Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of INCB099280 in Participants With Advanced Solid Tumors

Inclusion Criteria: * Must have disease progression after treatment with available therapies that are known to confer clinical benefit or must be intolerant to or ineligible for standard treatment. * Histologically confirmed advanced solid tumors (protocol-defined select solid tumors) with measurable lesions per Response Evaluation Criteria In Solid Tumors Version 1.1 (RECIST v1.1) that are considered nonamenable to surgery or other curative treatments or procedures. * Eastern Cooperative Oncology Group performance status score of 0 or 1. * Life expectancy \> 12 weeks. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Laboratory values outside the Protocol-defined ranges. * Clinically significant cardiac disease. * History or presence of an electrocardiogram that, in the investigator's opinion, is clinically meaningful. * Untreated brain or central nervous system (CNS) metastases or brain or CNS metastases that have progressed (eg, evidence of new or enlarging brain metastasis or new neurological symptoms attributable to brain or CNS metastases). * Known additional malignancy that is progressing or requires active treatment. * Has not recovered to ≤ Grade 1 or baseline from toxic effects of prior therapy (including prior IO) and/or complications from prior surgical intervention before starting study treatment. * Prior receipt of an anti-PD-L1 therapy. * Treatment with anticancer medications or investigational drugs within protocol-defined intervals before the first administration of study drug. * A 28-day washout for systemic antibiotics is required. * Probiotic usage while on study and during screening is prohibited. * Active infection requiring systemic therapy. * Known history of Human Immunodeficiency Virus (HIV) * Evidence of hepatitis B virus or hepatitis C virus infection or risk of reactivation.