Dry powder inhalation: past, present and future

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.

The pharmacokinetics of antibiotics in cystic fibrosis

INTRODUCTION

Dosing of antibiotics in people with cystic fibrosis (CF) is challenging, due to altered pharmacokinetics, difficulty of lung tissue penetration, and increasing presence of antimicrobial resistance.

AREAS COVERED

The purpose of this work is to critically review original data as well as previous reviews and guidelines on pharmacokinetics of systemic and inhaled antibiotics in CF, with the aim to propose strategies for optimization of antibacterial therapy in both children and adults with CF.

EXPERT OPINION

For systemic antibiotics, absorption is comparable in CF patients and non-CF controls. The volume of distribution (Vd) of most antibiotics is similar between people with CF with normal body composition and healthy individuals. However, there are a few exceptions, like cefotiam and tobramycin. Many antibiotic class-dependent changes in drug metabolism and excretion are reported, with an increased total body clearance for ß-lactam antibiotics, aminoglycosides, fluoroquinolones, and trimethoprim. We, therefore, recommend following class-specific guidelines for CF, mostly resulting in higher dosages per kg bodyweight in CF compared to non-CF controls. Higher local antibiotic concentrations in the airways can be obtained by inhalation therapy, with which eradication of bacteria may be achieved while minimizing systemic exposure and risk of toxicity.

Development of High Dose Oseltamivir Phosphate Dry Powder for Inhalation Therapy in Viral Pneumonia

Oseltamivir phosphate (OP) is an antiviral drug available only as oral therapy for the treatment of influenza and as a potential treatment option when in combination with other medication in the fight against the corona virus disease (COVID-19) pneumonia. In this study, OP was formulated as a dry powder for inhalation, which allows drug targeting to the site of action and potentially reduces the dose, aiming a more efficient therapy. Binary formulations were based on micronized excipient particles acting like diluents, which were blended with the drug OP. Different excipient types, excipient ratios, and excipient size distributions were prepared and examined. To investigate the feasibility of delivering high doses of OP in a single dose, 1:1, 1:3, and 3:1 drug/diluent blending ratios have been prepared. Subsequently, the aerosolization performance was evaluated for all prepared formulations by cascade impaction using a novel medium-resistance capsule-based inhaler (UNI-Haler). Formulations with micronized trehalose showed relatively excellent aerosolization performance with highest fine-particle doses in comparison to examined lactose, mannitol, and glucose under similar conditions. Focusing on the trehalose-based dry-powder inhalers' (DPIs) formulations, a physicochemical characterization of extra micronized grade trehalose in relation to the achieved performance in dispersing OP was performed. Additionally, an early indication of inhaled OP safety on lung cells was noted by the viability MTT assay utilizing Calu-3 cells.

Anatomical variability in the upper tracheobronchial tree: sex-based differences and implications for personalized inhalation therapies

The morphometry of the large conducting airways is presumed to have a strong effect on the regional deposition of inhaled aerosol particles. Nevertheless, sex-based differences have not been fully quantified and are still largely ignored in designing inhalation therapies. To this end, we retrospectively analyzed high-resolution computed tomography scans for 185 individuals (90 women, 95 men) in the age range of 12-89 yr to determine airway luminal areas, airway lengths, and bifurcation angles. Only subjects free of chronic airway disease were considered. In men, luminal areas of the upper conducting airways were, on average, ∼30%-50% larger when compared with those in women, with the largest differences found in the trachea (289.72 ± 54.25 vs. 193.50 ± 42.37 mm² for men and women, respectively). The ratio of the largest luminal area in men to the smallest luminal area in women (in any given segment) ranged between 4.5 and 8.6, the largest differences being found in the lobar bronchi. Sex-based differences were minor in the case of bifurcation angles (e.g., average main bifurcation angle: 93.04 ± 9.58° vs. 91.03 ± 9.81° for men and women, respectively), but large intersubject variability was found irrespective of sex (e.g., range of main bifurcation angle: 65.04°-122.01° vs. 69.46°-113.94° for men and women, respectively). Bronchial segments were shorter by ∼5%-20% in women relative to men, the largest differences being located in the upper lobes. False discovery rate analysis revealed statistically significant associations among morphometric measures of the right lung in women (but not in men), suggesting two phenotypes among women that we attribute to the smaller female thoracic volume.NEW & NOTEWORTHY We found significant sex-based morphometric differences in the central airways of healthy men and women that were only mildly attenuated in subsets matched for lung volume. Lumen areas were significantly larger in men (∼30%-50%). Large variability (∼75%-87%) in airway bifurcation angles (60°-122°) was found irrespective of sex. The branching pattern of the right main and right upper bronchi in women (but not in men) follows two phenotypes modulated by lung volume.

Pulmonary Delivery of Biological Drugs

In the last decade, biological drugs have rapidly proliferated and have now become an important therapeutic modality. This is because of their high potency, high specificity and desirable safety profile. The majority of biological drugs are peptide- and protein-based therapeutics with poor oral bioavailability. They are normally administered by parenteral injection (with a very few exceptions). Pulmonary delivery is an attractive non-invasive alternative route of administration for local and systemic delivery of biologics with immense potential to treat various diseases, including diabetes, cystic fibrosis, respiratory viral infection and asthma, etc. The massive surface area and extensive vascularisation in the lungs enable rapid absorption and fast onset of action. Despite the benefits of pulmonary delivery, development of inhalable biological drug is a challenging task. There are various anatomical, physiological and immunological barriers that affect the therapeutic efficacy of inhaled formulations. This review assesses the characteristics of biological drugs and the barriers to pulmonary drug delivery. The main challenges in the formulation and inhalation devices are discussed, together with the possible strategies that can be applied to address these challenges. Current clinical developments in inhaled biological drugs for both local and systemic applications are also discussed to provide an insight for further research.

Advancement of a Positive-Pressure Dry Powder Inhaler for Children: Use of a Vertical Aerosolization Chamber and Three-Dimensional Rod Array Interface

PURPOSE

Available dry powder inhalers (DPIs) have very poor lung delivery efficiencies in children. The objective of this study was to advance and experimentally test a positive-pressure air-jet DPI for children based on the use of a vertical aerosolization chamber and new patient interfaces that contain a three-dimensional (3D) rod array structure.

METHODS

Aerosolization performance of different air-jet DPI designs was first evaluated based on a 10 mg powder fill mass of a spray-dried excipient enhanced growth (EEG) formulation. Devices were actuated with positive pressure using flow rate (10-20 L/min) and inhaled volume (750 ml) conditions consistent with a 5-year-old child. Devices with best performance were connected to different mouthpiece designs to determine the effect on aerosolization and tested for aerosol penetration through a realistic pediatric in vitro mouth-throat model.

RESULTS

Use of the new vertical aerosolization chamber resulted in high quality aerosol formation. Inclusion of a 3D rod array structure in the mouthpiece further reduced aerosol size by approximately 20% compared to conditions without a rod array, and effectively dissipated the turbulent jet leaving the device. Best case device and mouthpiece combinations produced < 2% mouth-throat depositional loss and > 70% lung delivery efficiency based on loaded dose.

CONCLUSIONS

In conclusion, use of a 3D rod array in the MP of a positive-pressure air-jet DPI was found to reduce aerosol size by 20%, not significantly increase MP depositional loss, reduce mouth-throat deposition by 6.4-fold and enable lung delivery efficiency as high as 73.4% of loaded dose based on pediatric test conditions.

Numerical Study on Particle Adhesion in Dry Powder Inhaler Device

This study investigated the particle adhesion mechanism in a capsule of dry powder inhaler (DPI) based on a combined computational fluid dynamics and discrete element method (CFD-DEM) approach. In this study, the Johnson-Kendall-Roberts (JKR) theory was selected as the adhesion force model. The simulation results corroborated the experimental results-numerous particles remained on the outlet side of the capsule, while a few particles remained on the inlet side. In the computer simulation, the modeled particles were placed in a capsule. They were quickly dispersed to both sides of the capsule, by air fed from one side of the capsule, and delivered from the air inlet side to the outlet side of the capsule. It was confirmed that vortex flows were seen at the outlet side of the capsule, which, however, were not seen at the inlet side. Numerous collisions were observed at the outlet side, while very few collisions were observed at the inlet side. These results suggested that the vortex flows were crucial to reduce the amount of residual particles in the capsule. The original capsule was then modified to enhance the vortex flow in the area, where many particles were found remaining. The modified capsule reduced the number of residual particles compared to the original capsule. This investigation suggests that the CFD-DEM approach can be a great tool for understanding the particle adhesion mechanism and improving the delivery efficiency of DPIs.

Spray Drying for the Preparation of Nanoparticle-Based Drug Formulations as Dry Powders for Inhalation

Nanoparticle-based therapeutics have been used in pulmonary formulations to enhance delivery of poorly water-soluble drugs, protect drugs against degradation and achieve modified release and drug targeting. This review focuses on the use of spray drying as a solidification technique to produce microparticles containing nanoparticles (i.e., nanoparticle (NP) agglomerates) with suitable properties as dry powders for inhalation. The review covers the general aspects of pulmonary drug delivery with emphasis on nanoparticle-based dry powders for inhalation and the principles of spray drying as a method for the conversion of nanosuspensions to microparticles. The production and therapeutic applications of the following types of NP agglomerates are presented: nanoporous microparticles, nanocrystalline agglomerates, lipid-based and polymeric formulations. The use of alternative spray-drying techniques, namely nano spray drying, and supercritical CO2-assisted spray drying is also discussed as a way to produce inhalable NP agglomerates.

Performance tuning of particle engineered mannitol in dry powder inhalation formulations

Typically, smooth lactose particles are used as carrier in dry powder formulations for inhalation. Two classical approaches to improve their aerodynamic behaviour are the addition of fines (milled lactose) or magnesium stearate (MgSt). Mannitol (Parteck® M DPI) as an alternative carrier was used in this study. It has an irregular particle size distribution and a large and rough surface. This could be challenging for the detachment of micronised drug upon inhalation and it is unclear whether classic strategies for the optimisation of aerodynamic performance can be applied. In contrast, its rough surface could be an advantage in terms of drug load. To address these questions, the mannitol carrier was blended with two different drugs using various concentrations up to 50%. Self-produced mannitol fines and MgSt in different amounts and in combination were added. Blends were investigated regarding their in vitro aerodynamic performance, dosing behaviour and powder rheology. An addition of up to 30% drug load was possible while retaining good flowability and constant dosing behaviour. Despite the rough and indented carrier surface of the mannitol carrier, the addition of fines or MgSt increased the inhalable fraction, but higher concentrations of fines, as used for lactose blends, were necessary.

Relationship Between Geometric and Aerodynamic Particle Size Distributions in the Formulation of Solution and Suspension Metered-Dose Inhalers

The relationship between the geometric particle size distribution (GPSD) and the aerodynamic particle size distribution (APSD) of commercial solution and suspension metered-dose inhaler (MDI) formulations was assessed to clarify the use of GPSD to estimate the APSD. The size distribution of particles discharged from four suspension and four solution MDIs was measured using the Inas®100 light-scattering spectrometer and a Next Generation Impactor. The conversion factor was calculated by measuring the GPSD and APSD of MDIs. The morphology and physical properties of MDIs were studied using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Six of the eight MDIs showed similar conversion factor profiles, irrespective of their composition and formulation types. Applying the conversion factor obtained from one of the six MDIs resulted in a particle size distribution comparable to each APSD except for some formulations. The two other solution MDIs, which contained citric acid, had much higher and variable conversion factors. SEM images and DSC scans of the solids obtained by nebulization of the solutions containing beclomethasone and/or citric acid showed the formation of a paste-like amorphous solid. These results indicated that APSD of solution and suspension MDIs that form rigid particles may be estimated by using the conversion factor and GPSD. Contrarily, the estimation is more difficult in formulations that tend to lose the particle structure during the measurement.

Polymer-coated aperture plates for tailored atomization processes

There is a significant industrial demand for minimizing the size of droplets for various technical applications. Herein, conformal polymer coatings were used to decrease the orifice dimensions of aperture plates to almost any desired dimension. The generated droplet size revealed a relevant impact on the final dried particle size in a spray-drying process. Likewise, the smaller droplets generated resulted in an improved lung deposition following inhalation. Overall, the current results help increase the understanding on how to manipulate the size distribution of droplets produced by actuated aperture plates, especially in the sub-10 μm range.

Excipient-free pulmonary insulin dry powder: Pharmacokinetic and pharmacodynamics profiles in rats

A novel pure insulin spray-dried powder for DPI product (Ins_SD) was studied with respect to physico-chemical stability, in vitro respirability, bioavailability, activity and tolerability. Ins_SD powder exhibited a very high in vitro respirability, independently of the DPI product preparation (manual or semi-automatic). Physico-chemical characteristics of Ins_SD powder remained within the pharmacopoeia limits during 6 months of storage at room temperature. PK/PD profiles were measured in rats that received the pulmonary powders by intratracheal insufflation and compared with Afrezza inhalation insulin. Due to the low drug powder mass to deliver, both insulin powders were diluted with mannitol. Insulin from Ins_SD was promptly absorbed (t_max 15 min and C_maxx4.9 ± 1.5 mU/ml). Afrezza had a slower absorption (t_max 30 min and C_max of 1.8 ± 0.37 mU/ml). After glucose injection, Ins_SD determined a rapid reduction of glucose level, similar to Afrezza. As reference, insulin subcutaneous injection showed a long-lasting hypoglycemic effect due to the slow absorption that prolonged insulin plasma level. In summary, Ins_SD product is suitable for post-prandial glucose control, providing a convenient and compliant product, in particular in the event of using a disposable device. Albeit the product has to be stored in fridge, its stability at room temperature allows the diabetic individual to carry the daily dose in normal conditions.

3D characterisation of dry powder inhaler formulations: Developing X-ray micro computed tomography approaches

Carrier-based dry powder inhaler (DPI) formulations need to be accurately characterised for their particle size distributions, surface roughnesses, fines contents and flow properties. Understanding the micro-structure of the powder formulation is crucial, yet current characterisation methods give incomplete information. Commonly used techniques like laser diffraction (LD) and optical microscopy (OM) are limited due to the assumption of sphericity and can give variable results depending on particle orientation and dispersion. The aim of this work was to develop new three dimensional (3D) powder analytical techniques using X-ray computed tomography (XCT) that could be employed for non-destructive metrology of inhaled formulations. α-lactose monohydrate powders with different characteristics have been analysed, and their size and shape (sphericity/aspect ratio) distributions compared with results from LD and OM. The three techniques were shown to produce comparable size distributions, while the different shape distributions from XCT and OM highlight the difference between 2D and 3D imaging. The effect of micro-structure on flowability was also analysed through 3D measurements of void volume and tap density. This study has demonstrated for the first time that XCT provides an invaluable, non-destructive and analytical approach to obtain number- and volume-based particle size distributions of DPI formulations in 3D space, and for unique 3D characterisation of powder micro-structure.

Recent advances in aerosol devices for the delivery of inhaled medications

Introduction: Aerosolized medications are commonly prescribed for the treatment of patients with pulmonary diseases, and there has been an increased interest in the development of aerosol delivery devices over the years. Technical innovations have advanced device design, novel features such as breath actuation, dose tracking, portability, and feedback mechanism during treatment that improved the performance of aerosol devices, and effectiveness of inhalation therapy.Areas covered: The purpose of this paper is to review recent advances in aerosol devices for delivery of inhaled medications.Expert opinion: Drug formulations and device designs are rapidly evolving to make more consistent dosing across a broad range of inspiratory efforts, to maximize dose and target specific areas of the diseased lung.

Influence of Composition and Spray-Drying Process Parameters on Carrier-Free DPI Properties and Behaviors in the Lung: A review

Although dry powder inhalers (DPIs) have attracted great interest compared to nebulizers and metered-dose inhalers (MDIs), drug deposition in the deep lung is still insufficient to enhance therapeutic activity. Indeed, it is estimated that only 10–15% of the drug reaches the deep lung while 20% of the drug is lost in the oropharyngeal sphere and 65% is not released from the carrier. The potentiality of the powders to disperse in the air during the patient’s inhalation, the aerosolization, should be optimized. To do so, new strategies, in addition to classical lactose-carrier, have emerged. The lung deposition of carrier-free particles, mainly produced by spray drying, is higher due to non-interparticulate forces between the carrier and drug, as well as better powder uniformity and aerosolization. Moreover, the association of two or three active ingredients within the same powder seems easier. This review is focused on a new type of carrier-free particles which are characterized by a sugar-based core encompassed by a corrugated shell layer produced by spray drying. All excipients used to produce such particles are dissected and their physico-chemical properties (Péclet number, glass transition temperature) are put in relation with the lung deposition ability of powders. The importance of spray-drying parameters on powders’ properties and behaviors is also evaluated. Special attention is given to the relation between the morphology (characterized by a corrugated surface) and lung deposition performance. The understanding of the closed relation between particle material composition and spray-drying process parameters, impacting the final powder properties, could help in the development of promising DPI systems suitable for local or systemic drug delivery.

Emerging trends in inhaled drug delivery

Ideally, inhaled therapy is driven by the needs of specific disease management. Lung biology interfaces with inhaler performance to allow optimal delivery of therapeutic agent for disease treatment. Inhalation aerosol products consist of the therapeutic agent, formulation, and device. The manufacturing specifications on each of the components, and their combination, allow accurate and reproducible control of measures of quality and in-vitro performance. These product variables in combination with patient variables, including co-ordination skill during inhaler use, intrinsic lung biology, disease and consequent pulmonary function, contribute to drug safety and efficacy outcomes. Due to the complexity of pulmonary drug delivery, predicting biological outcomes from first principles has been challenging. Ongoing research appears to offer new insights that may allow accurate prediction of drug behavior in the lungs. Disruptive innovations were characteristic of research and development in inhaled drug delivery at the end of the last century. Although there were relatively few new inhaled products launched in the first decade of the new millennium it was evident that the earlier years of exploration resulted in maturation of commercially successful technologies. A significant increase in new and generic products has occurred in the last decade and technical, regulatory and disease management trends are emerging. Some of these developments can trace their origins to earlier periods of creativity in the field while others are a reflection of advances in other areas of basic and computer, sciences and engineering. Select biological and technical advances are highlighted with reflections on the potential to impact future clinical and regulatory considerations.

In vitro toxicity screening of polyglycerol esters of fatty acids as excipients for pulmonary formulations

One of the main problems for the development of pulmonary formulations is the low availability of approved excipients. Polyglycerol esters of fatty acids (PGFA) are promising molecules for acting as excipient for formulation development and drug delivery to the lung. However, their biocompatibility in the deep lung has not been studied so far. Main exposed cells include alveolar epithelial cells and alveolar macrophages. Due to the poor water-solubility of PGFAs, the exposure of alveolar macrophages is expected to be much higher than that of epithelial cells. In this study, two PGFAs and their mixture were tested regarding cytotoxicity to epithelial cells and cytotoxicity and functional impairment of macrophages. Cytotoxicity was assessed by dehydrogenase activity and lactate dehydrogenase release. Lysosome function, phospholipid accumulation, phagocytosis, nitric oxide production, and cytokine release were used to evaluate macrophage function. Cytotoxicity was increased with the increased polarity of PGFA molecules. At concentrations above 1 mg/ml accumulation in lysosomes, impairment of phagocytosis, secretion of nitric oxide, and increased release of cytokines were noted. The investigated PGFAs in concentrations up to 1 mg/ml can be considered as uncritical and are promising for advanced pulmonary delivery of high powder doses and drug targeting to alveolar macrophages.

Inhaled levodopa in Parkinson's disease patients with OFF periods: A randomized 12-month pulmonary safety study

INTRODUCTION

CVT-301 is an orally inhaled levodopa therapy approved for the intermittent treatment of OFF episodes in Parkinson's disease patients who are taking a standard oral levodopa regimen. This open-label, randomized, controlled study over 12 months characterizes the safety, including pulmonary safety, of CVT-301 84 mg (nominal respirable levodopa fine-particle dose, 50 mg).

METHODS

Patients experiencing motor fluctuations were randomized 2:1 to CVT-301 or an observational cohort (OC) receiving oral standard of care. Pulmonary safety was assessed using spirometry and carbon monoxide diffusion capacity (DL_CO). Exploratory efficacy endpoints, assessed only for CVT-301, included change in Unified Parkinson's Disease Rating Scale Part III (UPDRS-III), patients achieving ON within 60 min and remaining ON at 60 min, Patient Global Impression of Change (PGIC) scale, and total daily OFF time.

RESULTS

Of 408 patients randomized, 310 completed the study (204 in CVT-301 and 106 in OC). Mean 12-month changes from baseline for CVT-301 were -0.105 L (FEV₁) and -0.378 mL/min/mm Hg (DL_CO), and for OC were -0.117 L and -0.722 mL/min/mm Hg, respectively. Between-group comparisons were not statistically significant. For FEV₁/FVC the 12-month change was -0.3 and -1.6, respectively, which was a significant between-group difference. However, between-group differences were not significant at 3 and 9 months and all changes from baseline were small (<2.0%). UPDRS-III scores improved from predose to 60 min postdose at all assessments; 80%-85% of patients switched ON within 60 min and remained ON; and >75% reported improvement in PGIC. OFF time decreased by 1.32-1.42 h/day.

CONCLUSION

CVT-301 84 mg induced no clinically significant differences in pulmonary function compared with the OC. Improvements in motor scores, OFF time, and patient-reported outcomes support clinical efficacy for up to 12 months.

The Confusing World of Dry Powder Inhalers: It Is All About Inspiratory Pressures, Not Inspiratory Flow Rates

Dry powder inhalers (DPIs) all have the ability to aerosolize dry powders, but they each offer different operating mechanisms and resistances to inhaled airflow. This variety has resulted in both clinician and patient confusion concerning DPI performance, use, and effectiveness. Particularly, there is a growing misconception that a single peak inspiratory flow rate (PIFR) can determine a patient's ability to use a DPI effectively, regardless of its design or airflow resistance. For this review article, we have sifted through the relevant literature concerning DPIs, inspiratory pressures, and inspiratory flow rates to provide a comprehensive and concise discussion and recommendations for DPI use. We ultimately clarify that the controlling parameter for DPI performance is not the PIFR but the negative pressure generated by the patient's inspiratory effort. A pressure drop ∼≥1 kPa (∼10 cm H₂O) with any DPI is a reasonable threshold above which a patient should receive an adequate lung dose. Overall, we explore the underlying factors controlling inspiratory pressures, flow rates and dispensing, and dispersion characteristics of the various DPIs to clarify that inspiratory pressures, not flow rates, limit and control a patient's ability to generate sufficient flow for effective DPI use.

The Impact of Lipid Corona on Rifampicin Intramacrophagic Transport Using Inhaled Solid Lipid Nanoparticles Surface-Decorated with a Mannosylated Surfactant

The mimicking of physiological conditions is crucial for the success of accurate in vitro studies. For inhaled nanoparticles, which are designed for being deposited on alveolar epithelium and taken up by macrophages, it is relevant to investigate the interactions with pulmonary surfactant lining alveoli. As a matter of fact, the formation of a lipid corona layer around the nanoparticles could modulate the cell internalization and the fate of the transported drugs. Based on this concept, the present research focused on the interactions between pulmonary surfactant and Solid Lipid Nanoparticle assemblies (SLNas), loaded with rifampicin, an anti-tuberculosis drug. SLNas were functionalized with a synthesized mannosylated surfactant, both alone and in a blend with sodium taurocholate, to achieve an active targeting to mannose receptors present on alveolar macrophages (AM). Physico-chemical properties of the mannosylated SLNas satisfied the requirements relative to suitable respirability, drug payload, and AM active targeting. Our studies have shown that a lipid corona is formed around SLNas in the presence of Curosurf, a commercial substitute of the natural pulmonary surfactant. The lipid corona promoted an additional resistance to the drug diffusion for SLNas functionalized with the mannosylated surfactant and this improved drug retention within SLNas before AM phagocytosis takes place. Moreover, lipid corona formation did not modify the role of nanoparticle mannosylation towards the specific receptors on MH-S cell membrane.

Toxicological assessment of nanoparticle interactions with the pulmonary system

Nanoparticle(NP)-based materials have breakthrough applications in many fields of life, such as in engineering, communications and textiles industries; food and bioenvironmental applications; medicines and cosmetics, etc. Biomedical applications of NPs are very active areas of research with successful translation to pharmaceutical and clinical uses overcoming both pharmaceutical and clinical challenges. Although the attractiveness and enhanced applications of these NPs stem from their exceptional properties at the nanoscale size, i.e. 1-1000 nm, they exhibit completely different physicochemical profiles and, subsequently, toxicological profiles from their parent bulk materials. Hence, the clinical evaluation and toxicological assessment of NPs interactions within biological systems are continuously evolving to ensure their safety at the nanoscale. The pulmonary system is one of the primary routes of exposure to airborne NPs either intentionally, via aerosolized nanomedicines targeting pulmonary pathologies such as cancer or asthma, or unintentionally, via natural NPs and anthropogenic (man-made) NPs. This review presents the state-of-the-art, contemporary challenges, and knowledge gaps in the toxicological assessment of NPs interactions with the pulmonary system. It highlights the main mechanisms of NP toxicity, factors influencing their toxicity, the different toxicological assessment methods and their drawbacks, and the recent NP regulatory guidelines based on literature collected from the research pool of NPs interactions with lung cell lines, in vivo inhalation studies, and clinical trials.

Development of an Inline Dry Powder Inhaler for Oral or Trans-Nasal Aerosol Administration to Children

Background: Dry powder inhalers (DPIs) offer a number of advantages, such as rapid delivery of high-dose inhaled medications; however, DPI use in children is often avoided due to low lung delivery efficiency and difficulty in operating the device. The objective of this study was to develop a high-efficiency inline DPI for administering aerosol therapy to children with the option of using either an oral or trans-nasal approach. Methods: An inline DPI was developed that consisted of hollow inlet and outlet capillaries, a powder chamber, and a nasal or oral interface. A ventilation bag or compressed air was used to actuate the device and simultaneously provide a full deep inspiration consistent with a 5-year-old child. The powder chamber was partially filled with a model spray-dried excipient enhanced growth powder formulation with a mass of 10 mg. Device aerosolization was characterized with cascade impaction, and aerosol transmissions through oral and nasal in vitro models were assessed. Results: Best device performance was achieved when all actuation air passed through the powder chamber (no bypass flow) resulting in an aerosol mean mass median aerodynamic diameter (MMAD) <1.75 μm and a fine particle fraction (<5 μm) ≥90% based on emitted dose. Actuation with the ventilation bag enabled lung delivery efficiency through the nasal and oral interfaces to a tracheal filter of 60% or greater, based on loaded dose. In both oral and nose-to-lung (N2L) administrations, extrathoracic depositional losses were <10%. Conclusion: In conclusion, this study has proposed and initially developed an efficient inline DPI for delivering spray-dried formulations to children using positive pressure operation. Actuation of the device with positive pressure enabled effective N2L aerosol administration with a DPI, which may be beneficial for subjects who are too young to use a mouthpiece or to simultaneously treat the nasal and lung airways of older children.

Inhalable combination powder formulations of phage and ciprofloxacin for P. aeruginosa respiratory infections

Recently we showed that nebulized ciprofloxacin and phage PEV20 in combination had a synergistic bactericidal effect against antibiotic-resistant Pseudomonas aeruginosa isolates from patients with cystic fibrosis. Compared to nebulization, dry powders for inhalation may improve patient handling characteristics and compliance. In the present study, we co-spray dried ciprofloxacin and phage PEV20 using L-leucine with or without lactose as excipients. Two formulations were identified for testing in this study. The mass ratios were set at 1:1:1 for ciprofloxacin, lactose and L-leucine (Formulation A) or 2:1 for ciprofloxacin and L-leucine without lactose (Formulation B). Concentrations of PEV20 were set at 10⁸ and 10⁹ PFU/mL for two clinical P. aeruginosa strains FADD1-PA001 and JIP865, respectively. Formulations A and B were characterized as partially crystalline and the powders recrystallized at >40% relative humidity (RH). Both formulations exhibited strong synergistic antimicrobial killing effect on the two strains. Formulations A and B maintained bactericidal synergy after dispersion using both low and high resistance Osmohaler™. Powder aerosol performance was examined by next generation impactor (NGI) in low resistance inhaler at 100 L/min and by multi-stage liquid impinger (MSLI) in high resistance inhaler at 60 L/min. Fine particle fractions (FPF) obtained by NGI were 59.7 ± 2.1% and 64.3 ± 2.9% for A and B, respectively. FPF obtained by MSLI were 71.0 ± 3.4% and 73.3 ± 5.0%, respectively. In conclusion, it is feasible to prepare stable and inhalable combination powder formulations of phage PEV20 and ciprofloxacin for potential treatment of respiratory infections caused by multi-drug resistant (MDR) P. aeruginosa.

Development and Characterization of a Dry Powder Formulation for Anti-Tuberculosis Drug Spectinamide 1599

PURPOSE

Human tuberculosis (TB) is a global health problem that causes nearly 2 million deaths per year. Anti-TB therapy exists, but it needs to be administered as a cocktail of antibiotics for six months. This lengthy therapy results in low patient compliance and is the main reason attributable to the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis.

METHODS

One alternative approach is to combine anti-TB multidrug therapy with inhalational TB therapy. The aim of this work was to develop and characterize dry powder formulations of spectinamide 1599 and ensure in vitro and in vivo delivered dose reproducibility using custom dosators.

RESULTS

Amorphous dry powders of spectinamide 1599 were successfully spray dried with mass median aerodynamic diameter (MMAD) = 2.32 ± 0.05 μm. The addition of L-leucine resulted in minor changes to the MMAD (1.69 ± 0.35 μm) but significantly improved the inhalable portion of spectinamide 1599 while maintaining amorphous qualities. Additionally, we were able to demonstrate reproducibility of dry powder administration in vitro and in vivo in mice.

CONCLUSIONS

The corresponding systemic drug exposure data indicates dose-dependent exposure in vivo in mice after dry powder intrapulmonary aerosol delivery in the dose range 15.4 - 32.8 mg/kg.

Understanding the motion of hard-shell capsules in dry powder inhalers

The delivery of small drug particles from a dry powder inhaler (DPI) into the patient's peripheral airways requires the dispersion of the powder. In DPIs that contain a rotating pierced capsule, the capsule's motion is paramount to powder dispersion. Previous studies have simplified the capsule motion in an Aerolizer® inhaler as a constant rotation around a fixed center. The present work examines deviations from this simplified motion and describes the capsule collisions with the surrounding inhaler walls. High-speed photography was employed to analyze the motion of a size 3 capsule in an Aerolizer® inhaler at various flow rates ranging from 30 to 100 L/min. Frequent collisions of the capsule with the surrounding inhaler walls were observed. Computational fluid dynamics (CFD) simulations indicated that the air flow through the capsule governs the behavior of small drug particles, while inertial forces are the dominant influence on large carrier particles in the capsule. Discrete element method (DEM) simulations were employed to study the effect of the capsule-inhaler collisions on the powder discharge from a rotating capsule. The collisions vastly improved the discharge of a polydisperse model carrier powder from the capsule over a wide range of cohesiveness.

Delivery of Dry Powders to the Lungs: Influence of Particle Attributes from a Biological and Technological Point of View

Dry powder inhalers are medical devices used to deliver powder formulations of active pharmaceutical ingredients via oral inhalation to the lungs. Drug particles, from a biological perspective, should reach the targeted site, dissolve and permeate through the epithelial cell layer in order to deliver a therapeutic effect. However, drug particle attributes that lead to a biological activity are not always consistent with the technical requirements necessary for formulation design. For example, small cohesive drug particles may interact with neighbouring particles, resulting in large aggregates or even agglomerates that show poor flowability, solubility and permeability. To circumvent these hurdles, most dry powder inhalers currently on the market are carrier-based formulations. These formulations comprise drug particles, which are blended with larger carrier particles that need to detach again from the carrier during inhalation. Apart from blending process parameters, inhaler type used and patient's inspiratory force, drug detachment strongly depends on the drug and carrier particle characteristics such as size, shape, solid-state and morphology as well as their interdependency. This review discusses critical particle characteristics. We consider size of the drug (1-5 µm in order to reach the lung), solid-state (crystalline to guarantee stability versus amorphous to improve dissolution), shape (spherical drug particles to avoid macrophage clearance) and surface morphology of the carrier (regular shaped smooth or nano-rough carrier surfaces for improved drug detachment.) that need to be considered in dry powder inhaler development taking into account the lung as biological barrier.

Selective drug deposition in lungs through pulmonary drug delivery system for effective management of drug-resistant TB

INTRODUCTION

The emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) is a major health issue and continues to be a global health concern. Despite significant advancements in treatment modalities, ~1.6 million deaths worldwide occur due to TB infection. This is because of tuberculosis reservoirs in the alveoli making it a challenge for the formulation scientist to target this.

AREAS COVERED

This review recent investigations on the forefront of pulmonary drug delivery for managing MDR-TB and XDR-TB. Novel delivery systems like liposomes, niosomes, employing carbohydrate, and -coated molecules via conjugation to selectively deliver the drugs to the lung TB reservoir via pulmonary administration are discussed.

EXPERT OPINION

Poor patient adherence to treatment due to side effects and extended therapeutic regimen leads to drug-resistant TB. Thus, it is essential to design novel strategies this issue by developing new chemical entities and/or new delivery systems for delivery to the lungs, consequently reducing the side effects, the frequency and the duration of treatment. Delivery of drugs to enhance the efficacy of new/existing anti-TB drugs to overcome the resistance and enhance patient compliance is underway.

Exploring the influence of particle shape and air velocity on the flowability in the respiratory tract: a computational fluid dynamics approach

Dry powder inhalers (DPIs) are considered a main drug delivery system through pulmonary route. The main objective of this work is to study the flow of differently shaped microparticles in order to find the optimum shape of drug particles that will demonstrate the best flow to the deep lung. The flowability of particles in air or any fluid depends particularly on the drag force which is defined as the resistance of the fluid molecules to the particle flow. One of the most important parameters that affect the drag force is the particles' shape. Computational simulations using COMSOL Multi Physics 5.2 software were performed for investigating the particles flow in the air pathways of lung, and the drag force was calculated for different particles shapes. This was accomplished by screening a set of 17 possible shapes that are expected to be synthesized easily in the micro-scale. In addition, the macro-scale behavior of the investigated shapes was also simulated so as to compare the behavior of the flowing particles in both cases. A very big difference was found between the behavior of particles' flow in the micro and macro scales, but a similar behavior can be obtained if the flow velocity of the microparticles is very high. It was also found that the micro-triangle with aspect ratio 2:1 has the least drag force in both deep and upper lung; so, it should be the shape of choice during the process of particle synthesis for pulmonary drug delivery.

Feasibility Study of Mesoporous Silica Particles for Pulmonary Drug Delivery: Therapeutic Treatment with Dexamethasone in a Mouse Model of Airway Inflammation

Diseases in the respiratory tract rank among the leading causes of death in the world, and thus novel and optimized treatments are needed. The lungs offer a large surface for drug absorption, and the inhalation of aerosolized drugs are a well-established therapeutic modality for local treatment of lung conditions. Nanoparticle-based drug delivery platforms are gaining importance for use through the pulmonary route. By using porous carrier matrices, higher doses of especially poorly soluble drugs can be administered locally, reducing their side effects and improving their biodistribution. In this study, the feasibility of mesoporous silica particles (MSPs) as carriers for anti-inflammatory drugs in the treatment of airway inflammation was investigated. Two different sizes of particles on the micron and nanoscale (1 µm and 200 nm) were produced, and were loaded with dexamethasone (DEX) to a loading degree of 1:1 DEX:MSP. These particles were further surface-functionalized with a polyethylene glycol–polyethylene imine (PEG–PEI) copolymer for optimal aqueous dispersibility. The drug-loaded particles were administered as an aerosol, through inhalation to two different mice models of neutrophil-induced (by melphalan or lipopolysaccharide) airway inflammation. The mice received treatment with either DEX-loaded MSPs or, as controls, empty MSPs or DEX only; and were evaluated for treatment effects 24 h after exposure. The results show that the MEL-induced airway inflammation could be treated by the DEX-loaded MSPs to the same extent as free DEX. Interestingly, in the case of LPS-induced inflammation, even the empty MSPs significantly down-modulated the inflammatory response. This study highlights the potential of MSPs as drug carriers for the treatment of diseases in the airways.

Linking carrier morphology to the powder mechanics of adhesive mixtures for dry powder inhalers via a blend-state model

The aim of this study was to investigate how the carrier morphology affects the expression of blend states in adhesive mixtures as a function of surface coverage ratio (SCR) and to identify where transitions between the different states occur. Adhesive mixtures of five lactose carriers with varying contents of lactose fines, corresponding to blends with different SCR ranging from 0 to 6, were produced by low-shear mixing. The powder mechanics of the mixtures were characterized by bulk density, compressibility and permeability. The appearance of the carriers and blends was studied by scanning electron microscopy, light microscopy and atomic force microscopy. The size and morphology of the carriers had a crucial impact on the evolution of the blend state, and affected the powder mechanical properties of the mixtures. It was found that smaller carriers with little or no surface irregularities were more sensitive to additions of fines resulting in self-agglomeration of fines at relatively low SCR values. On the contrary, carriers with irregular surface structures and larger sizes were able to reach higher SCR values before self-agglomeration of fines occurred. This could be attributed to an increased deagglomeration efficiency of irregular and larger carriers and to fines predominantly adhering to open pores.

Development of a New Inhaler for High-Efficiency Dispersion of Spray-Dried Powders Using Computational Fluid Dynamics (CFD) Modeling

Computational fluid dynamics (CFD) modeling offers a powerful tool for the development of drug delivery devices using a first principles approach but has been underutilized in the development of pharmaceutical inhalers. The objective of this study was to develop quantitative correlations for predicting the aerosolization behavior of a newly proposed dry powder inhaler (DPI). The dose aerosolization and containment (DAC) unit DPI utilizes inlet and outlet air orifices designed to maximize the dispersion of spray-dried powders, typically with low air volumes (~ 10 mL) and relatively low airflow rates (~ 3 L/min). Five DAC unit geometries with varying orifice outlet sizes, configurations, and protrusion distances were considered. Aerosolization experiments were performed using cascade impaction to determine mean device emitted dose (ED) and mass median aerodynamic diameter (MMAD). Concurrent CFD simulations were conducted to predict both flow field-based and particle-based dispersion parameters that captured different measures of turbulence. Strong quantitative correlations were established between multiple measures of turbulence and the experimentally observed aerosolization metrics of ED and MMAD. As expected, increasing turbulence produced increased ED with best case values reaching 85% of loaded dose. Surprisingly, decreasing turbulence produced an advantageous decrease in MMAD with values as low as approximately 1.6 μm, which is in contrast with previous studies. In conclusion, CFD provided valuable insights into the performance of the DAC unit DPI as a new device including a two-stage aerosolization process offering multiple avenues for future enhancements.

Spray-Dried PulmoSphere™ Formulations for Inhalation Comprising Crystalline Drug Particles

Over the past 20 years, solution-based spray dried powders have transformed inhaled product development, enabling aerosol delivery of a wider variety of molecules as dry powders. These include inhaled proteins for systemic action (e.g., Exubera®) and high-dose inhaled antibiotics (e.g., TOBI® Podhaler™). Although engineered particles provide several key advantages over traditional powder processing technologies (e.g., spheronized particles and lactose blends), the physicochemical stability of the amorphous drug present in these formulations brings along its own unique set of constraints. To this end, a number of approaches have been developed to maintain the crystallinity of drugs throughout the spray drying process. One approach is to spray dry suspensions of micronized drug(s) from a liquid feed. In this method, minimization of drug particle dissolution in the liquid feed is critical, as dissolved drug is converted into amorphous domains in the spray-dried drug product. The review explores multiple formulation and engineering strategies for decreasing drug dissolution independent of the physicochemical properties of the drug(s). Strategies to minimize particle dissolution include spray blending of particles of different compositions, formation of respirable agglomerates of micronized drug with small porous carrier particles, and use of common ions. The formulations extend the range of doses that can be delivered with a portable inhaler from about 100 ng to 100 mg. The spray-dried particles exhibit significant advantages in terms of lung targeting and dose consistency relative to conventional lactose blends, while still maintaining the crystallinity of drug(s) in the formulated drug product.

100 Years of Drug Delivery to the Lungs

Inhalation therapy is one of the oldest approaches to the therapy of diseases of the respiratory tract. It is well recognised today that the most effective and safe means of treating the lungs is to deliver drugs directly to the airways. Surprisingly, the delivery of therapeutic aerosols has a rich history dating back more than 2,000 years to Ayurvedic medicine in India, but in many respects, the introduction of the first pressurised metered-dose inhaler (pMDI) in 1956 marked the beginning of the modern pharmaceutical aerosol industry. The pMDI was the first truly portable and convenient inhaler that effectively delivered drug to the lung and quickly gained widespread acceptance. Since 1956, the pharmaceutical aerosol industry has experienced dramatic growth. The signing of the Montreal Protocol in 1987 to reduce the use of CFCs as propellants for aerosols led to a surge in innovation that resulted in the diversification of inhaler technologies with significantly enhanced delivery efficiency, including modern pMDIs, dry powder inhalers and nebuliser systems. There is also great interest in tailoring particle size to deliver drugs to treat specific areas of the respiratory tract. One challenge that has been present since antiquity still exists, however, and that is ensuring that the patient has access to the medication and understands how to use it effectively. In this article, we will provide a summary of therapeutic aerosol delivery systems from ancient times to the present along with a look to the future.

Is there room for further innovation in inhaled therapy for airways disease?

Inhaled medication is the cornerstone in the treatment of patients across a spectrum of respiratory diseases including asthma and chronic obstructive pulmonary disease. The benefits of inhaled therapy have long been recognised but the most important innovations have occurred over the past 60 years, beginning with the invention of the pressurised metered dose inhaler. However, despite over 230 different device and drug combinations currently being available, disease control is far from perfect. Here we look at how innovation in inhaler design may improve treatments for respiratory diseases and how new formulations may lead to treatments for diseases beyond the lungs. We look at the three main areas where innovation in inhaled therapy is most likely to occur: 1) device engineering and design; 2) chemistry and formulations; and 3) digital technology associated with inhalers. Inhaler design has improved significantly but considerable challenges still remain in order to continually innovate and improve targeted drug delivery to the lungs. Healthcare professionals want see innovations that motivate their patients to achieve their goal of improving their health, through better adherence to treatment. Patients want devices that are easy to use and to see that their efforts are rewarded by improvements in their condition.

KEY POINTS

The dictionary definition of innovation is the introduction of new things, ideas or ways of doing something. We show how this definition can be applied to inhaled therapy.We take a look at the past to see what drove innovation in inhaler design and how this has led to the current devices.We look at the current drivers of innovation in engineering, chemistry and digital technology and predict how this may translate to new devices.Can innovation help the healthcare professional manage their patients better?What does the patient expect from innovation in their device?

EDUCATIONAL AIMS

To understand the importance of inhaled medication in the treatment of lung diseases.To understand how innovation has helped advance some of the devices patients use today from basic and inefficient designs.To understand the obstacles that prevent patients from receiving optimal treatment from their inhalers.To understand how innovation in inhaler design can lead to improved treatment for patients and widen the range of diseases that can be treated via the inhaled route.

Formulation of High-Performance Dry Powder Aerosols for Pulmonary Protein Delivery

PURPOSE

Pulmonary delivery of biologics is of great interest, as it can be used for the local treatment of respiratory diseases or as a route to systemic drug delivery. To reach the full potential of inhaled biologics, a formulation platform capable of producing high performance aerosols without altering protein native structure is required.

METHODS

A formulation strategy using Particle Replication in Non-wetting Templates (PRINT) was developed to produce protein dry powders with precisely engineered particle morphology. Stability of the incorporated proteins was characterized and the aerosol properties of the protein dry powders was evaluated in vitro with an Andersen Cascade Impactor (ACI).

RESULTS

Model proteins bovine serum albumin (BSA) and lysozyme were micromolded into 1 μm cylinders composed of more than 80% protein, by mass. Extensive characterization of the incorporated proteins found no evidence of alteration of native structures. The BSA formulation produced a mass median aerodynamic diameter (MMAD) of 1.77 μm ± 0.06 and a geometric standard deviation (GSD) of 1.51 ± 0.06 while the lysozyme formulation had an MMAD of 1.83 μm ± 0.12 and a GSD of 1.44 ± 0.03.

CONCLUSION

Protein dry powders manufactured with PRINT could enable high-performance delivery of protein therapeutics to the lungs.

Fluticasone Propionate/Salmeterol MDPI (AirDuo RespiClick®): A Review in Asthma

The novel, easy-to-use, breath-actuated fluticasone propionate/salmeterol multidose dry powder inhaler (MDPI) (AirDuo RespiClick^®) was recently approved in the USA for twice-daily treatment of asthma in patients aged ≥ 12 years. This inhaled corticosteroid (ICS) and long-acting β₂-adrenoreceptor agonist (LABA) combination treatment is available in low-, mid- and high-dosage formulations (55/14, 113/14 and 232/14 μg, respectively). In 12-week, phase III trials in patients aged ≥ 12 years with persistent asthma, all three dosages of fluticasone propionate/salmeterol MDPI treatment produced significant improvements in lung function and other asthma symptoms compared with fluticasone propionate MDPI monotherapy or placebo MDPI. In a 26-week, phase III trial in this patient population, mid- and high-dosage fluticasone propionate/salmeterol MDPI were noninferior to mid- (250/50 μg) and high- (500/50 μg) dosage fluticasone propionate/salmeterol DPI (Advair Diskus^®), respectively, in terms of improvements in lung function. Treatment-emergent adverse events (TEAEs) with fluticasone propionate/salmeterol MDPI were mostly of mild to moderate severity, with no severe TEAEs deemed to be treatment related. Although long-term pharmacovigilance is required to fully establish its safety, given the ease of use and favorable characteristics of the device and its clinical efficacy at relatively low metered doses of the active moieties, fluticasone propionate/salmeterol MDPI is an important emerging treatment option in patients aged ≥ 12 years with asthma.