Trileucine improves aerosol performance and stability of spray-dried powders for inhalation

Design of dry powder inhalers to improve patient outcomes: it's not just about the device

INTRODUCTION

Up to 50% of asthma/COPD patients make critical errors in dose preparation and dose inhalation with current marketed DPIs which negatively impact clinical outcomes. Others fail to adhere to their chronic treatment regimen.

AREAS COVERED

For this review, we describe how a human-factors approach to design of a dry powder inhaler can be used to improve usability, proficiency, and functionality of DPIs, while effectively mitigating critical errors associated with DPIs. The review highlights the critical importance of utilizing improved formulations with monomodal aerodynamic particle size distributions to reduce variability associated with oropharyngeal filtering of particles, flow rate dependence, and co-formulation effects.

EXPERT OPINION

Much of the variability in dose delivery with DPIs is associated with limitations of the bimodal APSDs inherent in current lactose blend formulations. Evidence supports that improved lung targeting and dose consistency can be achieved with drug-device combination products comprising spray-dried powders. Unfortunately, no data exists to assess whether these advances observed in in vitro and in vivo dose delivery studies will translate into improved clinical outcomes. Given the significant percentage of patients that receive suboptimal drug delivery with current DPIs it would behoove the industry to assess the efficacy of new approaches.

Hierarchy of the Components in Spray-Dried, Protein-Excipient Particles Using DNP-Enhanced NMR Spectroscopy

Protein-based drugs are becoming increasingly important, but there are challenges associated with their formulation (for example, formulating stable inhalable aerosols while maintaining the proper long-term stability of the protein). Determining the morphology of multicomponent, protein-based drug formulations is particularly challenging. Here, we use dynamic nuclear polarization (DNP) solid-state NMR spectroscopy to determine the hierarchy of components within spray-dried particles containing protein, trehalose, leucine, and trileucine. DNP NMR was applied to these formulations to assess the localization of the components within the particles. We found a consistent scheme, where trehalose and the protein are co-located within the same phase in the core of the particles and leucine and trileucine are distributed in separate phases at the surface of the particles. The description of the hierarchy of the organic components determined by DNP NMR enables the rationalization of the performance of the formulation.

Mechanism of Insoluble Aggregate Formation in a Reconstituted Solution of Spray-Dried Protein Powder

BACKGROUND

Spray-drying is considered a promising alternative drying method to lyophilization (freeze-drying) for therapeutic proteins. Particle counts in reconstituted solutions of dried solid dosage forms of biologic drug products are closely monitored to ensure product quality. We found that high levels of particles formed after reconstitution of protein powders that had been spray-dried under suboptimal conditions.

METHODS

Visible and subvisible particles were evaluated. Soluble proteins in solution before spray-drying and in the reconstituted solution of spray-dried powder were analyzed for their monomer content levels and melting temperatures. Insoluble particles were collected and analyzed by Fourier transform infrared microscopy (FTIR), and further analyzed with hydrogen-deuterium exchange (HDX).

RESULTS

Particles observed after reconstitution were shown not to be undissolved excipients. FTIR confirmed their identity as proteinaceous in nature. These particles were therefore considered to be insoluble protein aggregates, and HDX was applied to investigate the mechanism underlying aggregate formation. Heavy-chain complementarity-determining region 1 (CDR-1) in the aggregates showed significant protection by HDX, suggesting CDR-1 was critical for aggregate formation. In contrast, various regions became more conformationally dynamic globally, suggesting the aggregates have lost protein structural integrity and partially unfolded after spray-drying.

DISCUSSION

The spray-drying process could have disrupted the higher-order structure of proteins and exposed the hydrophobic residues in CDR-1 of the heavy chain, contributing to the formation of aggregate through hydrophobic interactions upon reconstitution of spray-dried powder. These results can contribute to efforts to design spray-dry resilient protein constructs and improve the robustness of the spray-drying process.

Cyclosporine A-loaded chitosan extra-fine particles for deep pulmonary drug delivery: In vitro and in vivo evaluation

In this study, the extra-fine dry powder inhalers (DPIs) with chitosan (CS) as carrier were successfully prepared by ionic gel method combined with spray drying technique for deep pulmonary drug delivery of Cyclosporine A (CsA), using sodium hyaluronate (SHA) and sodium polyglutamate (SPGA) as polyanions. The CsA-loaded DPIs of CS-SHA-CsA and CS-SPGA-CsA were spherical particles with wrinkles on the surface, which were more conducive to improving the aerosol properties. The aerodynamic evaluation of CS-SHA-CsA and CS-SPGA-CsA showed that the fine particle fraction (FPF) reached up to 79.22 ± 2.12% and 81.55 ± 0.43%, while the emitted fraction (EF) reached 77.15 ± 1.46% and 78.29 ± 2.10%. In addition, the mass median aerodynamic diameter (MMAD) was calculated as 1.58 ± 0.04 μm and 1.94 ± 0.02 μm for CS-SHA-CsA and CS-SPGA-CsA, indicating that they were all extra-fine particles (d < 2 μm). These in vitro aerodynamic results showed that CS-SHA-CsA and CS-SPGA-CsA could reach the smaller airways, further improving therapeutic efficiency. The cell viability on A549 cell line results showed that CS-SHA-CsA and CS-SPGA-CsA were safe to deliver CsA to lungs. The in vivo pharmacokinetics consequence proved that inhalation administration of CS-SHA-CsA and CS-SPGA-CsA could significantly improve the bioavailability of CsA in vivo compared with oral administration of Neoral®, effectively reducing the risk of a series of adverse effects caused by systemic overexposure. In addition, the safety and compatibility of DPIs using SHA, SPGA, and CS as carriers for pulmonary drug delivery was verified by in vivo repeated dose inhalation toxicity. From these findings, the extra-fine DPIs with CS as carrier could be a viable delivery option for the deep pulmonary drug delivery of CsA relative to orally administered drug.

