Redox activation of metal-based prodrugs as a strategy for drug delivery

This review provides an overview of metal-based anticancer drugs and drug candidates. In particular, we focus on metal complexes that can be activated in the reducing environment of cancer cells, thus serving as prodrugs. There are many reports of Pt and Ru complexes as redox-activatable drug candidates, but other d-block elements with variable oxidation states have a similar potential to serve as prodrugs in this manner. In this context are compounds based on Fe, Co, or Cu chemistry, which are also covered. A trend in the field of medicinal inorganic chemistry has been toward molecularly targeted, metal-based drugs obtained by functionalizing complexes with biologically active ligands. Another recent activity is the use of nanomaterials for drug delivery, exploiting passive targeting of tumors with nano-sized constructs made from Au, Fe, carbon, or organic polymers. Although complexes of all of the above mentioned metals will be described, this review focuses primarily on Pt compounds, including constructs containing nanomaterials.     

Peptide-mediated delivery of therapeutic and imaging agents into mammalian cells

Modern molecular targeting provides new opportunities for imaging, diagnosis and treatment of diseases. Small molecular weight peptides have the potential for enhancing targeting of compounds, and they may also have therapeutic effects by themselves. The limiting step for successful molecular targeting is the development of efficient peptide delivery systems. This review will focus on peptides developed by phage display and combinatorial chemistry for the delivery of pharmaceuticals, radioactive compounds and gene expression vectors. Target cell-specific delivery can be improved by peptides that penetrate the cell membrane or alternatively induce receptor-mediated endocytosis. In addition, peptides that contain endosomal escape signals or nuclear localization motifs may help trafficking of therapeutics to appropriate locations inside the cell. Small molecule radiolabelled peptides are the preferred agents for targeting and for diagnostic imaging of various organs as they are easily synthesized, effectively penetrate tissues, and are rapidly cleared from the circulation. Such peptides have been tested in animals and humans in the fields of cancer, cardiology, neurology, inflammation/infection, atherosclerosis and thrombosis.     

基于糖基化修饰非铂类抗肿瘤制剂研究进展

铂类药物是众多恶性肿瘤的重要治疗药物之一,但靶向性弱,毒副作用强;与铂类金属药物相比,部分非铂类金属化合物前期研究展现出良好的抗肿瘤活性和较低的毒性。近期研究表明,糖基化金属化合物不但提高了化合物的靶向性,还可进一步降低毒性,并且还展现出除抗肿瘤以外的其他药用价值,如杀菌、抗病毒、抗疟疾等。鉴于此,本文尝试总结近年非铂类糖基金属化合物的研究进展,并对目前糖基金属类化合物存在的问题进行了分析与展望,期望为非铂类抗肿瘤制剂的研发提供借鉴。     

Structural approaches to obtain kinase selectivity

One of the grand challenges in kinase drug discovery is the design of small-molecule inhibitors with selectivity profiles that will ultimately be efficacious in the clinic. Current medicinal chemistry strategies make heavy use of structural, biophysical and computational approaches to achieve this multi-faceted goal. Here we review structure-based approaches underlying the development of several molecules that are currently in clinical trials, including the cMet inhibitor ARQ197 and the Bcr-Abl inhibitor ponatinib. We highlight the challenge posed by the emergence of resistance mutants and discuss promising lead generation strategies to obtain selective inhibitors of protein and lipid kinases such as targeting of specific sites, the use of fragment-based approaches and new chemical probes based on metal complexes.     

Chelating agents and their use in radiopharmaceutical sciences

Radiometal nuclides can serve as diagnostic markers in molecular imaging or can be used in therapeutic settings for a rising number of human afflictions. For the targeted delivery of these medically interesting ions, appropriate chelating agents forming stable complexes are of fundamental importance. For different metal ions exhibiting different physical and chemical properties, resulting in different coordination chemistries and therefore differing requirements on the chelator used, a broad variety of chelating agents has been developed over the years. Not only the chemical properties of the metal ion determine the choice of the chelator, but also the desired in vivo behavior of the resulting molecular imaging or therapeutic compound influences the choice of the complexation agent. Furthermore, the conjugation chemistry for the introduction of the chelator into the biologically active compound and the complexation reaction of the metal ion can affect the choice of the appropriate chelator. This review outlines chelating agents used in medicinal chemistry, their radiometal complexation behavior and their potential influence on the properties of the resulting drugs.     

