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.

Unlike Chloroquine, Mefloquine Inhibits SARS-CoV-2 Infection in Physiologically Relevant Cells.

Despite the development of specific therapies against severe acute respiratory coronavirus 2 (SARS-CoV-2), the continuous investigation of the mechanism of action of clinically approved drugs could provide new information on the druggable steps of virus-host interaction. For example, chloroquine (CQ)/hydroxychloroquine (HCQ) lacks in vitro activity against SARS-CoV-2 in TMPRSS2-expressing cells, such as human pneumocyte cell line Calu-3, and likewise, failed to show clinical benefit in the Solidarity and Recovery clinical trials. Another antimalarial drug, mefloquine, which is not a 4-aminoquinoline like CQ/HCQ, has emerged as a potential anti-SARS-CoV-2 antiviral in vitro and has also been previously repurposed for respiratory diseases. Here, we investigated the anti-SARS-CoV-2 mechanism of action of mefloquine in cells relevant for the physiopathology of COVID-19, such as Calu-3 cells (that recapitulate type II pneumocytes) and monocytes. Molecular pathways modulated by mefloquine were assessed by differential expression analysis, and confirmed by biological assays. A PBPK model was developed to assess mefloquine's optimal doses for achieving therapeutic concentrations. Mefloquine inhibited SARS-CoV-2 replication in Calu-3, with an EC50 of 1.2 µM and EC90 of 5.3 µM. It reduced SARS-CoV-2 RNA levels in monocytes and prevented virus-induced enhancement of IL-6 and TNF-α. Mefloquine reduced SARS-CoV-2 entry and synergized with Remdesivir. Mefloquine's pharmacological parameters are consistent with its plasma exposure in humans and its tissue-to-plasma predicted coefficient points suggesting that mefloquine may accumulate in the lungs. Altogether, our data indicate that mefloquine's chemical structure could represent an orally available host-acting agent to inhibit virus entry.

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.

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.

In vitro antiviral activity of the anti-HCV drugs daclatasvir and sofosbuvir against SARS-CoV-2, the aetiological agent of COVID-19.

BACKGROUND: Current approaches of drug repurposing against COVID-19 have not proven overwhelmingly successful and the SARS-CoV-2 pandemic continues to cause major global mortality. SARS-CoV-2 nsp12, its RNA polymerase, shares homology in the nucleotide uptake channel with the HCV orthologue enzyme NS5B. Besides, HCV enzyme NS5A has pleiotropic activities, such as RNA binding, that are shared with various SARS-CoV-2 proteins. Thus, anti-HCV NS5B and NS5A inhibitors, like sofosbuvir and daclatasvir, respectively, could be endowed with anti-SARS-CoV-2 activity. METHODS: SARS-CoV-2-infected Vero cells, HuH-7 cells, Calu-3 cells, neural stem cells and monocytes were used to investigate the effects of daclatasvir and sofosbuvir. In silico and cell-free based assays were performed with SARS-CoV-2 RNA and nsp12 to better comprehend the mechanism of inhibition of the investigated compounds. A physiologically based pharmacokinetic model was generated to estimate daclatasvir's dose and schedule to maximize the probability of success for COVID-19. RESULTS: Daclatasvir inhibited SARS-CoV-2 replication in Vero, HuH-7 and Calu-3 cells, with potencies of 0.8, 0.6 and 1.1 µM, respectively. Although less potent than daclatasvir, sofosbuvir alone and combined with daclatasvir inhibited replication in Calu-3 cells. Sofosbuvir and daclatasvir prevented virus-induced neuronal apoptosis and release of cytokine storm-related inflammatory mediators, respectively. Sofosbuvir inhibited RNA synthesis by chain termination and daclatasvir targeted the folding of secondary RNA structures in the SARS-CoV-2 genome. Concentrations required for partial daclatasvir in vitro activity are achieved in plasma at Cmax after administration of the approved dose to humans. CONCLUSIONS: Daclatasvir, alone or in combination with sofosbuvir, at higher doses than used against HCV, may be further fostered as an anti-COVID-19 therapy.

