Nanotechnology approaches for inhalation treatment of fibrosis

Abstract

Cystic fibrosis (CF) is an autosomal recessive monogenetic disease that afflicts nearly 70?000 patients worldwide. The mutation results in the accumulation of viscous mucus in multiple organs especially in the lungs, liver and pancreas. High associated morbidity and mortality is caused by CF due to the lack of effective therapies. It is widely accepted that morbidity and mortality caused by CF is primarily due to the respiratory manifestations of the disease. Consequently, several approaches were recently developed for treatment of lung complications of CF. However, the lack of effective methods for delivery and especially targeted delivery of therapeutics specifically to lung tissues and cells limits the efficiency of the therapy. Local pulmonary delivery of therapeutics has two major advantages over systemic application. First, it enhances the accumulation of therapeutics specifically in the lungs and therefore increases the efficiency of the treatment. Second, local lung delivery substantially prevents the penetration of the delivered drug into the systemic circulation limiting adverse side effects of the treatment on other organs and tissues. This review is focused on different approaches to the treatment of respiratory manifestations of CF as well as on methods of pulmonary delivery of therapeutics.     

缓释型肺吸入制剂的研究进展

近年来,肺吸入制剂因为直接将药物递送至患病部位、无首过效应、患者依从性大等优点,成为研究热点。但肺吸入制剂仍然存在许多问题如药物消除迅速、给药次数频繁、存在临床用药安全性隐患。本文将从肺部主要的消除机制入手,对目前缓释肺吸入制剂进行综述,为今后肺吸入的临床应用提供思路。     

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.     

Drug Delivery Approaches in Addressing Clinical Pharmacology-Related Issues: Opportunities and Challenges

Various drug delivery approaches can be used to maximize therapeutic efficacy and minimize side effects, by impacting absorption, distribution, metabolism, and elimination (ADME) of a drug compound. For those drugs with poor water solubility or low permeability, techniques such as amorphous solid dispersion, liposomes, and complexations have been used to improve their oral bioavailability. Modified release (MR) formulations have been widely used to improve patient compliance, as well as to reduce side effects, especially for those drugs with short half-lives or narrow therapeutic windows. More than ten drugs using sterile long-acting release (LAR) formulations with clear clinical benefit have been successfully marketed. Furthermore, drug delivery systems have been used in delaying drug clearance processes. Additionally, modifying the in vivo drug distribution using targeted delivery systems has significantly improved oncology treatments. All the drug delivery approaches have their advantages and limitations. For both brand and generic drugs, the achievement of consistent quality and therapeutic performance using drug delivery systems can also pose serious challenges in developing a drug for the market, which requires close collaboration among industry, academia, and regulatory agencies. With the advent of personalized medicines, there will be great opportunities and challenges in utilizing drug delivery systems to provide better products and services for patients.KEY WORDS: absorption, distribution, metabolism, and elimination (ADME); adverse effects; bioequivalence; clinical pharmacology; drug delivery; formulation design; local delivery; long-acting release; modified release; personalized medicine; pharmacokinetic profiles; prodrug; quality; regulatory; targeted delivery; therapeutic performance     

Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) for pulmonary application: A review of the state of the art

Drug delivery by inhalation is a noninvasive means of administration that has following advantages for local treatment for airway diseases: reaching the epithelium directly, circumventing first pass metabolism and avoiding systemic toxicity. Moreover, from the physiological point of view, the lung provides advantages for systemic delivery of drugs including its large surface area, a thin alveolar epithelium and extensive vasculature which allow rapid and effective drug absorption. Therefore, pulmonary application is considered frequently for both, the local and the systemic delivery of drugs. Lipid nanoparticles – Solid Lipid Nanoparticles and Nanostructured Lipid Carriers – are nanosized carrier systems in which solid particles consisting of a lipid matrix are stabilized by surfactants in an aqueous phase. Advantages of lipid nanoparticles for the pulmonary application are the possibility of a deep lung deposition as they can be incorporated into respirables carriers due to their small size, prolonged release and low toxicity. This paper will give an overview of the existing literature about lipid nanoparticles for pulmonary application. Moreover, it will provide the reader with some background information for pulmonary drug delivery, i.e., anatomy and physiology of the respiratory system, formulation requirements, application forms, clearance from the lung, pharmacological benefits and nanotoxicity.     

