Delivery technology of inhaled therapy for asthma and COPD.

Inhaled therapy is the cornerstone of the management of asthma and chronic obstructive pulmonary disease (COPD). Drugs such as bronchodilators and corticosteroids are administered directly to the airways for local effect and rapid onset of action while systemic exposure and side effects are minimized. There are four major types of inhaler devices used clinically to generate aerosols for inhalation, namely, pressurized metered-dose inhalers (pMDIs), nebulizers, Soft Mist™ inhalers (SMIs) and dry powder inhalers (DPIs). Each of them has its own unique characteristics that can target different patient groups. For instance, patients' inhaler technique is critical for pMDIs and SMIs to achieve proper drug deposition in the lung, which could be challenging for some patients. Nebulizers are designed to deliver aerosols to patients during tidal breathing, but they require electricity to operate and are less portable than other devices. DPIs are the only device that delivers aerosols in dry powder form with better stability, but they rely on patients' inspiration effort for powder dispersion, rendering them unsuitable for patients with compromised lung function. Choosing a device that can cater for the need of individual patient is paramount for effective inhaled therapy. This chapter provides an overview of inhaled therapy for the management of asthma and COPD. The operation principles, merits and limitations of different delivery technologies are examined. Looking ahead, the challenges of delivering novel therapeutics such as biologics through the pulmonary route are also discussed.

Co-Delivery of D-LAK Antimicrobial Peptide and Capreomycin as Inhaled Powder Formulation to Combat Drug-Resistant Tuberculosis.

INTRODUCTION: The emergence of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) posed a severe challenge to tuberculosis (TB) management. The treatment of MDR-TB involves second-line anti-TB agents, most of which are injectable and highly toxic. Previous metabolomics study of the Mtb membrane revealed that two antimicrobial peptides, D-LAK120-A and D-LAK120-HP13, can potentiate the efficacy of capreomycin against mycobacteria. AIMS: As both capreomycin and peptides are not orally available, this study aimed to formulate combined formulations of capreomycin and D-LAK peptides as inhalable dry powder by spray drying. METHODS AND RESULTS: A total of 16 formulations were prepared with different levels of drug content and capreomycin to peptide ratios. A good production yield of over 60% (w/w) was achieved in most formulations. The co-spray dried particles exhibited spherical shape with a smooth surface and contained low residual moisture of below 2%. Both capreomycin and D-LAK peptides were enriched at the surface of the particles. The aerosol performance of the formulations was evaluated with Next Generation Impactor (NGI) coupled with Breezhaler®. While no significant difference was observed in terms of emitted fraction (EF) and fine particle fraction (FPF) among the different formulations, lowering the flow rate from 90 L/min to 60 L/min could reduce the impaction at the throat and improve the FPF to over 50%. CONCLUSIONS: Overall, this study showed the feasibility of producing co-spray dried formulation of capreomycin and antimicrobial peptides for pulmonary delivery. Future study on their antibacterial effect is warranted.

Inhalable neutralizing antibodies - promising approach to combating respiratory viral infections.

Monoclonal antibodies represent an exciting class of therapeutics against respiratory viral infections. Notwithstanding their specificity and affinity, the conventional parenteral administration is suboptimal in delivering antibodies for neutralizing activity in the airways due to the poor distribution of macromolecules to the respiratory tract. Inhaled therapy is a promising approach to overcome this hurdle in a noninvasive manner, while advances in antibody engineering have led to the development of unique antibody formats which exhibit properties desirable for inhalation. In this Opinion, we examine the major challenges surrounding the development of inhaled antibodies, identify knowledge gaps that need to be addressed and provide strategies from a drug delivery perspective to enhance the efficacy and safety of neutralizing antibodies against respiratory viral infections.

A dual action of D-amino acids on anti-biofilm activity and moisture-protection of inhalable ciprofloxacin powders.

