Showing papers in "Nature Reviews Drug Discovery in 2011"
TL;DR: It is timely to review the science underpinning the amyloid cascade hypothesis, consider what type of clinical trials will constitute a valid test of this hypothesis and explore whether amyloids-β-directed therapeutics will provide the medicines that are urgently needed by society for treating this devastating disease.
Abstract: The amyloid cascade hypothesis, which posits that the deposition of the amyloid-β peptide in the brain is a central event in Alzheimer's disease pathology, has dominated research for the past twenty years. Several therapeutics that were purported to reduce amyloid-β production or aggregation have failed in Phase III clinical testing, and many others are in various stages of development. Therefore, it is timely to review the science underpinning the amyloid cascade hypothesis, consider what type of clinical trials will constitute a valid test of this hypothesis and explore whether amyloid-β-directed therapeutics will provide the medicines that are urgently needed by society for treating this devastating disease.
1,897 citations
TL;DR: It is postulate that a target-centric approach for first-in-class drugs, without consideration of an optimal MMOA, may contribute to the current high attrition rates and low productivity in pharmaceutical research and development.
Abstract: Preclinical strategies that are used to identify potential drug candidates include target-based screening, phenotypic screening, modification of natural substances and biologic-based approaches. To investigate whether some strategies have been more successful than others in the discovery of new drugs, we analysed the discovery strategies and the molecular mechanism of action (MMOA) for new molecular entities and new biologics that were approved by the US Food and Drug Administration between 1999 and 2008. Out of the 259 agents that were approved, 75 were first-in-class drugs with new MMOAs, and out of these, 50 (67%) were small molecules and 25 (33%) were biologics. The results also show that the contribution of phenotypic screening to the discovery of first-in-class small-molecule drugs exceeded that of target-based approaches — with 28 and 17 of these drugs coming from the two approaches, respectively — in an era in which the major focus was on target-based approaches. We postulate that a target-centric approach for first-in-class drugs, without consideration of an optimal MMOA, may contribute to the current high attrition rates and low productivity in pharmaceutical research and development.
1,552 citations
TL;DR: It is indicated that the limitations of the predictivity of disease models and also that the validity of the targets being investigated is frequently questionable, which is a crucial issue to address if success rates in clinical trials are to be improved.
Abstract: 1. This indicates the limitations of the predictivity of disease models and also that the validity of the targets being investigated is frequently questionable, which is a crucial issue to address if success rates in clinical trials are to be improved. Candidate drug targets in industry are derived from various sources, including inhouse target identification campaigns, inlicensing and public sourcing, in particular based on reports published in the literature and presented at conferences. During the transfer of projects from an academic to a company setting, the focus changes from ‘interesting’ to ‘feasible/marketable’, and the financial costs of pursuing a full-blown drug discovery and development programme for a particular target could ultimately be hundreds of millions of Euros. Even in the earlier stages, investments in activities such as high-throughput screening programmes are substantial, and thus the validity of published data on potential targets is crucial for companies when deciding to start novel projects. To mitigate some of the risks of such investments ultimately being wasted, most pharmaceutical companies run in-house target validation programmes. However, validation projects that were started in our company based on exciting published data have often resulted in disillusionment when key data could not be reproduced. Talking to scientists, both in academia and in industry, there seems to be a general impression that many
1,549 citations
TL;DR: The evidence for G-quadruplexes in gene promoters is described and their potential as therapeutic targets are discussed, as well as progress in the development of strategies to harness this potential through intervention with small-molecule ligands.
Abstract: G-quadruplexes are four-stranded DNA structures that are over-represented in gene promoter regions and are viewed as emerging therapeutic targets in oncology, as transcriptional repression of oncogenes through stabilization of these structures could be a novel anticancer strategy. Many gene promoter G-quadruplexes have physicochemical properties and structural characteristics that might make them druggable, and their structural diversity suggests that a high degree of selectivity might be possible. Here, we describe the evidence for G-quadruplexes in gene promoters and discuss their potential as therapeutic targets, as well as progress in the development of strategies to harness this potential through intervention with small-molecule ligands.
1,420 citations
TL;DR: Preclinical and initial clinical evidence reveal that normalization of the vascular abnormalities is emerging as a complementary therapeutic paradigm for cancer and other vascular disorders, which affect more than half a billion people worldwide.
