Daniele Fancelli

PHA-739358, a potent inhibitor of Aurora kinases with a selective target inhibition profile relevant to cancer

PHA-739358 is a small-molecule 3-aminopyrazole derivative with strong activity against Aurora kinases and cross-reactivities with some receptor tyrosine kinases relevant for cancer. PHA-739358 inhibits all Aurora kinase family members and shows a dominant Aurora B kinase inhibition–related cellular phenotype and mechanism of action in cells in vitro and in vivo. p53 status–dependent endoreduplication is observed upon treatment of cells with PHA-739358, and phosphorylation of histone H3 in Ser10 is inhibited. The compound has significant antitumor activity in different xenografts and spontaneous and transgenic animal tumor models and shows a favorable pharmacokinetic and safety profile. In vivo target modulation is observed as assessed by the inhibition of the phosphorylation of histone H3, which has been validated preclinically as a candidate biomarker for the clinical phase. Pharmacokinetics/pharmacodynamics modeling was used to define drug potency and to support the prediction of active clinical doses and schedules. We conclude that PHA-739358, which is currently tested in clinical trials, has great therapeutic potential in anticancer therapy in a wide range of cancers. [Mol Cancer Ther 2007;6(12):3158–68]

PHA-680632, a novel Aurora kinase inhibitor with potent antitumoral activity.

Purpose: Aurora kinases play critical roles during mitosis in chromosome segregation and cell division. The aim of this study was to determine the preclinical profile of a novel, highly selective Aurora kinase inhibitor, PHA-680632, as a candidate for anticancer therapy. Experimental Design: The activity of PHA-680632 was assayed in a biochemical ATP competitive kinase assay. A wide panel of cell lines was evaluated for antiproliferative activity. Cell cycle analysis. Immunohistochemistry, Western blotting, and Array Scan were used to follow mechanism of action and biomarker modulation. Specific knockdown of the targets by small interfering RNA was followed to validate the observed phenotypes. Efficacy was determined in different xenograft models and in a transgenic animal model of breast cancer. Results: PHA-680632 is active on a wide range of cancer cell lines and shows significant tumor growth inhibition in different animal tumor models at well-tolerated doses. The mechanism of action of PHA-680632 is in agreement with inhibition of Aurora kinases. Histone H3 phosphorylation in Ser10 is mediated by Aurora B kinase, and our kinetic studies on its inhibition by PHA-680632 in vitro and in vivo show that phosphorylation of histone H3 is a good biomarker to follow activity of PHA-680632. Conclusions: PHA-680632 is the first representative of a new class of Aurora inhibitors with a high potential for further development as an anticancer therapeutic. On treatment, different cell lines respond differentially, suggesting the absence of critical cell cycle checkpoints that could be the basis for a favorable therapeutic window.

Crystal Structure of the T315I Abl Mutant in Complex with the Aurora Kinases Inhibitor PHA-739358

Mutations in the kinase domain of Bcr-Abl are the most common cause of resistance to therapy with imatinib in patients with chronic myelogenous leukemia (CML). Second-generation Bcr-Abl inhibitors are able to overcome most imatinib-resistant mutants, with the exception of the frequent T315I substitution, which is emerging as a major cause of resistance to these drugs in CML patients. Structural studies could be used to support the drug design process for the development of inhibitors able to target the T315I substitution, but until now no crystal structure of the T315I Abl mutant has been solved. We show here the first crystal structure of the kinase domain of Abl T315I in complex with PHA-739358, an Aurora kinase inhibitor currently in clinical development for solid and hematologic malignancies. This compound inhibits in vitro the kinase activity of wild-type Abl and of several mutants, including T315I. The cocrystal structure of T315I Abl kinase domain provides the structural basis for this activity: the inhibitor associates with an active conformation of the kinase domain in the ATP-binding pocket and lacks the steric hindrance imposed by the substitution of threonine by isoleucine.

SOLID PHASE SYNTHESIS OF 2-SUBSTITUTED BENZOFURANS VIA THE PALLADIUM-CATALYSED HETEROANNULATION OF ACETYLENES

Abstract The copper/palladium-promoted heteroannulation of terminal acetylenic compounds in the presence of resin bound ortho-hydroxy aryl iodides is described. The process produces 2-substituted benzofuran derivatives in good yield and high purity.

An update on therapeutic opportunities offered by cancer glycolytic metabolism

Almost all invasive cancers, regardless of tissue origin, are characterized by specific modifications of their cellular energy metabolism. In fact, a strong predominance of aerobic glycolysis over oxidative phosphorylation (Warburg effect) is usually associated with aggressive tumour phenotypes. This metabolic shift offers a survival advantage to cancer cells, since they may continue to produce energy and anabolites even when they are exposed to either transient or permanent hypoxic conditions. Moreover, it ensures a high production rate of glycolysis intermediates, useful as building blocks for fast cell proliferation of cancer cells. This peculiar metabolic profile may constitute an ideal target for therapeutic interventions that selectively hit cancer cells with minimal residual systemic toxicity. In this review we provide an update about some of the most recent advances in the discovery of new bioactive molecules that are able to interfere with cancer glycolysis.