Although inhalation powder aerosols of antibiotics have been used to treat respiratory infections caused by Pseudomonas aeruginosa, biofilms are difficult to clear. Ciprofloxacin and D-amino acids (D-Met, D-Trp and D-Phe) were shown to facilitate P. aeruginosa biofilm removal. Spray dried powders for inhalation tend to be amorphous, hence unstable to moisture which causes deterioration in the aerosol performance. Hydrophobic L-amino acids such as leucine can impart moisture protection. In this study, we hypothesized that co-spray dried formulations of ciprofloxacin and hydrophobic D-amino acids will offer the combined benefits of both anti-biofilm and moisture protection properties. Of the three D-amino acids tested, D-Met and D-Trp (at 5 mM) but not D-Phe reduced clinical isolate P. aeruginosa biofilm loads and the extent of biofilm clearance was further enhanced in the presence of ciprofloxacin. Subsequently, ciprofloxacin was spray dried alone or in combination with 30% (w/w) D-Met or D-Trp. The biological and physicochemical properties of the powders were assessed, including the minimum inhibitory concentration, anti-biofilm activity, particle size distribution and morphology, solid-state properties, water sorption, and aerosol performance. The spray dried combination powders were physically stable and inhalable with fine particle fraction (<5 µm) values of 50-57% when aerosolized. The powders exhibited enhanced anti-biofilm activity compared with ciprofloxacin alone. The presence of D-amino acids provided moisture protection, with the recrystallization event shifting from 50% RH to 80% RH in powders containing D-Trp. In conclusion, the use of D-amino acids (D-Met or D-Trp) is an attractive formulation strategy which offers dual benefits of anti-biofilm effect and moisture protection.

The effects of different doses of inhaled bacteriophage therapy for Pseudomonas aeruginosa pulmonary infections in mice.

OBJECTIVES: Inhaled phage therapy has been revisited as a potential treatment option for respiratory infections caused by multidrug-resistant Pseudomonas aeruginosa; however, there is a distinct gap in understanding the dose-response effect. The aim of this study was to investigate the dose-response effect of Pseudomonas-targeting phage PEV31 delivered by the pulmonary route in a mouse lung infection model. METHODS: Neutropenic BALB/c mice were infected with multidrug-resistant P. aeruginosa (2 × 104 colony-forming units) through the intratracheal route and then treated with PEV31 at three different doses of 7.5 × 104 (Group A), 5 × 106 (Group B), and 5 × 108 (Group C) plaque-forming units, or phosphate-buffered saline at 2 hours postinoculation. Mice (n = 5-7) were euthanized at 2 hours and 24 hours postinfection, and lungs, kidneys, spleen, liver, bronchoalveolar lavage fluid, and blood were collected for bacteria and phage enumeration. RESULTS: At 24 hours postinfection, all phage-treated groups exhibited a significant reduction in pulmonary bacterial load by 1.3-1.9 log10, independent of the delivered phage dose. The extent of phage replication was negatively correlated with the dose administered, with log10 titre increases of 6.2, 2.7, and 9 for Groups A, B, and C, respectively. Phage-resistant bacterial subpopulations in the lung homogenate samples harvested at 24 hours postinfection increased with the treatment dose (i.e. 30%, 74%, and 91% in respective Groups A-C). However, the mutants showed increased susceptibility to ciprofloxacin, impaired twitching motility, and reduced blue-green pigment production. The expression of the inflammatory cytokines (IL-1ß and IL-6, and TNF-α) was suppressed with increasing PEV31 treatment dose. DISCUSSION: This study provides the dose-response effect of inhaled phage therapy that may guide dose selection for treating P. aeruginosa respiratory infections in humans.

Spray-Dried Powder Formulation of Capreomycin Designed for Inhaled Tuberculosis Therapy.

Multi-drug-resistant tuberculosis (MDR-TB) is a huge public health problem. The treatment regimen of MDR-TB requires prolonged chemotherapy with multiple drugs including second-line anti-TB agents associated with severe adverse effects. Capreomycin, a polypeptide antibiotic, is the first choice of second-line anti-TB drugs in MDR-TB therapy. It requires repeated intramuscular or intravenous administration five times per week. Pulmonary drug delivery is non-invasive with the advantages of local targeting and reduced risk of systemic toxicity. In this study, inhaled dry powder formulation of capreomycin targeting the lung was developed using spray drying technique. Among the 16 formulations designed, the one containing 25% capreomycin (w/w) and spray-dried at an inlet temperature of 90 °C showed the best overall performance with the mass median aerodynamic diameter (MMAD) of 3.38 µm and a fine particle fraction (FPF) of around 65%. In the pharmacokinetic study in mice, drug concentration in the lungs was approximately 8-fold higher than the minimum inhibitory concentration (MIC) (1.25 to 2.5 µg/mL) for at least 24 h following intratracheal administration (20 mg/kg). Compared to intravenous injection, inhaled capreomycin showed significantly higher area under the curve, slower clearance and longer mean residence time in both the lungs and plasma.

Dry powder pharmaceutical biologics for inhalation therapy.

Therapeutic biologics such as genes, peptides, proteins, virus and cells provide clinical benefits and are becoming increasingly important tools in respiratory medicine. Pulmonary delivery of therapeutic biologics enables the potential for safe and effective treatment option for respiratory diseases due to high bioavailability while minimizing absorption into the systemic circulation, reducing off-target toxicity to other organs. Development of inhalable powder formulation requires stabilization of complex biological materials, and each type of biologics may present unique challenges and require different formulation strategy combined with manufacture process to ensure biological and physical stabilities during production and over shelf-life. This review examines key formulation strategies for stabilizing proteins, nucleic acids, virus (bacteriophages) and bacterial cells in inhalable powders. It also covers characterization methods used to assess physicochemical properties and aerosol performance of the powders, biological activity and structural integrity of the biologics, and chemical analysis at the nanoscale. Furthermore, the review includes manufacture technologies which are based on lyophilization and spray-drying as they have been applied to manufacture Food and Drug Administration (FDA)-approved protein powders. In perspective, formulation and manufacture of inhalable powders for biologic are highly challenging but attainable. The key requirements are the stability of both the biologics and the powder, along with the powder dispersibility. The formulation to be developed depends on the manufacture process as it will subject the biologics to different stresses (temperature, mechanical and chemical) which could lead to degradation by different pathways. Stabilizing excipients coupled with the suitable choice of process can alleviate the stability issues of inhaled powders of biologics.

Modeling of a spray drying method to produce ciprofloxacin nanocrystals inside the liposomes utilizing a response surface methodology: Box-Behnken experimental design.

Spray drying was previously used to modify the physical form of the encapsulated ciprofloxacin drug to produce ciprofloxacin nanocrystals inside the liposomes (CNL). The purpose of the present study was to optimize CNL powder production by evaluating the response surface via design of experiments (DoE). Using the Box-Behnken (BB) design, the study independent variables were the protectant type (sucrose, trehalose or lactose), protectant amount, drying temperature, and spray gas flow. Individual spray drying experiments were performed at various set points for each variable followed by characterization of the produced powders. Liposomal particle size, drug encapsulation efficiency (EE%), liposomal surface zeta potential, and nanocrystal dimensions were the design dependant variables. By applying the least square regression method on the experimental data, mathematical models were developed using the mathematical software package MATLAB R2018b. Model reliability and the significance of the model's factors were estimated using analysis of variance (ANOVA). The generated CNL powders showed spherical to elliptical liposomal vesicles with particle sizes ranging from 98 to 159 nm. The EE (%) ranged from 30 to 95% w/w while the zeta potential varied between -3.5 and -10.5 mV. The encapsulated ciprofloxacin nanocrystals were elongated cylindrical structures with an aspect ratio of 4.0-7.8. Coefficients of determination (R2 > 0.9) revealed a good agreement between the predicted and experimental values for all responses except for the nanocrystal dimensions. Sucrose and lactose were superior to trehalose in protecting the liposomes during spray drying. The amount of sugar significantly affected the characteristics of the CNL powders (p-value < 0.05). In conclusion, the DoE approach using BB design has efficiently modelled the generation of CNL by spray drying. The optimum processing conditions which produced high drug encapsulation (90%) after formation of nanocrystals and a vesicle size of ~125 nm utilized 57% (w/w) sucrose, an 80 °C inlet temperature, and an atomization rate of 742 L/hr.

