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.