A hemophilia A dog model was used to evaluate changes affecting the liver and factors affecting FVIII expression following AAV gene therapy. Five male dogs were treated with a single infusion of AAV5-HLP-cFVIII at doses of 6.8e13–2e14 vector genomes/kg. FVIII expression was seen for the 2 dogs treated with codon-optimized constructs (JA2013 and K2015), which was sustained at six months (co-cFVIII-SQ = 6.8% and co-cFVIII-V3 = 4.3%) with normalization of the whole blood clotting time (WBCT).