Non-optical screening platforms: the next wave in label-free screening?

The use of optical biosensors for compound screening was first demonstrated in the mid-1990s, but there has been limited uptake in the market owing to issues of limited throughput and a lack of applications for key receptor classes. Recently, several start-up and established tools companies have exploited non-optical detection modalities that seek to address the shortcomings of more established optical approaches. Platforms based on acoustic resonance, electrical impedance, microcantilevers, nanowires and differential calorimetry are beginning to appear with commercially available products targeted at post-high-throughput screening hit confirmation and mode-of-action studies. This article highlights key advances in commercial label-free analysis platforms, which complement more traditional optical system and which also allow novel assay formats for the analysis of previously intractable targets.     

Whither high-throughput screening?

‘…today’s HTS will become the fulcrum that fully leverages genomics in drug discovery’     

Pharmacophore-based virtual screening versus docking-based virtual screening： a benchmark comparison against eight targets

Aim:

This study was conducted to compare the efficiencies of two virtual screening approaches, pharmacophore-based virtual screening (PBVS) and docking-based virtual screening (DBVS) methods.

Methods:

All virtual screens were performed on two data sets of small molecules with both actives and decoys against eight structurally diverse protein targets, namely angiotensin converting enzyme (ACE), acetylcholinesterase (AChE), androgen receptor (AR), D-alanyl-D-alanine carboxypeptidase (DacA), dihydrofolate reductase (DHFR), estrogen receptors α (ERα), HIV-1 protease (HIV-pr), and thymidine kinase (TK). Each pharmacophore model was constructed based on several X-ray structures of protein-ligand complexes. Virtual screens were performed using four screening standards, the program Catalyst for PBVS and three docking programs (DOCK, GOLD and Glide) for DBVS.

Results:

Of the sixteen sets of virtual screens (one target versus two testing databases), the enrichment factors of fourteen cases using the PBVS method were higher than those using DBVS methods. The average hit rates over the eight targets at 2% and 5% of the highest ranks of the entire databases for PBVS are much higher than those for DBVS.

Conclusion:

The PBVS method outperformed DBVS methods in retrieving actives from the databases in our tested targets, and is a powerful method in drug discovery.     

From screening criteria to colorectal cancer screening: what can New Zealand learn from other countries?

New Zealand is currently exploring how population-based colorectal cancer (CRC) screening will be implemented. The United Kingdom (UK), Australia, France, Italy, Spain, Finland, Denmark, the Netherlands, and Switzerland have conducted or are currently conducting pilot/feasibility studies. The UK, Australia, Finland, Canada, France and Italy are all in the early stages of implementing population-based CRC screening programmes. Most of these countries have lower CRC mortality rates than New Zealand. New Zealand is in a good position to learn from this overseas experience. Some of the key areas that will require careful consideration include; the best use of a population register to identify and invite eligible participants; the type of screening test to be used; ensuring adequate colonoscopy capacity; efficient and effective information systems; the management of high-risk groups; and how to ensure that all population groups benefit from screening.     

A pharmacy-based private chlamydia screening programme: results from the first 2?years of screening and treatment

Objective A major UK Pharmacy chain private Chlamydia screening and treatment service began in October 2006. People pay for a screening kit, send off a urine sample, and are informed of their result directly. Treatment is accessed via the pharmacy chain or the National Health Service. We analysed data from the first 2 years of the service to describe the positivity rate by age and gender, profile of users and to determine if the program succeeded in reaching those who are currently being missed in other clinical settings. Setting Three hundred and thirty-eight community pharmacies from a major pharmacy chain in England and Wales. Methods Cross sectional study of the first 2 years screening and treatment data. Data was collected on number of tests, test results, age and gender. Data was also collected on treatment uptake by age and gender. Further Data regarding the treatment service including the site, was collected on customer record forms. Positivity data was analysed using ??². Results A total of 14,378 private Chlamydia screening tests were performed in pharmacies during the 2 year period. Overall positivity rates in males (9.8%) were higher than females (6.8%). The positivity rate was significantly higher in the 16?C24 age group than in the 25 and over age group. A total of 533 people accessed and paid for treatment from Boots out of a total of 1,131 people who tested positive (47.1%). Hundred and thirty three (25.0%) partners also accessed treatment. Conclusions The data further supports the feasibility and acceptability of pharmacy testing and treatment.     

