Entecavir for treatment of hepatitis B virus displays no in vitro mitochondrial toxicity or DNA polymerase gamma inhibition.
Therapy with nucleoside reverse transcriptase inhibitors (NRTIs) can be associated with mitochondrial toxicity. In vitro studies have been used to predict the predisposition for and characterize the mechanisms causing mitochondrial toxicity. Entecavir (ETV) is an approved deoxyguanosine nucleoside for the treatment of chronic hepatitis B virus (HBV) infection that exhibits potent activity against viral reverse transcriptase. We assessed the potential for mitochondrial toxicity of ETV in long-term cultures of HepG2 hepatoma cells by measuring mitochondrial function (through lactate secretion), levels of mitochondrial DNA (mtDNA), and levels of mitochondrial proteins COX II and COX IV. Furthermore, we tested the activity of ETV-triphosphate (ETV-TP) against mitochondrial DNA polymerase gamma (Pol gamma) in vitro. ETV concentrations as high as 100 times the maximal clinical exposure (C(max)) did not affect cell proliferation, levels of lactate, mitochondrial DNA, or mitochondrial proteins throughout the 15-day culture. The lack of mitochondrial toxicity was consistent with the finding that ETV-TP was not recognized by mitochondrial DNA Pol gamma and failed to be incorporated into DNA or inhibit the polymerase assay at the highest levels tested, 300 microM. Combinations of ETV with each of the other HBV NRTI antivirals, adefovir, tenofovir, and lamivudine at 10 times their respective C(max) levels also failed to result in cellular or mitochondrial toxicity. In summary, cell culture and enzymatic studies yielded no evidence that would predict mitochondrial toxicity of ETV at exposure levels in excess of those expected to be achieved clinically.
Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
Charles E
CE
Mazzucco
Robert K
RK
Hamatake
Richard J
RJ
Colonno
Daniel J
DJ
Tenney
D000998:Antiviral Agents / Q000009:adverse effects* / Q000494:pharmacology / Q000627:therapeutic use; D000074002:DNA Polymerase gamma; D004272:DNA, Mitochondrial / Q000187:drug effects; D004259:DNA-Directed DNA Polymerase; D042963:Electron Transport Complex II / Q000187:drug effects / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000187:drug effects / Q000378:metabolism; D006147:Guanine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D006509:Hepatitis B / Q000188:drug therapy / Q000821:virology; D006515:Hepatitis B virus / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors; D018894:Reverse Transcriptase Inhibitors / Q000009:adverse effects* / Q000494:pharmacology / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
D000998:Antiviral Agents; D004272:DNA, Mitochondrial; D019384:Nucleic Acid Synthesis Inhibitors; D018894:Reverse Transcriptase Inhibitors; C413685:entecavir; D006147:Guanine; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase