Nitrones as therapeutics

Nitrones have the general chemical formula X-CH=NO-Y. They were first used to trap free radicals in chemical systems and then subsequently in biochemical systems. More recently several nitrones, including alpha-phenyl-tert-butylnitrone (PBN), have been shown to have potent biological activity in many experimental animal models. Many diseases of aging, including stroke, cancer development, Parkinson disease, and Alzheimer disease, are known to have enhanced levels of free radicals and oxidative stress. Some derivatives of PBN are significantly more potent than PBN and have undergone extensive commercial development for stroke. Recent research has shown that PBN-related nitrones also have anti-cancer activity in several experimental cancer models and have potential as therapeutics in some cancers. Also, in recent observations nitrones have been shown to act synergistically in combination with antioxidants in the prevention of acute acoustic-noise-induced hearing loss. The mechanistic basis of the potent biological activity of PBN-related nitrones is not known. Even though PBN-related nitrones do decrease oxidative stress and oxidative damage, their potent biological anti-inflammatory activity and their ability to alter cellular signaling processes cannot readily be explained by conventional notions of free radical trapping biochemistry. This review is focused on our studies and others in which the use of selected nitrones as novel therapeutics has been evaluated in experimental models in the context of free radical biochemical and cellular processes considered important in pathologic conditions and age-related diseases.     

Copper complexes as therapeutic agents

The importance of transition metals in biological processes has been well established. Copper (Cu) is a transition metal that can exist in oxidised and reduced states. This allows it to participate in redox and catalytic chemistry, making it a suitable cofactor for a diverse range of enzymes and molecules. Cu deficiency or toxicity is implicated in a variety of pathological conditions; therefore inorganic complexes of Cu have been investigated for their therapeutic and diagnostic potential. These Cu complexes have been shown to be effective in cancer treatment due to their cytotoxic action on tumour cells. Alternatively, Cu complexes can also modulate Cu homeostasis in the brain, resulting in protective effects in several models of neurodegeneration. In other diseases such as coronary heart disease and skin disease, the success of Cu complexes as potential therapeutics will most likely be due to their ability to increase SOD activity, leading to relief of oxidative stress. This review seeks to provide a broad insight into some of the diverse actions of Cu complexes and demonstrate the strong future for these compounds as potential therapeutic agents.     

Protease research in the era of systems biology

Proteases are specific modulators of signaling molecules and their underlying pathways in addition to their degradative roles. However, proteases do not act alone, but form cascades, circuits and networks that all dynamically interconnect to form the protease web, which defines the proteolytic potential of a cell or tissue in a defined condition. To describe the protease web and its net activity several novel high-throughput proteomic techniques, in the field termed degradomics, have been developed. Emerging systems biology methods to evaluate the expression, activity and substrate discovery of proteases are presented. Understanding the protease web and its perturbations in pathology will help to develop new therapeutics for the treatment of diseases, such as cancer, arthritis and chronic obstructive pulmonary diseases.     

Mitochondrial diseases: Drosophila melanogaster as a model to evaluate potential therapeutics

While often presented as a single entity, mitochondrial diseases comprise a wide range of clinical, biochemical and genetic heterogeneous disorders. Among them, defects in the process of oxidative phosphorylation are the most prevalent. Despite intense research efforts, patients are still without effective treatment. An important part of the development of new therapeutics relies on predictive models of the pathology in order to assess their therapeutic potential. Since mitochondrial diseases are a heterogeneous group of progressive multisystemic disorders that can affect any organ at any time, the development of various in vivo models for the different diseases-associated genes defects will accelerate the search for effective therapeutics. Here, we review existing Drosophila melanogaster models for mitochondrial diseases, with a focus on alterations in oxidative phosphorylation, and discuss the potential of this powerful model organism in the process of drug target discovery.This article is part of a Directed Issue entitled: Energy Metabolism Disorders and Therapies.     

Drug repositioning for orphan diseases

The need and opportunity to discover therapeutics for rare or orphan diseases are enormous. Due to limited prevalence and/or commercial potential, of the approximately 6000 orphan diseases (defined by the FDA Orphan Drug Act as <200 000 US prevalence), only a small fraction (5%) is of interest to the biopharmaceutical industry. The fact that drug development is complicated, time-consuming and expensive with extremely low success rates only adds to the low rate of therapeutics available for orphan diseases. An alternative and efficient strategy to boost the discovery of orphan disease therapeutics is to find connections between an existing drug product and orphan disease. Drug Repositioning or Drug Repurposing--finding a new indication for a drug--is one way to maximize the potential of a drug. The advantages of this approach are manifold, but rational drug repositioning for orphan diseases is not trivial and poses several formidable challenges--pharmacologically and computationally. Most of the repositioned drugs currently in the market are the result of serendipity. One reason the connection between drug candidates and their potential new applications are not identified in an earlier or more systematic fashion is that the underlying mechanism 'connecting' them is either very intricate and unknown or indirect or dispersed and buried in an ever-increasing sea of information, much of which is emerging only recently and therefore is not well organized. In this study, we will review some of these issues and the current methodologies adopted or proposed to overcome them and translate chemical and biological discoveries into safe and effective orphan disease therapeutics.     

Therapeutic peptides: technological advances driving peptides into development

As potential therapeutics, peptides offer several advantages over small molecules (increased specificity) and antibodies (small size). Nevertheless, a number of key issues have hampered their use as drug candidates. A series of new technologies have recently been developed that allow peptides to be viable drug candidates in areas usually restricted to protein therapeutics, such as monoclonal antibodies. These include the development of various types of peptide-conjugates that have lower rates of clearance and hence the potential to increase the exposure of peptide drug candidates in chronic diseases. Structural additions have also been made to peptides, including the use of unnatural amino acids, mainchain modifications and other novel substitutions, which have helped to improve peptide stability and further their therapeutic potential.     

Promising antifungal agents: A minireview

In the recent past, prevalence of life threatening fungal diseases have increased rapidly in immune-compromised cases such as acquired immunodeficiency syndrome (AIDS), cancer, organ transplant etc. Side by side, the appearance of drug resistance to the presently available antifungal therapeutics is on a rapid rise. It has become a top priority for the academia and pharmaceutical industries to develop new antifungal agents able to combat this resistance, and at the same time, possess potential broad spectrum of activity and minimum toxicity. An understanding of the pharmacological interactions between antifungal agents and their targets offers opportunities for design of new therapeutics. This review discusses the various methodology of drug design, structure activity relationships (SARs), and mode of action of variety of new antifungal agents.     

Combination therapeutics in complex diseases

The biological redundancies in molecular networks of complex diseases limit the efficacy of many single drug therapies. Combination therapeutics, as a common therapeutic method, involve pharmacological intervention using several drugs that interact with multiple targets in the molecular networks of diseases and may achieve better efficacy and/or less toxicity than monotherapy in practice. The development of combination therapeutics is complicated by several critical issues, including identifying multiple targets, targeting strategies and the drug combination. This review summarizes the current achievements in combination therapeutics, with a particular emphasis on the efforts to develop combination therapeutics for complex diseases.     

Coming of age: anti-cytokine therapies

Although cytokines are critical in maintaining normal physiology, excessive production of these proteins can lead to pathological consequences. Inhibitors of cytokine production or action are therefore widely investigated as potential therapeutic agents in a variety of immune and inflammatory diseases. Indeed, the successful application of inhibitors of tumor necrosis factor-alpha in rheumatoid arthritis and Crohn's disease heralds the great therapeutic potential of biopharmaceutical agents to counteract cytokine activities. Emerging opportunities for new therapeutics, as well as the challenges we face in their use and development, are described in this review.     

α-Aryl-N-aryl nitrones: Synthesis and screening of a new scaffold for cellular protection against an oxidative toxic stimulus

Nitrone-containing compounds are commonly employed as spin traps of free radical species in chemical and biological studies. Some molecules as α-phenyl-N-t-butyl nitrone (PBN) and its derivatives have been tested as potential drugs to treat oxidative stress related diseases, as Alzheimer and stroke for example. In this work we report the design and the synthesis of α-aryl-N-aryl nitrones and their cytoprotection profile on human neuroblastoma cells (SH-SY5Y) under induced oxidative stress. All the nine synthesized nitrones showed a significant response at low micromolar concentration. The selected compound 8 (α-phenyl-N-phenyl nitrone) increased the reduced glutathione (GSH) levels by 65% and lowered the necrotic cell death from 25.8% to 3.8%. Based on our data, the designed highly conjugated nitrone double-bond skeleton can be considered as a good scaffold for further studies regarding oxidative stress-related diseases.     