Inhalation delivery technology for genome-editing of respiratory diseases.

The clustered regulatory interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) system has significant therapeutic potentials for lung congenital diseases such as cystic fibrosis, as well as other pulmonary disorders like lung cancer and obstructive diseases. Local administration of CRISPR/Cas9 therapeutics through inhalation can achieve high drug concentration and minimise systemic exposure. While the field is advancing with better understanding on the biological functions achieved by CRISPR/Cas9 systems, the lack of progress in inhalation formulation and delivery of the molecule may impede their clinical translation efficiently. This forward-looking review discussed the current status of formulations and delivery for inhalation of relevant biologics such as genes (plasmids and mRNAs) and proteins, emphasising on their design strategies and preparation methods. By adapting and optimising formulation strategies used for genes and proteins, we envisage that development of inhalable CRISPR/Cas9 liquid or powder formulations for inhalation administration can potentially be fast-tracked in near future.

Synergistic activity of phage PEV20-ciprofloxacin combination powder formulation-A proof-of-principle study in a P. aeruginosa lung infection model.

Combination treatment using bacteriophage and antibiotics is potentially an advanced approach to combatting antimicrobial-resistant bacterial infections. We have recently developed an inhalable powder by co-spray drying Pseudomonas phage PEV20 with ciprofloxacin. The purpose of this study was to assess the in vivo effect of the powder using a neutropenic mouse model of acute lung infection. The synergistic activity of PEV20 and ciprofloxacin was investigated by infecting mice with P. aeruginosa, then administering freshly spray-dried single PEV20 (106 PFU/mg), single ciprofloxacin (0.33 mg/mg) or combined PEV20-ciprofloxacin treatment using a dry powder insufflator. Lung tissues were then harvested for colony counting and flow cytometry analysis at 24 h post-treatment. PEV20 and ciprofloxacin combination powder significantly reduced the bacterial load of clinical P. aeruginosa strain in mouse lungs by 5.9 log10 (p < 0.005). No obvious reduction in the bacterial load was observed when the animals were treated only with PEV20 or ciprofloxacin. Assessment of immunological responses in the lungs showed reduced inflammation associating with the bactericidal effect of the PEV20-ciprofloxacin powder. In conclusion, this study has demonstrated the synergistic potential of using the combination PEV20-ciprofloxacin powder for P. aeruginosa respiratory infections.

Inhalable Hydroxychloroquine Powders for Potential Treatment of COVID-19.

Background: Hydroxychloroquine (HCQ) is one of the repurposed drugs proposed for the treatment of coronavirus disease 2019 (COVID-19). However, all the published clinical trials involve oral administration of the drug, although the disease is primarily a respiratory one. Direct inhaled delivery could reduce the side effects associated with oral use and ensure a high concentration of the drug in the lungs. In this study, inhalable HCQ powders were prepared and characterized for potential COVID-19 therapy. Methods: Hydroxychloroquine sulfate (HCQ-sul) was jet milled (JM) followed by conditioning by storage at different relative humidities (43%, 53%, 58%, and 75% RHs) for 7 days. The solid-state properties, including particle morphology and size distribution, crystallinity, and vapor moisture profiles of HCQ-sul samples, were characterized by scanning electron microscopy, laser diffraction, X-ray powder diffraction, differential scanning calorimetry, thermogravimetric analysis, and dynamic water vapor sorption. The aerosol performance of the HCQ-sul powders was assessed using a medium-high resistance Osmohaler coupling to a next-generation impactor (NGI) at a flow rate of 60 L/min. Results: The jet-milled powder showed a volume median diameter of 1.7 µm (span 1.5) and retained the same crystalline form as the raw HCQ-sul. A small amount of amorphous materials was present in the jet-milled HCQ-sul, which was convertible to the stable, crystalline state after conditioning at 53%, 58%, and 75% RH. The recovered fine particle fraction (FPF)recovered and the emitted fine particle fraction (FPFemitted) of the HCQ-sul sample immediately after jet milling and the samples after conditioning at 43%, 53%, and 58% RH were similar at ∼43% and 61%, respectively. In contrast, the sample having conditioned at 75%RH showed lower corresponding values at 33% and 26% respectively, due to the formation of solid bridges caused by excessive moisture. Conclusion: Inhalable crystalline powders of HCQ-sul were successfully prepared, which can be used for clinical testing as a potential inhaled COVID-19 treatment.

