Hyaluronidase impacts exposures of long-acting injectable paliperidone palmitate in rodent models.

A significant challenge in the development of long-acting injectable drug formulations, especially for anti-infective agents, is delivering an efficacious dose within a tolerable injection volume. Co-administration of the extracellular matrix-degrading enzyme hyaluronidase can increase maximum tolerable injection volumes but is untested for this benefit with long-acting injectable formulations. One concern is that hyaluronidase could potentially alter the tissue response surrounding an injection depot, a response known to be important for drug release kinetics of long-acting injectable formulations. The objective of this pilot study was to evaluate the impact of co-administration of hyaluronidase on the drug release kinetics, pharmacokinetic profiles, and injection site histopathology of the long-acting injectable paliperidone palmitate for up to four weeks following intramuscular injection in mouse and rat models. In both species, co-administration of hyaluronidase increased paliperidone plasma exposures the first week after injection but did not negate the overall long-acting release nature of the formulation. Hyaluronidase-associated modification of the injection site depot was observed in mice but not in rats. These findings suggest that further investigation of hyaluronidase with long-acting injectable agents is warranted.

Lack of antiviral activity of probenecid in vitro and in Syrian golden hamsters.

OBJECTIVES: Antiviral interventions are required to complement vaccination programmes and reduce the global burden of COVID-19. Prior to initiation of large-scale clinical trials, robust preclinical data to support candidate plausibility are required. This work sought to further investigate the putative antiviral activity of probenecid against SARS-CoV-2. METHODS: Vero E6 cells were preincubated with probenecid, or control media for 2 h before infection (SARS-CoV-2/Human/Liverpool/REMRQ0001/2020). Probenecid or control media was reapplied, plates reincubated and cytopathic activity quantified by spectrophotometry after 48 h. In vitro human airway epithelial cell (HAEC) assays were performed for probenecid against SARS-CoV-2-VoC-B.1.1.7 (hCoV-19/Belgium/rega-12211513/2020; EPI_ISL_791333, 2020-12-21) using an optimized cell model for antiviral testing. Syrian golden hamsters were intranasally inoculated (SARS-CoV-2 Delta B.1.617.2) 24 h prior to treatment with probenecid or vehicle for four twice-daily doses. RESULTS: No observable antiviral activity for probenecid was evident in Vero E6 or HAEC assays. No reduction in total or subgenomic RNA was observed in terminal lung samples (P > 0.05) from hamsters. Body weight of uninfected hamsters remained stable whereas both probenecid- and vehicle-treated infected hamsters lost body weight (P > 0.5). CONCLUSIONS: These data do not support probenecid as a SARS-CoV-2 antiviral drug.

Physiologically Based Pharmacokinetic Modelling of Cabotegravir Microarray Patches in Rats and Humans.

Microarray patches (MAPs) are currently under investigation as a self-administered, pain-free alternative used to achieve long-acting (LA) drug delivery. Cabotegravir is a potent antiretroviral that has demonstrated superior results over current pre-exposure prophylaxis (PrEP) regimens. This study aimed to apply physiologically based pharmacokinetic (PBPK) modelling to describe the pharmacokinetics of the dissolving bilayer MAP platform and predict the optimal dosing strategies for a once-weekly cabotegravir MAP. A mathematical description of a MAP was implemented into a PBPK model, and empirical models were utilised for parameter estimation. The intradermal PBPK model was verified against previously published in vivo rat data for intramuscular (IM) and MAP administration, and in vivo human data for the IM administration of LA cabotegravir. The verified model was utilised for the prediction of 300 mg, 150 mg and 75 mg once-weekly MAP administration in humans. Cabotegravir plasma concentrations >4 × protein-adjusted 90% inhibitory concentration (PA-IC90) (0.664 µg/mL) and >8 × PA-IC90 (1.33 µg/mL) were set as targets. The 75 mg, 150 mg and 300 mg once-weekly cabotegravir MAP regimens were predicted to sustain plasma concentrations >4 × PA-IC90, while the 300 mg and 150 mg regimens achieved plasma concentrations >8 × PA-IC90. These data demonstrate the potential for a once-weekly cabotegravir MAP using practical patch sizes for humans and inform the further development of cabotegravir MAPs for HIV PrEP.

