5. Age >= 18 years old. (Females must be either post-menopausal >12 months, practicing a protocol-acceptable method of birth control [defined as injectable or implantable hormonal contraceptives, oral contraceptives, intrauterine device, diaphragm plus spermicide], or have had a hysterectomy, bilateral oophorectomy, or tubal ligation performed at least 6 months prior to enrollment).