Radiolabeled compounds in diagnosis of infectious and inflammatory disease

Nuclear medicine offers powerful noninvasive techniques for visualization of infectious and inflammatory disorders using whole body imaging enabling the determination of both localization and number of inflammatory foci. A wide variety of approaches depicting the different stages of the inflammatory response have been developed. Non-specific radiolabeled compounds, such as 67Ga-citrate and radiolabeled polyclonal human immunoglobulin accumulate in inflammatory foci due to enhanced vascular permeability. Specific accumulation of radiolabeled compounds in inflammatory lesions results from binding to activated endothelium (e.g. radiolabeled anti-E-selectin), the enhanced influx of leukocytes (e.g. radiolabeled autologous leukocytes, anti-granulocyte antibodies or cytokines), the enhanced glucose-uptake by activated leukocytes (18F-fluorodeoxyglucose) or direct binding to micro-organisms (e.g. radiolabeled ciprofloxacin or antimicrobial peptides). Scintigraphy using autologous leukocytes, labeled with 111In or 99mTc, is still considered the "gold standard" nuclear medicine technique for the imaging of infection and inflammation, but the range of radiolabeled compounds available for this indication is still expanding. Recently, positron emission tomography with 18F-fluorodeoxyglucose has been shown to delineate various infectious and inflammatory disorders with high sensitivity. New developments in peptide chemistry and in radiochemistry will result in specific agents with high specific activity. A gradual shift from non-specific, cumbersome or even hazardous approaches to more sophisticated, specific approaches is ongoing. In this review, the different approaches to scintigraphic imaging of infection and inflammation, already in use or under investigation, are discussed.     

Furans, thiophenes and related heterocycles in drug discovery

The five-membered aromatic heterocycles containing oxygen and sulfur are key building blocks used in medicinal chemistry applications. Furans, thiophenes and related azole analogs constitute an important class of compounds that are readily available, stable and easily functionalized. In this review, the authors survey the recent literature and highlight the application of such compounds in the development of therapeutic agents. This review focuses on two major strategies involving these compounds. The first is the use of these rings as intact scaffolds within the final target compound, and the second is the use of these compounds as convenient and flexible synthons for non-aromatic structural moieties.     

Targeted multimodal imaging modalities

Molecular imaging non-invasively visualizes and characterizes the biologic functions and mechanisms in living organisms at a molecular level. In recent years, advances in imaging instruments, imaging probes, assay methods, and quantification techniques have enabled more refined and reliable images for more accurate diagnoses. Multimodal imaging combines two or more imaging modalities into one system to produce details in clinical diagnostic imaging that are more precise than conventional imaging. Multimodal imaging offers complementary advantages: high spatial resolution, soft tissue contrast, and biological information on the molecular level with high sensitivity. However, combining all modalities into a single imaging probe involves problems yet to be solved due to the requirement of high dose contrast agents for a component of imaging modality with low sensitivity. The introduction of targeting moieties into the probes enhances the specific binding of targeted multimodal imaging modalities and selective accumulation of the imaging agents at a disease site to provide more accurate diagnoses. An extensive list of prior reports on the targeted multimodal imaging probes categorized by each modality is presented and discussed. In addition to accurate diagnosis, targeted multimodal imaging agents carrying therapeutic medications make it possible to visualize the theranostic effect and the progress of disease. This will facilitate the development of an imaging-guided therapy, which will widen the application of the targeted multimodal imaging field to experiments in vivo.     

Comprehensive Review in Current Developments of Benzimidazole‐Based Medicinal Chemistry

The properties of benzimidazole and its derivatives have been studied over more than one hundred years. Benzimidazole derivatives are useful intermediates/subunits for the development of molecules of pharmaceutical or biological interest. Substituted benzimidazole derivatives have found applications in diverse therapeutic areas such as antiulcer, anticancer agents, and anthelmintic species to name just a few. This work systematically gives a comprehensive review in current developments of benzimidazole‐based compounds in the whole range of medicinal chemistry as anticancer, antibacterial, antifungal, anti‐inflammatory, analgesic agents, anti‐HIV, antioxidant, anticonvulsant, antitubercular, antidiabetic, antileishmanial, antihistaminic, antimalarial agents, and other medicinal agents. This review will further be helpful for the researcher on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole drugs/compounds.     

The role of medicinal chemistry in drug research

Classical medicinal chemistry, that is molecular modifications of existing bioactive compounds, leading to me-too drugs with value added and often to me-too drugs which will never reach the market or to drugs in another pharmacological field than that originally intended, will be with us for a long time to come. The ultimate goal, however, is of course rational or at least semi-rational drug design. In some instances this goal seems to have already been reached as in the case of angiotensin-converting enzyme inhibitors and H₂ antagonists. In the (near) future results from the steady progress in molecular biology in combination with computer-assisted drug modelling — possibly coupled with artificial intelligence techniques — will help the medicinal chemist in his efforts to attain this goal.     

