Positive Effect of Liposomal Amikacin for Inhalation on Mycobacterium abcessus in Cystic Fibrosis Patients

An evolving perspective on novel modified release drug delivery systems for inhalational therapy

INTRODUCTION

Drugs delivered via the lungs are predominantly used to treat various respiratory disorders, including asthma, chronic obstructive pulmonary diseases, respiratory tract infections and lung cancers, and pulmonary vascular diseases such as pulmonary hypertension. To treat respiratory diseases, targeted, modified or controlled release inhalation formulations are desirable for improved patient compliance and superior therapeutic outcome.

AREAS COVERED

This review summarizes the important factors that have an impact on the inhalable modified release formulation approaches with a focus toward various formulation strategies, including dissolution rate-controlled systems, drug complexes, site-specific delivery, drug-polymer conjugates, and drug-polymer matrix systems, lipid matrix particles, nanosystems, and formulations that can bypass clearance via mucociliary system and alveolar macrophages.

EXPERT OPINION

Inhaled modified release formulations can potentially reduce dosing frequency by extending drug's residence time in the lungs. However, inhalable modified or controlled release drug delivery systems remain unexplored and underdeveloped from the commercialization perspective. This review paper addresses the current state-of-the-art of inhaled controlled release formulations, elaborates on the avenues for developing newer technologies for formulating various drugs with tailored release profiles after inhalational delivery and explains the challenges associated with translational feasibility of modified release inhalable formulations.

Mycobacterium biofilms

The genus Mycobacterium includes some of the deadliest pathogens of History (Mycobacterium tuberculosis, Mycobacterium leprae), but most of the species within the genus are environmental microorganisms. Because some of these nontuberculous mycobacteria (NTM) species can be human pathogens, the study of these mycobacterial biofilms has increased during the last decades, and the interest in this issue increased as well as the growing number of patients with diseases caused by NTM. Different molecular mechanisms have been described, being especially well known the importance of glycopeptidolipids. Moreover, the knowledge of the extracellular matrix has shown important differences with other microorganisms, especially because of the presence of lipidic molecules as a key component of this structure. The clinical importance of mycobacterial biofilms has been described for many chronic diseases, especially lung diseases and implant-related ones, both in vitro and in vivo, and even in patients. Moreover, the biofilm-producing capacity has been proven also in M. tuberculosis, while its importance is not well understood. Biofilm studies have also shown the increasing resistance of mycobacteria in sessile form, and the importance of this resistance in the management of the patients is beyond doubt, being surgery necessary in some cases to cure the patients. Diagnosis of mycobacterial diseases is still based on culture-based techniques designed for the detection of M. tuberculosis. Molecular biology-based methods are also broadly used but again designed for tuberculosis diagnosis. Antimicrobial susceptibility testing is also well developed for tuberculosis, but only some species of NTM have standardized techniques for this purpose. New tools or approaches are necessary to treat these patients, whose importance is increasing, as the number of potential hosts is also increasing throughout the world.

Mechanistic insights into nanoparticle surface-bacterial membrane interactions in overcoming antibiotic resistance

Antimicrobial Resistance (AMR) raises a serious concern as it contributes to the global mortality by 5 million deaths per year. The overall impact pertaining to significant membrane changes, through broad spectrum drugs have rendered the bacteria resistant over the years. The economic expenditure due to increasing drug resistance poses a global burden on healthcare community and must be dealt with immediate effect. Nanoparticles (NP) have demonstrated inherent therapeutic potential or can serve as nanocarriers of antibiotics against multidrug resistant (MDR) pathogens. These carriers can mask the antibiotics and help evade the resistance mechanism of the bacteria. The targeted delivery can be fine-tuned through surface functionalization of Nanocarriers using aptamers, antibodies etc. This review covers various molecular mechanisms acquired by resistant bacteria towards membrane modification. Mechanistic insight on 'NP surface-bacterial membrane' interactions are crucial in deciding the role of NP as therapeutic. Finally, we highlight the potential accessible membrane targets for designing smart surface-functionalized nanocarriers which can act as bacteria-targeted robots over the existing clinically available antibiotics. As the bacterial strains around us continue to evolve into resistant versions, nanomedicine can offer promising and alternative tools in overcoming AMR.

Microbiological profile, preclinical pharmacokinetics and efficacy of CRS0393, a novel antimycobacterial agent targeting MmpL3

The benzothiazole amide CRS0393 demonstrated excellent in vitro activity against nontuberculous mycobacteria (NTM), including M. abscessus isolates from cystic fibrosis (CF) patients, with minimum inhibitory concentrations (MICs) of ≤0.03-0.5 μg/mL. The essential transport protein MmpL3 was confirmed as the target via analysis of spontaneous resistant mutants and further biological profiling. In mouse pharmacokinetic studies, intratracheal instillation of a single dose of CRS0393 resulted in high concentrations of drug in epithelial lining fluid (ELF) and lung tissue, which remained above the M. abscessus MIC for at least 9 hours post-dose. This exposure resulted in a penetration ratio of 261 for ELF and 54 for lung tissue relative to plasma. CRS0393 showed good oral bioavailability, particularly when formulated in kolliphor oil, with a lung-to-plasma penetration ratio ranging from 0.5 to 4. CRS0393 demonstrated concentration-dependent reduction of intracellular M. abscessus in a THP-1 macrophage infection model. CRS0393 was well tolerated following intranasal administration (8 mg/kg) or oral dosing (25 mg/kg) once daily for 28 days in dexamethasone-treated C3HeB/FeJ mice. Efficacy against M. abscessus strain 103 was achieved via the intranasal route, while oral dosing will need further optimization. CRS0393 holds promise for development as a novel agent with broad antimycobacterial activity.

Liposomal amikacin and Mycobacterium abscessus: intimate interactions inside eukaryotic cells

BACKGROUND

Mycobacterium abscessus (Mabs), a rapidly growing Mycobacterium species, is considered an MDR organism. Among the standard antimicrobial multi-drug regimens against Mabs, amikacin is considered as one of the most effective. Parenteral amikacin, as a consequence of its inability to penetrate inside the cells, is only active against extracellular mycobacteria. The use of inhaled liposomal amikacin may yield improved intracellular efficacy by targeting Mabs inside the cells, while reducing its systemic toxicity.

OBJECTIVES

To evaluate the colocalization of an amikacin liposomal inhalation suspension (ALIS) with intracellular Mabs, and then to measure its intracellular anti-Mabs activity.

METHODS

We evaluated the colocalization of ALIS with Mabs in eukaryotic cells such as macrophages (THP-1 and J774.2) or pulmonary epithelial cells (BCi-NS1.1 and MucilAir), using a fluorescent ALIS and GFP-expressing Mabs, to test whether ALIS reaches intracellular Mabs. We then evaluated the intracellular anti-Mabs activity of ALIS inside macrophages using cfu and/or luminescence.

RESULTS

Using confocal microscopy, we demonstrated fluorescent ALIS and GFP-Mabs colocalization in macrophages and epithelial cells. We also showed that ALIS was active against intracellular Mabs at a concentration of 32 to 64 mg/L, at 3 and 5 days post-infection. Finally, ALIS intracellular activity was confirmed when tested against 53 clinical Mabs isolates, showing intracellular growth reduction for nearly 80% of the isolates.

CONCLUSIONS

Our experiments demonstrate the intracellular localization and intracellular contact between Mabs and ALIS, and antibacterial activity against intracellular Mabs, showing promise for its future use for Mabs pulmonary infections.