Transmucosal drug administration as an alternative route in palliative and end-of-life care during the COVID-19 pandemic.

The Coronavirus disease 2019 (COVID-19) pandemic has led to a surge in need for alternative routes of administration of drugs for end of life and palliative care, particularly in community settings. Transmucosal routes include intranasal, buccal, sublingual and rectal. They are non-invasive routes for systemic drug delivery with the possibility of self-administration, or administration by family caregivers. In addition, their ability to offer rapid onset of action with reduced first-pass metabolism make them suitable for use in palliative and end-of-life care to provide fast relief of symptoms. This is particularly important in COVID-19, as patients can deteriorate rapidly. Despite the advantages, these routes of administration face challenges including a relatively small surface area for effective drug absorption, small volume of fluid for drug dissolution and the presence of a mucus barrier, thereby limiting the number of drugs that are suitable to be delivered through the transmucosal route. In this review, the merits, challenges and limitations of each of these transmucosal routes are discussed. The goals are to provide insights into using transmucosal drug delivery to bring about the best possible symptom management for patients at the end of life, and to inspire scientists to develop new delivery systems to provide effective symptom management for this group of patients.

Pharmacokinetics and Time-Kill Study of Inhaled Antipseudomonal Bacteriophage Therapy in Mice.

Inhaled bacteriophage (phage) therapy is a potential alternative to conventional antibiotic therapy to combat multidrug-resistant (MDR) Pseudomonas aeruginosa infections. However, pharmacokinetics (PK) and pharmacodynamics (PD) of phages are fundamentally different from antibiotics and the lack of understanding potentially limits optimal dosing. The aim of this study was to investigate the in vivo PK and PD profiles of antipseudomonal phage PEV31 delivered by pulmonary route in immune-suppressed mice. BALB/c mice were administered phage PEV31 at doses of 107 and 109 PFU by the intratracheal route. Mice (n = 4) were sacrificed at 0, 1, 2, 4, 8, and 24 h posttreatment and various tissues (lungs, kidney, spleen, and liver), bronchoalveolar lavage fluid, and blood were collected for phage quantification. In a separate study combining phage with bacteria, mice (n = 4) were treated with PEV31 (109 PFU) or phosphate-buffered saline (PBS) at 2 h postinoculation with MDR P. aeruginosa Infective PEV31 and bacteria were enumerated from the lungs. In the phage-only study, the PEV31 titer gradually decreased in the lungs over 24 h, with a half-life of approximately 8 h for both doses. In the presence of bacteria, in contrast, the PEV31 titer increased by almost 2-log10 in the lungs at 16 h. Furthermore, bacterial growth was suppressed in the PEV31-treated group, while the PBS-treated group showed exponential growth. Of the 10 colonies tested, four phage-resistant isolates were observed from the lung homogenates sampled at 24 h after phage treatment. These colonies had a different antibiogram to the parent bacteria. This study provides evidence that pulmonary delivery of phage PEV31 in mice can reduce the MDR bacterial burden.

Inhaled RNA Therapy: From Promise to Reality.

RNA-based medicine is receiving growing attention for its diverse roles and potential therapeutic capacity. The largest obstacle in its clinical translation remains identifying a safe and effective delivery system. Studies investigating RNA therapeutics in pulmonary diseases have rapidly expanded and drug administration by inhalation allows the direct delivery of RNA therapeutics to the target site of action while minimizing systemic exposure. In this review, we highlight recent developments in pulmonary RNA delivery systems with the use of nonviral vectors. We also discuss the major knowledge gaps that require thorough investigation and provide insights that will help advance this exciting field towards the bedside.

Intratracheal Administration of Dry Powder Formulation in Mice.

