- Reduced-intensity conditioning regimen: Patients receive busulfan IV over 6 hours on days -7 and -6, fludarabine phosphate IV over 30 minutes on days -7 to -2, anti-thymocyte globulin (ATG) IV over 4 hours on days -4 to -1, and methylprednisolone IV over 30 minutes on days -4 to -1.