Calcium carbonate mineralization is essential for biofilm formation and lung colonization

Biofilms are differentiated microbial communities held together by an extracellular matrix. μCT X-ray revealed structured mineralized areas within biofilms of lung pathogens belonging to two distant phyla - the proteobacteria Pseudomonas aeruginosa and the actinobacteria Mycobacterium abscessus. Furthermore, calcium chelation inhibited the assembly of complex bacterial structures for both organisms with little to no effect on cell growth. The molecular mechanisms promoting calcite scaffold formation were surprisingly conserved between the two pathogens as biofilm development was similarly impaired by genetic and biochemical inhibition of calcium uptake and carbonate accumulation. Moreover, chemical inhibition and mutations targeting mineralization significantly reduced the attachment of P. aeruginosa to the lung, as well as the subsequent damage inflicted by biofilms to lung tissues, and restored their sensitivity to antibiotics. This work offers underexplored druggable targets for antibiotics to combat otherwise untreatable biofilm infections.

Chemical Advances in Therapeutic Application of Exosomes and Liposomes

Exosomes and liposomes are vesicular nanoparticles that can encapsulate functional cargo. The chemical similarities between naturally occurring exosomes and synthetic liposomes have accelerated the development of exosome mimetics as a therapeutic drug delivery platform under physiological and pathological environments. To maximise the applications of exosomes and liposomes in the clinical setting, it is essential to look into their basic chemical properties and utilise these characteristics to optimise the preparation, loading, modification and hybridisation. This review summarises the chemical and biological properties of both exosomal and liposomal systems as well as some of the challenges related to their production and application. This article concludes with a discussion on potential perspectives for the integration of exosomal and liposomal technologies in mapping better approaches for their biomedical use, especially in therapeutics.

ERS International Congress 2021: highlights from the Respiratory Infections Assembly

The European Respiratory Society Annual Congress 2021 took place virtually for the second year running due to the coronavirus pandemic. The congress programme featured more than 400 sessions and 3000 abstract presentations, covering the entire respiratory science and medicine field. In this article, Early Career Members of the Respiratory Infections Assembly summarise a selection of sessions across a broad range of topics, including presentations on bronchiectasis, non-tuberculosis mycobacteria, tuberculosis, cystic fibrosis and COVID-19.

The role of amikacin in the treatment of nontuberculous mycobacterial disease

Introduction: Guidelines recommend the use of amikacin in the treatment of nontuberculous mycobacterial (NTM) disease. The authors have evaluated the evidence for the position of amikacin in NTM disease treatment.Areas covered: The authors performed a literature search for original research on amikacin in NTM disease, including its mechanism of action, emergence of resistance, pre-clinical and clinical investigations.Expert opinion: Amikacin shows moderate in vitro activity against the clinically most relevant NTM species (M. avium complex and M. abscessus). It is synergistic with ethambutol, clofazimine, and macrolides and these combinations are effective in animal models. Liposomal encapsulation increases amikacin efficacy. Clinically, the recommended dose of 15 mg/kg intravenous amikacin does not lead to PK/PD target attainment in all patients and a positive impact on long-term treatment outcomes remains unproven in both M. avium complex and M. abscessus disease. Adding the amikacin liposome inhalation suspension did prove to be effective in short and long term in patients not responding to recommended treatment for M. avium complex pulmonary disease. Its optimal use in M. avium complex and M. abscessus pulmonary disease warrants further evaluation.

99m Tc-labeled antibiotics for infection diagnosis: Mechanism, action, and progress

Discovery of penicillin marked a turning point in the history of infection therapy which also led to the emergence of bacterial resistance. It is now 100 years to fight with ever-muted variants of pathogens by developing more and more antibiotics. Since 1987 to todate, no successful class of antibiotic was introduced; this three decade period is known as "the discovery void" period. While, the clinically approved antibiotics are gradually dying in front of bacterial resistance due to which bacterial infections are appearing leading cause of death and disability. Nuclear medicine imaging technique is the strongest modality to diagnose and follow-up of deep-seated and complicated infections. However, the selection of radiolabeled antimicrobial agents plays critical role in gaining sensitivity and specificity of the imaging results. This review comprises of two main sections; first section explains antibiotic targets, and second section explains the imaging efficacy of ^99m Tc-labeled antimicrobial agents against bacterial infection along with the emphasis on progress and update of ^99m Tc-labeled antibiotics as infection imaging probes. The review, in conclusion, could be an acceleration for radiopharmaceutical chemists for designing and developing ^99m Tc-labeled antimicrobial agents to improve infection imaging quality.

Resistant Tuberculosis: the Latest Advancements of Second-line Antibiotic Inhalation Products

Drug-resistant tuberculosis (TB) can be considered the man-made result of interrupted, erratic or inadequate TB therapy. As reported in WHO data, resistant Mycobacterium tuberculosis (Mtb) strains continue to constitute a public health crisis. Mtb is naturally able to survive host defence mechanisms and to resist most antibiotics currently available. Prolonged treatment regimens using the available first-line drugs give rise to poor patient compliance and a rapid evolution of strains resistant to rifampicin only or to both rifampicin and isoniazid (multi drug-resistant, MDR-TB). The accumulation of mutations may give rise to extensively drug-resistant strains (XDR-TB), i.e. strains with resistance also to fluoroquinolones and to the injectable aminoglycoside, which represent the second-line drugs. Direct lung delivery of anti-tubercular drugs, as an adjunct to conventional routes, provides high concentrations within the lungs, which are the intended target site of drug delivery, representing an interesting strategy to prevent or reduce the development of drug-resistant strains. The purpose of this paper is to describe and critically analyse the most recent and advanced results in the formulation development of WHO second-line drug inhalation products, with particular focus on dry powder formulation. Although some of these formulations have been developed for other lung infectious diseases (Pseudomonas aeruginosa, nontuberculous mycobacteria), they could be valuable to treat MDR-TB and XDR-TB.

Novel therapies for treatment of resistant and refractory nontuberculous mycobacterial infections in patients with cystic fibrosis

Respiratory infections caused by non-tuberculous mycobacteria (NTM) are a major cause of morbidity for patients living with cystic fibrosis (CF), as NTM pulmonary disease (NTM-PD) is challenging to both diagnose and eradicate. Despite the lengthy courses of the established regimens recommended by the Cystic Fibrosis Foundation (CFF) and European Cystic Fibrosis Society (ECFS) consensus guidelines, only about 50% to 60% of patients achieve culture conversion, and treatment regimens are often complicated by antibiotic resistance and toxicities. Since publication of the CFF/ECFS guidelines, several new or alternative antibiotic regimens have been described for patients with CF who have NTM-PD. These regimens offer new options for patients who do not clear NTM with standard therapies or cannot utilize the usual regimens due to toxicities or drug-drug interactions.

The role of cells and their products in respiratory drug delivery: the past, present, and future

INTRODUCTION

Cell-based delivery systems offer considerable promise as novel and innovative therapeutics to target the respiratory system. These systems consist of cells and/or their extracellular vesicles that deliver their contents, such as anti-microbial peptides, micro RNAs, and even mitochondria to the lung, exerting direct therapeutic effects.

AREAS COVERED

The purpose of this article is to critically review the status of cell-based therapies in the delivery of therapeutics to the lung, evaluate current progress, and elucidate key challenges to the further development of these novel approaches. An overview as to how these cells and/or their products may be modified to enhance efficacy is given. More complex delivery cell-based systems, including cells or vesicles that are genetically modified to (over)express specific therapeutic products, such as proteins and therapeutic nucleic acids are also discussed. Focus is given to the use of the aerosol route to deliver these products directly into the lung.

EXPERT OPINION

The use of biological carriers to deliver chemical or biological agents demonstrates great potential in modern medicine. The next generation of drug delivery systems may comprise 'cell-inspired' drug carriers that are entirely synthetic, developed using insights from cell-based therapeutics to overcome limitations of current generation synthetic carriers.

Nontuberculous mycobacteria in solid organ transplant

PURPOSE OF REVIEW

Nontuberculous mycobacteria (NTM) are emerging pathogens of concern especially in solid organ transplant candidates and recipients. This review aims to address diagnostic challenges, new and emerging treatment options, and infection prevention.

