In Vitro and In Vivo Characterisation of PEG-Lipid-Based Micellar Complexes of Salmon Calcitonin for Pulmonary Delivery

Advances in the design of new types of inhaled medicines

Inhalation of small molecule drugs has proven very efficacious for the treatment of respiratory diseases due to enhanced efficacy and a favourable therapeutic index compared with other dosing routes. It enables targeted delivery to the lung with rapid onset of therapeutic action, low systemic drug exposure, and thereby reduced systemic side effects. An increasing number of pharmaceutical companies and biotechs are investing in new modalities-for this review defined as therapeutic molecules with a molecular weight >800Da and therefore beyond usual inhaled small molecule drug-like space. However, our experience with inhaled administration of PROTACs, peptides, oligonucleotides (antisense oligonucleotides, siRNAs, miRs and antagomirs), diverse protein scaffolds, antibodies and antibody fragments is still limited. Investigating the retention and metabolism of these types of molecules in lung tissue and fluid will contribute to understanding which are best suited for inhalation. Nonetheless, the first such therapeutic molecules have already reached the clinic. This review will provide information on the physiology of healthy and diseased lungs and their capacity for drug metabolism. It will outline the stability, aggregation and immunogenicity aspects of new modalities, as well as recap on formulation and delivery aspects. It concludes by summarising clinical trial outcomes with inhaled new modalities based on information available at the end of 2021.

An Update on Advancements and Challenges in Inhalational Drug Delivery for Pulmonary Arterial Hypertension

A lethal condition at the arterial–alveolar juncture caused the exhaustive remodeling of pulmonary arterioles and persistent vasoconstriction, followed by a cumulative augmentation of resistance at the pulmonary vascular and, consequently, right-heart collapse. The selective dilation of the pulmonary endothelium and remodeled vasculature can be achieved by using targeted drug delivery in PAH. Although 12 therapeutics were approved by the FDA for PAH, because of traditional non-specific targeting, they suffered from inconsistent drug release. Despite available inhalation delivery platforms, drug particle deposition into the microenvironment of the pulmonary vasculature and the consequent efficacy of molecules are influenced by pathophysiological conditions, the characteristics of aerosolized mist, and formulations. Uncertainty exists in peripheral hemodynamics outside the pulmonary vasculature and extra-pulmonary side effects, which may be further exacerbated by underlying disease states. The speedy improvement of arterial pressure is possible via the inhalation route because it has direct access to pulmonary arterioles. Additionally, closed particle deposition and accumulation in diseased tissues benefit the restoration of remolded arterioles by reducing fallacious drug deposition in other organs. This review is designed to decipher the pathological changes that should be taken into account when targeting the underlying pulmonary endothelial vasculature, especially with regard to inhaled particle deposition in the alveolar vasculature and characteristic formulations.

Expanding the arsenal against pulmonary diseases using surface-functionalized polymeric micelles: breakthroughs and bottlenecks

Pulmonary diseases such as lung cancer, asthma and tuberculosis have remained one of the common challenges globally. Polymeric micelles (PMs) have emerged as an effective technique for achieving targeted drug delivery for a local as well as a systemic effect. These PMs encapsulate and protect hydrophobic drugs, increase pulmonary targeting, decrease side effects and enhance drug efficacy through the inhalation route. In the current review, emphasis has been placed on the different barriers encountered by the drugs given via the pulmonary route and the mechanism of PMs in achieving drug targeting. The applications of PMs in different pulmonary diseases have also been discussed in detail.

Newer approaches and novel drugs for inhalational therapy for pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of small pulmonary arteries leading to increased pulmonary arterial pressure. Existing treatments acts to normalize vascular tone via three signaling pathways: the prostacyclin, the endothelin-1, and the nitric oxide. Although over the past 20 years, there has been considerable progress in terms of treatments for PAH, the disease still remains incurable with a disappointing prognosis.Areas covered: This review summarizes the pathophysiology of PAH, the advantages and disadvantages of the inhalation route, and assess the relative advantages various inhaled therapies for PAH. The recent studies concerning the development of controlled-release drug delivery systems loaded with available anti-PAH drugs have also been summarized.Expert opinion: The main obstacles of current pharmacotherapies of PAH are their short half-life, stability, and formulations, resulting in reducing the efficacy and increasing systemic side effects and unknown pathogenesis of PAH. The pulmonary route has been proposed for delivering anti-PAH drugs to overcome the shortcomings. However, the application of approved inhaled anti-PAH drugs is limited. Inhalational delivery of controlled-release nanoformulations can overcome these restrictions. Extensive studies are required to develop safe and effective drug delivery systems for PAH patients.

