA-4, GITR, LAG3, TIM3, OX-40, IL-2, 4-1BB or other immune modulator, and have not received prior systemic therapy and one of the following, * Unresectable or metastatic Child-Pugh Class A HCC not eligible for surgical and/or locoregional therapy, or * Intermediate - or poor-risk advanced clear cell RCC. * ECOG performance score of 0 or 1. * Life expectancy \> 3 months, in the opinion of the investigator. * Histologically confirmed solid tumors with measurable disease per RECIST v1.1. * Exception: HCC may be diagnoses based on cross-sectional multiphasic imagining using the AASLD criteria. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Known history of an additional malignancy. * Central nervous system (CNS) metastases requiring treat…