Abstract: Despite having an abundant number of vessels, tumours are usually hypoxic and nutrient-deprived because their vessels malfunction. Such abnormal milieu can fuel disease progression and resistance to treatment. Traditional anti-angiogenesis strategies attempt to reduce the tumour vascular supply, but their success is restricted by insufficient efficacy or development of resistance. Preclinical and initial clinical evidence reveal that normalization of the vascular abnormalities is emerging as a complementary therapeutic paradigm for cancer and other vascular disorders, which affect more than half a billion people worldwide. Here, we discuss the mechanisms, benefits, limitations and possible clinical translation of vessel normalization for cancer and other angiogenic disorders.
1,385 citations
TL;DR: The prevalence and pharmacological advantages of covalent drugs are surveyed, how potential risks and challenges may be addressed through innovative design, and the broad opportunities provided by targeted covalENT inhibitors are presented.
Abstract: Covalent drugs have proved to be successful therapies for various indications, but largely owing to safety concerns, they are rarely considered when initiating a target-directed drug discovery project. There is a need to reassess this important class of drugs, and to reconcile the discordance between the historic success of covalent drugs and the reluctance of most drug discovery teams to include them in their armamentarium. This review surveys the prevalence and pharmacological advantages of covalent drugs, discusses how potential risks and challenges may be addressed through innovative design, and presents the broad opportunities provided by targeted covalent inhibitors.
1,363 citations
TL;DR: Key pH regulators in tumour cells include: isoforms 2, 9 and 12 of carbonic anhydrase, isoforms of anion exchangers, Na+/HCO3− co-transporters, Na+./H+ exchanger, monocarboxylate transporters and the vacuolar ATPase.
Abstract: The high metabolic rate of tumours often leads to acidosis and hypoxia in poorly perfused regions. Tumour cells have thus evolved the ability to function in a more acidic environment than normal cells. Key pH regulators in tumour cells include: isoforms 2, 9 and 12 of carbonic anhydrase, isoforms of anion exchangers, Na+/HCO3- co-transporters, Na+/H+ exchangers, monocarboxylate transporters and the vacuolar ATPase. Both small molecules and antibodies targeting these pH regulators are currently at various stages of clinical development. These antitumour mechanisms are not exploited by the classical cancer drugs and therefore represent a new anticancer drug discovery strategy.
1,331 citations
TL;DR: Research into how changes in cell metabolism promote tumour growth has accelerated in recent years, and efforts to target metabolic dependencies of cancer cells as a selective anticancer strategy have refocused.
Abstract: Genetic events in cancer activate signalling pathways that alter cell metabolism. Clinical evidence has linked cell metabolism with cancer outcomes. Together, these observations have raised interest in targeting metabolic enzymes for cancer therapy, but they have also raised concerns that these therapies would have unacceptable effects on normal cells. However, some of the first cancer therapies that were developed target the specific metabolic needs of cancer cells and remain effective agents in the clinic today. Research into how changes in cell metabolism promote tumour growth has accelerated in recent years. This has refocused efforts to target metabolic dependencies of cancer cells as a selective anticancer strategy.
1,198 citations
TL;DR: Here, a review of the natural drug delivery carriers that have provided the basis and inspiration for new drug delivery systems is reviewed.
Abstract: The exploitation of natural particulates, such as pathogens and mammalian cells, for drug delivery applications is a rapidly emerging field. Here, Yoo and colleagues discuss recent advances in the design of drug carriers based on natural particulates, provide an overview of their current development status and highlight the various applications and limitations of each approach.
1,050 citations
TL;DR: The case for the use of HTS as part of a proven scientific tool kit, the wider use of which is essential for the discovery of new chemotypes is presented.
Abstract: High-throughput screening (HTS) has been postulated in several quarters to be a contributory factor to the decline in productivity in the pharmaceutical industry. Moreover, it has been blamed for stifling the creativity that drug discovery demands. In this article, we aim to dispel these myths and present the case for the use of HTS as part of a proven scientific tool kit, the wider use of which is essential for the discovery of new chemotypes.
