After the first loading dose, you will continue to receive the study drug as a single, 3-hour infusion 1 time each week (this is called a maintenance dose). Maintenance doses will be given on Days 8, 15, and 22 as a single, 3-hour infusion. Days 8-28 will be defined as Cycle 2. All cycles beginning with Cycle 3 will be 28 days. In this study, different participants will receive different dose levels.