The dose escalation will follow the widely used 3+3 design. Cohorts of 3-6 subjects will be enrolled sequentially at escalating doses of 1.0, 2.5, 5.0 and 10 mg/kg weekly. Dose escalation will continue until identification of MTD up to a maximum dose of 10 mg/kg. MTD is defined as the highest dose studied at which no more than 1 of 6 subjects has experienced a dose-limiting toxicity (DLT) in Cycle 1. The enrolled patients are managed under hospitalization for DLT observation period (C1 28 days). If no DLTs occur in a cohort of 3 subjects, a new cohort of 3 subjects will be treated at the next higher dose level. If 1 of 3 subjects in a cohort experiences a DLT, that cohort will be expanded to 6 subjects. If only 1 of the 6 subjects has a DLT, then the next cohort of 3 subjects will be treated at the next higher dose level. If 2 or more DLTs occur within a cohort, then that dose level will be above the MTD, and the previous lower (tolerated) dose level will be considered the MTD if ≤ 1 in 6 subjects has a DLT.