1,023 citations
TL;DR: A new generation of ATP-competitive inhibitors that directly target the mTOR catalytic site display potent and comprehensive mTOR inhibition and are in early clinical trials.
Abstract: Mammalian target of rapamycin (mTOR) is an atypical protein kinase that controls growth and metabolism in response to nutrients, growth factors and cellular energy levels, and it is frequently dysregulated in cancer and metabolic disorders. Rapamycin is an allosteric inhibitor of mTOR, and was approved as an immuno-suppressant in 1999. In recent years, interest has focused on its potential as an anticancer drug. However, the performance of rapamycin and its analogues (rapalogues) has been undistinguished despite isolated successes in subsets of cancer, suggesting that the full therapeutic potential of targeting mTOR has yet to be exploited. A new generation of ATP-competitive inhibitors that directly target the mTOR catalytic site display potent and comprehensive mTOR inhibition and are in early clinical trials.
TL;DR: The concept that compared to the use of conventional antioxidants, inhibiting NOX1 and NOX2 oxidases is a superior approach for combating oxidative stress is advanced.
Abstract: NADPH oxidases are a family of enzymes that generate reactive oxygen species (ROS). The NOX1 (NADPH oxidase 1) and NOX2 oxidases are the major sources of ROS in the artery wall in conditions such as hypertension, hypercholesterolaemia, diabetes and ageing, and so they are important contributors to the oxidative stress, endothelial dysfunction and vascular inflammation that underlies arterial remodelling and atherogenesis. In this Review, we advance the concept that compared to the use of conventional antioxidants, inhibiting NOX1 and NOX2 oxidases is a superior approach for combating oxidative stress. We briefly describe some common and emerging putative NADPH oxidase inhibitors. In addition, we highlight the crucial role of the NADPH oxidase regulatory subunit, p47phox, in the activity of vascular NOX1 and NOX2 oxidases, and suggest how a better understanding of its specific molecular interactions may enable the development of novel isoform-selective drugs to prevent or treat cardiovascular diseases.
TL;DR: This study examines the decline of R&D productivity in pharmaceuticals in the past two decades and shows that this decline is associated with an increasing concentration ofR&D investments in areas in which the risk of failure is high, which correspond to unmet therapeutic needs and unexploited biological mechanisms.
Abstract: Advances in the understanding of the molecular basis of diseases have expanded the number of plausible therapeutic targets for the development of innovative agents in recent decades. However, although investment in pharmaceutical research and development (R&D) has increased substantially in this time, the lack of a corresponding increase in the output in terms of new drugs being approved indicates that therapeutic innovation has become more challenging. Here, using a large database that contains information on R&D projects for more than 28,000 compounds investigated since 1990, we examine the decline of R&D productivity in pharmaceuticals in the past two decades and its determinants. We show that this decline is associated with an increasing concentration of R&D investments in areas in which the risk of failure is high, which correspond to unmet therapeutic needs and unexploited biological mechanisms. We also investigate the potential variations in productivity with regard to the regional location of companies and find that although companies based in the United States and Europe differ in the composition of their R&D portfolios, there is no evidence of any productivity gap.
TL;DR: The drugs that were approved by the US Food and Drug Administration during the past three decades are analysed and the interactions of these drugs with therapeutic targets that are encoded by the human genome are examined, using the DrugBank database and extensive manual curation.
Abstract: The discovery and exploitation of new drug targets is a key focus for both the pharmaceutical industry and academic biomedical research. To provide an insight into trends in the exploitation of new drug targets, we have analysed the drugs that were approved by the US Food and Drug Administration during the past three decades and examined the interactions of these drugs with therapeutic targets that are encoded by the human genome, using the DrugBank database and extensive manual curation. We have identified 435 effect-mediating drug targets in the human genome, which are modulated by 989 unique drugs, through 2,242 drug-target interactions. We also analyse trends in the introduction of drugs that modulate previously unexploited targets, and discuss the network pharmacology of the drugs in our data set.
TL;DR: The current understanding and future directions in BDNF-related research in the central nervous system are reviewed, with an emphasis on the possible therapeutic application of BDNF in modifying fundamental processes underlying neural disease.