Dose prediction for repurposing nitazoxanide in SARS-CoV-2 treatment or chemoprophylaxis.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared a global pandemic and urgent treatment and prevention strategies are needed. Nitazoxanide, an anthelmintic drug, has been shown to exhibit in vitro activity against SARS-CoV-2. 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 SARS-CoV-2 EC90 . METHODS: A whole-body PBPK model was validated against available pharmacokinetic data for healthy individuals receiving single and multiple doses between 500 and 4000 mg with and without food. The validated model was used to predict doses expected to maintain tizoxanide plasma and lung concentrations above the EC90 in >90% of the simulated population. PopDes was used to estimate an optimal sparse sampling strategy for future clinical trials. RESULTS: The PBPK model was successfully validated against the reported human pharmacokinetics. The model predicted optimal doses of 1200 mg QID, 1600 mg TID and 2900 mg BID in the fasted state and 700 mg QID, 900 mg TID and 1400 mg BID when given with food. For BID regimens an optimal sparse sampling strategy of 0.25, 1, 3 and 12 hours post dose was estimated. CONCLUSION: The PBPK model predicted tizoxanide concentrations within doses of nitazoxanide already given to humans previously. The reported dosing strategies provide a rational basis for design of clinical trials with nitazoxanide for the treatment or prevention of SARS-CoV-2 infection. A concordant higher dose of nitazoxanide is now planned for investigation in the seamless phase I/IIa AGILE trial.

Therapeutic Potential of Nitazoxanide: An Appropriate Choice for Repurposing versus SARS-CoV-2?

The rapidly growing COVID-19 pandemic is the most serious global health crisis since the "Spanish flu" of 1918. There is currently no proven effective drug treatment or prophylaxis for this coronavirus infection. While developing safe and effective vaccines is one of the key focuses, a number of existing antiviral drugs are being evaluated for their potency and efficiency against SARS-CoV-2 in vitro and in the clinic. Here, we review the significant potential of nitazoxanide (NTZ) as an antiviral agent that can be repurposed as a treatment for COVID-19. Originally, NTZ was developed as an antiparasitic agent especially against Cryptosporidium spp.; it was later shown to possess potent activity against a broad range of both RNA and DNA viruses, including influenza A, hepatitis B and C, and coronaviruses. Recent in vitro assessment of NTZ has confirmed its promising activity against SARS-CoV-2 with an EC50 of 2.12 µM. Here we examine its drug properties, antiviral activity against different viruses, clinical trials outcomes, and mechanisms of antiviral action from the literature in order to highlight the therapeutic potential for the treatment of COVID-19. Furthermore, in preliminary PK/PD analyses using clinical data reported in the literature, comparison of simulated TIZ (active metabolite of NTZ) exposures at two doses with the in vitro potency of NTZ against SARS-CoV-2 gives further support for drug repurposing with potential in combination chemotherapy approaches. The review concludes with details of second generation thiazolides under development that could lead to improved antiviral therapies for future indications.

The Current Landscape of Novel Formulations and the Role of Mathematical Modeling in Their Development.

Drug delivery is an integral part of the drug development process, influencing safety and efficacy of active pharmaceutical ingredients. The application of nanotechnology has enabled the discovery of novel formulations for numerous therapeutic purposes across multiple disease areas. However, evaluation of novel formulations in clinical scenarios is slow and hampered due to various ethical and logistical barriers. Computational models have the ability to integrate existing domain knowledge and mathematical correlations, to rationalize the feasibility of using novel formulations for safely enhancing drug delivery, identifying suitable candidates, and reducing the burden on preclinical and clinical studies. In this review, types of novel formulations and their application through several routes of administration and the use of modeling approaches that can find application in different stages of the novel formulation development process are discussed.

Prioritization of Anti-SARS-Cov-2 Drug Repurposing Opportunities Based on Plasma and Target Site Concentrations Derived from their Established Human Pharmacokinetics.

There is a rapidly expanding literature on the in vitro antiviral activity of drugs that may be repurposed for therapy or chemoprophylaxis against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). However, this has not been accompanied by a comprehensive evaluation of the target plasma and lung concentrations of these drugs following approved dosing in humans. Accordingly, concentration 90% (EC90 ) values recalculated from in vitro anti-SARS-CoV-2 activity data was expressed as a ratio to the achievable maximum plasma concentration (Cmax ) at an approved dose in humans (Cmax /EC90 ratio). Only 14 of the 56 analyzed drugs achieved a Cmax /EC90 ratio above 1. A more in-depth assessment demonstrated that only nitazoxanide, nelfinavir, tipranavir (ritonavir-boosted), and sulfadoxine achieved plasma concentrations above their reported anti-SARS-CoV-2 activity across their entire approved dosing interval. An unbound lung to plasma tissue partition coefficient (Kp Ulung ) was also simulated to derive a lung Cmax /half-maximal effective concentration (EC50 ) as a better indicator of potential human efficacy. Hydroxychloroquine, chloroquine, mefloquine, atazanavir (ritonavir-boosted), tipranavir (ritonavir-boosted), ivermectin, azithromycin, and lopinavir (ritonavir-boosted) were all predicted to achieve lung concentrations over 10-fold higher than their reported EC50 . Nitazoxanide and sulfadoxine also exceeded their reported EC50 by 7.8-fold and 1.5-fold in lung, respectively. This analysis may be used to select potential candidates for further clinical testing, while deprioritizing compounds 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 lungs, in order to maximize the potential for success of proposed human clinical trials.

