A hand-held apparatus for "nose-only" exposure of mice to inhalable microparticles as a dry powder inhalation targeting lung and airway macrophages

QbD driven targeted pulmonary delivery of dexamethasone-loaded chitosan microspheres: Biodistribution and pharmacokinetic study

Inhaling drugs, on the other hand, is limited mainly by the natural mechanisms of the respiratory system, which push drug particles out of the lungs or make them inefficient once they are there. Because of this, many ways have been found to work around the problems with drug transport through the lungs. Researchers have made polymeric microparticles (MP) and nanoparticles as a possible way to get drugs into the lungs. They showed that the drug could be trapped in large amounts and retained in the lungs for a long time, with as little contact as possible with the bloodstream. MP were formulated in this study to get dexamethasone (DMC) into the pulmonary area. The Box-Behnken design optimized microspheres preparation to meet the pulmonary delivery prerequisites. Optimized formulation was figured out based on the desirability approach. The mass median aerodynamic diameter (MMAD) of the optimized formula (O-DMC-MP) was 8.46 ± 1.45 µm, and the fine particle fraction (FPF) was 77.69 ± 1.26%. This showed that it made suitable drug delivery system, which could make it possible for MP to settle deeply in the lung space after being breathed in. With the first burst of drug release, it was seen that drug release could last up to 16 h. Also, there was no clear sign that the optimized formulation was toxic to the alveoli basal epithelial cells in the lungs, as supported by cytotoxic studies in HUVEC, A549, and H1299 cell lines. Most importantly, loading DMC inside MP cuts the amount of drug into the bloodstream compared to plain DMC, as evident from biodistribution studies. Stability tests have shown that the product can stay the same over time at both the storage conditions. Using chitosan DMC-MP can be a better therapeutic formulation to treat acute respiratory distress syndrome (ARDS).

Inhaled Adjunct Therapy with Second-Line Drug Candidates for Dose Reduction in Chemotherapeutic Regimens for Multi-drug-Resistant Tuberculosis

Chemotherapy of multi-drug-resistant tuberculosis (TB) requires prolonged administration of multiple drugs. We investigated whether pulmonary delivery of minute doses of drugs, along with reduced oral doses of the same agents, would affect preclinical efficacy. We prepared dry powder inhalation (DPI) formulations comprising sutezolid (SUT), the second-generation pretomanid analog TBA-354 (TBA), or a fluorinated derivative of TBA-354 (32,625) in a matrix of the biodegradable polymer poly(L-lactide). We established formulation characteristics, doses inhaled by healthy mice, and preclinical efficacy in a mouse model of TB. Oral doses of 100 mg/kg/day or DPI doses of 0.25-0.5 mg/kg/day of drugs SUT, TBA-354, or 32,625 administered over 28 days were sub-optimally effective in reducing lung and spleen burden of Mycobacterium tuberculosis (Mtb) in infected mice. The addition of 0.25-0.5 mg/kg/day of SUT, TBA-354, or 32,625 as DPI to oral doses of 50 mg/kg/day was non-inferior in clearing Mtb from the lungs of infected mice. We concluded that adjunct therapy with inhaled second-line agents has the potential to reduce the efficacious oral dose.

Design Considerations for Intratracheal Delivery Devices to Achieve Proof-of-Concept Dry Powder Biopharmaceutical Delivery in Mice

PURPOSE

Intratracheal delivery and consistent dosing of dry powder vaccines is especially challenging in mice. To address this issue, device design of positive pressure dosators and actuation parameters were assessed for their impacts on powder flowability and in vivo dry powder delivery.

METHODS

A chamber-loading dosator assembled with stainless-steel, polypropylene or polytetrafluoroethylene needle-tips was used to determine optimal actuation parameters. Powder loading methods including tamp-loading, chamber-loading and pipette tip-loading were compared to assess performance of the dosator delivery device in mice.

RESULTS

Available dose was highest (45%) with a stainless-steel tip loaded with an optimal mass and syringe air volume, primarily due to the ability of this configuration to dissipate static charge. However, this tip encouraged more agglomeration along its flow path in the presence of humidity and was too rigid for intubation of mice compared to a more flexible polypropylene tip. Using optimized actuation parameters, the polypropylene pipette tip-loading dosator achieved an acceptable in vivo emitted dose of 50% in mice. After administering two doses of a spray dried adenovirus encapsulated in mannitol-dextran, high bioactivity was observed in excised mouse lung tissue three days post-infection.

CONCLUSIONS

This proof-of-concept study demonstrates for the first time that intratracheal delivery of a thermally stable, viral-vectored dry powder can achieve equivalent bioactivity to the same powder, reconstituted and delivered intratracheally. This work may guide the design and device selection process for murine intratracheal delivery of dry powder vaccines to help progress this promising area of inhalable therapeutics.

Preparation and Evaluation of Low-Dose Calcitriol Dry Powder Inhalation as Host-Directed Adjunct Therapy for Tuberculosis

Background

It is unclear whether Vitamin D is efficacious as a host-directed therapy (HDT) for patients of tuberculosis (TB). We investigated pulmonary delivery of the active metabolite of Vitamin D₃, i.e., 1, 25-dihydroxy vitamin D₃ (calcitriol) in a mouse model of infection with Mycobacterium tuberculosis (Mtb).

Methods

We optimized a spray drying process to prepare a dry powder inhalation (DPI) of calcitriol using a Quality by Design (QbD) approach. We then compared outcomes when Mtb-infected mice were treated with inhaled calcitriol at 5 ng/kg as a stand-alone intervention versus DPI as adjunct to standard oral anti-tuberculosis therapy (ATT).