Abstract: The growth factor brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase receptor type B (TRKB) are actively produced and trafficked in multiple regions in the adult brain, where they influence neuronal activity, function and survival throughout life. The diverse presence and activity of BDNF suggests a potential role for this molecule in the pathogenesis and treatment of both neurological and psychiatric disorders. This article reviews the current understanding and future directions in BDNF-related research in the central nervous system, with an emphasis on the possible therapeutic application of BDNF in modifying fundamental processes underlying neural disease.
TL;DR: This work reviews recent findings that present unexpected opportunities to interfere with major tumorigenic signals by manipulating GPCR-mediated pathways and discusses current data regarding novel G PCR targets that may provide promising opportunities for drug discovery in cancer prevention and treatment.
Abstract: G protein-coupled receptors (GPCRs) belong to a superfamily of cell surface signalling proteins that have a pivotal role in many physiological functions and in multiple diseases, including the development of cancer and cancer metastasis. Current drugs that target GPCRs - many of which have excellent therapeutic benefits - are directed towards only a few GPCR members. Therefore, huge efforts are currently underway to develop new GPCR-based drugs, particularly for cancer. We review recent findings that present unexpected opportunities to interfere with major tumorigenic signals by manipulating GPCR-mediated pathways. We also discuss current data regarding novel GPCR targets that may provide promising opportunities for drug discovery in cancer prevention and treatment.
TL;DR: The identification of separable key functions of GABAA receptor subtypes suggests that receptor subtype-selective compounds could overcome the limitations of classical benzodiazepines; furthermore, they might be valuable for novel indications such as chronic pain, depression, schizophrenia, cognitive enhancement and stroke.
Abstract: The identification of physiological and pharmacological functions of GABAA (γ-aminobutyric acid, type A) receptor subtypes has renewed the interest in the GABAA receptor system as a target for the development of non-sedating anxiolytics, as well as of drugs for indications that are distinct from those of classical benzodiazepines, such as analgesia, schizophrenia and depression.
TL;DR: Well-conducted Phase II clinical trials provide the data required to determine whether there is a case to be made, both scientifically and commercially, for progressing a drug candidate into Phase III trials, but results are lower than at any other phase of development.
Abstract: Well-conducted Phase II clinical trials provide the data required to determine whether there is a case to be made, both scientifically and commercially, for progressing a drug candidate into Phase III trials. At present, however, Phase II success rates are lower than at any other phase of development. Analysis by the Centre for Medicines Research (CMR) of projects from a group of 16 companies (representing approximately 60% of global RD 2011), the overall attrition of late-stage drug development seems to be unsustainably high.
TL;DR: The biology of CCN proteins, their roles in various pathologies and their potential as therapeutic targets are summarized.
Abstract: Members of the CCN family of matricellular proteins are crucial for embryonic development and have important roles in inflammation, wound healing and injury repair in adulthood. Deregulation of CCN protein expression or activities contributes to the pathobiology of various diseases — many of which may arise when inflammation or tissue injury becomes chronic — including fibrosis, atherosclerosis, arthritis and cancer, as well as diabetic nephropathy and retinopathy. Emerging studies indicate that targeting CCN protein expression or signalling pathways holds promise in the development of diagnostics and therapeutics for such diseases. This Review summarizes the biology of CCN proteins, their roles in various pathologies and their potential as therapeutic targets.
TL;DR: Approaches to accurately quantify distinct cell death pathways are described, their advantages and pitfalls are discussed, and those techniques that are amenable to HTS are focused on.
Abstract: Cell death has an important role in many human diseases, and strategies aimed at modulating the associated pathways have been successfully applied to treat various disorders. Indeed, several clinically promising cytotoxic and cytoprotective agents with potential applications in cancer, ischaemic and neurodegenerative diseases have recently been identified by high-throughput screening (HTS), based on appropriate cell death assays. Given that different cell death modalities may be dysregulated in different diseases, it is becoming increasingly clear that such assays need to not only quantify the extent of cell death, but they must also be able to distinguish between the various pathways. Here, we systematically describe approaches to accurately quantify distinct cell death pathways, discuss their advantages and pitfalls, and focus on those techniques that are amenable to HTS.
TL;DR: This Review focuses on recent developments in the TRP channel-related field, and highlights potential opportunities for therapeutic intervention.