Predicting Pharmacokinetics of a Tenofovir Alafenamide Subcutaneous Implant Using Physiologically Based Pharmacokinetic Modelling.

Long-acting (LA) administration using a subcutaneous (s.c.) implant presents opportunities to simplify administration of antiretroviral drugs, improve pharmacological profiles, and overcome suboptimal adherence associated with daily oral formulations. Tenofovir alafenamide (TAF) is a highly potent nucleoside reverse transcriptase inhibitor (NRTI) and an attractive agent for LA delivery, with a high potency and long intracellular half-life. The aim of this study was to predict minimum TAF doses required to achieve concentrations effective for HIV preexposure prophylaxis (PrEP). Daily drug release requirements were then ascertained by averaging across the dosing interval. A TAF physiologically based pharmacokinetic (PBPK) model was developed and partially qualified against available oral single- and multiple-dose pharmacokinetics. The models were assumed to be qualified when simulated values were within 2-fold of the observed mean. TAF s.c. implants were simulated in five hundred individuals, reporting predicted TAF plasma and tenofovir (TFV) plasma concentrations for various release rates. Intracellular TFV diphosphate (TFV-DP) concentrations were also simulated in peripheral blood cells and cervical and rectal tissues. The minimum dose predicted to achieve intracellular TFV-DP levels above a target concentration of 48 fmol/106 cells for a month was identified. TAF, TFV, and TFV-DP concentrations for release rates between 1.0 and 1.6 mg/day were simulated. The PBPK model indicated that a minimum release of 1.4 mg/day TAF is necessary to achieve TFV-DP concentrations above the identified target in peripheral blood mononuclear cells (PBMCs). TFV-DP cervical and rectal tissue concentrations were predicted to be between 1.5 and 2.0 fmol/106 cells and 0.9 and 1.1 fmol/106 cells, respectively, for release rates between 1.3 and 1.6 mg/day. These simulations provide target minimum doses for LA TAF PrEP in humans. Based on the generated results, multiple implants delivering a total of 1.4 mg/day of TAF subcutaneously could provide protection levels for approximately 6 months to 1 year. This modeling may inform future design of s.c. implants to mitigate adherence issues for effective PrEP applications.

Prediction of dolutegravir pharmacokinetics and dose optimization in neonates via physiologically based pharmacokinetic (PBPK) modelling.

BACKGROUND: Only a few antiretroviral drugs (ARVs) are recommended for use during the neonatal period and there is a need for more to be approved to increase treatment and prophylaxis strategies. Dolutegravir, a selective integrase inhibitor, has potential for treatment of HIV infection and prophylaxis of transmission in neonates. OBJECTIVES: To model the pharmacokinetics of dolutegravir in neonates and to simulate a theoretical optimal dosing regimen. METHODS: The physiologically based pharmacokinetic (PBPK) model was built incorporating the age-related changes observed in neonates. Virtual neonates between 0 and 28 days were simulated. The model was validated against observed clinical data for raltegravir and midazolam in neonates, prior to the prediction of dolutegravir pharmacokinetics. RESULTS: Both raltegravir and midazolam passed the criteria for model qualification, with simulated data within 1.8-fold of clinical data. The qualified model predicted the pharmacokinetics for several multidose regimens of dolutegravir. Regimen 6 involved 5 mg doses with a 48 h interval from Day 1-20, increasing to 5 mg once daily on Week 3, yielding AUC and Ctrough values of 37.2 mg·h/L and 1.3 mg/L, respectively. These exposures are consistent with those observed in paediatric patients receiving dolutegravir. CONCLUSIONS: Dolutegravir pharmacokinetics were successfully simulated in the neonatal PBPK model. The predictions suggest that during the first 3 weeks of life a 5 mg dose administered every 48 h may achieve plasma exposures needed for therapy and prophylaxis.