Chemoprophylactic Assessment of Combined Intranasal SARS-CoV-2 Polymerase and Exonuclease Inhibition in Syrian Golden Hamsters.

Pibrentasvir (PIB) has been demonstrated to block exonuclease activity of the SARS-CoV-2 polymerase, protecting favipiravir (FVP) and remdesivir (RDV) from post-incorporation excision and eliciting antiviral synergy in vitro. The present study investigated the chemoprophylactic efficacy of PIB, FVP, RDV, FVP with PIB, or RDV with PIB dosed intranasally twice a day, using a Syrian golden hamster contact transmission model. Compared to the saline control, viral RNA levels were significantly lower in throat swabs in FVP (day 7), RDV (day 3, 5, 7), and RDV+PIB (day 3, 5) treatment groups. Similarly, findings were evident for nasal turbinate after PIB and RDV treatment, and lungs after PIB, FVP, and FVP+PIB treatment at day 7. Lung viral RNA levels after RDV and RDV+PIB treatment were only detectable in two animals per group, but the overall difference was not statistically significant. In situ examination of the lungs confirmed SARS-CoV-2 infection in all animals, except for one in each of the RDV and RDV+PIB treatment groups, which tested negative in all virus detection approaches. Overall, prevention of transmission was observed in most animals treated with RDV, while other agents reduced the viral load following contact transmission. No benefit of combining FVP or RDV with PIB was observed.

Evaluation of Nafamostat as Chemoprophylaxis for SARS-CoV-2 Infection in Hamsters.

The successful development of a chemoprophylaxis against SARS-CoV-2 could provide a tool for infection prevention that is implementable alongside vaccination programmes. Nafamostat is a serine protease inhibitor that inhibits SARS-CoV-2 entry in vitro, but it has not been characterised for chemoprophylaxis in animal models. Clinically, nafamostat is limited to intravenous delivery and has an extremely short plasma half-life. This study sought to determine whether intranasal dosing of nafamostat at 5 mg/kg twice daily was able to prevent the airborne transmission of SARS-CoV-2 from infected to uninfected Syrian Golden hamsters. SARS-CoV-2 RNA was detectable in the throat swabs of the water-treated control group 4 days after cohabitation with a SARS-CoV-2 inoculated hamster. However, throat swabs from the intranasal nafamostat-treated hamsters remained SARS-CoV-2 RNA negative for the full 4 days of cohabitation. Significantly lower SARS-CoV-2 RNA concentrations were seen in the nasal turbinates of the nafamostat-treated group compared to the control (p = 0.001). A plaque assay quantified a significantly lower concentration of infectious SARS-CoV-2 in the lungs of the nafamostat-treated group compared to the control (p = 0.035). When taken collectively with the pathological changes observed in the lungs and nasal mucosa, these data are strongly supportive of the utility of intranasally delivered nafamostat for the prevention of SARS-CoV-2 infection.

Quantitation of tizoxanide in multiple matrices to support cell culture, animal and human research.

Currently nitazoxanide is being assessed as a candidate therapeutic for SARS-CoV-2. Nitazoxanide is rapidly broken down to its active metabolite tizoxanide upon administration. Unlike many other candidates being investigated, tizoxanide 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 Dulbecco's 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. Herein a 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 15.6 ng/mL to 1000 ng/mL. 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.

Preclinical Evaluation of Long-Acting Emtricitabine Semi-Solid Prodrug Nanoparticle Formulations.

