Leucine as an excipient in spray dried powder for inhalation

Effect of lubricants type and particle size on the rheological properties and aerosolization behavior of dry powder inhalers

A commonly used strategy to improve aerosolization behavior of carrier-based dry powder inhalers (DPIs) is the addition of magnesium stearate as a lubricant, yet it may also negatively affect properties of DPIs. Thus, the aim of this study was to find lubricants that could be used as alternatives of magnesium stearate and meanwhile verify the applicability of using powder rheological properties to predict the performance of different lubricants in DPIs. Here, using fluticasone propionate as a model drug, LH200 as the carrier, influence of lubricants type and particle size, including magnesium stearate, sodium stearate, Leucine, sodium stearate fumarate, Compritol® 888 ATO, and Compritol® HD5 ATO, on the physicochemical properties, powder rheology and aerosolization behavior of the DPI formulations was characterized. Further, the relationship between powder rheological parameters and in-vitro drug deposition parameter, fine particle fraction (FPF), were explored, and the contribution of powder flowability and adhesion was evaluated using principal component analysis (PCA). The results showed that magnesium stearate, sodium stearate and smaller sized leucine significantly reduced the basic flowability energy, aeration energy and Permeability of the DPI formulations, leading to improved aerosolization behavior. A robust linear correlation was established between rheological parameters and FPF. PCA showed that in lubricants containing formulations, the contribution of flowability (74.69%) was greater than that of adhesion (25.31%). In conclusion, sodium stearate and smaller particle size Leucine can be considered as substitutes of magnesium stearate in DPI formulations.

The activity of a Ga(III) catecholate complex against Aspergillus fumigatus in conditions mimicking cystic fibrosis lung and inhaled formulations for its pulmonary administration

Azole-resistant Aspergillus fumigatus (A. fumigatus) is an emerging worldwide pathogen. Pulmonary aspergillosis primarily affects severely immunocompromised patients and is also a particularly critical condition for cystic fibrosis (CF) patients. A recently designed gallium polypyridyl catecholate complex, GaS1, has previously demonstrated in vitro and in vivo antimicrobial activity against Gram-negative bacteria. In the present work GaS1 activity was assessed against A. fumigatus clinical isolates in a novel air-liquid-interface lung infection model, mimicking the conditions found in the CF airways. Furthermore, in this study both a solution for nebulisation and dry powders for inhalation were developed with a view to optimising GaS1 delivery to the lung. The solution for nebulisation was characterised for its osmolality and pH, while the dry powders were characterised by scanning electron microscopy, powder X-ray diffraction, thermal analysis and laser light scattering particle size analysis. The aerodynamic deposition profiles of all formulations were determined using a next generation impactor. GaS1, tested in a concentration range of 0.016-0.5 mg/mL, inhibited the growth of A. fumigatus lung isolates in a complex host-environment-mimicking medium at the non-toxic concentration of 0.063 mg/mL. A marked dose-dependent antifungal activity of GaS1 was also observed in the presence of differentiated human distal lung epithelial cells (NCI-H441) at the air liquid interface, with nearly no fungal growth detected at the macroscopic and microscopic level. A solution for nebulisation and three different dry powder inhaler formulations, prepared by spray-drying GaS1 with different concentrations of L-leucine, displayed suitable aerodynamic characteristics for GaS1 delivery to the lungs, while maintaining excellent antifungal activity. Overall, the results obtained highlight the potential of gallium-polypyridyl catecholate complexes for the management of difficult-to-treat A. fumigatus pulmonary infections.

Pirfenidone microcrystals for pulmonary delivery: Regulation of the precipitation behavior in the supercooled droplet

Pirfenidone (PFD) is one of the first-line drugs for treating idiopathic pulmonary fibrosis, while directly delivering PFD to lung showed better efficiency. However, PFD is a non-glass former and easily precipitates into larger-sized crystals that are undesirable for pulmonary delivery. Hence, the fabrication of PFD particles with pulmonary delivery efficiency remains challenging. Herein, a series of particles were prepared by spray freeze drying a PFD and leucine mixed solution. The sub-ambient behavior of the mixed solution was evaluated via a differential scanning calorimeter. The effects of the PFD/leucine mass ratio and freezing temperature on the particle morphology, size, crystal polymorphism, molecular structure and in vitro aerosol performance were investigated. Shortening the lifetime of the droplet and adding proper amounts of leucine are the keys to decreasing the PFD crystal size and improving its dispersity. The optimal sample is SF-80D-P95L5-2, with high FPF and eFPF values of ∼ 65.97 % and ∼ 27.86 %, and owing to its high drug loading (95 %), the FPD and eFPD are extremely high at ∼ 6.27 mg and ∼ 2.65 mg, respectively, equivalent to ∼ 6.27 mg and ∼ 2.65 mg PFD deposited in the lungs and alveoli, respectively, when 10 mg dry powder is inhaled. This work provides a potential strategy for tuning the precipitation behavior of PFD microcrystals with high pulmonary drug delivery efficiency.

Development of inhaled moxifloxacin-metformin formulation as an alternative for pulmonary tuberculosis treatment

Resistant M. tuberculosis strains threaten pulmonary tuberculosis (P-TB) control since they limit drug options. Drug repositioning and new development strategies are urgently required to overcome resistance. Studies have already shown the beneficial role of the oral antidiabetic metformin as an anti-tuberculosis adjuvant drug. This work aimed to develop an inhalatory dry powder co-formulation of metformin and moxifloxacin to figure out a future option for P-TB treatment. Pre-formulation evaluations indicated the physicochemical compatibility of constituents, demonstrating powder crystallinity and acceptable drug content. Eight moxifloxacin-metformin dry powder formulations were produced by spray drying, and solid-state characterizations showed partial amorphization, ascribed to moxifloxacin. Four formulations containing L-leucine exhibited micromeritic and in vitro deposition profiles indicating pulmonary delivery suitability, like spherical and corrugated particle surface, geometric diameters < 5 μm, high emitted doses (>85 %), and mass median aerodynamic diameters between 1-5 μm. The use of a second spray dryer model further optimized the aerodynamic properties and yield of the best formulation, demonstrating the influence of the equipment used on the product obtained. Moreover, the final formulation showed high in vitro cell tolerability and characteristics in permeability studies indicative of good drug retention in the lungs.

Influence of L-leucine content on the aerosolization stability of spray-dried protein dry powder inhalation (DPI)

Inhalable formulations of medicines intended to act locally in the lung are therapeutically effective at lower doses with targeted delivery, compared to parenteral or oral administration. Meanwhile, different APIs, including biologics, have proven to be challenging regarding formulation and final bioavailability. This study focuses on the production, improved stability performance, and delivery of spray-dried, inhalable protein powders to the lungs. By spray-drying 11 aqueous formulations of proteinX with varying L-leucine content and by employing a Design of Experiment (DoE), two formulations have been selected for stability studies based on the highest fine particle fraction (FPF), highest monomer content, and lowest particle size. We found that 5 %w/w L-leucine (based on protein content) resulted in similar or higher FPF at 2-8 °C and 25 °C/60 %RH (67.12 % and 48.50 %) stored for six months than 10 %w/w L-leucine (68.49 % and 35.04 %). This indicates that less leucine may be sufficient to produce stable, spray-dried inhalable particles with an improved FPF, and by doubling the leucine content, the aerosolization stability can deteriorate. We have discussed the postulated hypothesis underlying the observed stability behavior based on solid-state and morphological analysis. Our results suggest that spray-dried proteinX-leu-powders can be delivered to the lung at a lower dose than for intravenous administration.

Dandelion inspired microparticles with highly efficient drug delivery to deep lung

Active pharmaceutical ingredient (API) embedded dry powder for inhalation (AeDPI) shows higher drug loading and delivery dose for directly treating various lung infections. Inspired by the dandelion, we propose a novel kind of AeDPI microparticle structure fabricated by spray freeze drying technology, which would potentially enhance the alveoli deposition efficiency. When inhaling, such microparticles are expected to be easily broken-up into fragments containing API that acts as 'seed' and could be delivered to alveoli aided by the low density 'pappus' composed of excipient. Herein, itraconazole (ITZ), a first-line drug for treating pulmonary aspergillosis, was selected as model API. TPGS, an amphiphilic surfactant, was used to achieve stable primary ITZ nanocrystal (INc) suspensions for spray freeze drying. A series of microparticles were prepared, and the dandelion-like structure was successfully achieved. The effects of feed liquid compositions and freezing parameters on the microparticle size, morphology, surface energy, crystal properties and in vitro aerosol performance were systematically investigated. The optimal sample (SF(-50)D-INc7Leu3-2) in one-way experiment showed the highest fine particle fraction of ∼ 68.96 % and extra fine particle fraction of ∼ 36.87 %, equivalently ∼ 4.60 mg and ∼ 2.46 mg could reach the lung and alveoli, respectively, when inhaling 10 mg dry powders. The response surface methodology (RSM) analysis provided the optimized design space for fabricating microparticles with higher deep lung deposition performance. This study demonstrates the advantages of AeDPI microparticle with dandelion-like structure on promoting the delivery efficiency of high-dose drug to the deep lung.

