“…Attempts in the early 1980 s to block HBV replication using inhibitors of viral DNA synthesis were generally unsuccessful because of the poor efficacy and/or toxicity of available drugs, for example, as found with adenosine arabinoside [8][9][10][11][12][13][14][15]. Moreover, with the lack at that time of tissue culture and in vitro systems for virus growth or viral polymerase expression, which were suitable for high throughput screening, antiviral compound libraries could not be tested against HBV.…”