Pulmonary delivery of dry powders to rats: tolerability limits of an intra-tracheal administration model

Nebulised delivery of RNA formulations to the lungs: From aerosol to cytosol

In the past decade RNA-based therapies such as small interfering RNA (siRNA) and messenger RNA (mRNA) have emerged as new and ground-breaking therapeutic agents for the treatment and prevention of many conditions from viral infection to cancer. Most clinically approved RNA therapies are parenterally administered which impacts patient compliance and adds to healthcare costs. Pulmonary administration via inhalation is a non-invasive means to deliver RNA and offers an attractive alternative to injection. Nebulisation is a particularly appealing method due to the capacity to deliver large RNA doses during tidal breathing. In this review, we discuss the unique physiological barriers presented by the lung to efficient nebulised RNA delivery and approaches adopted to circumvent this problem. Additionally, the different types of nebulisers are evaluated from the perspective of their suitability for RNA delivery. Furthermore, we discuss recent preclinical studies involving nebulisation of RNA and analysis in in vitro and in vivo settings. Several studies have also demonstrated the importance of an effective delivery vector in RNA nebulisation therefore we assess the variety of lipid, polymeric and hybrid-based delivery systems utilised to date. We also consider the outlook for nebulised RNA medicinal products and the hurdles which must be overcome for successful clinical translation. In summary, nebulised RNA delivery has demonstrated promising potential for the treatment of several lung-related conditions such as asthma, COPD and cystic fibrosis, to which the mode of delivery is of crucial importance for clinical success.

Performance Testing of a Homemade Aerosol Generator for Pulmonary Administration of Dry Powder Formulations to Mice

A challenge in the development of dry powder formulations for inhalation is the poor reproducibility of their administration to small laboratory animals. The currently used devices for the pulmonary administration of dry powder formulations to small rodents often function sub-optimally as they use the same puff of air for both powder dispersion and aerosol delivery. As a result, either the air volume and flow rate are too low for complete powder deagglomeration or they are too high for effective aerosol delivery to the lungs of the animal. Therefore, novel and better devices are desired. We here present an aerosol generator designed to administer a pre-generated aerosol to the lungs of mice. By mapping the complex relationship between the airflow rate, delivery time and emitted dose, we were able to control the amount of powder being delivered from the aerosol generator. The emitted aerosol had a size range favorable for lung deposition and could be measured reproducibly. Nevertheless, in vivo fluorescent imaging still revealed considerable differences between the mice in terms of the dose deposited and the distribution of powder over the lungs, suggesting that a certain biological variation in lung deposition is inevitable.

Pulmonary drug delivery technology enables anakinra repurposing in cystic fibrosis

Inflammation is a key pathological driver in cystic fibrosis (CF). Current therapies are ineffective in treating and preventing the escalation of inflammatory events often exacerbated by superimposed infection. In this work, we propose a novel treatment based on the pulmonary administration of anakinra, a non-glycosylated recombinant form of IL-1Ra. An inhalable dry powder of anakinra was successfully developed to meet the specific needs of lung drug delivery. The new formulation was investigated in vitro for aerodynamic performances and activity and in vivo for its pharmacological profile, including the pharmacokinetics, treatment schedule, antimicrobial and anti-inflammatory activity and systemic toxicity. The protein was structurally preserved inside the formulation and retained its pharmacological activity in vitro immediately after preparation and over time when stored at ambient conditions. Anakinra when delivered to the lungs showed an improved and extended therapeutic efficacy in CF models in vivo as well as higher potency compared to systemic delivery. Peripheral side effects were significantly reduced and correlated with lower serum levels compared to systemic treatment. These findings provide proof-of-concept demonstration for anakinra repurposing in CF through the pulmonary route.

Evaluation of Phage Therapy for Pulmonary Infection of Mouse by Liquid Aerosol-Exposure Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an important nosocomial infectious bacterium, more and more multidrug resistant P. aeruginosa have been isolated and posed severe challenges to clinical antibiotic treatment, bringing additional morbidity, mortality, and economic burden. Bacteriophages can lyse bacteria specificity and are feasible alternatives to antibiotics.