Development of new in vitro models of lung protease activity for investigating stability of inhaled biological therapies and drug delivery systems

Proteases play a vital role in lung health and are critically important to the metabolic clearance of inhaled protein-based therapeutics after inhalation. Surprisingly little is known about lung fluid protease composition and there is a consequent lack of biorelevant experimental models, which limits research and development in the burgeoning field of inhaled biologics. The aim of this study was to quantify proteases in human lung fluid and to use this data to design novel in vitro experimental models of lung lining fluid possessing biorelevant lung protease activity for use in biopharmaceutical stability studies. As a proof of concept, these novel models were used to investigate the effect of proteolytic activity on the stability of albumin nanoparticles, a biologic nanoparticle formulation widely investigated as a pulmonary drug delivery system. Bronchoalveolar lavage fluid was collected from healthy human volunteers and proteomic analysis was used to quantify the predominant proteases. Based on these data, four new lung protease models were constructed based on: (i) trypsin as a sole protease, (ii) dipeptidyl peptidase IV, cathepsin D, cathepsin H, and angiotensin converting enzyme in ratio and concentration to mimic the protease concentration in healthy lungs. Neutrophil elastase was used to model protease activity in inflammation. Albumin nanoparticles of 100 nm diameter remained intact over 48 h in phosphate buffered saline, but were degraded more rapidly in trypsin (50% reduction in 10 min) compared to the healthy lung protease model (50% reduction in 150 min). The addition of neutrophil elastase to the healthy lung protease model resulted in a similar, but more variable degradation profile. Nanoparticle degradation was associated with concomitant appearance of small fragments and aggregates. In conclusion, we have characterised the protease concentration in the lungs of healthy humans, designed models of lung protease activity and demonstrated their utility in studying albumin nanoparticle degradation. These methods and models have wide application to study the influence of proteases in lung disease, expression of proteases in respiratory cell culture models, stability of peptide and protein-based drugs and inhaled drug delivery systems.

Improvements in chemical carriers of proteins and peptides

The successful intracellular delivery of biologically active proteins and peptides plays an important role for therapeutic applications. Indeed, protein/peptide delivery could overcome some problems of gene therapy, for example, controlling the expression levels and the integration of transgene into the host cell genome. Thus, protein/peptide drug delivery showed a promising and safe approach for treatment of cancer and infectious diseases. Due to the unique physical and chemical properties of proteins, their production (e.g., isolation, purification & formulation) and delivery represented significant challenges in pharmaceutical studies. Modification in the structural moieties of these protein/peptide drugs could improve their solubility, stability, crystallinity, lipophilicity, enzymatic susceptibility and targetability, and subsequently, therapies and cures against various diseases. Using the structural modification of protein/peptide, their delivery provided overall higher success rates including high specificity, high activity, bioreactivity and safety. Recently, biotechnological and pharmaceutical companies have tried to find novel techniques for the modifications and improve delivery systems/carriers. However, each carrier has its own benefits and drawbacks, and an appropriate carrier is often established by the physicochemical properties of protein or peptide, the ideal route of injection, and clinical characteristics of therapy. In this review, an attempt was made to give an overview on the chemical carriers for proteins and peptides as well as the recent advances in this field.

NMR analysis of free and lipid nanodisc anchored CEACAM1 membrane proximal peptides with Ca2+/CaM

CEACAM1, a homotypic transmembrane receptor with 12 or 72 amino acid cytosolic domain isoforms, is converted from inactive cis-dimers to active trans-dimers by calcium-calmodulin (Ca²⁺/CaM). Previously, the weak binding of Ca²⁺/CaM to the human 12 AA cytosolic domain was studied using C-terminal anchored peptides. We now show the binding of ¹⁵N labeled Phe-454 cytosolic domain peptides in solution or membrane anchored using NMR demonstrates a significant role for the lipid bilayer. Although binding is increased by the mutation Phe454Ala, this mutation was previously shown to abrogate actin binding. On the other hand, Ca²⁺/CaM binding is abrogated by phosphorylation of nearby Thr-457, a post-translation modification required for actin binding and subsequent in vitro lumen formation. Binding of Ca²⁺/CaM to a membrane proximal peptide from the long 72 AA cytosolic domain anchored to lipid nanodiscs was very weak compared to lipid free conditions, suggesting membrane specific effects between the two isoforms. NMR analysis of ¹⁵N labeled Ca²⁺/CaM with unlabeled peptides showed the C-lobe of Ca²⁺/CaM is involved in peptide interactions, and hydrophobic residues such as Met-109, Val-142 and Met-144 play important roles in binding peptide. This information was incorporated into transmembrane models of CEACAM1 binding to Ca²⁺/CaM. The lack of Ca²⁺/CaM binding to phosphorylated Thr-457, a residue we have previously shown to be phosphorylated by CaMK2D, also dependent on Ca²⁺/CaM, suggests stepwise binding of the cytosolic domain first to Ca²⁺/CaM and then to actin.

Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery

Aim: Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Materials & methods: Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Results: Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Conclusion: Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

Novel delivery systems for improving the clinical use of peptides

Peptides have long been recognized as a promising group of therapeutic substances to treat various diseases. Delivery systems for peptides have been under development since the discovery of insulin for the treatment of diabetes. The challenge of using peptides as drugs arises from their poor bioavailability resulting from the low permeability of biological membranes and their instability. Currently, subcutaneous injection is clinically the most common administration route for peptides. This route is cost-effective and suitable for self-administration, and the development of appropriate dosing equipment has made performing the repeated injections relatively easy; however, only few clinical subcutaneous peptide delivery systems provide sustained peptide release. As a result, frequent injections are needed, which may cause discomfort and additional risks resulting from a poor administration technique. Controlled peptide delivery systems, able to provide required therapeutic plasma concentrations over an extended period, are needed to increase peptide safety and patient compliancy. In this review, we summarize the current peptidergic drugs, future developments, and parenteral peptide delivery systems. Special emphasis is given to porous silicon, a novel material in peptide delivery. Biodegradable and biocompatible porous silicon possesses some unique properties, such as the ability to carry exceptional high peptide payloads and to modify peptide release extensively. We have successfully developed porous silicon as a carrier material for improved parenteral peptide delivery. Nanotechnology, with its different delivery systems, will enable better use of peptides in several therapeutic applications in the near future.

A Comparison of the Pharmacokinetics and Pulmonary Lymphatic Exposure of a Generation 4 PEGylated Dendrimer Following Intravenous and Aerosol Administration to Rats and Sheep

PURPOSE

Cancer metastasis to pulmonary lymph nodes dictates the need to deliver chemotherapeutic and diagnostic agents to the lung and associated lymph nodes. Drug conjugation to dendrimer-based delivery systems has the potential to reduce toxicity, enhance lung retention and promote lymphatic distribution in rats. The current study therefore evaluated the pharmacokinetics and lung lymphatic exposure of a PEGylated dendrimer following inhaled administration.

METHODS

Plasma pharmacokinetics and disposition of a 22 kDa PEGylated dendrimer were compared after aerosol administration to rats and sheep. Lung-derived lymph could not be sampled in rats and so lymphatic transport of the dendrimer from the lung was assessed in sheep.

RESULTS

Higher plasma concentrations were achieved when dendrimer was administered to the lungs of rats as a liquid instillation when compared to an aerosol. Plasma pharmacokinetics were similar between sheep and rats, although some differences in disposition patterns were evident. Unexpectedly, less than 0.5% of the aerosol dose was recovered in pulmonary lymph.

CONCLUSIONS

The data suggest that rats provide a relevant model for assessing the pharmacokinetics of inhaled macromolecules prior to evaluation in larger animals, but that the pulmonary lymphatics are unlikely to play a major role in the absorption of nanocarriers from the lungs.

Advances in lipid-based drug delivery: enhancing efficiency for hydrophobic drugs

INTRODUCTION

Many drug candidates with high therapeutic efficacy have low water solubility, which limits the administration and transport across physiological barriers, for example, the tumor tissue barrier. Therefore, strategies are needed to permeabilize the physiological barriers safely so that hydrophobic drugs may be delivered efficiently.

AREAS COVERED

This review focuses on prospects for therapeutic application of lipid-based drug delivery carriers that increase hydrophobic drugs to improve their solubility, bioavailability, drug release, targeting and absorption. Moreover, novel techniques to prepare for lipid-based drug delivery to extend pharmaceuticals with poor bioavailability such as surface modifications of lipid-based drug delivery are presented. Industrial developments of several drug candidates employing these strategies are discussed, as well as applications and clinical trials.

EXPERT OPINION

Overall, hydrophobic drugs can be encapsulated in the lipid-based drug delivery systems, represent a relatively safe and promising strategy to extend drug retention, lengthen the lifetime in the circulation, and allow active targeting to specific tissues and controllable drug release in the desirable sites. However, there are still noticeable gaps that need to be filled before the theoretical advantage of these formulations may truly be realized such as investigation on the use of lipid-based drug delivery for administration routes. This research may provide further interest within the area of lipid-based systems, both in industry and in the clinic.

