S1126 Safety and Efficacy of Switching to Tenofovir Alafenamide (TAF) in Virally Suppressed Chronic Hepatitis B (CHB) Patients With Hepatic Impairment: Week 48 Results From a Phase 2 Open Label Study

INTRODUCTION: Switching to TAF, a novel tenofovir prodrug, has shown maintenance of viral suppression with stable or improved bone and renal safety at Week 24 in CHB patients with impaired hepatic function. Here we evaluated the efficacy and safety 48 weeks after CHB patients with hepatic decompensation were switched to TAF. METHODS: In this Phase 2 study (NCT03180619) patients with CHB having a Child-Turcotte-Pugh (CTP) score ≥ 7 and ≤ 12 at screening, or by documented history, receiving TDF and/or other OAVs for ≥ 48 weeks, with HBV DNA < LLOQ for ≥ 24 weeks and < 20 IU/mL at screening were eligible to participate. All patients were switched to TAF 25 mg QD and were to be treated for 96 weeks. Safety assessments including changes in bone (hip and spine BMD) and renal (CrCl by Cockcroft-Gault [eGFRCG], serum creatinine) parameters, viral suppression, and biochemical responses were assessed at Week 48. RESULTS: 31 patients were enrolled at 18 sites in 7 countries and 90% completed 48 weeks of treatment. At baseline, 74% were ≥ 50 y, 68% male, 81% Asian, 90% HBeAg-negative, with median fibrotest (FT) score 0.81, median CTP and MELD scores of 6 and 10, respectively, median eGFRCG 98 mL/min, and 19% and had osteoporosis by T score at spine. Prior use of TDF and entecavir was reported by 68% and 45%, respectively. Key efficacy/safety results at Week 48 are summarized in the Table. By missing equals failure analysis, 31 patients (100%) had HBV DNA < 20 IU/mL, 81% had normal ALT and CTP/MELD scores were stable. After switching to TAF in this population with liver impairment, CTP, MELD, and FT scores were unchanged while bone and renal parameters were stable. TAF was well tolerated with few having Grade 3 or 4 AEs (4 patients); no serious AEs related to study drug, and 1 patient who discontinued for worsening renal function unrelated to TAF. CONCLUSION: CHB patients with hepatic impairment who were switched to TAF from TDF or other OAV showed high rates of viral suppression, normal ALT and bone and renal safety were stable at Week 48.Table 1.: Efficacy and Safety Results at Week 48

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