Long-acting injectable (LAI) formulations promise to deliver patient benefits by overcoming issues associated with non-adherence. A preclinical assessment of semi-solid prodrug nanoparticle (SSPN) LAI formulations of emtricitabine (FTC) is reported here. Pharmacokinetics over 28 days were assessed in Wistar rats, New Zealand white rabbits, and Balb/C mice following intramuscular injection. Two lead formulations were assessed for the prevention of an HIV infection in NSG-cmah-/- humanised mice to ensure antiviral activities were as anticipated according to the pharmacokinetics. Cmax was reached by 12, 48, and 24 h in rats, rabbits, and mice, respectively. Plasma concentrations were below the limit of detection (2 ng/mL) by 21 days in rats and rabbits, and 28 days in mice. Mice treated with SSPN formulations demonstrated undetectable viral loads (700 copies/mL detection limit), and HIV RNA remained undetectable 28 days post-infection in plasma, spleen, lung, and liver. The in vivo data presented here demonstrate that the combined prodrug/SSPN approach can provide a dramatically extended pharmacokinetic half-life across multiple preclinical species. Species differences in renal clearance of FTC mean that longer exposures are likely to be achievable in humans than in preclinical models.

Using Dynamic Oral Dosing of Rifapentine and Rifabutin to Simulate Exposure Profiles of Long-Acting Formulations in a Mouse Model of Tuberculosis Preventive Therapy.

Administration of tuberculosis preventive therapy (TPT) to individuals with latent tuberculosis infection is an important facet of global tuberculosis control. The use of long-acting injectable (LAI) drug formulations may simplify and shorten regimens for this indication. Rifapentine and rifabutin have antituberculosis activity and physiochemical properties suitable for LAI formulation, but there are limited data available for determining the target exposure profiles required for efficacy in TPT regimens. The objective of this study was to determine exposure-activity profiles of rifapentine and rifabutin to inform development of LAI formulations for TPT. We used a validated paucibacillary mouse model of TPT in combination with dynamic oral dosing of both drugs to simulate and understand exposure-activity relationships to inform posology for future LAI formulations. This work identified several LAI-like exposure profiles of rifapentine and rifabutin that, if achieved by LAI formulations, could be efficacious as TPT regimens and thus can serve as experimentally determined targets for novel LAI formulations of these drugs. We present novel methodology to understand the exposure-response relationship and inform the value proposition for investment in development of LAI formulations that have utility beyond latent tuberculosis infection.

Using dynamic oral dosing of rifapentine and rifabutin to simulate exposure profiles of long-acting formulations in a mouse model of tuberculosis preventive therapy.

Administration of tuberculosis preventive therapy (TPT) to individuals with latent tuberculosis infection is an important facet of global tuberculosis control. The use of long-acting injectable (LAI) drug formulations may simplify and shorten regimens for this indication. Rifapentine and rifabutin have anti-tuberculosis activity and physiochemical properties suitable for LAI formulation, but there are limited data available for determining the target exposure profiles required for efficacy in TPT regimens. The objective of this study was to determine exposure-activity profiles of rifapentine and rifabutin to inform development of LAI formulations for TPT. We utilized a validated paucibacillary mouse model of TPT in combination with dynamic oral dosing of both drugs to simulate and understand exposure-activity relationships to inform posology for future LAI formulations. This work identified several LAI-like exposure profiles of rifapentine and rifabutin that, if achieved by LAI formulations, could be efficacious as TPT regimens and thus can serve as experimentally-determined targets for novel LAI formulations of these drugs. We present novel methodology to understand the exposure-response relationship and inform the value proposition for investment in development of LAI formulations that has utility beyond latent tuberculosis infection.

Ronapreve (REGN-CoV; casirivimab and imdevimab) reduces the viral burden and alters the pulmonary response to the SARS-CoV-2 Delta variant (B.1.617.2) in K18-hACE2 mice using an experimental design reflective of a treatment use case.