Results

The DPI with or without concomitant ATT markedly improved the morphology of the lungs and mitigated histopathology in both the lungs and the spleens. The number of nodular lesions on the lung surface decreased from 43.7 ± 3.1 to 22.5 ± 3.9 with the DPI alone and to 9.8 ± 2.5 with DPI + ATT. However, no statistically significant induction of host antimicrobial peptide cathelicidin or reduction in bacterial burden was seen with the DPI alone. DPI + ATT did not significantly reduce the bacterial burden in the lungs compared to ATT alone.

Conclusions

We concluded that HDT using the low dose calcitriol DPI contributed markedly to mitigation of pathology, but higher dose may be required to evoke significant induction of bactericidal host response and bactericidal activity in the lung.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03360-5.

SIRT 1 Activator Loaded Inhaled Antiangiogenic Liposomal Formulation Development for Pulmonary Hypertension

Pulmonary hypertension (PH) is characterized by the rise in mean pulmonary arterial pressure (≥ 20 mmHg at rest) due to the narrowing of the pulmonary arterial networks. Current treatments provide symptomatic treatment and the underlying progress of PH continues leading to higher mortality rates due to non-reversal of the disease. This warrants the need for drug therapies targeting angiogenesis and vascular remodeling mechanisms. Resveratrol, SIRT 1 activator, alters various signaling pathways, inhibits apoptosis, and negatively regulates angiogenesis either by increasing the production of anti-angiogenic factors or inhibiting pro-angiogenic factors. Our work describes the liposomal formulation development, physicochemical characterization, and in vitro aerosolization performance of resveratrol liposomal dry powder formulation. The resveratrol liposomal dry powder formulation reduces the right ventricular systolic pressure measured during right jugular vein catheterization and significantly reverses the PH disease pathological changes as demonstrated by histological observations of pulmonary arterial lumen and ventricular hypertrophy. The developed resveratrol liposomal dry powder formulation alleviates the pulmonary arterial remodeling through its antiangiogenic mechanism and indicates a promising therapeutic strategy for PH treatment.

High dose nanocrystalline solid dispersion powder of voriconazole for inhalation

In the current work, we aimed to deliver high dose of voriconazole (VRC) to lung through dry powder for inhalation (DPIs). Furthermore, the research tested the hypothesis that drug nanocrystals can escape the clearance mechanisms in lung by virtue of their size and rapid dissolution. High dose nanocrystalline solid dispersion (NCSD) based DPI of VRC was prepared using a novel spray drying process. Mannitol (MAN) and soya lecithin (LEC) were used as crystallization inducer and stabilizer, respectively. The powders were characterized for physicochemical and aerodynamic properties. Chemical interactions contributing to generation and stabilization of VRC nanocrystals in the matrix of MAN were established using computational studies. Performance of NCSD (VRC-N) was compared with microcrystalline solid dispersion (VRC-M) in terms of dissolution, uptake in A549 and RAW 264.7 cells. Plasma and lung distribution of VRC-N and VRC-M in Balb/c mice upon insufflation was compared with the intravenous product. In VRC-N, drug nanocrystals of size 645.86 ± 56.90 nm were successfully produced at VRC loading of 45%. MAN created physical barrier to crystal growth by interacting with N- of triazole and F- of pyrimidine ring of VRC. An increase in drug loading to 60% produced VRC crystals of size 4800 ± 200 nm (VRC-M). The optimized powders were crystalline and showed deposition at stage 2 and 3 in NGI. In comparison to VRC-M, more than 80% of VRC-N dissolved rapidly in around 5-10 mins, therefore, showed higher and lower drug uptake into A549 and RAW 264.7 cells, respectively. In contrast to intravenous product, insufflation of VRC-N and VRC-M led to higher drug concentrations in lung in comparison to plasma. VRC-N showed higher lung AUC_0-24 due to escape of macrophage clearance.

Pulmonary Targeting of Levofloxacin Using Microsphere-Based Dry Powder Inhalation

The objective of the current study was to develop poly (lactic-co-glycolic acid) (PLGA) microspheres loaded with the anti-tuberculosis (anti-TB) fluoroquinolone, Levofloxacin (LVX), in the form of dry powder inhalation (DPI). LVX-loaded microspheres were fabricated by solvent evaporation technique. Central Composite Design (CCD) was adopted to optimize the microspheres, with desired particle size, drug loading, and drug entrapment efficiency, for targeting alveolar macrophages via non-invasive pulmonary delivery. Structural characterization studies by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction analysis revealed the absence of any possible chemical interaction between the drug and the polymer used for the preparation of microspheres. In addition, the optimized drug-loaded microspheres exhibited desired average aerodynamic diameter of 2.13 ± 1.24 μm and fine particle fraction of 75.35 ± 1.42%, indicating good aerosolization properties. In vivo data demonstrated that LVX-loaded microspheres had superior lung accumulation, as evident by a two-fold increase in the area under the curve AUC0–24h, as compared with plain LVX. Furthermore, LVX-loaded microspheres prolonged drug residence time in the lung and maintained a relatively high drug concentration for a longer time, which contributed to a reduced leakage in the systemic circulation. In conclusion, inhalable LVX-loaded microspheres might represent a plausible delivery vehicle for targeting pulmonary tuberculosis via enhancing the therapeutic efficacy of LVX while minimizing its systemic off-target side effects.

