Preferences of Patients and Providers in High-Burden Malaria Settings for Long-Acting Malaria Chemoprevention.

Antimalarial medications are recommended for chemoprevention as part of malaria control programs to decrease the morbidity and mortality related to more than 200 million infections each year. We sought to evaluate patient and provider acceptability of malaria chemoprevention in a long-acting formulation. We administered questionnaires to patients and providers in malaria endemic districts in Kenya and Zambia. Questions explored preferences and concerns around long-acting antimalarial formulations compared with oral formulations. We recruited 202 patient respondents (Kenya, n = 102; Zambia, n = 100) and 215 provider respondents (Kenya, n = 105; Zambia, n = 110). Long-acting injection was preferred to oral pills, whereas oral pills were preferred to implant or transdermal administration by patient respondents. Of 202 patient respondents, 80% indicated that they 'definitely would try' malaria chemoprevention offered by injection instead of oral pills. Of parents or guardians, 84% of 113 responded that they 'definitely would' have their child age < 12 years and 90% of 88 'definitely would' have their child ≥12 years receive an injection for malaria prevention. Provider respondents indicated that they would be more likely to prescribe a long-acting injectable product compared with an oral product for malaria chemoprevention in adults (70%), adolescents ages 12 years and older (67%), and children <12 years (81%). Potential for prolonged adverse effects with long-acting products was the highest concern for patient respondents, while higher medication-related cost was cited as the most concerning barrier to implementation by providers. Overall, these findings indicate enthusiasm for the development of long-acting injectable antimalarials to provide individual delivery method options across age groups.

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.

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.

Towards a Maraviroc long-acting injectable nanoformulation.

Suboptimal adherence to antiretroviral (ARV) therapy can lead to insufficient drug exposure leading to viral rebound and increased likelihood of resistance. This has driven the development of long-acting injectable (LAI) formulations which may mitigate some of these problems. Maraviroc (MVC) is an orally dosed CCR5 antagonist approved for use in patients infected with CCR5-trophic HIV-1. MVC prevents viral entry into host cells, is readily distributed to biologically relevant tissues and has an alternative resistance profile compared to more commonly used therapies. This makes a MVC LAI formulation particularly appealing for implementation in Pre-Exposure Prophylaxis (PrEP). A 70 wt% MVC-loaded nanodispersion stabilised with polyvinyl alcohol (PVA) and sodium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate (AOT) was prepared using emulsion-templated freeze-drying. In vitro release rate studies revealed over a 22% decrease in MVC release rate constant across a size selective membrane compared with an aqueous solution of MVC (<5% DMSO). Pharmacokinetic studies in rats were subsequently carried out following intramuscular injection of either the nanodispersion or an aqueous MVC preparation (<5% DMSO). Results demonstrated over a 3.4-fold increase in AUC0-∞ (1959.71 vs 567.17 ng.h ml), over a 2.6-fold increase in MVCs terminal half-life (t½) (140.69 vs 53.23 h) and MVC concentrations present up to 10-days. These data support development of a MVC LAI formulation with potential application in HIV therapy or prevention.

Lack of interaction of lopinavir solid drug nanoparticles with cells of the immune system.

AIM: We previously demonstrated that solid drug nanoparticles (SDNs) lopinavir (LPV) dispersed into aqueous media display favorable pharmacokinetics. METHODS: The impact of LPV SDNs on the function and phenotype of primary human T cells and macrophages (primary sites of HIV replication) was investigated. RESULTS: LPV significantly increased IL-1ß (ninefold higher than untreated cells; p = 0.045) and TNF-α (sixfold higher than untreated cells; p = 0.018) secretion from monocyte-derived macrophages, whereas LPV SDNs did not elicit these responses at comparable drug concentrations. LPV SDNs were demonstrated to be immunologically inert to human T cells and monocyte-derived macrophages. CONCLUSION: The LPV SDN was demonstrated to exhibit comparable, or favorable behavior compared with an LPV aqueous solution in the employed biocompatibility assessments.

Synthesis and in vivo magnetic resonance imaging evaluation of biocompatible branched copolymer nanocontrast agents.

Branched copolymer nanoparticles (D(h) =20-35 nm) possessing 1,4,7, 10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid macrocycles within their cores have been synthesized and applied as magnetic resonance imaging (MRI) nanosized contrast agents in vivo. These nanoparticles have been generated from novel functional monomers via reversible addition-fragmentation chain transfer polymerization. The process is very robust and synthetically straightforward. Chelation with gadolinium and preliminary in vivo experiments have demonstrated promising characteristics as MRI contrast agents with prolonged blood retention time, good biocompatibility, and an intravascular distribution. The ability of these nanoparticles to perfuse and passively target tumor cells through the enhanced permeability and retention effect is also demonstrated. These novel highly functional nanoparticle platforms have succinimidyl ester-activated benzoate functionalities within their corona, which make them suitable for future peptide conjugation and subsequent active cell-targeted MRI or the conjugation of fluorophores for bimodal imaging. We have also demonstrated that these branched copolymer nanoparticles are able to noncovalently encapsulate hydrophobic guest molecules, which could allow simultaneous bioimaging and drug delivery.

