23. Female patients of childbearing potential are not willing to use highly effective contraception to prevent pregnancy or agree to abstain from heterosexual activity throughout the study. Highly effective contraception is defined as 1) Surgical birth control/sterilization (such as male vasectomy or female sterilization; 2) Birth control pills, injections, implants, or patches; 3) Intrauterine devices (IUDs); 4) Two barrier methods (male condom and female diaphragm, cervical cap, or sponge) in combination with a spermicide.