Evaluating the effect of sodium alginate and sodium carboxymethylcellulose on pulmonary delivery of levofloxacin spray-dried microparticles

BACKGROUND

Patients with cystic fibrosis commonly suffer from lung infections caused by Pseudomonas aeruginosa. Recently, the Levofloxacin (LVF) nebulizing solution (Quinsair®) has been prescribed for the antimicrobial management. The sustained-release (SR) dry powder formulation of LVF is a convenient alternative to Quinsair®. It has the potential to enhance patient convenience and decrease the likelihood of drug resistance over time.

OBJECTIVE

In this paper, we set forth to formulate and evaluate the potential application of sodium alginate (SA) and sodium carboxymethylcellulose (SCMC) for sustained pulmonary delivery of LVF.

METHODS

The spray-dried (SD) LVF microparticles were formulated using SCMC and SA along with L-leucine (Leu). The microparticles were analyzed in terms of particle size, morphology, x-ray diffraction (XRD), in-vitro drug release, and aerodynamic properties. Selected formulations were further proceeded to short-term stability test.

RESULTS

The polymer-containing samples displayed process yield of 33.31%-39.67%, mean entrapment efficiency of 89% and volume size within the range of 2-5 μm. All the hydrogel microparticles were amorphous and exhibited rounded morphology with surface indentations. Formulations with a drug-to-excipient ratio of 50:50 and higher, showed a 24-h SR. The aerodynamic parameters were fine particle fraction and emitted dose percentage ranging between 46.21%-60.6% and 66.67%-87.75%, respectively. The short-term stability test revealed that the formulation with a 50:50 drug-to-excipient ratio, containing SA, demonstrated better physical stability.

CONCLUSION

The selected formulation containing SA has the potential to extend the release duration. However, further enhancements are required to optimize its performance.

Comprehensive In Vitro and In Silico Aerodynamic Analysis of High-Dose Ibuprofen- and Mannitol-Containing Dry Powder Inhalers for the Treatment of Cystic Fibrosis

Background: Cystic fibrosis is a hereditary disease, which causes the accumulation of dense mucus in the lungs accompanied by frequent local inflammation. The non-steroidal anti-inflammatory drug ibuprofen (IBU) and the mucolytic mannitol (MAN) can treat these symptoms. Compared to per os administration, a lower dose of these drugs is sufficient to achieve the desired effect by delivering them in a pulmonary manner. However, it is still a challenge to administer high drug doses to the lungs. We aim to develop two inhaled powder formulations, a single-drug product of MAN and a combined formulation containing IBU and MAN. Methods: MAN was dissolved in an aqueous solution of Poloxamer-188 (POL). In the case of the combined formulation, a suspension was first prepared in a planetary mill via wet milling in POL medium. After the addition of leucine (LEU), the formulations were spray-dried. The prepared DPI samples were analyzed by using laser diffraction, scanning electron microscopy, powder X-ray diffraction, differential scanning calorimetry, density tests, in vitro aerodynamic studies (Andersen Cascade Impactor, Spraytec® device), in vitro dissolution tests in artificial lung fluid, and in silico tests with stochastic lung model. Results: The DPIs showed suitability for inhalation with low-density spherical particles of appropriate size. The LEU-containing systems were characterized by high lung deposition and adequate aerodynamic diameter. The amorphization during the procedures resulted in rapid drug release. Conclusions: We have successfully produced a single-drug formulation and an innovative combination formulation, which could provide complex treatment for patients with cystic fibrosis to improve their quality of life.

Inhalable nano-structured microparticles for extracellular matrix modulation as a potential delivery system for lung cancer

The use of inhalable nanoparticulate-based systems in the treatment of lung cancer allows for efficient localized delivery to the lungs with less undesirable systemic exposure. For this to be attained, the inhaled particles should have optimum properties for deposition and at the same time avoid pulmonary clearance mechanisms. Drug delivery to solid tumors is furthermore challenging, due to dense extracellular matrix (ECM) formation, which hinders the penetration and diffusion of therapeutic agents. To this end, the aim of the current work is to develop an ECM-modulating nano-structured microparticulate carrier, that not only enables the delivery of therapeutic nanoparticles (NPs) to the lungs, but also enhances their intratumoral penetration. The system is composed of acetalated maltodextrin (AcMD) NPs embedded into a water-soluble trehalose/leucine matrix, in which collagenase was loaded with different mass concentrations (10 %, 30 % and 50 %). The collagenase-containing AcMD nano-structured microparticles (MPs) exhibited suitable median volume diameters (2.58 ± 1.35 to 3.01 ± 0.68 µm), hollow corrugated morphology, sufficient redispersibility, low residual moisture content (2.71 ± 0.17 % to 3.10 ± 0.20 %), and favorable aerodynamic properties (Mass median aerodynamic diameter (MMAD): 1.93 ± 0.06 to 2.80 ± 0.10 µm and fine particle fraction (FPF): 68.02 ± 6.86 % to 69.62 ± 2.01 %). Importantly, collagenase retained as high as 89.5 ± 6.7 % of its enzymatic activity after spray drying. MPs containing 10 % mass content of collagenase did not show signs of cytotoxicity on either human lung adenocarcinoma A549 cells or lung MRC-5 fibroblasts. The nanoparticle penetration was tested using adenocarcinoma A549/MRC-5 co-culture spheroid model, where the inclusion of collagenase resulted in deeper penetration depth of AcMD-NPs.

Formulation strategies, preparation methods, and devices for pulmonary delivery of biologics

Biological products, including vaccines, blood components, and recombinant therapeutic proteins, are derived from natural sources such as humans, animals, or microorganisms and are typically produced using advanced biotechnological methods. The success of biologics, particularly monoclonal antibodies, can be attributed to their favorable safety profiles and target specificity. However, their large molecular size presents significant challenges in drug delivery, particularly in overcoming biological barriers. Pulmonary delivery has emerged as a promising route for administering biologics, offering non-invasive delivery with rapid absorption, high systemic bioavailability, and avoidance of first-pass metabolism. This review first details the anatomy and physiological barriers of the respiratory tract and the associated challenges of pulmonary drug delivery (PDD). It further discusses innovations in PDD, the impact of particle size on drug deposition, and the use of secondary particles, such as nanoparticles, to enhance bioavailability and targeting. The review also explains various devices used for PDD, including dry powder inhalers (DPIs) and nebulizers, highlighting their advantages and limitations in delivering biologics. The role of excipients in improving the stability and performance of inhalation products is also addressed. Since dry powders are considered the suitable format for delivering biomolecules, particular emphasis is placed on the excipients used in DPI development. The final section of the article reviews and compares various dry powder manufacturing methods, clarifying their clinical relevance and potential for future applications in the field of inhalable drug formulation.

Spray drying of a zinc complexing agent for inhalation therapy of pulmonary fibrosis

Pulmonary fibrosis, a disabling lung disease, results from the fibrotic transformation of lung tissue. This fibrotic transformation leads to a deterioration of lung capacity, resulting in significant respiratory distress and a reduction in overall quality of life. Currently, the frontline treatment of pulmonary fibrosis remains limited, focusing primarily on symptom relief and slowing disease progression. Bacterial infections with Pseudomonas aeruginosa are contributing to a severe progression of idiopathic pulmonary fibrosis. Phytic acid, a natural chelator of zinc, which is essential for the activation of metalloproteinase enzymes involved in pulmonary fibrosis, shows potential inhibition of LasB, a virulence factor in P. aeruginosa, and mammalian metalloproteases (MMPs). In addition, phytic acid has anti-inflammatory properties believed to result from its ability to capture free radicals, inhibit certain inflammatory enzymes and proteins, and reduce the production of inflammatory cytokines, key signaling molecules that promote inflammation. To achieve higher local concentrations in the deep lung, phytic acid was spray dried into an inhalable powder. Challenges due to its hygroscopic and low melting (25 °C) nature were mitigated by converting it to sodium phytate to improve crystallinity and powder characteristics. The addition of leucine improved aerodynamic properties and reduced agglomeration, while mannitol served as carrier matrix. Size variation was achieved by modifying process parameters and were evaluated by tools such as the Next Generation Impactor (NGI), light diffraction methods, and scanning electron microscopy (SEM). An inhibition assay for human MMP-1 (collagenase-1) and MMP-2 (gelatinase A) allowed estimation of the biological effect on tissue remodeling enzymes. The activity was also assessed with respect to inhibition of bacterial LasB. The formulated phytic acid demonstrated an IC50 of 109.7 µg/mL for LasB with viabilities > 80 % up to 188 µg/mL on A549 cells. Therefore, inhalation therapy with phytic acid-based powder shows promise as a treatment for early-stage Pseudomonas-induced pulmonary fibrosis.

