5,6-Dihydro-5-azathymidine: in vitro antiviral properties against human herpesviruses

5,6-Dihydro-5-azathymidine (DHAdT), a novel water-soluble nucleoside antibiotic, inhibits herpes simplex virus type 1 (HSV-1) in appropriately infected cell cultures to a greater extent than herpes simplex virus type 2 (HSV-2). Vaccinia virus was less susceptible than HSV-2, and pseudorabies virus yields were not reduced at the concentrations studied. Plaque formation by varicella-zoster virus was suppressed by DHAdT. DHAdT was slightly toxic to cells at concentrations that were inhibitory for HSV-1 and varicella-zoster virus. Thymidine and deoxyuridine completely reversed the anti-HSV-1 activity of DHAdT, whereas deoxycytidine was partially effective. Compared with other nucleoside analogs with activity for HSV-1, DHAdT was less active than 5-iodo-2'-deoxyuridine or 1-beta-d-arabinofuranosylcytosine and nearly equipotent with 9-beta-d-arabinofuranosyladenine.