Safety and Efficacy Study of ARQ 501 in Adult Patients With Leiomyosarcoma

Inclusion Criteria: * Able to provide signed and dated informed consent prior to study-specific screening procedures. * Histologically or cytologically confirmed leiomyosarcoma that is persistent, recurrent or metastatic. * Measurable disease as defined by RECIST. * Karnofsky performance status \>= 70% * Male or female patients of child-producing potential must agree to use contraception or avoidance of pregnancy measures during the study and for 30 days after the last infusion of ARQ 501. * Hemoglobin (Hgb) \>= 10 g/dL. * Absolute neutrophil count (ANC) \>= 1.5 x 10\^9/L (\>= 1,500/mm3). * Platelet count \>= 100 x 10\^9/L (\>= 100,000/mm3). * Total bilirubin less than or equal to 1.5 x upper limit of normal (ULN) or less than or equal to 3.0 x ULN with metastatic liver disease. * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) less than or equal to 2.5 x ULN less than or equal to 5.0 ULN with metastatic liver disease. * Creatinine less than or equal to 1.5 x ULN. Exclusion Criteria: * Received three or more prior anticancer chemotherapy regimens. * Have active, uncontrolled systemic infection considered opportunistic, life threatening or clinically significant at the time of treatment. * Have received anticancer chemotherapy, immunotherapy, radiotherapy, surgery or investigational agents within four weeks of first infusion. * Have symptomatic or untreated central nervous system (CNS) involvement. * Are pregnant or breastfeeding. * Previous exposure to ARQ 501.