Background: Ronapreve demonstrated clinical application in post-exposure prophylaxis, mild/moderate disease and in the treatment of seronegative patients with severe COVID19 prior to the emergence of the Omicron variant in late 2021. Numerous reports have described loss of in vitro neutralisation activity of Ronapreve and other monoclonal antibodies for BA.1 Omicron and subsequent sub-lineages of the Omicron variant. With some exceptions, global policy makers have recommended against the use of existing monoclonal antibodies in COVID19. Gaps in knowledge regarding the mechanism of action of monoclonal antibodies are noted, and further preclinical study will help understand positioning of new monoclonal antibodies under development. Objectives: The purpose of this study was to investigate the impact of Ronapreve on compartmental viral replication as a paradigm for a monoclonal antibody combination. The study also sought to confirm absence of in vivo activity against BA.1 Omicron (B.1.1.529) relative to the Delta (B.1.617.2) variant. Methods: Virological efficacy of Ronapreve was assessed in K18-hACE2 mice inoculated with either the SARS-CoV-2 Delta or Omicron variants. Viral replication in tissues was quantified using qRT-PCR to measure sub-genomic viral RNA to the E gene (sgE) as a proxy. A histological examination in combination with staining for viral antigen served to determine viral spread and associated damage. Results: Ronapreve reduced sub-genomic viral RNA levels in lung and nasal turbinate, 4 and 6 days post infection, 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. It also appeared to block brain infection which is seen with high frequency in K18-hACE2 mice after Delta variant infection. At day 6, the inflammatory response to lung infection with the Delta variant was altered to a mild multifocal granulomatous inflammation in which the virus appeared to be confined. A similar tendency was also observed in Omicron infected, Ronapreve-treated animals. Conclusions: The current study provides evidence of an altered tissue response to the SARS-CoV-2 after treatment with a monoclonal antibody combination that retains neutralization activity. These data also demonstrate that experimental designs that reflect the treatment use case are achievable in animal models for monoclonal antibodies deployed against susceptible variants. Extreme caution should be taken when interpreting prophylactic experimental designs when assessing plausibility of monoclonal antibodies for treatment use cases.

FXR inhibition may protect from SARS-CoV-2 infection by reducing ACE2.

Preventing SARS-CoV-2 infection by modulating viral host receptors, such as angiotensin-converting enzyme 2 (ACE2)1, could represent a new chemoprophylactic approach for COVID-19 that complements vaccination2,3. However, the mechanisms that control the expression of ACE2 remain unclear. Here we show that the farnesoid X receptor (FXR) is a direct regulator of ACE2 transcription in several tissues affected by COVID-19, including the gastrointestinal and respiratory systems. We then use the over-the-counter compound z-guggulsterone and the off-patent drug ursodeoxycholic acid (UDCA) to reduce FXR signalling and downregulate ACE2 in human lung, cholangiocyte and intestinal organoids and in the corresponding tissues in mice and hamsters. We show that the UDCA-mediated downregulation of ACE2 reduces susceptibility to SARS-CoV-2 infection in vitro, in vivo and in human lungs and livers perfused ex situ. Furthermore, we reveal that UDCA reduces the expression of ACE2 in the nasal epithelium in humans. Finally, we identify a correlation between UDCA treatment and positive clinical outcomes after SARS-CoV-2 infection using retrospective registry data, and confirm these findings in an independent validation cohort of recipients of liver transplants. In conclusion, we show that FXR has a role in controlling ACE2 expression and provide evidence that modulation of this pathway could be beneficial for reducing SARS-CoV-2 infection, paving the way for future clinical trials.

Determination of the Pharmacokinetics and Pharmacodynamics of Isoniazid, Rifampicin, Pyrazinamide and Ethambutol in a Cross-Over Cynomolgus Macaque Model of Mycobacterium tuberculosis Infection.