In the development of inhalable dry powder formulations, it is essential to evaluate their biological activities in preclinical animal models. This paper introduces a noninvasive method of intratracheal delivery of dry powder formulation in mice. A dry powder loading device that consists of a 200 µL gel loading pipette tip connected to an 1 mL syringe via a three-way stopcock is presented. A small amount of dry powder (1-2 mg) is loaded into the pipette tip and dispersed by 0.6 mL of air in the syringe. Because pipette tips are disposable and inexpensive, different dry powder formulations can be loaded into different tips in advance. Various formulations can be evaluated in the same animal experiment without device cleaning and dose refilling, thereby saving time and eliminating the risk of cross-contamination from residual powder. The extent of powder dispersion can be inspected by the amount of powder remaining in the pipette tip. A protocol of intubation in mouse with a custom-made light source and a guiding cannula is included. Proper intubation is one of the key factors that influences the intratracheal delivery of dry powder formulation to the deep lung region of the mouse.

Predicting the composition and size distribution of dry particles for aerosols and sprays of suspension: A Monte Carlo approach.

A volume-based Monte Carlo simulation describing the distribution of polydisperse particles aerosolized in polydisperse droplets was developed. The algorithm addressed some major limitations found in previous models, particularly when the assumptions of the Poisson distribution, a parametric distribution frequently employed to describe the distribution process both deterministically and stochastically, may be less justified. A total of 144 simulations were conducted over combinations of four formulation factors, namely, the suspension concentration c, the ratio of the mass median diameter of the droplets to that of the particles R, and the geometric standard deviation of the droplet σd and that of the particle σp. Using the current algorithm, we found good agreements between simulated results and those from previous studies. The composition uniformity of the resultant clusters was improved with increasing c and/or R, and decreasing σp and σd. The exhaustive distribution of all simulated particles also allowed ready adaptation to infer other statistics of interest, such as the aerodynamic diameter of the resultant clusters. This approach is useful for prediction of the particle size distribution and chemical composition of powders produced by aerosolization and spray drying of suspensions.

High siRNA loading powder for inhalation prepared by co-spray drying with human serum albumin.

The development of small interfering RNA (siRNA) formulation for pulmonary delivery is a key to the clinical translation of siRNA therapeutics for the treatment of respiratory diseases. Most inhalable siRNA powder formulations published to date were limited by the siRNA content which was often too low to be clinically relevant. This study aimed to prepare inhalable siRNA powder formulations that contained high siRNA loading of over 6% w/w by spray drying, with human serum albumin (HSA) investigated as a dispersion enhancer to improve the aerosol performance. The effect of siRNA, HSA and solute concentrations in the formulations were evaluated systemically using factorial analyses. All the spray dried siRNA powders exhibited excellent aerosol performance with fine particle fraction (FPF) consistently over 50% in all the formulations. An enrichment of HSA on the particle surface was observed. Surface corrugation was more prominent as HSA composition increased. Importantly, the bioactivity of siRNA was successfully preserved upon spray drying as demonstrated in the in vitro transfection study, and up to 78% of intact siRNA retained in the spray dried powder. Overall, HSA is an effective dispersion enhancer and spray drying is an appropriate technique to produce inhalable dry powder with high siRNA loading for further investigation.

Effective mRNA pulmonary delivery by dry powder formulation of PEGylated synthetic KL4 peptide.

