Delivery Systems as Vital Tools in Drug Repurposing

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Telmisartan loaded lipid nanocarrier as a potential repurposing approach to treat glioma: characterization, apoptosis evaluation in U87MG cells, pharmacokinetic and molecular simulation study

The study explores anticancer potential of telmisartan (TS) loaded lipid nanocarriers (TLNs) in glioma cells as a potential repurposing nanomodality along with estimation of drug availability at rat brain. Experimental TLNs were produced by previously reported method and characterized.In vitroanticancer efficacy of experimental TLNs was estimated by MTT, confocal microscopy, and FACs analysis in glioma cells. Plasma and brain pharmacokinetic (PK) parameters were also analysed by LCMS/MS. Spherical, nanosized, homogenous, unilamellar, TLNs were reported having desirable drug loading (9.5% ± 0.6%), negative zeta potential and sustained TS release tendency. FITC-TLNs were sufficiently internalized into U87MG cells line within 0.5 h incubation period. IC50for TLNs was considerably higher than free TS in the tested glioma cell lines. Further, TLNs induced superior apoptotic effect in U87MG cells than TS. PK (plasma/brain) data depicted higher AUC,Vss, MRT with lower Cltfor TLNs suggesting improved bioavailability,in vivoresidence and sustained drug availability than free TS administration. Docking studies rationalizedin vitro/in vivoresults as preferably higher binding affinity (docking score:12.4) was detected for TS with glioma proteins. Further,in vivostudies in glioma bearing xenograft model is underway for futuristic clinical validation of TLNs.

Pathogenesis of COVID19 and the applications of US FDA-approved repurposed antiviral drugs to combat SARS-CoV-2 in Saudi Arabia: A recent update by review of literature

Still, there is no cure for the highly contagious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-caused coronavirus disease 2019 (COVID19). The COVID19 pandemic caused health emergencies which resulted in enormous medical and financial consequences worldwide including Saudi Arabia. Saudi Arabia is the largest Arab country of the Middle East. The urban setting of Saudi Arabia makes it vulnerable towards SARS-CoV-2 (SCV-2). Religious areas of this country are visited by millions of pilgrims every year for the Umrah and Hajj pilgrimage, which contributes to the potential COVID19 epidemic risk. COVID19 throws various challenges to healthcare professionals to choose the right drugs or therapy in clinical settings because of the lack of availability of newer drugs. Current drug development and discovery is an expensive, complex, and long process, which involves a high failure rate in clinical trials. While repurposing of United States Food and Drug Administration (US FDA)-approved antiviral drugs offers numerous benefits including complete pharmacokinetic and safety profiles, which significantly shorten drug development cycles and reduce costs. A range of repurposed US FDA-approved antiviral drugs including ribavirin, lopinavir/ritonavir combination, oseltamivir, darunavir, remdesivir, nirmatrelvir/ritonavir combination, and molnupiravir showed encouraging results in clinical trials in COVID19 treatment. In this article, several COVID19-related discussions have been provided including emerging variants of concern of, COVID19 pathogenesis, COVID19 pandemic scenario in Saudi Arabia, drug repurposing strategies against SCV-2, as well as repurposing of US FDA-approved antiviral drugs that might be considered to combat SCV-2 in Saudi Arabia. Moreover, drug repurposing in the context of COVID19 management along with its limitations and future perspectives have been summarized.