METHODS

A Pseudomonas aeruginosa-infecting phage vB_PaeP_PA01EW was isolated. Phage plaque assays, transmission electron microscopy, host-range determination, infection assay analyses, whole-genome sequencing and annotation were performed for the phage. Mice pneumonia model using liquid aerosol-exposure Pseudomonas aeruginosa was established, and phage therapy was evaluated.

RESULTS

vB_PaeP_PA01EW belongs to the family Podoviridae according to transmission electron microscopy and was identified as a Luz24likevirus according to the genome analysis. For the phage therapy, compared with the bacteria-infected group, the phage-rescue group has some characteristics. First, adventitial edema and diffuse infiltration of inflammatory cells in tissues were alleviated, Second, bronchial epithelial cell proliferation was reduced. Third, the bacterial burden was significantly decreased.

CONCLUSION

This study provided data support and theoretical basis for the clinical application of bacteriophages. It has important guiding significance and reference value for the application of bacteriophage therapy of other pathogenic bacteria.

Studies on the safety and the tissue distribution of inhaled high-dose amorphous and crystalline rifampicin in a rat model

Inhaled delivery of rifampicin has the potential to achieve high drug concentrations in the lung and the blood for efficient treatment of tuberculosis (TB). Due to its existence as polymorphs, in vivo evaluation of the respiratory tract safety of inhalable amorphous and crystalline rifampicin particles, at clinically relevant high-dose, is necessary. This study investigates the lung and liver safety and the tissue distribution of rifampicin after intra-tracheal administration of high (≥25 mg/kg) doses of amorphous and crystalline powder formulations to Sprague Dawley rats. Powder formulations were administered by intra-tracheal insufflation to rats. Lung and liver safety were evaluated by histopathology. Serum alanine transaminase (ALT) and aspartate aminotransferase (AST) assays were performed to study the hepatic effects. Rifampicin was quantified in the tissues using LC-MS/MS. Intra-tracheal administration of rifampicin decreased the drug burden on the liver compared to oral administration based on its lower serum ALT activity. Repeated-dose intra-tracheal rifampicin was well tolerated by rats, confirmed by the absence of drug or delivery induced complexities. The histopathological evaluation of rat lungs, after both single and repeated drug administration for seven days, suggested the absence of drug-induced toxicity. Following single intra-tracheal delivery of 50 mg/kg doses, comparable rifampicin concentrations to that from same oral dose were observed in lung, liver, heart and brain. Inhaled delivery of high-dose rifampicin was safe to rat lungs and liver suggesting its potential for localized as well as systemic drug delivery without toxicity concerns.

Systemic Delivery of hGhrelin Derivative by Lyophilizate for Dry Powder Inhalation System in Monkeys

Ghrelin is the peptide that increases the hunger sensation and food intake and is expected to be clinically applied for treatment of diseases such as cachexia and anorexia nervosa. In the clinical application of ghrelin, injections are problematic in that they are invasive and inconvenient. Thus, we aimed to develop a formulation that can eliminate the need for injections and can be applied clinically. We prepared formulations of an hGhrelin derivative, in which the octanoyl group essential for expression of activity is modified to avoid rapid des-acylation, using lyophilizate for a dry powder inhalation (LDPI) system. The formulation of hGhrelin derivative was optimized by the addition of phenylalanine, of which the fine particle fraction of 5 µm or less was 41.7 ± 3.8%. We also performed pharmacokinetic/pharmacodynamic tests in monkeys using the optimum formulation that can be applied clinically. The absolute bioavailability of inhaled hGhrelin derivative with respect to that intravenously injected was 16.9 ± 2.6%. An increase in growth hormone was shown as an effect of the inhaled hGhrelin derivative similar to intravenous injection. The LDPI formulation can deliver the hGhrelin derivative systemically, and it is expected to be applied clinically as a substitute for injections.

Correlation and clinical relevance of animal models for inhaled pharmaceuticals and biopharmaceuticals

Nonclinical studies are fundamental for the development of inhaled drugs, as for any drug product, and for successful translation to clinical practice. They include in silico, in vitro, ex vivo and in vivo studies and are intended to provide a comprehensive understanding of the inhaled drug beneficial and detrimental effects. To date, animal models cannot be circumvented during drug development programs, acting as surrogates of humans to predict inhaled drug response, fate and toxicity. Herein, we review the animal models used during the different development stages of inhaled pharmaceuticals and biopharmaceuticals, highlighting their strengths and limitations.