Performance and drug deposition of kappa-carrageenan microspheres encapsulating ciprofloxacin HCl: Effect of polymer concentration

It has been known that in respiratory disease, antibiotic is selected for respiratory diseases or lung infections and this research focused on ciprofloxacin HCl as a model. The aim was to evaluate the effect of kappa-carrageenan polymer concentrations on characteristics, release, and drug deposition in the lung. Ciprofloxacin HCl-carrageenan microspheres were produced with kappa carrageenan (0.75%, 0.50%, and 0.25%) as polymer and KCl (1.5%) as crosslinker. Physical characteristics were included morphology, size, moisture content, swelling index, mucoadhesivity, drug loading, entrapment efficiency, and yield. Freeze-dried microspheres were inhaled by animal, and drug deposition was observed. Results showed that dried, smooth, and spherical microspheres of size of 1.34 to 1.70 μm and loading of 15.63% to 38.72%. Entrapment efficiency and yield were 25.38%-51.61% and 52.53%-63.19%, respectively. Mucoadhesivity was 0.0059-0.0096 kg force, and release in 24 h was 74.38%-81.02%. Release kinetics demonstrated Higuchi mechanism. Increasing carrageenan concentration affected size, loading, and efficiency but did not influence adhesivity, yield, and release. Higher amount of polymer caused the lower deposit on the lungs. Respirable size of ciprofloxacin HCl-kappa carrageenan microspheres was successfully achieved target site and prolonged residence time in lungs.

Inhalable particles containing isoniazid and rifabutin as adjunct therapy for safe, efficacious and relapse-free cure of experimental animal tuberculosis in one month

We investigated the preclinical efficacy and safety/tolerability of biodegradable polymeric particles containing isoniazid (INH) and rifabutin (RFB) dry powder for inhalation (DPI) as an adjunct to oral first-line therapy. Mice and guinea pigs infected with Mycobacterium tuberculosis H37Rv (Mtb) were treated with ∼80 and ∼300 μg of the DPI, respectively, for 3-4 weeks starting 3, 10, and 30 days post-infection. Adjunct combination therapy eliminated culturable Mtb from the lungs and spleens of all but one of 52 animals that received the DPI. Relapse-free cure was not achieved in one mouse that received DPI + oral, human-equivalent doses (HED) of four drugs used in the Directly Observed Treatment, Short Course (DOTS), starting 30 days post-infection. Oral doses (20 mg/Kg/day, each) of INH + RFB reduced Mtb burden from ∼10⁶ to ∼10³ colony-forming units. Combining half the oral dose with DPI prevented relapse of infection four weeks after stopping the treatment. The DPI was safe in rodents, guinea pigs, and monkeys at 1, 10, and 100 μg/day doses over 90 days. In conclusion, we show the efficacy and safety/tolerability of the DPI as an adjunct to oral chemotherapy in three different animal models of TB.

Transient Transfection of the Respiratory Epithelium with Gamma Interferon for Host-Directed Therapy in Pulmonary Tuberculosis

Nebulized gamma interferon (IFN-γ) protein has been studied for clinical safety and efficacy against pulmonary tuberculosis (TB). The protein is expensive, requires a cold chain, and is difficult to deploy in limited-resource, high-incidence settings. We generated a preclinical proof of concept (PoC) for a dry powder inhalation (DPI) containing DNA constructs to transiently transfect the lung and airway epithelium of mice with murine IFN-γ. Bacterial colony-forming units (CFU) in the lungs of mice infected with Mycobacterium tuberculosis (Mtb) reduced from about 106/g of tissue to ~104 after four doses given once a week. Nodular inflammatory lesions in the lungs reduced significantly in number. Immunohistochemistry of infected lung sections for LC3-1 and LAMP-1 indicated autophagy induction between 18 and 48 h after inhalation. ELISA on bronchoalveolar lavage (BAL) fluid showed differences in kinetics of IFN-γ concentrations in the epithelial lining fluid of healthy versus infected mice. Uninfected mice receiving DNA constructs expressing a fluorescent protein were live-imaged. The fluorescence signals from the intracellular protein peaked at about 36 h after inhalation and declined by 48 h. These results establish preclinical PoC of the efficacy of a DPI and dosing regimen as a host-directed and transient gene therapy of experimental pulmonary TB in mice, justifying preclinical development.

Targeted Pulmonary Delivery of the Green Tea Polyphenol Epigallocatechin Gallate Controls the Growth of Mycobacterium tuberculosis by Enhancing the Autophagy and Suppressing Bacterial Burden

Growing rates of tuberculosis (TB) superbugs are alarming, which has hampered the progress made to-date to control this infectious disease, and new drug candidates are few. Epigallocatechin gallate (EGCG), a major polyphenolic compound from green tea extract, shows powerful efficacy against TB bacteria in in vitro studies. However, the therapeutic efficacy of the molecule is limited due to poor pharmacokinetics and low bioavailability following oral administration. Aiming to improve the treatment outcomes of EGCG therapy, we investigated whether encapsulation and pulmonary delivery of the molecule would allow the direct targeting of the site of infection without compromising the activity. Microencapsulation of EGCG was realized by scalable spray-freeze-drying (SFD) technology, forming free-flowing micrometer-sized microspheres (epigallocatechin-3-gallate-loaded trehalose microspheres, EGCG-t-MS) of trehalose sugar. These porous microspheres exhibited appropriate aerodynamic parameters and high encapsulation efficiencies. In vitro studies demonstrated that EGCG-t-MS exhibited dose- and time-dependent killing of TB bacteria inside mouse macrophages by cellular mechanisms of lysosome acidification and autophagy induction. In a preclinical study on TB-infected Balb/c mice model (4 weeks of infection), we demonstrate that the microencapsulated EGCG, administered 5 days/week for 6 weeks by pulmonary delivery, showed exceptional efficacy compared to oral treatment of free drug. This treatment approach exhibited therapeutic outcomes by resolution of inflammation in the infected lungs and significant reduction (P < 0.05) in bacterial burden (up to ∼2.54 Log₁₀ CFU) compared to untreated control and orally treated mice groups. No pathological granulomas, lesions, and inflammation were observed in the histopathological investigation, compared to untreated controls. The encouraging results of the study may pave the avenues for future use of EGCG in TB therapeutics by targeted pulmonary delivery and lead to its translational success.

