Biological Obstacles for Identifying In Vitro-In Vivo Correlations of Orally Inhaled Formulations

Preclinical concept studies showing advantage of an inhaled anti-CTGF/CCN2 protein for pulmonary fibrosis treatment

Inhaled therapeutics have high potential for the treatment of chronic respiratory diseases of high unmet medical need, such as idiopathic pulmonary fibrosis (IPF). Preclinical and early clinical evidence show that cellular communication network factor 2 (CCN2), previously called connective tissue growth factor (CTGF), is a promising target for the treatment of IPF. In recent phase 3 clinical trials, however, systemic CCN2 inhibition failed to demonstrate a clinically meaningful benefit. Here, we present the preclinical profile of the inhaled anti-CCN2 Anticalin® protein PRS-220. Our study demonstrates that efficient pulmonary delivery directly translates into superior efficacy in relevant models of pulmonary fibrosis when compared to systemic CCN2 inhibition. Moreover, we present a holistic approach for the preclinical characterization of inhaled PRS-220 from state-of-the art in vitro and in vivo models to novel human ex vivo and in silico models, highlighting the advantage of inhaled drug delivery for treatment of respiratory disease.

Nebulized 2-deoxylated glucose analogues inhibit respiratory viral infection in advanced in vitro airway models

Respiratory viral infections, such as those caused by rhinoviruses (RVs) and human corona viruses (HCoV), result in a serious strain on healthcare systems and public health, underscoring an urgent need for inhaled broad-spectrum antiviral therapies. However, their development is challenging, as no standardized in vitro methodologies that can fully replicate the in vivo environment have been established. In this work, we aimed to investigate the antiviral and anti-inflammatory effect of three 2-deoxylated glucose analogues (2-DGA): 2-deoxy-D-glucose, 2-fluoro-2-deoxy-D-glucose and 2-fluoro-2-deoxy-D-mannose (2-FDM), by utilizing advanced in vitro air-liquid interface (ALI) airway models. We demonstrated that commonly used ALI models have variable susceptibility to RV, HCoV and influenza A virus (IAV) infection. Further, we showed that 2-DGA have an anti-inflammatory effect and suppress respiratory viral replication in models mimicking the upper and lower respiratory airways. Moreover, we confirmed that 2-DGA can be delivered via nebulization in vitro, highlighting their potential to be used as broad-spectrum inhaled antivirals. Finally, our results demonstrate the importance of incorporating complex in vitro methodologies, such as primary cell ALI cultures and aerosol exposure, at an early stage of drug development.

A novel in vitro high-content imaging assay for the prediction of drug-induced lung toxicity

The development of inhaled drugs for respiratory diseases is frequently impacted by lung pathology in non-clinical safety studies. To enable design of novel candidate drugs with the right safety profile, predictive in vitro lung toxicity assays are required that can be applied during drug discovery for early hazard identification and mitigation. Here, we describe a novel high-content imaging-based screening assay that allows for quantification of the tight junction protein occludin in A549 cells, as a model for lung epithelial barrier integrity. We assessed a set of compounds with a known lung safety profile, defined by clinical safety or non-clinical in vivo toxicology data, and were able to correctly identify 9 of 10 compounds with a respiratory safety risk and 9 of 9 compounds without a respiratory safety risk (90% sensitivity, 100% specificity). The assay was sensitive at relevant compound concentrations to influence medicinal chemistry optimization programs and, with an accessible cell model in a 96-well plate format, short protocol and application of automated imaging analysis algorithms, this assay can be readily integrated in routine discovery safety screening to identify and mitigate respiratory toxicity early during drug discovery. Interestingly, when we applied physiologically-based pharmacokinetic (PBPK) modelling to predict epithelial lining fluid exposures of the respiratory tract after inhalation, we found a robust correlation between in vitro occludin assay data and lung pathology in vivo, suggesting the assay can inform translational risk assessment for inhaled small molecules.

A Monoclonal Human Alveolar Epithelial Cell Line ("Arlo") with Pronounced Barrier Function for Studying Drug Permeability and Viral Infections

In the development of orally inhaled drug products preclinical animal models regularly fail to predict pharmacological as well as toxicological responses in humans. Models based on human cells and tissues are potential alternatives to animal experimentation allowing for the isolation of essential processes of human biology and making them accessible in vitro. Here, the generation of a novel monoclonal cell line "Arlo," derived from the polyclonal human alveolar epithelium lentivirus immortalized cell line hAELVi via single-cell printing, and its characterization as a model for the human alveolar epithelium as well as a building block for future complex in vitro models is described. "Arlo" is systematically compared in vitro to primary human alveolar epithelial cells (hAEpCs) as well as to the polyclonal hAELVi cell line. "Arlo" cells show enhanced barrier properties with high transepithelial electrical resistance (TEER) of ≈3000 Ω cm2 and a potential difference (PD) of ≈30 mV under air-liquid interface (ALI) conditions, that can be modulated. The cells grow in a polarized monolayer and express genes relevant to barrier integrity as well as homeostasis as is observed in hAEpCs. Successful productive infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a proof-of-principle study offers an additional, attractive application of "Arlo" beyond biopharmaceutical experimentation.

