O-12 : Switching from Tenofovir Disoproxil Fumarate (TDF) to Tenofovir Alafenamide (TAF) in Virally Suppressed Chronic Hepatitis B (CHB) Patients with Moderate or Severe Renal Impairment, or in End-Stage Renal Disease (ESRD) Patients on Hemodialysis (HD): Week 2

Aims: TAF, a novel tenofovir prodrug, has demonstrated noninferior efficacy to TDF with superior bone and renal safety in virally suppressed CHB patients with eGFR (by Cockcroft-Gault; eGFRCG) ³50 mL/min when switched from TDF. The efficacy and safety of virally suppressed patients on TDF with renal impairment who were switched to TAF were evaluated in this Phase 2 study. Methods: CHB patients with renal impairment taking TDF for ³48 weeks and virally suppressed for ³6 months with HBV DNA <20 IU/mL at screening were enrolled into 2 cohorts: 1) moderate-severe renal impairment (eGFRCG 15 to <60mL/min) and 2) ESRD (eGFRCG <15 mL/min) patients on chronic HD. All patients were switched to TAF 25 mg QD for 96 weeks. Co-primary endpoints were proportion with HBV DNA <20 IU/mL and graded adverse events (AEs)/lab abnormalities at Week 24. Results: 93 patients (Mod-severe impairment 78; ESRD 15) were enrolled from 26 sites in 8 countries. Median age was 65 years, 74% male, 77% Asian, 83% HBeAg-negative, up to 60% had low BMD at hip and/or spine, and 60% and 24% had a history of HTN and/or diabetes, respectively. Key efficacy/safety results at Week 24 are summarized in the Table. All patients on treatment at Week 24 maintained HBV DNA <20 IU/mL and a high proportion had normal ALT levels. Relative to baseline levels, switching to TAF from TDF resulted in increases in hip/spine BMD, decreases in bone turnover markers, as well as increases in eGFRCG and decreases in renal tubular markers. TAF was well tolerated with few having Grade 3 or 4 AEs (8%) and no discontinuations due to AEs. Conclusions: In renally-impaired CHB patients, including ESRD patients on HD, viral suppression was well maintained and the bone and renal safety were improved 24 weeks after switching from TDF to TAF.