Surface-engineered smart nanocarrier-based inhalation formulations for targeted lung cancer chemotherapy: a review of current practices

Lung cancer is the second most common and lethal cancer in the world. Chemotherapy is the preferred treatment modality for lung cancer and prolongs patient survival by effective controlling of tumor growth. However, owing to the nonspecific delivery of anticancer drugs, systemic chemotherapy has limited clinical efficacy and significant systemic adverse effects. Inhalation routes, on the other hand, allow for direct delivery of drugs to the lungs in high local concentrations, enhancing their anti-tumor activity with minimum side effects. Preliminary research studies have shown that inhaled chemotherapy may be tolerated with manageable adverse effects such as bronchospasm and cough. Enhancing the anticancer drugs deposition in tumor cells and limiting their distribution to other healthy cells will therefore increase their clinical efficacy and decrease their local and systemic toxicities. Because of the controlled release and localization of tumors, nanoparticle formulations are a viable option for the delivery of chemotherapeutics to lung cancers via inhalation. The respiratory tract physiology and lung clearance mechanisms are the key barriers to the effective deposition and preservation of inhaled nanoparticle formulations in the lungs. Designing and creating smart nanoformulations to optimize lung deposition, minimize pulmonary clearance, and improve cancerous tissue targeting have been the subject of recent research studies. This review focuses on recent examples of work in this area, along with the opportunities and challenges for the pulmonary delivery of smart nanoformulations to treat lung cancers.     

Biodegradable polymeric nanocarriers for pulmonary drug delivery

BACKGROUND: Pulmonary drug delivery is attractive for both local and systemic drug delivery as a non-invasive route that provides a large surface area, thin epithelial barrier, high blood flow and the avoidance of first-pass metabolism. OBJECTIVE: Nanoparticles can be designed to have several advantages for controlled and targeted drug delivery, including controlled deposition, sustained release, reduced dosing frequency, as well as an appropriate size for avoiding alveolar macrophage clearance or promoting transepithelial transport. METHODS: This review focuses on the development and application of biodegradable polymers to nanocarrier-based strategies for the delivery of drugs, peptides, proteins, genes, siRNA and vaccines by the pulmonary route. RESULTS/CONCLUSION: The selection of natural or synthetic materials is important in designing particles or nanoparticle clusters with the desired characteristics, such as biocompatibility, size, charge, drug release and polymer degradation rate.     

Models of deposition,pharmacokinetics, and intersubject variability in respiratory drug delivery

ABSTRACT

Introduction: Aerosol drug delivery to the lungs via inhalation is widely used in the treatment of respiratory diseases. The deposition pattern of inhaled particles within the airways of the respiratory tract is key in determining the initial delivered dose. Thereafter, dose-dependent processes including drug release or dissolution, clearance, and absorption influence local and systemic exposure to inhaled drugs over time.

Areas covered: Empirical correlations, numerical simulation, and in vitro airway geometries that permit improved prediction of extrathoracic and lung deposition fractions in a variety of age groups and breathing conditions are described. Efforts to link deposition models with pharmacokinetic models predicting lung and systemic exposure to inhaled drugs over time are then reviewed. Finally, new methods to predict intersubject variability in extrathoracic deposition, capturing variability in both size and shape of the upper airways, are highlighted.

Expert opinion: Recent work has been done to expand in vitro deposition experiments to a wide range of age groups and breathing conditions, to link regional lung deposition models with pharmacokinetic models, and to improve prediction of intersubject variability. These efforts are improving predictive understanding of respiratory drug delivery, and will aid the development of new inhaled drugs and delivery devices.     

Drug delivery via the respiratory tract.

Inhalation offers an enormous absorptive surface area for rapid drug absorption and substantial absorption of polypeptides. Due to slow clearance from the lower lung, even compounds with very small absorption rates can be absorbed in significant quantities over 10-12h periods. Aerosol dosimetry problems can also be minimized when lung-normal patients are considered. In the near future, optimal formulations will be combined with modified aerosol delivery devices to achieve reproducible dosing. These will be used as alternatives to parenteral delivery for drug doses of the order of milligrams or less. Research on the molecular structural dependence of lung disposition is in its infancy. Absorption kinetics for small molecules are known to depend on lipophilicity and molecular size. For macromolecules however, electronic charge and site of deposition may be additional determinants of bioavailability. Carrier-mediated absorption processes may also be important. The pulmonary absorption of a number of molecules is reviewed with special emphasis on new and promising products of biotechnology like human insulin and human growth hormone. Delivery improvements in the future should ensure, ideally, that nondenatured, monomeric pure compounds are delivered reproducibly and predominantly to the lung itself, so that these compounds may elicit reproducible systemic effects following absorption.     