Virtual screening: are we there yet?

The cost of pharmaceutical development has increased dramatically in recent years, and many assorted approaches have been developed to decrease both the time and costs associated with bringing a drug to the market. Among these methods is the use of in silico screening of compound databases for potential new lead compounds, commonly referred to as virtual screening (VS). Virtual screening has become an integral part of the early discovery process in pharmaceutical development, readily observed by the large number of methodologies that have been published to date. Other reviews have been published detailing the various types of virtual screening methods in use. This work will review some of the virtual screening approaches and strategies that have been attempted to identify compounds to launch medicinal chemistry campaigns. Understanding trends and drivers in VS should help to set expectations about how and when VS could be used and what it can and cannot deliver and how it can be integrated in a successful screening campaign and used in a complementary fashion to HTS.     

Transcreener™: screening enzymes involved in covalent regulation

Enzymes that catalyse group transfer reactions comprise a significant fraction of the human proteome and are a rich source of drug targets because of their role in covalent regulatory cycles. Phosphorylation, glycosylation, sulfonation, methylation and acetylation represent some of the key types of group transfer reactions that modulate the function of diverse biomolecules through covalent modification. Development of high-throughput screening methods for these enzymes has been problematic because of the diversity of acceptor substrates. Recently, the authors developed a novel assay platform called Transcreener? that relies upon fluorescence detection of the invariant reaction product of a group transfer reaction, usually a nucleotide. This platform enables screening of any isoform in a family of group transfer enzymes, with any acceptor substrate, using the same assay reagents.     

Miniaturizing screening: how low can we go today?

Miniaturization in HTS is perceived as essential by pharmaceutical screening laboratories to accommodate the enormous increase in compounds and targets over the past few years. The two primary goals are to increase throughput while decreasing costs. However, although the desire is there, what is the reality of being able to achieve these goals?     

Is antenatal antibody screening worthwhile in the Zimbabwean population?

OBJECTIVES: To determine the incidence of clinically significant allo-antibodies in antenatal care (ANC) patients, and make recommendations on laboratory management of such cases in similar settings in Zimbabwe. DESIGN: A retrospective study. SETTING: Harare Central Hospital, a tertiary medical centre in Harare. SUBJECTS: Patients attending the ANC clinic at Harare Central Hospital. MAIN OUTCOME MEASURES: Blood group tests, allo-antibody screen, development of haemolytic disease of the newborn. RESULTS: 3,000 patients were grouped and screened and 96.7% were found to be Rhesus positive, 0.5% were Rhesus Du positive and 2.8% were Rhesus negative. An overall antibody incidence of 1.7% (n = 50) was obtained, 1.0% (n = 30) of which were strongly positive and 0.7% (n = 20) were so weakly positive so that no antibodies could be identified. Antibodies identified from those patients with strongly positive antibody screen were anti-D 13.3% (n = 4), anti-E 6.7% (n = 2), anti-Jsb 3.2% (n = 1), anti-Lea 23.3% (n = 7) and anti-Leb 20% (n = 6). Antibodies of unknown specificity were detected from 20% (n = 6) of the patients. Four (13.3%) of the specimens were insufficient for antibody identification. Clinical records of those patients with a strongly positive antibody screen were examined and anti-D and anti-Jsb were observed to have caused severe to fatal Haemolytic Disease of the Newborn (HDN). The four anti-D positive cases resulted in two still births and two jaundiced babies. The single anti-Jsb positive antibody case resulted in an intra-uterine death. Antibodies that are generally considered of no clinical significance did not cause HDN in this study. CONCLUSION: Anti-D remains the most important allo-antibody causing HDN, regardless of the availability of anti-D immunoglobulin for prophylaxis. Only Rhesus D negative women and those who have clinically significant antibodies need have repeat antibody screens during the rest of the pregnancy. In line with the current policy of screening all patients at booking, the policy on repeats is not clear and was not evident in this study.     

How can high-throughput screening deliver drugs to treat atherosclerosis?

Importance of the field: Atherosclerosis is a progressive disease that is characterized by the accumulation of lipid-rich plaques within the artery walls. Despite the past 3 decades witnessing the most significant advances in the pharmacotherapy of atherosclerosis with statins, atherosclerosis is still one of the leading causes of mortality in industrialized and developing nations. The applications of high-throughput screening (HTS) have retrieved hits and lead compounds which may be further developed to new promising therapeutics to achieve more effective reductions in the risk of cardiovascular morbidity and mortality.