Reimagining old drugs with new tricks: Mechanisms, strategies and notable success stories in drug repurposing for neurological diseases

Recent evolution in drug repurposing has brought new anticipation, especially in the conflict against neurodegenerative diseases (NDDs). The traditional approach to developing novel drugs for these complex disorders is laborious, time-consuming, and often abortive. However, drug reprofiling which is the implementation of illuminating novel therapeutic applications of existing approved drugs, has shown potential as a promising strategy to accelerate the hunt for therapeutics. The advancement of computational approaches and artificial intelligence has expedited drug repurposing. These progressive technologies have enabled scientists to analyse extensive datasets and predict potential drug-disease interactions. By prospecting into the existing pharmacological knowledge, scientists can recognise potential therapeutic candidates for reprofiling, saving precious time and resources. Preclinical models have also played a pivotal role in this field, confirming the effectiveness and mechanisms of action of repurposed drugs. Several studies have occurred in recent years, including the discovery of available drugs that demonstrate significant protective effects in NDDs, relieve debilitating symptoms, or slow down the progression of the disease. These findings highlight the potential of repurposed drugs to change the landscape of NDD treatment. Here, we present an overview of recent developments and major advances in drug repurposing intending to provide an in-depth analysis of traditional drug discovery and the strategies, approaches and technologies that have contributed to drug repositioning. In addition, this chapter attempts to highlight successful case studies of drug repositioning in various therapeutic areas related to NDDs and explore the clinical trials, challenges and limitations faced by researchers in the field. Finally, the importance of drug repositioning in drug discovery and development and its potential to address discontented medical needs is also highlighted.

Curcumin I-SMA nanomicelles as promising therapeutic tool to tackle bacterial infections

Renewed interest towards natural substances has been pushed by the widespread diffusion of antibiotic resistance. Curcumin I is the most active and effective constituent of curcuminoids extracted from Curcuma longa and, among other beneficial effects, attracted attention for its antimicrobial potential. Since the poor pharmacokinetic profile hinders its efficient utilization, in the present paper, we report encapsulation of curcumin I in poly(styrene-co-maleic acid) (SMA-CUR) providing a nanomicellar system with improved aqueous solubility and bioavailability. SMA-CUR was characterized by means of size, zeta potential, polydispersity index, atomic force microscopy (AFM), drug release studies, spectroscopic properties and stability. SMA-CUR nanoformulation displayed exciting antimicrobial properties compared to free curcumin I towards Gram-positive and Gram-negative clinical isolates.

COVID-19 therapeutics: Clinical application of repurposed drugs and futuristic strategies for target-based drug discovery

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes the complicated disease COVID-19. Clinicians are continuously facing huge problems in the treatment of patients, as COVID-19-specific drugs are not available, hence the principle of drug repurposing serves as a one-and-only hope. Globally, the repurposing of many drugs is underway; few of them are already approved by the regulatory bodies for their clinical use and most of them are in different phases of clinical trials. Here in this review, our main aim is to discuss in detail the up-to-date information on the target-based pharmacological classification of repurposed drugs, the potential mechanism of actions, and the current clinical trial status of various drugs which are under repurposing since early 2020. At last, we briefly proposed the probable pharmacological and therapeutic drug targets that may be preferred as a futuristic drug discovery approach in the development of effective medicines.

Oral Mucosa Models to Evaluate Drug Permeability

Due to its numerous advantages, such as excellent drug accessibility, rapid absorption, and bypass of first-pass metabolism, the route of drug administration that involves crossing the oral mucosa is highly favored. As a result, there is significant interest in investigating the permeability of drugs through this region. The purpose of this review is to describe the various ex vivo and in vitro models used to study the permeability of conveyed and non-conveyed drugs through the oral mucosa, with a focus on the most effective models. Currently, there is a growing need for standardized models of this mucosa that can be used for developing new drug delivery systems. Oral Mucosa Equivalents (OMEs) may provide a promising future perspective as they are capable of overcoming limitations present in many existing models.

