Subjects in this study enter one of two schedules: Schedule 1 or Schedule 2. Schedule 1 is a sequential dose escalation study which consists of Parts A and B. Part A is the initial treatment phase, where the clinically effective dose (CED) of NESP administered every 3 weeks will be determined after 12 weeks of treatment. Part B is an optional 12-week, open-label, dose-maintenance phase that follows Part A.