Construction of a Live-Attenuated Vaccine Strain of Yersinia pestis EV76-B-SHUΔpla and Evaluation of Its Protection Efficacy in a Mouse Model by Aerosolized Intratracheal Inoculation

Plague, which is caused by Yersinia pestis, is one of the most dangerous infectious diseases. No FDA-approved vaccine against plague is available for human use at present. To improve the immune safety of Y. pestis EV76 based live attenuated vaccine and to explore the feasibility of aerosolized intratracheal inoculation (i.t.) route for vaccine delivery, a plasminogen activator protease (pla) gene deletion mutant of the attenuated Y. pestis strain EV76-B-SHU was constructed, and its residual virulence and protective efficacy were evaluated in a mouse model via aerosolized intratracheal inoculation (i.t.) or via subcutaneous injection (s.c.). The residual virulence of EV76-B-SHUΔpla was significantly reduced compared to that of the parental strain EV76-B-SHU following i.t. and s.c. infection. The EV76-B-SHUΔpla induced higher levels of mucosal antibody sIgA in the bronchoalveolar lavage fluid of mice immunized by i.t. but not by s.c.. Moreover, after lethal challenge with Y. pestis biovar Microtus strain 201 (avirulent in humans), the protective efficacy and bacterial clearance ability of the EV76-B-SHUΔpla-i.t. group were comparable to those of the EV76-B-SHUΔpla-s.c. and EV76-B-SHU immunized groups. Thus, the EV76-B-SHUΔpla represents an excellent live-attenuated vaccine candidate against pneumonic plague and aerosolized i.t. represents a promising immunization route in mouse model.

CHF6001 Inhibits NF-κB Activation and Neutrophilic Recruitment in LPS-Induced Lung Inflammation in Mice

Inhibitors of phosphodiesterase 4 (PDE4) are potent anti-inflammatory agents, inhibiting the production of inflammatory mediators through the elevation of intracellular cAMP concentrations. We studied the activity of a novel PDE4 inhibitor, CHF6001, both in vitro in human cells and in vivo, using bioluminescence imaging (BLI) in mice lung inflammation. Mice transiently transfected with the luciferase gene under the control of an NF-κB responsive element (NF-κB-luc) have been used to assess the in vivo anti-inflammatory activity of CHF6001 in lipopolysaccharide (LPS)-induced lung inflammation. BLI as well as inflammatory cells and the concentrations of pro-inflammatory cytokines were monitored in bronchoalveolar lavage fluids (BALF) while testing in vitro its ability to affect the production of leukotriene B₄ (LTB₄), measured by LC/MS/MS, by LPS/LPS/N-formyl--methionyl--leucyl-phenylalanine (fMLP)-activated human blood. CHF6001 inhibited the production of LTB₄ in LPS/fMLP-activated human blood at sub-nanomolar concentrations. LPS-induced an increase of BLI signal in NF-κB-luc mice, and CHF6001 administered by dry powder inhalation decreased in parallel luciferase signal, cell airway infiltration, and pro-inflammatory cytokine concentrations in BALF. The results obtained provide in vitro and in vivo evidence of the anti-inflammatory activity of the potent PDE4 inhibitor CHF6001, showing that with a topical administration that closely mimics inhalation in humans, it efficiently disrupts the NF-κB activation associated with LPS challenge, an effect that may be relevant for the prevention of exacerbation episodes in chronic obstructive pulmonary disease subjects.

Intra-tracheal amikacin spray delivery in healthy mechanically ventilated piglets

BACKGROUND

Nebulization during mechanical ventilation is impeded by large extra-pulmonary drug deposition and long administration durations which currently limit implementation of inhaled antibiotic therapy. Direct intra-tracheal delivery using a sprayer represents an appealing alternative investigated in small animal models, but large animal data are lacking.

METHODS

Amikacin was administered through intravenous infusion (20 mg/kg), nebulization (60 mg/kg) and direct intra-tracheal spray (30 mg/kg) to 10 intubated piglets, in a randomized cross-over design. Amikacin concentrations were measured in the serum and pulmonary parenchyma. Anatomic deposition was investigated using immuno-histochemistry.

