- Therapy with any systemic anti-viral, anti-neoplastic or immunomodulatory treatment greater than or equal to6 months prior to the first dose of study drug, except PEG-IFN alfa-2b and ribavirin. This includes amantadine, mycophenolate mofetil, thymosine alpha, viramidine, levovirin, supraphysiologic doses of steroids (greater than or equal to 10 mg/d for greater than or equal to 14 consecutive days of prednisone or equivalence) and radiation, exception: patients who have had a limited (greater than or equal to 7 day) course of acyclovir or valacyclovir for herpetic lesions more than 1 month prior to the first administration of test drug are not excluded.