12. Females of childbearing potential (non childbearing is defined as greater than one year post-menopausal or surgically sterilized) must use acceptable contraceptive methods (abstinence, intrauterine device, oral contraceptive or double barrier device), and must have a negative serum or urine pregnancy test within 7 days prior to beginning treatment on this trial. Sexually active men must also use acceptable contraceptive methods for the duration of time on study.