Abstract: Transient receptor potential (TRP) cation channels have been among the most aggressively pursued drug targets over the past few years. Although the initial focus of research was on TRP channels that are expressed by nociceptors, there has been an upsurge in the amount of research that implicates TRP channels in other areas of physiology and pathophysiology, including the skin, bladder and pulmonary systems. In addition, mutations in genes encoding TRP channels are the cause of several inherited diseases that affect a variety of systems including the renal, skeletal and nervous system. This Review focuses on recent developments in the TRP channel-related field, and highlights potential opportunities for therapeutic intervention.
TL;DR: Recent advances in understanding the role of some of these enzymes are highlighted and how these new insights may be the key to developing novel therapeutics for diseases including immuno-inflammatory disorders, cancer, infectious diseases, cardiovascular disease and neurodegenerative disorders.
Abstract: The ubiquitin-proteasome system (UPS) and ubiquitin-like protein (UBL) conjugation pathways are integral to cellular protein homeostasis. The growing recognition of the fundamental importance of these pathways to normal cell function and in disease has prompted an in-depth search for small-molecule inhibitors that selectively block the function of these pathways. However, our limited understanding of the molecular mechanisms and biological consequences of UBL conjugation is a significant hurdle to identifying drug-like inhibitors of enzyme targets within these pathways. Here, we highlight recent advances in understanding the role of some of these enzymes and how these new insights may be the key to developing novel therapeutics for diseases including immuno-inflammatory disorders, cancer, infectious diseases, cardiovascular disease and neurodegenerative disorders.
TL;DR: How iPSCs are being exploited to illuminate disease pathophysiology, identify novel drug targets and enhance the probability of clinical success of new drugs is discussed.
Abstract: The ability to generate induced pluripotent stem cells (iPSCs) from patients, and an increasingly refined capacity to differentiate these iPSCs into disease-relevant cell types, promises a new paradigm in drug development - one that positions human disease pathophysiology at the core of preclinical drug discovery. Disease models derived from iPSCs that manifest cellular disease phenotypes have been established for several monogenic diseases, but iPSCs can likewise be used for phenotype-based drug screens in complex diseases for which the underlying genetic mechanism is unknown. Here, we highlight recent advances as well as limitations in the use of iPSC technology for modelling a 'disease in a dish' and for testing compounds against human disease phenotypes in vitro. We discuss how iPSCs are being exploited to illuminate disease pathophysiology, identify novel drug targets and enhance the probability of clinical success of new drugs.
TL;DR: An assessment of the current approaches used for the evaluation of chemically reactive metabolites and how these approaches are being used within the pharmaceutical industry to assess and minimize the potential of drug candidates to cause toxicity is presented.
Abstract: The normal metabolism of drugs can generate metabolites that have intrinsic chemical reactivity towards cellular molecules, and therefore have the potential to alter biological function and initiate serious adverse drug reactions. Here, we present an assessment of the current approaches used for the evaluation of chemically reactive metabolites. We also describe how these approaches are being used within the pharmaceutical industry to assess and minimize the potential of drug candidates to cause toxicity. At early stages of drug discovery, iteration between medicinal chemistry and drug metabolism can eliminate perceived reactive metabolite-mediated chemical liabilities without compromising pharmacological activity or the need for extensive safety evaluation beyond standard practices. In the future, reactive metabolite evaluation may also be useful during clinical development for improving clinical risk assessment and risk management. Currently, there remains a huge gap in our understanding of the basic mechanisms that underlie chemical stress-mediated adverse reactions in humans. This Review summarizes our views on this complex topic, and includes insights into practices considered by the pharmaceutical industry.
Centre national de la recherche scientifique1, University of Bordeaux2, Michael J. Fox Foundation3, German Center for Neurodegenerative Diseases4, Rush University Medical Center5, Toronto Western Hospital6, Imperial College London7, University of Navarra8, French Institute of Health and Medical Research9, University College London10, University of Cambridge11, Merck Serono12
TL;DR: This Review describes the most promising biological targets and therapeutic agents that are currently being assessed to address treatment goals of Parkinson's disease.
