ABSTRACT
The Omicron variant (B.1.1.529) of SARS-CoV-2 has placed enormous strain on global healthcare systems since it was first identified by South African researchers in late 2021. Omicron has >50 mutations which mainly occur in the surface spike protein and this has led to rapid assessment of monoclonal antibodies to assess the impact on virus neutralisation. Ronapreve has shown potential application in post-exposure prophylaxis, mild/moderate disease and in seronegative patients with severe COVID19, but several early reports of loss of in vitro neutralisation activity have been documented. Here, the virological efficacy of Ronapreve was assessed in K18-hACE2 mice to provide an in vivo outcome. Ronapreve reduced sub-genomic RNA in lung and nasal turbinate for the Delta variant but not the Omicron variant of SARS-CoV-2 at doses 2-fold higher than those shown to be active against previous variants of the virus. These data add to the growing evidence that the effectiveness of Ronapreve is compromised for the Omicron variant.
ABSTRACT
Successful development of a chemoprophylaxis against SARS-CoV-2 could provide a tool for infection prevention implementable alongside vaccination programmes. Camostat and nafamostat are serine protease inhibitors that inhibit SARS-CoV-2 viral entry in vitro but have not been characterised for chemoprophylaxis in animal models. Clinically, nafamostat is limited to intravenous delivery and while camostat is orally available, both drugs have extremely short plasma half-lives. This study sought to determine whether intranasal dosing at 5 mg/kg twice daily was able to prevent airborne transmission of SARS-CoV-2 from infected to uninfected Syrian golden hamsters. SARS-CoV-2 viral RNA was above the limits of quantification in both saline- and camostat-treated hamsters 5 days after cohabitation with a SARS-CoV-2 inoculated hamster. However, intranasal nafamostat-treated hamsters remained RNA negative for the full 7 days of cohabitation. Changes in body weight over the course of the experiment were supportive of a lack of clinical symptomology in nafamostat-treated but not saline- or camostat-treated animals. These data are strongly supportive of the utility of intranasally delivered nafamostat for prevention of SARS-CoV-2 infection and further studies are underway to confirm absence of pulmonary infection and pathological changes.
ABSTRACT
Currently nitazoxanide is being assessed as a candidate therapeutic for SARS-CoV-2. Unlike many other candidates being investigated, tizoxanide (the active metabolite of nitazoxanide) plasma concentrations achieve antiviral levels after administration of the approved dose, although higher doses are expected to be needed to maintain these concentrations across the dosing interval in the majority of patients. Here an LC-MS/MS assay is described that has been validated in accordance with Food and Drug Administration (FDA) guidelines. Fundamental parameters have been evaluated, and these included accuracy, precision and sensitivity. The assay was validated for human plasma, mouse plasma and Dulbeccos Modified Eagles Medium (DMEM) containing varying concentrations of Foetal Bovine Serum (FBS). Matrix effects are a well-documented source of concern for chromatographic analysis, with the potential to impact various stages of the analytical process, including suppression or enhancement of ionisation. Therefore, a robustly validated LC-MS/MS analytical method is presented capable of quantifying tizoxanide in multiple matrices with minimal impact of matrix effects. The validated assay presented here was linear from 15.6ng/mL to 1000ng/mL. Accuracy and precision ranged between 102.2% and 113.5%, 100.1% and 105.4%, respectively. The presented assay here has applications in both pre-clinical and clinical research and may be used to facilitate further investigations into the application of nitazoxanide against SARS-CoV-2.
ABSTRACT
The ability of acquired immune responses against SARS-CoV-2 to protect after subsequent exposure to emerging variants of concern (VOC) such as B1.1.7 and B1.351 is currently of high significance. Here, we use a hamster model of COVID-19 to show that prior infection with a strain representative of the original circulating lineage B of SARS-CoV-2 induces protection from clinical signs upon subsequent challenge with either B1.1.7 or B1.351 viruses, which recently emerged in the UK and South Africa, respectively. The results indicate that these emergent VOC may be unlikely to cause disease in individuals that are already immune due to prior infection, and this has positive implications for overall levels of infection and COVID-19 disease.
ABSTRACT
Favipiravir (FAV; T-705) has been approved for use as an anti-influenza therapeutic and has reports against a wide range of viruses (e.g., Ebola virus, rabies and norovirus). Most recently FAV has been reported to demonstrate activity against SARS-CoV-2. Repurposing opportunities have been intensively studied with only limited success to date. If successful, repurposing will allow interventions to become more rapidly available than development of new chemical entities. Pre-clinical and clinical investigations of FAV require robust, reproducible and sensitive bioanalytical assay. Here, a liquid chromatography tandem mass spectrometry assay is presented which was linear from 0.78-200 ng/mL Accuracy and precision ranged between 89% and 110%, 101% and 106%, respectively. The presented assay here has applications in both pre-clinical and clinical research and may be used to facilitate further investigations into the application of FAV against SARS-CoV-2.