Pulmonary delivery of messenger RNA (mRNA) has considerable potential as therapy or vaccine for a range of lung diseases. Inhaled dry powder formulation of mRNA is particularly attractive as it has superior stability and dry powder inhaler is relatively easy to use. A safe and effective mRNA delivery vector as well as a suitable particle engineering method are required to produce a dry powder formulation that is respirable and mediates robust transfection in the lung. Here, we introduce a novel RNA delivery vector, PEG12KL4, in which the synthetic cationic KL4 peptide is attached to a monodisperse linear PEG of 12-mers. The PEG12KL4 formed nano-sized complexes with mRNA at 10:1 ratio (w/w) and mediated effective transfection on human lung epithelial cells. PEG12KL4/mRNA complexes were successfully formulated into dry powder by spray drying (SD) and spray freeze drying (SFD) techniques. Both SD and SFD powder exhibited satisfactory aerosol properties for inhalation. More importantly, the biological activity of the PEG12KL4 /mRNA complexes were successfully preserved after drying. Using luciferase mRNA, the intratracheal administration of the liquid or powder aerosol of PEG12KL4 /mRNA complexes at a dose of 5µg mRNA resulted in luciferase expression in the deep lung region of mice 24h post-transfection. The transfection efficiency was superior to naked mRNA or lipoplexes (Lipofectamine 2000), in which luciferase expression was weaker and restricted to the tracheal region only. There was no sign of inflammatory response or toxicity of the PEG12KL4 /mRNA complexes after single intratracheal administration. Overall, PEG12KL4 is an excellent mRNA transfection agent for pulmonary delivery. This is also the first study that successfully demonstrates the preparation of inhalable dry powder mRNA formulations with in vivo transfection efficiency, showing the great promise of PEG12KL4 peptide as a mRNA delivery vector candidate for clinical applications.

Porous and highly dispersible voriconazole dry powders produced by spray freeze drying for pulmonary delivery with efficient lung deposition.

Systemic administration of antifungal agents for the treatment of pulmonary aspergillosis is limited by the poor lung deposition and severe adverse effects. In contrast, pulmonary delivery allows a higher amount of drug to be delivered directly to the infection site and therefore a lower dose is required. This study aimed to develop porous and inhalable voriconazole dry powder with good lung deposition by spray freeze drying (SFD), using tert-butyl alcohol (TBA) as a co-solvent. A three-factor two-level full factorial design approach was used to investigate the effect of total solute concentration, drug content and co-solvent composition on the aerosol performance of the SFD powder. In general, the SFD voriconazole powder exhibited porous and spherical structure, and displayed crystalline characteristics. The analysis of factorial design indicated that voriconazole content was the most significant variable that could influence the aerosol performance of the SFD powders. The formulations that contained a high voriconazole content (40% w/w) and high TBA concentration in the feed solution (70% v/v) displayed the highest fine particle fraction of over 40% in the Next Generation Impactor study in which the powder was dispersed with a Breezhaler® at 100 L/min. In addition, the fine particle dose of the SFD powder showed a faster dissolution rate when compared to the unformulated voriconazole. Intratracheal administration of SFD voriconazole powder to mice resulted in a substantially higher drug concentration in the lungs when comparing to the group that received an equivalent dose of liquid voriconazole formulation intravenously, while a clinically relevant plasma drug concentration was maintained for at least two hours. Overall, an inhalable voriconazole dry powder formulation exhibiting good aerosol property and lung deposition was developed with clinical translation potential.

Using two-fluid nozzle for spray freeze drying to produce porous powder formulation of naked siRNA for inhalation.

Spray freeze drying is an attractive technology to produce powder formulation for inhalation. It can be used to generate large porous particles which tend to aerosolize efficiently and do not aggregate readily. It also avoids material to be exposed to elevated temperature. In this study, we reported the use of two-fluid nozzle to produce spray freeze dried powder of small interfering RNA (siRNA). The effect of atomization gas flow rate and liquid feed rate were inspected initially using herring sperm DNA (hsDNA) as nucleic acid model. The atomization gas flow rate was found to have a major impact on the aerosol properties. The higher the atomization gas flow rate, the smaller the particle size, the higher the fine particle fraction (FPF). In contrast, the liquid feed rate had very minor effect. Subsequently, spray freeze dried siRNA powder was produced at various atomization gas flow rates. The particles produced were highly porous as examined with the scanning electron microscopy, and the structural integrity of the siRNA was demonstrated with gel electrophoresis. The gene-silencing effect of the siRNA was also successfully preserved in vitro. The best performing siRNA formulation was prepared at the highest atomization gas flow rate investigated with a moderate FPF of 30%. However, this was significantly lower than that obtained with the corresponding hsDNA counterparts (FPF ∼57%). A direct comparison between the hsDNA and siRNA formulations revealed that the former exhibited a lower density, hence a smaller aerodynamic diameter despite similar geometric size.