Remdesivir (RDV), a single diastereomeric monophosphoramidate prodrug that inhibits viral RNA polymerases, has potent in vitro antiviral activity against severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2). RDV received the US Food and Drug Administration (FDA)’s emergency use authorization in the United States and approval in Japan for treatment of patients with severe coronavirus disease 2019 (COVID‐19). This report describes two phase I studies that evaluated the safety and pharmacokinetics (PKs) of single escalating and multiple i.v. doses of RDV (solution or lyophilized formulation) in healthy subjects. Lyophilized formulation was evaluated for potential future use in clinical trials due to its storage stability in resource‐limited settings. All adverse events were grade 1 or 2 in severity. Overall, RDV exhibited a linear profile following single‐dose i.v. administration over 2 hours of RDV solution formulation across the dose range of 3–225 mg. Both lyophilized and solution formulations provided comparable PK parameters. High intracellular concentrations of the active triphosphate (~ 220‐fold to 370‐fold higher than the in vitro half‐maximal effective concentration against SARS‐CoV‐2 clinical isolate) were achieved following infusion of 75 mg or 150 mg lyophilized formulation over 30 minutes or 2 hours. Following multiple‐doses of RDV 150 mg once daily for 7 or 14 days, RDV exhibited a PK profile similar to single‐dose administration. Metabolite GS‐441524 accumulated ~ 1.9‐fold after daily dosing. Overall, RDV exhibited favorable safety and PK profiles that supported once‐daily dosing.

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Remdesivir (RDV, Veklury ® ) is a once-daily, nucleoside ribonucleic acid polymerase inhibitor of severe acute respiratory syndrome coronavirus 2 replication. Remdesivir has been granted approvals in several countries for use in adults and children hospitalized with severe coronavirus disease 2019 (COVID-19). Inside the cell, remdesivir undergoes metabolic activation to form the intracellular active triphosphate metabolite, GS-443902 (detected in peripheral blood mononuclear cells), and ultimately, the renally eliminated plasma metabolite GS-441524. This review discusses the pre-clinical pharmacology of RDV, clinical pharmacokinetics, pharmacodynamics/concentration-QT analysis, rationale for dose selection for treatment of patients with COVID-19, and drug–drug interaction potential based on available in vitro and clinical data in healthy volunteers. Following single-dose intravenous administration over 2 h of an RDV solution formulation across the dose range of 3–225 mg in healthy participants, RDV and its metabolites (GS-704277and GS-441524) exhibit linear pharmacokinetics. Following multiple doses of RDV 150 mg once daily for 7 or 14 days, major metabolite GS-441524 accumulates approximately 1.9-fold in plasma. Based on pharmacokinetic bridging from animal data and available human data in healthy volunteers, the RDV clinical dose regimen of a 200-mg loading dose on day 1 followed by 100-mg maintenance doses for 4 or 9 days was selected for further evaluation of pharmacokinetics and safety. Results showed high intracellular concentrations of GS-443902 suggestive of efficient conversion from RDV into the triphosphate form, and further supporting this clinical dosing regimen for the treatment of COVID-19. Mathematical drug–drug interaction liability predictions, based on in vitro and phase I data, suggest RDV has low potential for drug–drug interactions, as the impact of inducers or inhibitors on RDV disposition is minimized by the parenteral route of administration and extensive extraction. Using physiologically based pharmacokinetic modeling, RDV is not predicted to be a clinically significant inhibitor of drug-metabolizing enzymes or transporters in patients infected with COVID-19 at therapeutic RDV doses. Supplementary Information The online version contains supplementary material available at 10.1007/s40262-021-00984-5.

Drug transporter and cytochrome P450 expression is regulated by shared nuclear receptors and, hence, an inducer should induce both, although the magnitude may differ. The objective of this study was to establish relative induction relationships between CYP3A and drug transporters (P‐glycoprotein (P‐gp), organic anion transporting polypeptide (OATP), and breast cancer resistance protein (BCRP)) or other P450s (CYP2C9 and CYP1A2) using ascending doses of the prototypical pregnane xenobiotic receptor (PXR) agonist, rifampin, to elicit weak, moderate, and strong PXR agonism. Healthy subjects received dabigatran etexilate, pravastatin, rosuvastatin, and a midazolam/tolbutamide/caffeine cocktail before and after rifampin 2, 10, 75, or 600 mg q.d. Unlike CYP3A, only moderate induction of P‐gp, OATP, and CYP2C9 was observed and dose‐dependent induction of P‐gp, OATP, and CYP2C9 was always one drug–drug interaction category lower than observed for CYP3A, even when correcting for probe drug sensitivity. Data from this study establish proof‐of‐concept that P450 induction data can be leveraged to inform on the effect on transporters.

Rifampin demonstrated dose‐dependent relative induction between cytochrome P (CYP)3A and P‐glycoprotein (P‐gp), organic anion transporting polypeptides (OATPs), or CYP2C9; P‐gp, OATP, and CYP2C9 induction was one drug–drug interaction (DDI) category lower than that observed for CYP3A across a wide range of pregnane X receptor (PXR) agonism. The objective of this study was to determine if these relationships could be utilized to predict transporter induction by other CYP3A inducers (rifabutin and carbamazepine) and of another P‐gp substrate, sofosbuvir. Healthy subjects received sofosbuvir and a six‐probe drug cassette before and after 300 mg q.d. rifabutin or 300 mg b.i.d. carbamazepine. Induction of P‐gp, CYP2C9, and decreased sofosbuvir exposure were successfully predicted by observed CYP3A induction. Carbamazepine induction of OATP was underpredicted, likely due to reported additional non‐PXR agonism. The results demonstrate that the effect of a PXR agonist on CYP3A can be leveraged to inform on induction liability for other primarily PXR‐regulated P450s/transporters, allowing for prioritization of targeted DDI assessments during new drug development.