Drug delivery to the lungs: challenges and opportunities

PET imaging to assess the impact of P-glycoprotein on pulmonary drug delivery in rats

Several drugs approved for inhalation for the treatment of pulmonary diseases are substrates of the adenosine triphosphate-binding cassette (ABC) transporter P-glycoprotein (P-gp). P-gp is expressed in the apical membrane of pulmonary epithelial cells and could play a role in modulating the pulmonary absorption and distribution of inhaled drugs, thereby potentially contributing to variability in therapeutic response and/or systemic side effects. We developed a new in vivo experimental approach to assess the functional impact of P-gp on the pulmonary delivery of inhaled drugs in rats. By using positron emission tomography (PET) imaging, we measured the intrapulmonary pharmacokinetics of the model P-gp substrates (R)-[¹¹C]verapamil ([¹¹C]VPM) and [¹¹C]-N-desmethyl-loperamide ([¹¹C]dLOP) administered by intratracheal aerosolization in three rat groups: wild-type, Abcb1a/b^(-/-) and wild-type treated with the P-gp inhibitor tariquidar. Lung exposure (AUC_{lung_right}) to [¹¹C]VPM was 64% and 50% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b^(-/-) rats, respectively, compared to untreated wild-type rats. For [¹¹C]dLOP, AUC_{lung_right} was 59% and 34% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b^(-/-) rats, respectively. Our results show that P-gp can affect the pulmonary disposition of inhaled P-gp substrates, whereby a decrease in P-gp activity may lead to lower lung exposure and potentially to a decrease in therapeutic efficacy. Our study highlights the potential of PET imaging with intratracheally aerosolized radiotracers to assess the impact of membrane transporters on pulmonary drug delivery, in rodents and potentially also in humans.

Prospects of Inhaled Phage Therapy for Combatting Pulmonary Infections

With respiratory infections accounting for significant morbidity and mortality, the issue of antibiotic resistance has added to the gravity of the situation. Treatment of pulmonary infections (bacterial pneumonia, cystic fibrosis-associated bacterial infections, tuberculosis) is more challenging with the involvement of multi-drug resistant bacterial strains, which act as etiological agents. Furthermore, with the dearth of new antibiotics available and old antibiotics losing efficacy, it is prudent to switch to non-antibiotic approaches to fight this battle. Phage therapy represents one such approach that has proven effective against a range of bacterial pathogens including drug resistant strains. Inhaled phage therapy encompasses the use of stable phage preparations given via aerosol delivery. This therapy can be used as an adjunct treatment option in both prophylactic and therapeutic modes. In the present review, we first highlight the role and action of phages against pulmonary pathogens, followed by delineating the different methods of delivery of inhaled phage therapy with evidence of success. The review aims to focus on recent advances and developments in improving the final success and outcome of pulmonary phage therapy. It details the use of electrospray for targeted delivery, advances in nebulization techniques, individualized controlled inhalation with software control, and liposome-encapsulated nebulized phages to take pulmonary phage delivery to the next level. The review expands knowledge on the pulmonary delivery of phages and the advances that have been made for improved outcomes in the treatment of respiratory infections.

Zinc ions coordinated carboxymethyl chitosan-hyaluronic acid microgel for pulmonary drug delivery

Microgel affords a porous and swollen microstructure for the establishment of pulmonary delivery system with sustained released properties. Here, we report a microgel (with the diameter around 4 μm) prepared with a precipitation method, synthesized by coordinating Zn²⁺ to the Schiff base cross-linked carboxymethyl chitosan and glycol split hyaluronate. The microgel has shown well swollen and pH sensitive behaviors, high safety and biocompatibility in vitro. Besides, the biomaterial could escape from macrophage phagocytosis, a key factor contribute to quick drug clearance in the lung after co-incubated with RAW 264.7 cells. In consist with this, the bovine serum albumin loaded in the microgel showed sustained release behavior in 24 h in vitro; meanwhile, the drug had a retention time up to 36 h in the lung and followed by clearance in ICR mice through pulmonary administration. Thus, our microgel platform provides a promising candidate for pulmonary drug delivery systems with controlled release rate.

Inhalation delivery of repurposed drugs for lung cancer: Approaches, benefits and challenges

Lung cancer (LC) is one of the leading causes of mortality accounting for almost 25% of cancer deaths throughout the world. The shortfall of affordable and effective first-line chemotherapeutics, the existence of resistant tumors, and the non-optimal route of administration contribute to poor prognosis and high mortality in LC. Administration of repurposed non-oncology drugs (RNODs) loaded in nanocarriers (NCs) via inhalation may prove as an effective alternative strategy to treat LC. Furthermore, their site-specific release through inhalation route using an appropriate inhalation device would offer improved therapeutic efficacy, thereby reducing mortality and improving patients' quality of life. The current manuscript offers a comprehensive overview on use of RNODs in LC treatment with an emphasis on their inhalation delivery and the associated challenges. The role of NCs to improve lung deposition and targeting of RNODs via inhalation are also elaborated. In addition, information about various RNODs in clinical trials for the treatment of LC, possibility for repurposing phytoceuticals against LC via inhalation and the bottlenecks associated with repurposing RNODs against cancer are also highlighted. Based on the reported studies covered in this manuscript, it was understood that delivery of RNODs via inhalation has emerged as a propitious approach. Hence, it is anticipated to provide effective first-line treatment at an affordable cost in debilitating LC from low and middle-income countries (LMIC).

Nebulizer systems: a new frontier for therapeutics and targeted delivery

Drug delivery via the pulmonary route is a cornerstone in the pharmaceutical sector as an alternative to oral and parenteral administration. Nebulizer inhalation treatment offers multiple drug administration, easily employed with tidal breathing, suitable for children and elderly, can be adapted for severe patients and visible spray ensures patient satisfaction. This review discusses the operational and mechanical characteristics of nebulizer delivery devices in terms of aerosol production processes, their usage, benefits and drawbacks that are currently shaping the contemporary landscape of inhaled drug delivery. With the advent of particle engineering, novel inhaled nanosystems can be successfully developed to increase lung deposition and decrease pulmonary clearance. The above-mentioned advances might pave the path for treating a life-threatening disorder like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is also discussed in the current state of the art.

Therapeutic Delivery of Nitric Oxide Utilizing Saccharide-Based Materials

As a gasotransmitter, nitric oxide (NO) regulates physiological pathways and demonstrates therapeutic effects such as vascular relaxation, anti-inflammation, antiplatelet, antithrombosis, antibacterial, and antiviral properties. However, gaseous NO has high reactivity and a short half-life, so NO delivery and storage are critical questions to be solved. One way is to develop stable NO donors and the other way is to enhance the delivery and storage of NO donors from biomaterials. Most of the researchers studying NO delivery and applications are using synthetic polymeric materials, and they have demonstrated significant therapeutic effects of these NO-releasing polymeric materials on cardiovascular diseases, respiratory disease, bacterial infections, etc. However, some researchers are exploring saccharide-based materials to fulfill the same tasks as their synthetic counterparts while avoiding the concerns of biocompatibility, biodegradability, and sustainability. Saccharide-based materials are abundant in nature and are biocompatible and biodegradable, with wide applications in bioengineering, drug delivery, and therapeutic disease treatments. Saccharide-based materials have been implemented with various NO donors (like S-nitrosothiols and N-diazeniumdiolates) via both chemical and physical methods to deliver NO. These NO-releasing saccharide-based materials have exhibited controlled and sustained NO release and demonstrated biomedical applications in various diseases (respiratory, Crohn's, cardiovascular, etc.), skin or wound applications, antimicrobial treatment, bone regeneration, anticoagulation, as well as agricultural and food packaging. This review aims to highlight the studies in methods and progress in developing saccharide-based NO-releasing materials and investigating their potential applications in biomedical, bioengineering, and disease treatment.

Challenges and solutions in polymer drug delivery for bacterial biofilm treatment: A tissue-by-tissue account

To tackle the emerging antibiotic resistance crisis, novel antimicrobial approaches are urgently needed. Bacterial communities (biofilms) are a particular concern in this context. Biofilms are responsible for most human infections and are inherently less susceptible to antibiotic treatments. Biofilms have been linked with several challenging chronic diseases, including implant-associated osteomyelitis and chronic wounds. The specific local environments present in the infected tissues further contribute to the rise in antibiotic resistance by limiting the efficacy of systemic antibiotic therapies and reducing drug concentrations at the infection site, which can lead to reoccurring infections. To overcome the shortcomings of systemic drug delivery, encapsulation within polymeric carriers has been shown to enhance antimicrobial efficacy, permeation and retention at the infection site. In this Review, we present an overview of current strategies for antimicrobial encapsulation within polymeric carriers, comparing challenges and solutions on a tissue-by-tissue basis. We compare challenges and proposed drug delivery solutions from the perspective of the local environments for biofilms found in oral, wound, gastric, urinary tract, bone, pulmonary, vaginal, ocular and middle/inner ear tissues. We will also discuss future challenges and barriers to clinical translation for these therapeutics. The following Review demonstrates there is a significant imbalance between the research focus being placed on different tissue types, with some targets (oral and wound biofims) being extensively more studied than others (vaginal and otitis media biofilms and endocarditis). Furthermore, the importance of the local tissue environment when selecting target therapies is demonstrated, with some materials being optimal choices for certain sites of bacterial infection, while having limited applicability in others.

Organic cation transporters (OCTs/OCTNs) in human primary alveolar epithelial cells

Alveolar epithelium, besides exerting a key role in gas exchange and surfactant production, plays important functions in host defense and inflammation. Pathological conditions associated to alveolar dysfunction include Acute Respiratory Distress Syndrome (ARDS), asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). The use of predictive in vitro models of human alveolar epithelium is nowadays required for the study of disease mechanisms, as well as of pharmacokinetic parameters of pulmonary drugs delivery. Here, we employed a novel 3D model of human alveoli, namely EpiAlveolar™, consisting of primary alveolar epithelial cells, pulmonary endothelial cells and fibroblasts, that reflects properly the in vivo-like conditions. In EpiAlveolar™ we performed a characterization of Organic Cation Transporters (OCTs and OCTNs) expression and activity and we found that OCTN2, OCT1 and OCT3 are expressed on the basolateral membrane; instead, ATB^0,+ transporter for cationic and neutral amino acids, which shares with OCTN2 the affinity for carnitine as substrate, is readily detectable and functional at the apical side. We also show that these transporters differentially interact with anticholinergic drugs. Overall, our findings reveal close similarities of EpiAlveolar™ with the tracheal/bronchial epithelium (EpiAirway™ model) and entrust this alveolar tissue as a potential tool for the screening of biopharmaceuticals molecules.

Nanoparticle-Based Drug Delivery System: The Magic Bullet for the Treatment of Chronic Pulmonary Diseases

Chronic pulmonary diseases encompass different persistent and lethal diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF), asthma, and lung cancers that affect millions of people globally. Traditional pharmacotherapeutic treatment approaches (i.e., bronchodilators, corticosteroids, chemotherapeutics, peptide-based agents, etc.) are not satisfactory to cure or impede diseases. With the advent of nanotechnology, drug delivery to an intended site is still difficult, but the nanoparticle's physicochemical properties can accomplish targeted therapeutic delivery. Based on their surface, size, density, and physical-chemical properties, nanoparticles have demonstrated enhanced pharmacokinetics of actives, achieving the spotlight in the drug delivery research field. In this review, the authors have highlighted different nanoparticle-based therapeutic delivery approaches to treat chronic pulmonary diseases along with the preparation techniques. The authors have remarked the nanosuspension delivery via nebulization and dry powder carrier is further effective in the lung delivery system since the particles released from these systems are innumerable to composite nanoparticles. The authors have also outlined the inhaled particle's toxicity, patented nanoparticle-based pulmonary formulations, and commercial pulmonary drug delivery devices (PDD) in other sections. Recently advanced formulations employing nanoparticles as therapeutic carriers for the efficient treatment of chronic pulmonary diseases are also canvassed.

Mesoporous silica nanoparticles for pulmonary drug delivery

Over the last years, respiratory diseases represent a clinical concern, being included among the leading causes of death in the world due to the lack of effective lung therapies, mainly ascribed to the pulmonary barriers affecting the delivery of drugs to the lungs. In this way, nanomedicine has arisen as a promising approach to overcome the limitations of current therapies for pulmonary diseases. The use of nanoparticles allows enhancing drug bioavailability at the target site while minimizing undesired side effects. Despite different approaches have been developed for pulmonary delivery of drugs, including the use of polymers, lipid-based nanoparticles, and inorganic nanoparticles, more efforts are required to achieve effective pulmonary drug delivery. This review provides an overview of the clinical challenges in main lung diseases, as well as highlighted the role of nanomedicine in achieving efficient pulmonary drug delivery. Drug delivery into the lungs is a complex process limited by the anatomical, physiological and immunological barriers of the respiratory system. We discuss how nanomedicine can be useful to overcome these pulmonary barriers and give insights for the rational design of future nanoparticles for enhancing lung treatments. We also attempt herein to display more in detail the potential of mesoporous silica nanoparticles (MSNs) as promising nanocarrier for pulmonary drug delivery by providing a comprehensive overview of their application in lung delivery to date while discussing the use of these particles for the treatment of respiratory diseases.

Inhalable nanoparticles delivery targeting alveolar macrophages for the treatment of pulmonary tuberculosis

Pulmonary tuberculosis is a highly prevalent respiratory disease that affects approximately a quarter of the world's population. The drug treatment protocol for tuberculosis is complex because the Mycobacterium tuberculosis (M. tuberculosis) invades macrophages and begins to infect. Thus treatment usually includes combination therapy with several drugs such as rifampicin, pyrazinamide, isoniazid, and ethambutol over a long dosing period. Therefore, drug-delivery technologies have been developed to improve patient compliance with medication, reduce adverse effects, and increase effectiveness of the treatment. In the present review, we have discussed recent inhalable nanopharmaceutical systems for the treatment of pulmonary tuberculosis and investigated their design and effectiveness. We examined the underlying processes and characteristics of spray-drying technology and studied the formulation of a dry carrier using spray-drying method. Moreover, we reviewed various research articles on pulmonary delivery of nanoparticles using these carriers, and studied their alveolar macrophage targeting ability and therapeutic effects. Further, we appraised the effectiveness of nanoparticle inhalation therapy for the treatment of pulmonary tuberculosis and its potential as a treatment strategy for lung diseases.

A technology evaluation of CVT-301 (Inbrija): an inhalable therapy for treatment of Parkinson's disease

Introduction: The most widely used pharmacological treatment for Parkinson's disease is levodopa, the precursor for dopamine formation in the brain. Over time, the effectiveness of levodopa declines, and patients experience motor fluctuations, or OFF periods. A levodopa formulation administered via a capsule-based oral inhaler provides a new delivery mechanism for levodopa that provides rapid relief of OFF periods.Areas covered: CVT-301 is a dry powder formulation designed to supply levodopa to the systemic circulation via pulmonary absorption. The technology, pharmacokinetics, efficacy, and safety data of this formulation are presented.Expert opinion: Oral inhalation is a novel method of administration for levodopa that bypasses the gastrointestinal tract, allowing levodopa to enter the systemic circulation rapidly and more reliably than oral medications. Gastrointestinal dysfunction, a common feature of Parkinson's disease, can lead to impaired absorption of oral medications. Pulmonary delivery rapidly elevates levodopa plasma concentrations to provide relief of OFF periods for patients receiving oral levodopa.

Microencapsulated Chitosan-Based Nanocapsules: A New Platform for Pulmonary Gene Delivery

In this work, we propose chitosan (CS)-based nanocapsules (NCs) for pulmonary gene delivery. Hyaluronic acid (HA) was incorporated in the NCs composition (HA/CS NCs) aiming to promote gene transfection in the lung epithelium. NCs were loaded with a model plasmid (pCMV-βGal) to easily evaluate their transfection capacity. The plasmid encapsulation efficiencies were of approx. 90%. To facilitate their administration to the lungs, the plasmid-loaded NCs were microencapsulated in mannitol (Ma) microspheres (MS) using a simple spray-drying technique, obtaining dry powders of adequate properties. In vivo, the MS reached the deep lung, where the plasmid-loaded CS-based NCs were released and transfected the alveolar cells more homogeneously than the control formulation of plasmid directly microencapsulated in Ma MS. The HA-containing formulation achieved the highest transfection efficiency, in a more extended area and more homogeneously distributed than the rest of tested formulations. The new micro-nanostructured platform proposed in this work represents an efficient strategy for the delivery of genetic material to the lung, with great potential for the treatment of genetic lung diseases.

Engineering of konjac glucomannan into respirable microparticles for delivery of antitubercular drugs

Few medically-approved excipients are available for formulation strategies to endow microcarriers with improved performance in lung drug targeting. Konjac glucomannan (KGM) is a novel, biocompatible material, comprising mannose units potentially inducing macrophage uptake for the treatment of macrophage-mediated diseases. This work investigated spray-dried KGM microparticles as inhalable carriers of model antitubercular drugs, isoniazid (INH) and rifabutin (RFB). The polymer was characterised and different polymer/drug ratios tested in the production of microparticles for which respirability was assessed in vitro. The swelling of KGM microparticles and release of drugs in simulated lung fluid were characterised and the biodegradability in presence of β-mannosidase, a lung hydrolase, determined. KGM microparticles were drug loaded with 66-91% association efficiency and had aerodynamic diameter around 3 µm, which enables deep lung penetration. The microparticles swelled upon liquid contact by 40-50% but underwent size reduction (>62% in 90 min) in presence of β-mannosidase, indicating biodegradability. Finally, drug release was tested showing slower release of RFB compared with INH but complete release of both within 24 h. This work identifies KGM as a biodegradable polymer of natural origin that can be engineered to encapsulate and release drugs in respirable microparticles with physical and chemical macrophage-targeting properties.

Pulmonary Drug Delivery of Antimicrobials and Anticancer Drugs Using Solid Dispersions

It is well established that currently available inhaled drug formulations are associated with extremely low lung deposition. Currently available technologies alleviate this low deposition problem via mixing the drug with inert larger particles, such as lactose monohydrate. Those inert particles are retained in the inhalation device or impacted in the throat and swallowed, allowing the smaller drug particles to continue their journey towards the lungs. While this seems like a practical approach, in some formulations, the ratio between the carrier to drug particles can be as much as 30 to 1. This limitation becomes more critical when treating lung conditions that inherently require large doses of the drug, such as antibiotics and antivirals that treat lung infections and anticancer drugs. The focus of this review article is to review the recent advancements in carrier free technologies that are based on coamorphous solid dispersions and cocrystals that can improve flow properties, and help with delivering larger doses of the drug to the lungs.

Inhalable liposomes for treating lung diseases: clinical development and challenges

Inhalation delivery of liposomal drugs has distinct advantages for the treatment of pulmonary diseases. Inhalable liposomes of several drugs are currently undergoing clinical trials for a range of indications in the lungs. Herein, general principles of pulmonary delivery as well as the clinical development of inhalable liposomal drugs are reviewed.

Augmentation therapy with alpha 1-antitrypsin: present and future of production, formulation, and delivery

Alpha 1-antitrypsin is one of the first protein therapeutics introduced on the market - more than 30 years ago - and, to date, it is indicated only for the treatment of the severe forms of a genetic condition known as alpha-1 antitrypsin deficiency. The only approved preparations are derived from plasma, posing potential problems associated with its limited supply and high processing costs. Moreover, augmentation therapy with alpha 1-antitrypsin is still limited to intravenous infusions, a cumbersome regimen for patients. Here, we review the recent literature on its possible future developments, focusing on i) the recombinant alternatives to the plasma-derived protein, ii) novel formulations, and iii) novel administration routes. Regulatory issues and the still unclear noncanonical functions of alpha 1-antitrypsin - possibly associated with the glycosylation pattern found only in the plasma-derived protein - have hindered the introduction of new products. However, potentially new therapeutic indications other than the treatment of alpha-1 antitrypsin deficiency might open the way to new sources and new formulations.

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.

Cell-specific drug targeting in the lung

Non-targeted drug delivery systems have several limitations including the decreased bioavailability of the drug, poor stability and rapid clearance in addition to off-target distribution. Cell-specific targeted delivery approaches promise to overcome some of these limitations and enhance therapeutic selectivity. In this review, we aim to discuss cell-specific targeted approachesin the lung at the biochemical and molecular levels. These approaches include;a) directly administered small molecule drugs with intracellular action; b) targeted biologics and synthetic hybrids with extracellular action; c) site activateddrugs; and d) delivery systems.We discuss the pharmaceutical and biochemical parameters that govern the fate of drug molecules at delivery sites while presenting an overview of relevant literature surrounding this area of research and current advancements.

Pulmonary delivery of cationic liposomal hydroxycamptothecin and 5-aminolevulinic acid for chemo-sonodynamic therapy of metastatic lung cancer

Sonodynamic therapy (SDT) has been tried for cancer treatment; however, sonosensitizers are usually administered by injection, leading to low distribution in the tumor tissue and compromised therapeutic effect, even serious side effect. Here, we combined cationic liposomal hydroxycamptothecin (CLH) and 5-aminolevulinic acid (5-ALA) via intratracheal (i.t.) administration for the chemo-sonodynamic (Chemo-SDT) therapy of metastatic lung cancer. CLH was prepared from HCPT and the lipid mixture of soybean lecithin/cholesterol/octadecylamine with a film method. The optimal pre-incubation time of 5-ALA with tumor cells before ultrasound exposure was 4 h, for sake of sonosensitizer accumulation, i.e., protoporphyrin IX, the metabolite of 5-ALA. In vitro studies showed the higher cytotoxicity of Chemo-SDT compared to the other treatments, including i.t. CLH, intravenous (i.v.) CLH, and SDT alone. The combination of pulmonary delivery and Chemo-SDT showed the highest anticancer effect among the treatments on the metastatic lung tumor-bearing mice, which was judged according to the tumor appearance and pathological sections. The major anticancer mechanism of Chemo-SDT included the improved apoptosis of cancer cells and the enhanced production of reactive oxygen species, and more importantly, the synergy of chemotherapy and SDT. Pulmonary delivery of chemotherapeutics and sonosensitizers is a promising strategy for the treatment of lung cancer.

Multiscale Co-reconstruction of Lung Architectures and Inhalable Materials Spatial Distribution

The effective pulmonary deposition of inhaled particulate carriers loaded with drugs is a prerequisite for therapeutic effects of drug delivery via inhalation route. Revealing the sophisticated lung scaffold and intrapulmonary distribution of particles at three-dimensional (3D), in-situ, and single-particle level remains a fundamental and critical challenge for dry powder inhalation in pre-clinical research. Here, taking advantage of the micro optical sectioning tomography system, the high-precision cross-scale visualization of entire lung anatomy is obtained. Then, co-localized lung-wide datasets of both cyto-architectures and fluorescent particles are collected at full scale with the resolution down to individual particles. The precise spatial distribution pattern reveals the region-specific distribution and structure-associated deposition of the inhalable particles in lungs, which is undetected by previous methods. Overall, this research delivers comprehensive and high-resolution 3D detection of pulmonary drug delivery vectors and provides a novel strategy to evaluate materials distribution for drug delivery.

The clinical path to deliver encapsulated phages and lysins

The global emergence of multidrug-resistant pathogens is shaping the current dogma regarding the use of antibiotherapy. Many bacteria have evolved to become resistant to conventional antibiotherapy, representing a health and economic burden for those afflicted. The search for alternative and complementary therapeutic approaches has intensified and revived phage therapy. In recent decades, the exogenous use of lysins, encoded in phage genomes, has shown encouraging effectiveness. These two antimicrobial agents reduce bacterial populations; however, many barriers challenge their prompt delivery at the infection site. Encapsulation in delivery vehicles provides targeted therapy with a controlled compound delivery, surpassing chemical, physical and immunological barriers that can inactivate and eliminate them. This review explores phages and lysins' current use to resolve bacterial infections in the respiratory, digestive, and integumentary systems. We also highlight the different challenges they face in each of the three systems and discuss the advances towards a more expansive use of delivery vehicles.

Disease Models: Lung Models for Testing Drugs Against Inflammation and Infection

Lung diseases have increasingly attracted interest in the past years. The all-known fear of failing treatments against severe pulmonary infections and plans of the pharmaceutical industry to limit research on anti-infectives to a minimum due to cost reasons makes infections of the lung nowadays a "hot topic." Inhalable antibiotics show promising efficacy while limiting adverse systemic effects to a minimum. Moreover, in times of increased life expectancy in developed countries, the treatment of chronic maladies implicating inflammatory diseases, like bronchial asthma or chronic obstructive pulmonary disease, becomes more and more exigent and still lacks proper treatment.In this chapter, we address in vitro models as well as necessary in vivo models to help develop new drugs for the treatment of various severe pulmonary diseases with a strong focus on infectious diseases. By first presenting the essential hands-on techniques for the setup of in vitro models, we intend to combine these with already successful and interesting model approaches to serve as some guideline for the development of future models. The overall goal is to maximize time and cost-efficacy and to minimize attrition as well as animal trials when developing novel anti-infective therapeutics.

Salvianolic acid B inhalation solution enhances antifibrotic and anticoagulant effects in a rat model of pulmonary fibrosis

The purpose of this study was to investigate the antifibrotic effect and anticoagulant ability of salvianolic acid B (SAB) inhalation solution on bleomycin (BLM)-induced idiopathic pulmonary fibrosis (IPF) in rats. We investigated how the osmotic pressure and concentration of SAB in an aerosol exerted effects. We also determined the aerodynamic particle size distribution and the uniformity of the delivery dose; these parameters were found to be suitable for inhalation. Compared with BLM group, the levels of hydroxyproline (HYP), collagen-1 (Col-1), tissue factor (TF) / coagulation factor VII (TF-VIIa), activated coagulation factor X (FXa), thrombin-antithrombin complex (TAT), fibrinogen degradation product (FDP) and plasminogen activator inhibitor-1 (PAI-1) decreased in SAB group. The increased expression of coagulation factor Ⅱ (FⅡ), coagulation factor X (FX), tissue type plasminogen activator (t-PA) and urokinase type plasminogen activator (u-PA) proved that SAB has obvious antifibrotic and anticoagulant effects. Western blotting and immunofluorescence further showed that compared with the BLM group, the SAB group of rats exhibited significant reductions in the expression levels of protease-activated receptors-1 (PAR-1) and phospho-protein kinase C (p-PKC) and increased expression levels of protein kinase C (PKC) in lung tissue. Furthermore, SAB reduced the infiltration of lymphocytes and neutrophils, protected the basic structure of the lung from destruction, inhibited the proliferation of fibrous tissue. Collectively, our data revealed that SAB may exert its antifibrotic and anticoagulant effects by preventing the expression of PAR-1 and phosphorylation of PKC.

Nanomedicine for the SARS-CoV-2: State-of-the-Art and Future Prospects

The newly emerged ribonucleic acid (RNA) enveloped human beta-coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection caused the COVID-19 pandemic, severely affects the respiratory system, and may lead to death. Lacking effective diagnostics and therapies made this pandemic challenging to manage since the SARS-CoV-2 transmits via human-to-human, enters via ACE2 and TMPSSR2 receptors, and damages organs rich in host cells, spreads via symptomatic carriers and is prominent in an immune-compromised population. New SARS-CoV-2 informatics (structure, strains, like-cycles, functional sites) motivated bio-pharma experts to investigate novel therapeutic agents that act to recognize, inhibit, and knockdown combinations of drugs, vaccines, and antibodies, have been optimized to manage COVID-19. However, successful targeted delivery of these agents to avoid off-targeting and unnecessary drug ingestion is very challenging. To overcome these obstacles, this mini-review projects nanomedicine technology, a pharmacologically relevant cargo of size within 10 to 200 nm, for site-specific delivery of a therapeutic agent to recognize and eradicate the SARS-CoV-2, and improving the human immune system. Such combinational therapy based on compartmentalization controls the delivery and releases of a drug optimized based on patient genomic profile and medical history. Nanotechnology could help combat COVID-19 via various methods such as avoiding viral contamination and spraying by developing personal protective equipment (PPE) to increase the protection of healthcare workers and produce effective antiviral disinfectants surface coatings capable of inactivating and preventing the virus from spreading. To quickly recognize the infection or immunological response, design highly accurate and sensitive nano-based sensors. Development of new drugs with improved activity, reduced toxicity, and sustained release to the lungs, as well as tissue targets; and development of nano-based immunizations to improve humoral and cellular immune responses. The desired and controlled features of suggested personalized therapeutics, nanomedicine, is a potential therapy to manage COVID-19 successfully. The state-of-the-art nanomedicine, challenges, and prospects of nanomedicine are carefully and critically discussed in this report, which may serve as a key platform for scholars to investigate the role of nanomedicine for higher efficacy to manage the COVID-19 pandemic.

Unlocking the Power of Exosomes for Crossing Biological Barriers in Drug Delivery

Since the 2013 Nobel Prize was awarded for the discovery of vesicle trafficking, a subgroup of nanovesicles called exosomes has been driving the research field to a new regime for understanding cellular communication. This exosome-dominated traffic control system has increased understanding of many diseases, including cancer metastasis, diabetes, and HIV. In addition to the important diagnostic role, exosomes are particularly attractive for drug delivery, due to their distinctive properties in cellular information transfer and uptake. Compared to viral and non-viral synthetic systems, the natural, cell-derived exosomes exhibit intrinsic payload and bioavailability. Most importantly, exosomes easily cross biological barriers, obstacles that continue to challenge other drug delivery nanoparticle systems. Recent emerging studies have shown numerous critical roles of exosomes in many biological barriers, including the blood–brain barrier (BBB), blood–cerebrospinal fluid barrier (BCSFB), blood–lymph barrier (BlyB), blood–air barrier (BAB), stromal barrier (SB), blood–labyrinth barrier (BLaB), blood–retinal barrier (BRB), and placental barrier (PB), which opens exciting new possibilities for using exosomes as the delivery platform. However, the systematic reviews summarizing such discoveries are still limited. This review covers state-of-the-art exosome research on crossing several important biological barriers with a focus on the current, accepted models used to explain the mechanisms of barrier crossing, including tight junctions. The potential to design and engineer exosomes to enhance delivery efficacy, leading to future applications in precision medicine and immunotherapy, is discussed.

Traditional Chinese medicine combined with pulmonary drug delivery system and idiopathic pulmonary fibrosis: Rationale and therapeutic potential

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Pathogenesis and characteristics of idiopathic pulmonary fibrosis (IPF) are presented.

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The history and current situation of traditional Chinese medicine (TCM) in treating lung diseases are introduced.

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Therapeutic mechanisms of different TCM to treat IPF are summarized.

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Advantages and types of pulmonary drug delivery systems (PDDS) are emphasized.

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Combining TCM with PDDS is a potential strategy to treat IPF.

Idiopathic pulmonary fibrosis (IPF) is a progressive pulmonary interstitial inflammatory disease of unknown etiology, and is also a sequela in severe patients with the Coronavirus Disease 2019 (COVID-19). Nintedanib and pirfenidone are the only two known drugs which are conditionally recommended for the treatment of IPF by the FDA. However, these drugs pose some adverse side effects such as nausea and diarrhoea during clinical applications. Therefore, it is of great value and significance to identify effective and safe therapeutic drugs to solve the clinical problems associated with intake of western medicine. As a unique medical treatment, Traditional Chinese Medicine (TCM) has gradually exerted its advantages in the treatment of IPF worldwide through a multi-level and multi-target approach. Further, to overcome the current clinical problems of oral and injectable intakes of TCM, pulmonary drug delivery system (PDDS) could be designed to reduce the systemic metabolism and adverse reactions of the drug and to improve the bioavailability of drugs. Through PubMed, Google Scholar, Web of Science, and CNKI, we retrieved articles published in related fields in recent years, and this paper has summarized twenty-seven Chinese compound prescriptions, ten single TCM, and ten active ingredients for effective prevention and treatment of IPF. We also introduce three kinds of inhaling PDDS, which supports further research of TCM combined with PDDS to treat IPF.

Recent applications and strategies in nanotechnology for lung diseases

Lung diseases, including COVID-19 and lung cancers, is a huge threat to human health. However, for the treatment and diagnosis of various lung diseases, such as pneumonia, asthma, cancer, and pulmonary tuberculosis, are becoming increasingly challenging. Currently, several types of treatments and/or diagnostic methods are used to treat lung diseases; however, the occurrence of adverse reactions to chemotherapy, drug-resistant bacteria, side effects that can be significantly toxic, and poor drug delivery necessitates the development of more promising treatments. Nanotechnology, as an emerging technology, has been extensively studied in medicine. Several studies have shown that nano-delivery systems can significantly enhance the targeting of drug delivery. When compared to traditional delivery methods, several nanoparticle delivery strategies are used to improve the detection methods and drug treatment efficacy. Transporting nanoparticles to the lungs, loading appropriate therapeutic drugs, and the incorporation of intelligent functions to overcome various lung barriers have broad prospects as they can aid in locating target tissues and can enhance the therapeutic effect while minimizing systemic side effects. In addition, as a new and highly contagious respiratory infection disease, COVID-19 is spreading worldwide. However, there is no specific drug for COVID-19. Clinical trials are being conducted in several countries to develop antiviral drugs or vaccines. In recent years, nanotechnology has provided a feasible platform for improving the diagnosis and treatment of diseases, nanotechnology-based strategies may have broad prospects in the diagnosis and treatment of COVID-19. This article reviews the latest developments in nanotechnology drug delivery strategies in the lungs in recent years and studies the clinical application value of nanomedicine in the drug delivery strategy pertaining to the lung.

Volatile molecules for COVID-19: A possible pharmacological strategy?

COVID-19 is a novel coronavirus disease with a higher incidence of bilateral pneumonia and pleural effusion. The high pulmonary tropism and contagiousness of the virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have stimulated new approaches to combat its widespread diffusion. In developing new pharmacological strategies, the chemical characteristic of volatility can add therapeutic value to the hypothetical drug candidate. Volatile molecules are characterized by a high vapor pressure and are consequently easily exhaled by the lungs after ingestion. This feature could be exploited from a pharmacological point of view, reaching the site of action in an uncommon way but allowing for drug delivery. In this way, a hypothetical molecule for COVID-19 should have a balance between its lung exhalation characteristics and both antiviral and anti-inflammatory pharmacological action. Here, the feasibility, advantages, and disadvantages of a therapy based on oral administration of possible volatile drugs for COVID-19 will be discussed. Both aerosolized antiviral therapy and oral intake of volatile molecules are briefly reviewed, and an evaluation of 1,8-cineole is provided in view of a possible clinical use and also for asymptomatic COVID-19.

Preparation, optimization, and in vivo evaluation of an inhaled solution of total saponins of Panax notoginseng and its protective effect against idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive pulmonary disease that can cause fibrotic remodeling of the surrounding lung, thus leading to respiratory failure. Although IPF is the most common form of idiopathic interstitial pneumonia, the precise mechanisms underlying this condition remain unknown. In this study, we used total saponins of Panax notoginseng inhalation solution (TIS) to induce idiopathic bleomycin-induced pulmonary fibrosis in rats. The uniformity of delivery dose was investigated by analyzing the aerodynamic particle size distribution and drug stability. The potential of hydrogen potential of hydrogen (pH) of the inhalation solution was 7.0 and the solvent 0.9% NaCl solution, thus meeting physiological requirements for pulmonary drug administration. The delivery rate was 1.94 ± 0.16 mg·min-1 and the total dose was 17.40 ± 0.04 mg. TIS was composed of five key components: notoginsenoside R1, ginsenosides Rg1, ginsenosides Re, ginsenosides Rb1, and ginsenosides Rd. The mass median aerodynamic diameter (MMAD) for these five components were 3.62 ± 0.05 µm, 3.62 ± 0.06 µm, 3.65 ± 0.10 µm, 3.62 ± 0.06 µm, and 3.61 ± 0.05 µm, respectively. Fine particle fraction (FPF) was 66.24 ± 0.73%, 66.20 ± 0.89%, 66.07 ± 1.42%, 66.18 ± 0.79%, and 66.29 ± 0.70%, respectively. The MMAD for inhalation solutions needs to be 1-5 µm, which indicates that the components of TIS are suitable for inhalation. It is important to control the particle size of targeted drugs to ensure that the drug is delivered to the appropriate target tissue. In vitro experiments indicated that TIS exhibited high rates of deposition in lung tissue, thus indicating that pulmonary delivery systems may represent a good therapeutic option for patients.

Inhalation of sustained release microparticles for the targeted treatment of respiratory diseases

Delivering drugs through inhalation for systemic and local applications has been in practice since several decades to treat various diseases. In recent times, inhalation drug delivery is becoming one of the highly focused areas of research in the pharmaceutical industry. It is being considered as one of the major portals for delivering drugs because of its wide range of advantages like requirement of low concentrations of drug to reach therapeutic efficacy, surpassing first pass metabolism and a very low incidence of side effects as compared to conventional delivery of drugs. Owing to these favorable characteristics of pulmonary drug delivery, diverse pharmaceutical formulations like liposomes, nanoparticles, and microparticles are developed through consistent efforts for delivery drugs to lungs in suitable form. However, drug-loaded microparticles have displayed various advantages over the other pharmaceutical dosage forms which give a cutting edge over other inhalational drug delivery systems. Assuring results with respect to sustained release through inhalational delivery of drug-loaded microparticles from pre-clinical studies are anticipative of similar benefits in the clinical settings. This review centralizes partly on the advantages of inhalational microparticles over other inhalational dosage forms and largely on the therapeutic applications and future perspectives of inhalable microparticle drug delivery systems.

Two-Year Outcomes for the Double-Blind, Randomized, Sham-Controlled Study of Targeted Lung Denervation in Patients with Moderate to Severe COPD: AIRFLOW-2

Purpose

COPD exacerbations are associated with worsening clinical outcomes and increased healthcare costs, despite use of optimal medical therapy. A novel bronchoscopic therapy, targeted lung denervation (TLD), which disrupts parasympathetic pulmonary innervation of the lung, has been developed to reduce clinical consequences of cholinergic hyperactivity and its impact on COPD exacerbations. The AIRFLOW-2 study assessed the durability of safety and efficacy of TLD additive to optimal drug therapy compared to sham bronchoscopy and optimal drug therapy alone in subjects with moderate-to-severe, symptomatic COPD two years post randomization.

Patients and Methods

TLD was performed in COPD patients (FEV1 30-60% predicted, CAT≥10 or mMRC≥2) in a 1:1 randomized, sham-controlled, double-blinded multicenter study (AIRFLOW-2) using a novel lung denervation system (Nuvaira, Inc., USA). Subjects remained blinded until their 12.5-month follow-up visit when control subjects were offered the opportunity to undergo TLD. A time-to-first-event analysis on moderate and severe and severe exacerbations of COPD was performed.

Results

Eighty-two subjects (FEV1 41.6±7.4% predicted, 50.0% male, age 63.7±6.8 yrs, 24% with prior year respiratory hospitalization) were randomized. Time-to-first severe COPD exacerbation was significantly lengthened in the TLD arm (p=0.04, HR=0.38) at 2 years post-TLD therapy and trended towards similar attenuation for moderate and severe COPD exacerbations (p=0.18, HR=0.71). No significant changes in lung function or SGRQ-C were found 2 years post randomization between groups.

Conclusion

In a randomized trial, TLD demonstrated a durable effect of significantly lower risk of severe AECOPD over 2 years. Further, lung function and quality of life remained stable following TLD.

Clinical Trial Registration

NCT02058459.

An Overview on Spray-Drying of Protein-Loaded Polymeric Nanoparticles for Dry Powder Inhalation

The delivery of therapeutic proteins remains a challenge, despite recent technological advances. While the delivery of proteins to the lungs is the gold standard for topical and systemic therapy through the lungs, the issue still exists. While pulmonary delivery is highly attractive due to its non-invasive nature, large surface area, possibility of topical and systemic administration, and rapid absorption circumventing the first-pass effect, the absorption of therapeutic proteins is still ineffective, largely due to the immunological and physicochemical barriers of the lungs. Most studies using spray-drying for the nanoencapsulation of drugs focus on the delivery of conventional drugs, which are less susceptible to bioactivity loss, compared to proteins. Herein, the development of polymeric nanoparticles by spray-drying for the delivery of therapeutic proteins is reviewed with an emphasis on its advantages and challenges, and the techniques to evaluate their in vitro and in vivo performance. The protein stability within the carrier and the features of the carrier are properly addressed.

Exogenous Surfactant as a Pulmonary Delivery Vehicle for Budesonide In Vivo

Background

Lung inflammation is associated with many respiratory conditions. Consequently, anti-inflammatory medications, like glucocorticoids, have become mainstay intrapulmonary therapeutics. However, their effectiveness for treating inflammation occurring in the alveolar regions of the lung is limited by suboptimal delivery. To improve the pulmonary distribution of glucocorticoids, such as budesonide to distal regions of the lung, exogenous surfactant has been proposed as an ideal delivery vehicle for such therapies. It was therefore hypothesized that fortifying an exogenous surfactant (BLES) with budesonide would enhance efficacy for treating pulmonary inflammation in vivo.

Methods

An intratracheal instillation of heat-killed bacteria was used to elicit an inflammatory response in the lungs of male and female rats. Thirty minutes after this initial instillation, either budesonide or BLES combined with budesonide was administered intratracheally. To evaluate the efficacy of surfactant delivery, various markers of inflammation were measured in the bronchoalveolar lavage and lung tissue.

Results

Although budesonide exhibited anti-inflammatory effects when administered alone, delivery with BLES enhanced those effects by lowering the lavage neutrophil counts and myeloperoxidase activity in lung tissue. Combining budesonide with BLES was also shown to reduce several other pro-inflammatory mediators. These results were shown across both sexes, with no observed sex differences.

Conclusion

Based on these findings, it was concluded that exogenous surfactant can enhance the delivery and efficacy of budesonide in vivo.

Inhaled cytotoxic chemotherapy: clinical challenges, recent developments, and future prospects

INTRODUCTION

Since 1968, inhaled chemotherapy has been evaluated and has shown promising results up to phase II but has not yet reached the market. This is due to technological and clinical challenges that require to be overcome with the aim of optimizing the efficacy and the tolerance of drug to re-open new developments in this field. Moreover, recent changes in the therapeutic standard of care for treating the patient with lung cancer also open new opportunities to combine inhaled chemotherapy with standard treatments.

AREAS COVERED

Clinical and technological concerns are highlighted from the reported clinical trials made with inhaled cytotoxic chemotherapies. This work then focuses on new pharmaceutical developments using dry powder inhalers as inhalation devices and on formulation strategies based on controlled drug release and with sustained lung retention or based on nanomedicine. Finally, new clinical strategies are described in regard to the impact of the immunotherapy on the patient's standard of care.

EXPERT OPINION

The choice of the drug, inhalation device, and formulation strategy as well as the position of inhaled chemotherapy in the patient's clinical care are crucial factors in optimizing local tolerance and efficacy as well as in its scalability and applicability in clinical practice.

Ivermectin: an award-winning drug with expected antiviral activity against COVID-19

Ivermectin is an FDA-approved broad-spectrum antiparasitic agent with demonstrated antiviral activity against a number of DNA and RNA viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite this promise, the antiviral activity of ivermectin has not been consistently proven in vivo. While ivermectin's activity against SARS-CoV-2 is currently under investigation in patients, insufficient emphasis has been placed on formulation challenges. Here, we discuss challenges surrounding the use of ivermectin in the context of coronavirus disease-19 (COVID-19) and how novel formulations employing micro- and nanotechnologies may address these concerns.

A dry powder inhalable formulation of salvianolic acids for the treatment of pulmonary fibrosis: safety, lung deposition, and pharmacokinetic study

Salvianolic acids (SAL), the main bioactive component extracted from Salvia miltiorrhiza, is a natural product with a reported anti-pulmonary fibrosis (PF) effect. SAL is commonly administrated orally; however, it has a low oral bioavailability (less than 5%). The objective of this work was to develop a new dry powder inhalable formulation intended to facilitate the access of SAL to the target place. We prepared the new SAL powder formulation containing L-arginine and 2% of lecithin using the ball milling technique. L-arginine was used to regulate the strong acidity of the SAL solution, and lecithin was added to disperse the powder and improve the flowability. The resulting powder had a content in salvianolic acid B (SALB, the main active principle of SAL) of 66.67%, a particle size of less than 5 μm and a good flowability. In vivo fluorescence imaging showed that the powder could be successfully aerosolized and delivered to the lung. The acute lung irritation study proved that the presence of L-arginine improved the biocompatibility of the powder. Finally, according to the pharmacokinetic study, the new SAL powder formulation was found to significantly increase drug concentration in the lung and the bioavailability. In conclusion, the new dry powder inhalable formulation of SAL developed in this study could be a strategy to enhance the performance of SAL at the lung level. Graphical abstract.

Engineering large porous microparticles with tailored porosity and sustained drug release behavior for inhalation

Sustained drug delivery is considered as an effective strategy to improve the treatment of local lung diseases. In this context, inhalation administration of large porous microparticles (LPPs) represents promising prospects. However, one major challenge with said delivery technology is to control the drug release pattern (especially to decrease the burst release) while maintaining a low mass density/high porosity, which is of high significance for the aerodynamic behavior of LPP systems. Here, we show how to engineer drug-loaded, biodegradable LPPs with varying microstructure by means of a premix membrane emulsification-solvent evaporation (PME-SE) method using poly(vinyl pyrrolidone) (PVP) as the pore former. The influence of PVP concentration on the physicochemical properties, in-vitro drug release behavior and in-vitro aerodynamic performance of the drug-loaded microparticles was tested. We demonstrated that the PME-SE technique led to LPPs with favorable pore distribution characteristics (i.e., low external but high internal porosity) as a function of the PVP concentration. In general, more PVP conditioned a larger discrepancy of the internal vs. external porosity. When the external porosity of the LPP formulation (15% of PVP during the manufacturing process) was less than 3%, the burst release of the embedded drug was significantly reduced compared to LPPs prepared by a "conventional" emulsification solvent evaporation method. All the formulations prepared by the PME-SE method had aerodynamic properties suitable for inhalation. This is the first report indicating that the microstructure of LPPs can be tailored using the PME-SE technology with PVP as a suitable pore former. Doing so, we designed LPP formulations having full control over the drug release kinetics and aerodynamic behavior.

Recent Advances in Polymeric Nanoparticle-Encapsulated Drugs against Intracellular Infections

Polymeric nanocarriers (PNs) have demonstrated to be a promising alternative to treat intracellular infections. They have outstanding performance in delivering antimicrobials intracellularly to reach an adequate dose level and improve their therapeutic efficacy. PNs offer opportunities for preventing unwanted drug interactions and degradation before reaching the target cell of tissue and thus decreasing the development of resistance in microorganisms. The use of PNs has the potential to reduce the dose and adverse side effects, providing better efficiency and effectiveness of therapeutic regimens, especially in drugs having high toxicity, low solubility in the physiological environment and low bioavailability. This review provides an overview of nanoparticles made of different polymeric precursors and the main methodologies to nanofabricate platforms of tuned physicochemical and morphological properties and surface chemistry for controlled release of antimicrobials in the target. It highlights the versatility of these nanosystems and their challenges and opportunities to deliver antimicrobial drugs to treat intracellular infections and mentions nanotoxicology aspects and future outlooks.

Recent advances in the development of microparticles for pulmonary administration

Pulmonary drug delivery offers several benefits for the management of various conditions over other conventional routes. Inhalation of drugs can also be useful for targeting alveolar macrophages and for maintaining a higher drug concentration in the lung tissues to improve the efficacy of drugs and shorten the duration of treatment, thereby reducing drug toxicities. Thus, such an approach is useful in the treatment of various pulmonary and nonpulmonary diseases. Newer techniques and delivery devices have been used for the formulation of inhalable microparticles. Here. we not only focus on advances in inhalation therapy and in the preparation of microparticles, but also address the clinical development and regulatory aspects of such therapies.

Pulmonary Delivery of Fenretinide: A Possible Adjuvant Treatment In COVID-19

At present, there is no vaccine or effective standard treatment for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection (or coronavirus disease-19 (COVID-19)), which frequently leads to lethal pulmonary inflammatory responses. COVID-19 pathology is characterized by extreme inflammation and amplified immune response with activation of a cytokine storm. A subsequent progression to acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can take place, which is often followed by death. The causes of these strong inflammatory responses in SARS-CoV-2 infection are still unknown. As uncontrolled pulmonary inflammation is likely the main cause of death in SARS-CoV-2 infection, anti-inflammatory therapeutic interventions are particularly important. Fenretinide N-(4-hydroxyphenyl) retinamide is a bioactive molecule characterized by poly-pharmacological properties and a low toxicity profile. Fenretinide is endowed with antitumor, anti-inflammatory, antiviral, and immunomodulating properties other than efficacy in obesity/diabetic pathologies. Its anti-inflammatory and antiviral activities, in particular, could likely have utility in multimodal therapies for the treatment of ALI/ARDS in COVID-19 patients. Moreover, fenretinide administration by pulmonary delivery systems could further increase its therapeutic value by carrying high drug concentrations to the lungs and triggering a rapid onset of activity. This is particularly important in SARS-CoV-2 infection, where only a narrow time window exists for therapeutic intervention.

Multifunctional Nanocarriers for Lung Drug Delivery

Nanocarriers have been increasingly proposed for lung drug delivery applications. The strategy of combining the intrinsic and more general advantages of the nanostructures with specificities that improve the therapeutic outcomes of particular clinical situations is frequent. These include the surface engineering of the carriers by means of altering the material structure (i.e., chemical modifications), the addition of specific ligands so that predefined targets are reached, or even the tuning of the carrier properties to respond to specific stimuli. The devised strategies are mainly directed at three distinct areas of lung drug delivery, encompassing the delivery of proteins and protein-based materials, either for local or systemic application, the delivery of antibiotics, and the delivery of anticancer drugs-the latter two comprising local delivery approaches. This review addresses the applications of nanocarriers aimed at lung drug delivery of active biological and pharmaceutical ingredients, focusing with particular interest on nanocarriers that exhibit multifunctional properties. A final section addresses the expectations regarding the future use of nanocarriers in the area.

Aerosol Characteristics and Physico-Chemical Compatibility of Combivent® (Containing Salbutamol and Ipratropium Bromide) Mixed with Three Other Inhalants: Budesonide, Beclomethasone or N-Acetylcysteine

Inhalation therapy with a nebulizer is widely used in chronic respiratory disease. Mixing inhalation solutions/suspensions for simultaneous inhalation is more convenient and might simplify the administration procedure. However, there are no data available to address the in vitro aerosol characteristics and physico-chemical compatibility of Combivent^® (containing Salbutamol and Ipratropium bromide) with other inhalation solutions/suspensions. In order to investigate the in vitro aerosol characteristics and physico-chemical compatibility of Combivent^® with Budesonide, Beclomethasone, and N-acetylcysteine, the appearance, pH, osmotic pressure, chemical stability, mass median aerodynamic diameter (MMAD), fine particles fraction (FPF), particle size corresponding to X50 (particle size, which accounts for 50% of the total cumulative percentage of volume of all particles), delivery rate, and total delivery of the mixed inhalation solution/suspension were tested. There was no change in the appearance such as a change in color or precipitation formation at room temperature. The pH, osmolality, and chemicals of the mixtures were stable for 24 h after mixing. There were no significant differences between Combivent^®, Budesonide, Beclomethasone, N-acetylcysteine, and the mixtures in MMAD, FPF, X50, the delivery rate, and the total delivery. This indicates that the mixtures were physically and chemically compatible. The mixing did not influence the particle size, distribution, or delivery compatibility of the mixtures.

Pharmacokinetic profile analyses for inhaled drugs in humans using the lung delivery and disposition model

The kinetic clarification of lung disposition for inhaled drugs in humans via pharmacokinetic (PK) modeling aids in their development and regulation for systemic and local delivery, but remains challenging due to its multiplex nature. This study exercised our lung delivery and disposition kinetic model to derive the kinetic descriptors for the lung disposition of four drugs [calcitonin, tobramycin, ciprofloxacin and fluticasone propionate (FP)] inhaled via different inhalers from the published PK profile data. With the drug dose delivered to the lung (DTL) estimated from the corresponding γ-scintigraphy or in vivo predictive cascade impactor data, the model-based curve-fitting and statistical moment analyses derived the rate constants of lung absorption (k_a ) and non-absorptive disposition (k_nad ). The k_a values differed substantially between the drugs (0.05-1.00 h^-1 ), but conformed to the lung partition-based membrane diffusion except for FP, and were inhaler/delivery/deposition-independent. The k_nad values also varied widely (0.03-2.32 h^-1 ), yet appeared to be explained by the presence or absence of non-absorptive disposition in the lung via mucociliary clearance, local tissue degradation, binding/sequestration and/or phagocytosis, and to be sensitive to differences in lung deposition. For FP, its k_a value of 0.2 h^-1 was unusually low, suggesting solubility/dissolution-limited slow lung absorption, but was comparable between two inhaler products. Thus, the difference in the PK profile was attributed to differences in the DTL and the k_nad value, the latter likely originating from different aerosol sizes and regional deposition in the lung. Overall, this empirical, rather simpler model-based analysis provided a quantitative kinetic understanding of lung absorption and non-absorptive disposition for four inhaled drugs from PK profiles in humans.

Stability of Polymer Coatings on Nebulizer Membranes During Aerosol Generation

The dimensions of orifices found in aperture plates used for nebulization can be modified by thin polymer coatings with the aim to control the size distribution of the generated aerosol droplets. However, the stability of such polymer coatings on the surface of nebulizer membranes during aerosol generation has not been elucidated. Nebulizer membranes made of stainless steel were covered with a thin film of poly(chloro-p-xylylene) (~1 μm) in the presence or absence of a silane-based adhesion promoter. Thereby, the orifice cross-sections of the nebulizer membrane were reduced by ~50%, accompanied by a remarkable decline in droplet size. Upon continuous nebulization of aqueous test liquids, the droplet size generated by the nonconditioned (no silane), poly(chloro-p-xylylene)-coated membranes reverted to that of the uncoated nebulizer membrane within ~5 min. By contrast, no such rapid return of droplet size to "baseline" values was noticed for the silane-conditioned, poly(chloro-p-xylylene)-coated counterparts. Scanning electron microscopy exhibited significant polymer detachment from the orifices of the nonconditioned (no silane) membranes and thus confirmed the findings from laser diffraction. Overall, silane-based adhesion promoters can increase the persistence of poly(chloro-p-xylylene) coatings on nebulizer membranes during aerosol generation.