Abstract: The loss of dopaminergic neurons in the substantia nigra pars compacta leads to the characteristic motor symptoms of Parkinson's disease: bradykinesia, rigidity and resting tremors. Although these symptoms can be improved using currently available dopamine replacement strategies, there is still a need to improve current strategies of treating these symptoms, together with a need to alleviate non-motor symptoms of the disease. Moreover, treatments that provide neuroprotection and/or disease-modifying effects remain an urgent unmet clinical need. This Review describes the most promising biological targets and therapeutic agents that are currently being assessed to address these treatment goals. Progress will rely on understanding genetic mutations or susceptibility factors that lead to Parkinson's disease, better translation between preclinical animal models and clinical research, and improving the design of future clinical trials.
TL;DR: Key findings include: first, that oral drugs seldom possess nanomolar potency; second, that many oral drugs have considerable off-target activity; and third, that in vitro potency does not correlate strongly with the therapeutic dose.
Abstract: A common underlying assumption in current drug discovery strategies is that compounds with higher in vitro potency at their target(s) have greater potential to translate into successful, low-dose therapeutics. This has led to the development of screening cascades with in vitro potency embedded as an early filter. However, this approach is beginning to be questioned, given the bias in physicochemical properties that it can introduce early in lead generation and optimization, which is due to the often diametrically opposed relationship between physicochemical parameters associated with high in vitro potency and those associated with desirable absorption, distribution, metabolism, excretion and toxicity (ADMET) characteristics. Here, we describe analyses that probe these issues further using the ChEMBL database, which includes more than 500,000 drug discovery and marketed oral drug compounds. Key findings include: first, that oral drugs seldom possess nanomolar potency (50 nM on average); second, that many oral drugs have considerable off-target activity; and third, that in vitro potency does not correlate strongly with the therapeutic dose. These findings suggest that the perceived benefit of high in vitro potency may be negated by poorer ADMET properties.
TL;DR: The recent positive results of clinical trials with novel immunoactive drugs as well as the unexpected finding of a positive interaction between immunotherapy and chemotherapy may herald a new era for the immunotherapy of cancer.
Abstract: Our insight into antitumour immune responses has increased considerably during the past decades, yet the development of immunotherapy as a treatment modality for cancer has been hampered by several factors. These include difficulties in the selection of the optimal dose and schedule, the methods of evaluation, and financial support. Although durable clinical remissions have been observed with various immunotherapeutic strategies, the percentage of patients who benefited from these interventions has remained too small to justify the general use of such strategies. However, the recent positive results of clinical trials with novel immunoactive drugs as well as the unexpected finding of a positive interaction between immunotherapy and chemotherapy may herald a new era for the immunotherapy of cancer.
TL;DR: This Review elaborates on nanoparticle-targeting concepts in Atherosclerotic disease, provides an overview of the use of nanomedicine in atherosclerosis, and discusses potential future applications and clinical benefits.
Abstract: The use of nanotechnology for medical purposes — nanomedicine — has grown exponentially over the past few decades. This is exemplified by the US Food and Drug Administration's approval of several nanotherapies for various conditions, as well as the funding of nanomedical programmes worldwide. Although originally the domain of anticancer therapy, recent advances have illustrated the considerable potential of nanomedicine in the diagnosis and treatment of atherosclerosis. This Review elaborates on nanoparticle-targeting concepts in atherosclerotic disease, provides an overview of the use of nanomedicine in atherosclerosis, and discusses potential future applications and clinical benefits.
TL;DR: It is hoped that a thorough understanding of the mechanisms underlying cardiotoxicity will lead to the development of safe, effective drugs and consequently, fewer costly surprises as agents progress through clinical trials.
Abstract: Targeted therapeutics, particularly those that inhibit the activity of protein kinases that are mutated and/or overexpressed in cancer, have revolutionized the treatment of some cancers and improved survival rates in many others. Although these agents dominate drug development in cancer, significant toxicities, including cardiotoxicity, have emerged. In this Review, we examine the underlying mechanisms that result in on-target or off-target cardiotoxicities of small molecule kinase inhibitors. We also discuss how well the various preclinical safety models and strategies might predict clinical cardiotoxicity. It is hoped that a thorough understanding of the mechanisms underlying cardiotoxicity will lead to the development of safe, effective drugs and consequently, fewer costly surprises as agents progress through clinical trials.