Areas covered in this review: The review provides a summary of potential drug targets other than HMG-CoA reductase (primary target of statins) and their application in biochemical or cell-based HTS assays used by pharmaceutical companies and academic laboratories for anti-atherosclerotic drug discovery.

What the reader will gain: The reader will gain an overview of the HTS strategies currently used in the development of anti-atherosclerotic agents. The reader is also provided with some abortive examples in anti-atherosclerotic drug discovery as well as the associated limitations and challenges of the process that HTS delivers new drugs to treat atherosclerosis.

Take home message: HTS can assist in the efficient discovery of new drugs towards the potential targets involved in the progress of atherosclerosis.     

How can high-throughput screening deliver drugs to treat atherosclerosis?

Importance of the field: Atherosclerosis is a progressive disease that is characterized by the accumulation of lipid-rich plaques within the artery walls. Despite the past 3 decades witnessing the most significant advances in the pharmacotherapy of atherosclerosis with statins, atherosclerosis is still one of the leading causes of mortality in industrialized and developing nations. The applications of high-throughput screening (HTS) have retrieved hits and lead compounds which may be further developed to new promising therapeutics to achieve more effective reductions in the risk of cardiovascular morbidity and mortality. Areas covered in this review: The review provides a summary of potential drug targets other than HMG-CoA reductase (primary target of statins) and their application in biochemical or cell-based HTS assays used by pharmaceutical companies and academic laboratories for anti-atherosclerotic drug discovery. What the reader will gain: The reader will gain an overview of the HTS strategies currently used in the development of anti-atherosclerotic agents. The reader is also provided with some abortive examples in anti-atherosclerotic drug discovery as well as the associated limitations and challenges of the process that HTS delivers new drugs to treat atherosclerosis. Take home message: HTS can assist in the efficient discovery of new drugs towards the potential targets involved in the progress of atherosclerosis.     

Tubulin inhibitors： pharmacophore modeling,virtua screening and molecular docking

Aim： To construct a quantitative pharmacophore model of tubulin inhibitors and to discovery new leads with potent antitumor activities. Methods： Ligand-based pharmacophore modeling was used to identify the chemical features responsible for inhibiting tubulin polymerization. A set of 26 training compounds was used to generate hypothetical pharmacophores using the HypoGen algorithm. The structures were further validated using the test set, Fischer randomization method, leave-one-out method and a decoy set, and the best model was chosen to screen the Specs database. Hit compounds were subjected to molecular docking study using a Molecular Operating Environment （MOE） software and to biological evaluation in vitro. Results： Hypol was demonstrated to be the best pharmacophore model that exhibited the highest correlation coefficient （0.9582）, largest cost difference （70.905） and lowest RMSD value （0.6977）. Hypol consisted of one hydrogen-bond acceptor, a hydrogen-bond donor, a hydrophobic feature, a ring aromatic feature and three excluded volumes. Hypol was validated with four different methods and had a goodness-of-hit score of 0.81. When Hypol was used in virtual screening of the Specs database, 952 drug-like compounds were revealed. After docking into the colchicine-binding site of tubulin, 5 drug-like compounds with the required interaction with the critical amino acid residues and the binding free energies 〈-4 kcal/mol were selected as representative leads. Compounds 1 and 3 exhibited inhibitory activity against MCF-7 human breast cancer cells in vitro. Conclusion： Hypol is a quantitative pharmacophore model for tubulin inhibitors, which not only provides a better understanding of their interaction with tubulin, but also assists in discovering new potential leads with antitumor activities.     

Synthesis, anticonvulsant and toxicity screening of thiazolyl�Cthiadiazole derivatives

Various thiazole-substituted thiadiazole derivatives (7a–t) were designed and synthesized using substituted acetophenones and substituted anilines as starting materials. Thiazole and thiadiazole moieties being anticonvulsants were clubbed together to get the titled compounds and their in vivo anticonvulsant screening were performed by two most adopted seizure models, maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ). Three compounds 7i, 7l and 7n were found to be potent in both the screens with comparable ED₅₀ and better TD₅₀ values than some standard drugs. These compounds were also found to exert lesser toxic effects on liver.