Fabrication and characterization of anti-rosacea 3D nanofibrous customized sheet masks as a novel scaffold for repurposed use of spironolactone with pre-clinical studies

The repurposed oral use of spironolactone (SP) as an anti-rosacea drug faces many challenges that hinder its efficacy and compliance. In this study, a topically applied nanofibers (NFs) scaffold was evaluated as a promising nanocarrier that enhances SP activity and avoids the friction routine that exaggerates rosacea patients' inflamed, sensitive skin. SP-loaded poly-vinylpyrrolidone (40% PVP) nanofibers (SP-PVP NFs) were electrospun. Scanning electron microscopy showed that SP-PVP NFs have a smooth homogenous surface with a diameter of about 426.60 nm. Wettability, solid state, and mechanical properties of NFs were evaluated. Encapsulation efficiency and drug loading were 96.34% ± 1.20 and 11.89% ± 0.15, respectively. The in vitro release study showed a higher amount of SP released over pure SP with a controlled release pattern. Ex vivo results showed that the permeated amount of SP from SP-PVP NFs sheets was 4.1 times greater than that of pure SP gel. A higher percentage of SP was retained in different skin layers. Moreover, the in vivo anti-rosacea efficacy of SP-PVP NFs using croton oil challenge showed a significant reduction in erythema score compared to the pure SP. The stability and safety of NFs mats were proved, indicating that SP-PVP NFs are promising carriers of SP.

Heavy-Metal Trojan Horse: Enterobactin-Directed Delivery of Platinum(IV) Prodrugs to Escherichia coli

The global crisis of untreatable microbial infections necessitates the design of new antibiotics. Drug repurposing is a promising strategy for expanding the antibiotic repertoire. In this study, we repurpose the clinically approved anticancer agent cisplatin into a targeted antibiotic by conjugating its Pt(IV) prodrug to enterobactin (Ent), a triscatecholate siderophore employed by Enterobacteriaceae for iron (Fe) acquisition. The l-Ent-Pt(IV) conjugate (l-EP) exhibits antibacterial activity against Escherichia coli K12 and the uropathogenic isolate E. coli CFT073. Similar to cisplatin, l-EP causes a filamentous morphology in E. coli and initiates lysis in lysogenic bacteria. Studies with E. coli mutants defective in Ent transport proteins show that Ent mediates the delivery of l-EP into the E. coli cytoplasm, where reduction of the Pt(IV) prodrug releases the cisplatin warhead, causing growth inhibition and filamentation of E. coli. Substitution of Ent with its enantiomer affords the d-Ent-Pt(IV) conjugate (d-EP), which displays enhanced antibacterial activity, presumably because d-Ent cannot be hydrolyzed by Ent esterases and thus Fe cannot be released from this conjugate. E. coli treated with l/d-EP accumulate ≥10-fold more Pt as compared to cisplatin treatment. By contrast, human embryonic kidney cells (HEK293T) accumulate cisplatin but show negligible Pt uptake after treatment with either conjugate. Overall, this work demonstrates that the attachment of a siderophore repurposes a Pt anticancer agent into a targeted antibiotic that is recognized and transported by siderophore uptake machinery, providing a design strategy for drug repurposing by siderophore modification and heavy-metal "trojan-horse" antibiotics.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

A Novel Computational Approach for the Discovery of Drug Delivery System Candidates for COVID-19

In order to treat Coronavirus Disease 2019 (COVID-19), we predicted and implemented a drug delivery system (DDS) that can provide stable drug delivery through a computational approach including a clustering algorithm and the Schrödinger software. Six carrier candidates were derived by the proposed method that could find molecules meeting the predefined conditions using the molecular structure and its functional group positional information. Then, just one compound named glycyrrhizin was selected as a candidate for drug delivery through the Schrödinger software. Using glycyrrhizin, nafamostat mesilate (NM), which is known for its efficacy, was converted into micelle nanoparticles (NPs) to improve drug stability and to effectively treat COVID-19. The spherical particle morphology was confirmed by transmission electron microscopy (TEM), and the particle size and stability of 300-400 nm were evaluated by measuring DLSand the zeta potential. The loading of NM was confirmed to be more than 90% efficient using the UV spectrum.

Liposomes as a Nanoplatform to Improve the Delivery of Antibiotics into Staphylococcus aureus Biofilms

Staphylococcus aureus biofilm-associated infections are a major public health concern. Current therapies are hampered by reduced penetration of antibiotics through biofilm and low accumulation levels at infected sites, requiring prolonged usage. To overcome these, repurposing antibiotics in combination with nanotechnological platforms is one of the most appealing fast-track and cost-effective approaches. In the present work, we assessed the potential therapeutic benefit of three antibiotics, vancomycin, levofloxacin and rifabutin (RFB), through their incorporation in liposomes. Free RFB displayed the utmost antibacterial effect with MIC and MBIC₅₀ below 0.006 µg/mL towards a methicillin susceptible S. aureus (MSSA). RFB was selected for further in vitro studies and the influence of different lipid compositions on bacterial biofilm interactions was evaluated. Although positively charged RFB liposomes displayed the highest interaction with MSSA biofilms, RFB incorporated in negatively charged liposomes displayed lower MBIC₅₀ values in comparison to the antibiotic in the free form. Preliminary safety assessment on all RFB formulations towards osteoblast and fibroblast cell lines demonstrated that a reduction on cell viability was only observed for the positively charged liposomes. Overall, negatively charged RFB liposomes are a promising approach against biofilm S. aureus infections and further in vivo studies should be performed.

The pulmonary route as a way to drug repositioning in COVID-19 therapy

Introduction

The outbreak of the disease caused by the new coronavirus (COVID-19) has been affecting society's routine and its patterns of interaction worldwide, in addition to the impact on the global economy. To date, there is still no clinically effective treatment for this comorbidity, and drug repositioning might be a good strategy considering the established clinical safety profile. In this context, since COVID-19 affects the respiratory tract, a promising approach would be the pulmonary drug delivery.

Objective

Identify repurposing drug candidates for the treatment of COVID-19 based on the data of ongoing clinical trials and in silico studies and also assess their potential to be applied in formulations for pulmonary administration.

Method

A integrative literature review was conducted between June and July 2020, by extracting the results from Clinical Trials, PubMed, Web of Science and Science Direct databases.

Results

By crossing the results obtained from diverse sources, 21 common drugs were found, from which only 4 drugs presented studies of pulmonary release formulations, demonstrating the need for greater investment and incentive in this field.

Conclusion

Even though the lung is a target that facilitates viral infection and replication, formulations for pulmonary delivery of suitable drugs are still lacking for COVID-19 treatment. However, it is indisputable that the pandemic constitutes a concrete demand, with a profound impact on public health, and that, with the appropriate investments, it will give the pharmaceutical industry an opportunity to reinforce the pulmonary delivery field.

Chemo-physical Strategies to Advance the in Vivo Functionality of Targeted Nanomedicine: The Next Generation

The past few decades have witnessed an evolution of nanomedicine from biologically inert entities to more smart systems, aimed at advancing in vivo functionality. However, we should recognize that most systems still rely on reasonable explanation-including some over-explanation-rather than definitive evidence, which is a watershed radically determining the speed and extent of advancing nanomedicine. Probing nano-bio interactions and desirable functionality at the tissue, cellular, and molecular levels is most frequently overlooked. Progress toward answering these questions will provide instructive insight guiding more effective chemo-physical strategies. Thus, in the next generation, we argue that much effort should be made to provide definitive evidence for proof-of-mechanism, in lieu of creating many new and complicated systems for similar proof-of-concept.

Nucleic Acid Aptamers as a Potential Nucleus Targeted Drug Delivery System

BACKGROUND

Nucleus targeted drug delivery provides several opportunities for the treatment of fatal diseases such as cancer. However, the complex nucleocytoplasmic barriers pose significant challenges for delivering a drug directly and efficiently into the nucleus. Aptamers representing singlestranded DNA and RNA qualify as next-generation highly advanced and personalized medicinal agents that successfully inhibit the expression of certain proteins; possess extraordinary gene-expression for manoeuvring the diseased cell's fate with negligible toxicity. In addition, the precisely directed aptamers to the site of action present a tremendous potential to reach the nucleus by escaping the ensuing barriers to exhibit a better drug activity and gene expression.

