To Assess the Safety, Tolerability and Pharmacokinetics of INCB086550

Inclusion Criteria:

* Willing and able to conform to and comply with all Protocol requirements, including all scheduled visits, Protocol procedures, and the ability to swallow oral medication.

  * Histologically or cytologically confirmed diagnosis of any locally advanced or metastatic solid tumors with measurable lesions per RECIST v1.1 not amenable to local or other curative therapy.
  * Disease progression after treatment with available therapies that are known to confer clinical benefit or intolerant to or ineligible for standard treatment.
  * ECOG performance status of 0 or 1.
  * Life expectancy \> 12 weeks.
  * Female participants should agree to use medically acceptable contraceptive measures should not be breastfeeding, and must have a negative pregnancy test before the start of study drug administration if of childbearing potential.
  * Female participants of childbearing potential must understand and accept that pregnancy must be avoided during participation in the study, from screening through 90 days after the last dose of study drug.

Male participants should avoid unprotected sex with women of childbearing potential during the study and for a washout period of 90 days after the last dose of study drug.

* For participants who will be enrolled in the study and receive the RP2D of INCB086550 in the expanded cohort: Willingness to undergo a tumor biopsy to obtain tumor tissue. Pretreatment and on-treatment tumor biopsies are required.

Exclusion Criteria:

* Laboratory values not within the Protocol-defined range.
* Clinically significant cardiac disease, including left ventricular ejection fraction \< 40%, unstable angina, acute myocardial infarction within 6 months of Cycle 1 Day 1, New York Heart Association Class III or IV congestive heart failure, and arrhythmia requiring therapy.
* History or presence of abnormal ECG that, in the investigator's opinion, is clinically meaningful.
* Untreated brain or CNS metastases or brain or CNS metastases that have progressed (eg, evidence of new or enlarging brain metastasis or new neurologic symptoms attributable to brain or CNS metastases).
* Active or inactive autoimmune disease or syndrome (eg, rheumatoid arthritis, moderate or severe psoriasis, multiple sclerosis, inflammatory bowel disease) that has required systemic treatment in the past 2 years or receiving systemic therapy for an autoimmune or inflammatory disease (ie, with use of disease-modifying agents, corticosteroids, or immunosuppressive drugs).
* Diagnosis of immunodeficiency or receiving chronic systemic steroid therapy (doses exceeding 10 mg daily of prednisolone equivalent) or any other form of immunosuppressive therapy within 7 days before the first dose of study drug. Use of short courses of steroids for procedure prophylaxis, inhaled or topical steroids, or systemic corticosteroids ≤ 10 mg is permitted.
* Known additional malignancy that is progressing or requires active treatment.
* Evidence or a history of interstitial lung disease or active, noninfectious pneumonitis.
* Treatment with anticancer medications or investigational drugs is prohibited within the following intervals before the first administration of study drug.
* Concomitant treatment with moderate and potent CYP3A4/CYP3A5 inhibitors or inducers.
* Receipt of a live vaccine within 3 months of the first dose of study drug.
* Active infection requiring systemic therapy.
* Systemic antibiotic therapy. A washout of 28 days is required before the first dose of INCB086550.
* Probiotic supplement usage during screening and throughout the study treatment period.
* Known active HBV or HCV infection or risk of reactivation of HBV or HCV.
* History of organ transplant, including allogeneic stem cell transplantation.
* Known hypersensitivity or severe reaction to any component of study drug or formulation components.
* Inability to swallow food or any condition of the upper gastrointestinal tract that precludes administration of oral medications.
* Any condition that would, in the investigator's judgment, interfere with full participation in the study, including administration of study drug and attending required study visits; pose a significant risk to the participant; or interfere with interpretation of study data.
* Inability or unlikeliness of the participant to comply with the dose schedule and study evaluations, in the opinion of the investigator.
* Inadequate recovery from toxicity and/or complications from a major surgery before starting therapy.
* Women who are pregnant or breastfeeding.
* Inability of the participant (or parent, guardian, or legally authorized representative) to comprehend the ICF or unwillingness to sign the ICF.