In vitro and in vivo comparison of the abilities of purine and pyrimidine 2',3'-dideoxynucleosides to inhibit duck hepadnavirus.

Four purine and two pyrimidine 2',3'-dideoxynucleosides were studied for their ability to inhibit duck hepadnavirus replication. The purine 2',3'-dideoxynucleosides were more potent antiviral agents than the pyrimidine 2',3'-dideoxynucleosides. The concentration for 50% inhibition of viral replication (IC50) was determined for each of the effective agents. Two drugs with low IC50s, 2,6-diaminopurine 2',3'-dideoxyriboside and 2',3'-dideoxyadenosine, were chosen for in vivo studies. Animals received 10 mg/kg intramuscularly twice daily. Rapid clearance of hepadnavirus DNA from the sera of the animals was seen as a result of treatment with 2,6-diaminopurine 2',3'-dideoxyriboside; however, treatment with 2',3'-dideoxyadenosine did not clear the virus.