Preclinical Investigation of a Lipoglycopeptide Dry Powder Inhalation Therapy for the Treatment of Pulmonary MRSA Infection

The increased prevalence of pulmonary methicillin-resistant Staphylococcus aureus (MRSA) infection in patients living with cystic fibrosis (CF) is concerning due to a correlation with reduced life expectancy and lack of available treatment options. RV94 is a next generation lipoglycopeptide designed for pulmonary delivery that preclinically demonstrated high potency against MRSA in planktonic and protected colonies and improved pulmonary clearance relative to same class molecules. Here, RV94 was formulated into a dry powder for inhalation (DPI) to investigate the localized treatment of pulmonary MRSA presented in a potentially more convenient dosage form. RV94 DPI was generated using a spray-drying process with 12.5 wt% trileucine and demonstrated aerosol characteristics (2.0 μm MMAD and 73% FPF) predictive of efficient pulmonary deposition. In vivo PK from a single dose of RV94 DPI delivered by inhalation to rats yielded lung levels (127 μg/g) much greater than the MRSA minimum inhibitory concentration (0.063 μg/mL), low systemic levels (0.1 μg/mL), and a lung t1/2 equal to 3.5 days. In a rat acute pulmonary MRSA model, a single dose of RV94 DPI delivered by inhalation either up to seven days prior to or 24 h after infection resulted in a statistically significant reduction in lung MRSA titer.

Performance Testing of a Homemade Aerosol Generator for Pulmonary Administration of Dry Powder Formulations to Mice

A challenge in the development of dry powder formulations for inhalation is the poor reproducibility of their administration to small laboratory animals. The currently used devices for the pulmonary administration of dry powder formulations to small rodents often function sub-optimally as they use the same puff of air for both powder dispersion and aerosol delivery. As a result, either the air volume and flow rate are too low for complete powder deagglomeration or they are too high for effective aerosol delivery to the lungs of the animal. Therefore, novel and better devices are desired. We here present an aerosol generator designed to administer a pre-generated aerosol to the lungs of mice. By mapping the complex relationship between the airflow rate, delivery time and emitted dose, we were able to control the amount of powder being delivered from the aerosol generator. The emitted aerosol had a size range favorable for lung deposition and could be measured reproducibly. Nevertheless, in vivo fluorescent imaging still revealed considerable differences between the mice in terms of the dose deposited and the distribution of powder over the lungs, suggesting that a certain biological variation in lung deposition is inevitable.

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.

Pulmonary delivery of spray-dried Nisin ZP antimicrobial peptide for non-small cell lung cancer (NSCLC) treatment

Nisin ZP is an antimicrobial peptide (AMP) produced by the bacterium Lactococcus lactis, and we have previously demonstrated anticancer activity in NSCLC (A549) cells. In this study, we formulated a nisin ZP dry powder (NZSD) using a spray dryer to facilitate inhaled delivery for the treatment of NSCLC. Nisin ZP was spray-dried with mannitol, l-leucine, and trehalose in a ratio of 75:15:10 using Büchi mini spray-dryer B-290 in different drug loadings (10, 20, and 30% w/w). NZSD powder revealed a good powder yield of >55% w/w with ≤3 % w/w moisture content and high nisin ZP drug loading for all the peptide ratios. The NZSD powder particles were irregularly shaped with corrugated morphology. The presence of an endothermic peak in DSC thermograms and attenuated crystalline peaks in PXRD diffractograms confirmed the semi-crystalline powder nature of NZSD. The anticancer activity of nisin ZP was maintained after fabricating it into NZSD powder and showed a similar inhibitory concentration to free nisin ZP. Stability studies indicated that NZSD powders were stable for three months at 4 and 25 ℃ with more than 90% drug content and semi-crystalline nature, as confirmed by DSC and PXRD. Aerosolization studies performed using NGI indicated an aerodynamic diameter (MMAD) within the desired range (1-5 µm) and a high fine particle fraction (FPF > 75%) for all peptide ratios, suggesting powder deposition in the lung's respiratory airways. In conclusion, a dry powder of nisin ZP was formulated using a spray dryer with enhanced storage stability and suitable for inhaled delivery.

Preparation of Free-Flowing Spray-Dried Amorphous Composites Using Neusilin®

A highly porous additive, Neusilin^®, with high adsorption capability is investigated to improve bulk properties, hence processability of spray-dried amorphous solid dispersions (ASDs). Griseofulvin (GF) is applied as a model BCS class 2 drug in ASDs. Two grades of Neusilin^®, US2 (coarser) and UFL2 (finer), were used as additives to produce spray-dried amorphous composite (AC) powders, and their performance was compared with the resulting ASDs without added Neusilin^®. The resulting AC powders that included Neusilin^® had greatly enhanced flowability (flow function coefficient (FFC) > 10) comparable to larger particles (100 μm) yet had finer particle size (< 50 μm), hence retaining the advantage of fast dissolution rate of finer sizes. Dissolution results demonstrated that achieved GF supersaturation for AC powders with Neusilin^® was as high as 3 times that of crystalline GF concentration and was achieved within 30 min. In addition, 80% of drug was released within 4 min. The flowability improvement for AC powders with Neusilin^® was more significant as compared to spray-dried ASDs without Neusilin^®. Thus, the role of Neusilin^® in flowability improvement was evident, considering that spray-dried AC with Neusilin^® UFL2 has higher FFC than ASDs having a similar size. Lastly, the AC powders retained a fully amorphous state of GF after 3-month ambient storage. The overall results conveyed that the improved flowability and dissolution rate could outweigh the loss of drug loading resulted by addition of Neusilin^®.

Engineering the right formulation for enhanced drug delivery

Dry powder inhalers (DPIs) can be used with a wide range of drugs such as small molecules and biologics and offer several advantages for inhaled therapy. Early DPI products were intended to treat asthma and lung chronic inflammatory disease by administering low-dose, high-potency drugs blended with lactose carrier particles. The use of lactose blends is still the most common approach to aid powder flowability and dose metering in DPI products. However, this conventional approach may not meet the high demand for formulation physical stability, aerosolisation performance, and bioavailability. To overcome these issues, innovative techniques coupled with modification of the traditional methods have been explored to engineer particles for enhanced drug delivery. Different particle engineering techniques have been utilised depending on the types of the active pharmaceutical ingredient (e.g., small molecules, peptides, proteins, cells) and the inhaled dose. This review discusses the challenges of formulating DPI formulations of low-dose and high-dose small molecule drugs, and biologics, followed by recent and emerging particle engineering strategies utilised in developing the right inhalable powder formulations for enhanced drug delivery.

