8. Pregnant women are excluded from this study. Women of child-bearing potential and men must agree to use contraception prior to study entry and for the duration of study participation. Acceptable forms of birth control include: Birth control pills plus a barrier method, such as a condom or diaphragm, Intrauterine devices (IUD) plus a barrier method, Implantable or injectable birth control (such as NorplantR or epo-ProveraR) started at least 3 months before joining the study, plus a barrier method, or Double-barrier method, such as a condom when used in combination with a diaphragm. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician.