Aerosol delivery of DNA/liposomes to the lung for cystic fibrosis gene therapy

Aerosol Inhalation of Gene Delivery Therapy for Pulmonary Diseases

Gene delivery therapy has emerged as a popular approach for the treatment of various diseases. However, it still poses the challenges of accumulation in target sites and reducing off-target effects. Aerosol gene delivery for the treatment of pulmonary diseases has the advantages of high lung accumulation, specific targeting and fewer systemic side effects. However, the key challenge is selecting the appropriate formulation for aerosol gene delivery that can overcome physiological barriers. There are numerous existing gene carriers under study, including viral vectors and non-viral vectors. With the development of biomaterials, more biocompatible substances have applied gene delivery via inhalation. Furthermore, many types of genes can be delivered through aerosol inhalation, such as DNA, mRNA, siRNA and CRISPR/Cas9. Aerosol delivery of different types of genes has proven to be efficient in the treatment of many diseases such as SARS-CoV-2, cystic fibrosis and lung cancer. In this paper, we provide a comprehensive review of the ongoing research on aerosol gene delivery therapy, including the basic respiratory system, different types of gene carriers, different types of carried genes and clinical applications.

Optimization of ionizable lipids for aerosolizable mRNA lipid nanoparticles

Although mRNA lipid nanoparticles (LNPs) are highly effective as vaccines, their efficacy for pulmonary delivery has not yet fully been established. A major barrier to this therapeutic goal is their instability during aerosolization for local delivery. This imparts a shear force that degrades the mRNA cargo and therefore reduces cell transfection. In addition to remaining stable upon aerosolization, mRNA LNPs must also possess the aerodynamic properties to achieve deposition in clinically relevant areas of the lungs. We addressed these challenges by formulating mRNA LNPs with SM-102, the clinically approved ionizable lipid in the Spikevax COVID-19 vaccine. Our lead candidate, B-1, had the highest mRNA expression in both a physiologically relevant air-liquid interface (ALI) human lung cell model and in healthy mice lungs upon aerosolization. Further, B-1 showed selective transfection in vivo of lung epithelial cells compared to immune cells and endothelial cells. These results show that the formulation can target therapeutically relevant cells in pulmonary diseases such as cystic fibrosis. Morphological studies of B-1 revealed differences in the surface structure compared to LNPs with lower transfection efficiency. Importantly, the formulation maintained critical aerodynamic properties in simulated human airways upon next generation impaction. Finally, structure-function analysis of SM-102 revealed that small changes in the number of carbons can improve upon mRNA delivery in ALI human lung cells. Overall, our study expands the application of SM-102 and its analogs to aerosolized pulmonary delivery and identifies a potent lead candidate for future therapeutically active mRNA therapies.

Aerosol-Mediated Non-Viral Lung Gene Therapy: The Potential of Aminoglycoside-Based Cationic Liposomes

Aerosol lung gene therapy using non-viral delivery systems represents a credible therapeutic strategy for chronic respiratory diseases, such as cystic fibrosis (CF). Progress in CF clinical setting using the lipidic formulation GL67A has demonstrated the relevance of such a strategy while emphasizing the need for more potent gene transfer agents. In recent years, many novel non-viral gene delivery vehicles were proposed as potential alternatives to GL67 cationic lipid. However, they were usually evaluated using procedures difficult or even impossible to implement in clinical practice. In this study, a clinically-relevant administration protocol via aerosol in murine lungs was used to conduct a comparative study with GL67A. Diverse lipidic compounds were used to prepare a series of formulations inspired by the composition of GL67A. While some of these formulations were ineffective at transfecting murine lungs, others demonstrated modest-to-very-efficient activities and a series of structure-activity relationships were unveiled. Lipidic aminoglycoside derivative-based formulations were found to be at least as efficient as GL67A following aerosol delivery of a luciferase-encoding plasmid DNA. A single aerosol treatment with one such formulation was found to mediate long-term lung transgene expression, exceeding half the animal's lifetime. This study clearly supports the potential of aminoglycoside-based cationic lipids as potent GL67-alternative scaffolds for further enhanced aerosol non-viral lung gene therapy for diseases such as CF.

How Far Are Non-Viral Vectors to Come of Age and Reach Clinical Translation in Gene Therapy?

Efficient delivery of genetic material into cells is a critical process to translate gene therapy into clinical practice. In this sense, the increased knowledge acquired during past years in the molecular biology and nanotechnology fields has contributed to the development of different kinds of non-viral vector systems as a promising alternative to virus-based gene delivery counterparts. Consequently, the development of non-viral vectors has gained attention, and nowadays, gene delivery mediated by these systems is considered as the cornerstone of modern gene therapy due to relevant advantages such as low toxicity, poor immunogenicity and high packing capacity. However, despite these relevant advantages, non-viral vectors have been poorly translated into clinical success. This review addresses some critical issues that need to be considered for clinical practice application of non-viral vectors in mainstream medicine, such as efficiency, biocompatibility, long-lasting effect, route of administration, design of experimental condition or commercialization process. In addition, potential strategies for overcoming main hurdles are also addressed. Overall, this review aims to raise awareness among the scientific community and help researchers gain knowledge in the design of safe and efficient non-viral gene delivery systems for clinical applications to progress in the gene therapy field.

Inhalation delivery technology for genome-editing of respiratory diseases

The clustered regulatory interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) system has significant therapeutic potentials for lung congenital diseases such as cystic fibrosis, as well as other pulmonary disorders like lung cancer and obstructive diseases. Local administration of CRISPR/Cas9 therapeutics through inhalation can achieve high drug concentration and minimise systemic exposure. While the field is advancing with better understanding on the biological functions achieved by CRISPR/Cas9 systems, the lack of progress in inhalation formulation and delivery of the molecule may impede their clinical translation efficiently. This forward-looking review discussed the current status of formulations and delivery for inhalation of relevant biologics such as genes (plasmids and mRNAs) and proteins, emphasising on their design strategies and preparation methods. By adapting and optimising formulation strategies used for genes and proteins, we envisage that development of inhalable CRISPR/Cas9 liquid or powder formulations for inhalation administration can potentially be fast-tracked in near future.

Nanoapproaches to Modifying Epigenetics of Epithelial Mesenchymal Transition for Treatment of Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronically progressive interstitial lung that affects over 3 M people worldwide and rising in incidence. With a median survival of 2-3 years, IPF is consequently associated with high morbidity, mortality, and healthcare burden. Although two antifibrotic therapies, pirfenidone and nintedanib, are approved for human use, these agents reduce the rate of decline of pulmonary function but are not curative and do not reverse established fibrosis. In this review, we discuss the prevailing epithelial injury hypothesis, wherein pathogenic airway epithelial cell-state changes known as Epithelial Mesenchymal Transition (EMT) promotes the expansion of myofibroblast populations. Myofibroblasts are principal components of extracellular matrix production that result in airspace loss and mortality. We review the epigenetic transition driving EMT, a process produced by changes in histone acetylation regulating mesenchymal gene expression programs. This mechanistic work has focused on the central role of bromodomain-containing protein 4 in mediating EMT and myofibroblast transition and initial preclinical work has provided evidence of efficacy. As nanomedicine presents a promising approach to enhancing the efficacy of such anti-IPF agents, we then focus on the state of nanomedicine formulations for inhalable delivery in the treatment of pulmonary diseases, including liposomes, polymeric nanoparticles (NPs), inorganic NPs, and exosomes. These nanoscale agents potentially provide unique properties to existing pulmonary therapeutics, including controlled release, reduced systemic toxicity, and combination delivery. NP-based approaches for pulmonary delivery thus offer substantial promise to modify epigenetic regulators of EMT and advance treatments for IPF.

A helper-dependent adenoviral vector rescues CFTR to wild-type functional levels in cystic fibrosis epithelial cells harbouring class I mutations

Cystic fibrosis (CF) is a genetic disorder affecting multiple organs, including the pancreas, hepatobiliary system and reproductive organs; however, lung disease is responsible for the majority of morbidity and mortality. Management of CF involves CF transmembrane conductance regulator (CFTR) modulator agents including corrector drugs to augment cellular trafficking of mutant CFTR as well as potentiators that open defective CFTR channels. These therapies are poised to help most individuals with CF, with the notable exception of individuals with class I mutations where full-length CFTR protein is not produced. For these mutations, gene replacement has been suggested as a potential solution.In this work, we used a helper-dependent adenoviral vector (HD-CFTR) to express CFTR in nasal epithelial cell cultures derived from CF subjects with class I CFTR mutations.CFTR function was significantly restored in CF cells by HD-CFTR and reached healthy control functional levels as detected by Ussing chamber and membrane potential (FLIPR) assay. A dose-response relationship was observed between the amount of vector used and subsequent functional outcomes; small amounts of HD-CFTR were sufficient to correct CFTR function. At higher doses, HD-CFTR did not increase CFTR function in healthy control cells above baseline values. This latter observation allowed us to use this vector to benchmark in vitro efficacy testing of CFTR-modulator drugs.In summary, we demonstrate the potential for HD-CFTR to inform in vitro testing and to restore CFTR function to healthy control levels in airway cells with class I or CFTR nonsense mutations.

Prolonged distribution of aerosolized PEGylated liposomes in the lungs of mice with bleomycin-induced pulmonary fibrosis

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is a progressive and chronic lung disease characterized by abnormal remodeling of the lung parenchyma with subsequent scarring of the alveolar structure. In this study, we examined the distribution characteristics of aerosolized polyethylene glycol (PEG)ylated liposomes in the lungs of mice with bleomycin-induced pulmonary fibrosis.

SIGNIFICANCE

The present study details the utility of aerosolized PEGylated liposomes for improving intrapulmonary pharmacokinetics in fibrotic lungs.

METHODS

Aerosolized PEGylated liposomes were administered to fibrotic mouse lungs using a MicroSprayer. Intrapulmonary pharmacokinetics was evaluated via in vivo imaging, measurement of liposome concentrations in bronchoalveolar lavage fluid (BALF) and alveolar macrophages (AMs), and observation of lung tissue sections. In addition, in vitro accumulation experiments using WI-38, A549, and RAW264.7 cells were performed.

RESULTS

The decrease of the fluorescence intensity of the PEGylated liposomes was slower than that of the non-modified liposomes. Compared with the non-modified liposomes, the PEGylated liposomes were determined higher in BALF, whereas those in the AMs were lower. Both PEGylated and non-modified liposomes were widely dispersed in fibrotic regions in tissue sections. No difference in accumulation in WI-38 and A549 cells was noted between PEGylated and non-modified liposomes, whereas the PEGylated liposomes exhibited lower intracellular accumulation than non-modified liposomes in RAW264.7 cells.

CONCLUSION

Aerosolized drug delivery systems using PEGylated liposomes exhibited prolonged distribution in both healthy and fibrotic mouse lungs. PEGylated liposomes were determined to be efficient drug delivery systems for anti-fibrotic agents targeting lung fibroblasts and alveolar epithelial cells for optimizing the treatment of IPF.

Nucleic Acid-Based Approaches for Tumor Therapy

Within the last decade, the introduction of checkpoint inhibitors proposed to boost the patients' anti-tumor immune response has proven the efficacy of immunotherapeutic approaches for tumor therapy. Furthermore, especially in the context of the development of biocompatible, cell type targeting nano-carriers, nucleic acid-based drugs aimed to initiate and to enhance anti-tumor responses have come of age. This review intends to provide a comprehensive overview of the current state of the therapeutic use of nucleic acids for cancer treatment on various levels, comprising (i) mRNA and DNA-based vaccines to be expressed by antigen presenting cells evoking sustained anti-tumor T cell responses, (ii) molecular adjuvants, (iii) strategies to inhibit/reprogram tumor-induced regulatory immune cells e.g., by RNA interference (RNAi), (iv) genetically tailored T cells and natural killer cells to directly recognize tumor antigens, and (v) killing of tumor cells, and reprograming of constituents of the tumor microenvironment by gene transfer and RNAi. Aside from further improvements of individual nucleic acid-based drugs, the major perspective for successful cancer therapy will be combination treatments employing conventional regimens as well as immunotherapeutics like checkpoint inhibitors and nucleic acid-based drugs, each acting on several levels to adequately counter-act tumor immune evasion.

Cystic Fibrosis: Overview of the Current Development Trends and Innovative Therapeutic Strategies

Cystic Fibrosis (CF), an autosomal recessive genetic disease, is caused by a mutation in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This mutation reduces the release of chloride ions (Cl-) in epithelial tissues, and hyperactivates the epithelial sodium channels (ENaC) which aid in the absorption of sodium ions (Na+). Consequently, the mucus becomes dehydrated and thickened, making it a suitable medium for microbial growth. CF causes several chronic lung complications like thickened mucus, bacterial infection and inflammation, progressive loss of lung function, and ultimately, death. Until recently, the standard of clinical care in CF treatment had focused on preventing and treating the disease complications. In this review, we have summarized the current knowledge on CF pathogenesis and provided an outlook on the current therapeutic approaches relevant to CF (i.e., CFTR modulators and ENaC inhibitors). The enormous potential in targeting bacterial biofilms using antibiofilm peptides, and the innovative therapeutic strategies in using the CRISPR/Cas approach as a gene-editing tool to repair the CFTR mutation have been reviewed. Finally, we have discussed the wide range of drug delivery systems available, particularly non-viral vectors, and the optimal properties of nanocarriers which are essential for successful drug delivery to the lungs.

Future Trends in Nebulized Therapies for Pulmonary Disease

Aerosol therapy is a key modality for drug delivery to the lungs of respiratory disease patients. Aerosol therapy improves therapeutic effects by directly targeting diseased lung regions for rapid onset of action, requiring smaller doses than oral or intravenous delivery and minimizing systemic side effects. In order to optimize treatment of critically ill patients, the efficacy of aerosol therapy depends on lung morphology, breathing patterns, aerosol droplet characteristics, disease, mechanical ventilation, pharmacokinetics, and the pharmacodynamics of cell-drug interactions. While aerosol characteristics are influenced by drug formulations and device mechanisms, most other factors are reliant on individual patient variables. This has led to increased efforts towards more personalized therapeutic approaches to optimize pulmonary drug delivery and improve selection of effective drug types for individual patients. Vibrating mesh nebulizers (VMN) are the dominant device in clinical trials involving mechanical ventilation and emerging drugs. In this review, we consider the use of VMN during mechanical ventilation in intensive care units. We aim to link VMN fundamentals to applications in mechanically ventilated patients and look to the future use of VMN in emerging personalized therapeutic drugs.

The Cystic Fibrosis-Like Airway Surface Layer Is not a Significant Barrier for Delivery of Eluforsen to Airway Epithelial Cells

Background: Eluforsen (previously known as QR-010) is a 33-mer antisense oligonucleotide under development for oral inhalation in cystic fibrosis (CF) patients with the delta F508 mutation. Previous work has shown that eluforsen restores CF transmembrane conductance regulator (CFTR) function in vitro and in vivo. To be effective, eluforsen has first to reach its primary target, the lung epithelial cells. Therefore, it has to diffuse through the CF airway surface layer (ASL), which in CF is characterized by the presence of thick and viscous mucus, impaired mucociliary clearance, and persistent infections. The goal of this study was to assess delivery of eluforsen through CF-like ASL. Methods and Results: First, air-liquid interface studies with cultured primary airway epithelial cells revealed that eluforsen rapidly diffuses through CF-like mucus at clinically relevant doses when nebulized once or repeatedly, over a range of testing doses. Furthermore, eluforsen concentrations remained stable in CF patient sputum for at least 48 hours, and eluforsen remained intact in the presence of various inhaled CF medications for at least 24 hours. When testing biodistribution of eluforsen after orotracheal administration in vivo, no differences in lung, liver, trachea, and kidney eluforsen concentration were observed between mice with a CF-like lung phenotype (ENaC-overexpressing mice) and control wild-type (WT) littermates. Also, eluforsen was visualized in the airway epithelial cell layer of CF-like muco-obstructed mice and WT littermates. Finally, studies of eluforsen uptake and binding to bacteria prevalent in CF lungs, and diffusion through bacterial biofilms showed that eluforsen was stable and not absorbed by, or bound to bacteria. In addition, eluforsen was found to be able to penetrate Pseudomonas aeruginosa biofilms. Conclusions: The thickened and concentrated CF ASL does not constitute a significant barrier for delivery of eluforsen, and feasibility of oral inhalation of eluforsen is supported by these data.

Tetrafunctional Block Copolymers Promote Lung Gene Transfer in Newborn Piglets

Tetrafunctional block copolymers are molecules capable of complexing DNA. Although ineffective in vitro, studies in mice have shown that the tetrafunctional block copolymer 704 is a more efficient lung gene transfer agent than the cationic liposome GL67A, previously used in a phase II clinical trial in cystic fibrosis patients. In the present study, we compared the gene transfer capacity of the 704-DNA formulation and a cationic liposome-DNA formulation equivalent to GL67A in a larger-animal model, the newborn piglet. Our results indicate an efficacy of the 704-DNA formulation well above one order of magnitude higher than that of the cationic liposome-DNA formulation, with no elevated levels of interleukin-6 (IL-6), taken as a marker of inflammation. Transgene expression was heterogeneous within lung lobes, with expression levels that were below the detection threshold in some samples, while high in other samples. This heterogeneity is likely to be due to the bolus injection procedure as well as to the small volume of injection. The present study highlights the potential of tetrafunctional block copolymers as non-viral vectors for lung gene therapy.

Understanding Gene Therapy in Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) and its complications remain lifethreatening conditions for critically ill patients. The present therapeutic strategies such as prone positioning ventilation strategies, nitric oxide inhalation, restrictive intravenous fluid management, and extracorporeal membrane oxygenation (ECMO) do not contribute much to improving the mortality of ARDS. The advanced understanding of the pathophysiology of acute respiratory distress syndrome suggests that gene-based therapy may be an innovative method for this disease. Many scientists have made beneficial attempts to regulate the immune response genes of ARDS, maintain the normal functions of alveolar epithelial cells and endothelial cells, and inhibit the fibrosis and proliferation of ARDS. Limitations to effective pulmonary gene therapy still exist, including the security of viral vectors and the pulmonary defense mechanisms against inhaled particles. Here, we summarize and review the mechanism of gene therapy for acute respiratory distress syndrome and its application.

A Comparison between Two Pathophysiologically Different yet Microbiologically Similar Lung Diseases: Cystic Fibrosis and Chronic Obstructive Pulmonary Disease

Cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) are chronic pulmonary diseases that affect ~70,000 and 251 million individuals worldwide, respectively. Although these two diseases have distinctly different pathophysiologies, both cause chronic respiratory insufficiency that erodes quality of life and causes significant morbidity and eventually death. In both CF and COPD, the respiratory microbiome plays a major contributing role in disease progression and morbidity. Pulmonary pathogens can differ dramatically during various stages of each disease and frequently cause acute worsening of lung function due to disease exacerbation. Despite some similarities, outcome and timing/type of exacerbation can also be quite different between CF and COPD. Given these clinical distinctions, both patients and physicians should be aware of emerging therapeutic options currently being offered or in development for the treatment of lung infections in individuals with CF and COPD. Although interventions are available that prolong life and mitigate morbidity, neither disorder is curable. Both acute and chronic pulmonary infections contribute to an inexorable downward course and may trigger exacerbations, culminating in loss of lung function or respiratory failure. Knowledge of the pulmonary pathogens causing these infections, their clinical presentation, consequences, and management are, therefore, critical. In this review, we compare and contrast CF and COPD, including underlying causes, general outcomes, features of the lung microbiome, and potential treatment strategies.