RESULTS

Spray delivery resulted in higher amikacin outputs than nebulization and infusion. Pulmonary inhaled delivery techniques yielded much higher lung concentrations and much lower serum concentrations than intravenous infusion. However, unlike nebulization and infusion, intra-tracheal spray delivery was associated with more than 100- and 1000-fold variability in lung concentrations between and within animals. Amikacin specific immuno-histochemistry showed consistent bronchial and alveolar drug deposition with all modalities.

CONCLUSION

Nebulization remains the most reliable and simple technique to deliver inhaled amikacin uniformly to the lung during mechanical ventilation. Further development of tracheal sprays is required to take advantage of potential benefits related to high drug output and low extra-pulmonary deposition in large animals.

Inhaled formulation and device selection: bridging the gap between preclinical species and first-in-human studies

The factors that influence inhaled first-in-human (FIH) device and formulation selection often differ significantly from the factors that have influenced the preceding preclinical experiments and inhalation toxicology work. In order to minimize the risk of delivery issues negatively impacting a respiratory pipeline program, the preclinical and FIH delivery systems must be considered holistically. This topic will be covered in more detail in this paper. Several examples will be presented that highlight how appropriate scientific strategy can help bridge the gap between delivering to preclinical species and human. Considerations for the FIH device selection (metered dose inhaler, dry powder inhaler and nebulizer) and formulation optimization for small molecules will be discussed in context with the preclinical delivery systems.

Development of spray-freeze-dried siRNA/PEI powder for inhalation with high aerosol performance and strong pulmonary gene silencing activity

In the present study, a novel dry small interfering RNA (siRNA) powder for inhalation, containing polyethyleneimine (PEI) as a delivery vector, was produced by spray freeze drying (SFD). The powder had spherical and highly porous structure of approximately 10 μm in diameter with high aerosol performance for emission and lung delivery. The reconstituted siRNA/PEI complex after dissolution of the powder had almost the same physicochemical properties and in vitro gene silencing activity as the original one constituted in the sample solution before SFD, showing that the integrity of the siRNA was maintained. In in vivo studies of intratracheal administration into lung metastasis mice and healthy mice, powder with a low dose of 3 μg siRNA exhibited strong and specific gene silencing activity against tumors metastasized to the lungs, whereas it caused no significant histological changes, lactate dehydrogenase leakage, or inflammatory cytokine induction in the lungs. These results strongly indicated that inhalable dry siRNA/PEI powders can provide effective pulmonary gene silencing without severe lung injury and that SFD can be applied to the production of such powders.

Insights on animal models to investigate inhalation therapy: Relevance for biotherapeutics

Acute and chronic respiratory diseases account for major causes of illness and deaths worldwide. Recent developments of biotherapeutics opened a new era in the treatment and management of patients with respiratory diseases. When considering the delivery of therapeutics, the inhaled route offers great promises with a direct, non-invasive access to the diseased organ and has already proven efficient for several molecules. To assist in the future development of inhaled biotherapeutics, experimental models are crucial to assess lung deposition, pharmacokinetics, pharmacodynamics and safety. This review describes the animal models used in pulmonary research for aerosol drug delivery, highlighting their advantages and limitations for inhaled biologics. Overall, non-clinical species must be selected with relevant scientific arguments while taking into account their complexities and interspecies differences, to help in the development of inhaled medicines and ensure their successful transposition in the clinics.

Combination therapy for tuberculosis treatment: pulmonary administration of ethionamide and booster co-loaded nanoparticles

Tuberculosis (TB) is a leading infectious cause of death worldwide. The use of ethionamide (ETH), a main second line anti-TB drug, is hampered by its severe side effects. Recently discovered "booster" molecules strongly increase the ETH efficacy, opening new perspectives to improve the current clinical outcome of drug-resistant TB. To investigate the simultaneous delivery of ETH and its booster BDM41906 in the lungs, we co-encapsulated these compounds in biodegradable polymeric nanoparticles (NPs), overcoming the bottlenecks inherent to the strong tendency of ETH to crystallize and the limited water solubility of this Booster. The efficacy of the designed formulations was evaluated in TB infected macrophages using an automated confocal high-content screening platform, showing that the drugs maintained their activity after incorporation in NPs. Among tested formulations, "green" β-cyclodextrin (pCD) based NPs displayed the best physico-chemical characteristics and were selected for in vivo studies. The NPs suspension, administered directly into mouse lungs using a Microsprayer®, was proved to be well-tolerated and led to a 3-log decrease of the pulmonary mycobacterial load after 6 administrations as compared to untreated mice. This study paves the way for a future use of pCD NPs for the pulmonary delivery of the [ETH:Booster] pair in TB chemotherapy.