Augmented Inhibition of CYP3A4 in Human Primary Hepatocytes by Ritonavir Solid Drug Nanoparticles.

Ritonavir is a protease inhibitor utilized primarily as a pharmaco-enhancer with concomitantly administered antiviral drugs including other protease inhibitors. However, poor tolerance, serious side effects, and toxicities associated with drug-drug interactions are common during exposure to ritonavir. The aim of this work was to investigate the impact of nanoformulation on ritonavir pharmacological properties. Emulsion-templated freeze-drying techniques were used to generate ritonavir (10 wt %) solid drug nanoparticle formulations. A total of 68 ritonavir formulations containing various mixtures of excipients were assessed for inhibition of CYP3A4 in baculosomes and primary human hepatocytes. Accumulation and cytotoxicity were assessed in HepG2 (hepatocytes), Caco-2 (intestinal), THP-1 (monocytes), A-THP-1 (macrophage), and CEM (lymphocytes). Transcellular permeation across Caco-2 cells was also assessed. From 68 solid drug nanoparticle formulations tested, 50 (73.5%) for baculosome and 44 (64.7%) for human primary hepatocytes exhibited enhanced CYP3A4 inhibition relative to an aqueous ritonavir solution. Sixty-one (89.7%) and 49 (72%) solid drug nanoformulations had higher apical to basal permeation across Caco-2 cells than aqueous solution of ritonavir after 60 and 120 min, respectively. No significant difference in cellular accumulation was observed for any solid drug nanoparticle for any cell type compared to aqueous ritonavir. However, incubation with the vast majority of solid drug nanoparticle formulations resulted in lower cytotoxicity of ritonavir than detected with an aqueous solution. These data provide in vitro proof of concept for improved inhibition of CYP3A4 by ritonavir through formation of solid drug nanoparticles. Nanodispersions also showed enhanced permeability across Caco-2 cells lower cytotoxicity across hepatic, intestinal, and immune cell types compared to an aqueous solution of ritonavir.

Nanoformulation strategies for the enhanced oral bioavailability of antiretroviral therapeutics.

The oral delivery of drugs with poor aqueous solubility is challenging and often results in poor bioavailability. Various nanoformulation platforms have demonstrated improved oral bioavailability of a range of drugs for different indications. The focus of this review is to provide an overview of the application of nanomedicine to oral antiretroviral therapy and outline how the current short-falls of this life-long therapy may be resolved using nanotechnology. As well as highlighting the rationale for a nanomedicine-based approach, the review focuses on the various strategies used to enhance oral bioavailability and describes the mechanisms of particle absorption across the GI tract. The recent advances in the development of long-acting formulations for both HIV treatment and pre-exposure prophylaxis are also discussed.

Hyperbranched polydendrons: a new nanomaterials platform with tuneable permeation through model gut epithelium.

The development of nanomaterials for advanced therapies requires the formation of versatile platforms that may be tuned to maximize beneficial attributes and minimize unwanted negative behaviour. Additionally, the optimum route of administration is a key consideration of any new treatment and much work has been focused on direct injection into the systemic circulation rather than oral delivery. Here we describe a new approach to polymeric nanoparticle design and present initial results showing the potential for tuneable permeation through a gut epithelium model. Through the use of mixed initiators and branched vinyl polymerization, a series of systematically varying branched polymers have been synthesized and nanoprecipitated. The surprisingly uniform structures have undergone preliminary pharmacological evaluation to establish low cytotoxicity and enhanced permeation through model intestinal epithelial cells. This presents potential opportunities for future developments that may allow oral dosing to result in circulating polymeric nanoparticles; behaviour that may prove clinically desirable to many non-terminal or chronic diseases that utilise nanomedicines but wish to avoid regular or repeated intravenous administration.

The first peripherally masked thiol dendrimers: a facile and highly efficient functionalization strategy of polyester dendrimers via one-pot xanthate deprotection/thiol-acrylate Michael addition reactions.

Introducing multiple reactive functional groups at the periphery of dendrimer materials presents considerable challenges if the functionality is able to self-react. An efficient and facile approach to introducing masked thiols at the surface of polyester dendrimers is presented. One-pot, deprotection/thiol-acrylate Michael addition from the xanthate-functional dendritic substrates (generation zero to two) has been achieved for the first time, with high efficiency demonstrated using three acrylates of varying chemistry and avoiding disulfide formation.

Antiretroviral solid drug nanoparticles with enhanced oral bioavailability: production, characterization, and in vitro-in vivo correlation.