Recent researches in triazole compounds as medicinal drugs

Triazole compounds containing three nitrogen atoms in the five-membered aromatic azole ring are readily able to bind with a variety of enzymes and receptors in biological system via diverse non-covalent interactions, and thus display versatile biological activities. The related researches in triazole-based derivatives as medicinal drugs have been an extremely active topic, and numerous excellent achievements have been acquired. Noticeably, a large number of triazole compounds as clinical drugs or candidates have been frequently employed for the treatment of various types of diseases, which have shown their large development value and wide potential as medicinal agents. This work systematically reviewed the recent researches and developments of the whole range of triazole compounds as medicinal drugs, including antifungal, anticancer, antibacterial, antitubercular, antiviral, anti-inflammatory and analgesic, anticonvulsant, antiparasitic, antidiabetic, anti-obesitic, antihistaminic, anti-neuropathic, antihypertensive as well as other biological activities. The perspectives of the foreseeable future in the research and development of triazole-based compounds as medicinal drugs are also presented. It is hoped that this review will serve as a stimulant for new thoughts in the quest for rational designs of more active and less toxic triazole medicinal drugs.     

Novel compounds to combat trypanosomatid infections: a medicinal chemical perspective

INTRODUCTION: The current therapeutic arsenal against the kinetoplastids Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. is clearly inadequate and underscores the urgent need to develop new effective, safe and cost-effective drugs. AREAS COVERED: Accordingly, this review of patented products and processes using anti-kinetoplastid agents provides insight into the identification of novel or more refined drugs. In this review, we describe products developed in recent years for the treatment of human African trypanosomiasis, American trypanosomiasis and leishmaniasis from a medicinal chemical perspective. EXPERT OPINION: Applications so far have looked only superficially for candidate anti-trypanosomatid drugs and are deficient in the final stages of drug development studies, i.e., tolerance/safety, selectivity, drug-resistance, scaling-up, pharmacokinetic and pharmacodynamic assays. The ultimate goal for production of agents with anti-HAT activity has been the development of dicationic agents with parasite DNA-binding activity. Another goal for control of human African trypanosomiasis as well as for Chagas disease and leishmaniasis is the development of protease inhibitors. It should also be noted that several recent studies describing promising targets and compounds have not yet been patented. An effort should be made by foundations, international health organizations and pharmaceutical corporations to support analysis and development of promising new chemotherapeutic agents for controlling the trypanosomiasis and leishmaniasis.     

Finding the sweet spot: the role of nature and nurture in medicinal chemistry

Given its position at the heart of small-molecule drug discovery, medicinal chemistry has an important role in tackling the well-known productivity challenges in pharmaceutical research and development. In recent years, extensive analyses of successful and failed discovery compounds and drug candidates have improved our understanding of the role of physicochemical properties in drug attrition. Based on the clarified challenges in finding the 'sweet spot' in medicinal chemistry programmes, we suggest that this goal can be achieved through a combination of first identifying chemical starting points with appropriate 'nature' and then rigorously 'nurturing' them during lead optimization. Here, we discuss scientific, strategic, organizational and cultural considerations for medicinal chemistry practices, with the aim of promoting more effective use of what is already known, as well as a wider appreciation of the risks of pursuing suboptimal compounds.     

Target-based anticancer indole derivatives and insight into structure‒activity relationship: A mechanistic review update (2018–2021)

Cancer, which is the uncontrolled growth of cells, is the second leading cause of death after heart disease. Targeting drugs, especially to specific genes and proteins involved in growth and survival of cancer cells, is the prime need of research world-wide. Indole moiety, which is a combination of aromatic-heterocyclic compounds, is a constructive scaffold for the development of novel leads. Owing to its bioavailability, high unique chemical properties and significant pharmacological behaviours, indole is considered as the most inquisitive scaffold for anticancer drug research. This is illustrated by the fact that the U.S. Food and Drug Administration (FDA) has recently approved several indole-based anticancer agents such as panobinostat, alectinib, sunitinib, osimertinib, anlotinib and nintedanib for clinical use. Furthermore, hundreds of studies on the synthesis and activity of the indole ring have been published in the last three years. Taking into account the facts stated above, we have presented the most recent advances in medicinal chemistry of indole derivatives, encompassing hot articles published between 2018 and 2021 in anticancer drug research. The recent advances made towards the synthesis of promising indole-based anticancer compounds that may act via various targets such as topoisomerase, tubulin, apoptosis, aromatase, kinases, etc., have been discussed. This review also summarizes some of the recent efficient green chemical synthesis for indole rings using various catalysts for the period during 2018–2021. The review also covers the synthesis, structure?activity relationship, and mechanism by which these leads have demonstrated improved and promising anticancer activity. Indole molecules under clinical and preclinical stages are classified into groups based on their cancer targets and presented in tabular form, along with their mechanism of action. The goal of this review article is to point the way for medicinal chemists to design and develop effective indole-based anticancer agents.     

