Progress in the design and development of phosphoinositide 3-kinase (PI3K) inhibitors for the treatment of chronic diseases

Discovery and synthesis of a novel series of potent, selective inhibitors of the PI3Kα: 2-alkyl-chromeno[4,3-c]pyrazol-4(2H)-one derivatives

A series of novel 2-alkyl-chromeno[4,3-c]pyrazol-4(2H)-one derivatives were synthesized and evaluated for their biological activities as PI3K inhibitors. In vitro biological evaluation against four human tumor cell lines revealed that most target compounds showed impressively better antiproliferative activities than that of LY294002. Among these compounds, compound 4l exhibited the most potent and selective activity for PI3Kα, with the value of 0.014 μM, an approximately 30-fold increase in comparison with LY294002. Docking simulation was performed to position compound 4l into the PI3Kα active site and the result showed that compound 4l could bind well at the PI3Kα active site and it indicated that compound 4l could be a potential inhibitor of PI3Kα.

Synthesis and cancer stem cell-based activity of substituted 5-morpholino-7H-thieno[3,2-b]pyran-7-ones designed as next generation PI3K inhibitors

Dysregulation of the phosphatidylinositol-3-kinase (PI3K) pathway in a wide range of tumors has made PI3K a consensus target to inhibit as illustrated by more than 15 inhibitors now in clinical trials. Our previous work, built on the early pioneering multikinase inhibitor LY294002, resulted in the only PI3K vascular-targeted PI3K inhibitor prodrug, SF1126, which has now completed Phase I clinical trials. This inhibitor has properties that impart more in vivo activity than should be warranted by its enzymatic potency, which in general is much lower than other clinical stage PI3K inhibitors. We embarked on the exploration of scaffolds that retained such properties while simultaneously exhibiting an increased potency toward PI3K. This work resulted in the discovery of the 5-morpholino-7H-thieno[3,2-b]pyran-7-one system as the foundation of a new compound class of potential PI3K inhibitors having improved potency toward PI3K. The synthesis and cancer stem cell-based activity of these compounds are reported herein.

Novel pyrazolo[1,5-a]pyridines as p110α-selective PI3 kinase inhibitors: Exploring the benzenesulfonohydrazide SAR

Structure-activity relationship studies of the pyrazolo[1,5-a]pyridine class of PI3 kinase inhibitors show that substitution off the hydrazone nitrogen and replacement of the sulfonyl both gave a loss of p110α selectivity, with the exception of an N-hydroxyethyl analogue. Limited substitutions were tolerated around the phenyl ring; in particular the 2,5-substitution pattern was important for PI3 kinase activity. The N-hydroxyethyl compound also showed good inhibition of cell proliferation and inhibition of phosphorylation of Akt/PKB, a downstream marker of PI3 kinase activity. It had suitable pharmacokinetics for evaluation in vivo, and showed tumour growth inhibition in two human tumour cell lines in xenograft studies. This work has provided suggestions for the design of more soluble analogues.

Synthesis and biological evaluation of novel analogues of the pan class I phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(difluoromethyl)-1-[4,6-di(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole (ZSTK474)

A structure-activity relationship (SAR) study of the pan class I PI 3-kinase inhibitor 2-(difluoromethyl)-1-[4,6-di(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole (ZSTK474) identified substitution at the 4 and 6 positions of the benzimidazole ring as having significant effects on the potency of substituted derivatives. The 6-amino-4-methoxy analogue displayed a greater than 1000-fold potency enhancement over the corresponding 6-aza-4-methoxy analogue against all three class Ia PI 3-kinase enzymes (p110α, p110β, and p110δ) and also displayed significant potency against two mutant forms of the p110α isoform (H1047R and E545K). This compound was also evaluated in vivo against a U87MG human glioblastoma tumor xenograft model in Rag1(-/-) mice, and at a dose of 50 mg/kg given by ip injection at a qd × 10 dosing schedule it dramatically reduced cancer growth by 81% compared to untreated controls.

Progress in the preclinical discovery and clinical development of class I and dual class I/IV phosphoinositide 3-kinase (PI3K) inhibitors

The phosphoinositide 3-kinases (PI3Ks) constitute an important family of lipid kinase enzymes that control a range of cellular processes through their regulation of a network of signal transduction pathways, and have emerged as important therapeutic targets in the context of cancer, inflammation and cardiovascular diseases. Since the mid-late 1990s, considerable progress has been made in the discovery and development of small molecule ATP-competitive PI3K inhibitors, a number of which have entered early phase human trials over recent years from which key clinical results are now being disclosed. This review summarizes progress made to date, primarily on the discovery and characterization of class I and dual class I/IV subtype inhibitors, together with advances that have been made in translational and clinical research, notably in cancer.

PI3K: from the bench to the clinic and back

From humble beginnings over 25 years ago as a lipid kinase activity associated with certain oncoproteins, PI3K (phosphoinositide 3-kinase) has been catapulted to the forefront of drug development in cancer, immunity and thrombosis, with the first clinical trials of PI3K pathway inhibitors now in progress. Here, we give a brief overview of some key discoveries in the PI3K area and their impact, and include thoughts on the current state of the field, and where it could go from here.PI3K has become a very intense area of research, with over 2,000 publications on PI3K in PubMed for 2009 alone. The expectations for a therapeutic impact of intervention with PI3K activity are high, and progress in the clinical arena is being monitored by many. However, targeted therapies almost invariably encounter roadblocks, often exposing unresolved questions in the basic understanding of the target. PI3K will most likely be no exception. Below, we describe some of these early "surprises" and how these inform and shape basic science investigations.