A Study of INCB059872 in Relapsed or Refractory Ewing Sarcoma

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of Ewing sarcoma and have progressed on or after standard therapies. * Must not be a candidate for potentially curative therapy or standard-of-care approved therapy. * Measurable disease by computed tomography or magnetic resonance imaging based on RECIST 1.1 as determined by site radiology. * Eastern Cooperative Oncology Group performance status 0 to 2. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Receipt of anticancer medications, anticancer therapies, or investigational drugs within protocol-defined intervals before the first administration of study drug. * Must have recovered (≤ Grade 2 or at pretreatment baseline) from adverse events (AEs) from previously administered therapies except for stable chronic toxicities (≤ Grade 2) not expected to resolve. * Untreated brain or central nervous system (CNS) metastases or brain/CNS metastases that have progressed. * Prior radiotherapy within 2 weeks of study treatment. A 1-week washout period is permitted for palliative radiation to non-CNS disease with medical monitor approval. * Laboratory values outside the protocol-defined range at screening. * History or evidence of bleeding disorder or active clinically significant bleeding requiring medical intervention.