Shedding light on designing potential meprin β inhibitors through ligand-based robust validated computational approaches: A proposal to chemists!

Human meprin (EC 3.4.24.18) is a member of the metzincin superfamily. It correlates with matrix metalloproteinases and ADAMs (a disintegrin and metalloproteinase). Overexpression of meprin β is implicated in fibrosis, inflammatory diseases and cancers. However, selective meprin β inhibition is crucial to reduce cancer metastasis and adverse effects in inflammation. It also plays critical roles in modulating several interleukins and growth factors. Moreover, meprin β cleaves amyloid precursor protein, thought to be involved in the progression of Alzheimer’s disease. Therefore, meprin β inhibitors are considered to be emerging therapeutics with paramount importance in the treatment of kidney failure, fibrosis, inflammatory bowel diseases and cancer. Despite its crucial implication in several diseases, no meprin β inhibitors are available as drug candidates till date. Therefore, it is an urgent need to identify new potential meprin β inhibitors as prospective therapeutics. In this article, a series of meprin β inhibitors has been analysed through multiple molecular modelling studies as the first initiative to get an idea about their structural, physicochemical and pharmacophoric requirements for higher activity. All in silico approaches performed here are statistically validated and subsequently adjudicated each other. Compounds with p-carboxylic acid substituted arylsulphonamide moiety attached with m-carboxylic acid substituted benzyl group along with a methylene hydroxamate function may be crucial for imparting potential meprin β inhibition. Depending on the results obtained, 14 molecules have been proposed by QSAR model that predicted a minimum of 4-fold higher activity compared to these compounds of the current study.     

Using induced pluripotent stem cell neuronal models to study neurodegenerative diseases

Current application of human induced pluripotent stem cells (hiPSCs) technology in patient-specific models of neurodegenerative disorders recapitulate some of key phenotypes of diseases, representing disease-specific cellular modeling and providing a unique platform for therapeutics development. We review recent efforts toward advancing hiPSCs-derived neuronal cell types and highlight their potential use for the development of more complex in vitro models of neurodegenerative diseases by focusing on Alzheimer's disease, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. We present evidence from previous works on the important phenotypic changes of various neuronal types in these neurological diseases. We also summarize efforts on conducting low- and high-throughput screening experiments with hiPSCs toward developing potential therapeutics for treatment of neurodegenerative diseases. Lastly, we discuss the limitations of hiPSCs culture system in studying neurodegenerative diseases and alternative strategies to overcome these hurdles.     

Polyketal copolymers: a new acid-sensitive delivery vehicle for treating acute inflammatory diseases

Acute inflammatory diseases are a major cause of death in the world, and effective treatments are greatly needed. Macrophages play a central role in causing acute inflammatory diseases, and there is currently great interest in developing drug delivery vehicles that can target therapeutics to macrophages. Microparticles formulated from aliphatic polyketals have great potential to enhance the treatment of acute inflammatory diseases, due to their ability to passively target therapeutics to macrophages, their acid sensitivity, and their biocompatible degradation products. However, existing aliphatic polyketals are unsuitable for treating acute inflammatory diseases because they require weeks to hydrolyze, and strategies for accelerating their hydrolysis kinetics are greatly needed. In this report, we demonstrate that the hydrolysis kinetics of aliphatic polyketals can be accelerated by increasing their hydrophilic/hydrophobic balance. Aliphatic polyketals of varying hydrophobicity were synthesized, via the acetal exchange reaction, and their hydrolysis kinetics were investigated at the pH values of 4.5 and 7.4. A polyketal termed PK3 was developed, which had the hydrolysis kinetics suitable for treating acute inflammatory diseases. PK3 has a hydrolysis half-life of 2 days at pH 4.5, but requires several weeks to hydrolyze at pH 7.4. Microparticles were formulated with PK3, which encapsulated the anti-inflammatory drug, imatinib. In vivo experiments demonstrated that PK3 microparticles were able to significantly improve the efficacy of imatinib in treating acute liver failure. We anticipate that aliphatic polyketals will have numerous applications for the treatment of acute inflammatory diseases, given their pH sensitivity, tunable hydrolysis kinetics, and biocompatible degradation products.     

