Four patients are entered at each dose level starting with level 1. Patients are not entered into the next higher dose level until at least two patients at the previous dose level have completed at least 3 weeks of therapy with grade 2 or less maximum tolerated dose-defining toxicities. Treatment is repeated weekly for 52 weeks until either a grade 3 or 4 toxicity occurs, or until a patient shows a complete response or progressive disease. Patients with a complete response are continued on drug for 4 additional weeks from the time that complete response is first documented. Patients with progressive disease are withdrawn from study. Patients with partial response or stable disease continue until either unacceptable toxicity occurs or a complete response or progression of disease is reached.