Peptide-micelle hybrids containing fasudil for targeted delivery to the pulmonary arteries and arterioles to treat pulmonary arterial hypertension

This study investigates the respirability and efficacy of peptide-micelle hybrid nanoparticles as carriers for inhalational therapy of pulmonary arterial hypertension (PAH). CARSKNKDC (CAR), a cell-penetrating and lung-homing peptide, conjugated polyethylene glycol-distearoyl-phosphoethanolamine micelles containing fasudil, an investigational anti-PAH drug, were prepared by solvent evaporation method and characterized for various physicochemical properties. The pharmacokinetics and pharmacological efficacy of hybrid particles containing fasudil were evaluated in healthy rats and monocrotaline-induced PAH rats. CAR micelles containing fasudil had an entrapment efficiency of approximately 58%, showed controlled release of the drug, and were monodispersed with an average size of approximately 14 nm. Nuclear magnetic resonance scan confirmed the drug's presence in the core of peptide-micelle hybrid particles. Compared with plain micelles, CAR peptide increased the cellular uptake by approximately 1.7-fold and extended the drug half-life by approximately fivefold. The formulations were more prone to accumulate in the pulmonary vasculature than in the peripheral blood, which is evident from the ratio of the extent of reduction of pulmonary and systemic arterial pressures. On the whole, this study demonstrates that peptide-polymer hybrid micelles can serve as inhalational carriers for PAH therapy.

Biopharmaceutical in vitro characterization of CPZEN-45, a drug candidate for inhalation therapy of tuberculosis

BACKGROUND

The caprazamycin derivative, CPZEN-45 has previously demonstrated antitubercular activity against Mycobacterium tuberculosis H37Rv. Here, the authors report a basic biopharmaceutical characterization of the compound focusing on in vitro permeability and cytotoxicity, with respect to the suitability of CPZEN-45 hydrochloride for inhalation treatment of tuberculosis.

RESULTS

MTT assays confirmed that CPZEN-45 HCl had no acute cytotoxic effects up to 3 mg/ml. In transport studies, apparent permeability coefficients of CPZEN-45 HCl across Calu-3 monolayers in absorptive and secretive directions were 0.43 ± 0.20 × 10(-6) cm/s and 0.38 ± 0.12 × 10(-6) cm/s, respectively. Across ATI-like monolayers, apparent permeability values were 12.10 ± 4.31 × 10(-6) cm/s and 8.50 ± 1.83 × 10(-6) cm/s. CPZEN-45 HCl formed colloidal complexes at concentrations above 0.38 mg/ml; however, these complexes were not micelles, as assessed by Orange OT encapsulation assay.

CONCLUSION

CPZEN-45 is an interesting new drug candidate with potential to be used in aerosol therapy of tuberculosis.

Pulmonary administration of PEGylated polylysine dendrimers: absorption from the lung versus retention within the lung is highly size-dependent

The systemic delivery of drugs via the inhaled route is an attractive, needle-free means of improving the systemic exposure of molecules such as peptides and proteins that are poorly absorbed after oral administration. Directed delivery into the lungs also provides a means of increasing drug concentrations at the site of action for lung-specific disease states such as pulmonary infections and lung cancer. The current study has examined the potential utility of PEGylated polylysine dendrimers as pulmonary delivery agents and in particular sought to explore the relationship between dendrimer size and absorption of the intact construct (as a potential systemic delivery mechanism) versus retention within the lungs (as a potential pulmonary depot for controlled local release). Dendrimer absorption from the lungs was inversely correlated with molecular weight, with approximately 20-30% of the dose of relatively small (<22 kDa) dendrimers systemically absorbed compared to only 2% absorption for a larger (78 kDa) PEGylated dendrimer. Increasing the molecular weight of the dendrimers led to slower absorption and more prolonged retention in the lung tissue and bronchoalveolar lavage fluid. Oral administration of the two smaller dendrimers confirmed that oral bioavailability of the PEGylated dendrimers was essentially zero and did not contribute to exposure after pulmonary administration. The smaller PEGylated dendrimers were also degraded in the lungs to low molecular weight products that were subsequently absorbed and excreted via the urine, while the larger constructs showed good stability in the lungs. The data suggest first, that small PEGylated dendrimer-based drug delivery systems may be delivered to the blood via inhalation, providing a more attractive alternative to injections, and second that larger PEGylated dendrimers may be retained in the lungs providing the potential for controlled delivery of medications to the blood or lung tissue.