OBJECTIVE

This review epigrammatically highlights the significance of targeted drug delivery and presents a comprehensive description of the principal barriers faced by the nucleus targeted drug delivery paradigm and ensuing complexities thereof. Eventually, the progress of nucleus targeting with nucleic acid aptamers and success achieved so far have also been reviewed.

METHODS

Systematic literature search was conducted of research published to date in the field of nucleic acid aptamers.

CONCLUSION

The review specifically points out the contribution of individual aptamers as the nucleustargeting agent rather than aptamers in conjugated form.

Utilizing drug repurposing against COVID-19 - Efficacy, limitations, and challenges

The recent outbreak of Coronavirus disease (COVID-19), first in Eastern Asia and then essentially across the world has been declared a pandemic by the WHO. COVID-19 is caused by a novel virus SARS-CoV2 (2019-nCoV), against which there is currently no vaccine available; and current antiviral therapies have failed, causing a very high mortality rate. Drug repurposing i.e. utilizing an approved drug for different indication, offers a time- and cost-efficient alternative for making new therapies available to patients. Although there are several reports presenting novel approaches to treat COVID-19, still an attentive review of previous scientific literature is essential to overcome their failure to exhibit efficacy. There is an urgent need to provide a comprehensive outlook toward utilizing drug repurposing as a tool for discovery of new therapies against COVID-19. In this article, we aim to provide a to-the-point review of current literature regarding efficacy of repurposed drugs against COVID-19 and other respiratory infections caused by coronaviruses. We have briefly discussed COVID-19 epidemiology, and then have discussed drug repurposing approaches and examples, specific to respiratory viruses. Limitations of utilization of repurposed drug molecules such as dosage regimen and associated challenges such as localized delivery in respiratory tract have also been discussed in detail.

Overcoming barriers confronting application of protein therapeutics in bone fracture healing

Bone fracture is a major contributor to debilitation and death among patients with bone diseases. Thus, osteogenic protein therapeutics and their delivery to bone have been extensively researched as strategies to accelerate fracture healing. To prevent morbidity and mortality of fractures, which occur frequently in the aging population, there is a critical need for development of first-line therapeutics. Bone morphogenic protein-2 (BMP-2) has been at the forefront of bone regeneration research for its potent osteoinduction, despite safety concerns and biophysiological obstacles of delivery to bone. However, continued pursuit of osteoinductive proteins as a therapeutic option is largely aided by drug delivery systems, playing an imperative role in enhancing safety and efficacy. In this work, we highlighted several types of drug delivery platforms and their biomaterials, to evaluate the suitability in overcoming challenges of therapeutic protein delivery for bone regeneration. To showcase the clinical considerations for each type of platform, we have assessed the most common route of administration strategies for bone regeneration, classifying the platforms as implantable or injectable. Additionally, we have analyzed the commonly utilized models and methodology for safety and efficacy evaluation of these osteogenic protein-loaded systems, to present clinical opinions for future directions of research in this field. It is hoped that this review will promote research and development of clinically translatable osteogenic protein therapeutics, while targeting first-line treatment status for achieving desired outcomes of fracture healing. Graphical abstract.

Computational approaches for drug discovery against trypanosomatid-caused diseases

During three decades, only about 20 new drugs have been developed for malaria, tuberculosis and all neglected tropical diseases (NTDs). This critical situation was reached because NTDs represent only 10% of health research investments; however, they comprise about 90% of the global disease burden. Computational simulations applied in virtual screening (VS) strategies are very efficient tools to identify pharmacologically active compounds or new indications for drugs already administered for other diseases. One of the advantages of this approach is the low time-consuming and low-budget first stage, which filters for testing experimentally a group of candidate compounds with high chances of binding to the target and present trypanocidal activity. In this work, we review the most common VS strategies that have been used for the identification of new drugs with special emphasis on those applied to trypanosomiasis and leishmaniasis. Computational simulations based on the selected protein targets or their ligands are explained, including the method selection criteria, examples of successful VS campaigns applied to NTDs, a list of validated molecular targets for drug development and repositioned drugs for trypanosomatid-caused diseases. Thereby, here we present the state-of-the-art of VS and drug repurposing to conclude pointing out the future perspectives in the field.

