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.