Physiologically-Based Pharmacokinetic Modeling for Optimal Dosage Prediction of Quinine Coadministered With Ritonavir-Boosted Lopinavir.

The coformulated lopinavir/ritonavir significantly reduces quinine concentration in healthy volunteers due to potential drug-drug interactions (DDIs). However, DDI information in malaria and HIV coinfected patients are lacking. The objective of the study was to apply physiologically-based pharmacokinetic (PBPK) modeling to predict optimal dosage regimens of quinine when coadministered with lopinavir/ritonavir in malaria and HIV coinfected patients with different conditions. The developed model was validated against literature. Model verification was evaluated using the accepted method. The verified PBPK models successfully predicted unbound quinine disposition when coadministered with lopinavir/ritonavir in coinfected patients with different conditions. Suitable dose adjustments to counteract with the DDIs have identified in patients with various situations (i.e., a 7-day course at 1,800 mg t.i.d. in patients with malaria with HIV infection, 648 mg b.i.d. in chronic renal failure, 648 mg t.i.d. in hepatic insufficiency except for severe hepatic insufficiency (324 mg b.i.d.), and 648 mg t.i.d. in CYP3A4 polymorphism).

Modelling the intradermal delivery of microneedle array patches for long-acting antiretrovirals using PBPK.

INTRODUCTION: Existing HIV therapy using oral antiretrovirals (ARVs) can result in pill fatigue and sub-optimal adherence. Microneedle array patches (MAPs) offer non-invasive, blood-free and painless drug delivery, and may improve patient adherence. The objective of this study was to develop a novel physiologically-based pharmacokinetic (PBPK) model to simulate the systemic pharmacokinetics of cabotegravir and rilpivirine MAPs using the intradermal route. METHODS: The developed PBPK models were qualified against observed pharmacokinetic data after intramuscular (IM) and intradermal administration of long-acting nanoformulated rilpivirine to rats, and for IM administration of both drugs to healthy adults. Qualified models were then utilised to estimate suitable MAP characteristics (e.g. nanoformulation dose and release rates) and inform dosing strategies to maintain plasma concentrations above target trough concentrations for the designated dosing interval. RESULTS: PBPK models simulated q4-weekly loading and maintenance doses of 360 mg and 180 mg for long-acting formulated cabotegravir between the release rates of 1 × 10-3-3 × 10-3h-1 and 1 × 10-3-1.5 × 10-3h-1 respectively, for a 70 kg adult. Estimated patch size was 60 cm2 for a 360 mg dose of cabotegravir. For q4-weekly dosing, rilpivirine required a 1080 mg loading dose and a 540 mg maintenance dose with release rates of 1.5 × 10-3-2.5 × 10-3h-1 and 5 × 10-4-1 × 10-3h-1, respectively. Weekly dosing was also evaluated to assess the potential application from a smaller patch size. The ability to self-administer via a patch that is only left in place for a short duration makes longer durations less important than for some other long-acting approaches. Weekly cabotegravir required 60 mg between release rates 7 × 10-3-9 × 10-3h-1 and rilpivirine required 270 mg and 180 mg respectively between release rates of 7 × 10-3-9 × 10-3h-1. DISCUSSION: This model estimated optimal dose and release rates for cabotegravir and rilpivirine MAPs. Our approach provides a computational platform to support rational development of intradermal administration strategies to tackle problems associated with chronic oral ARV administration.

Using mechanistic physiologically-based pharmacokinetic models to assess prenatal drug exposure: Thalidomide versus efavirenz as case studies.

Maternofoetal physiologically-based pharmacokinetic models integrating multi-compartmental maternal and foetal units were developed using Simbiology® to estimate prenatal drug exposure. Processes governing drug disposition were described using differential equations with key system and drug-specific parameters. Transplacental drug transfer was modelled as bidirectional passive diffusion and benchmarked against those for thalidomide as a control. Model-predictions for pharmacokinetic parameters during pregnancy were within acceptable ranges for qualification (two-fold difference of clinically-observed values). Predicted foetal exposure to thalidomide was higher than efavirenz, with median (range) foetal-to-maternal plasma ratios of 4.55 (3.06-9.57) for 400 mg thalidomide versus 0.89 (0.73-1.05) for 400 mg efavirenz at third trimester. Model-predictions indicated foetal exposure consistently above 300% of maternal plasma concentration for thalidomide throughout pregnancy, while exposure to efavirenz increased from under 20% at second trimester to above 100% at third trimester. Further qualification of this approach as a tool in evaluating drug exposure and safety during pregnancy is warranted.