HBF-0259 is an inhibitors of hepatitis B virus surface antigen (HBsAg) secretion with an EC50 of 11.3 μM and a CC50 value of >50 μM in HepG2.2.15 cells. HBF-0259 had a EC50 of approximately 1.5 microM in a secondary, HBV-expressing cell line, with a concentration that exhibited 50% cytotoxicity of >50 microM. The equilibrium concentration of HBF-0259 in aqueous solution at physiological pH was 15 to 16 microM; the selective index was thus >9.