A Study of Epacadostat, an IDO1 Inhibitor, in Combination With Pembrolizumab in Patients With Metastatic and/or Locally Advanced Sarcoma

Inclusion Criteria: * Male or female age ≥ 18 years at the time of informed consent * Be willing and able to provide written informed consent/assent for the trial * Be willing to comply with treatment protocol * Subjects must have a histologically confirmed metastatic and/or locally advanced sarcoma * Adequate performance status: ECOG 0 or 1/KPS 100-70% * Subjects must have at least one prior line of systemic therapy (e.g. chemotherapy, immunotherapy, targeted or biological therapy) for their sarcoma. An exception to this criterion will be made for patients with sarcoma histological subtypes for which there is no known standard systemic therapy (e.g., chondrosarcoma). Any patient that refuses standard chemotherapy for the treatment of their disease is also considered eligible. Prior adjuvant therapy will not count provided it was completed more than 6 months previously. * Presence of measureable disease per RECIST v1.1.Target lesions must not be chosen from a previously irradiated field unless there has been radiographically and/or pathologically documented tumor progression in that lesion prior to enrollment. * All subjects must agree to pre-treatment tumor biopsy. Subjects in whom biopsy is technically not feasible or in whom would result in unacceptable risk, in the opinion of the investigator, may be exempted from the biopsy requirement with discussion with the principal investigator. * Adequate organ function determined within 21 days of treatment initiation * Hematolog…