DNA Vaccines-How Far From Clinical Use?

Two decades ago successful transfection of antigen presenting cells (APC) in vivo was demonstrated which resulted in the induction of primary adaptive immune responses. Due to the good biocompatibility of plasmid DNA, their cost-efficient production and long shelf life, many researchers aimed to develop DNA vaccine-based immunotherapeutic strategies for treatment of infections and cancer, but also autoimmune diseases and allergies. This review aims to summarize our current knowledge on the course of action of DNA vaccines, and which factors are responsible for the poor immunogenicity in human so far. Important optimization steps that improve DNA transfection efficiency comprise the introduction of DNA-complexing nano-carriers aimed to prevent extracellular DNA degradation, enabling APC targeting, and enhanced endo/lysosomal escape of DNA. Attachment of virus-derived nuclear localization sequences facilitates nuclear entry of DNA. Improvements in DNA vaccine design include the use of APC-specific promotors for transcriptional targeting, the arrangement of multiple antigen sequences, the co-delivery of molecular adjuvants to prevent tolerance induction, and strategies to circumvent potential inhibitory effects of the vector backbone. Successful clinical use of DNA vaccines may require combined employment of all of these parameters, and combination treatment with additional drugs.

P311, Friend, or Foe of Tissue Fibrosis?

P311 was first identified by the group of Studler et al. (1993) in the developing brain. In healthy, but mainly in pathological tissues, P311 is implicated in cell migration and proliferation. Furthermore, evidence in models of tissue fibrosis points to the colocalization with and the stimulation of transforming growth factor β1 by P311. This review provides a comprehensive overview on P311 and discusses its potential as an anti-fibrotic target.

Lessons learned from lung and liver in-vivo gene therapy: implications for the future

INTRODUCTION

Ex-vivo gene therapy has had significant clinical impact over the last couple of years and in-vivo gene therapy products are being approved for clinical use. Gene therapy and gene editing approaches have huge potential to treat genetic disease and chronic illness.

AREAS COVERED

This article provides a review of in-vivo approaches for gene therapy in the lung and liver, exploiting non-viral and viral vectors with varying serotypes and pseudotypes to target-specific cells. Antibody responses inhibiting viral vectors continue to constrain effective repeat administration. Lessons learned from ex-vivo gene therapy and genome editing are also discussed.

EXPERT OPINION

The fields of lung and liver in-vivo gene therapy are thriving and a comparison highlights obstacles and opportunities for both. Overcoming immunological issues associated with repeated administration of viral vectors remains a key challenge. The addition of targeted small molecules in combination with viral vectors may offer one solution. A substantial bottleneck to the widespread adoption of in-vivo gene therapy is how to ensure sufficient capacity for clinical-grade vector production. In the future, the exploitation of gene editing approaches for in-vivo disease treatment may facilitate the resurgence of non-viral gene transfer approaches, which tend to be eclipsed by more efficient viral vectors.

Generation of High Concentrations of Respirable Solid-Phase Aerosols from Viscous Fluids

High outputs of respirable solid-phase aerosols were generated from viscous solutions or suspensions of low and high molecular weight polyvinylprrolidone (PVP) solutions, 10% (w/v) albumin and, gamma-globulin solutions as well as 10.3% (w/v) surfactant suspensions. A central fluid flow was aerosolized by coaxial converging compressed air. The water was evaporated from the droplets using warm dilution air and infrared radiation. The resulting aerosol particles were concentrated using a virtual impactor. The aerosols were generated at fluid flow rates between 1 and 3 ml/min and delivered at a flow rate of 44 l/min as 2.6 - 3.6 μm MMAD aerosols with geometric standard deviations between 1.5 and 2. Increases in viscosity over the range of 4 to 39 cSt caused a modest increase in MMAD. Increases in aerosol exit orifice diameter was associated with a decrease in aerosol diameter. Increases in compressed air pressure caused a decrease in aerosol diameter. Increases in fluid flow rate resulted modest increases in MMAD together with proportional increases in output mass. Aerosolizing 10% 8 kDa PVP at 3 ml/min resulted in the delivery of 193 mg/min of PVP at 64% efficiency enabling 1.2 g to be collected in 7 min. Aerosolizing 10.3% surfactant suspensions at 3 ml/min resulted in the delivery of up to 163 mg/min with 59% efficiency. The surface tension of the surfactant was not changed by these processes. SEM showed dimpled particles of PVP, albumin and gamma globulin indicating that their aerodynamic diameter was less than their morphometric diameter.

Enhancement of lung gene delivery after aerosol: a new strategy using non-viral complexes with antibacterial properties

The pathophysiology of obstructive pulmonary diseases, such as cystic fibrosis (CF), leads to the development of chronic infections in the respiratory tract. Thus, the symptomatic management of the disease requires, in particular, repetitive antibiotherapy. Besides these antibacterial treatments, certain pathologies, such as CF or chronic obstructive pulmonary disease (COPD), require the intake of many drugs. This simultaneous absorption may lead to undesirable drug interactions. For example, Orkambi® (lumacaftor/Ivacaftor, Vertex), a pharmacological drug employed to treat F508del patients, cannot be used with antibiotics such as rifampicin or rifabutin (rifamycin family) which are necessary to treat Mycobacteriaceae. As far as gene therapy is concerned, bacteria and/or biofilm in the airways present an additional barrier for gene transfer. Thus, aerosol administration of nanoparticles have to overcome many obstacles before allowing cellular penetration of therapeutic compounds. This review focusses on the development of aerosol formulations adapted to the respiratory tract and its multiple barriers. Then, formulations that are currently used in clinical applications are summarized depending on the active molecule delivered. Finally, we focus on new therapeutic approaches to reduce possible drug interactions by transferring the antibacterial activity to the nanocarrier while ensuring the transfection efficiency.

Inhaled gene delivery: a formulation and delivery approach

INTRODUCTION

Gene therapy is a potential alternative to treat a number of diseases. Different hurdles are associated with aerosol gene delivery due to the susceptibility of plasmid DNA (pDNA) structure to be degraded during the aerosolization process. Different strategies have been investigated in order to protect and efficiently deliver pDNA to the lungs using non-viral vectors. To date, no successful therapy involving non-viral vectors has been marketed, highlighting the need for further investigation in this field. Areas covered: This review is focused on the formulation and delivery of DNA to the lungs, using non-viral vectors. Aerosol gene formulations are divided according to the current delivery systems for the lung: nebulizers, dry powder inhalers and pressurized metered dose inhalers; highlighting its benefits, challenges and potential application. Expert opinion: Successful aerosol delivery is achieved when the supercoiled DNA structure is protected during aerosolization. A formulation strategy or compounds that can protect, stabilize and efficiently transfect DNA into the cells is desired in order to produce an effective, low-cost and safe formulation. Nebulizers and dry powder inhalers are the most promising approaches to be used for aerosol delivery, due to the lower shear forces involved. In this context it is also important to highlight the importance of considering the 'pDNA-formulation-device system' as an integral part of the formulation development for a successful nucleic acid delivery.

The function and performance of aqueous aerosol devices for inhalation therapy

OBJECTIVES

In this review paper, we explore the interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations for several types of devices, namely jet, ultrasonic and vibrating-mesh nebulizers; colliding and extruded jets; electrohydrodynamic mechanism; surface acoustic wave microfluidic atomization; and capillary aerosol generation.

KEY FINDINGS

Nebulization is the transformation of bulk liquids into droplets. For inhalation therapy, nebulizers are widely used to aerosolize aqueous systems, such as solutions and suspensions. The interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations plays a significant role in the performance of aerosol generation appropriate for pulmonary delivery. Certain types of nebulizers have consistently presented temperature increase during the nebulization event. Therefore, careful consideration should be given when evaluating thermo-labile drugs, such as protein therapeutics. We also present the general approaches for characterization of nebulizer formulations.

SUMMARY

In conclusion, the interplay between the dosage form (i.e. aqueous systems) and the specific type of device for aerosol generation determines the effectiveness of drug delivery in nebulization therapies, thus requiring extensive understanding and characterization.

New and emerging targeted therapies for cystic fibrosis

Cystic fibrosis (CF) is a monogenic autosomal recessive disorder that affects about 70,000 people worldwide. The clinical manifestations of the disease are caused by defects in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The discovery of the CFTR gene in 1989 has led to a sophisticated understanding of how thousands of mutations in the CFTR gene affect the structure and function of the CFTR protein. Much progress has been made over the past decade with the development of orally bioavailable small molecule drugs that target defective CFTR proteins caused by specific mutations. Furthermore, there is considerable optimism about the prospect of gene replacement or editing therapies to correct all mutations in cystic fibrosis. The recent approvals of ivacaftor and lumacaftor represent the genesis of a new era of precision medicine in the treatment of this condition. These drugs are having a positive impact on the lives of people with cystic fibrosis and are potentially disease modifying. This review provides an update on advances in our understanding of the structure and function of the CFTR, with a focus on state of the art targeted drugs that are in development.

Cystic Fibrosis Gene Therapy in the UK and Elsewhere

The cystic fibrosis transmembrane conductance regulator (CFTR) gene was identified in 1989. This opened the door for the development of cystic fibrosis (CF) gene therapy, which has been actively pursued for the last 20 years. Although 26 clinical trials involving approximately 450 patients have been carried out, the vast majority of these trials were short and included small numbers of patients; they were not designed to assess clinical benefit, but to establish safety and proof-of-concept for gene transfer using molecular end points such as the detection of recombinant mRNA or correction of the ion transport defect. The only currently published trial designed and powered to assess clinical efficacy (defined as improvement in lung function) administered AAV2-CFTR to the lungs of patients with CF. The U.K. Cystic Fibrosis Gene Therapy Consortium completed, in the autumn of 2014, the first nonviral gene therapy trial designed to answer whether repeated nonviral gene transfer (12 doses over 12 months) can lead to clinical benefit. The demonstration that the molecular defect in CFTR can be corrected with small-molecule drugs, and the success of gene therapy in other monogenic diseases, is boosting interest in CF gene therapy. Developments are discussed here.

Nebulisation of IVT mRNA Complexes for Intrapulmonary Administration

During the last years the potential role of in vitro transcribed (IVT) mRNA as a vehicle to deliver genetic information has come into focus. IVT mRNA could be used for anti-cancer therapies, vaccination purposes, generation of pluripotent stem cells and also for genome engineering or protein replacement. However, the administration of IVT mRNA into the target organ is still challenging. The lung with its large surface area is not only of interest for delivery of genetic information for treatment of e.g. for cystic fibrosis or alpha-1-antitrypsin deficiency, but also for vaccination purposes. Administration of IVT mRNA to the lung can be performed by direct intratracheal instillation or by aerosol inhalation/nebulisation. The latter approach shows a non-invasive tool, although it is not known, if IVT mRNA is resistant during the process of nebulisation. Therefore, we investigated the transfection efficiency of non-nebulised and nebulised IVT mRNA polyplexes and lipoplexes in human bronchial epithelial cells (16HBE). A slight reduction in transfection efficiency was observed for lipoplexes (Lipofectamine 2000) in the nebulised part compared to the non-nebulised which can be overcome by increasing the amount of Lipofectamine. However, Lipofectamine was more than three times more efficient in transfecting 16HBE than DMRIE and linear PEI performed almost 10 times better than its branched derivative. By contrast, the nebulisation process did not affect the cationic polymer complexes. Furthermore, aerosolisation of IVT mRNA complexes did neither affect the protein duration nor the toxicity of the cationic complexes. Taken together, these data show that aerosolisation of cationic IVT mRNA complexes constitute a potentially powerful means to transfect cells in the lung with the purpose of protein replacement for genetic diseases such as cystic fibrosis or alpha-1-antitrypsin deficiency or for infectious disease vaccines, while bringing along the advantages of IVT mRNA as compared to pDNA as transfection agent.

Nanocomplexes for gene therapy of respiratory diseases: Targeting and overcoming the mucus barrier

Gene therapy, i.e. the delivery and expression of therapeutic genes, holds great promise for congenital and acquired respiratory diseases. Non-viral vectors are less toxic and immunogenic than viral vectors, although they are characterized by lower efficiency. However, they have to overcome many barriers, including inflammatory and immune mediators and cells. The respiratory and airway epithelial cells, the main target of these vectors, are coated with a layer of mucus, which hampers the effective reaching of gene therapy vectors carrying either plasmid DNA or small interfering RNA. This barrier is thicker in many lung diseases, such as cystic fibrosis. This review summarizes the most important advancements in the field of non-viral vectors that have been achieved with the use of nanoparticulate (NP) systems, composed either of polymers or lipids, in the lung gene delivery. In particular, different strategies of targeting of respiratory and airway lung cells will be described. Then, we will focus on the two approaches that attempt to overcome the mucus barrier: coating of the nanoparticulate system with poly(ethylene glycol) and treatment with mucolytics. Our conclusions are: 1) Ligand and physical targeting can direct therapeutic gene expression in specific cell types in the respiratory tract; 2) Mucopenetrating NPs are endowed with promising features to be useful in treating respiratory diseases and should be now advanced in pre-clinical trials. Finally, we discuss the development of such polymer- and lipid-based NPs in the context of in vitro and in vivo disease models, such as lung cancer, as well as in clinical trials.

Repeated nebulisation of non-viral CFTR gene therapy in patients with cystic fibrosis: a randomised, double-blind, placebo-controlled, phase 2b trial

Background

Lung delivery of plasmid DNA encoding the CFTR gene complexed with a cationic liposome is a potential treatment option for patients with cystic fibrosis. We aimed to assess the efficacy of non-viral CFTR gene therapy in patients with cystic fibrosis.

Methods

We did this randomised, double-blind, placebo-controlled, phase 2b trial in two cystic fibrosis centres with patients recruited from 18 sites in the UK. Patients (aged ≥12 years) with a forced expiratory volume in 1 s (FEV₁) of 50–90% predicted and any combination of CFTR mutations, were randomly assigned, via a computer-based randomisation system, to receive 5 mL of either nebulised pGM169/GL67A gene–liposome complex or 0·9% saline (placebo) every 28 days (plus or minus 5 days) for 1 year. Randomisation was stratified by % predicted FEV₁ (<70 vs ≥70%), age (<18 vs ≥18 years), inclusion in the mechanistic substudy, and dosing site (London or Edinburgh). Participants and investigators were masked to treatment allocation. The primary endpoint was the relative change in % predicted FEV₁. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01621867.

Findings

Between June 12, 2012, and June 24, 2013, we randomly assigned 140 patients to receive placebo (n=62) or pGM169/GL67A (n=78), of whom 116 (83%) patients comprised the per-protocol population. We noted a significant, albeit modest, treatment effect in the pGM169/GL67A group versus placebo at 12 months' follow-up (3·7%, 95% CI 0·1–7·3; p=0·046). This outcome was associated with a stabilisation of lung function in the pGM169/GL67A group compared with a decline in the placebo group. We recorded no significant difference in treatment-attributable adverse events between groups.

Interpretation

Monthly application of the pGM169/GL67A gene therapy formulation was associated with a significant, albeit modest, benefit in FEV₁ compared with placebo at 1 year, indicating a stabilisation of lung function in the treatment group. Further improvements in efficacy and consistency of response to the current formulation are needed before gene therapy is suitable for clinical care; however, our findings should also encourage the rapid introduction of more potent gene transfer vectors into early phase trials.

Funding

Medical Research Council/National Institute for Health Research Efficacy and Mechanism Evaluation Programme.

Novel therapeutic approaches for pulmonary arterial hypertension: Unique molecular targets to site-specific drug delivery

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disorder characterized by increased blood pressure in the small arterioles supplying blood to lungs for oxygenation. Advances in understanding of molecular and cellular biology techniques have led to the findings that PAH is indeed a cascade of diseases exploiting multi-faceted complex pathophysiology, with cellular proliferation and vascular remodeling being the key pathogenic events along with several cellular pathways involved. While current therapies for PAH do provide for amelioration of disease symptoms and acute survival benefits, their full therapeutic potential is hindered by patient incompliance and off-target side effects. To overcome the issues related with current therapy and to devise a more selective therapy, various novel pathways are being investigated for PAH treatment. In addition, inability to deliver anti-PAH drugs to the disease site i.e., distal pulmonary arterioles has been one of the major challenges in achieving improved patient outcomes and improved therapeutic efficacy. Several novel carriers have been explored to increase the selectivity of currently approved anti-PAH drugs and to act as suitable carriers for the delivery of investigational drugs. In the present review, we have discussed potential of various novel molecular pathways/targets including RhoA/Rho kinase, tyrosine kinase, endothelial progenitor cells, vasoactive intestinal peptide, and miRNA in PAH therapeutics. We have also discussed various techniques for site-specific drug delivery of anti-PAH therapeutics so as to improve the efficacy of approved and investigational drugs. This review will provide gainful insights into current advances in PAH therapeutics with an emphasis on site-specific drug payload delivery.

Inhalation drug delivery devices: technology update

The pulmonary route of administration has proven to be effective in local and systemic delivery of miscellaneous drugs and biopharmaceuticals to treat pulmonary and non-pulmonary diseases. A successful pulmonary administration requires a harmonic interaction between the drug formulation, the inhaler device, and the patient. However, the biggest single problem that accounts for the lack of desired effect or adverse outcomes is the incorrect use of the device due to lack of training in how to use the device or how to coordinate actuation and aerosol inhalation. This review summarizes the structural and mechanical features of aerosol delivery devices with respect to mechanisms of aerosol generation, their use with different formulations, and their advantages and limitations. A technological update of the current state-of-the-art designs proposed to overcome current challenges of existing devices is also provided.

Gene delivery potential of biofunctional carbonate apatite nanoparticles in lungs

Existing nonviral gene delivery systems to lungs are inefficient and associated with dose limiting toxicity in mammalian cells. Therefore, carbonate apatite (CO₃Ap) nanoparticles were examined as an alternative strategy for effective gene delivery to the lungs. This study aimed to (1) assess the gene delivery efficiency of CO₃Ap in vitro and in mouse lungs, (2) evaluate the cytotoxicity effect of CO₃Ap/pDNA in vitro, and (3) characterize the CO₃Ap/pDNA complex formulations. A significantly high level of reporter gene expression was detected from the lung cell line transfected with CO₃Ap/pDNA complex prepared in both serum and serum-free medium. Cytotoxicity analysis revealed that the percentage of the viable cells treated with CO₃Ap to be almost similar to the untreated cells. Characterization analyses showed that the CO₃Ap/pDNA complexes are in a nanometer range with aggregated spherical structures and tended to be more negatively charged. In the lung of mice, highest level of transgene expression was observed when CO₃Ap (8 μL) was complexed with 40 μg of pDNA at day 1 after administration. Although massive reduction of gene expression was seen beyond day 1 post administration, the level of expression remained significant throughout the study period.