Innovative cross-over study designs were explored in non-human primate (NHP) studies to determine the value of this approach for the evaluation of drug efficacy against tuberculosis (TB). Firstly, the pharmacokinetics (PK) of each of the drugs Isoniazid (H), Rifampicin (R), Pyrazinamide (Z) and Ethambutol (E), that are standardly used for the treatment of tuberculosis, was established in the blood of macaques after oral dosing as a monotherapy or in combination. Two studies were conducted to evaluate the pharmacokinetics and pharmacodynamics of different drug combinations using cross-over designs. The first employed a balanced, three-period Pigeon design with an extra period; this ensured that treatment by period interactions and carry-over could be detected comparing the treatments HR, HZ and HRZ using H37Rv as the challenge strain of Mycobacterium tuberculosis (M. tb). Although the design accounted for considerable variability between animals, the three regimens evaluated could not be distinguished using any of the alternative endpoints assessed. However, the degree of pathology achieved using H37Rv in the model during this study was less than expected. Based on these findings, a second experiment using a classical AB/BA design comparing HE with HRZ was conducted using the M. tb Erdman strain. More extensive pathology was observed, and differences in computerized tomography (CT) scores and bacteriology counts in the lungs were detected, although due to the small group sizes, clearer differences were not distinguished. Type 1 T helper (Th1) cell response profiles were characterized using the IFN-γ ELISPOT assay and revealed differences between drug treatments that corresponded to decreases in disease burden. Therefore, the studies performed support the utility of the NHP model for the determination of PK/PD of TB drugs, although further work is required to optimize the use of cross-over study designs.

High Intrapulmonary Rifampicin and Isoniazid Concentrations Are Associated With Rapid Sputum Bacillary Clearance in Patients With Pulmonary Tuberculosis.

BACKGROUND: Intrapulmonary pharmacokinetics may better explain response to tuberculosis (TB) treatment than plasma pharmacokinetics. We explored these relationships by modeling bacillary clearance in sputum in adult patients on first-line treatment in Malawi. METHODS: Bacillary elimination rates (BER) were estimated using linear mixed-effects modelling of serial time-to-positivity in mycobacterial growth indicator tubes for sputum collected during the intensive phase of treatment (weeks 0-8) for microbiologically confirmed TB. Population pharmacokinetic models used plasma and intrapulmonary drug levels at 8 and 16 weeks. Pharmacokinetic-pharmacodynamic relationships were investigated using individual-level measures of drug exposure (area-under-the-concentration-time-curve [AUC] and Cmax) for rifampicin, isoniazid, pyrazinamide, and ethambutol, in plasma, epithelial lining fluid, and alveolar cells as covariates in the bacillary elimination models. RESULTS: Among 157 participants (58% human immunodeficiency virus [HIV] coinfected), drug exposure in plasma or alveolar cells was not associated with sputum bacillary clearance. Higher peak concentrations (Cmax) or exposure (AUC) to rifampicin or isoniazid in epithelial lining fluid was associated with more rapid bacillary elimination and shorter time to sputum negativity. More extensive disease on baseline chest radiograph was associated with slower bacillary elimination. Clinical outcome was captured in 133 participants, with 15 (11%) unfavorable outcomes recorded (recurrent TB, failed treatment, or death). No relationship between BER and late clinical outcome was identified. CONCLUSIONS: Greater intrapulmonary drug exposure to rifampicin or isoniazid in the epithelial lining fluid was associated with more rapid bacillary clearance. Higher doses of rifampicin and isoniazid may result in sustained high intrapulmonary drug exposure, rapid bacillary clearance, shorter treatment duration and better treatment outcomes.

Lack of antiviral activity of probenecid in Vero E6 cells and Syrian golden hamsters: a need for better understanding of inter-lab differences in preclinical assays.

