Targeting cancer: the challenges and successes of structure-based drug design against the human purinome

Purine-binding proteins are of critical importance to all living organisms. Approximately 13% of the human genome is devoted to coding for purine-binding proteins. Given their importance, purine-binding proteins are attractive targets for chemotherapeutic intervention against a variety of disease states, particularly cancer. Modern computational and biophysical techniques, combined together in a structure-based drug design approach, aid immensely in the discovery of inhibitors of these targets. This review covers the process of modern structure-based drug design and gives examples of its use in discovery and development of drugs that target purine-binding proteins. The targets reviewed are human purine nucleoside phosphorylase, human epidermal growth factor receptor kinase, and human kinesin spindle protein.     

Drugs, their targets and the nature and number of drug targets

What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.     

Proteins, drug targets and the mechanisms they control: the simple truth about complex networks

Realizing the promise of molecularly targeted inhibitors for cancer therapy will require a new level of knowledge about how a drug target is wired into the control circuitry of a complex cellular network. Here we review general homeostatic principles of cellular networks that enable the cell to be resilient in the face of molecular perturbations, while at the same time being sensitive to subtle input signals. Insights into such mechanisms may facilitate the development of combination therapies that take advantage of the cellular control circuitry, with the aim of achieving higher efficacy at a lower drug dosage and with a reduced probability of drug-resistance development.     

The role of ABC transporters in drug resistance, metabolism and toxicity

ATP Binding Cassette (ABC) transporters form a special family of membrane proteins, characterized by homologous ATP-binding, and large, multispanning transmembrane domains. Several members of this family are primary active transporters, which significantly modulate the absorption, metabolism, cellular effectivity and toxicity of pharmacological agents. This review provides a general overview of the human ABC transporters, their expression, localization and basic mechanism of action. Then we shortly deal with the human ABC transporters as targets of therapeutic interventions in medicine, including cancer drug resistance, lipid and other metabolic disorders, and even gene therapy applications. We place a special emphasis on the three major groups of ABC transporters involved in cancer multidrug resistance (MDR). These are the classical P-glycoprotein (MDR1, ABCB1), the multidrug resistance associated proteins (MRPs, in the ABCC subfamily), and the ABCG2 protein, an ABC half-transporter. All these proteins catalyze an ATP-dependent active transport of chemically unrelated compounds, including anticancer drugs. MDR1 (P-glycoprotein) and ABCG2 preferentially extrude large hydrophobic, positively charged molecules, while the members of the MRP family can extrude both hydrophobic uncharged molecules and water-soluble anionic compounds. Based on the physiological expression and role of these transporters, we provide examples for their role in Absorption-Distribution-Metabolism-Excretion (ADME) and toxicology, and describe several basic assays which can be applied for screening drug interactions with ABC transporters in the course of drug research and development.     

The role of absorption,distribution, metabolism,excretion and toxicity in drug discovery

Major reasons preventing many early candidates reaching market are the inappropriate ADME (absorption, distribution, metabolism and excretion) properties and drug-induced toxicity. From a commercial perspective, it is desirable that poorly behaved compounds are removed early in the discovery phase rather than during the more costly drug development phases. As a consequence, over the past decade, ADME and toxicity (ADMET) screening studies have been incorporated earlier in the drug discovery phase. The intent of this review is to introduce the desirable attributes of a new chemical entity (NCE) to the medicinal chemist from an ADMET perspective. Fundamental concepts, key tools, reagents and experimental approaches used by the drug metabolism scientist to aid a modern project team in predicting human pharmacokinetics and assessing the "drug-like" molecule are discussed.     

New targets, new hope: novel drug targets for curbing malaria

Malaria continues to plague the tropical and subtropical regions causing high morbidity and mortality. Every year, millions die due to lack of affordable and effective anti-malarial drugs. Malaria poses significant threat to half of the world's population and our arsenal to combat this disease is nearly empty. Pharmaceutical companies shy away from investing in research and development for anti-malarial drugs and have shunned it as non-profitable venture. In wake of emergence and spread of drug resistant malaria to newer territories, there is imperative need to develop new drugs for curbing malaria. This underscores the need of exploring new drug targets and reevaluation of existing drug targets. Availability of genome sequence of both parasite and human host has greatly facilitated the search for novel drug targets. This endeavor is complemented well by advances in functional genomics, structure - based drug design and high throughput screening methods and raises much optimism about winning this battle against malaria. This review discusses potential drug targets in the malarial parasite for designing intervention strategies and suitable chemotherapeutic agents.     

神经痛的药物作用靶点及其机制

目的对近年来出现的治疗神经痛的药物作用靶点及其机制作以综述。方法在查阅30篇文献的基础上,对神经痛的治疗靶点进行整理和归纳。结果目前治疗神经痛的药物作用靶点主要有5-羟色胺受体、去甲肾上腺素受体、阿片受体、大麻素受体、离子通道、免疫相关物质等等。以这些靶点设计的药物均已证明可在一定程度上缓解神经痛。结论为进一步开发治疗神经痛的靶向药物提供参考。     

Evaluation and validation of drug targets

Drug target is one of the key factors for discovering and developing new drugs. To find and validate drug targets is a crucial technique required in drug discovery by the strategy of high throughput screening. Based on the knowledge of molecular biology, human genomics and proteomics, it has been predicted that 5000 to 10000 drug targets exist in human. So, it is important orocedure to evaluate and validate the drug targets.     

Cancer research 2001: drug resistance, new targets and drug combinations.

