With the introduction of direct-acting antivirals (DAAs), treatment against hepatitis C virus (HCV) has significantly improved. To manage and control this worldwide infectious disease better, the "best" multidrug treatment is demanded based on scientific evidence. However, there is no method available that systematically quantifies and compares the antiviral efficacy and drug-resistance profiles of drug combinations. Based on experimental anti-HCV profiles in a cell culture system, we quantified the instantaneous inhibitory potential (IIP), which is the logarithm of the reduction in viral replication events, for both single drugs and multiple-drug combinations. From the calculated IIP of 15 anti-HCV drugs from different classes [telaprevir, danoprevir, asunaprevir, simeprevir, sofosbuvir (SOF), VX-222, dasabuvir, nesbuvir, tegobuvir, daclatasvir, ledipasvir, IFN-α, IFN-λ1, cyclosporin A, and SCY-635], we found that the nucleoside polymerase inhibitor SOF had one of the largest potentials to inhibit viral replication events. We also compared intrinsic antiviral activities of a panel of drug combinations. Our quantification analysis clearly indicated an advantage of triple-DAA treatments over double-DAA treatments, with triple-DAA treatments showing enhanced antiviral activity and a significantly lower probability for drug resistance to emerge at clinically relevant drug concentrations. Our framework provides quantitative information to consider in designing multidrug strategies before costly clinical trials.instantaneous inhibitory potential H epatitis C virus (HCV) affects ∼170 million people worldwide (1-4) and is a major cause of liver cirrhosis and hepatocellular carcinoma. The standard treatment has long been a combination of IFN, IFN-α or pegylated IFN-α (peg-IFN-α), with ribavirin (RBV), with a sustained virological response (SVR) rate of around 50% (5). Improvements in the SVR rate have been made by using anti-HCV agents that inhibit viral-derived factors or cellular factors that are essential for viral replication. Agents inhibiting viral proteins, called direct-acting antivirals (DAAs), typically target HCV nonstructural (NS)3 protease, NS5A, and NS5B polymerase (3). Anti-HCV molecules that target cellular factors, so-called hosttargeting antivirals (HTAs), include those HTAs inhibiting cyclophilins and microRNA-122, which are required for HCV replication (3). These agents have been evaluated in clinical trials. In 2011, the protease inhibitors (PIs) telaprevir (TPV) and boceprevir were approved by the US Food and Drug Administration for use in combination with peg-IFN and RBV. These drug combinations achieved significantly improved clinical outcomes, attaining more than a 70% SVR rate (5).

Background Mpox virus (MPXV) is a zoonotic orthopoxvirus and caused an outbreak in 2022. Although tecovirimat and brincidofovir are approved as anti-smallpox drugs, their effects in mpox patients have not been well documented. In this study, by a drug repurposing approach, we identified potential drug candidates for treating mpox and predicted their clinical impacts by mathematical modeling. Methods We screened approved 132 drugs using an MPXV infection cell system. We quantified antiviral activities of hit drugs by measuring intracellular viral DNA and analyzed the modes of action by time-of-addition assay and electron microscopic analysis. We further predicted the efficacy of drugs under clinical concentrations by mathematical simulation and examined combination treatment. Results Atovaquone, mefloquine, and molnupiravir exhibited anti-MPXV activity, with 50% inhibitory concentrations of 0.51-5.2 μM, which was more potent than cidofovir. Whereas mefloquine was suggested to inhibit viral entry, atovaquone and molnupiravir targeted post-entry process. Atovaquone was suggested to exert its activity through inhibiting dihydroorotate dehydrogenase. Combining atovaquone with tecovirimat enhanced the anti-MPXV effect of tecovirimat. Quantitative mathematical simulations predicted that atovaquone can promote viral clearance in patients by seven days at clinically relevant drug concentrations. Conclusion These data suggest that atovaquone would be potential candidates for treating mpox.