Design and synthesis of inhaled p38 inhibitors for the treatment of chronic obstructive pulmonary disease

This paper describes the identification and optimization of a novel series of DFG-out binding p38 inhibitors as inhaled agents for the treatment of chronic obstructive pulmonary disease. Structure based drug design and "inhalation by design" principles have been applied to the optimization of the lead series exemplied by compound 1a. Analogues have been designed to be potent and selective for p38, with an emphasis on slow enzyme dissociation kinetics to deliver prolonged lung p38 inhibition. Pharmacokinetic properties were tuned with high intrinsic clearance and low oral bioavailability in mind, to minimize systemic exposure and reduce systemically driven adverse events. High CYP mediated clearance and glucuronidation were targeted to achieve high intrinsic clearance coupled with multiple routes of clearance to minimize drug-drug interactions. Furthermore, pharmaceutical properties such as stability, crystallinity, and solubility were considered to ensure compatibility with a dry powder inhaler. 1ab (PF-03715455) was subsequently identified as a clinical candidate from this series with efficacy and safety profiles confirming its potential as an inhaled agent for the treatment of COPD.     

Experimental pulmonary delivery of cyclosporin A by liposome aerosol

The utilization of CsA–liposome for aerosol delivery by jet nebulizers has potential advantages for clinical development including: aqueous compatibility, sustained pulmonary release to maintain therapeutic drug levels and facilitated delivery to alveolar macrophages and pulmonary lymphocytes. Inhalation of cyclosporin A (CsA)–dilauroylphosphatidylcholine (DLPC) liposome aerosols will theoretically result in localized and sustained delivery of therapeutic CsA concentrations within the lung as an alternative to local immunotherapy for pulmonary diseases. In the lung, targeted delivery of therapeutic CsA concentrations would require lower dosages than via conventional intravenous or oral routes of administration. Potential benefits from targeted lung delivery could include reduced systemic toxicity and prolonged immunosuppressive activity. Aerosol delivery systems have been developed to deposit drugs directly onto pulmonary surfaces at the sites of disease within the lung. A novel HPLC method for tissue analysis of CsA–liposomes is developed and utilized with a solid-phase extraction method to measure CsA recovered from Balb/c mouse lung tissues. A concentrated formulation containing 5 mg CsA–37.5 mg DLPC/ml was nebulized with an Aerotech II nebulizer generating an aerosol particle size distribution (mass median aerodynamic diameter (MMAD)) of 1.7 μm and geometric standard deviation (GSD) of 2.0. After a 15-min aerosol exposure, little of no CsA was detected in the blood, liver, kidney or spleen. The lung contained the highest organ CsA levels with high immunosuppressive activity demonstrating effective pulmonary targeting of the CsA–DLPC liposome aerosol. The results of this system will be utilized as the experimental basis for future pharmacokinetic, toxicological, immunosuppression and other biological studies.     

Drug delivery across length scales

Abstract

Over the last century, there has been a dramatic change in the nature of therapeutic, biologically active molecules available to treat disease. Therapies have evolved from extracted natural products towards rationally designed biomolecules, including small molecules, engineered proteins and nucleic acids. The use of potent drugs which target specific organs, cells or biochemical pathways, necessitates new tools which can enable controlled delivery and dosing of these therapeutics to their biological targets. Here, we review the miniaturisation of drug delivery systems from the macro to nano-scale, focussing on controlled dosing and controlled targeting as two key parameters in drug delivery device design. We describe how the miniaturisation of these devices enables the move from repeated, systemic dosing, to on-demand, targeted delivery of therapeutic drugs and highlight areas of focus for the future.     

Inhibition of chlorine-induced lung injury by the type 4 phosphodiesterase inhibitor rolipram

Chlorine is a highly toxic respiratory irritant that when inhaled causes epithelial cell injury, alveolar-capillary barrier disruption, airway hyperreactivity, inflammation, and pulmonary edema. Chlorine is considered a chemical threat agent, and its release through accidental or intentional means has the potential to result in mass casualties from acute lung injury. The type 4 phosphodiesterase inhibitor rolipram was investigated as a rescue treatment for chlorine-induced lung injury. Rolipram inhibits degradation of the intracellular signaling molecule cyclic AMP. Potential beneficial effects of increased cyclic AMP levels include inhibition of pulmonary edema, inflammation, and airway hyperreactivity. Mice were exposed to chlorine (whole body exposure, 228-270 ppm for 1 h) and were treated with rolipram by intraperitoneal, intranasal, or intramuscular (either aqueous or nanoemulsion formulation) delivery starting 1 h after exposure. Rolipram administered intraperitoneally or intranasally inhibited chlorine-induced pulmonary edema. Minor or no effects were observed on lavage fluid IgM (indicative of plasma protein leakage), KC (Cxcl1, neutrophil chemoattractant), and neutrophils. All routes of administration inhibited chlorine-induced airway hyperreactivity assessed 1 day after exposure. The results of the study suggest that rolipram may be an effective rescue treatment for chlorine-induced lung injury and that both systemic and targeted administration to the respiratory tract were effective routes of delivery.     

Uncovering the regional localization of inhaled salmeterol retention in the lung

Treatment of respiratory disease with a drug delivered via inhalation is generally held as being beneficial as it provides direct access to the lung target site with a minimum systemic exposure. There is however only limited information of the regional localization of drug retention following inhalation. The aim of this study was to investigate the regional and histological localization of salmeterol retention in the lungs after inhalation and to compare it to systemic administration. Lung distribution of salmeterol delivered to rats via nebulization or intravenous (IV) injection was analyzed with high-resolution mass spectrometry imaging (MSI). Salmeterol was widely distributed in the entire section at 5?min after inhalation, by 15?min it was preferentially retained in bronchial tissue. Via a novel dual-isotope study, where salmeterol was delivered via inhalation and d₃-salmeterol via IV to the same rat, could the effective gain in drug concentration associated with inhaled delivery relative to IV, expressed as a site-specific lung targeting factor, was 5-, 31-, and 45-fold for the alveolar region, bronchial sub-epithelium and epithelium, respectively. We anticipate that this MSI-based framework for quantifying regional and histological lung targeting by inhalation will accelerate discovery and development of local and more precise treatments of respiratory disease.     

New aerosol drug delivery systems for the treatment of immune-mediated pulmonary diseases

In the lung, unchecked immune responses mediated predominantly by T-lymphocytes and concurrent inflammation can lead to the development of different pathological conditions such as parenchymal disease, interstitial fibrosis, hypersensitivity pneumonitis, bronchiolitis obliterans and bronchiolar asthma. Targeted modulation of uncontrolled T-cell activation and inhibition of cytokine production within different pulmonary compartments is the challenge for the development of novel methods for immunotherapeutic intervention. Utilization of aerosol technology for pulmonary drug delivery represents new potential opportunities for therapeutic application for such immune-mediated pulmonary diseases. For targeted aerosol pulmonary drug delivery, continuous-flow jet nebulizers have several advantages over metered dose or dry powder inhalers since they are the simplest and most effective for aerosol droplet deposition into the peripheral lung tissues. At the present, the major limitations for targeted pulmonary immunosuppression through effective utilization of nebulizer technology has been the conspicuous lack of suitable formulations. The development of liposomal formulations compatible with aerosol delivery with jet nebulizers has expanded the potential for more effective utilization with an array of potent and effective immunosuppressive drugs. For pulmonary therapy, the utilization of liposomes for aerosol delivery has many potential advantages, including universal carrier suitability for most lipophilic drugs, aqueous compatibility, sustained pulmonary release or depot and intracellular delivery. Drug liposomes may also prevent local irritation in the lung, and increase potency with reduced systemic toxicity. Successful utilization of potent immunosuppressive drugs, like cyclosporin, tacrolimus (FK-506), rapamycin, mycophenolate and budesonide, in a variety of immunopathological conditions for other indications demonstrates their potential efficacy for the treatment of many different immune-mediated pulmonary diseases. The route of delivery to the pulmonary tissues can potentially limit adverse effects and markedly affect localized immunosuppressive activity in the lung. Combination of liposomal formulations with topical aerosol delivery to the central and peripheral lung tissues has expanded potential for more effective utilization with these lipophilic immunosuppressive (and antiinflammatory) drugs. Synergistic combinations can also be developed for localized and sustained delivery of therapeutic drug concentrations within the lung to provide multisite immunosuppression. Drug liposome aerosol technology represents one readily available approach for more effective therapeutic intervention in the lung using cyclosporin, FK-506, rapamycin, mycophenolate, budesonide and other lipophilic drugs.     

Development and evaluation of inhalational liposomal system of budesonide for better management of asthma

Budesonide is a corticosteroid used by inhalation in the prophylactic management of asthma. However, frequent dosing and adverse effects (local and systemic) remain a major concern in the use of budesonide. Liposomal systems for sustained pulmonary drug delivery have been particularly attractive because of their compatibility with lung surfactant components. In the present investigation, pulmonary liposomal delivery system of budesonide was prepared by film hydration method and evaluated for sustained release. Various parameters were optimized with respect to entrapment efficiency as well as particle size of budesonide liposomes. For better shelf life of budesonide liposomes, they were freeze dried using trehalose as cryoprotectant. The liposomes were characterized for entrapment efficiency, particle size, and surface topography; in vitro drug release was evaluated out in simulated lung fluid at 37° at pH 7.4. The respirable or fine particle fraction was determined by using twin stage impinger. The stability study of freeze dried as well as aqueous liposomal systems was carried out at 2-8° and at ambient temperature (28±40). The freeze dried liposomes showed better fine particle fraction and drug content over the period of six months at ambient as well as at 2-8° storage condition compared to aqueous dispersion of liposomes.     

Formulation and Characterization of Spray-Dried Powders Containing Vincristine-Liposomes for Pulmonary Delivery and Its Pharmacokinetic Evaluation From In Vitro and In Vivo

Vincristine (VCR) has been used in the treatment of lung cancer. To improve its efficacy, the designs of elevating lung exposure to drug and decreasing the clearance with extended time were brought out. Pulmonary delivery is regarded as a good choice in pulmonary diseases treatment. Spray-drying is a technology for the preparation of drugs that can be delivered to lung via a dry powder inhaler. The results showed an appropriate particle size and shape for the pulmonary delivery. The aerosol behaved a sustained-release profile while VCR solution released rapidly within 10 h. The antitumor activity was characterized by 3-(4, 5-dimethylthiazol-2-yl) -2, 5-diphenyltetrazolium bromide assay, and half maximal inhibitory concentration values of VCR-liposomes spray-dried powder were 24.42 ± 1.88 nM and 55.28 ± 4.76 nM in MCF-7 and A549 cells, respectively. Compared with the free VCR, the aerosol performed better pharmacokinetic behavior: increased maximum concentration (630.8%) and systemic exposure (429.6%) and decreased elimination half-life (81.1%). The clearance was decreased by 83.2%. Comprehensively, the pulmonary delivery seemed to be a recommendable way to effectively treat the pulmonary disease.     

Toxicity of orally inhaled drug formulations at the alveolar barrier: parameters for initial biological screening

Oral delivery is the most common mode of systemic drug application. Inhalation is mainly used for local therapy of lung diseases but may also be a promising route for systemic delivery of drugs that have poor oral bioavailability. The thin alveolar barrier enables fast and efficient uptake of many molecules and could deliver small molecules and proteins, which are susceptible to degradation and show poor absorption by oral application. The low rate of biotransformation and proteolytic degradation increases bioavailability of drugs but accumulation of not absorbed material may impair normal lung function. This limitation is more relevant for compounds that should be systematically active because higher doses have to be applied to the lung. The review describes processes that determine absorption of orally inhaled formulations, namely dissolution in the lung lining fluid and uptake and degradation by alveolar epithelial cells and macrophages. Dissolution testing in simulated lung fluid, screening for cytotoxicity and pro-inflammatory action in respiratory cells and study of macrophage morphology, and phagocytosis can help to identify adverse effects of pulmonary formulations.     

Drug release kinetics from stent device-based delivery systems

In an effort to overcome the limitations of balloon-expandible intravascular metal stent-induced neointimal formation, drug-coated stent devices have been developed. The stent platform allows the local delivery of drugs to an injury site, thereby reducing the amount of drug exposure to the systemic circulation and other organs. The drug carrier matrix allows the release of the drug in a diffusion-controlled manner over an extended time period after the stent implant. The drugs are chosen such that the complex cascade of events that occurs after stent implantation that leads to smooth muscle cell proliferation and migration towards the intima are inhibited. The success of an antirestenotic drug therapy from a drug-coated stent is dependent, at least partially, on the extent of drug elution from the stent, the duration and rate of release, and accumulation of drug in the arterial wall in such a way that it covers the initiation and progression of vessel wall remodeling. The local vascular drug concentrations achieved are directly correlated with the biological effects and local vascular toxicity, and there is therefore a challenge in finding an optimum dose of drug to be delivered to tissues (ie, one that has the desired therapeutic effect without local adverse effects). There is increased focus on optimization of various factors that affect drug release from the stent system, including the physicochemical properties of the drugs, carrier vehicle formulation, and profile of elution kinetics. This review highlights the various factors involved in drug release kinetics, local vascular toxicity, carrier vehicle matrix, tissue deposition, and distribution through the arterial wall from stent-based drug delivery systems.