Development of a proliposomal pretomanid dry powder inhaler as a novel alternative approach for combating pulmonary tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) continue as public health concerns. Inhaled drug therapy for TB has substantial benefits in combating the causal agent of TB (Mycobacterium tuberculosis). Pretomanid is a promising candidate in an optional combined regimen for XDR-TB. Pretomanid has demonstrated high potency against M. tuberculosis in both the active and latent phases. Conventional spray drying was used to formulate pretomanid as dry powder inhalers (DPIs) for deep lung delivery using a proliposomal system with a trehalose coarse excipient to enhance the drug solubility. Co-spray drying with L-leucine protected hygroscopic trehalose in formulations and improved powder aerosolization. Higher amounts of L-leucine (40-50 % w/w) resulted in the formation of mesoporous particles with high percentages of drug content and entrapment efficiency. The aerosolized powders demonstrated both geometric and median aerodynamic diameters < 5 µm with > 90 % emitted dose and > 50 % fine particle fraction. Upon reconstitution in simulated physiological fluid, the proliposomes completely converted to liposomes, exhibiting suitable particle sizes (130-300 nm) with stable colloids and improving drug solubility, leading to higher drug dissolution compared to the drug alone. Inhalable pretomanid showed higher antimycobacterial activity than pretomanid alone. The formulations were safe for all broncho-epithelial cell lines and alveolar macrophages, thus indicating their potential suitability for DPIs targeting pulmonary TB.

Nanocrystal Agglomerates of Curcumin Prepared by Electrospray Drying as an Excipient-Free Dry Powder for Inhalation

Curcumin has shown beneficial effects on pulmonary diseases with chronic inflammation or abnormal inflammatory responses, including chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis. Clinical applications of curcumin are limited due to its chemical instability in solution, low water solubility, poor oral bioavailability, and intestinal and liver first-pass metabolism. Pulmonary delivery of curcumin can address these challenges and provide a high concentration in lung tissues. The purpose of the current work was to prepare a novel inhalable dry powder of curcumin nanocrystals without added excipients using electrospray drying (ED) with improved dissolution and aerosolization properties. ED of curcumin was performed at 2 and 4% w/v concentrations in acetone. Physicochemical properties of the formulated powders were evaluated by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), density and powder flow measurements, and in vitro dissolution. The in vitro deposition studies were conducted using next-generation impactor (NGI) and aerosol performance and aerodynamic particle size parameters were calculated for prepared formulations. ED could produce agglomerates of nanocrystals with a size of about 500 nm at an acceptable yield of about 50%. PXRD and FTIR data revealed that prepared nanocrystals were in a stable crystalline state. The bulk and tapped density of prepared agglomerates were in the range appropriate for pulmonary delivery. Formed nanocrystals could significantly improve the dissolution rate of water-insoluble curcumin. The optimized formulation exhibited acceptable recovered dose percentage, high emitted dose percentage, optimum mean mass median aerodynamic diameter, small geometric standard deviation, and high fine-particle fraction that favors delivery of curcumin to the deep lung regions. The ED proved to be an efficient technique to prepare curcumin nanocrystals for pulmonary delivery in a single step, at a mild condition, and with no surfactant.

Leucine as a Moisture-Protective Excipient in Spray-Dried Protein/Trehalose Formulation

The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) was dissolved in water with varied amounts of Leu (0 - 40%, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22°C/55% RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20% (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0%, 5%, and 10% (w/w) Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred in the 0% Leu formulation. However, adding as little as 5% (w/w) Leu inhibited this recrystallization during the water sorption/desorption cycle. In addition, after storage, the formulations with higher Leu contents showed reduced water uptake. Instead of observing recrystallization of amorphous Tre in 0%, 5%, and 10% (w/w) Leu formulations, recrystallization of amorphous Leu was noted in the 5% and 10% (w/w) Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.

Dry Powder Inhaler Formulation of Lactobacillus rhamnosus GG Targeting Pseudomonas aeruginosa Infection in Bronchiectasis Maintenance Therapy

The inhaled delivery of lactic acid bacteria (LAB) probiotics has been demonstrated to exert therapeutic benefits to the lungs due to LAB's immunomodulatory activities. The development of inhaled probiotics formulation, however, is in its nascent stage limited to nebulized LAB. We developed a dry powder inhaler (DPI) formulation of lactobacillus rhamnosus GG (LGG) intended for bronchiectasis maintenance therapy by spray freeze drying (SFD). The optimal DPI formulation (i.e., LGG: mannitol: lactose: leucine = 35: 45: 15: 5 wt.%) was determined based on the aerosolization efficiency (86% emitted dose and 26% respirable fraction) and LGG cell viability post-SFD (7 log CFU/mL per mg powder). The optimal DPI formulation was evaluated and compared to lyophilized naked LGG by its (1) adhesion capacity and cytotoxicity to human lung epithelium cells (i.e., A549 and 16HBE14o- cells) as well as its (2) effectiveness in inhibiting the growth and adhesion of Pseudomonas aeruginosa to lung cells. The optimal DPI of LGG exhibited similar non-cytotoxicity and adhesion capacity to lung cells to naked LGG. The DPI of LGG also inhibited the growth and adhesion of P. aeruginosa to the lung cells as effectively as the naked LGG. The present work established the feasibility of delivering the LAB probiotic by the DPI platform without adversely affecting LGG's anti-pseudomonal activities.

Inhalable solid lipid nanoparticles of levofloxacin for potential tuberculosis treatment

Delivering novel antimycobacterial agents through the pulmonary route using nanoparticle-based systems shows promise for treating diseases like tuberculosis. However, creating dry powder inhaler (DPI) with suitable aerodynamic characteristics while preserving nanostructure integrity and maintaining bioactivity until the active ingredient travels deeply into the lungs is a difficult challenge. We developed DPI formulations containing levofloxacin-loaded solid lipid nanoparticles (SLNs) via spray-drying technique with tailored aerosolization characteristics for effective inhalation therapy. A range of biophysical techniques, including transmission electron microscopy, confocal microscopy, and scanning electron microscopy were used to measure the morphologies and sizes of the spray-dried microparticles that explored both the geometric and aerodynamic properties. Spray drying substantially reduced the particle sizes of the SLNs while preserving their nanostructural integrity and enhancing aerosol dispersion with efficient mucus penetration. Despite a slower uptake rate compared to plain SLNs, the polyethylene glycol modified formulations exhibited enhanced cellular uptake in both A549 and NR8383 cell lines. The percent viability of Mycobacterium bovis had dropped to nearly 0 % by day 5 for both types of SLNs. Interestingly, the levofloxacin-loaded SLNs demonstrated a lower minimum bactericidal concentration (0.25 µg/mL) compared with pure levofloxacin (1 µg/mL), which indicated the formulations have potential as effective treatments for tuberculosis.

Preparation and Evaluation of Inhalable Microparticles with Improved Aerodynamic Performance and Dispersibility Using L-Leucine and Hot-Melt Extrusion

Dry-powder inhalers (DPIs) are valued for their stability but formulating them is challenging due to powder aggregation and limited flowability, which affects drug delivery and uniformity. In this study, the incorporation of L-leucine (LEU) into hot-melt extrusion (HME) was proposed to enhance dispersibility while simultaneously maintaining the high aerodynamic performance of inhalable microparticles. This study explored using LEU in HME to improve dispersibility and maintain the high aerodynamic performance of inhalable microparticles. Formulations with crystalline itraconazole (ITZ) and LEU were made via co-jet milling and HME followed by jet milling. The LEU ratio varied, comparing solubility, homogenization, and aerodynamic performance enhancements. In HME, ITZ solubility increased, and crystallinity decreased. Higher LEU ratios in HME formulations reduced the contact angle, enhancing mass median aerodynamic diameter (MMAD) size and aerodynamic performance synergistically. Achieving a maximum extra fine particle fraction of 33.68 ± 1.31% enabled stable deep lung delivery. This study shows that HME combined with LEU effectively produces inhalable particles, which is promising for improved drug dispersion and delivery.

Particulate bioaerogels for respiratory drug delivery

The bioaerogel microparticles have been recently developed for respiratory drug delivery and attract fast increasing interests. These highly porous microparticles have ultralow density and hence possess much reduced aerodynamic diameter, which favour them with greatly enhanced dispersibility and improved aerosolisation behaviour. The adjustable particle geometric dimensions by varying preparation methods and controlling operation parameters make it possible to fabricate bioaerogel microparticles with accurate sizes for efficient delivery to the targeted regions of respiratory tract (i.e. intranasal and pulmonary). Additionally, the technical process can provide bioaerogel microparticles with the opportunities of accommodating polar, weak polar and non-polar drugs at sufficient amount to satisfy clinical needs, and the adsorbed drugs are primarily in the amorphous form that potentially can facilitate drug dissolution and improve bioavailability. Finally, the nature of biopolymers can further offer additional advantageous characteristics of improved mucoadhesion, sustained drug release and subsequently elongated time for continuous treatment on-site. These fascinating features strongly support bioaerogel microparticles to become a novel platform for effective delivery of a wide range of drugs to the targeted respiratory regions, with increased drug residence time on-site, sustained drug release, constant treatment for local and systemic diseases and anticipated better-quality of therapeutic effects.

Building respirable powder architectures: utilizing polysaccharides for precise control of particle morphology for enhanced pulmonary drug delivery

INTRODUCTION

Dry powder inhaler (DPI) formulations are gaining attention as universal formulations with applications in a diverse range of drug formulations. The practical application of DPIs to pulmonary drugs requires enhancing their delivery efficiency to the target sites for various treatment modalities. Previous reviews have not explored the relation between particle morphology and delivery to different pulmonary regions. This review introduces new approaches to improve targeted DPI delivery using novel particle design such as supraparticles and metal-organic frameworks based on cyclodextrin.

AREAS COVERED

This review focuses on the design of DPI formulations using polysaccharides, promising excipients not yet approved by regulatory agencies. These excipients can be used to design various particle morphologies by controlling their physicochemical properties and manufacturing methods.

EXPERT OPINION

Challenges associated with DPI formulations include poor access to the lungs and low delivery efficiency to target sites in the lung. The restricted applicability of typical excipients contributes to their limited use. However, new formulations based on polysaccharides are expected to establish a technological foundation for the development of DPIs capable of delivering modalities specific to different lung target sites, thereby enhancing drug delivery.

Co-spray dried inhalable composite powders of ciprofloxacin and alginate oligosaccharide as anti-biofilm therapy

The treatment of chronic respiratory infections caused by biofilm formation are extremely challenging owing to poor drug penetration into the complex biofilm structure and high drug resistance. Local delivery of an antibiotic together with a non-antibiotic adjuvant to the lungs could often enhance the therapeutic responses by targeting different bacterial growth pathways and minimizing drug resistance. In this study, we designed new inhalable dry powders containing ciprofloxacin (CIP) and OligoG (Oli, a low-molecular-weight alginate oligosaccharide impairing the mucoid biofilms by interacting with their cationic ions) to combat respiratory bacterial biofilm infections. The resulting powders were characterized with respect to their morphology, solid-state property, surface chemistry, moisture sorption behavior, and dissolution rate. The aerosol performance and storage stability of the dry powders were also evaluated. The results showed that inhalable dry powders composed of CIP and Oli could be readily accomplished via the wet milling and spray drying process. Upon the storage under 20 ± 2 °C/20 ± 2 % relative humidity (RH) for one month, there was no significant change in the in vitro aerosol performances of the dry powders. In contrast, the dry powders became non-inhalable following the storage at 20 ± 2 °C/53 ± 2 % RH for one month due to the hygroscopic nature of Oli, which could be largely prevented by incorporation of leucine. Collectively, this study suggests that the newly developed co-spray-dried powders composed of CIP and Oli might represent a promising and alternative treatment strategy against respiratory bacterial biofilm infections.

Spray-Dried Mucoadhesive Re-dispersible Gargle of Chlorhexidine for Improved Response Against Throat Infection: Formulation Development, In Vitro and In Vivo Evaluation

Drug delivery to the buccal mucosa is one of the most convenient ways to treat common mouth problems. Here, we propose a spray-dried re-dispersible mucoadhesive controlled release gargle formulation to improve the efficacy of chlorhexidine. The present investigation portrays an approach to get stable and free-flowing spray-dried porous aggregates of chlorhexidine-loaded sodium alginate nanoparticles. The ionic gelation technique aided with the chlorhexidine's positive surface charge-based crosslinking, followed by spray drying of the nanoparticle's dispersion in the presence of lactose- and leucine-yielded nano-aggregates with good flow properties and with a size range of about 120-350 nm. Provided with the high entrapment efficiency (87%), the particles showed sustained drug release behaviors over a duration of 10 h, where 87% of the released drug got permeated within 12 h. The antimicrobial activity of the prepared formulation was tested on S. aureus, provided with a higher zone of growth inhibition than the marketed formulation. Aided with an appropriate mucoadhesive strength, this product exhibited extended retention of nanoparticles in the throat region, as shown by in vivo imaging results. In conclusion, the technology, provided with high drug retention and extended effect, could be a potential candidate for treating several types of throat infections.

Inhaled JAK Inhibitor GDC-0214 Nanoaggregate Powder Exhibits Improved Pharmacokinetic Profile in Rats Compared to the Micronized Form: Benefits of Thin Film Freezing

Asthma is a common chronic disease affecting the airways in the lungs. The receptors of allergic cytokines, including interleukin (IL)-4, IL-5, and IL-13, trigger the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, which involves the pathogenesis of asthma. GDC-0214 is a JAK inhibitor that was developed as a potent and selective target for the treatment of asthma, specifically targeting the lungs. While inhaled GDC-0214 is a promising novel treatment option against asthma, improvement is still needed to achieve increased potency of the powder formulation and a reduced number of capsules containing powder to be inhaled. In this study, high-potency amorphous powder formulations containing GDC-0214 nanoaggregates for dry powder inhalation were developed using particle engineering technology, thin film freezing (TFF). A high dose per capsule was successfully achieved by enhancing the solubility of GDC-0214 and powder conditioning. Lactose and/or leucine as excipients exhibited optimum stability and aerosolization of GDC-0214 nanoaggregates, and aerosolization of the dose was independent of air flow through the device between 2 and 6 kPa pressure drops. In the rat PK study, formulation F20, which contains 80% GDC-0214 and 20% lactose, resulted in the highest AUC0-24h in the lungs with the lowest AUC0-24h in the plasma that corresponds to a 4.8-fold higher ratio of the lung-to-plasma exposures compared to micronized crystalline GDC-0214 powder administered by dry powder inhalation. Therefore, GDC-0214 nanoaggregates produced by TFF provided an improved dry powder for inhalation that can lead to enhanced therapeutic efficacy with a lower risk of systemic toxicity.

Repurposing ebselen as an inhalable dry powder to treat respiratory tract infections

Respiratory tract infections (RTIs) are one of the leading causes of death globally, lately exacerbated by the increasing prevalence of antimicrobial resistance. While antimicrobial resistance could be overcome by developing new antimicrobial agents, the use of a safe repurposed agent having potent antimicrobial activity against various RTIs can be an efficient and cost-effective alternative to overcome the long and complex process of developing and testing new drugs. Ebselen, a synthetic organoselenium drug originally developed to treat noise-inducing hearing problems, has shown promising antimicrobial activity in vitro against several respiratory pathogens including viruses (e.g., SARS-CoV-2, influenza A virus) and bacteria (e.g., Mycobacterium tuberculosis, Streptococcus pneumoniae, and Staphylococcus aureus). Inhaled drug delivery is considered a promising approach for treating RTIs, as it can ensure effective drug concentrations at a lower dose, thereby minimizing the side effects that are often encountered by using oral or injectable drugs. In this study, we developed inhalable ebselen dry powder formulations using a spray-drying technique. The amino acids leucine, methionine, and tryptophan were incorporated with ebselen to enhance the yield and aerosolization of the dry powders. The amino acid-containing ebselen dry powders showed a better yield (37-56.4 %) than the amino acid-free formulation (30.9 %). All dry powders were crystalline in nature. The mass median aerodynamic diameter (MMAD) was less than 5 µm for amino acids containing dry powders (3-4 µm) and slightly higher (5.4 µm) for amino acid free dry powder indicating their suitability for inhalation. The aerosol performance was higher when amino acids were used, and the leucine-containing ebselen dry powder showed the highest emitted dose (84 %) and fine particle fraction (68 %). All amino acid formulations had similar cytotoxicity as raw ebselen, tested in respiratory cell line (A549 cells), with half-maximal inhibitory concentrations (IC50) between 100 and 250 μg/mL. Raw ebselen and amino acid-containing dry powders showed similar potent antibacterial activity against the Gram-positive bacteria S. aureus and S. pneumoniae with minimum inhibitory concentrations of 0.31 μg/mL and 0.16 μg/mL, respectively. On the other hand, raw ebselen and the formulations showed limited antimicrobial activity against the Gram-negative pathogens Pseudomonas aeruginosa and Klebsiella pneumoniae. In summary, in this study we were able to develop amino-acid-containing inhalable dry powders of ebselen that could be used against different respiratory pathogens, especially Gram-positive bacteria, which could ensure more drug deposition in the respiratory tract, including the lungs. DPIs are generally used to treat lung (lower respiratory tract) diseases. However, DPIs can also be used to treat both upper and lower RTIs. The deposition of the dry powder in the respiratory tract is dependent on its physicochemical properties and this properties can be modulated to target the intended site of infection (upper and/or lower respiratory tract). Further studies will allow the development of similar formulations of individual and/or combination of antimicrobials that could be used to inhibit a number of respiratory pathogens.

Towards More Precise Targeting of Inhaled Aerosols to Different Areas of the Respiratory System

Pharmaceutical aerosols play a key role in the treatment of lung disorders, but also systemic diseases, due to their ability to target specific areas of the respiratory system (RS). This article focuses on identifying and clarifying the influence of various factors involved in the generation of aerosol micro- and nanoparticles on their regional distribution and deposition in the RS. Attention is given to the importance of process parameters during the aerosolization of liquids or powders and the role of aerosol flow dynamics in the RS. The interaction of deposited particles with the fluid environment of the lung is also pointed out as an important step in the mass transfer of the drug to the RS surface. The analysis presented highlights the technical aspects of preparing the precursors to ensure that the properties of the aerosol are suitable for a given therapeutic target. Through an analysis of existing technical limitations, selected strategies aimed at enhancing the effectiveness of targeted aerosol delivery to the RS have been identified and presented. These strategies also include the use of smart inhaling devices and systems with built-in AI algorithms.

Targeted Molecular Therapeutics for Pulmonary Diseases: Addressing the Need for Precise Drug Delivery

Respiratory diseases are a major concern in public health, impacting a large population worldwide. Despite the availability of therapies that alleviate symptoms, selectively addressing the critical points of pathopathways remains a major challenge. Innovative formulations designed for reaching these targets within the airways, enhanced selectivity, and prolonged therapeutic effects offer promising solutions. To provide insights into the specific medical requirements of chronic respiratory diseases, the initial focus of this chapter is directed on lung physiology, emphasizing the significance of lung barriers. Current treatments involving small molecules and the potential of gene therapy are also discussed. Additionally, we will explore targeting approaches, with a particular emphasis on nanoparticles, comparing targeted and non-targeted formulations for pulmonary administration. Finally, the potential of inhaled sphingolipids in the context of respiratory diseases is briefly discussed, highlighting their promising prospects in the field.

Development of inhalation powders containing lactic acid bacteria with antimicrobial activity against Pseudomonas aeruginosa

OBJECTIVES

The aim of the project was to develop and characterise powders containing a probiotic (Lactiplantibacillus plantarum [Lpb. plantarum], Lacticaseibacillus rhamnosus, or Lactobacillus acidophilus) to be administered to the lung for the containment of pathogen growth in patients with lung infections.

METHODS

The optimised spray drying process for the powder manufacturing was able to preserve viability of the bacteria, which decreased of only one log unit and was maintained up to 30 days.

RESULTS

Probiotic powders showed a high respirability (42%-50% of particles had a size < 5 µm) suitable for lung deposition and were proven safe on A549 and Calu-3 cells up to a concentration of 107 colony-forming units/mL. The Lpb. plantarum adhesion to both cell lines tested was at least 10%. Surprisingly, Lpb. plantarum powder was bactericidal at a concentration of 106 colony-forming units/mL on P. aeruginosa, whereas the other two strains were bacteriostatic.

CONCLUSION

This work represents a promising starting point to consider a probiotic inhalation powder a value in keeping the growth of pathogenic microflora in check during the antibiotic inhalation therapy suspension in cystic fibrosis treatment regimen. This approach could also be advantageous for interfering competitively with pathogenic bacteria and promoting the restoration of the healthy microbiota.

Conversion of liquid chitosan-based nanoemulsions into inhalable solid microparticles: Process challenges with polysaccharide

Solid particles ≤5 μm are essential to allow lower lung deposition and macrophage phagocytosis of anti-tubercular drugs. Decorating liquid nanoemulsion of anti-tubercular drug with macrophage-specific chitosan and chitosan-folate conjugate and spray drying the nanoemulsion with lactose produced oversized solid particles due to polysaccharide binding effects. This study designed solid nanoemulsion using lactose as the primary solid carrier and explored additives and spray-drying variables to reduce the binding and particle growth effects of chitosan. Deposition of magnesium stearate on lactose negated chitosan-inducible excessive lactose-liquid nanoemulsion binding and solid particle growth. Moderating the adhesion of chitosan-decorated liquid nanoemulsion onto lactose produced smooth-surface solid microparticles (size: 5.45 ± 0.26 μm; roughness: ∼80 nm) with heterogeneous size (span: 1.87 ± 1.21) through plasticization of constituent materials of nanoemulsion and lactose involving OH/N-H, C-H, CONH and/or COO moieties. Smaller solid particles could attach onto the larger particles with minimal steric hindrance by smooth surfaces. Together with round solid particulate structures (circularity: 0.919 ± 0.002), good pulmonary inhalation beneficial for treatment of pulmonary tuberculosis as well as other diseases is conferred.

Stability of Naked Nucleic Acids under Physical Treatment and Powder Formation: Suitability for Development as Dry Powder Formulations for Inhalation

A number of functional nucleic acids, including plasmid DNA (pDNA) and small interfering RNA (siRNA), have been attracting increasing attention as new therapeutic modalities worldwide. Dry pDNA and siRNA powder formulations for inhalation are considered practical in clinical applications for respiratory diseases. However, physical stresses in the powder-forming process may destabilize nucleic acids, particularly when vectors with stabilizing effects are not used. We herein compare the stability of naked pDNA and siRNA through various physical treatments and two powder-forming processes. The structural and functional integrities of pDNA were markedly reduced via sonication, heating, and atomization, whereas those of siRNA were preserved throughout all of the physical treatments investigated. Spray-dried and spray-freeze-dried powders of siRNA maintained their structural and functional integrities, whereas those of pDNA did not. These results demonstrate that siRNA is more suitable for powder formation in the naked state than pDNA due to its higher stability under physical treatments. Furthermore, a spray-freeze-dried powder with a high content of naked siRNA (12% of the powder) was successfully produced that preserved its structural and functional integrities, achieving high aerosol performance with a fine particle fraction of approximately 40%.

Improvement in Inhalation Properties of Theophylline and Levofloxacin by Co-Amorphization and Enhancement in Its Stability by Addition of Amino Acid as a Third Component

Co-amorphous systems are amorphous formulations stabilized by the miscible dispersion of small molecules. This study aimed to design a stable co-amorphous system for the co-delivery of two drugs to the lungs as an inhaled formulation. Theophylline (THE) and levofloxacin (LEV) were used as model drugs for treating lung infection with inflammation. Leucine (LEU) or tryptophan (TRP) was employed as the third component to improve the inhalation properties. The co-amorphous system containing THE and LEV in an equal molar ratio was successfully prepared via spray drying where reduction of the particle size and change to the spherical morphology were observed. The addition of LEU or TRP at a one-tenth molar ratio to THE-LEV did not affect the formation of the co-amorphous system, but only TRP acted as an antiplasticizer. The Fourier transform infrared spectroscopy spectra revealed intermolecular interactions between THE and LEV in the co-amorphous system that were retained after the addition of LEU or TRP. The co-amorphous THE-LEV system exhibited better in vitro aerodynamic performance than a physical mixture of these compounds and permitted the simultaneous delivery of both drugs in various stages. The co-amorphous THE-LEV system crystallized at 40 °C, and this crystallization was not prevented by LEU. However, THE-LEV-TRP maintained its amorphous state for 1 month. Thus, TRP can act as a third component to improve the physical stability of the co-amorphous THE-LEV system, while maintaining the enhanced aerodynamic properties.

A dry powder formulation for peripheral lung delivery and absorption of an anti-SARS-CoV-2 ACE2 decoy polypeptide

One of the strategies proposed for the neutralization of SARS-CoV-2 has been to synthetize small proteins able to act as a decoy towards the virus spike protein, preventing it from entering the host cells. In this work, the incorporation of one of these proteins, LCB1, within a spray-dried formulation for inhalation was investigated. A design of experiments approach was applied to investigate the optimal condition for the manufacturing of an inhalable powder. The lead formulation, containing 6% w/w of LCB1 as well as trehalose and L-leucine as excipients, preserved the physical stability of the protein and its ability to neutralize the virus. In addition, the powder had a fine particle fraction of 58.6% and a very high extra-fine particle fraction (31.3%) which could allow a peripheral deposition in the lung. The in vivo administration of the LCB1 inhalation powder showed no significant difference in the pharmacokinetic from the liquid formulation, indicating the rapid dissolution of the microparticles and the protein capability to translocate into the plasma. Moreover, LCB1 in plasma samples still maintained the ability to neutralize the virus. In conclusion, the optimized spray drying conditions allowed to obtain an inhalation powder able to preserve the protein biological activity, rendering it suitable for a systemic prevention of the viral infection via pulmonary administration.

Inhalable dry powder containing remdesivir and disulfiram: Preparation and in vitro characterization

The respiratory tract, as the first and most afflicted target of many viruses such as SARS-CoV-2, seems to be the logical choice for delivering antiviral agents against this and other respiratory viruses. A combination of remdesivir and disulfiram, targeting two different steps in the viral replication cycle, has showed synergistic activity against SARS-CoV-2 in-vitro. In this study, we have developed an inhalable dry powder containing a combination of remdesivir and disulfiram utilizing the spray-drying technique, with the final goal of delivering this drug combination to the respiratory tract. The prepared dry powders were spherical, and crystalline. The particle size was between 1 and 5 μm indicating their suitability for inhalation. The spray-dried combinational dry powder containing remdesivir and disulfiram (RDSD) showed a higher emitted dose (ED) of >88% than single dry powder of remdesivir (RSD) (∼72%) and disulfiram (DSD) (∼84%), with a fine particle fraction (FPF) of ∼55%. Addition of L-leucine to RDSD showed >60% FPF with a similar ED. The in vitro aerosolization was not significantly affected after the stability study conducted at different humidity conditions. Interestingly, the single (RSD and DSD) and combined (RDSD) spray-dried powders showed limited cellular toxicity (CC50 values from 39.4 to >100 µM), while maintaining their anti-SARS-CoV-2 in vitro (EC50 values from 4.43 to 6.63 µM). In a summary, a combinational dry powder formulation containing remdesivir and disulfiram suitable for inhalation was developed by spray-drying technique which showed high cell viability in the respiratory cell line (Calu-3 cells) retaining their anti-SARS-CoV-2 property. In the future, in vivo studies will test the ability of these formulations to inhibit SARS-CoV-2 which is essential for clinical translation.

Enhanced powder dispersion of dual-excipient spray-dried powder formulations of a monoclonal antibody and its fragment for local treatment of severe asthma

The advent of biologics has brought renewed hope for patients with severe asthma, a condition notorious for being hampered by poor response to conventional therapies and adverse drug reactions owing to corticosteroid dependence. However, biologics are administered as injections, thereby precluding the benefits inhalation therapy could offer such as increased bioavailability at the site of action, minimal systemic side effects, non-invasiveness, and self-administration. Here, 2-hydroxypropyl-beta-cyclodextrin and ʟ-leucine were co-spray-dried, as protein stabiliser and dispersion enhancer, respectively, at various weight ratios to produce a series of formulation platforms. Powder aerosolisation characteristics and particle morphology were assessed for suitability for pulmonary delivery. The selected platform with the best aerosol performance, a 1:1 ratio of the excipients, was then incorporated with a monoclonal antibody directed against IL-4 receptor alpha or its antigen-binding fragment. The dual-excipient antibody formulations exhibited emitted fraction of at least 80% and fine particle fraction exceeding 60% in cascade impactor study, while the residual moisture content was within a desirable range between 1% and 3%. The in vitro antigen-binding ability and inhibitory potency of the spray-dried antibody were satisfactorily preserved. The results from this study corroborate the viability of inhaled solid-state biomacromolecules as a promising treatment approach for asthma.

Pharmacokinetic Considerations for Optimizing Inhaled Spray-Dried Pyrazinoic Acid Formulations

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of death with 1.6 million deaths worldwide reported in 2021. Oral pyrazinamide (PZA) is an integral part of anti-TB regimens, but its prolonged use has the potential to drive the development of PZA-resistant Mtb. PZA is converted to the active moiety pyrazinoic acid (POA) by the Mtb pyrazinamidase encoded by pncA, and mutations in pncA are associated with the majority of PZA resistance. Conventional oral and parenteral therapies may result in subtherapeutic exposure in the lung; hence, direct pulmonary administration of POA may provide an approach to rescue PZA efficacy for treating pncA-mutant PZA-resistant Mtb. The objectives of the current study were to (i) develop novel dry powder POA formulations, (ii) assess their feasibility for pulmonary delivery using physicochemical characterization, (iii) evaluate their pharmacokinetics (PK) in the guinea pig model, and (iv) develop a mechanism-based pharmacokinetic model (MBM) using in vivo PK data to select a formulation providing adequate exposure in epithelial lining fluid (ELF) and lung tissue. We developed three POA formulations for pulmonary delivery and characterized their PK in plasma, ELF, and lung tissue following passive inhalation in guinea pigs. Additionally, the PK of POA following oral, intravenous, and intratracheal administration was characterized in guinea pigs. The MBM was used to simultaneously model PK data following administration of POA and its formulations via the different routes. The MBM described POA PK well in plasma, ELF, and lung tissue. Physicochemical analyses and MBM predictions suggested that POA maltodextrin was the best among the three formulations and an excellent candidate for further development as it has: (i) the highest ELF-to-plasma exposure ratio (203) and lung tissue-to-plasma exposure ratio (30.4) compared with POA maltodextrin and leucine (75.7/16.2) and POA leucine salt (64.2/19.3) and (ii) the highest concentration in ELF (CmaxELF: 171 nM) within 15.5 min, correlating with a fast transfer into ELF after pulmonary administration (KPM: 22.6 1/h). The data from the guinea pig allowed scaling, using the MBM to a human dose of POA maltodextrin powder demonstrating the potential feasibility of an inhaled product.

Spray-Dried Inhalable Microparticles Combining Remdesivir and Ebselen against SARS-CoV-2 Infection

There is a continuous effort to develop efficient treatments for coronavirus disease 2019 (COVID-19) and other viral respiratory diseases. Among the different strategies, inhaled treatment is considered one of the most logical and efficient approaches to treating COVID-19, as the causative "SARS-CoV-2 virus RNA" predominantly infects the respiratory tract. COVID-19 treatments initially relied on repurposed drugs, with a few additional strategies developed during the last two years, and all of them are based on monotherapy. However, drug combinations have been found to be more effective than monotherapy in other viral diseases such as HIV, influenza, and hepatitis C virus. In the case of SARS-CoV-2 infection, in vitro studies have shown synergistic antiviral activity combining remdesivir with ebselen, an organoselenium compound. Therefore, these drug combinations could ensure better therapeutic outcomes than the individual agents. In this study, we developed a dry powder formulation containing remdesivir and ebselen using a spray-drying technique and used L-leucine as an aerosolization enhancer. The prepared dry powders were spherical and crystalline, with a mean particle size between 1 and 3 µm, indicating their suitability for inhalation. The emitted dose (ED) and fine particle fraction (FPF) of remdesivir- and ebselen-containing dry powders were ~80% and ~57% when prepared without L-leucine. The ED as well as the FPF significantly increased with values of >86% and >67%, respectively, when L-leucine was incorporated. More importantly, the single and combinational dry powder of remdesivir and ebselen showed minimal cytotoxicity (CC50 > 100 μM) in Calu-3 cells, retaining their anti-SARS-CoV-2 properties (EC50 2.77 to 18.64 μM). In summary, we developed an inhalable dry powder combination of remdesivir and ebselen using a spray-drying technique. The spray-dried inhalable microparticles retained their limited cytotoxicity and specific antiviral properties. Future in vivo studies are needed to verify the potential use of these remdesivir/ebselen combinational spray-dried inhalable microparticles to block the SARS-CoV-2 replication in the respiratory tract.

Spray Dried Progesterone Formulations for Carrier Free Dry Powder Inhalation

Low oral absorption and extensive first pass metabolism of progesterone is reported for many oral formulations which warrants investigation into other routes of administration. It is the aim of this study to investigate the generation of inhaled formulations of progesterone though a spray drying approach with a focus on how spray drying impacts the physicochemical properties of progesterone. Formulations of progesterone with L-leucine and hydroxypropyl methylcellulose acetate succinate (HPMCAS) are reported to this aim. X-ray diffraction, spectroscopy and thermal analysis were used to characterise these formulations and confirmed that progesterone crystallises as the Form II polymorph during spray drying regardless of the solvent used. The resultant formulations showed higher aqueous solubility than progesterone Form I starting material and the addition of HPMCAS was shown to temporarily enable a supersaturated state. Thermal analysis was used to show that the Form II polymorph was sensitive to transformation to Form I during heating. The addition of L-leucine to the formulations reduced the temperature for the polymorphic transformation by ∼10 °C. However, when HPMCAS was added to the formulation, the Form II polymorph was prevented from transforming to the Form I polymorph. Cascade impaction was used to determine the aerosol performance of the spray dried powders and showed promising lung deposition profiles (mass median aerodynamic diameter 5 µm) with significant variation depending on the organic solvent used and the ratio of organic to aqueous phase in the feedstock. However, further optimisation of formulations was required to direct more progesterone into the alveolar regions. The addition of HPMCAS was seen to increase the alveolar deposition and therefore formed a formulation with a lower fine particle fraction and mass median aerodynamic diameter. The most suitable formulation for inhalation was formed from a 50:50 acetone:water destockck and showed an ED, FPF and FPD of 81.7%, 44.5% and 7.3 mg respectively. Therefore, HPMCAS is suggested as a suitable excipient to increase solubility, prevent polymorphic transformation and improve inhalation properties of spray dried progesterone formulations. This study highlights the use of spray drying to form inhalable progesterone powders with higher solubility which may broaden the application of this medicine.

Quality by Design - Spray drying of Ciprofloxacin-Quercetin Fixed-Dose Combination Intended for Inhalation

Spray drying is a well-suited technique for producing fixed-dose drug combinations. There has been a growing interest in utilizing spray drying to engineer carrier-free inhalable drug particles. The aim of this study was to understand and optimise the spray drying process of a ciprofloxacin-quercetin fixed dose combination intended for pulmonary administration. A 2^4-1 fractional factorial design and multivariate data analysis was used to identify important process parameters and investigate correlations with particle characteristics. The independent variables were solute concentration along with the processing parameters: solution flow rate, atomizing air flow rate and inlet temperature. The dependent variables included particle size distribution, yield and residual moisture content (RMC). Correlations between dependent and independent variables were further investigated via principal component analysis. Overall, solution flow rate, atomizing air flow rate and inlet temperature were found to affect the particle size D_(v,50) and D_(v,90) while the solute concentration and the atomizing air flow rate mainly affected the span. The inlet temperature was the most important parameter affecting the RMC and the yield. The formulation with optimized independent variables had a D_(v,50) and span values of 2.42 µm and 1.81 with excellent process yield > 70% and low RMC i.e. 3.4%. The optimized formulation was further investigated for its in vitro aerosolization performance using next generation impactor (NGI); it exhibited high emitted dose (ED > 80%) and fine particle fractions (FPF > 70%) for both drugs.

Customizable Resveratrol Spray-dried Micro-composites for Inhalation as a Promising Contender for Treatment of Idiopathic Pulmonary Fibrosis

The past decades have witnessed tremendous expansion in utilization of plant-derived medicines as resveratrol (RES) in treating several diseases like idiopathic pulmonary fibrosis (IPF). RES can exhibit its role in treating IPF via its outstanding antioxidant and anti-inflammatory activities. The goal of this work was to formulate RES-loaded spray-dried composite microparticles (SDCMs) suitable for pulmonary delivery via dry powder inhaler (DPI). They were prepared by spray drying of a previously prepared RES-loaded bovine serum albumin nanoparticles (BSA NPs) dispersion using different carriers. RES-loaded BSA NPs, prepared by the desolvation technique, acquired suitable particle size of 177.67±0.95 nm and entrapment efficiency of 98.7±0.35% with perfectly uniform size distribution and high stability. Considering the attributes of the pulmonary route, NPs were co-spray dried with compatible carriers viz. mannitol, dextran, trehalose, leucine, glycine, aspartic acid, and glutamic acid to fabricate SDCMs. All formulations showed suitable mass median aerodynamic diameter less than 5 µm; that is suitable for deep lung deposition. However, the best aerosolization behavior was attained from using leucine with fine particle fraction (FPF) of 75.74%, followed by glycine with FPF of 54.7%. Finally, a pharmacodynamic study was conducted on bleomycin-induced mice, and it strongly revealed the role of the optimized formulations in alleviating PF through suppressing the levels of hydroxyproline, tumor necrosis factor-α and matrix metalloproteinase-9 with obvious improvements in the treated lung histopathology. These findings indicate that in addition to leucine, the glycine amino acid, which is not commonly used yet, is very promising in the formulation of DPIs.

Dual functional pullulan-based spray-dried microparticles for controlled pulmonary drug delivery

Two main challenges are associated with current spray-dried microparticles for inhalation, including the enhancement of aerosolization performance of microparticles and the creation of sustained drug release for continuous treatment on-site. For achieving these purposes, pullulan was explored as a novel excipient to prepare spray-dried inhalable microparticles (with salbutamol sulphate, SS, as a model drug), which were further modified by additives of leucine (Leu), ammonium bicarbonate (AB), ethanol and acetone. It was demonstrated that all pullulan-based spray-dried microparticles had improved flowability and enhanced aerosolization behavior, with the fine particle (<4.46µm) fraction of 42.0-68.7% w/w, much higher than 11.4% w/w of lactose-SS. Moreover, all modified microparticles showed augmented emitted fractions of 88.0-96.9% w/w, over 86.5% w/w of pullulan-SS. The pullulan-Leu-SS and pullulan-(AB)-SS microparticles demonstrated further increased fine particle (<1.66µm) doses of 54.7µg and 53.3µg respectively, surpassing that (49.6µg) of pullulan-SS, suggesting an additionally increased drug deposition in the deep lungs. Furthermore, pullulan-based microparticles revealed sustained drug release profiles with elongated time (60mins) over the control (2mins). Clearly, pullulan has a great potential to construct dual functional microparticles for inhalation with improved pulmonary delivery efficiency and sustained drug release on-site.

Preparation Strategies of the Anti-Mycobacterial Drug Bedaquiline for Intrapulmonary Routes of Administration

Mycobacterium tuberculosis (M.tb) has infected one-quarter of the world's population and led to the deaths of 1.6 million individuals in 2021 according to estimates from the World Health Organization. The rise in prevalence of multidrug-resistant and extensively drug-resistant M.tb strains coupled with insufficient therapies to treat such strains has motivated the development of more effective treatments and/or delivery modalities. Bedaquiline, a diarylquinoline antimycobacterial agent, effectively targets mycobacterial ATP synthase but may lead to systemic complications upon oral delivery. Targeted delivery of bedaquiline to the lungs represents an alternative strategy to harness the sterilizing benefits of the drug against M.tb while mitigating off-target side effects. Two pulmonary delivery modalities were developed herein, including dry powder inhalation and liquid instillation. Despite bedaquiline's poor water solubility, spray drying was performed in predominantly aqueous conditions (≥80%) to avoid a closed-loop, inert system. Aerosols of spray-dried bedaquiline with L-leucine excipient outperformed spray-dried bedaquiline alone, demonstrating superior fine particle fraction metrics (~89% of the emitted dose below <5 µm), suitable for inhalation therapies. Furthermore, the use of a 2-hydroxypropyl-β-cyclodextrin excipient allowed a molecular dispersion of bedaquiline in an aqueous solution for liquid instillation. Both delivery modalities were successfully administered to Hartley guinea pigs for pharmacokinetic analysis and were well-tolerated by the animals. Intrapulmonary liquid delivery of bedaquiline led to adequate serum absorption and appropriate peak serum concentrations of the drug. The liquid formulation was superior in systemic uptake compared to the powder formulation. The predominant route via which M.tb bacilli enter the body is aerosol droplets that are deposited onto airway surfaces. For this reason, we believe that further studies should focus on inhalation or intrapulmonary therapies that target the site of entry and primary site of infection for M.tb.

Bulk Flow Optimisation of Amorphous Solid Dispersion Excipient Powders through Surface Modification

Particulate amorphous solid dispersions (ASDs) have been recognised for their potential to enhance the performance of various solid dose forms, especially oral bioavailability and macromolecule stability. However, the inherent nature of spray-dried ASDs leads to their surface cohesion/adhesion, including hygroscopicity, which hinders their bulk flow and affects their utility and viability in terms of powder production, processing, and function. This study explores the effectiveness of L-leucine (L-leu) coprocessing in modifying the particle surface of ASD-forming materials. Various contrasting prototype coprocessed ASD excipients from both the food and pharmaceutical industries were examined for their effective coformulation with L-leu. The model/prototype materials included maltodextrin, polyvinylpyrrolidone (PVP K10 and K90), trehalose, gum arabic, and hydroxypropyl methylcellulose (HPMC E5LV and K100M). The spray-drying conditions were set such that the particle size difference was minimised, so that it did not play a substantial role in influencing powder cohesion. Scanning electron microscopy was used to evaluate the morphology of each formulation. A combination of previously reported morphological progression typical of L-leu surface modification and previously unreported physical characteristics was observed. The bulk characteristics of these powders were assessed using a powder rheometer to evaluate their flowability under confined and unconfined stresses, flow rate sensitivities, and compactability. The data showed a general improvement in maltodextrin, PVP K10, trehalose and gum arabic flowability measures as L-leu concentrations increased. In contrast, PVP K90 and HPMC formulations experienced unique challenges that provided insight into the mechanistic behaviour of L-leu. Therefore, this study recommends further investigations into the interplay between L-leu and the physico-chemical properties of coformulated excipients in future amorphous powder design. This also revealed the need to enhance bulk characterisation tools to unpack the multifactorial impact of L-leu surface modification.

Pharmacokinetic considerations for optimizing inhaled spray-dried pyrazinoic acid formulations

Tuberculosis (TB), caused by Mycobacterium tuberculosis ( Mtb ), remains a leading cause of death with 1.6 million deaths worldwide reported in 2021. Oral pyrazinamide (PZA) is an integral part of anti-TB regimens, but its prolonged use has the potential to drive development of PZA resistant Mtb . PZA is converted to the active moiety pyrazinoic acid (POA) by the Mtb pyrazinamidase encoded by pncA , and mutations in pncA are associated with the majority of PZA resistance. Conventional oral and parenteral therapies may result in subtherapeutic exposure in the lung, hence direct pulmonary administration of POA may provide an approach to rescue PZA efficacy for treating pncA- mutant PZA-resistant Mtb . The objectives of the current study were to i) develop novel dry powder POA formulations ii) assess their feasibility for pulmonary delivery using physicochemical characterization, iii) evaluate their pharmacokinetics (PK) in the guinea pig model and iv) develop a mechanism based pharmacokinetic model (MBM) using in vivo PK data to select a formulation providing adequate exposure in epithelial lining fluid (ELF) and lung tissue. We developed three POA formulations for pulmonary delivery and characterized their PK in plasma, ELF, and lung tissue following passive inhalation in guinea pigs. Additionally, the PK of POA following oral, intravenous and intratracheal administration was characterized in guinea pigs. The MBM was used to simultaneously model PK data following administration of POA and its formulations via the different routes. The MBM described POA PK well in plasma, ELF and lung tissue. Physicochemical analyses and MBM predictions suggested that POA maltodextrin was the best among the three formulations and an excellent candidate for further development as it has: (i) the highest ELF-to-plasma exposure ratio (203) and lung tissue-to-plasma exposure ratio (30.4) compared with POA maltodextrin and leucine (75.7/16.2) and POA leucine salt (64.2/19.3); (ii) the highest concentration in ELF ( Cmac ELF : 171 nM) within 15.5 minutes, correlating with a fast transfer into ELF after pulmonary administration ( k PM : 22.6 1/h). The data from the guinea pig allowed scaling, using the MBM to a human dose of POA maltodextrin powder demonstrating the potential feasibility of an inhaled product.

Table of Contents TOC/Abstract Graphic

Bacteriophage endolysin powders for inhaled delivery against pulmonary infections

Endolysins are bacteriophage-encoded enzymatic proteins that have great potential to treat multidrug-resistant bacterial infections. Bacteriophage endolysins Cpl-1 and ClyJ-3 have shown promising antimicrobial activity against Streptococcus pneumoniae, which causes pneumonia in humans. This is the first study to investigate the feasibility of spray-dried endolysins Cpl-1 and ClyJ-3 with excipients to produce inhalable powders. The two endolysins were individually tested with leucine and sugar (lactose or trehalose) for spray drying method followed by characterization of biological and physico-chemical properties. A complete loss of ClyJ-3 bioactivity was observed after atomization of the liquid feed solution（before the drying process）, while Cpl-1 maintained its bioactivity in the spray-dried powders. Cpl-1 formulations containing leucine with lactose or trehalose showed promising physico-chemical properties (particle size, crystallinity, hygroscopicity, etc.) and aerosol performances (fine particle fraction values above 65%). The results indicated that endolysin Cpl-1 can be formulated as spray dried powders suitable for inhaled delivery to the lungs for the potential treatment of pulmonary infections.

Spray freeze dried niclosamide nanocrystals embedded dry powder for high dose pulmonary delivery

Based on the drug repositioning strategy, niclosamide (NCL) has shown potential applications for treating COVID-19. However, the development of new formulations for effective NCL delivery is still challenging. Herein, NCL-embedded dry powder for inhalation (NeDPI) was fabricated by a novel spray freeze drying technology. The addition of Tween-80 together with 1,2-Distearoyl-sn-glycero-3-phosphocholine showed the synergistic effects on improving both the dispersibility of primary NCL nanocrystals suspended in the feed liquid and the spherical structure integrity of the spray freeze dried (SFD) microparticle. The SFD microparticle size, morphology, crystal properties, flowability and aerosol performance were systematically investigated by regulating the feed liquid composition and freezing temperature. The addition of leucine as the aerosol enhancer promoted the microparticle sphericity with greatly improved flowability. The optimal sample (SF_{- 80}D-N₂₀L₂D₂T₁) showed the highest fine particle fraction of ∼47.83%, equivalently over 3.8 mg NCL that could reach the deep lung when inhaling 10 mg dry powders.

On the Physical Stability of Leucine-Containing Spray-Dried Powders for Respiratory Drug Delivery

Carrier-free spray-dried dispersions for pulmonary delivery, for which the demand is growing, frequently require the incorporation of dispersibility-enhancing excipients into the formulations to improve the efficacy of the dosage form. One of the most promising of such excipients, L-leucine, is expected to be approved for inhalation soon and has been studied exhaustively. However, during stability, small fibers protruding from the particles of leucine-containing powders have occasionally been observed. To clarify the origin of these fibers and assess their potential influence on the performance of the powders, three different classes of spray-dried leucine-containing formulation systems were studied over an 8-month accelerated stability program. These systems consisted of a large molecule biologic (bevacizumab) in conjunction with a glass former (trehalose), an amorphous small-molecular mass active (moxidectin), and a crystallizing active (mannitol). It was determined that the appearance of the fibers was due to the presence of small quantities of leucine in higher energy states, either because these were amorphous or present as a less stable crystalline polymorph. It was further shown that the growth of these leucine fibers caused no significant physicochemical instability in the powders. Nor, more importantly, did it decrease their aerosol performance in a dry powder inhaler or reduce the concentration of their active pharmaceutical ingredients.

Development of spray-dried N-acetylcysteine dry powder for inhalation

N-acetylcysteine (NAC) has both antioxidant and immunomodulatory activities and has been used as adjuvant therapy in several viral infections. Recently, NAC attracted attention for its possible role in reducing the affinity of the spike protein receptor binding domain to angiotensin-converting enzyme (ACE2) receptors. Since only NAC solutions are available for inhalation, the purpose of the work was to develop a NAC dry powder for inhalation using mannitol or leucine as excipient. The powder was successfully produced using co-spray-drying with leucine. ATR-FTIR analyses evidenced spectral variations ascribed to the formation of specific interactions between NAC and leucine. This effect on the NAC environment was not evident for NAC-mannitol powders, but mannitol was in a different polymorphic form compared to the supplied material. Both the feedstock concentration and the leucine content have an impact on the powder aerodynamic features. In particular, to maximize the respirable fraction, it is preferable to produce the powder starting from a 0.5 % w/v feedstock solution using 33 to 50 % w/w leucine content. The NAC-leucine powder was stable for ten months maintaining NAC content of 50 % (w/w) and about 200 μg of NAC was able to deposit on a transwell insert, useful for future in vitro studies.

Development of a new indole derivative dry powder for inhalation for the treatment of biofilm-associated lung infections

The aim of this work was to produce an inhalable dry powder formulation of a new anti-biofilm compound (SC38). For this purpose, chitosan was used as a polymeric carrier and l-leucine as a dispersibility enhancer. SC38 was entrapped by spray-drying into previously optimized chitosan microparticles. The final formulation was fully characterized in vitro in terms of particle morphology, particle size and distribution, flowability, aerodynamic properties, anti-biofilm activity and effects on lung cell viability. The SC38-loaded chitosan microparticles exhibited favorable aerodynamic properties with emitted and respirable fractions higher than 80 % and 45 % respectively. The optimized formulation successfully inhibited biofilm formation at microparticle concentrations starting from 20 μg/mL for methicillin-sensitive and 100 μg/mL for methicillin-resistant Staphylococcus aureus and showed a relatively safe profile in lung cells after 72 h exposure. Future in vivo tolerability and efficacy studies are needed to unravel the potential of this novel formulation for the treatment of difficult-to-treat biofilm-mediated lung infections.

Nanoparticle-containing lyophilized dry powder inhaler formulations optimized using central composite design with improved aerodynamic parameters and redispersibility

Objectives: The aim of this study was to improve the aerodynamic behavior and redispersibility of a lyophilized dry powder inhaler (DPI) formulation containing nanoparticles.Methods: Paclitaxel (PTX)-human serum albumin (HSA) nanoparticles were used as a model, and DPIs containing the nanoparticles were produced by lyophilization using different carriers and carrier ratios. A central composite design was employed to optimize the formulation. L-leucine and mannitol were chosen as independent variables, and mass median aerodynamic diameter (MMAD), emitted fraction, fine particle fraction (FPF), nanoparticle size, polydispersity index (PDI), zeta potential were selected as dependent variables.Results: The water content of DPIs was less than 5% for all DPIs. The cytotoxicity of the DPIs, determined using A549 cells, was due to PTX alone. Particle sizes of 204.3 ± 1.65 nm and 94.3-1353.0 nm were obtained before and after lyophilization, respectively. The developed method resulted in a reduction in the MMAD from 8.148 µm to 5.274 µm, an increase in the FPF from 17.63% to 33.60%, and an increase in the emitted fraction from 77.68% to 97.03%. The physico-chemical characteristics of the optimized formulation were also assessed.Conclusions: In conclusion, this study demonstrates that lyophilization can be used to produce nanoparticle-containing DPI formulations with improved redispersibility and aerodynamic properties.