In contrast, specific regions across the HBx gene and precore that encode non structural regulatory or signaling elements, generally displayed higher viral diversity within HBsAg loss subjects compared to buy CH5424802 controls. These distinct patterns may reflect different mechanisms

by which coding regions for structural or nonstructural elements respond to adaptive pressure resulting in the common endpoint of HBsAg loss. Disclosures: Kathryn M. Kitrinos – Employment: Gilead Sciences, Gilead Sciences; Stock Shareholder: Gilead Sciences, Gilead Sciences Paul N. Hengen – Employment: Gilead Sciences Raul E. Aguilar Schall – Employment: Gilead Sciences, Inc. Phillip Dinh – Employment: Gilead Sciences Hendrik W. Reesink – Consulting: Abbott, Gilead, Astex, Merck, Roche, Janssen Cilag, GlaxoSmithKline, Tibotec/JJ, PRA-International; Grant/Research Support: Vertex, Boehringer Ingelheim, Anadys, Phenomix, Chugai, Japan Tobacco, Santaris, SGS, Idenix, BMS Fabien Zoulim – Advisory Committees or Review Panels: Gilead; Consulting: Roche; Grant/Research Support: Gilead, Scynexis, Roche; Speaking and Teaching:

Novartis, Roche, Janssen, Bristol Myers Squibb, Gilead Prista Charuworn – Employment: Gilead Sciences; Stock Shareholder: Gilead Sciences Background: During treatment with highly potent nucleo(s)tide analogues serum HBV DNA levels become suppressed to undetectable levels during the first treatment year in most patients and HBV genome analysis becomes infeasible. However, HBV RNA remains detectable in serum in many patients with undetectable HBV DNA. We have investigated Y-27632 the evolution of HBV variants by sequence analysis of serum HBV RNA in patients with HBV resistance mutations who were achieving undetectable HBV DNA levels during consecutive treatment with tenofovir (TDF). Methods: Nineteen patients who received monotherapy with TDF 245 mg/day for a mean of 40±14 (range, 21-76) months after prior treatment failure to lamivu-dine (n=4), adefovir (n=1) or both (n=14) were retrospectively analyzed. Sixteen patients were male, 16 HBeAg positive, the mean HBV DNA was 6.3±1.5 (3.8-9.6)

log 10 copies/mL and HBV genotypes A, B, D and E were present in 3,2, 13 and 1 patient, respectively. From serum samples stored at -20°C representing the start of TDF treatment GPX6 and consecutive time points HBV DNA was amplified by a real time PCR targeting the HBV core region and HBV RNA after reverse transcription by a real time PCR targeting the x gene with HBV RNA specific RACE primers (minimal detectable quantity was 100 and 500 copies/mL, respectively). The rt region and the overlapping s gene of HBV were sequenced in all samples with HBV DNA or HBV RNA levels > 1000 copies/mL (n=103). Results: During TDF treatment HBV DNA decreased to levels < 1000 and < 100 copies/mL after a mean duration of 13±8 (3-32) and 34±14 (3-76) months, respectively.