Combining ion pairing agents for enhanced analysis of oligonucleotide therapeutics by reversed phase-ion pairing ultra performance liquid chromatography (UPLC)

The burgeoning field of oligonucleotide therapeutics is based upon synthetically derived biopolymers comprised of relatively simple RNA and DNA building blocks. Significant gains in knowledge around mechanisms of action (RNA interference, RNA splicing, etc.) and oligonucleotide design (ASO, siRNA, DsiRNA, miRNA, locked nucleic acid, etc.) have been the main drivers of recent investment for this field [1,2]. As therapeutics, there is currently great interest in oligonucleotides due to the reduced time required to achieve lead molecules and to their potential for treating previously untractable diseases. One of the more challenging areas for the field of oligonucleotide therapeutics is the development of high-quality analysis schemes for the determination of purity in drug substance and product. This, in part, is due to the fact that the synthesis of oligonucleotides results in a significant number of closely related impurities that are not easily removed during purification [1]. As a result, these macromolecules (4000-8000 MW on average, depending on chain length) and their soup of closely related impurities are typically not well resolved from one another via conventional chromatographic approaches. One of the more common chromatographic techniques used for oligonucleotide analysis is reversed phase-ion pairing liquid chromatography (RP-IP). Our research led us to the discovery that the use of multiple ion pairing agents combined in the mobile phase can improve the overall chromatographic resolution and peak shape of the oligonucleotide analytes over the use of a single ion pairing agent alone, resulting in enhanced purity analysis and the opportunity to identify related impurities with greater certainty. In addition, the use of combined ion pairing agents allowed for the development of a "universal" method which has provided superior chromatography for several different oligonucleotide compounds and their related impurities regardless of differences in nucleotide sequence. The RP-IP UPLC method conditions are ESI-MS compatible and have allowed for the mass identification of five positional isomeric impurities chromatographically resolved and present at less than 1% of the nominal parent peak area.     

Translational research involving oxidative stress and diseases of aging

There is ample mounting evidence that reactive oxidant species are exacerbated in inflammatory processes, many pathological conditions, and underlying processes of chronic age-related diseases. Therefore there is increased expectation that therapeutics can be developed that act in some fashion to suppress reactive oxidant species and ameliorate the condition. This has turned out to be more difficult than at first expected. Developing therapeutics for indications in which reactive oxidant species are an important consideration presents some unique challenges. We discuss important questions including whether reactive oxidant species should be a therapeutic target, the need to recognize the fact that an antioxidant in a defined chemical system may be a poor antioxidant operationally in a biological system, and the importance of considering that reactive oxidant species may accompany the disease or pathological system rather than being a causative factor. We also discuss the value of having preclinical models to determine if the processes that are important in causing the disease under study are critically dependent on reactive oxidant species events and if the therapeutic under consideration quells these processes. In addition we discuss measures of success that must be met in commercial research and development and in preclinical and clinical trials and discuss as examples our translational research effort in developing nitrones for the treatment of acute ischemic stroke and as anti-cancer agents.     

Adult human neural stem cell therapeutics: Current developmental status and prospect

Over the past two decades, regenerative therapies using stem cell technologies have been developed for various neurological diseases. Although stem cell therapy is an attractive option to reverse neural tissue damage and to recover neurological deficits, it is still under development so as not to show significant treatment effects in clinical settings. In this review, we discuss the scientific and clinical basics of adult neural stem cells (aNSCs), and their current developmental status as cell therapeutics for neurological disease. Compared with other types of stem cells, aNSCs have clinical advantages, such as limited proliferation, inborn differentiation potential into functional neural cells, and no ethical issues. In spite of the merits of aNSCs, difficulties in the isolation from the normal brain, and in the in vitro expansion, have blocked preclinical and clinical study using aNSCs. However, several groups have recently developed novel techniques to isolate and expand aNSCs from normal adult brains, and showed successful applications of aNSCs to neurological diseases. With new technologies for aNSCs and their clinical strengths, previous hurdles in stem cell therapies for neurological diseases could be overcome, to realize clinically efficacious regenerative stem cell therapeutics.     