Nanomedicine strategies have produced many commercial products. However, no orally dosed HIV nanomedicines are available clinically to patients. Although nanosuspensions of drug particles have demonstrated many benefits, experimentally achieving >25 wt% of drug relative to stabilizers is highly challenging. In this study, the emulsion-templated freeze-drying technique for nanoparticles formation is applied for the first time to optimize a nanodispersion of the leading non-nucleoside reverse transcriptase inhibitor efavirenz, using clinically acceptable polymers and surfactants. Dry monoliths containing solid drug nanoparticles with extremely high drug loading (70 wt% relative to polymer and surfactant stabilizers) are stable for several months and reconstitute in aqueous media to provide nanodispersions with z-average diameters of 300 nm. The solid drug nanoparticles exhibit reduced cytoxicity and increased in vitro transport through model gut epithelium. In vivo studies confirm bioavailability benefits with an approximately four-fold higher pharmacokinetic exposure after oral administration to rodents, and predictive modeling suggests dose reduction with the new formulation may be possible.

Mediation of in vitro cytochrome p450 activity by common pharmaceutical excipients.

Polymers and surfactants are commonly used as excipients in oral formulations and are generally considered to be inert. However, relatively few studies have assessed their interaction with enzymes involved in the absorption, distribution, metabolism, and elimination of drugs. We have investigated the impact of twenty-three commonly used excipients (ten polymers and thirteen surfactants) on seven cytochrome P450 (CYP450) isoforms using baculosome-derived CYP450 enzymes across a range of concentrations. Time-course fluorescent readings were then taken to generate IC50 (inhibition) or EC50 (activation) values for excipient effects on CYP450 activity. All excipients had an observable effect activity of at least one CYP450 isoform with the majority of excipients altering substrate metabolism of at least 57% of CYP450s studied. In addition, most excipients were capable of inhibiting and increasing activity of several different CYP450 isoforms. Although the majority of these effects required concentrations outside those achievable therapeutically (>100 µM), almost 20% were seen at concentrations below 100 µM, and these results indicate that several excipients have the potential to modify the pharmacokinetics of administered drugs.

Polymer-mediated hierarchical and reversible emulsion droplet assembly.

Making and breaking: Stable, functional micrometer-sized emulsion droplets can be assembled into various complex macroscopic liquid structures (see picture). The hierarchical assembly process is mediated by interactions between polymeric surfactant molecules located on the droplet surfaces. These interdroplet interactions are reversible, therefore these "engineered emulsions" can be readily disassembled by using a simple pH switch.

Formation and enhanced biocidal activity of water-dispersable organic nanoparticles.

Water-insoluble organic compounds are often used in aqueous environments in various pharmaceutical and consumer products. To overcome insolubility, the particles are dispersed in a medium during product formation, but large particles that are formed may affect product performance and safety. Many techniques have been used to produce nanodispersions-dispersions with nanometre-scale dimensions-that have properties similar to solutions. However, making nanodispersions requires complex processing, and it is difficult to achieve stability over long periods. Here we report a generic method for producing organic nanoparticles with a combination of modified emulsion-templating and freeze-drying. The dry powder composites formed using this method are highly porous, stable and form nanodispersions upon simple addition of water. Aqueous nanodispersions of Triclosan (a commercial antimicrobial agent) produced with this approach show greater activity than organic/aqueous solutions of Triclosan.

pH-Responsive branched polymernanoparticles.

We describe a new one-pot, single-step route for the preparation of pH-responsive branched polymer nanoparticles. These polymers, which are based on the pH-responsive monomer 2-(diethylamino)ethyl methacrylate (DEA) and hydrophilic macromonomer poly(ethyleneglycol) methacrylate (PEGMA), are synthesised using a modified conventional free-radical polymerisation. Consequently, their preparation is generic, scaleable and tolerant of functionality. In aqueous solution the branched copolymers form core-shell structures at basic pH and on reducing the solution pH they become hydrated and swell, displaying similar characteristics to those of pH-responsive shell cross-linked micelles and microgels. We demonstrate good control over the hydrodynamic particle size, polymer chain-end, and the uptake and release of a model hydrophobe and also the ability to tune the apparent pKa of the DEA residues by varying the degree of branching. These results augur well for commercially viable tunable release applications.

Structure-LCST relationships for end-functionalized water-soluble polymers: an "accelerated" approach to phase behaviour studies.

A novel "high throughput" technique for LCST measurement was developed which is able to identify the effect of subtle changes in end group composition on the aqueous phase behaviour of water-soluble poly(2-(dimethylamino)ethyl methacrylate).

Synthesis of well-defined Locust Bean Gum-graft-copolymers using ambient aqueous atom transfer radical polymerisation.

The first atom transfer radical graft copolymerisation at ambient temperature in water from a soluble polysaccharide is demonstrated for a range of monomer types.