Low HBsAg (N=61) High HBsAg (N=61) Adjusted p-value a aAdjusted by Hochberg’s procedure a-determinant Disclosures: Kathryn M. Kitrinos – Employment: Gilead Sciences, Gilead Sciences; Stock Shareholder: Gilead Sciences, Gilead

Sciences Henry Lik-Yuen Chan – Advisory Committees or Review Panels: Gilead, Vertex, Bristol-Myers Squibb, Abbott, Novartis Pharmaceutical, Roche, MSD Edward J. Gane – Advisory Committees or Review Panels: Roche, AbbVie, Novartis, Tibotec, Gilead Sciences, Janssen Cilag, Vertex, Achillion; Speaking and Teaching: Novartis, Gilead Sciences, Roche Scott Fung – Advisory Committees or Review Panels: Merck, Vertex; Grant/Research Support: Gilead Sciences, NVP-AUY922 Roche; Speaking and Teaching: Gilead Sciences,

BMS Phillip Dinh – Employment: Gilead Sciences Lanjia Lin – Employment: Gilead; Stock Shareholder: Gilead Amoreena C. Corsa – Employment: Gilead Sciences Inc.; Stock Shareholder: Gilead Sciences Inc. Michael D. Miller – Employment: Gilead Sciences, Inc.; Stock Shareholder: Gilead Sciences, Inc. Mani Subramanian – Employment: Gilead Sciences Alexander J. Thompson – Advisory Committees or Review Panels: Merck, Inc, Roche, Janssen (Johnson & Johnson), BMS, GSK Australia, Novartis, GILEAD Sciences, Inc; Consulting: GILEAD Sciences, Inc; Grant/Research Support: Merck, Inc, Roche, GILEAD Sciences, Inc; Speaking and Teaching: Y-27632 cell line Merck, Inc, Roche, BMS Maria Buti – Advisory Committees or Review Panels: Boerhinger Inghelm, Boer-hinger Inghelm; Speaking and Teaching: MSD, Bristol-Myers Squibb, Novartis, Gilead, Janssen, MSD, Bristol-Myers Squibb, Novartis, Gilead, Janssen Background The HBV X region (HBX) overlapped with preCore, includes essential BCP motifs: TATA boxes TA1-TA4 MCE and the conserved DR1 motif with the target sequence (AS) for the 4-nucleotide primer (4nt) that starts HBV replication Aim To characterize

HBV quasispecies complexity in HBX, TA1-TA4, and DR1 by UDPS Patients and Methods UDPS (GS Junior Roche) analysis of HBX from 10 chronic HBV patients, all LMV nonresponders, in 30 serum samples: baseline (BA), untreated (UT), and after LMV. nt variations were studied. Quasispecies complexity was estimated by Shannon entropy (SE), mutation frequency, and nucleotide diversity (ND) Results UDPS yielded 415,726 sequences. TA1, TA2 and DR1 were more variable than TA3 or TA4 (Table). TA1 and TA2 variability was mainly due to T1753C and T1762A, respectively. In 6 patients, there was no identity between 4nt and AS (Table). Without treatment (BA/UT), quasispecies complexity was higher in HBeAg(-) than HBeAg(+) cases (SE 0.55 vs 0.35, p=0.029); after LMV it was greater in HBeAg(+) than HBeAg(-) (SE 0.38 vs 0.21, p=0.007), and near significantly greater in genotype A than D (ND 0.016 vs 0.01, p=0.