A Phase II Study of Eribulin and Pembrolizumab in Soft Tissue Sarcomas

Inclusion Criteria: * Histologically confirmed liposarcoma, leiomyosarcoma, or undifferentiated/unclassified pleomorphic sarcoma by a Dana-Farber Cancer Institute or Massachusetts General Hospital pathologist * Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as ≥20 mm with conventional techniques or as ≥10 mm with spiral CT scan, MRI, or calipers by clinical exam. See Section 11 for the evaluation of measurable disease. * Participants must have received at least one prior line of chemotherapy. No limit on prior lines of therapy. * Age ≥ 18 years. * ECOG performance status of 0 or 1 (see Appendix A). * Participants must have normal organ and marrow function as defined below: * leukocytes ≥3,000/mcL * absolute neutrophil count ≥1,500/mcL * platelets ≥100,000/mcL * Hemoglobin ≥ 8 g/dL within the first 2 weeks prior to the first dose of study drugs, transfusion is allowed. * total bilirubin ≤1.5× institutional upper limit of normal (ULN) (except participants with Gilbert Syndrome, who can have total bilirubin \<3.0 mg/dL) * AST(SGOT)/ALT(SGPT)\<2.5 x ULN in a participant with no documented liver metastases; ALT and AST \<5.0 x ULN in a participant with documented liver metastases * creatinine ≤1.5× ULN OR * creatinine clearance ≥50 mL/min/1.73 m2 for participants with creatinine levels above …