Cinnamic anilides as new mitochondrial permeability transition pore inhibitors endowed with ischemia-reperfusion injury protective effect in vivo.

In this account, we report the development of a series of substituted cinnamic anilides that represents a novel class of mitochondrial permeability transition pore (mPTP) inhibitors. Initial class expansion led to the establishment of the basic structural requirements for activity and to the identification of derivatives with inhibitory potency higher than that of the standard inhibitor cyclosporine-A (CsA). These compounds can inhibit mPTP opening in response to several stimuli including calcium overload, oxidative stress, and thiol cross-linkers. The activity of the cinnamic anilide mPTP inhibitors turned out to be additive with that of CsA, suggesting for these inhibitors a molecular target different from cyclophylin-D. In vitro and in vivo data are presented for (E)-3-(4-fluoro-3-hydroxy-phenyl)-N-naphthalen-1-yl-acrylamide 22, one of the most interesting compounds in this series, able to attenuate opening of the mPTP and limit reperfusion injury in a rabbit model of acute myocardial infarction.

Thieno[3,2-C]Pyrazoles: A Novel Class of Aurora Inhibitors with Favorable Antitumor Activity.

A novel series of 3-amino-1H-thieno[3,2-c]pyrazole derivatives demonstrating high potency in inhibiting Aurora kinases was developed. Here we describe the synthesis and a preliminary structure-activity relationship, which led to the discovery of a representative compound (38), which showed low nanomolar inhibitory activity in the anti-proliferation assay and was able to block the cell cycle in HCT-116 cell line. This compound demonstrated favorable pharmacokinetic properties and good efficacy in the HL-60 xenograft tumor model.

GNX-4728, a novel small molecule drug inhibitor of mitochondrial permeability transition, is therapeutic in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder in humans characterized by progressive degeneration of skeletal muscle and motor neurons in spinal cord, brainstem, and cerebral cortex causing skeletal muscle paralysis, respiratory insufficiency, and death. There are no cures or effective treatments for ALS. ALS can be inherited, but most cases are not associated with a family history of the disease. Mitochondria have been implicated in the pathogenesis but definitive proof of causal mechanisms is lacking. Identification of new clinically translatable disease mechanism-based molecular targets and small molecule drug candidates are needed for ALS patients. We tested the hypothesis in an animal model that drug modulation of the mitochondrial permeability transition pore (mPTP) is therapeutic in ALS. A prospective randomized placebo-controlled drug trial was done in a transgenic (tg) mouse model of ALS. We explored GNX-4728 as a therapeutic drug. GNX-4728 inhibits mPTP opening as evidenced by increased mitochondrial calcium retention capacity (CRC) both in vitro and in vivo. Chronic systemic treatment of G37R-human mutant superoxide dismutase-1 (hSOD1) tg mice with GNX-4728 resulted in major therapeutic benefits. GNX-4728 slowed disease progression and significantly improved motor function. The survival of ALS mice was increased significantly by GNX-4728 treatment as evidence by a nearly 2-fold extension of lifespan (360 days–750 days). GNX-4728 protected against motor neuron degeneration and mitochondrial degeneration, attenuated spinal cord inflammation, and preserved neuromuscular junction (NMJ) innervation in the diaphragm in ALS mice. This work demonstrates that a mPTP-acting drug has major disease-modifying efficacy in a preclinical mouse model of ALS and establishes mitochondrial calcium retention, and indirectly the mPTP, as targets for ALS drug development.

6-Substituted Pyrrolo[3,4-c]pyrazoles: An Improved Class of CDK2 Inhibitors

We have recently reported a new class of CDK2/cyclin A inhibitors based on a bicyclic tetrahydropyrrolo[3,4‐c]pyrazole scaffold. The introduction of small alkyl or cycloalkyl groups in position 6 of this scaffold allowed variation at the other two diversity points. Conventional and polymer‐assisted solution phase chemistry provided a way of generating compounds with improved biochemical and cellular activity. Optimization of the physical properties and pharmacokinetic profile led to a compound which exhibited good efficacy in vivo on A2780 human ovarian carcinoma.

Inhibitors of Aurora kinases for the treatment of cancer

Aurora protein kinases are key players in different steps during mitosis and their activity is required for correct cell division. The inhibition of Aurora kinases is regarded as a promising approach for the development of novel anticancer agents. In the last few years several templates for ATP-competitive kinase inhibition have been successfully developed towards the inhibition of Aurora kinases, and the first compounds have recently entered clinical studies. This review summarises the patent literature up until March 2005 and the characteristics of the low molecular weight Aurora inhibitors described so far.