Advancements in the Design and Development of Dry Powder Inhalers and Potential Implications for Generic Development

Dry powder inhalers (DPIs) are drug-device combination products where the complexity of the formulation, its interaction with the device, and input from users play important roles in the drug delivery. As the landscape of DPI products advances with new powder formulations and novel device designs, understanding how these advancements impact performance can aid in developing generics that are therapeutically equivalent to the reference listed drug (RLD) products. This review details the current understanding of the formulation and device related principles driving DPI performance, past and present research efforts to characterize these performance factors, and the implications that advances in formulation and device design may present for evaluating bioequivalence (BE) for generic development.

Inhalable Microparticle Platform Based on a Novel Shell-Forming Lipid Excipient and its Feasibility for Respirable Delivery of Biologics

Administration of biologics such as proteins, vaccines, and phages via the respiratory route is becoming increasingly popular. Inhalable powder formulations for the successful delivery of biologics must first ensure both powder dispersibility and physicochemical stability. A lipid-based inhalable microparticle platform combining the stability advantages offered by dry powder formulations and high dispersibility afforded by a rugose morphology was spray dried and tested. A new simplified spray drying method requiring no organic solvents or complicated feedstock preparation processes was introduced for the manufacture of the microparticles. Trehalose was selected to form the amorphous particle core, because of its well-known ability to stabilize biologics, and also because of its ability to serve as a surrogate for small molecule actives. Phospholipid distearoyl phosphatidylcholine (DSPC), the lipid component in this formulation, was used as a shell former to improve powder dispersibility. Effectiveness of the lipid excipient in modifying trehalose particle morphology and enhancing powder dispersibility was evaluated at different lipid mass fractions (5%, 10%, 25%, 50%) and compared with that of several previously published shell-forming excipients at their effective mass fractions, i.e., 5% trileucine, 20% leucine, and 40% pullulan. A strong dependence of particle morphology on the lipid mass fraction was observed. Particles transitioned from typical smooth spherical trehalose particles without lipid to highly rugose microparticles at higher lipid mass fractions (> 5%). In vitro aerosol performance testing demonstrated a significant improvement of powder dispersibility even at lipid mass fractions as low as 5%. Powder formulations with excellent aerosol performance comparable to those modified with leucine and trileucine were achieved at higher lipid mass fractions (> 25%). A model biologic-containing formulation with 35% myoglobin, 35% glass stabilizer (trehalose), and 30% lipid shell former was shown to produce highly rugose particle structure as designed and excellent aerosol performance for efficient pulmonary delivery. A short-term stability at 40 °C proved that this protein-containing formulation had good thermal stability as designed. The results demonstrated great potential for the new lipid microparticle as a platform for the delivery of both small-molecule APIs and large-molecule biologics to the lung.

An expert opinion on respiratory delivery of high dose powders for lung infections

INTRODUCTION

High dose powder inhalation is evolving as an important approach to to treat lung infections. It is important to its identify applications, consider the factors affecting high dose powder delivery, and assess the effect of high dose drugs in patients.

AREA COVERED

Both current and pipeline high dose inhalers and their applications have been summarized. Challenges and opportunities to high dose delivery have been highlighted after reviewing formulation techniques in the context of factors affecting aerosolization, devices, and patient factors.

EXPERT OPINION

High dose inhaled delivery of antimicrobials is an innovative way to increase treatment efficacy of respiratory infections, tackle drug resistance, and the scarcity of new antimicrobials. The high dose inhaled technology also has potential for systemic action; however, innovations in formulation strategies and devices are required to realize its full potential. Advances in formulation strategies include the use of excipients or the engineering of particles to decrease the cohesive property of microparticles and their packing density. Similarly, selection of a synergistic drug instead of an excipient can be considered to increase aerosolization and stability. Device development focused on improving dispersion and loading capacity is also important, and modification of existing devices for high dose delivery can also be considered.

Bioanalytical Methods and Strategic Perspectives Addressing the Rising Complexity of Novel Bioconjugates and Delivery Routes for Biotherapeutics

In recent years, an increase in the discovery and development of biotherapeutics employing new modalities, such as bioconjugates or novel routes of delivery, has created bioanalytical challenges. The inherent complexity of conjugated molecular structures means that quantification of the bioconjugate and its multiple components is critical for preclinical/clinical studies to inform drug discovery and development. Moreover, bioconjugates involve additional multifactorial complexity because of the potential for in vivo catabolism and biotransformation, which may require thorough investigations in multiple biological matrices. Furthermore, excipients that enhance absorption are frequently evaluated and employed for the development of oral and inhaled biotherapeutics. Risk-benefit assessments are required for novel or existing excipients that utilize dosages above previously approved levels. Bioanalytical methods that can measure both excipients and potential drug metabolites in biological matrices are highly relevant to these emerging bioanalysis challenges. We discuss the bioanalytical strategies for analyzing bioconjugates such as antibody-drug conjugates and antibody-oligonucleotide conjugates and review recent advances in bioanalytical methods for the quantification and characterization of novel bioconjugates. We also discuss bioanalytical considerations for both biotherapeutics and excipients through novel administration routes and review analyses in various biological matrices, from the extensively studied serum or plasma to tissue biopsy in the context of preclinical and clinical studies from both technical and regulatory perspectives.

Spray freeze drying to solidify Nanosuspension of Cefixime into inhalable microparticles

PURPOSE

Spray-freeze drying (SFD) incorporating diverse carbohydrates and leucine was employed to obtain dried nanosuspension of cefixime with improved dissolution profile, good dispersibility, and excellent inhalation performance.

METHODS

Nanoprecipitation was utilized to prepare nanoparticles (NPs). Nanosuspensions of cefixime were solidified via SFD to access inhalable microparticles. The aerosolization efficiencies were evaluated through twin stage impinger (TSI). Laser light scattering and scanning electron microscopy (SEM) provided assistance to determine the particle size/size distribution and morphology, respectively. Amorphous/ crystalline states of materials were examined via differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Release profiles of candidate preparations were evaluated.

