 Participants will take GW572016 by mouth daily each cycle cycles 28 days in length and will be given Topotecan intravenously on Days 1, 8 and 15. During Cycle 1 participants will be required to spend the evening before Day 1 in the General Clinical Research Center and frequent blood samples will be drawn on Day 1; this schedule will be repeated the evening of Day 6 with the blood samples drawn on Day 7. Participants will have weekly CBCs. 