Antiviral interventions are urgently required to support vaccination programmes and reduce the global burden of COVID-19. Prior to initiation of large-scale clinical trials, robust preclinical data in support of candidate plausibility are required. The speed at which preclinical models have been developed during the pandemic are unprecedented but there is a vital need for standardisation and assessment of the Critical Quality Attributes. This work provides cross-validation for the recent report demonstrating potent antiviral activity of probenecid against SARS-CoV-2 in preclinical models (1). Vero E6 cells were pre-incubated with probenecid, across a 7-point concentration range, or control media for 2 hours before infection with SARS-CoV-2 (SARS-CoV-2/Human/Liverpool/REMRQ0001/2020, Pango B; MOI 0.05). Probenecid or control media was then reapplied and plates incubated for 48 hours. Cells were fixed with 4% v/v paraformaldehyde, stained with crystal violet and cytopathic activity quantified by spectrophotometry at 590 nm. Syrian golden hamsters (n=5 per group) were intranasally inoculated with virus (SARS-CoV-2 Delta variant B.1.617.2; 103 PFU/hamster) for 24 hours prior to treatment. Hamsters were treated with probenecid or vehicle for 4 doses. Hamsters were ethically euthanised before quantification of total and sub-genomic pulmonary viral RNAs. No inhibition of cytopathic activity was observed for probenecid at any concentration in Vero E6 cells. Furthermore, no reduction in either total or subgenomic RNA was observed in terminal lung samples from hamsters on day 3 (P > 0.05). Body weight of uninfected hamsters remained stable throughout the course of the experiment whereas both probenecid- (6 - 9% over 3 days) and vehicle-treated (5 - 10% over 3 days) infected hamsters lost body weight which was comparable in magnitude (P > 0.5). The presented data do not support probenecid as a SARS-CoV-2 antiviral. These data do not support use of probenecid in COVID-19 and further analysis is required prior to initiation of clinical trials to investigate the potential utility of this drug.

An Open Label, Adaptive, Phase 1 Trial of High-Dose Oral Nitazoxanide in Healthy Volunteers: An Antiviral Candidate for SARS-CoV-2.

Repurposing approved drugs may rapidly establish effective interventions during a public health crisis. This has yielded immunomodulatory treatments for severe coronavirus disease 2019 (COVID-19), but repurposed antivirals have not been successful to date because of redundancy of the target in vivo or suboptimal exposures at studied doses. Nitazoxanide is a US Food and Drug Administration (FDA) approved antiparasitic medicine, that physiologically-based pharmacokinetic (PBPK) modeling has indicated may provide antiviral concentrations across the dosing interval, when repurposed at higher than approved doses. Within the AGILE trial platform (NCT04746183) an open label, adaptive, phase I trial in healthy adult participants was undertaken with high-dose nitazoxanide. Participants received 1,500 mg nitazoxanide orally twice-daily with food for 7 days. Primary outcomes were safety, tolerability, optimum dose, and schedule. Intensive pharmacokinetic (PK) sampling was undertaken day 1 and 5 with minimum concentration (Cmin ) sampling on days 3 and 7. Fourteen healthy participants were enrolled between February 18 and May 11, 2021. All 14 doses were completed by 10 of 14 participants. Nitazoxanide was safe and with no significant adverse events. Moderate gastrointestinal disturbance (loose stools or diarrhea) occurred in 8 participants (57.1%), with urine and sclera discoloration in 12 (85.7%) and 9 (64.3%) participants, respectively, without clinically significant bilirubin elevation. This was self-limiting and resolved upon drug discontinuation. PBPK predictions were confirmed on day 1 but with underprediction at day 5. Median Cmin was above the in vitro target concentration on the first dose and maintained throughout. Nitazoxanide administered at 1,500 mg b.i.d. with food was safe with acceptable tolerability a phase Ib/IIa study is now being initiated in patients with COVID-19.

Optimal dose and safety of molnupiravir in patients with early SARS-CoV-2: a Phase I, open-label, dose-escalating, randomized controlled study.

