Adefovir Dipivoxil 10mg (ADV) Resistance at 5 yrs in Chinese HBeAg+ve Chronic Hepatitis B (CHB) J.L. Hou 1 , Y.Z. Wang 2 , X.Q. Zhou 3 , J.Q. Niu 4 , Y.M. Wang 5 , H. Wang 6 , Y.M. Mao 7 , K.F. Barker 8 1 NanFang Hospital, Guangzhou, PRC, 2 JiNan Infectious Disease Hospital, JiNan, PRC, 3 Ruijin Hospital, Shanghai, PRC, 4 1st Hospital of Jilin University, Changchun, PRC, 5 Xinan Hospital, Chongqing, PRC, 6 People's Hospital, Beijing, PRC, 7 Renji Hospital, Shanghai, PRC, 8 GlaxoSmithKine R&D, London, UK Background: Long term ADV provides clinical and histological improvement in CHB, but may lead to emergence of treatment associated resistant mutations. We report on ADV resistance data from Chinese HBeAg positive subjects treated for 5 years. Methods: 480 HBeAg positive CHB subjects were randomized in an initial 52 weeks controlled ADV study (with a 12 weeks placebo period in half of patients) and then offered open label ADV treatment for a further 208 weeks. A total of 474, 456, 443, 421 and 390 subjects completed the 1 st , 2 nd , 3 rd ,4 th and 5 th yr, respectively. At the end of each year samples were analysed from those subjects with protocol-defined HBV DNA breakthrough for the rtN236T or rtA181V ADV mutations associated with resistance. Sera from subjects with breakthrough were analysed at all subsequent yearly timepoints whenever possible. Results: At the end of the 1 st yr, none of the 45 subjects with HBV DNA breakthrough had either mutation. Sera were available for analysis from 137, 199, 228 and 187 subjects with viral breakthrough at the end of the 2 nd , 3 rd , 4 th and 5 th yr, respectively, with new mutations identified in 6, 20, 24 and 20 subjects at the same timepoints. Of the cumulative 70 subjects at the 5 th yr analysis 31 had rtN236T, 29 had rtA181V, and 10 had both mutations. Conclusion: Treatment with ADV in Chinese HBeAg positive CHB subjects for up to 5yrs resulted in a cumulative rate of 14.6% (70/480) ADV resistance-associated mutations with HBV DNA breakthrough. Background and aims: To evaluate the predictive significance of rapid virologic response (RVR) for achieving an end-of-treatment virologic response (ER) or HBeAg seroconvertion and the predicting indicator of nonresponse (NR). Methods: 205 patients with chronic hepatitis B were treated with ADV and prospectively observed to 48 weeks. We assessed the values of virus load reduction at weeks 4, 8, and 12 weeks to predict the ER and HBeAg seroconversion. The association between less reduction of viral load at 12 and 24 weeks and nonresponse was also analyzed.