RECENT FINDINGS

The incidence of NTM infections in transplant candidates and recipients is rising. The infection prevalence of these environmental pathogens varies geographically by species with a coastal predominance. Although existing guidelines from the American Thoracic Society, Infectious Diseases Society of America, and British Thoracic Society provide recommendations for diagnosis and management, they do not fully address the subtle nuances and challenges faced in managing infections in immunocompromised transplant recipients. Evolving data on new therapeutic agents and their use in combination therapy will help individualize treatment regimens while limiting adverse effects and improving compliance. Use of combination β-lactams, avibactam, tedizolid, clofazimine, bedaquiline, liposomal amikacin, and ciprofloxacin for commonly isolated species such as Mycobacterium abscessus and Mycobacterium avium complex have proven effective.

SUMMARY

Further studies are needed to determine the incidence of NTM infection in a prospective, multicentric manner and evaluate the most promising synergistic treatment combinations in transplant recipients.

Novel drug delivery systems and significance in respiratory diseases

Pulmonary drug delivery offers targeted therapy for the treatment of respiratory diseases such as asthma, lung cancer, and chronic obstructive pulmonary diseases. However, this route poses challenges like deposition mechanism, drug instability, and rapid clearance mechanism. Other factors like the type of inhaler device, patient compatibility, consistent delivery by device, and inhaler technique also affect the performance of pulmonary delivery systems. Thus, to overcome these issues, pulmonary delivery systems utilizing particle-based approaches (nano/microparticles) have emerged in the last two decades. This chapter provides insight into various mechanisms of pulmonary drug administration, the ideal requirements of a pulmonary system, and the general devices used for pulmonary delivery. An overview of new pulmonary delivery systems and their relevance in the treatment of respiratory diseases is provided. In the end, novel pulmonary technologies that have been patented and cleared clinical trials have been highlighted along with the advances in the inhaler device.

Nanomedicine review: clinical developments in liposomal applications

Background

In recent years, disease treatment has evolved strategies that require increase in pharmaceutical agent’s efficacy and selectivity while decreasing their toxicity in normal tissues. These requirements have led to the development of nanoscale liposome systems for drug release. This review focuses on lipid features, pharmacological properties of liposomal formulations and the clinical studies of their application.

Main body

Several lipids are available, but their properties could affect pharmacological or clinical efficiency of drug formulations. Many liposomal formulations have been developed and are currently on the market. Proper selection of lipid is essential for the pharmacological effect to be improved. Most of the formulations use mainly zwitterionic, cationic or anionic lipids, PEG and/or cholesterol, which have different effects on stability, pharmacokinetics and delivery of the drug formulation. Clinical trials have shown that liposomes are pharmacologically and pharmacokinetically more efficient than drug-alone formulations in treating acute myeloid leukemia, hepatitis A, pain management, ovary, gastric breast and lung cancer, among others.

Conclusion

Liposomal formulations are less toxic than drugs alone and have better pharmacological parameters. Although they seem to be the first choice for drug delivery systems for various diseases, further research about dosage regimen regarding dose and time needs to be carried out.

Mycobacterium abscessus, an Emerging and Worrisome Pathogen among Cystic Fibrosis Patients

Nontuberculous mycobacteria (NTM) have recently emerged as important pathogens among cystic fibrosis (CF) patients worldwide. Mycobacterium abscessus is becoming the most worrisome NTM in this cohort of patients and recent findings clarified why this pathogen is so prone to this disease. M. abscessus drug therapy takes up to 2 years and its failure causes an accelerated lung function decline. The M. abscessus colonization of lung alveoli begins with smooth strains producing glycopeptidolipids and biofilm, whilst in the invasive infection, "rough" mutants are responsible for the production of trehalose dimycolate, and consequently, cording formation. Human-to-human M. abscessus transmission was demonstrated among geographically separated CF patients by whole-genome sequencing of clinical isolates worldwide. Using a M. abscessus infected CF zebrafish model, it was demonstrated that CFTR (cystic fibrosis transmembrane conductance regulator) dysfunction seems to have a specific role in the immune control of M. abscessus infections only. This pathogen is also intrinsically resistant to many drugs, thanks to its physiology and to the acquisition of new mechanisms of drug resistance. Few new compounds or drug formulations active against M. abscessus are present in preclinical and clinical development, but recently alternative strategies have been investigated, such as phage therapy and the use of β-lactamase inhibitors.