RESULTS

The fine particle fraction (FPF) ranged from 18.96 ± 0.76 to 79.28 ± 0.45%. The highest value resulted from trehalose with NP/carrier ratio of 1:1 and leucine 20%. The particle size varied from 5.24 ± 0.97 to 10.17 ± 1.01 μm. The most and the least size distribution were achieved in mannitol and trehalose containing formulations, respectively. The majority of samples demonstrated ideally spherical morphology with diverse degrees of porosity and without needle-shaped structure. Percentages of release in F₇ and F₈ were 89.33 ± 0.88% and 93.54 ± 1.02%, respectively, via first 10 min.

CONCLUSION

SFD of nanosuspensions can be established as a platform for the pulmonary delivery of poorly water-soluble molecules of cefixime. Trehalose and raffinose with a lower ratio of NP to the carrier and higher level of leucine could be introduced as favorable formulations for further respiratory delivery of cefixime.

Advancements in Particle Engineering for Inhalation Delivery of Small Molecules and Biotherapeutics

Dry powder inhalation formulations have become increasingly popular for local and systemic delivery of small molecules and biotherapeutics. Powder formulations provide distinct advantages over liquid formulations such as elimination of cold chain due to room temperature stability, improved portability, and the potential for increasing patient adherence. To become a viable product, it is essential to develop formulations that are stable (physically, chemically and/or biologically) and inhalable over the shelf-life. Physical particulate properties such as particle size, morphology and density, as well as chemical properties can significantly impact aerosol performance of the powder. This review will cover these critical attributes that can be engineered to enhance the dispersibility of inhalation powder formulations. Challenges in particle engineering for biotherapeutics will be assessed, followed by formulation strategies for overcoming the hurdles. Finally, the review will discuss recent examples of successful dry powder biotherapeutic formulations for inhalation delivery that have been clinically assessed.

Innovative Drying Technologies for Biopharmaceuticals

In the past two decades, biopharmaceuticals have been a breakthrough in improving the quality of lives of patients with various cancers, autoimmune, genetic disorders etc. With the growing demand of biopharmaceuticals, the need for reducing manufacturing costs is essential without compromising on the safety, quality, and efficacy of products. Batch Freeze-drying is the primary commercial means of manufacturing solid biopharmaceuticals. However, Freeze-drying is an economically unfriendly means of production with long production cycles, high energy consumption and heavy capital investment, resulting in high overall costs. This review compiles some potential, innovative drying technologies that have not gained popularity for manufacturing parenteral biopharmaceuticals. Some of these technologies such as Spin-freeze-drying, Spray-drying, Lynfinity® Technology etc. offer a paradigm shift towards continuous manufacturing, whereas PRINT® Technology and Microglassification^TM allow controlled dry particle characteristics. Also, some of these drying technologies can be easily scaled-up with reduced requirement for different validation processes. The inclusion of Process Analytical Technology (PAT) and offline characterization techniques in tandem can provide additional information on the Critical Process Parameters (CPPs) and Critical Quality Attributes (CQAs) during biopharmaceutical processing. These processing technologies can be envisaged to increase the manufacturing capacity for biopharmaceutical products at reduced costs.

Targeting of Inhaled Therapeutics to the Small Airways: Nanoleucine Carrier Formulations

Current dry powder formulations for inhalation deposit a large fraction of their emitted dose in the upper respiratory tract where they contribute to off-target adverse effects and variability in lung delivery. The purpose of the current study is to design a new formulation concept that more effectively targets inhaled dry powders to the large and small airways. The formulations are based on adhesive mixtures of drug nanoparticles and nanoleucine carrier particles prepared by spray drying of a co-suspension of leucine and drug particles from a nonsolvent. The physicochemical and aerosol properties of the resulting formulations are presented. The formulations achieve 93% lung delivery in the Alberta Idealized Throat model that is independent of inspiratory flow rate and relative humidity. Largely eliminating URT deposition with a particle size larger than solution pMDIs is expected to improve delivery to the large and small airways, while minimizing alveolar deposition and particle exhalation.

Optimizing Spray-Dried Porous Particles for High Dose Delivery with a Portable Dry Powder Inhaler

This manuscript critically reviews the design and delivery of spray-dried particles for the achievement of high total lung doses (TLD) with a portable dry powder inhaler. We introduce a new metric termed the product density, which is simply the TLD of a drug divided by the volume of the receptacle it is contained within. The product density is given by the product of three terms: the packing density (the mass of powder divided by the volume of the receptacle), the drug loading (the mass of drug divided by the mass of powder), and the aerosol performance (the TLD divided by the mass of drug). This manuscript discusses strategies for maximizing each of these terms. Spray drying at low drying rates with small amounts of a shell-forming excipient (low Peclet number) leads to the formation of higher density particles with high packing densities. This enables ultrahigh TLD (>100 mg of drug) to be achieved from a single receptacle. The emptying of powder from capsules is directly proportional to the mass of powder in the receptacle, requiring an inhaled volume of about 1 L for fill masses between 40 and 50 mg and up to 3.2 L for a fill mass of 150 mg.

Trileucine as a dispersibility enhancer of spray-dried inhalable microparticles

The formation of trileucine-containing spray-dried microparticles intended for pulmonary delivery was studied in depth. A single-particle method was employed to study the shell formation characteristics of trileucine in the presence of trehalose as a glass former, and an empirical correlation was proposed to predict the instance of shell formation. A droplet chain instrument was used to produce and collect monodisperse particles to examine morphology and calculate particle density for different levels of trileucine. It was observed that the addition of only 0.5 mg/mL (10% w/w) trileucine to a trehalose system could lower dried particle densities by approximately 1 g/cm³. In addition, a laboratory-scale spray dryer was used to produce batches of trileucine/trehalose powders in the respirable range. Raman spectroscopy demonstrated that both components were completely amorphous. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry were used to study the particle morphologies and surface compositions. For all cases with trileucine, highly rugose particles with trileucine coverages of more than 60% by mass were observed with trileucine feed fractions of as little as 2% w/w. Moreover, it was seen that at lower trileucine content, smaller and larger particles of a polydisperse powder had slightly different surface compositions. The surface activity of trileucine was also modeled via a modified form of the diffusion equation inside an evaporating droplet that took into account initial surface adsorption and eventual surface desorption due to droplet shrinkage. Finally, using the Flory-Huggins theory, it was estimated that at room temperature, liquid-liquid phase separation would start when the trileucine reached an aqueous concentration of about 18 mg/mL. Besides the surface activity of trileucine, this low concentration was assumed to explain the substantial effect of trileucine on the morphology of spray-dried particles due to early phase separation. The methodology proposed in this study can be used in the rational design of trileucine-containing microparticles.

Evaluation of the stability of a spray-dried tuberculosis vaccine candidate designed for dry powder respiratory delivery

Particle engineering via spray drying was used to develop a dry powder presentation of an adjuvanted tuberculosis vaccine candidate. This presentation utilizing a trileucine-trehalose excipient system was designed to be both thermostable and suitable for respiratory delivery. The stability of the spray-dried vaccine powder was assessed over one year at various storage temperatures (-20, 5, 25, 40, 50 °C) in terms of powder stability, adjuvant stability, and antigen stability. A formulation without trileucine was included as a control. The results showed that the interior particle structure and exterior particle morphology of the powder was maintained for one year at 40 °C, while the control case exhibited a small extent of particle fusing under the same storage conditions. Moisture content was maintained, and powder solid state remained amorphous for all storage temperatures. Aerosol performance was assessed with a commercial dry powder inhaler in combination with a human mouth-throat model. The emitted dose and lung dose were maintained for all samples after one year at temperatures up to 40 °C. Nanoemulsion size and oil content of the adjuvant system were maintained after one year at temperatures up to 40 °C, and the agonist content was maintained after one year at temperatures up to 25 °C. The antigen was completely degraded in the control formulation at seven months of storage at 40 °C; by contrast, 45% of the antigen was still present in the trehalose-trileucine formulation after one year of storage at 50 °C. Comparatively, the antigen was completely degraded in a liquid sample of the vaccine candidate after only one month of storage at 37 °C. The spray-dried trehalose-trileucine vaccine powder clearly maintained its inhalable properties after one year's storage at high temperatures and improved overall thermostability of the vaccine.

Leucine enhances the dispersibility of trehalose-containing spray-dried powders on exposure to a high-humidity environment

This study investigates the ability of various shell-forming excipients to preserve the dispersibility of dry powder dosage forms, e.g., nasally administered vaccines, upon exposure to a high-humidity environment. Trehalose combinations using leucine, pullulan, or trileucine were selected as the candidate excipient systems, and the powder dispersibility of these systems was compared with that of pure trehalose particles. Scaled-up monodisperse spray drying was used to produce sufficient quantities of uniform-sized particles for powder dispersibility analysis. Particle size, crystallinity, and morphology of the powders before and after exposure to moisture were characterized by an aerodynamic particle sizer, Raman spectroscopy, and scanning electron microscopy, respectively. Three two-component particle systems composed of trehalose/trileucine (97/3 w/w), trehalose/pullulan (70/30 w/w), and trehalose/leucine (70/30 w/w) were first formulated and their dispersibility, characterized as the emitted dose from dry powder inhalers, was then compared with that of trehalose particles. The formulation containing 30% leucine maintained the highest emitted dose (90.3 ± 10%) at a 60 L/min flow rate after 60 min exposure to 90% RH and 25 °C, showing its superior protection against exposure to humidity compared with the other systems. Further investigations under more challenging conditions at a 15 L/min flow rate on the trehalose/leucine system with various compositions (70/30, 80/20, 90/10 w/w) showed that a higher leucine concentration generally provided better protection against moisture and maintained higher powder dispersibility, probably due to higher surface coverage of crystalline leucine and a thicker leucine shell around the particle. The study concludes that leucine may be considered an appropriate shell-forming excipient in the development of dry powder formulations in order to protect the dosage forms against humidity during administration.

Dry powder pharmaceutical biologics for inhalation therapy

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

Novel formulations and drug delivery systems to administer biological solids

Recent advances in formulation sciences have expanded the previously limited design space for biological modalities, including peptide, protein, and vaccine products. At the same time, the discovery and application of new modalities, such as cellular therapies and gene therapies, have presented formidable challenges to formulation scientists. We explore these challenges and highlight the opportunities to overcome them through the development of novel formulations and drug delivery systems as biological solids. We review the current progress in both industry and academic laboratories, and we provide expert perspectives in those settings. Formulation scientists have made a tremendous effort to accommodate the needs of these novel delivery routes. These include stability-preserving formulations and dehydration processes as well as dosing regimes and dosage forms that improve patient compliance.

Development and Characterization of Excipient Enhanced Growth (EEG) Surfactant Powder Formulations for Treating Neonatal Respiratory Distress Syndrome

This study aimed to develop and characterize a spray-dried powder aerosol formulation of a commercially available surfactant formulation, Survanta® intratracheal suspension, using the excipient enhanced growth (EEG) approach. Survanta EEG powders were prepared by spray drying of the feed dispersions containing Survanta® (beractant) intratracheal suspension, hygroscopic excipients (mannitol and sodium chloride), and a dispersion enhancer (l-leucine or trileucine) in 5 or 20% v/v ethanol in water using the Buchi Nano Spray Dryer B-90 HP. Powders were characterized for primary particle size, morphology, phospholipid content, moisture content, thermal properties, moisture sorption, and surface activity. The aerosol performance of the powders was assessed using a novel low-volume dry powder inhaler (LV-DPI) device operated with 3-mL volume of dispersion air. At both ethanol concentrations, in comparison to trileucine, l-leucine significantly reduced the primary particle size and span and increased the fraction of submicrometer particles of the Survanta EEG powders. The l-leucine-containing Survanta EEG powders exhibited good aerosolization performance with ≥ 88% of the mass emitted (% nominal) after 3 actuations from the modified LV-DPI device. In addition, l-leucine-containing powders had a low moisture content (< 3% w/w) with transition temperatures close to the commercial surfactant formulation and retained their surface tension reducing activity after formulation processing. A Survanta EEG powder containing l-leucine was developed which showed efficient aerosol delivery from the modified LV-DPI device using a low dispersion air volume.

A quantitative approach to predicting lung deposition profiles of pharmaceutical powder aerosols

Dry powder inhalers (DPI) are widely used systems for pulmonary delivery of therapeutics. The inhalation performance of DPIs is influenced by formulation features, inhaler device and inhalation pattern. The current review presents the affecting factors with great focus on powder characteristics which include particle size, shape, surface, density, hygroscopicity and crystallinity. The properties of a formulation are greatly influenced by a number of physicochemical factors of drug and added excipients. Since available particle engineering techniques result in particles with a set of modifications, it is difficult to distinguish the effect of an individual feature on powder deposition behavior. This necessitates developing a predictive model capable of describing all influential factors on dry powder inhaler delivery. Therefore, in the current study, a model was constructed to correlate the inhaler device properties, inhalation flow rate, particle characteristics and drug/excipient physicochemical properties with the resultant fine particle fraction. The r² value of established correlation was 0.74 indicating 86% variability in FPF values is explained by the model with the mean absolute errors of 0.22 for the predicted values. The authors believe that this model is capable of predicting the lung deposition pattern of a formulation with an acceptable precision when the type of inhaler device, inhalation flow rate, physicochemical behavior of active and inactive ingredients and the particle characteristics of DPI formulations are considered.

Development of a formulation platform for a spray-dried, inhalable tuberculosis vaccine candidate

Protection against primarily respiratory infectious diseases, such as tuberculosis (TB), can likely be enhanced through mucosal immunization induced by direct delivery of vaccines to the nose or lungs. A thermostable inhalable dry powder vaccine offers further advantages, such as independence from the cold chain. In this study, we investigate the formulation for a stable, inhalable dry powder version of ID93 + GLA-SE, an adjuvanted subunit TB vaccine candidate, containing recombinant fusion protein ID93 and glucopyranosyl lipid A (GLA) in a squalene emulsion (SE) as an adjuvant system, via spray drying. The addition of leucine (20% w/w), pullulan (10%, 20% w/w), and trileucine (3%, 6% w/w) as dispersibility enhancers was investigated with trehalose as a stabilizing agent. Particle morphology and solid state, nanoemulsion droplet size, squalene and GLA content, ID93 presence, and aerosol performance were assessed for each formulation. The results showed that the addition of leucine improved aerosol performance, but increased aggregation of the emulsion droplets was demonstrated on reconstitution. Addition of pullulan preserved emulsion droplet size; however, the antigen could not be detected after reconstitution. The trehalose-trileucine excipient formulations successfully stabilized the adjuvant system, with evidence indicating retention of the antigen, in an inhalable dry powder format suitable for lung delivery.

On the particle formation of leucine in spray drying of inhalable microparticles

The particle formation of L-leucine, a dispersibility-enhancing amino acid used in the spray drying of inhalable pharmaceutical aerosols, was extensively studied using three experimental methods, and the results were interpreted with the aid of theory. A comparative-kinetics electrodynamic balance was used to study the shell formation behavior in single evaporating microdroplets containing leucine and trehalose. Different concentration thresholds of solidification and shell formation were determined for trehalose and leucine, which were then used in the particle formation model to predict the properties of spray-dried particles. Furthermore, a droplet chain instrument was used to study the particle morphologies and particle densities that were not accessible in the single particle experiments. Lab-scale spray drying was also used to produce powders typical for actual pharmaceutical applications. Raman spectroscopy confirmed that a glass former, such as trehalose, can inhibit the crystallization of leucine. The surface compositions of these spray-dried powders were analyzed via time-of-flight secondary ion mass spectrometry. The leucine surface coverage in a polydisperse powder was determined to be a function of the particle size or the initial droplet diameter of each respective particle. This observation confirms the important role of leucine crystallization kinetics in its shell-forming capabilities. A critical supersaturation ratio of 3.5 was also calculated for leucine, at which it is assumed to instantaneously nucleate out of solution. This ratio was used as the threshold for the initiation of crystallization. Crystallinity predictions for the leucine-trehalose particles based on this supersaturation ratio were in good agreement with the solid-state characterizations obtained by Raman spectroscopy. This study improves the fundamental understanding of the particle formation process of leucine-containing formulations, which can apply to other crystallizing systems and potentially facilitate the rational design of such formulations with reduced experimental effort.

Unraveling Particle Formation: From Single Droplet Drying to Spray Drying and Electrospraying

Spray drying and electrospraying are well-established drying processes that already have proven their value in the pharmaceutical field. However, there is currently still a lack of knowledge on the fundamentals of the particle formation process, thereby hampering fast and cost-effective particle engineering. To get a better understanding of how functional particles are formed with respect to process and formulation parameters, it is indispensable to offer a comprehensive overview of critical aspects of the droplet drying and particle formation process. This review therefore closely relates single droplet drying to pharmaceutical applications. Although excellent reviews exist of the different aspects, there is, to the best of our knowledge, no single review that describes all steps that one should consider when trying to engineer a certain type of particle morphology. The findings presented in this article have strengthened the predictive value of single droplet drying for pharmaceutical drying applications like spray drying and electrospraying. Continuous follow-up of the particle formation process in single droplet drying experiments hence allows optimization of manufacturing processes and particle engineering approaches and acceleration of process development.

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

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

Physical stability of dry powder inhaler formulations

Introduction: Dry powder inhalers (DPIs) are popular for pulmonary drug delivery. Various techniques have been employed to produce inhalation drug particles and improve the delivery efficiency of DPI formulations. Physical stability of these DPI formulations is critical to ensure the delivery of a reproducible dose to the airways over the shelf-life.Areas covered: This review focuses on the impact of solid-state stability on aerosolization performance of DPI drug particles manufactured by powder production approaches and particle-engineering techniques. It also highlights the different analytical tools that can be used to characterize the physical instability originating from production and storage.Expert opinion: A majority of the DPI literature focuses on the effects of physico-chemical properties such as size, morphology, and density on aerosolization. While little has been reported on the physical stability, particularly the stability of engineered drug particles for use in DPIs. Literature data have shown that different particle-engineering methods and storage conditions may cause physical instability of dry powders for inhalation and can significantly change the aerosol performance. A systematic examination of physical instability mechanisms in DPI formulations is necessary during formulation development in order to select the optimum formulation with satisfactory stability. In addition, the use of appropriate characterization tools is critical to detect and understand physical instability during the development of DPI formulations.

Dispersibility and Storage Stability Optimization of High Dose Isoniazid Dry Powder Inhalation Formulations with L-Leucine or Trileucine

Tuberculosis is the leading cause of death from a single infectious pathogen worldwide. Lately, the targeted delivery of antibiotics to the lungs via inhalation has received increasing interest. In a previous article, we reported on the development of a spray-dried dry powder isoniazid formulation containing an L-leucine coating. It dispersed well but had poor physical stability. In this study, we aimed to improve the stability by improving the leucine coating. To this end, we optimized the spray-drying conditions, the excipient content, and the excipient itself. Using L-leucine, the tested excipient contents (up to 5%) did not result in a stable powder. Contrary to L-leucine, the stability attained with trileucine was satisfactory. Even when exposed to 75% relative humidity, the formulation was stable for at least three months. The optimal formulation contained 3% trileucine w/w. This formulation resulted in a maximum fine particle dose of 58.00 ± 2.56 mg when a nominal dose of 80 mg was dispersed from the Cyclops^® dry powder inhaler. The improved moisture protection and dispersibility obtained with trileucine are explained by its amorphous nature and a higher surface enrichment during drying. Dispersion efficiency of the device decreases at higher nominal doses.

Trileucine and Pullulan Improve Anti-Campylobacter Bacteriophage Stability in Engineered Spray-Dried Microparticles

Spray drying biologics into a powder can increase thermal stability and shelf-life relative to liquid formulations, potentially eliminating the need for cold chain infrastructure for distribution in developing countries. In this study, process modelling, microparticle engineering, and a supplemented phase diagram were used to design physically stable fully amorphous spray-dried powder capable of stabilizing biological material. A greater proportion of anti-Campylobacter bacteriophage CP30A remained biologically active after spray drying using excipient formulations containing trehalose and a high glass transition temperature amorphous shell former, either trileucine or pullulan, as compared to the commonly used crystalline shell former, leucine, or a low glass transition temperature amorphous shell former, pluronic F-68. Particle formation models suggest that the stabilization was achieved by protecting the bacteriophages against the main inactivating stress, desiccation, at the surface. The most promising formulation contained a combination of trileucine and trehalose for which the combined effects of feedstock preparation, spray drying, and 1-month dry room temperature storage resulted in a titer reduction of only 0.6 ± 0.1 log₁₀(PFU mL^-1). The proposed high glass transition temperature amorphous formulation platform may be advantageous for stabilizing biologics in other spray drying applications in the biomedical engineering industry.

Amino acids as stabilizers for spray-dried simvastatin powder for inhalation

BACKGROUND

The use of amino acids as excipients is a promising approach to improve the physical stability and powder dispersibility of spray-dried powders for inhalation.

OBJECTIVES

The aim of this study was to investigate the stabilizing effect of different amino acids on spray-dried amorphous powders for inhalation using simvastatin (SV) as a model compound.

METHODS

Two hydrophobic amino acids (leucine, LEU and tryptophan, TRP), and one hydrophilic amino acid (lysine, LYS) were spray dried from 1% (w/v) solutions with SV at a molar ratio of 1:1 into dry powders for inhalation. Scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterize the morphology, solid form and potential intermolecular interactions of the spray-dried powders. X-ray photoelectron spectroscopy (XPS) was used to analyse the chemical composition of the surface of the particles. The physical stability of the dry powders was examined upon storage in controlled conditions. A Next generation impactor (NGI) was applied to assess the in vitro aerosol performance of the powders.

RESULTS

XRPD and DSC results confirmed that the spray-dried SV-LEU was composed of crystalline LEU and amorphous SV, the spray-dried SV-LYS was co-amorphous, and the spray-dried SV-TRP was an amorphous system with two phases. XPS analyses revealed that the surface of the spray-dried SV-LEU particles were LEU rich, indicating surface-enrichment of LEU in these particles. In contrast, an almost even distribution of TRP and SV at the surface of spray-dried SV-TRP was observed. FTIR results indicated no intermolecular interaction between SV and the amino acids used in the present study. The three spray-dried samples were physically stable after eight months storage in a desiccator (12% RH, ca. 22 °C). Nevertheless, spray-dried SV-LEU exhibited the best storage stability as compared to the other two spray-dried samples when the samples were stored at 60% RH, 25 °C. Both, the spray-dried SV-LEU and SV-TRP exhibited higher fine particle fractions than the spray-dried SV-LYS.

CONCLUSION

Both the spray-dried SV-LEU and SV-TRP exhibited better aerosol performance and storage stability compared to the spray-dried SV-LYS. Compared to TRP, LEU exhibited better protection of spray-dried amorphous SV from re-crystallization, which could be attributed to the formation of a LEU crystalline shell covering SV upon the spray drying process.

Fumaryl diketopiperazine based effervescent microparticles to escape macrophage phagocytosis for enhanced treatment of pneumonia via pulmonary delivery

The treatment of pulmonary infections with antibiotics administered via pulmonary delivery provides for higher local therapeutic efficacy rather than through systemic administration. Pneumonia is globally considered a major cause of death due to a lack of proper medication. The treatment of pneumonia with inhalable antibiotics (such as azithromycin (AZM)) can provide a maximum pulmonary therapeutic effect without significant systemic side effects. Compared to non-effervescent microparticles, effervescent microparticles can provide an active driving force to release loaded antibiotics for subsequent distribution deep into the lung by virtue of its smaller size. In this study, N-fumaroylated diketopiperazine (FDKP) was used as a carrier to prepare effervescent inhalable microparticles loaded with AZM (AZM@FDKP-E-MPs). This effervescent dry powder was characterized for both in vitro and in vivo deposition in the lung and the results obtained showed significant improvement in lung deposition and anti-bacterial efficiency, suggesting a strong potential application for pneumonia treatment.

Respiratory Administration of Infliximab Dry Powder for Local Suppression of Inflammation

The airways are verified as a relevant route to improve antibody therapeutic index with superior lung concentration but limited passage into systemic blood stream. The current research aimed to process spray-dried (SD) powder of Infliximab to assess the feasibility of respiratory delivery of antibody for local suppression of lung-secreted tumor necrosis factor α (TNFα). Molecular and structural stability of powders were determined through size exclusion chromatography (SEC-HPLC) and Fourier transform infrared (FTIR) spectroscopy. Particle properties were characterized by laser light scattering, twin stage impinger (TSI), and scanning electron microscopy (SEM). In vitro biological activity was quantified applying L-929 cell line. Ovalbumin (OVA)-challenged balb/c mice were employed to evaluate the anti-TNFα activity of antibody formulation as in vivo experimental model. SD sample consisting of 36 mg trehalose, 12 mg cysteine, and 0.05% of Tween 20 was selected with minimum aggregation/fragmentation rate constants of 0.07 and 0.05 (1/month) based on 1 and 2 months of storage at 40°C and relative humidity of 75%. Fine particle fraction (FPF) value of this formulation was 67.75% with desired particle size and surface morphology for respiratory delivery. EC₅₀ was 8.176 and 6.733 ng/ml for SD Infliximab and Remicade®, respectively. SD antibody reduced TNFα (26.56 pg/ml) secretion in mouse lung tissue, more than 2 orders of magnitudes comparing positive control group (TNFα, 68.34 pg/ml). The success of antibody inhalation mainly depended on the spray drying condition, formulation components, and stability of antibody within aerosolization. Inhaled Infliximab could be a potential drug for local inhibition of lung inflammation.

Particle Surface Roughness Improves Colloidal Stability of Pressurized Pharmaceutical Suspensions

PURPOSE

The effects of particle size and particle surface roughness on the colloidal stability of pressurized pharmaceutical suspensions were investigated using monodisperse spray-dried particles.

METHODS

The colloidal stability of multiple suspensions in the propellant HFA227ea was characterized using a shadowgraphic imaging technique and quantitatively compared using an instability index. Model suspensions of monodisperse spray-dried trehalose particles of narrow distributions (GSD < 1.2) and different sizes (MMAD = 5.98 μm, 10.1 μm, 15.5 μm) were measured first to study the dependence of colloidal stability on particle size. Particles with different surface rugosity were then designed by adding different fractions of trileucine, a shell former, and their suspension stability measured to further study the effects of surface roughness on the colloidal stability of pressurized suspensions.

RESULTS

The colloidal stability significantly improved (p < 0.001) from the suspension with 15.5 μm-particles to the suspension with 5.98 μm-particles as quantified by the decreased instability index from 0.63 ± 0.04 to 0.07 ± 0.01, demonstrating a strongly size-dependent colloidal stability. No significant improvement of suspension stability (p > 0.1) was observed at low trileucine fraction at 0.4 % where particles remained relatively smooth until the surface rugosity of the particles was improved by the higher trileucine fractions at 1.0 % and 5.0 %, which was indicated by the substantially decreased instability index from 0.27 ± 0.02 for the suspensions with trehalose model particles to 0.18 ± 0.01 (p < 0.01) and 0.03 ± 0.01 (p < 0.002) respectively.

CONCLUSIONS

Surface modification of particles by adding shell formers like trileucine to the feed solutions of spray drying was demonstrated to be a promising method of improving the colloidal stability of pharmaceutical suspensions in pressurized metered dose inhalers.

Understanding the Impacts of Surface Compositions on the In-Vitro Dissolution and Aerosolization of Co-Spray-Dried Composite Powder Formulations for Inhalation

PURPOSE

Dissolution behavior of dry powder inhaler (DPI) antibiotic formulations in the airways may affect their efficacy especially for poorly-soluble antibiotics such as azithromycin. The main objective of this study was to understand the effects of surface composition on the dissolution of spray dried azithromycin powders by itself and in combination with colistin.

METHODS

Composite formulations of azithromycin (a poorly water-soluble molecule) and colistin (a water-soluble molecule) were produced by spray drying. The resultant formulations were characterized for particle size, morphology, surface composition, solid-state properties, solubility and dissolution.

RESULTS

The results demonstrate that surfaces composition has critical impacts on the dissolution of composite formulations. Colistin was shown to increase the solubility of azithromycin. For composite formulations with no surface colistin, azithromycin released at a similar dissolution rate as the spray-dried azithromycin alone. An increase in surface colistin concentration was shown to accelerate the dissolution of azithromycin. The dissolution of colistin from the composite formulations was significantly slower than the spray-dried pure colistin. In addition, FTIR spectrum showed intermolecular interactions between azithromycin and colistin in the composite formulations, which could contribute to the enhanced solubility and dissolution of azithromycin.

CONCLUSIONS

Our study provides fundamental understanding of the effects of surface concentration of colistin on azithromycin dissolution of co-spray-dried composite powder formulations.

High dose dry powder inhalers to overcome the challenges of tuberculosis treatment

Tuberculosis (TB) is a major global health burden. The emergence of the human immunodeficiency virus (HIV) epidemic and drug resistance has complicated global TB control. Pulmonary delivery of drugs using dry powder inhalers (DPI) is an emerging approach to treat TB. In comparison with the conventional pulmonary delivery for asthma and chronic obstructive pulmonary disease (COPD), TB requires high dose delivery to the lung. However, high dose delivery depends on the successful design of the inhaler device and the formulation of highly aerosolizable powders. Particle engineering techniques play an important role in the development of high dose dry powder formulations. This review focuses on the development of high dose dry powder formulations for TB treatment with background information on the challenges of the current treatment of TB and the potential for pulmonary delivery. Particle engineering techniques with a particular focus on the spray drying and a summary of the developed dry powder formulations using different techniques are also discussed.

Considerations in preparing for clinical studies of inhaled rifampicin to enhance tuberculosis treatment

Drug delivery via the inhaled route has advantages for treating local and systemic diseases. Pulmonary drug delivery may have potential in treating tuberculosis (TB), which is mainly localised in the lung (pulmonary tuberculosis ∼75%) while also affecting other organs (extra-pulmonary tuberculosis). Currently, rifampicin, a first-line anti-tubercular drug, is given orally and the maximum daily oral dose is the lesser of 10 mg/kg or 600 mg. Since only a small fraction of this dose is available in the lung, concentrations may frequently fail to reach bactericidal levels, and therefore, contribute to the development of multi-drug resistant pulmonary TB. Pulmonary delivery of rifampicin, either alone or in addition to the standard oral dose, has the potential to achieve a high concentration of rifampicin in the lung at a relatively low administered dose that is sufficient to kill bacteria and reduce the development of drug resistance. As yet, no clinical study in humans has reported the pharmacokinetics or the efficacy of pulmonary delivery of rifampicin for TB. This review discusses the opportunities and challenges of rifampicin delivery via the inhaled route and important considerations for future clinical studies on high dose inhaled rifampicin are illustrated.