6. Sexually active female patients of childbearing potential and sexually active male patients must agree to use an effective method of birth control (e.g., barrier methods with spermicides, oral or parenteral contraceptives and/or intrauterine devices) during the entire duration of the study and for 4 months after final administration of study drug. Note that sterility in female patients must be confirmed in the patients' medical records and be defined as any of the following: surgical hysterectomy with bilateral oophorectomy, bilateral tubular ligation, natural menopause with last menses >1 year ago; radiation induced oophorectomy with last menses >1 year ago; chemotherapy induced menopause with last menses >1 year ago.