Off-label use of intravenous antimicrobials for inhalation in patients with cystic fibrosis

Management of infections in patients with cystic fibrosis (CF) presents challenges for healthcare providers, including the eradication of initial acquisition, treatment of acute exacerbations, and chronic infection with suppressive therapy. Inhaled antimicrobial therapy for infections in patients with CF has been used in these capacities, often in an effort to achieve optimal concentrations in sputum for antimicrobial efficacy while mitigating potential toxicities associated with systemic therapy. Unfortunately, there are few commercially available products formulated for inhalation, resulting in the off-label use of other formulations, such as intravenous products, administered via nebulization. This review aims to examine the evidence supporting the efficacy of these off-label formulations for management of acute and chronic infections associated with CF, as well as adverse effects associated with their use.

Nanotechnology based therapeutics for lung disease

Nanomedicine is a multidisciplinary research field with an integration of traditional sciences such as chemistry, physics, biology and materials science. The application of nanomedicine for lung diseases as a relatively new area of interdisciplinary science has grown rapidly over the last 10 years. Promising research outcomes suggest that nanomedicine will revolutionise the practice of medicine, through the development of new approaches in therapeutic agent delivery, vaccine development and nanotechnology-based medical detections. Nano-based approaches in the diagnosis and treatment of lung diseases will, in the not too distant future, change the way we practise medicine. This review will focus on the current trends and developments in the clinical translation of nanomedicine for lung diseases, such as in the areas of lung cancer, cystic fibrosis, asthma, bacterial infections and COPD.

Optimization and Lead Selection of Benzothiazole Amide Analogs Toward a Novel Antimycobacterial Agent

Mycobacteria remain an important problem worldwide, especially drug resistant human pathogens. Novel therapeutics are urgently needed to tackle both drug-resistant tuberculosis (TB) and difficult-to-treat infections with nontuberculous mycobacteria (NTM). Benzothiazole adamantyl amide had previously emerged as a high throughput screening hit against M. tuberculosis (Mtb) and was subsequently found to be active against NTM as well. For lead optimization, we applied an iterative process of design, synthesis and screening of several 100 analogs to improve antibacterial potency as well as physicochemical and pharmacological properties to ultimately achieve efficacy. Replacement of the adamantyl group with cyclohexyl derivatives, including bicyclic moieties, resulted in advanced lead compounds that showed excellent potency and a mycobacteria-specific spectrum of activity. MIC values ranged from 0.03 to 0.12 μg/mL against M. abscessus (Mabs) and other rapid- growing NTM, 1–2 μg/mL against M. avium complex (MAC), and 0.12–0.5 μg/mL against Mtb. No pre-existing resistance was found in a collection of n = 54 clinical isolates of rapid-growing NTM. Unlike many antibacterial agents commonly used to treat mycobacterial infections, benzothiazole amides demonstrated bactericidal effects against both Mtb and Mabs. Metabolic labeling provided evidence that the compounds affect the transfer of mycolic acids to their cell envelope acceptors in mycobacteria. Mapping of resistance mutations pointed to the trehalose monomycolate transporter (MmpL3) as the most likely target. In vivo efficacy and tolerability of a benzothiazole amide was demonstrated in a mouse model of chronic NTM lung infection with Mabs. Once daily dosing over 4 weeks by intrapulmonary microspray administration as 5% corn oil/saline emulsion achieved statistically significant CFU reductions compared to vehicle control and non-inferiority compared to azithromycin. The benzothiazole amides hold promise for development of a novel therapeutic agent with broad antimycobacterial activity, though further work is needed to develop drug formulations for direct intrapulmonary delivery via aerosol.