Synthesis and Biologic Evaluation of an Iodine-Labeled Entecavir Derivative for Anti-hepatitis B Virus Activity

Purpose To label entecavir (ETV) with radioiodine and evaluate its effect on inhibiting hepatitis B virus (HBV) secretionand replication in vitro as well as its biodistribution in BALB/c mice. Methods 125I-ETV was synthesized via binding a vinyl tributyltin group to ETV and producing electrophilic iodination of thegroup. Its chemical properties were assessed using traditional methods. Upon intravenous injection of 125I-ETV into BALB/cmice, the radioactivity of the critical organs was detected. In vitro, the anti-HBV activity of 125I-ETV was investigated usingHepG2.2.15 cell culture model. Confocal microscopy was used to analyze the cell apoptosis. Culture supernatant sampleswere used for measuring HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) by enzyme-linked immunosorbentassay. Intracellular HBV pregenomic RNA (pgRNA), DNA, and covalently closed circular DNA (cccDNA) were measuredby real-time fluorescence quantitative PCR. Results The radiochemical purity of 125I-ETV was greater than 95% after incubation in freshly serum within 48 h. The threehighest radioactivities were in the stomach, intestine, and liver after intravenous injection at 0.5 h, 2 h, and 24 h. The confocalfluorescence imaging showed that 125I-ETV did not induce cell apoptosis after treatment for 96 h. 125I-ETV decreasesHBsAg and HBeAg secretions as well as intracellular HBV pgRNA, DNA, and cccDNA copies in a dose-dependent manner. Moreover, the anti-HBV activity of 125I-ETV is greater than that of ETV. Conclusions The study outcome establishes 125I-ETV as a candidate for anti-HBV. However, it is still in need of furtherendorsement and optimization by animal model studies before using 125I-ETV to treat chronic HBV disease.