HIV-1 integrase inhibitors: 2005-2006 update

HIV-1 integrase (IN) catalyzes the integration of proviral DNA into the host genome, an essential step for viral replication. Inhibition of IN catalytic activity provides an attractive strategy for antiretroviral drug design. Currently two IN inhibitors, MK-0518 and GS-9137, are in advanced stages of human clinical trials. The IN inhibitors in clinical evaluation demonstrate excellent antiretroviral efficacy alone or in combination regimens as compared to previously used clinical antiretroviral agents in naive and treatment-experienced HIV-1 infected patients. However, the emergence of viral strains resistant to clinically studied IN inhibitors and the dynamic nature of the HIV-1 genome demand a continued effort toward the discovery of novel inhibitors to keep a therapeutic advantage over the virus. Continued efforts in the field have resulted in the discovery of compounds from diverse chemical classes. In this review, we provide a comprehensive report of all IN inhibitors discovered in the years 2005 and 2006.     

HIV‐1 integrase inhibitors: 2007–2008 update

In recent years, HIV‐1 integrase (IN) has become an attractive target for designing antiretroviral agents. The first IN inhibitor approved for clinical use, raltegravir, has validated the pharmacological viability of IN inhibitors and signals the advent of a new generation of antiretroviral drugs. The development of raltegravir and other successful lead IN inhibitors has also influenced the IN inhibitor design strategy. This has led to the identification of several potent inhibitors in these last two years. Further, an increased understanding of IN structural biology has opened up novel approaches to inhibiting IN, such as targeting its multimerization or interaction with cellular cofactors. This review covers recent developments in the field of IN inhibitor design from 2007 to 2008. © 2010 Wiley Periodicals, Inc. Med Res Rev, 30, No. 6, 890–954, 2010     

Dolutegravir for the treatment of adult patients with HIV-1 infection

Dolutegravir, is a second generation integrase inhibitor that had recently received United States Food and Drug Administration and European Commission approval for the treatment of adult patients with HIV-1 infection. Dolutegravir provides distinct advantages compared with first generation integrase inhibitors. Unlike raltegravir, dolutegravir can be given once daily for patients who are antiretroviral treatment naïve. Once-a-day dolutegravir dosing also does not require a pharmacokinetic booster like elvitegravir which minimizes the drug-drug interaction potential of dolutegravir. In Phase III clinical trials, dolutegravir-containing regimens have demonstrated either non-inferiority or superiority to current first line agents such as raltegravir, darunavir/ritonavir, and efavirenz containing regimens. Moreover, dolutegravir may be effective for patients with a history of raltegravir and/or elvitegravir resistance. Dolutegravir will likely play a major role in the management of patients with HIV-1 infection, and will be aided when coformulation with abacavir/lamivudine as a single pill, once-daily regimen is available.     

Discovery of cytochrome P450 1B1 inhibitors as new promising anti-cancer agents

Human cytochrome P450 (CYP)1B1 is a major enzyme for carcinogenic estrogen metabolism and involved in the metabolic activation of procarcinogens of the polycyclic aromatic hydrocarbons (PAHs). CYP1B1 is known to be expressed at a high frequency in various human cancers, but not in normal tissues. It also plays an important role in the metabolism of various anti-cancer drugs. These findings suggest inhibition of CYP1B1 as a new oncological therapeutic strategy. Several natural and synthetic compounds have been studied in an effort to find the isoform-specific inhibitors of the CYP1 subfamily. A survey of the inhibitors of CYP1B1 and other related inhibitors of the CYP1 subfamily is provided in this review.     

Nonsteroidal aromatase inhibitors: recent advances

Aromatase is the cytochrome P450 enzyme responsible for the last step of estrogen biosynthesis, and aromatase inhibitors constitute an important class of drugs in clinical use for the treatment of breast cancer. Nonsteroidal aromatase inhibitors (NSAIs) are competitive inhibitors of aromatase, which bind to the enzyme active site by coordinating the iron atom present in the heme group of the P450 protein. Presently, third generation NSAIs are in use, and research efforts are being carried out both to identify new molecules of therapeutic interest and to clarify the mechanism of action. In this article, we present a survey of the compounds that have been recently reported as NSAIs, to provide a broad view on the general structure-activity relationships of the class. Moreover, starting from the current knowledge of the mechanistic aspects of aromatase action and from recent theoretical work on the molecular modeling of both enzyme and inhibitors, we try to indicate a way to integrate these different studies in view of a more general understanding of the aromeatase-inhibitor system. Finally, some aspects regarding the possible future development of the field are considered briefly.     

Proton pump inhibitors: update on their role in acid-related gastrointestinal diseases

Gastric acid is pathogenic in many gastrointestinal disorders, such as gastroesophageal reflux disease and peptic ulcer disease. Proton pump inhibitors (PPIs) are the antisecretory drugs of choice for serious acid-related conditions. Ample recent data exist to explicate virtually every aspect of the clinical management of acid-peptic disorders with PPIs. Although all PPIs are effective, there are some differences in their clinical performance, particularly in terms of the degree and speed of gastric acid suppression. Rapid onset of acid suppression may be particularly relevant to newer approaches, such as 'on-demand' or intermittent therapy for non-erosive reflux disease and shorter regimens for Helicobacter pylori eradication. New data, in addition, highlight differences in PPI metabolism that may both affect efficacy and predispose patients to drug-drug interactions. PPI selection should involve the awareness of these issues.     

