Journal of Aerosol Medicine and Pulmonary Drug Delivery

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

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

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

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

In cystic fibrosis (CF) patients, inhalation of alpha₁-proteinase inhibitor (A₁-PI) can prevent or slow down persistent infections and reduce the massive ongoing inflammation and excessive levels of NE that destroy the airway epithelium, leading to progressive loss of pulmonary function and death. It is essential for an efficient treatment with inhaled A₁-PI that an adequate and reproducible dose is deposited within all regions of the lung. The I-neb AAD System provides two inhalation modes: the Target Inhalation Mode (TIM) and the Tidal Breathing Mode (TBM). Both were compared in this study for their efficiency to deliver A₁-PI to the lungs.

This was a randomized, open label, cross-over study to investigate the lung deposition of A₁-PI in 6 healthy subjects (HS) and 15 CF subjects. The primary endpoint was to evaluate the total lung deposition relative to filling dose of A₁-PI inhalation solution using the I-neb AAD System in TIM and in TBM. The main secondary endpoints were extra-thoracic deposition, exhaled drug fraction, nebulizer residue, C/P ratio, and variance of pixel counts. Additional exploratory endpoints were total treatment time and the inhalation time. Radiolabeling was performed considering GMP using a commercially available sterile labeling kit. Radiolabeling was validated using NGI data acquired by gamma scintillation and UV spectrometry.

The intrapulmonary deposition (mean ± SD) in CF subjects was 47.0% ± 6.6% and 46.7% ± 10.3% in TIM and TBM, respectively, and in healthy subjects, 50.0% ± 6.7% and 54.8% ± 7.0% in TIM and TBM, respectively. TIM resulted in an approximately 40% lower treatment time (HS 6.4 min vs. 10.3 min, CF 5.3 min vs. 10.7 min) and less extra-thoracic deposition compared to TBM, and showed a higher residue of drug in the nebulizer, compared to TBM. In both groups, inhalation of a single dose of 77 mg of A₁-PI was efficient, safe, and well tolerated using TIM and TBM.

The effectiveness of inhaled aerosolized antibiotics is limited by poor ventilation of infected airways. Pulmonary delivery of antibiotics emulsified within liquid perfluorocarbon [antibacterial perfluorocarbon ventilation (APV)] may solve this problem through better airway penetration and improved spatial uniformity. However, little work has been done to explore emulsion formulation and the corresponding effects on drug delivery during APV. This study investigated the effects of emulsion formulation on emulsion stability and the pharmacokinetics of antibiotic delivery via APV.

Gravity-driven phase separation was examined in vitro by measuring emulsion tobramycin concentrations at varying heights within a column of emulsion over 4 hours for varying values of fluorosurfactant concentration (C_fs = 5–48 mg/mL H₂O). Serum and pulmonary tobramycin concentrations in rats were then evaluated following pulmonary tobramycin delivery via aerosol or APV utilizing sufficiently stable emulsions of varying aqueous volume percentage (V_aq = 1%–5%), aqueous tobramycin concentration (C_t = 20–100 mg/mL), and C_fs (15 and 48 mg/mL H₂O).

In vitro assessment showed sufficient spatial and temporal uniformity of tobramycin dispersion within emulsion for C_fs ≥15 mg/mL H₂O, while lower C_fs values showed insufficient emulsification even immediately following preparation. APV with stable emulsion formulations resulted in 5–22 times greater pulmonary tobramycin concentrations at 4 hours post-delivery relative to aerosolized delivery. Concentrations increased with emulsion formulations utilizing increased V_aq (with decreased C_t) and, to a lesser extent, increased C_fs.

The emulsion stability necessary for effective delivery is retained at C_fs values as low as 15 mg/mL H₂O. Additionally, the pulmonary retention of antibiotic delivered via APV is significantly greater than that of aerosolized delivery and can be most effectively increased by increasing V_aq and decreasing C_t. APV has been further proven as an effective means of pulmonary drug delivery with the potential to significantly improve antibiotic therapy for lung disease patients.

Theoretical models suggest that He-O₂ as carrier gas may lead to more homogeneous ventilation and aerosol deposition than air. However, these effects have not been clinically consistent and it is unclear why subjects may or may not respond to the therapy. Here we present 3D-imaging data of aerosol deposition and ventilation distributions from subjects with asthma inhaling He-O₂ as carrier gas. The data are compared with those that we previously obtained from a similar group of subjects inhaling air.

Subjects with mild-to-moderate asthma were bronchoconstricted with methacholine and imaged with PET-CT while inhaling aerosol carried with He-O₂. Mean-normalized-values of lobar specific ventilation sV* and deposition sD* were derived and the factors affecting the distribution of sD* were evaluated along with the effects of breathing frequency (f) and regional expansion (F_VOL).

Lobar distributions of sD* and sV* with He-O₂ were not statistically different from those previously measured with air. However, with He-O₂ there was a larger number of lobes having sV* and sD* closer to unity and, in those subjects with uneven deposition distributions, the correlation of sD* with sV* was on average higher (p < 0.05) in He-O₂ (0.84 ± 0.8) compared with air (0.55 ± 0.28). In contrast with air, where the frequency of breathing during nebulization was associated with the degree of sD*-sV* correlation, with He-O₂ there was no association. Also, the modulation of f on the correlation between F_VOL and sD*/sV* in air, was not observed in He-O₂.

There were no differences in the inter-lobar heterogeneity of sD* or sV* in this group of mild asthmatic subjects breathing He-O₂ compared with patients previously breathing air. Future studies, using these personalized 3D data sets as input to CFD models, are needed to understand if, and for whom, breathing He-O₂ during aerosol inhalation may be beneficial.

Better treatment outcomes in cystic fibrosis (CF) may be expected by changing standard twice daily (BID) tobramycin inhalation with the conventional nebulizer to once daily (OD) inhalation at double the standard BID dose with a controlled-inhalation nebulizer. We aimed to determine the pharmacokinetics and tolerability of inhaled double-dose tobramycin with the controlled-inhalation AKITA^® and conventional PARI-LC^® Plus nebulizer in patients with CF.

Randomized, open label, crossover study. Pharmacokinetics were assessed in 10 adult CF patients following inhalation of tobramycin (Bramitob^®) at double the recommended BID dose with the AKITA (300 mg fill dose) and PARI-LC Plus (600 mg fill dose).

No significant differences were found in pharmacokinetic parameters between the two nebulizers. Median maximum serum levels were 3.44 (2.25–5.49) and 2.84 (0.82–6.63) mg/L for AKITA and PARI-LC Plus, respectively. Trough serum levels were very low for both nebulizers: 0.03 (0.00–0.09) and 0.02 (0.00–0.06) mg/L for AKITA and PARI-LC Plus, respectively. Time to maximum level was comparable: 0.44 (0.08–0.96) and 0.40 (0.08–0.96) hours for AKITA and PARI-LC Plus, respectively. Serum levels were well below the toxic limit. Inhalations were well tolerated and no serious adverse events occurred. Nebulization time was 33% shorter with the AKITA.

OD tobramycin inhalation of the double standard BID dose with a controlled-inhalation and conventional nebulizer resulted in similar pharmacokinetics in the doses given, with serum levels below the toxic limit. Further research demonstrating clinical efficacy and safety of this treatment approach is required.

Dutch trial register number NTR4525.

In pre-clinical animal studies, the uniformity of dosing across subjects and routes of administration is a crucial requirement. In preparation for a study in which aerosolized live-attenuated measles virus vaccine was administered to cynomolgus monkeys (Macaca fascicularis) by inhalation, we assessed the percentage of a nebulized dose inhaled under varying conditions.

Drug delivery varies with breathing parameters. Therefore we determined macaque breathing patterns (tidal volume, breathing frequency, and inspiratory to expiratory (I:E) ratio) across a range of 3.3–6.5 kg body weight, using a pediatric pneumotachometer interfaced either with an endotracheal tube or a facemask. Subsequently, these breathing patterns were reproduced using a breathing simulator attached to a filter to collect the inhaled dose. Albuterol was nebulized using a vibrating mesh nebulizer and the percentage inhaled dose was determined by extraction of drug from the filter and subsequent quantification.

Tidal volumes ranged from 24 to 46 mL, breathing frequencies from 19 to 31 breaths per minute and I:E ratios from 0.7 to 1.6. A small pediatric resuscitation mask was identified as the best fitting interface between animal and pneumotachometer. The average efficiency of inhaled dose delivery was 32.1% (standard deviation 7.5, range 24%–48%), with variation in tidal volumes as the most important determinant.

Studies in non-human primates aimed at comparing aerosol delivery with other routes of administration should take both the inter-subject variation and relatively low efficiency of delivery to these low body weight mammals into account.

Inhalation therapy targeted to the deep alveolated regions holds great promise, specifically in pediatric populations. Yet, inhalation devices and medical protocols are overwhelmingly derived from adult guidelines, with very low therapeutic efficiency in young children. During the first years of life, airway remodeling and changing ventilation patterns are anticipated to alter aerosol deposition with underachieving outcomes in infants. As past research is still overwhelmingly focused on adults or limited to models of upper airways, a fundamental understanding of inhaled therapeutic transport and deposition in the acinar regions is needed to shed light on delivering medication to the developing alveoli.

Using computational fluid dynamics (CFD), we simulated inhalation maneuvers in anatomically-inspired models of developing acinar airways, covering the distinct phases of lung development, from underdeveloped, saccular pulmonary architectures in infants, to structural changes in toddlers, ultimately mimicking space-filling morphologies of a young child, representing scaled-down adult lungs. We model aerosols whose diameters span the range of sizes acknowledged to reach the alveolar regions and examine the coupling between morphological changes, varying ventilation patterns and particle characteristics on deposition outcomes.

Spatial distributions of deposited particles point to noticeable changes in the patterns of aerosol deposition with age, in particular in the youngest age group examined (3 month). Total deposition efficiency, as well as deposition dispersion, vary not only with the phases of lung development but also and critically with aerosol diameter.

Given the various challenges when prescribing inhalation therapy to a young infant, our findings underline some mechanistic aspects to consider when targeting medication to the developing alveoli. Not only does the intricate coupling between acinar morphology and ventilation patterns need to be considered, but the physical properties (i.e., aerodynamic size) of therapeutic aerosols also closely affect the anticipated success rates of the inhaled medication.

Health effects of inhaling aerosol produced by electronic cigarettes (ECs) are still uncertain. This work analyzes ECs as specific inhalation devices, which can be characterized by aerodynamic resistance, size distribution of released droplets, and predicted regional and total lung deposition as a function of inhalation maneuver.

The internal resistance of two types of EC and a conventional cigarette was evaluated by measuring ΔP-Q curves. Particle size distribution in EC-emitted mist was determined by laser diffraction. The measured data were used to calculate lung deposition based on two approaches: multipath particle dosimetry model (MPPD) and Finlay-Martin correlations. Computations were done for the set of ventilation parameters of an EC user, and also for a by-stander.

Tested ECs had higher aerodynamic resistance (1.6–1.9 mbar^0.5 min/L) than tobacco cigarette (0.56 mbar^0.5 min/L), and these values are much above the high-resistant DPIs. The average mass median diameter of droplets emitted from ECs was 410 nm, with the average GSD = 1.6. Predicted total lung deposition of the mainstream aerosol was 15%–45% depending on the breathing scheme. An expected increase of particle size in the exhaled aerosol led to predictions of 15%–30% deposition efficiency during passive vaping.

ECs are characterized by high inhalatory resistance, so they require stronger physical effort to transfer cloud of droplets to the lungs, as compared, for example, to DPIs. A significant amount of aerosol is then exhaled, forming an unintentional source of particles to which by-standers are exposed. From this perspective, ECs are not optimal personal aerosol delivery devices.