The starting dose of 1.2 mg/m2 once every 3 weeks is expected to ensure a safe first-in-human dose and allow increases of 50% with the first several subject cohorts. The first cohort will enroll 3 subjects, and the subsequent 3-subject cohorts will proceed according to a modified Fibonacci scheme. The standard dose increase, in the absence of dose limiting toxicity, will be 50%. However, once 1 subject experiences a DLT, or 2 or more subjects within a cohort experience ≥ Grade 2 drug-related adverse events, all subsequent dose escalations will occur at approximately 25% increments. In the case that the dose escalation increment is decreased to 25% following 2 or more subjects with ≥ Grade 2 drug-related events, the increment can subsequently be reset at 50% if, in the 2 successive cohorts, no DLTs are observed, and no more than 1 subject per cohort experiences a ≥ Grade 2 drug-related AE. DLT and MTD determinations will be made according to the first treatment cycle (single dose plus 3-week follow-up). The MTD will be declared as the highest level at which none of the original 3 subjects or no more than 1 of the expanded 6-subject cohort experiences a DLT. At the MTD level, subjects will be enrolled into two parallel groups: Group A, those with solid tumor of unrestricted tumor type, and Group B, those with primary tumor type of soft tissue sarcoma. Up to a total of 24 subjects will be enrolled at the MTD.