T cells play a critical role in maintaining the normal function of the adaptive immune response, with their dysfunction resulting in a variety of autoimmune and immunodeficiency diseases. Efficient and accurate detection of T cell function is therefore crucial to clinical diagnosis and development of immunomodulators. A variety of in vitro cellular systems are currently employed for analyzing T cell activation, yet all suffer from some combination of low throughput, unnatural conditions and long assay times. Label-free technologies are capable of detecting phenotypic responses to treatments under physiological conditions, thereby potentially accelerating drug discovery by facilitating the use of disease-relevant cell models for functional assessment and clinical diagnosis. The xCELLigence system is an impedance based label-free platform that allows for dynamic monitoring of subtle morphological and adhesive changes in cells, such as those induced during T cell activation. Here we describe the development and validation of a T cell activation assay based upon electrical impedance. Co-activation of Jurkat cells with anti-CD28 and anti-CD3 functional antibodies led to impedance changes that were rapidly and sensitively recorded (within 30 minutes). This phenomenon was also observed in human peripheral blood mononuclear cells. These changes reflect morphological and adhesive alterations correlated with cytoskeletal reorganization as verified by microscopy. They were functionally dependent on canonical T cell signaling pathways, including calcium-mediated signals and Src family kinases because relevant inhibitors impaired T cell activation. Our results provide a convenient approach to measure T cell activation in real-time and to elucidate the underlying mechanisms of action through probing with small molecules.

A novel cyclobutane class of nonpeptidic glucagon-like peptide-1 (GLP-1) receptor agonists, exemplified by 3, was identified using receptor binding and multiple response element/cAMP response element (MRE/CRE)-driven reporter gene assays. The structures of 3 and its three isomers were elucidated by NMR, HRESIMS, and X-ray crystallography. A series of structural modifications were also made based on the core structure of 3 with different substitution groups at the west and east ends. Among these analogues, compound 16 was found to be 4- to 5-fold more potent than 3 both in vitro and in vivo.

β-Cell injury plays an important role in the development of type 1 and type 2 diabetes. Most of the β-cell bioassays depend on labeling or endpoint assessments that might not capture the true physiology or pathology of the injury process. In the current study, we dynamically detected a broad range of pathological and pharmacological responses to four toxicants (cytokine mixture, free fatty acid mixture, streptozotocin, and hydrogen peroxide) in living β-cells (INS-1E and MIN6) by a label-free, cell-based assay system named xCELLigence, codeveloped by ACEA Biosciences and Roche Diagnostics. Our results suggest that the impedance readout is highly sensitive and provides more information than some of the conventional endpoint cytotoxicity assays for β-cell injury such as the Cell Counting Kit-8 (CCK-8) and morphology measurements. Furthermore, this system was used to evaluate the anti-injury effects of glucagon-like peptide-1 (GLP-1) and its nonpeptidic mimetic Boc5 by monitoring responses to four toxicants in two β-cell lines. This study confirms that the protective property of Boc5 on β-cells is similar to that of GLP-1.

Glucagon-like peptide-1 (GLP-1)-based therapy presents a promising option for treating type 2 diabetes. However, there are several limitations relative to the peptidic GLP-1 mimetics currently on the market or under development. This concern has led to a continued interest in the search for non-peptidic agonists for GLP-1 receptor (GLP-1R). Here, we briefly review the discovery, characterization and current status of a novel class of cyclobutane-derivative-based non-peptidic agonists for GLP-1R, including Boc5 and its newly discovered analogue WB4–24. Although the oral bioavailability of such compounds still poses great challenges, the progress made so far encourages us to identify a truly 'druggable' small molecule agonist for GLP-1R.

