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The treatment and prevention of atrial fibrillation (AF) remains a significant unmet medical need. Existing therapies that maintain or restore sinus rhythm (rhythm control) have deleterious effects on the ventricle. A major goal for finding new AF therapies is the identification of repolarization mechanisms that are present in the atrium and not in the ventricle. The potassium current I(Kur) has been shown to be selectively involved in atrial repolarization in human tissue. Hence this current and specifically Kv1.5, the protein that underlies it, have become prime targets for the invention of new AF agents. This article reviews the development of Kv1.5 blockers. The discovery and clinical progress of the non-selective Kv1.5 blockers vernakalant and AVE-0118 are highlighted. More selective Kv1.5 blockers in pre-clinical stages of discovery are then reviewed, with a focus on compounds that have been investigated for their in vivo effects on atrial repolarization or on efficacy in pre-clinical models of atrial fibrillation.

This article describes recent advances in the development and biological evaluation of allosteric and ATP-competitive small molecule inhibitors for the serine/threonine kinase Akt (protein kinase B, PKB). Unregulated activation of the PI3K/Akt/PTEN pathway is a prominent feature of many human cancers and Akt is over-expressed or activated in all major cancers making Akt an exciting new target for cancer therapy. The development of Akt inhibitors has been complicated and hampered by the presence of three Akt isozymes, (Akt1, Akt2 and Akt3) which differ in function and tissue distribution, as well as a lack of Akt specific inhibitors. In the past 18 months, a large number of reports have appeared describing the discovery and development of allosteric Akt kinase inhibitors and classical ATP-competitive Akt kinase inhibitors. This review will discuss the PI3K/Akt/PTEN pathway, allosteric and ATP-competitive Akt kinase inhibitors, their biological evaluation and progress towards target validation.

Inhibition of the cardiac I(Kr) current leads to prolongation of the QT interval and to a risk of ventricular arrhythmia. This activity has been observed for a wide range of small molecules and results from their binding to the hERG ion channel. The off-target inhibition of I(Kr) presents a daunting challenge for many medicinal chemistry programs. This review article presents case studies that describe a rang of findings across several projects at Merck. The article begins with a review of findings from the original efforts to identify I(Kr) blockers as antiarrhythmic therapeutics. A discussion follows of in vitro and in vivo assays that have been utilized for the assessment of I(Kr) inhibition. General SAR rules that have been found to be useful guides for diminishing hERG activity in lead compounds are discussed and case studies are presented that illustrate specific observations. The case studies highlight how the issue of hERG antagonism was navigated on four distinct medicinal chemistry programs.

This article describes recent advances in the development and biological evaluation of small molecule inhibitors for the serine/threonine kinase Akt (PKB). Akt plays a pivotal role in cell survival and proliferation through a number of downstream effectors. Recent studies indicate that unregulated activation of the PI3K/Akt pathway is a prominent feature of many human cancers and Akt is over-expressed or activated in all major cancers. Akt is considered an attractive target for cancer therapy and inhibition of Akt alone or in combination with standard cancer chemotherapeutics has been postulated to reduce the apoptotic threshold and preferentially kill cancer cells. The development of specific and potent inhibitors will allow this hypothesis to be tested in animals. Recently, several series of small molecule, ATP-competitive inhibitors have been reported with a range of Akt potencies and selectivities. Phosphatidylinositol (PI) analogs have been reported to inhibit Akt, but these inhibitors may also have specificity problems with respect to other pleckstrin homology (PH) domain containing proteins and may have poor bioavailability. In addition, novel allosteric inhibitors have been reported which are PH domain dependent, exhibit selectivity for the individual Akt isozymes and inhibit the activity and the activation of Akt. Compounds within these classes Akt inhibitors have sufficient potency and specificity to test for tumor efficacy in animal models and recently reported preliminary experiments are reviewed.

This article describes recent advances in the development and biological evaluation of small molecule inhibitors for the serine/threonine kinase Akt (PKB). Akt plays a pivotal role in cell survival and proliferation through a number of downstream effectors. Recent studies indicate that unregulated activation of the PI3K/Akt pathway is a prominent feature of many human cancers and Akt is over-expressed or activated in all major cancers. Akt is considered an attractive target for chemotherapy and it has been postulated that inhibition of Akt alone or in combination with standard cancer chemotherapeutics will reduce the apoptotic threshold and preferentially kill cancer cells. The development of specific and potent inhibitors will allow this hypothesis to be tested in animals. The majority of small molecule inhibitors in this nascent field are classic ATP-competitive inhibitors which provide little specificity. Phosphatidylinositol (PI) analogs have been reported to inhibit Akt, but these inhibitors may also have specificity problems with respect to other PH domain containing proteins and may have poor bioavailability. None of the inhibitors in these classes have been reported to have Akt isozyme specificity. Recently, novel allosteric inhibitors have been reported which are pleckstrin homology domain dependent and exhibit Akt isozyme selectivity. Inhibitors in this class may have sufficient potency and specificity to test for tumor efficacy in animal models and recently reported preliminary experiments are reviewed.