- Patients who are pregnant or adults of reproductive potential not employing an effective method of birth control (women of childbearing potential must have a negative serum pregnancy test within 48 hrs prior to administration of Clofarabine-Cyclophosphamide). Post menopausal women must be amenorrheic for at least 12 months to be considered of non-childbearing potential. Male and female patients must agree to employ an effective barrier method of birth control throughout the study and for up to 3 months following discontinuation of study drugs.