Obesity, the primary health threat in the 21st century, affects the quality of life physiologically, economically and psychologically, irrespective of cultural, financial or ethnic background. Prevalence of obesity has been increasing steadily during the past 30 years worldwide, especially in developed countries. In America, almost one-third of adult population are obese (BMI ≥30 kg/m2)1 and healthcare expenditure for obesity had reached nearly 75 billion USD in 20032. A similar picture has been seen in developing countries as well where incidence of obesity is rising at an alarming speed. In China, according to one report, 12.1% and 2.6% of the urban population are either overweight (25 kg/m2≤ BMI ≤30 kg/m2) or clinically obese (BMI ≥30 kg/m2)3. The situation in children is more disturbing: a 2005 study conducted in northern coastal large cities of China shows that the combined prevalence of obesity had reached 32.5% in boys and 17.6% in girls, respectively4. Possible contributing factors may include steady economic growth, lifestyle changes and significantly reduced family size since the late 1970's.From a medical stand point, obesity contributes to a broad range of health issues, involving type 2 diabetes mellitus, cardiovascular and kidney diseases (see review by Barton), as well as certain cancers, etc5. It significantly increases mortality, causes physical impairment and psychological stigma, and results in economic burden that is largely unmanageable even in many affluent societies. Therefore, prevention and treatment of obesity are a common challenge with extraordinary urgency to both developed and developing nations, and all-out efforts are required to exploit efficient strategies, from policy to education, from research to industry, and from physicians to patients.Obesity is generally recognized as disturbances in energy homeostasis between nutrient intake and expenditure. The balance is controlled by the central nervous system (CNS), mainly the neurons located in hypothalamus. They sense nutrient molecules in circulation and peripheral signaling proteins released by organs in order to regulate energy homeostasis6. However, the exact molecular mechanisms relative to pathogenesis of obesity remain elusive (see review by Herbst), and may include interaction of different genes (see article by Ke et al), environmental factors, life style, social status and even intrauterine or neonatal nutritional states7. It is believed that a chronic, low grade inflammation, in response to excess nutrients or energy, in the metabolic tissues is involved in the development of obesity (see review by Gao and Ye). A cascade may exist starting from release of inflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin-1(IL-1)β, CCL2, etc] and activation of inflammatory kinases (JNK, IKK, PKR etc) by metabolic cells, progressing towards tissue malfunction (eg insulin resistance), and eventually linking inflammation to obesity-related diseases, such as type 2 diabetes8.While prevention is largely dependent upon change of life style, therapeutic approaches are dominated by medications that result in weight loss, covering both small molecules and peptides aiming at a variety of drug targets (Tables 1 and 2)9, 10, 11. Of which, sibutramine, phentermine, rimonabant, lorcaserin, contrave, qnexa, liraglutide, tesofensine and velneperit, etc, target the CNS and decrease energy intake via reducing appetite or increasing satiety, whereas orlistat and cetilistat interfere with nutrient absorption in the digestive system. Although the pipeline looks prosperous, only one drug (orlistat) is available at present for long-term weight control because sibutramine was withdrawn last year due to an increased cardiovascular risk12. Others that were approved for short-term treatment (eg phentermine, diethylpropion, benzphetamine and phendimetrazine) all have the limitation of controlled use because of potential drug abuse13.With worldwide demands for a “magic bullet” to loose body weight, major pharmaceutical companies are chasing after the multibillion-dollar obesity market even under extremely high risks. In 2010, Sanofi-Avantis decided to discontinue all ongoing clinical trials and to suspend sales of its cannabinoid 1 receptor (CB1R) blocker, rimonabant, following the recommendation from the European Medicines Agency in response to serious psychiatric side-effects14. Merck and Pfizer wasted no time to cease the development of their versions of CB1R antagonists, taranabant and CP-945598, respectively, making CB1R as a drug target dubious. Thus, a new strategy to discover selective CB1R blockers that predominantly interact with the receptor in the periphery has been debated14.Haunted by the withdrawal of sibutramine and the end of CB1R blockers, the developers of anti-obesity drugs experienced further setbacks. Apart from rejecting regulatory approval of Vivus's combination product qnexa and Arena's locaserin15, the Food and Drug Administration requested a cardiovascular outcome study for another combination therapy, Orexigen's contrave10. Obviously, the paramount concern on therapeutics against obesity is safety because it is not a fatal disease and requires long-term management. In comparison with physical exercise and diet control that demand for active participation, the advantage of a safe and efficacious pill is unquestionable albeit it is passive in terms of patient efforts.The multi-facet actions of the gut hormone, glucagon-like peptide-1 (GLP-1), render it ideal as a target for drug intervention16. Encouraged by early success with a GLP-1 mimetic, exenatide, in diabetic weight loss17, liraglutide, a long-acting GLP-1 analog, was shown to reduce body weight in both animal models of obesity (see article by Hansen et al) and human clinical studies18. Similar effects in animal models were also seen with a non-peptidic GLP-1 receptor agonist Boc519 and one of its analogs (see review by He et al).As demonstrated in the treatment of many other diseases, combination therapy is more effective than a single agent. Of the four such products (qnexa, contrave, empatic and pramlintide), qnexa and contrave were previously approved for other indications. Clinical trials revealed that qnexa (phentermine plus topiramate) and contrave (bupropion plus naltrexone) administration induced a net weight loss of 12.2 kg and 6.2 kg, respectively, compared with a reduction of 4.0 kg or 3.2 kg when phentermine or bupropion was administered alone10.Facing such an unprecedented challenge on a global scale, it is far from adequate in terms of novel approaches to obesity management. Clearly, the most important task lies in education that alters social behavior capable of preventing the prevalence of obesity from rising. In this special issue, several topics that relate to obesity etiology, animal models (see review by Nilsson et al), therapeutics and clinical implications are covered in order to provide a glance of the latest developments in this important field.

A novel class of non-steroidal progesterone receptor antagonists with aromatic β-amino-ketone scaffold have been synthesized and characterized with high binding affinity and great selectivity for the cognate receptors. Among them, compound 22 was shown to be the most potent progesterone receptor antagonist in cotransfection assay and a murine model of ligand-induced decidualization.A series of aromatic β-amino-ketone derivatives was identified as a novel class of non-steroidal progesterone receptor antagonists.

Glucagon-like peptide-1 (GLP-1) receptor is an ideal target in the development of incretin-based therapies for diabetes and obesity. Two approaches have been adopted: GLP-1 receptor agonists that mimic the effects of native GLP-1 and dipeptidyl peptidase-4 inhibitors that increase endogenous GLP-1 levels. During the past two decades, search for orally active, non-peptidic GLP-1 receptor agonists has been the focal point of research and development activities in many multinational pharmaceutical companies. Such efforts have not resulted in any success thus far. Serendipitous discovery of substituted cyclobutanes represented by Boc5 as a new class of GLP-1 receptor agonists led us to believe that a small molecule approach to class B G-protein coupled receptor agonism is no longer a fantasy but a reality. However, major obstacles still pose great challenges, and the reasons of which are discussed in this perspectives.

The pharmaceutical industry is presently suffering difficult times due to low productivity of new molecular entities. As a major source of drug leads, high-throughput screening (HTS) has been often criticized for its ‘dead end’ lead compounds. However, the fruitful achievements resulting from HTS technology indicate that it remains a feasible way for drug innovation. Because of increasing considerations of earlier stage ADMET (absorption, distribution, metabolism, excretion and toxicity) in drug development, cell-based HTS is highly recommended in modern drug discovery for its ability to detect more biologically relevant characteristics of compounds in living systems. This review provides a systematic and practical description of vital points for conducting high quality cell-based HTS, from assay development to optimization, compound management, data analyses, hit validation as well as lead identification. Potential problems and solutions are also covered.