Drivers of absolute systemic bioavailability after oral pulmonary inhalation in humans

There are few studies in humans dealing with the relationship between physico-chemical properties of drugs and their systemic bioavailability after administration via oral inhalation route (Fpulm). Getting further insight in the determinants of Fpulm after oral pulmonary inhalation could be of value for drugs considered for a systemic delivery as a result of poor oral bioavailability, as well as for drugs considered for a local delivery to anticipate their undesirable systemic effects. To better delineate the parameters influencing the systemic delivery after oral pulmonary inhalation in humans, we studied the influence of physico-chemical and permeability properties obtained in silico on the rate and extent of Fpulm in a series of 77 compounds with or without marketing approval for pulmonary delivery, and intended either for local or for systemic delivery. Principal component analysis (PCA) showed mainly that Fpulm was positively correlated with Papp and negatively correlated with %TPSA, without a significant influence of solubility and ionization fraction, and no apparent link with lipophilicity and drug size parameters. As a result of the small sample set, the performance of the different models as predictive of Fpulm were quite average with random forest algorithm displaying the best performance. As a whole, the different models captured between 50 and 60% of the variability with a prediction error of less than 20%. Tmax data suggested a significant positive influence of lipophilicity on absorption rate while charge apparently had no influence. A significant linear relationship between Cmax and dose (R² = "0.79) highlighted that Cmax was primarily dependent on dose and absorption rate and could be used to estimate Cmax in humans for new inhaled drugs.

A review on chitosan and its development as pulmonary particulate anti-infective and anti-cancer drug carriers

Chitosan, as a biodegradable and biocompatible polymer, is characterized by anti-microbial and anti-cancer properties. It lately has received a widespread interest for use as the pulmonary particulate backbone materials of drug carrier for the treatment of infectious disease and cancer. The success of chitosan as pulmonary particulate drug carrier is a critical interplay of their mucoadhesive, permeation enhancement and site/cell-specific attributes. In the case of nanocarriers, various microencapsulation and micro-nano blending systems have been devised to equip them with an appropriate aerodynamic character to enable efficient pulmonary aerosolization and inhalation. The late COVID-19 infection is met with acute respiratory distress syndrome and cancer. Chitosan and its derivatives are found useful in combating HCoV and cancer as a function of their molecular weight, substituent type and its degree of substitution. The interest in chitosan is expected to rise in the next decade from the perspectives of drug delivery in combination with its therapeutic performance.

In vitro-in vivo correlations (IVIVCs) of deposition for drugs given by oral inhalation

Conventional in vitro tests to assess the aerodynamic particle size distribution (APSD) from inhaler devices use simple right-angle inlets ("mouth-throats", MTs) to cascade impactors, and air is drawn through the system at a fixed flow for a fixed time. Since this arrangement differs substantially from both human oropharyngeal airway anatomy and the patterns of air flow when patients use inhalers, the ability of in vitro tests to predict in vivo deposition of pharmaceutical aerosols has been limited. MTs that mimic the human anatomy, coupled with simulated breathing patterns, have yielded estimates of lung dose from in vitro data that closely match those from in vivo gamma scintigraphic or pharmacokinetic studies. However, different models of MTs do not always yield identical data, and selection of an anatomical MT and representative inhalation profiles remains challenging. Improved in vitro - in vivo correlations (IVIVCs) for inhaled drug products could permit increased reliance on in vitro data when developing new inhaled drug products, and could ultimately result in accelerated drug product development, together with reduced research and development spending.

Preclinical Development of Orally Inhaled Drugs (OIDs)-Are Animal Models Predictive or Shall We Move Towards In Vitro Non-Animal Models?

Respiratory diseases constitute a huge burden in our society, and the global respiratory drug market currently grows at an annual rate between 4% and 6%. Inhalation is the preferred administration method for treating respiratory diseases, as it: (i) delivers the drug directly at the site of action, resulting in a rapid onset; (ii) is painless, thus improving patients' compliance; and (iii) avoids first-pass metabolism reducing systemic side effects. Inhalation occurs through the mouth, with the drug generally exerting its therapeutic action in the lungs. In the most recent years, orally inhaled drugs (OIDs) have found application also in the treatment of systemic diseases. OIDs development, however, currently suffers of an overall attrition rate of around 70%, meaning that seven out of 10 new drug candidates fail to reach the clinic. Our commentary focuses on the reasons behind the poor OIDs translation into clinical products for the treatment of respiratory and systemic diseases, with particular emphasis on the parameters affecting the predictive value of animal preclinical tests. We then review the current advances in overcoming the limitation of animal animal-based studies through the development and adoption of in vitro, cell-based new approach methodologies (NAMs).

Development of an In Vitro System to Study the Interactions of Aerosolized Drugs with Pulmonary Mucus

Mucus is the first biological component inhaled drugs encounter on their journey towards their pharmacological target in the upper airways. Yet, how mucus may influence drug disposition and efficacy in the lungs has been essentially overlooked. In this study, a simple in vitro system was developed to investigate the factors promoting drug interactions with airway mucus in physiologically relevant conditions. Thin layers of porcine tracheal mucus were prepared in Transwell^® inserts and initially, the diffusion of various fluorescent dyes across those layers was monitored over time. A deposition system featuring a MicroSprayer^® aerosolizer was optimized to reproducibly deliver liquid aerosols to multiple air-facing layers and then exploited to compare the impact of airway mucus on the transport of inhaled bronchodilators. Both the dyes and drugs tested were distinctly hindered by mucus with high logP compounds being the most affected. The diffusion rate of the bronchodilators across the layers was in the order: ipratropium ≈ glycopyronnium > formoterol > salbutamol > indacaterol, suggesting hydrophobicity plays an important role in their binding to mucus but is not the unique parameter involved. Testing of larger series of compounds would nevertheless be necessary to better understand the interactions of inhaled drugs with airway mucus.