Inhaled efficacious dose translation from rodent to human: A retrospective analysis of clinical standards for respiratory diseases

Clinical pharmacologists and toxicologists are often faced with predicting equivalent dosages for humans from biological observations in laboratory animals. Allometric scaling has been used extensively as the basis for extrapolation of drug dosage that might be expected to produce the equivalent biological effects. Allometry is the study of size and its consequences and it is based on the anatomical, physiological, and biochemical similarities between animals. In this review, retrospective analyses have been performed based on data reported in the literature in an attempt to determine the utility of allometric scaling for human dose projections from pre-clinical data for compounds that are delivered by inhalation. The limited pre-clinical efficacy data available on inhaled drugs that are also used clinically supports the current method of scaling using a fixed allometric exponent of 0.67. An example of the utility of the human inhaled dose projections for planning inhaled toxicology studies is also presented.

Dry Powder and Nebulized Aerosol Inhalation of Pharmaceuticals Delivered to Mice Using a Nose-only Exposure System

Obstructive respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD) are currently treated by inhaled anti-inflammatory and bronchodilator drugs. Despite the availability of multiple treatments, both diseases are growing public health concerns. The majority of asthma patients are well controlled on current inhaled therapies but a substantial number of patients with severe asthma are not. Asthma affects an estimated 300 million people worldwide and approximately 20 percent have a severe form of the disease. In contrast to asthma, there are few effective therapies for COPD. An estimated 10% of the population has COPD and the trend in death rates is increasing for COPD while decreasing for other major diseases. Although developing drugs for inhaled delivery is challenging, the nose-only inhalation unit enables direct delivery of novel drugs to the lung of rodents for pre-clinical efficacy and safety/toxicology studies. Inhaled drug delivery has multiple advantages for respiratory diseases, where high concentration in the lung improves efficacy and minimizes systemic side effects. Inhaled corticosteroids and bronchodilators benefit from these advantages and inhaled delivery may also hold potential for future biologic therapies. The inhalation unit described herein can generate, sample for characterization, and uniformly deposit a drug aerosol in the lungs of rodents. This enables the pre-clinical determination of the efficacy and safety of drug doses deposited in the lungs of rodents, key data required before initiating clinical development.

Disposable Dosators for Pulmonary Insufflation of Therapeutic Agents to Small Animals

Development of new therapeutic products requires efficacy testing in an animal model. The pulmonary route of administration can be utilized to deliver drugs locally and systemically. Evaluation of dry powder aerosols necessitates an efficient dispersion mechanism to maintain high concentrations in an exposure chamber or for direct endotracheal administration. While solutions exist to expose animals by passive inhalation to dry powder aerosols, most require masses of powder in large excess of the dose delivered. This precludes conducting early feasibility studies as insufficient drug is available at the research or early development stage to support the dose delivery requirements for conventional aerosol delivery systems. When designing an aerosol drug product, aerodynamic performance can relate directly to delivery efficiency and efficacy. Dispersion of powder into an aerosol requires energy input sufficient to overcome interparticulate forces, and particle engineering approaches can substantially improve aerosol performance. We have developed a dispersion system (dosator) which can aerosolize engineered dry powder aerosols efficiently for the purpose of direct pulmonary insufflation, dispersion into an exposure system or generation for analytical purposes.

