Efficacy of hepatitis B virus ribonuclease H inhibitors, a new class of replication antagonists, in FRG human liver chimeric mice

Abstract

Chronic hepatitis B virus infection cannot be cured by current therapies, so new treatments are urgently needed. We recently identified novel inhibitors of the hepatitis B virus ribonuclease H that suppress viral replication in cell culture. Here, we employed immunodeficient FRG KO mice whose livers had been engrafted with primary human hepatocytes to ask whether ribonuclease H inhibitors can suppress hepatitis B virus replication in vivo. Humanized FRG KO mice infected with hepatitis B virus were treated for two weeks with the ribonuclease H inhibitors #110, an α-hydroxytropolone, and #208, an N-hydroxypyridinedione. Hepatitis B virus viral titers and S and e antigen plasma levels were measured. Treatment with #110 and #208 caused significant reductions in plasma viremia without affecting hepatitis B virus S or e antigen levels, and viral titers rebounded following treatment cessation. This is the expected pattern for inhibitors of viral DNA synthesis. Compound #208 suppressed viral titers of both hepatitis B virus genotype A and C isolates. These data indicate that Hepatitis B virus replication can be suppressed during infection in an animal by inhibiting the viral ribonuclease H, validating the ribonuclease H as a novel target for antiviral drug development.

3,7-Dihydroxytropolones Inhibit Initiation of Hepatitis B Virus Minus-Strand DNA Synthesis

“…Based on the requirement for divalent metal (Mg ++ ) at the DNA polymerase and RNase H active sites of HBV P protein, α–HTs, which we [ 11 ], and others [ 9 , 13 , 15 , 25 , 26 , 39 ] have studied extensively as viral RNase H inhibitors, were a logical starting choice. However, despite showing good activity against recombinant HBV RNase H, α–HTs were poorly active in inhibiting minus-strand priming.…”

“…Although no inhibitor of HIV-1 RT RNase H function has advanced to the clinic, intense efforts over almost 2 decades have made a plethora of compounds available for testing its HBV counterpart [ 9 , 10 ]. Following reports that the natural product α-hydroxytropolone (α-HT), β-thujaplicinol [ 11 ] inhibits HBV replication by sequestering the catalytic Mg ++ in the RNase H active site [ 12 ], modified α-HTs [ 13 ], 2-hydroxyisoquinoline-1,3(2H,4H)-diones [ 14 ] and N -hydroxypyridinediones, have emerged as a new class of RNase H inhibitors [ 15 ]. The availability of an active form of the isolated HBV RNase H domain [ 16 ] should also promote development of high-throughput assays to accelerate drug-screening efforts.…”

Ribonuclease H, an unexploited target for antiviral intervention against HIV and hepatitis B virus

“…Suppression of HBV replication has been observed in chimeric mice carrying humanized livers after treatment with N-hydroxypyridinedione or α-hydroxytropolone derivatives (compounds 110 and 208; Figure 16) (Long et al, 2018). These results, that were further confirmed for HBV genotype A and C isolates using the N-hydroxypyridinedione derivative compound 208, confirmed that indeed HBV replication can be suppressed in vivo with specific RNase H inhibitors, thereby further validating the enzyme as a target for antiviral drug development.…”

Divergent synthesis of a thiolate-based α-hydroxytropolone library with a dynamic bioactivity profile

“…5), which also suppresses HBV viremia in an animal model. 30 We hypothesized that electron-withdrawing groups on the aHT could improve potency by stabilizing a dianionic state that may exist when the aHT is bound to the target enzyme, which is believed to be the dinuclear metalloenzyme HBV ribonuclease H (RNaseH). 31 Thus, the thiolate-based library provided us with an opportunity to probe this structure-function activity relationship in more detail.…”