药物分子伴侣: 蛋白质折叠运输缺陷的新疗法

大量遗传性疾病的发生是由于基因突变引起蛋白质错误折叠而不能运输到作用位点,从而导致功能缺陷．近年来兴起的药物分子伴侣是恢复蛋白质折叠运输缺陷的新疗法,这类化合物一般为目的蛋白的底物类似物、受体配基或酶抑制剂等化学小分子,具细胞通透性,能在内质网中特异性识别并结合突变蛋白,校正并稳定其正确构象,协助其运输到正确位点,直接恢复突变蛋白功能,可治疗各种南蛋白质折叠运输缺陷导致的内分泌及代谢疾病．目前已报道的由药物分子伴侣恢复功能的突变蛋白主要为质膜蛋白及细胞器蛋白,如ATP结合盒转运蛋白、G-蛋白耦联受体及溶酶体酶等．大量的细胞及动物实验结果显示了药物分子伴侣的临床应用前景广阔,目前已有一例临床实验获得了成功．     

Reexamining assumptions about miRNA-guided gene silencing

MicroRNAs (miRNAs) are short endogenously expressed RNAs that have the potential to regulate the expression of any RNA. This potential has led to the publication of several thousand papers each year connecting miRNAs to many different genes and human diseases. By contrast, relatively few papers appear that investigate the molecular mechanism used by miRNAs. There is a disconnect between rigorous understanding of mechanism and the extraordinary diversity of reported roles for miRNAs. Consequences of this disconnect include confusion about the assumptions underlying the basic science of human miRNAs and slow development of therapeutics that target miRNAs. Here, we present an overview of investigations into miRNAs and their impact on gene expression. Progress in our understanding of miRNAs would be aided by a greater focus on the mechanism of miRNAs and a higher burden of evidence on researchers who seek to link expression of a particular miRNA to a biological phenotype.     

Development of membrane-active peptide therapeutics in oncology

Membrane-active peptides play an essential role in many living organisms and their immune systems and counter many infectious diseases. Many have dual or multiple mechanisms and can synergize with other molecules, like peptides, proteins, and small molecules. Although membrane-active peptides have been intensively studied in the past decades and more than 3500 sequences have been identified, only a few received approvals from the US Food and Drug Administration. In this review, we investigated all the peptide therapeutics that have entered the market or were subjected to preclinical and clinical studies to understand how they succeeded. With technological advancement (e.g., chemical modifications and pharmaceutical formulations) and a better understanding of the mechanism of action and the potential targets, we found at least five membrane-active peptide drugs that have entered preclinical/clinical phases and show promising results for cancer treatment. We summarized our findings in this review and provided insights into membrane-active anticancer peptide therapeutics.     

Impact of nanoparticles on amyloid β-induced Alzheimer’s disease,tuberculosis, leprosy and cancer: a systematic review

Nanotechnology is an interdisciplinary domain of science, technology and engineering that deals with nano-sized materials/particles. Usually, the size of nanoparticles lies between 1 and 100 nm. Due to their small size and large surface area-to-volume ratio, nanoparticles exhibit high reactivity, greater stability and adsorption capacity. These important physicochemical properties attract scientific community to utilize them in biomedical field. Various types of nanoparticles (inorganic and organic) have broad applications in medical field ranging from imaging to gene therapy. These are also effective drug carriers. In recent times, nanoparticles are utilized to circumvent different treatment limitations. For example, the ability of nanoparticles to cross the blood−brain barrier and having a certain degree of specificity towards amyloid deposits makes themselves important candidates for the treatment of Alzheimer’s disease. Furthermore, nanotechnology has been used extensively to overcome several pertinent issues like drug-resistance phenomenon, side effects of conventional drugs and targeted drug delivery issue in leprosy, tuberculosis and cancer. Thus, in this review, the application of different nanoparticles for the treatment of these four important diseases (Alzheimer’s disease, tuberculosis, leprosy and cancer) as well as for the effective delivery of drugs used in these diseases has been presented systematically. Although nanoformulations have many advantages over traditional therapeutics for treating these diseases, nanotoxicity is a major concern that has been discussed subsequently. Lastly, we have presented the promising future prospective of nanoparticles as alternative therapeutics. In that section, we have discussed about the futuristic approach(es) that could provide promising candidate(s) for the treatment of these four diseases.