Lipid Nanoparticles as a Skin Wound Healing Drug Delivery System: Discoveries and Advances

Chronic wounds are a remarkable cause of morbidity, requiring long-time treatments with a significant impact on the quality of life and high costs for public health. Although there are a variety of topical skin preparations commercially available, they have several limitations that frequently impair wound healing, such as drug instability, toxicity, limited time of action and ineffective skin permeation. In recent years, researchers have focused on the development of new effective treatments for wound healing and shown frequent interest in nanometric drug delivery systems to overcome such obstacles. In dermatology, lipid nanoparticles (LNPs) have received great attention from researchers due to their great functionalities, greater adhesion to the skin and film formation, enabling the hydration and maintenance of skin integrity, as well as present a more effective penetration through the skin barrier. This review provides an update on topical formulations based on Solid Lipid Nanoparticles (SLNs) and Nanostructured Lipid Carriers (NLCs) as wound healing treatments. Both SLNs and NLCs are able to increase solubility and stability of active pharmaceutical ingredients and increase skin penetration compared to the free drugs. Additionally, SLNs and NLCs can increase pharmacological activity, increase the release profile of the drugs, promote synergistic effects and improve the sensory properties of the final formulation. Topical dosage forms containing nanoparticles have been extensively evaluated for wound healing activity, mainly the dressings, films and scaffolds. Therefore, lipid nanoparticles have contributed in improving wound healing therapies when incorporated into other dosage forms with better efficacy and lesser adverse effects than conventional formulations.

Nose-to-brain co-delivery of repurposed simvastatin and BDNF synergistically attenuates LPS-induced neuroinflammation

A therapeutic strategy that can combat the multifaceted nature of neuroinflammation pathology was investigated. Thus, we fabricated PEG-PdLLA polymersomes and evaluated the efficacy in co-delivery of simvastatin (Sim, as a repurposed anti-inflammatory agent) with brain derived neurotrophic factor (BDNF, as an exogeneous trophic factor supplementation). Using LPS model of neuroinflammation, intranasal administration of combination drug-loaded polymersomes (containing both Sim and BDNF; Sim-BDNF-Ps) markedly down-regulated brain levels of cytokines compared to free drug and single-drug-loaded polymersomes. Further, Sim-BDNF-Ps effectively replenished brain level of BDNF that was depleted following neuroinflammation, resulting in a 2-fold BDNF increase versus untreated LPS control group. We found out that the efficiency of the combination drug-loaded polymersomes to suppress microglia activation in brain regions followed the order: frontal cortex > striatum > hippocampus. Our findings indicated that Sim-BDNF-Ps could effectively inhibit microglial-mediated inflammation as well as potentially resolve the neurotoxic microenvironment that is often associated with neuroinflammation.

X-Ray Characterization of Pharmaceutical and Cosmetic Lipidic Nanoparticles for Cutaneous Application

Starting from the second half of the 1900s, the advent of nanotechnology in medicine has provoked a profound revolution in this area; at present, nanomedicine delivered a remarkably large set of research and clinically useful tools as diagnostic devices, contrast agents, analytical tools, physical therapy applications, and drugdelivery vehicles. Concerning nanoformulations for drug delivery, they are constituted by nanoparticles with dimensions lower than 1 μm, usually characterized by improved pharmacokinetics, taking advantage of specific targeting, and reduced side effects. The contributors to the present chapter are reviewing a range of papers related to the structural characterization of nanoformulations by X-ray diffraction techniques. The whole of the considered papers underlines the essential role that biophysical techniques have acquired as an essential prerequisite to understanding stability, bioavailability, and lipid, biopolymer, and drug organization in nanoformulations.