An Efficient and Cost-Effective Nose-Only Inhalational Chamber for Rodents: Design, Optimization and Validation

The mainstay treatment of pulmonary disorders lies around the direct drug targeting to the lungs using a nebulizer, metered-dose inhaler, or dry powder inhaler. Only few inhalers are available in the market that could be used for inhalational drug delivery in rodents. However, the available rodent inhalers invariably require high cost and maintenance, which limits their use at laboratory scale. The present work, therefore, was undertaken to develop a simple, reliable, and cost-effective nose-only inhalation chamber with holding capacity of three mice at a time. The nebulized air passes directly and continuously from the central chamber to mouthpiece and maintains an aerosol cloud for rodents to inhale. Laser diffraction analysis indicated volume mean diameter of 4.02 ± 0.30 μm, and the next-generation impactor studies, however, revealed mean mass aerodynamic diameter of 3.40 ± 0.27 μm, respectively. An amount of 2.05 ± 0.20 mg of voriconazole (VRC) was available for inhalation at each delivery port of the inhaler. In vivo studies indicated the deposition of 76.12 ± 19.50 μg of VRC in the mice lungs when nebulized for a period of 20 min. Overall, the developed nose-only inhalation chamber offers a reliable means of generating aerosols and successfully exposing mice to nebulization.

Hybrid Ofloxacin/eugenol co-loaded solid lipid nanoparticles with enhanced and targetable antimicrobial properties

In the global context of an imminent emergence of multidrug-resistant microorganisms, the present work combined the use of nanotechnology and the therapeutic benefits of natural compounds as a strategy to potentiate antimicrobial action of the wide-spectrum antibiotic Ofloxacin (Ofx). Hybrid solid lipid nanoparticles (SLN) were synthesized by incorporation of chitosan (Chi, a cationic biopolymer with antimicrobial activity) and eugenol (Eu, a phenolic compound that interferes with bacterial quorum sensing) into a lipid matrix by hot homogenization/ultrasonication method. The developed SLN/Chi/Eu sustainably released the encapsulated Ofx for 24 h. Characterization by DLS, TEM, DSC, TGA and XRD revealed the presence of positively charged spherical nanoparticles with diameters around 300 nm and Ofx entrapped in amorphous state. The SLN exhibited an enhanced bactericidal activity against Pseudomonas aeruginosa and Staphylococcus aureus. The minimum inhibitory concentration (MIC) for free and nanoencapsulated Ofx formulations was below 1.0 µg/ml. The MIC values decreased by 6.1- to 16.1-fold when Ofx was encapsulated in SLN/Chi/Eu. Fluorescent-labeled nanoparticles had the ability to interact with the bacterial cell membrane. Selective toxicity of SLN/Chi/Eu-Ofx was tested in the range of 0.3-30.0 µg/ml and showed no toxicity up to 3.0 µg/ml Ofx in human cell models (A549 and Wi-38) at 24 h and 48 h exposure. It was proved that the administration of hybrid SLN to mice by dry powder inhalation reached therapeutic Ofx levels in lungs.

Formulation of RNA interference-based drugs for pulmonary delivery: challenges and opportunities

With recent advances in the field of RNAi-based therapeutics, it is possible to make any target gene 'druggable', at least in principle. The present review focuses on aspects critical for pulmonary delivery of formulations of nucleic acid-based drugs. The first part introduces the therapeutic potential of RNAi-based drugs for the treatment of lung diseases. Subsequently, we discuss opportunities for formulation-enabled pulmonary delivery of RNAi drugs in light of key physicochemical properties and physiological barriers. In the following section, an overview is included of methodologies for imparting inhalable characteristics to nucleic acid formulations. Finally, we review one of the bottlenecks in the early preclinical testing of inhalable nucleic acid-based formulations, in other words, devices suitable for pulmonary administration of powder-based formulations in rodents.

Preclinical Development of Inhalable d-Cycloserine and Ethionamide To Overcome Pharmacokinetic Interaction and Enhance Efficacy against Mycobacterium tuberculosis

We compared the pharmacokinetics and efficacy of a combination of d-cycloserine (DCS) and ethionamide (ETO) via oral and inhalation routes in mice. The plasma half-life (t _1/2) of oral ETO at a human-equivalent dose decreased from 4.63 ± 0.61 h to 1.64 ± 0.40 h when DCS was coadministered. The area under the concentration-time curve from 0 h to time t (AUC_{0- t} ) was reduced to one-third. Inhalation overcame the interaction. Inhalation, but not oral doses, reduced the lung CFU/g of Mycobacterium tuberculosis H37Rv from 6 to 3 log₁₀ in 4 weeks, indicating bactericidal activity.

Establishment and characterization of a multi-purpose large animal exposure chamber for investigating health effects

Air pollution poses a significant threat to the environment and human health. Most in vivo health studies conducted regarding air pollutants, including particulate matter (PM) and gas phase pollutants, have been either through traditional medical intranasal treatment or using a tiny chamber, which limit animal activities. In this study, we designed and tested a large, whole-body, multiple animal exposure chamber with uniform dispersion and exposure stability for animal studies. The chamber simultaneously controls particle size distribution and PM mass concentration. Two different methods were used to generate aerosol suspension through either soluble material (Alternaria extract), liquid particle suspension (nanosilica solution), or dry powder (silica powder). We demonstrate that the chamber system provides well controlled and characterized whole animal exposures, where dosage is by inhalation of particulate matter.

Exploring inhalable polymeric dry powders for anti-tuberculosis drug delivery

The growing interest on polymeric delivery systems for pulmonary administration of drugs anticipates a more direct and efficient treatment of diseases such as tuberculosis (TB) that uses the pulmonary route as the natural route of infection. Polymeric microparticles or nano-in-microparticles offer target delivery of drugs to the lungs and the potential to control and sustain drug release within TB infected macrophages improving the efficiency of the anti-TB treatment and reducing side effects. In a dry powder form these inhalable delivery systems have increased stability and prolonged storage time without requiring refrigeration, besides being cost-effective and patient convenient. Thus, this review aims to compile the recent innovations of inhalable polymeric dry powder systems for the delivery of anti-TB drugs exploring the methods of production, aerodynamic characterization and the efficacy of targeted drug delivery systems using in vitro and in vivo models of the disease. Advanced knowledge and promising outcomes of these systems are anticipated to simplify and revolutionize the pulmonary drug delivery and to contribute towards more effective anti-TB treatments.

Respiratory Tract Deposition and Distribution Pattern of Microparticles in Mice Using Different Pulmonary Delivery Techniques

Pulmonary delivery of drugs and vaccines is an established route of administration, with particulate-based carriers becoming an attractive strategy to enhance the benefits of pulmonary therapeutic delivery. Despite the increasing number of publications using the pulmonary route of delivery, the lack of effective and uniform administration techniques in preclinical models generally results in poor translational success. In this study, we used the IVIS Spectrum small-animal in vivo imaging system to compare the respiratory tract deposition and distribution pattern of a microsphere suspension (5 µm) in mice after 1, 4, and 24 h when delivered by oropharyngeal aspiration, the Microsprayer® Aerosolizer, and the BioLite Intubation System, three-widely reported preclinical inhalation techniques. We saw no significant differences in microsphere deposition in whole body images and excised lungs (at 1, 4, and 24 h); however, the three-dimensional (3D) images showed more localized deposition in the lungs with the MicroSprayer® and BioLite delivery techniques. Further, oropharyngeal aspiration (at 1 h) showed microsphere deposition in the oral cavity, in contrast to the MicroSprayer® and BioLite systems. The studies shown here will allow researchers to choose the appropriate pulmonary delivery method in animal models based on their study requirements.

Preparation and optimization of a dry powder for inhalation of second-line anti-tuberculosis drugs

A spray drying process was standardized to prepare an inhalable powder comprising d-cycloserine and ethionamide, two "second line" drugs employed for treating multi-drug resistant (MDR) tuberculosis (TB). The aim of the process development effort was to maximize product yield. Contour plots were generated using a small central composite design (CCD) with face centered (α = 1) to maximize the process yield as the response criterion. The design space was experimentally validated. Powder was prepared and characterized for drug content (HPLC), geometric size (laser scattering), surface morphology (scanning electron microscopy) aerosol behaviour (cascade impaction) and powder flow properties. The optimized process yielded a powder with a median mass aerodynamic diameter (MMAD) of 1.76 µ ± 3.1 geometric standard deviation (GSD). Mass balance indicated that the major proportion of the particles produced by spray drying are lost to the outlet filter. The process represents a best-case compromise of spray-drying conditions to minimize loss during droplet drying, collection and process air discharge.

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

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

Hybrid inhalable microparticles for dual controlled release of levofloxacin and DNase: physicochemical characterization and in vivo targeted delivery to the lungs

Current medical treatments against recurrent pulmonary infections caused by Pseudomonas aeruginosa, such as cystic fibrosis (CF) disorder, involve the administration of inhalable antibiotics.

Pharmacokinetics of Ethionamide Delivered in Spray-Dried Microparticles to the Lungs of Guinea Pigs

The use of ethionamide (ETH) in treating multidrug-resistant tuberculosis is limited by severe side effects. ETH disposition after pulmonary administration in spray-dried particles might minimize systemic exposure and side effects. To explore this hypothesis, spray-dried ETH particles were optimized for performance in a dry powder aerosol generator and exposure chamber. ETH particles were administered by the intravenous (IV), oral, or pulmonary routes to guinea pigs. ETH appearance in plasma, bronchoalveolar lavage, and lung tissues was measured and subjected to noncompartmental pharmacokinetic analysis. Dry powder aerosol generator dispersion of 20% ETH particles gave the highest dose at the exposure chamber ports and fine particle fraction of 72.3%. Pulmonary ETH was absorbed more rapidly and to a greater extent than orally administered drug. At T_max, ETH concentrations were significantly higher in plasma than lungs from IV dosing, whereas insufflation lung concentrations were 5-fold higher than in plasma. AUC_(0-t) (area under the curve) and apparent total body clearance (CL) were similar after IV administration and insufflation. AUC_(0-t) after oral administration was 6- to 7-fold smaller and CL was 6-fold faster. Notably, ETH bioavailability after pulmonary administration was significantly higher (85%) than after oral administration (17%). These results suggest that pulmonary ETH delivery would potentially enhance efficacy for tuberculosis treatment given the high lung concentrations and bioavailability.

Inhalable Particles for "Pincer Therapeutics" Targeting Nitazoxanide as Bactericidal and Host-Directed Agent to Macrophages in a Mouse Model of Tuberculosis

Nitazoxanide (NTZ) has moderate mycobactericidal activity and is also an inducer of autophagy in mammalian cells. High-payload (40-50% w/w) inhalable particles containing NTZ alone or in combination with antituberculosis (TB) agents isoniazid (INH) and rifabutin (RFB) were prepared with high incorporation efficiency of 92%. In vitro drug release was corrected for drug degradation during the course of study and revealed first-order controlled release. Particles were efficiently taken up in vitro by macrophages and maintained intracellular drug concentrations at one order of magnitude higher than NTZ in solution for 6 h. Dose-dependent killing of Mtb and restoration of lung and spleen architecture were observed in experimentally infected mice treated with inhalations containing NTZ. Adjunct NTZ with INH and RFB cleared culturable bacteria from the lung and spleen and markedly healed tissue architecture. NTZ can be used in combination with INH-RFB to kill the pathogen and heal the host.

Targeted pulmonary delivery of inducers of host macrophage autophagy as a potential host-directed chemotherapy of tuberculosis

One of the promising host-directed chemotherapeutic interventions in tuberculosis (TB) is based on inducing autophagy as an immune effector. Here we consider the strengths and weaknesses of potential autophagy-based pharmacological intervention. Using the existing drugs that induce autophagy is an option, but it has limitations given the broad role of autophagy in most cells, tissues, and organs. Thus, it may be desirable that the agent being used to modulate autophagy is applied in a targeted manner, e.g. delivered to affected tissues, with infected macrophages being an obvious choice. This review addresses the advantages and disadvantages of delivering drugs to induce autophagy in M. tuberculosis-infected macrophages. One option, already being tested in models, is to design particles for inhalation delivery to lung macrophages. The choice of drugs, drug release kinetics and intracellular residence times, non-target cell exposure and feasibility of use by patients is discussed. We term here this (still experimental) approach, of compartment-targeting, autophagy-based, host-directed therapy as "Track-II antituberculosis chemotherapy."

Preparation and Preclinical Evaluation of Inhalable Particles Containing Rapamycin and Anti-Tuberculosis Agents for Induction of Autophagy

PURPOSE

Mycobacterium tuberculosis (Mtb) inhibits host defense mechanisms, including autophagy. We investigated particles containing rapamycin (RAP) alone or in combination with isoniazid (INH) and rifabutin (RFB) for: targeting lung macrophages on inhalation; inducing autophagy; and killing macrophage-resident Mtb and/or augmenting anti-tuberculosis (TB) drugs.

METHODS

PLGA and drugs were spray-dried. Pharmacokinetics, partial biodistribution (LC-MS/MS) and efficacy (colony forming units, qPCR, acid fast staining, histopathology) in mice following dry powder inhalation were evaluated.

RESULTS

Aerodynamic diameters of formulations were 0.7-4.7 μm. Inhaled particles reached deep lungs and were phagocytosed by alveolar macrophages, yielding AUC0-48 of 102 compared to 0.1 μg/ml × h obtained with equivalent intravenous dose. RAP particles induced more autophagy in Mtb-infected macrophages than solutions. Inhaled particles containing RAP alone in daily, alternate-day and weekly dosing regimens reduced bacterial burden in lungs and spleens, inducing autophagy and phagosome-lysosome fusion. Inhalation of particles containing RAP with INH and RFB cleared the lungs and spleens of culturable bacteria.

CONCLUSIONS

Targeting a potent autophagy-inducing agent to airway and lung macrophages alone is feasible, but not sufficient to eliminate Mtb. Combination of macrophage-targeted inhaled RAP with classical anti-TB drugs contributes to restoring tissue architecture and killing Mtb.

A stable live bacterial vaccine

Formulating vaccines into a dry form enhances its thermal stability. This is critical to prevent administering damaged and ineffective vaccines, and to reduce its final cost. A number of vaccines in the market as well as those being evaluated in the clinical setting are in a dry solid state; yet none of these vaccines have achieved long-term stability at high temperatures. We used spray-drying to formulate a recombinant live attenuated Listeria monocytogenes (Lm; expressing Francisella tularensis immune protective antigen pathogenicity island protein IglC) bacterial vaccine into a thermostable dry powder using various sugars and an amino acid. Lm powder vaccine showed minimal loss in viability when stored for more than a year at ambient room temperature (∼23°C) or for 180days at 40°C. High temperature viability was achieved by maintaining an inert atmosphere in the storage container and removing oxygen free radicals that damage bacterial membranes. Further, in vitro antigenicity was confirmed by infecting a dendritic cell line with cultures derived from spray dried Lm and detection of an intracellularly expressed protective antigen. A combination of stabilizing excipients, a cost effective one-step drying process, and appropriate storage conditions could provide a viable option for producing, storing and transporting heat-sensitive vaccines, especially in regions of the world that require them the most.

The in vitro and in vivo investigation of a novel small chamber dry powder inhalation delivery system for preclinical dosing to rats

PURPOSE

This research describes a novel "minitower" dry powder delivery system for nose-only delivery of dry powder aerosols to spontaneously breathing rats.

METHODS

The minitower system forces pressurized air through pre-filled capsules to deliver aerosolized drug to four nose ports; three of which house spontaneously breathing rats, with the fourth used as a control. Within each port are vent filters which capture drug that was not inhaled for further quantitation. These vent filters along with a novel control system referred to as the "artificial rat lung", allow for the theoretical amount of drug delivered and subsequently inhaled by each rat to be calculated.

RESULTS

In vitro and in vivo studies have demonstrated this system's ability to deliver aerosolized drug to rats. The in vitro study showed that ∼30% of the starting dose reached the 4 ports and was available for inhalation. During in-vivo studies, rats inhaled ∼34% of the delivered dose. Of the estimated inhaled dose, 12-18% was detectable in the various tissue samples, with over 30% of the recovered dose found in the rat's lungs.

CONCLUSION

Results show that this system is capable of reproducibly delivering drug to the lungs of spontaneously breathing rats. Advantages over current delivery methods include being amenable to the administration of multiple doses and using less (milligram) amount of starting material. In addition, this technique avoids anesthesia which is typically required for instillation or insufflation, and thus has the potential as an efficient and noninvasive aerosol delivery method for preclinical drug development.

Pharmacokinetic and pharmacodynamic implications in inhalable antimicrobial therapy

Inhaled antimicrobials provide a promising alternative to the systemically delivered drugs for the treatment of acute and chronic lung infections. The delivery of antimicrobials via inhalation route decreases the systemic exposure while increasing the local concentration in the lungs, enabling the use of antimicrobials with severe systemic side effects. The inhalation route of administration has several challenges in pharmacokinetic (PK) and pharmacodynamic (PD) assessments. This review discusses various issues that need to be considered during study, data analysis, and interpretation of PK and PD of inhaled antimicrobials. Advancements overcoming the challenges are also discussed.

Inhalable microparticles of nitric oxide donors induce phagosome maturation and kill Mycobacterium tuberculosis

Nitric oxide (NO) kills Mycobacterium tuberculosis (Mtb) in vitro, but gaseous NO is difficult to administer to patients. We evaluated the consequences of intracellular delivery of NO using inhalable microparticles (MP) containing NO donors. MP containing 10% w/w of NO donors alone, or in addition to 25% each of isoniazid (INH) and rifabutin (RFB) in a polylactide-co-glycolide (PLGA) matrix were prepared by spray drying. THP-1-derived macrophages infected with Mtb H37Rv were exposed to MP or soluble NO donors. Phagosome-lysosome fusion (PLF) and bacterial killing were monitored. Colony forming units (cfu) in lungs and spleen of mice infected with a low-dose aerosol and administered inhalations of MP were enumerated. Bacterial DNA in these tissues was estimated by real-time PCR. In vitro studies indicated a bacteriostatic effect of NO donors despite significant enhancement of PLF. Daily inhalation of MP containing 10% diethylenetriamine nitric oxide adduct (DETA/NO) alone reduced log10 cfu in the lungs from 6.1 to 4.4 at the highest dose in four weeks, but did not significantly affect cfu in the spleen. Inhalations of MP containing DETA/NO in combination with INH and RFB significantly (P < 10(-5), ANOVA) reduced cfu in lungs and spleens by 4 log. Gross morphology and histology of the lungs and spleen indicated that inhaled particles were well-tolerated. Inhalable MP containing NO donors need further investigation as an adjunct to standard anti-tuberculosis chemotherapy.

Inhaled microparticles containing clofazimine are efficacious in treatment of experimental tuberculosis in mice

Inhalable clofazimine-containing dry powder microparticles (CFM-DPI) and native clofazimine (CFM) were evaluated for activity against Mycobacterium tuberculosis in human monocyte-derived macrophage cultures and in mice infected with a low-dose aerosol. Both formulations resulted in 99% killing at 2.5 μg/ml in vitro. In mice, 480 μg and 720 μg CFM-DPI inhaled twice per week over 4 weeks reduced numbers of CFU in the lung by as much as log(10) 2.6; 500 μg oral CFM achieved a log(10) 0.7 reduction.

Inhalable microparticles containing nitric oxide donors: saying NO to intracellular Mycobacterium tuberculosis

Although nitric oxide (NO) is a bactericidal component of the macrophage's innate response to intracellular infections such as tuberculosis (TB), prolonged inhalation of NO gas has little benefit in chemotherapy of TB. The impact of controlled release of NO through intracellular delivery of NO donors to macrophages infected in vitro with Mycobacterium tuberculosis (Mtb) was investigated. Inhalable microparticles (MP) were prepared by spray-drying. Isosorbide mononitrate (ISMN), sodium nitroprusside (SNP), and diethylenetriamine nitric oxide adduct (DETA/NO) were incorporated in poly(lactic-co-glycolic acid) (PLGA) with encapsulation efficiencies of >90% to obtain MP yields of ∼70%. The mass median aerodynamic diameter (MMAD) of the MP was 2.2-2.4 μm within geometric standard deviations (GSD) of ≤0.1 μm. MP were phagocytosed by THP-1 derived macrophages in culture and significantly (P < 0.05) sustained NO secretion into culture supernatant from 6 to 72 h in comparison to equivalent amounts of drugs in solution. Significantly (P < 0.05) higher dose-dependent killing of intracellular Mtb by MP compared to equivalent amounts of drugs in solution was observed on estimation of colony forming units (CFU) surviving 24 h after exposure to drugs or MP. The cytotoxicity of MP toward macrophages was lower than that of dissolved drugs. It was concluded that inhalable MP can target NO donors to the macrophage, control NO release in the macrophage cytosol, and reduce Mtb CFU by up to 3-log in 24 h, at doses that are much lower than those required for cardiovascular effects.

Partial biodistribution and pharmacokinetics of isoniazid and rifabutin following pulmonary delivery of inhalable microparticles to rhesus macaques

Dry powder inhalations (DPI) of microparticles containing isoniazid (INH) and rifabutin (RFB) are under preclinical development for use in pulmonary tuberculosis. Microparticles containing 0.25, 2.5, or 25 mg of each drug were administered daily for 90 days to rhesus macaques (n = 4/group). Single inhalations or intravenous (i.v.) doses were administered to separate groups. Drugs in serum, alveolar macrophages, and organ homogenates were assayed by high-performance liquid chromatography (HPLC). The RFB/INH in the lungs (101.10 ± 12.90/101.07 ± 8.09 μg/g of tissue) was twice that of the liver concentrations (60.22 ± 04.97/52.08 ± 4.62 μg/g) and four times that of the kidneys (22.89 ± 05.22/30.25 ± 3.71 μg/g). Pharmacokinetic parameters indicated the operation of flip-flop kinetics. Thus, the elimination half-life (t(1/2)) of RFB and INH was calculated as 8.01 ± 0.5 and 2.49 ± 0.23 h, respectively, upon intravenous (iv) administration, and as 13.8 ± 0.8 and 10.43 ± 0.77 h following a single inhalation; or 13.36 ± 3.51 and 10.13 ± 3.01 at a presumed steady state (day 60 of dosing). Targeted and sustained drug delivery to nonhuman primate lungs and alveolar macrophages was demonstrated. Flip-flop serum pharmacokinetics was observed, and nonlinearity in some pharmacokinetic parameters at logarithmic dose increments was indicated. The results suggest that human patients would benefit through improvement in biodistribution following DPI.

Development of an inhalation chamber and a dry powder inhaler device for administration of pulmonary medication in animal model

CONTEXT

Pulmonary route of administration is becoming more popular for drug delivery in pulmonary tract and lungs for local and systemic actions.

OBJECTIVE

A dry powder inhaler (DPI) for delivery of dry powder and a nose-only inhalation chamber for small animals that can be used with nebuliser/DPI were designed.

MATERIALS AND METHODS

The inhalation chamber was made with a polypropylene-rectangular box and centrifuge tubes. DPI was made of a polypropylene tube. Micronized voriconazole and voriconazole solution were used for DPI and nebulizer, respectively, for both in vitro and in vivo studies.

RESULTS

In vitro drug deposition from nebulizer was found to be 11-26% w/w and that from DPI was 42 to 57% w/w depending on experimental set up. Uniform deposition across all the inhalation ports was observed irrespective of the methods. Respirable fraction (RF) varied from 34 to 73% in case of nebulizer and from 47 to 54% in case of DPI. In vivo deposition of voriconazole in lungs was found to be 80-130 µg/g of lung tissue in case of DPI and 40-68 µg/g of lung tissue in case of using nebulizer.

DISCUSSION

DPI designed was efficient in fluidizing powder bed and dispensing dry powder for inhalation. The inhalation chamber designed was efficient in uniformly distributing drug in various inhalation ports of the chamber.

CONCLUSIONS

The DPI and inhalation chamber designed can be successfully used for inhalation study with multiple animals especially mice.

Intracellular time course, pharmacokinetics, and biodistribution of isoniazid and rifabutin following pulmonary delivery of inhalable microparticles to mice

Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalable microparticles of these drugs to phorbol-differentiated THP-1 cells and the pharmacokinetics and biodistribution of these drugs upon inhalation of microparticles or intravenous administration of free drugs to mice were investigated. In cultured cells, both microparticles and dissolved drugs established peak concentrations of isoniazid ( approximately 1.4 and 1.1 microg/10(6) cells) and rifabutin ( approximately 2 microg/ml and approximately 1.4 microg/10(6) cells) within 10 min. Microparticles maintained the intracellular concentration of isoniazid for 24 h and rifabutin for 96 h, whereas dissolved drugs did not. The following pharmacokinetic parameters were calculated using WinNonlin from samples obtained after inhalation using an in-house apparatus (figures in parentheses refer to parameters obtained after intravenous administration of an equivalent amount, i.e., 100 microg of either drug, to parallel groups): isoniazid, serum half-life (t(1/2)) = 18.63 +/- 5.89 h (3.91 +/- 1.06 h), maximum concentration in serum (C(max)) = 2.37 +/- 0.23 microg x ml(-1) (3.24 +/- 0.57 microg x ml(-1)), area under the concentration-time curve from 0 to 24 h (AUC(0-24)) = 55.34 +/- 13.72 microg/ml(-1) h(-1) (16.64 +/- 1.80 microg/ml(-1) h(-1)), and clearance (CL) = 63.90 +/- 13.32 ml x h(-1) (4.43 +/- 1.85 ml x h(-1)); rifabutin, t(1/2) = 119.49 +/- 29.62 h (20.18 +/- 4.02 h), C(max) = 1.59 +/- 0.01 microg x ml(-1) (3.47 +/- 0.33 microg x ml(-1)), AUC(0-96) = 109.35 +/- 14.78 microg/ml(-1) h(-1) (90.82 +/- 7.46 microg/ml(-1) h(-1)), and CL = 11.68 +/- 7.00 ml x h(-1) (1.03 +/- 0.11 ml.h(-1)). Drug targeting to the lungs in general and alveolar macrophages in particular was observed. It was concluded that inhaled microparticles can reduce dose frequency and improve the pharmacologic index of the drug combination.