OUTLINE: This is a dose escalation, open label, multicenter study. Patients receive PNU 166148 IV over 30 minutes. Treatment repeats every 4 weeks for 3-6 courses in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of PNU 166148 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which at least 2 of 3-6 patients experience dose limiting toxicity. Patients are followed for 30 days, and then monthly thereafter only for resolution of adverse events that occurred while on study and were attributable to study drug, unless another antitumor treatment is begun.