ABSTRACT
BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared a global pandemic by the World Health Organisation and urgent treatment and prevention strategies are needed. Many clinical trials have been initiated with existing medications, but assessments of the expected plasma and lung exposures at the selected doses have not featured in the prioritisation process. Although no antiviral data is currently available for the major phenolic circulating metabolite of nitazoxanide (known as tizoxanide), the parent ester drug has been shown to exhibit in vitro activity against SARS-CoV-2. Nitazoxanide is an anthelmintic drug and its metabolite tizoxanide has been described to have broad antiviral activity against influenza and other coronaviruses. The present study used physiologically-based pharmacokinetic (PBPK) modelling to inform optimal doses of nitazoxanide capable of maintaining plasma and lung tizoxanide exposures above the reported nitazoxanide 90% effective concentration (EC90) against SARS-CoV-2. MethodsA whole-body PBPK model was constructed for oral administration of nitazoxanide and validated against available tizoxanide pharmacokinetic data for healthy individuals receiving single doses between 500 mg - 4000 mg with and without food. Additional validation against multiple-dose pharmacokinetic data when given with food was conducted. The validated model was then used to predict alternative doses expected to maintain tizoxanide plasma and lung concentrations over the reported nitazoxanide EC90 in >90% of the simulated population. Optimal design software PopDes was used to estimate an optimal sparse sampling strategy for future clinical trials. ResultsThe PBPK model was validated with AAFE values between 1.01 - 1.58 and a difference less than 2-fold between observed and simulated values for all the reported clinical doses. The model predicted optimal doses of 1200 mg QID, 1600 mg TID, 2900 mg BID in the fasted state and 700 mg QID, 900 mg TID and 1400 mg BID when given with food, to provide tizoxanide plasma and lung concentrations over the reported in vitro EC90 of nitazoxanide against SARS-CoV-2. For BID regimens an optimal sparse sampling strategy of 0.25, 1, 3 and 12h post dose was estimated. ConclusionThe PBPK model predicted that it was possible to achieve plasma and lung tizoxanide concentrations, using proven safe doses of nitazoxanide, that exceed the EC90 for SARS-CoV-2. The PBPK model describing tizoxanide plasma pharmacokinetics after oral administration of nitazoxanide was successfully validated against clinical data. This dose prediction assumes that the tizoxanide metabolite has activity against SARS-CoV-2 similar to that reported for nitazoxanide, as has been reported for other viruses. The model and the reported dosing strategies provide a rational basis for the design (optimising plasma and lung exposures) of future clinical trials of nitazoxanide in the treatment or prevention of SARS-CoV-2 infection.
ABSTRACT
There is a rapidly expanding literature on the in vitro antiviral activity of drugs that may be repurposed for therapy or chemoprophylaxis against SARS-CoV-2. However, this has not been accompanied by a comprehensive evaluation of the ability of these drugs to achieve target plasma and lung concentrations following approved dosing in humans. Moreover, most publications have focussed on 50% maximum effective concentrations (EC50), which may be an insufficiently robust indicator of antiviral activity because of marked differences in the slope of the concentration-response curve between drugs. Accordingly, in vitro anti-SARS-CoV-2 activity data was digitised from all available publications up to 13th April 2020 and used to recalculate an EC90 value for each drug. EC90 values were then expressed as a ratio to the achievable maximum plasma concentrations (Cmax) reported for each drug after administration of the approved dose to humans (Cmax/EC90 ratio). Only 14 of the 56 analysed drugs achieved a Cmax/EC90 ratio above 1 meaning that plasma Cmax concentrations exceeded those necessary to inhibit 90% of SARS-CoV-2 replication. A more in-depth assessment of the putative agents tested demonstrated that only nitazoxanide, nelfinavir, tipranavir (boosted with ritonavir) and sulfadoxine achieved plasma concentrations above their reported anti-SARS-CoV-2 activity across their entire approved dosing interval at their approved human dose. For all drugs reported, the unbound lung to plasma tissue partition coefficient (KpUlung) was also simulated and used along with reported Cmax and fraction unbound in plasma to derive a lung Cmax/EC50 as a better indicator of potential human efficacy (lung Cmax/EC90 ratio was also calculable for a limited number of drugs). Using this parameter hydroxychloroquine, chloroquine, mefloquine, atazanavir (boosted with ritonavir), tipranavir (boosted with ritonavir), ivermectin, azithromycin and lopinavir (boosted with ritonavir) were all predicted to achieve lung concentrations over 10-fold higher than their reported EC50. This analysis was not possible for nelfinavir because insufficient data were available to calculate KpUlung but nitozoxanide and sulfadoxine were also predicted to exceed their reported EC50 by 3.1- and 1.5-fold in lung, respectively. The antiviral activity data reported to date have been acquired under different laboratory conditions across multiple groups, applying variable levels of stringency. However, this analysis may be used to select potential candidates for further clinical testing, while deprioritising compounds which are unlikely to attain target concentrations for antiviral activity. Future studies should focus on EC90 values and discuss findings in the context of achievable exposures in humans, especially within target compartments such as the lung, in order to maximise the potential for success of proposed human clinical trials.