4. Women of childbearing potential and sexually active males must be willing to use contraception, as indicated in Section 6 of the protocol. Subjects who are not of reproductive potential (status post bilateral tubal ligation, bilateral oophorectomy, hysterectomy, or vasectomy), not sexually active, whose current partner(s) is not of reproductive potential, or whose sexual activity is exclusively homosexual are eligible without requiring the use of contraception.