Targeting COPD: advances on low‐molecular‐weight inhibitors of human neutrophil elastase

Chronic obstructive pulmonary disease (COPD) is a major increasing health problem and the World Health Organization (WHO) reports COPD as the fifth leading cause of death worldwide. COPD refers to a condition of inflammation and progressive weakening of the structure of the lung as well as irreversible narrowing of the airways. Current treatment is only palliative and no available drug halts the progression of the disease. Human neutrophil elastase (HNE) is a serine protease, which plays a major role in the COPD inflammatory process. The protease/anti‐protease imbalance leads to an excess of extracellular HNE hydrolyzing elastin, the structural protein that confers elasticity to the lung tissue. Although HNE was identified as a therapeutic target for COPD more than 30 years ago, only Sivelestat (ONO‐5046), an HNE inhibitor from Ono Pharmaceutical, has been approved for clinical use. Nevertheless, Sivelestat is only approved in Japan and its development in the USA was terminated in 2003. Other inhibitors in pre‐clinical or phase I trials were discontinued for various reasons. Hence, there is an urgent need for low‐molecular‐weight synthetic elastase inhibitors and the present review discusses the recent advances on this field covering acylating agents, transition‐state inhibitors, mechanism‐based inhibitors, relevant natural products, and major patent disclosures.     

Gastrointestinal safety of coxibs: systematic review and meta‐analysis of observational studies on selective inhibitors of cyclo‐oxygenase 2

Prior meta‐analyses have shown a higher gastrointestinal risk of nonselective NSAIDs versus placebo and a lower gastrointestinal risk of coxibs versus nonselective NSAIDs. However, the available data about gastrointestinal risk for coxibs versus placebo are scarce. The aim of this study was to review the current evidence on the use of coxibs and to evaluate the risk of gastrointestinal adverse outcomes (GAO) associated with coxibs versus nonexposed. Search was conducted on PubMed and Embase databases. We selected cohort observational, case‐control, nested case‐control and case‐crossover studies that reported the risk of GAO associated with coxibs versus nonexposed as relative risk (RR), odds ratio (OR), hazard ratio (HR) or incidence rate ratio (IRR). It was estimated the pooled RR and the 95% confidence interval (CI) for coxibs both individually and as a whole by the DerSimonian and Laird method. Twenty‐eight studies met inclusion criteria. Overall, coxibs were associated with a significant increment in the risk of GAO [RR 1.64 (95% CI 1.44–1.86)]. The analysis by individual drugs showed that etoricoxib [RR 4.85 (95% CI 2.64–8.93)] presented the highest gastrointestinal risk, followed by rofecoxib [RR 2.02 (95% CI 1.56–2.61)] and celecoxib [RR 1.53 (95% CI 1.19–1.97)]. Gastrointestinal risk was also high for the subgroups aged <65 years and low‐dose coxibs. The use of coxibs is associated with a statistically significant increased risk of GAO, which would be high even for low‐dose coxibs and <65‐year‐old subgroups. The risk would be higher for etoricoxib than for celecoxib and rofecoxib.     

COX‐1 Inhibitors: Beyond Structure Toward Therapy

Biosynthesis of prostaglandins from arachidonic acid (AA) is catalyzed by cyclooxygenase (COX), which exists as COX‐1 and COX‐2. AA is in turn released from the cell membrane upon neopathological stimuli. COX inhibitors interfere in this catalytic and disease onset process. The recent prominent discovery involvements of COX‐1 are mainly in cancer and inflammation. Five classes of COX‐1 inhibitors are known up to now and this classification is based on chemical features of both synthetic compounds and substances from natural sources. Physicochemical interactions identification between such molecules and COX‐1 active site was achieved through X‐ray, mutagenesis experiments, specific assays and docking investigations, as well as through a pharmacometric predictive model building. All these insights allowed the design of new highly selective COX‐1 inhibitors to be tested into those disease models in which COX‐1 is involved. Particularly, COX‐1 is expressed at high levels in the early to advanced stages of human epithelial ovarian cancer, and it also seems to play a pivotal role in cancer progression. The refinement of COX‐1 selective inhibitor structure has progressed to the stage that some of the inhibitors described in this review could be considered as promising active principle ingredients of drugs and hence part of specific therapeutic protocols. This review aims to outline achievements, in the last 5 years, dealing with the identification of highly selective synthetic and from plant extracts COX‐1 inhibitors and their theranostic use in neuroinflammation and ovarian cancer. Their gastrotoxic effect is also discussed.     

Hypoxia‐inducible factor‐1 (HIF‐1) inhibitors from the last decade (2007 to 2016): A “structure–activity relationship” perspective

Tumor hypoxia is a common feature in most solid tumors and is associated with overexpression of the hypoxia response pathway. Overexpression of the hypoxia‐inducible factor (HIF‐1) protein leads to angiogenesis, metastasis, apoptosis resistance, and many other pro‐tumorigenic responses in cancer development. HIF‐1 is a promising target in cancer drug development to increase the patient's response to chemotherapy and radiotherapy as well as the survival rate of cancer patients. Since up to 1% of genes are hypoxia‐sensitive, a target‐specific HIF‐1 inhibitor may be a better clinical candidate in cancer drug discovery. Though no HIF‐1 inhibitor is clinically available to date, a lot of effort has been applied during the last decade in search of potent HIF‐1 inhibitors. In this review, we will summarize the structure–activity relationship of ten different chemotypes reported to be HIF‐1 inhibitors in the last decade (2007–2016), their mechanisms of action for HIF‐1 inhibition, progress in the way of target‐specific inhibitors, and problems associated with current inhibitors. It is anticipated that the results of these research on the medicinal chemistry of HIF‐1 inhibitors will provide decent information in the design and development of future inhibitors.