OBJECTIVES: AGILE is a Phase Ib/IIa platform for rapidly evaluating COVID-19 treatments. In this trial (NCT04746183) we evaluated the safety and optimal dose of molnupiravir in participants with early symptomatic infection. METHODS: We undertook a dose-escalating, open-label, randomized-controlled (standard-of-care) Bayesian adaptive Phase I trial at the Royal Liverpool and Broadgreen Clinical Research Facility. Participants (adult outpatients with PCR-confirmed SARS-CoV-2 infection within 5 days of symptom onset) were randomized 2:1 in groups of 6 participants to 300, 600 and 800 mg doses of molnupiravir orally, twice daily for 5 days or control. A dose was judged unsafe if the probability of 30% or greater dose-limiting toxicity (the primary outcome) over controls was 25% or greater. Secondary outcomes included safety, clinical progression, pharmacokinetics and virological responses. RESULTS: Of 103 participants screened, 18 participants were enrolled between 17 July and 30 October 2020. Molnupiravir was well tolerated at 300, 600 and 800 mg doses with no serious or severe adverse events. Overall, 4 of 4 (100%), 4 of 4 (100%) and 1 of 4 (25%) of the participants receiving 300, 600 and 800 mg molnupiravir, respectively, and 5 of 6 (83%) controls, had at least one adverse event, all of which were mild (≤grade 2). The probability of ≥30% excess toxicity over controls at 800 mg was estimated at 0.9%. CONCLUSIONS: Molnupiravir was safe and well tolerated; a dose of 800 mg twice daily for 5 days was recommended for Phase II evaluation.

Quantitation of tizoxanide in multiple matrices to support cell culture, animal and human research.

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.

Pharmacokinetic modelling to estimate intracellular favipiravir ribofuranosyl-5'-triphosphate exposure to support posology for SARS-CoV-2.

OBJECTIVES: Favipiravir has discrepant activity against SARS-CoV-2 in vitro, concerns about teratogenicity and pill burden, and an unknown optimal dose. This analysis used available data to simulate the intracellular pharmacokinetics of the favipiravir active metabolite [favipiravir ribofuranosyl-5'-triphosphate (FAVI-RTP)]. METHODS: Published in vitro data for intracellular production and elimination of FAVI-RTP in Madin-Darby canine kidney cells were fitted with a mathematical model describing the time course of intracellular FAVI-RTP as a function of favipiravir concentration. Parameter estimates were then combined with a published population pharmacokinetic model in Chinese patients to predict human intracellular FAVI-RTP. In vitro FAVI-RTP data were adequately described as a function of concentrations with an empirical model, noting simplification and consolidation of various processes and several assumptions. RESULTS: Parameter estimates from fittings to in vitro data predict a flatter dynamic range of peak to trough for intracellular FAVI-RTP (peak to trough ratio of ∼1 to 1) when driven by a predicted free plasma concentration profile, compared with the plasma profile of parent favipiravir (ratio of ∼2 to 1). This approach has important assumptions, but indicates that, despite rapid clearance of the parent from plasma, sufficient intracellular FAVI-RTP may be maintained across the dosing interval because of its long intracellular half-life. CONCLUSIONS: Population mean intracellular FAVI-RTP concentrations are estimated to be maintained above the Km for the SARS-CoV-2 polymerase for 9 days with a 1200 mg twice-daily regimen (following a 1600 mg twice-daily loading dose on day 1). Further evaluation of favipiravir as part of antiviral combinations for SARS-CoV-2 is warranted.

Scalable nanoprecipitation of niclosamide and in vivo demonstration of long-acting delivery after intramuscular injection.

The control of COVID-19 across the world requires the formation of a range of interventions including vaccines to elicit an immune response and immunomodulatory or antiviral therapeutics. Here, we demonstrate the nanoparticle formulation of a highly insoluble drug compound, niclosamide, with known anti SARS-CoV-2 activity as a cheap and scalable long-acting injectable antiviral candidate.

Development of a highly sensitive bioanalytical assay for the quantification of favipiravir.

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.