AVI-4020 Injection, a phosphorodiamidate Morpholino oligomer (PMO), was found to cross the blood-brain barrier during a study of patients with presumptive West Nile virus disease. AVI-4065, which was designed to target HCV, is also a PMO; its ability to cross the blood-brain barrier is unknown. As the incidence of HCV disease has grown, the knowledge base of this disease has likewise increased.