Identification of Retinoic Acid Receptor Agonists as Potent Hepatitis B Virus Inhibitors via a Drug Repurposing Screen

Abstract

Currently available therapies for chronic hepatitis B virus (HBV) infection can efficiently reduce viremia but induce hepatitis B surface antigen (HBsAg) loss in very few patients; also, these therapies do not greatly affect the viral covalently closed circular DNA (cccDNA). To discover new agents with complementary anti-HBV effects, we performed a drug repurposing screen of 1,018 Food and Drug Administration (FDA)-approved compounds using HBV-infected primary human hepatocytes (PHH). Several compounds belonging to the family of retinoic acid receptor (RAR) agonists were identified that reduced HBsAg levels in a dose-dependent manner without significant cytotoxicity. Among them, tazarotene exhibited the most potent anti-HBV effect, with a half-maximal inhibitory concentration (IC) for HBsAg of less than 30 nM in PHH. The inhibitory effect was also observed in HBV-infected differentiated HepaRG (dHepaRG) models, but not in HepG2.215 cells, and HBV genotypes A to D were similarly inhibited. Tazarotene was further demonstrated to repress HBV cccDNA transcription, as determined by the levels of HBV cccDNA and RNAs and the activation of HBV promoters. Moreover, RNA sequence analysis showed that tazarotene did not induce an interferon response but altered the expression of a number of genes associated with RAR and metabolic pathways. Inhibition of RARβ, but not RARα, by a specific antagonist significantly attenuated the anti-HBV activity of tazarotene, suggesting that tazarotene inhibits HBV in part through RARβ. Finally, a synergistic effect of tazarotene and entecavir on HBV DNA levels was observed. Therefore, RAR agonists as represented by tazarotene were identified as potential novel anti-HBV agents.

A role for retinoids in the treatment of COVID‐19?

“…Similarly, Chen et al reported that the antiviral effects of RA against enterovirus 71 are mediated through IFN‐α and RIG‐I 25 . Natural and synthetic retinoids also have direct inhibitory effects on replication of a number of viruses, including hepatitis B virus (HBV), cytomegalovirus, influenza, MeV, and norovirus 27‐30 . There is also evidence that activation of retinoid signalling can potently inhibit coronaviruses 31 .…”

Strategies to Inhibit Hepatitis B Virus Gene Transcription

“…The most potent hit, Tazarotene, inhibits transcription from cccDNA with IC50 value of 20~75 nM without reducing cccDNA levels. It targets mostly RAR but not RAR and RAR in infected primary hepatocytes [108]. Nkongolo et al identified Tamibarotene (Am80) using another FDA approved drug library and further compared Tamibarotene (RAR-specific) with other agonists, Tazarotene (RAR/-specific), Adapalene (RAR-specific), all-trans retinoic acid (pan-activity).…”

The rationale for a multi-step therapeutic approach based on antivirals, drugs and nutrients with immunomodulatory activity in patients with coronavirus-SARS2-induced disease of different severities

“…Some vitamins, like vitamins E, D and A, have been used in clinical trials for the treatment of patients with persistent viral infections, including HBV, HCV and HIV. These micronutrients have been demonstrated to enhance both the innate and the adaptive immunity against these pathogens (61,(68)(69)(70)(71)(72)(73) and to decrease susceptibility of CD4þ T lymphocytes to HIV-1 infection (74) . Furthermore, vitamins A, D and E have been suggested to improve innate and adaptive immune response against respiratory viruses, including influenza virus, rhinovirus and respiratory syncytial virus both in vivo and in vitro studies (75) .…”