Activation of PXR causes drug interactions with Paxlovid in transgenic mice

Paxlovid is a nirmatrelvir(NMV)and ritonavir(RTV)co-packaged medication used for the treatment of coronavirus disease 2019(COVID-19).The active component of Paxlovid is NMV and RTV is a pharmacokinetic booster.Our work aimed to investigate the drug/herb-drug interactions associated with Paxlovid and provide mechanism-based guidance for the clinical use of Paxlovid.By using recombinant human cytochrome P450s(CYPs),we confirmed that CYP3A4 and 3A5 are the major enzymes responsible for NMV metabolism.The role of CYP3A in Paxlovid metabolism were further verified in Cyp3a-null mice,which showed that the deficiency of CYP3A significantly suppressed the metabolism of NMV and RTV.Pregnane X receptor(PXR)is a ligand-dependent transcription factor that upregulates CYP3A4/5 expression.We next explored the impact of drug-and herb-mediated PXR activation on Paxlovid metabolism in a transgenic mouse model expressing human PXR and CYP3A4/5.We found that PXR activation increased CYP3A4/5 expression,accelerated NMV metabolism,and reduced the systemic exposure of NMV.In summary,our work demonstrated that PXR activation can cause drug interactions with Paxlovid,suggesting that PXR-activating drugs and herbs should be used cautiously in COVID-19 patients receiving Paxlovid.

Chemical basis of pregnane X receptor activators in the herbal supplement Gancao (licorice)

Background and aims:The herbal supplement Gancao,also known as licorice,belongs to the genus Glycyrrhiza and has been used worldwide for its hepatoprotective effect.Recent studies have raised concerns about potential herb-drug interactions associated with Gancao via pregnane X receptor(PXR)-mediated induction of hepatic cytochrome P4503A4(CYP3A4).The current work aimed to determine the phytochemicals in Gancao that activate PXR and induce CYP3A4.Methods:DPX2 cells were used for cell-based PXR reporter assays.The phytochemicals in Gancao extract were identified using a metabolomics approach.The effects of PXR activators identified from in vitro studies were further investigated in PXR-and CYP3A4-humanized mouse models.Results:Gancao was verified to be a PXR-activating herb.Two major phytochemicals in Gancao,gly-cyrrhizin(GZ)and glycyrrhetinic acid(GA),did not activate PXR in the cell-based reporter assays.However,glabridin was shown to activate PXR in a dose-dependent manner.In vivo studies confirmed that GZ is not a PXR activator and glabridin is a weak PXR activator.Although GA did not active PXR in vitro,it induced CYP3A4 expression in a PXR-dependent manner in the PXR-and CYP3A4-humanized mice.

Clinical perspectives of isoniazid-induced liver injury

Isoniazid(INH)is a synthetic anti-mycobacterial agent used to treat active or latent tuberculosis(TB).INH has been in clinical use for nearly 70 years and remains broadly utilized at the front line of anti-TB treatment.However,the potential for liver damage and even fulminant liver failure during INH-based TB treatment presents a major challenge for TB control programs worldwide.In this review,we discuss the hepatotoxic effects of INH and provide an overview of the mechanisms and their applications in prediction and prevention of INH hepatotoxicity in clinical practice.