Ruthenium complexes as anticancer agents

Cancer is one of the major cases of death in the world. Current treatment of cancer is limited to surgery, radiotherapy, and the use of cytotoxic agents, despite their well known side effects and problems associated with the development of resistance. For most forms of disseminated cancer, however, no curative therapy is available, and the discovery and development of novel active chemotherapeutic agents is largely needed. Since the development of cisplatin, an inorganic platinum complex, numerous platinum and non-platinum metal complexes were synthesized and tested for anticancer activity. Very few match the clinical efficacy of cisplatin. Ruthenium complexes were prepared to ameliorate cisplatin activity, particularly on resistant tumours, or to reduce host toxicity at active doses. Since many years a lot of scientific groups have actively worked in the field of inorganic antitumor drugs and have developed a number of Ru(II) and Ru(III) complexes, which were shown to possess good antitumor and, above all, antimetastatic properties against animal models. Ruthenium complexes are presently an object of great attention in the field of medicinal chemistry, as antitumor agents with selective antimetastatic properties and low systemic toxicity. Ruthenium compounds appear to penetrate reasonably well the tumor cells and bind effectively to DNA. In this review, the achievements in the field of medicinal chemistry, DNA binding modes, and the development status of Ru(II) and Ru(III) complexes as anticancer agents are discussed. The aim of this review is therefore that of critically examining the past and the actual work on ruthenium compounds with emphasis on their proposed role in cancer therapy.     

Palladacycles as antimicrobial agents

This review article deals with the structure activity relationship (SAR) for a variety of palladacycles in biomedical applications. Moreover, the types of antibacterial, antifungal, antimycobacterial and antiprotozoal (antiamoebic and antitrypanosomal) activities will vary considerably from one country to another. Therefore, all efforts will be required to face such a vast diversity of problems. This study gives an up to date overview of the antibacterial, antifungal, antimycobacterial and antiprotozoal chemistry of the palladium group elements with an emphasis on the new strategies used in the development of new antibacterial agents. Methodologies for application of bulky aromatic or aliphatic nitrogen ligands, chiral organic moieties, chelates containing other donor atoms than nitrogen, and biologically active ligands in the design of agents analogous to palladacycles are presented. Therefore, the use of palladacycles in medicinal chemistry is interesting as potential application in the biological properties with less toxic drugs compounds..     

Molecules of Natural Origin, Semi-synthesis and Synthesis with Anti-Inflammatory and Anticancer Utilities

The development of new drugs that can be valuable for the evolution of diseases' treatment is a goal for different areas of research, namely natural products chemistry, molecular biology and biochemistry, pharmacology, medicinal chemistry, synthetic organic chemistry and analytical chemistry. Nature is the main source of compounds for pharmaceutical purposes, either by providing the natural organic chemical compounds of interest or as a source of inspiration for the design of new drugs. The known anti-inflammatory and anticancer agents belong to a great diversity of structural skeletons since inflammatory and cancer processes involve many different biological targets. Their origins extend to plants, fungi, bacteria, and marine organisms, besides those produced by semi-synthesis and total synthesis. The tasks of the organic chemist are the screening, the structure assignment, and the semi and total syntheses of active molecules. Herein the screening and assignment of new active structures is addressed, together with other aspects, namely the improvements, both in availability and in effectiveness of action that can be achieved from new derivatives by synthetic or semi-synthetic strategies. Some aspects of drug delivery of anti-inflammatory and anticancer agents are considered. The bibliography presented is far from being exhaustive due to the prodigious number of published works. Instead, the most significant contributions in the scope of this review are described. The active compounds are organised by their biosynthetic origins as terpenoids; macrolides, polyketides and ansamycins; phenolics; alkaloids; peptides; glycoconjugates; other compounds, and food compounds.     

Magnetic nanoparticles in MR imaging and drug delivery

Magnetic nanoparticles (MNPs) possess unique magnetic properties and the ability to function at the cellular and molecular level of biological interactions making them an attractive platform as contrast agents for magnetic resonance imaging (MRI) and as carriers for drug delivery. Recent advances in nanotechnology have improved the ability to specifically tailor the features and properties of MNPs for these biomedical applications. To better address specific clinical needs, MNPs with higher magnetic moments, non-fouling surfaces, and increased functionalities are now being developed for applications in the detection, diagnosis, and treatment of malignant tumors, cardiovascular disease, and neurological disease. Through the incorporation of highly specific targeting agents and other functional ligands, such as fluorophores and permeation enhancers, the applicability and efficacy of these MNPs have greatly increased. This review provides a background on applications of MNPs as MR imaging contrast agents and as carriers for drug delivery and an overview of the recent developments in this area of research.