Aims: TAF, a novel tenofovir (TFV) prodrug, has greater plasma stability, more targeted delivery of TFV to hepatocytes, and reduced circulating levels of TFV compared to TDF. We evaluated efficacy and safety when virally suppressed CHB (Chronic Hepatitis B) patients with hepatic impairment were switched to TAF. Methods: In this Phase 2 study (NCT03180619) CHB patients with a ChildTurcottePugh (CTP) score of ³7 and £12 at screening (or past history of CTP ³7 and any score £12 at screening) who were taking TDF and/or other OAVs for ³48 weeks, with HBV DNA CG 98 mL/min; up to 48% had low BMD at hip and/or spine, and 68% had prior TDF exposure. Key efficacy/safety results at Week 24 are summarized in the Table. All patients had HBV DNA <20 IU/mL and a high proportion had normal ALT. Switching to TAF resulted in increases in hip/spine BMD, decreases in bone turnover markers, an increase in eGFR_CG with decreases in tubular markers. TAF was well tolerated with few having Grade 3 or 4 AEs (2 patients) and no discontinuations for and AE. ^aHBV DNA results are missing=failure. ^bALT normal is the proportion with ALT ≤ULN at Week 48, regardless of baseline ALT level; ^cULN 35 U/L males, 25 U/L females; ^dPatients with ALT >ULN at baseline; ^eHBeAg-positive at baseline. ^fSerum C-type collagen sequence (bone resorption marker); ^gSerum procollagen type 1 N-terminal propeptide (bone formation marker); ^hUrine retinol binding protein/creatinine (tubular marker); ⁱUrine beta-2 microglobulin/creatinine (tubular marker). BMD, bone mineral density by DXA scan; sCr, serum creatinine; PO₄, serum phosphorus; eGFR_CG, estimated creatinine clearance (Cockcroft-Gault method) Conclusions: In CHB patients with hepatic impairment switched to TAF from TDF or other OAVs, viral suppression was well maintained and improved bone and renal safety was seen at Week 24.