The development of new anticancer drugs and the identification of novel targets represent major focus areas for pharmaceutical and biotech companies, universities and research institutes worldwide. The 92nd Annual Meeting of the American Association for Cancer Research (AACR) provided a glimpse of the latest developments in the cancer field. We highlight here presentations on resistance mechanisms (efflux, target modulation), new targets and drugs in development (topoisomerase, angiogenesis, cell cycle inhibitors) and new molecular technologies. The emergence of technologies for concurrently screening for expression of thousands of genes, has provided a new approach for the identification of molecular targets and mechanisms of both action and resistance of new compounds. The importance of inhibiting multiple targets simultaneously was brought up in several presentations.     

The size and mix of government spending on illicit drug policy in Australia

Aim . To estimate how much governments in Australia spend on reducing and dealing with illicit drug problems. Methods . Government documents and supplementary information sources were used to estimate drug‐related expenditure for the financial year 2002–03, in Australian dollars. Public sector expenditure on reducing drug problems (‘proactive expenditure’) was classified into four policy functions: prevention, treatment, harm reduction and enforcement. Expenditure related to the consequences of drug use (‘reactive expenditure’) was included as a separate category. Results . Spending by Australian governments in financial year 2002–03 on all drug‐related activities was estimated to be $3.2 billion. Proactive expenditure was estimated to be $1.3 billion, comprising 55% on enforcement, 23% on prevention, 17% on treatment, 3% on harm reduction and 1% on activities that span several of these functions. Expenditure on dealing with the consequences of drug use was estimated to be $1.9 billion, with the majority the result of crime‐related consequences. Conclusion . Several insights result from estimating these expenditures. First, law enforcement is the largest drug policy component, with Australian governments also spending significant amounts on treatment and prevention programmes. Secondly, apart from the prevention component, Australia's drug policy mix is strikingly similar to recent international estimates. Finally, expenditures associated with dealing with the consequences of illicit drugs are large and important for assessing drug‐related public sector expenditure.     

Metalworking fluid--the toxicity of a complex mixture

Various chemicals are used in the manufacture of cooling and lubricating fluids and fall into the classes of straight, soluble, semisynthetic, and synthetic metalworking fluids. The diversity of chemicals and in-use contaminants makes the risk assessment of metalworking fluids quite difficult. Toxicologists have used a number of methods to evaluate the component(s) responsible for the adverse pulmonary effects of metal working fluid aerosols encountered in the workplace. Although investigators have studied the adverse effects of metalworking fluid chemicals alone and in combination, the majority of evidence strongly suggests that the microbial changes that occur in fluid composition, during use and storage in the workplace, are responsible for the pulmonary effects reported for workers exposed to metalworking fluid aerosols. This review discusses the methodologies used to examine the toxicity of the complex nature of modern metalworking fluids and the findings that point toward bacterial endotoxin as a major contributor to their adverse effects.     

Immunological effects of iron oxide nanoparticles and iron-based complex drug formulations: Therapeutic benefits,toxicity, mechanistic insights,and translational considerations

Nanotechnology offers several advantages for drug delivery. However, there is the need for addressing potential safety concerns regarding the adverse health effects of these unique materials. Some such effects may occur due to undesirable interactions between nanoparticles and the immune system, and they may include hypersensitivity reactions, immunosuppression, and immunostimulation. While strategies, models, and approaches for studying the immunological safety of various engineered nanoparticles, including metal oxides, have been covered in the current literature, little attention has been given to the interactions between iron oxide-based nanomaterials and various components of the immune system. Here we provide a comprehensive review of studies investigating the effects of iron oxides and iron-based nanoparticles on various types of immune cells, highlight current gaps in the understanding of the structure–activity relationships of these materials, and propose a framework for capturing their immunotoxicity to streamline comparative studies between various types of iron-based formulations.     

Preparation and toxicity evaluation of a novel nattokinase-tauroursodeoxycholate complex

Nattokinase (NK), which has been identified as a potent fibrinolytic protease, has remarkable potential in treatment of thrombolysis, and even has the ability to ameliorate chronic vein thrombosis. To reduce the hemorrhagic risk from an intravenous injection of NK, nattokinase-tauroursodeoxycholate (NK-TUDCA) complex was prepared at different pH values and with different ratios of NK and TUDCA. When assessing survival time, survival state, tail injury, and the body weight of mice, it was found that the NK-TUDCA complex (NK: 10 kIU/ml; TUDCA: 10 mg/ml; pH 5.0) had a lower toxicity when administered at an NK dosage of 130 kIU/kg in the acute toxicity test and 13 kIU/kg in the repeated low-dose challenge. From the results of the in vitro thrombolytic test and characterization of NK-TUDCA, we speculated that the delayed release of NK-TUDCA might be the main cause of toxicity reduction by the complex. This study described the preparation of an NK complex with low toxicity following intravenous administration, which could be utilized for further clinical study of NK.     

Innovative cancer drug targets: genomics,transcriptomics and clinomics

In men, gonadal function is affected in a slow, progressive way as part of the normal ageing process. Recently, however, significant interest has developed on the importance of this condition, which is variously known as male climacteric, andropause or, more appropriately, androgen decline in the ageing male (ADAM). The term andropause is biologically wrong and clinically inappropriate but, it adequately conveys the concept of emotional and physical changes that, although related to ageing in general, are also associated with significant hormonal alterations. The inappropriateness of the term is based on the fact that in women, the reproductive cycle invariably ends with ovarian failure. In men, this process is not universal and when it occurs it is normally subtle in its clinical manifestations. This has led to a tendency to ignore the syndrome as an unavoidable and untreatable result of the ageing process. For the sake of simplicity and directness, this review will use the terms ADAM and andropause to denote the global hormonal alterations associated with ageing.