Dose escalation will be continued until more than one-third of the patients in a given cohort show dose-limiting toxicity (DLT) during treatment cycle 1. At least three patients will be enrolled in each cohort. Before escalating to the next dose level, all three patients should have received at least one treatment cycle. If none of the first three treated patients develops DLT in the first cycle at a specific dose level, dose escalation will be continued. If one of the first three treated patients develops DLT at any dose level, then three additional patients are to be entered on the same dose level. If only one in six patients at a given level experiences a DLT, escalation will proceed. The MTD is defined as the dose level at which at least one-third of patients experienced a DLT. The RD for the subsequent phase II study is defined as the preceding dose level before the MTD is attained. Intra-patient dose escalation will not be permitted. Treatment will be continued in the absence of disease progression or unacceptable toxicity with maximum 12 cycles. For purpose of determining the MTD, only DLT occurring during the first cycle of therapy will be considered.