Protective effect of magnolol-loaded polyketal microparticles on lipopolysaccharide-induced acute lung injury in rats

Magnolol has shown inhibitory effects on NO production and TNF-alpha production in lipopolysaccharide (LPS)-activated macrophages and LPS-induced acute lung injury; however, the poor solubility of magnolol has hindered its clinical success. In this study, magnolol-loaded microparticles were prepared via single emulsion method from a polyketal polymer, termed PK3. The particle sizes of magnolol-loaded PK3 microparticle is 3.73 ± 0.41 μm, and was suitable for phagocytosis by macrophages and pulmonary drug delivery. PK3 microparticles exhibited excellent biocompatibility both in vitro and in vivo. More importantly, intratracheal delivery of these magnolol-loaded microparticles significantly reduced the lung inflammatory responses at low dosage of magnolol (0.5 mg/kg), and have great clinical potential in treating acute lung injury.

Btk Inhibitor RN983 Delivered by Dry Powder Nose-only Aerosol Inhalation Inhibits Bronchoconstriction and Pulmonary Inflammation in the Ovalbumin Allergic Mouse Model of Asthma

BACKGROUND

In allergen-induced asthma, activated mast cells start the lung inflammatory process with degranulation, cytokine synthesis, and mediator release. Bruton's tyrosine kinase (Btk) activity is required for the mast cell activation during IgE-mediated secretion.

METHODS

This study characterized a novel inhaled Btk inhibitor RN983 in vitro and in ovalbumin allergic mouse models of the early (EAR) and late (LAR) asthmatic response.

RESULTS

RN983 potently, selectively, and reversibly inhibited the Btk enzyme. RN983 displayed functional activities in human cell-based assays in multiple cell types, inhibiting IgG production in B-cells with an IC50 of 2.5 ± 0.7 nM and PGD2 production from mast cells with an IC50 of 8.3 ± 1.1 nM. RN983 displayed similar functional activities in the allergic mouse model of asthma when delivered as a dry powder aerosol by nose-only inhalation. RN983 was less potent at inhibiting bronchoconstriction (IC50(RN983) = 59 μg/kg) than the β-agonist salbutamol (IC50(salbutamol) = 15 μg/kg) in the mouse model of the EAR. RN983 was more potent at inhibiting the antigen induced increase in pulmonary inflammation (IC50(RN983) = <3 μg/kg) than the inhaled corticosteroid budesonide (IC50(budesonide) = 27 μg/kg) in the mouse model of the LAR.

CONCLUSIONS

Inhalation of aerosolized RN983 may be effective as a stand-alone asthma therapy or used in combination with inhaled steroids and β-agonists in severe asthmatics due to its potent inhibition of mast cell activation.

Inhalation Study of Mycobacteriophage D29 Aerosol for Mice by Endotracheal Route and Nose-Only Exposure

BACKGROUND

Lytic mycobacteriophage D29 has the potential for tuberculosis treatment including multidrug-resistant strains. The aims of this study are to investigate deposition and distribution of aerosolized phage D29 particles in naive Balb/C mice, together with pharmacokinetics and evaluation of acute lung injury.

METHODS

Pharmacokinetics and BALF (bronchoalveolar lavage fluids) were analyzed after administration of phage D29 aerosols by endotracheal route using Penn-century aerosolizer; Collison 6-jet and Spinning top aerosol nebulizers (STAG) were used to generate phage aerosols with different particle size distributions in nose-only inhalation experiments. After exposure, deposited amounts of phage D29 particles in respiratory tracts were measured, and deposition efficiencies were calculated. A typical path deposition model for mice was developed, and then comparisons were made between predictions and experimentally measured results.

RESULTS

Approximately 10% of aerosolized phages D29 reached lung of mouse for pulmonary delivery, and were completely eliminated until 72 h after administration. In contrast, about 0.1% of intraperitoneal injected phages reached the lung, and were almost eliminated at 12 h time point. The inflammation was hardly observed in lung according to the results of BALF analysis. The CMADs (count median aerodynamic diameters) of generated aerosol by Collison and STAG nebulizer were 0.8 μm and 1.5 μm, respectively. After nose-only exposure, measured deposition efficiencies in whole respiratory tract for 0.8 and 1.5 μm phage particles were below 1% and 10%, respectively. Predictions of the computer deposition model compared fairly well with experimentally measured results.

CONCLUSIONS

This is the first systematic study of phage D29 aerosol respiratory challenge in laboratory animals. It provides evidence that aerosol delivery of phage D29 is an effective way for treating pulmonary infections caused by Mycobacterium tuberculosis. This research will also provide important data for future inhalation experiments.