The Discovery of PLK4 Inhibitors: (E)-3-((1H-Indazol-6-yl)methylene)indolin-2-ones as Novel Antiproliferative Agents
ABSTRACT The family of Polo-like Kinases is important in the regulation of mitotic progression; this work keys on one member, namely Polo-like Kinase 4 (PLK4). PLK4 has been identified as a candidate anti-cancer target which prompted a search for potent and selective inhibitors of PLK4. The body of the paper describes lead generation and optimization work which yielded nanomolar PLK4 inhibitors. Lead generation began with directed virtual screening, using a ligand based focused library and a PLK4 homology model. Validated hits were used as starting points for the design and discovery of PLK4 inhibitors of novel structure, namely (E)-3-((1H-indazol-6-yl)methylene)indolin-2-ones. Computational models, based on a published X-ray structure (PLK4 kinase domain), were used to understand and optimize the in vitro activity of the series; potent anti-proliferative activity was obtained. The kinase selectivity profile and cell cycle analysis of selected inhibitors are described. The results of a xenograft study with an optimized compound 50 (designated CFI-400437) support the potential of these novel PLK4 inhibitors for cancer therapy.
SourceAvailable from: Ayman Altoukhy[Show abstract] [Hide abstract]
ABSTRACT: A hybrid pharmacophore approach was adopted to design and synthesize new series of isatin-pyridine hybrids. All the newly prepared hybrids (5a-o, 8 and 11a-d) were in vitro evaluated for their anti-proliferative activity against three human cancer cell lines, namely HepG2 hepatocellular carcinoma, A549 lung cancer and MCF-7 breast cancer. Compound 8 emerged as the most active member against HepG2 cell line (IC50 = 2.5 ± 0.39 μM), with 2.7-fold increased activity than the reference drug, doxorubicin (IC50 = 6.9 ± 2.05 μM). Whilst, compound 11c was found to be the most potent counterpart against A549 and MCF-7 cell lines with IC50 values of 10.8 ± 1.15 and 6.3 ± 0.79, respectively. The weightiness of the utilization of non-cleavable linker, as the chalcone linker, and simplification of the first group, was explored via the SAR study. Furthermore, a QSAR model was built to explore the structural requirements controlling the cytotoxic activities. Notably, the predicted activities by the QSAR model were very close to those experimentally observed, hinting that this model could be safely applied for prediction of more efficacious hits comprising the same skeletal framework. Finally, a theoretical kinetic study was established to predict the ADME of the active hybrids. Copyright © 2014 Elsevier Masson SAS. All rights reserved.European Journal of Medicinal Chemistry 12/2014; 90C:684-694. DOI:10.1016/j.ejmech.2014.12.010 · 3.43 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The identification of novel anticancer agents with high efficacy and low toxicity has always been an intriguing topic in medicinal chemistry. The unique structural features of spirooxindoles together with diverse biological activities have made them promising structures in new drug discovery. Among spirooxindoles, CFI-400945 holds its promise as the first potent PLK4 inhibitor, the fumarate of CFI-400945 has entered phase I clinical trials for the treatment of solid tumors. However, questions remain as to whether PLK4 is the only relevant therapeutic target for CFI-400945. To highlight this significant progress of CFI-400945 in last two years, this review centers on the identification from a focused kinase library, structural optimizations and strategies involved, structure-activity relationships, modes of action, target validation, chemical synthesis and, more importantly, the kinase selectivity between PLK4 and other targets. Copyright © 2015 Elsevier Masson SAS. All rights reserved.European Journal of Medicinal Chemistry 03/2015; 95. DOI:10.1016/j.ejmech.2015.03.020 · 3.43 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Tropomyosin receptor kinases (TrkA/B/C) are critically involved in the development of the nervous system, in neurological disorders as well as in multiple neoplasms of both neural and non-neural origins. The development of Trk radiopharmaceuticals would offer unique opportunities towards a more complete understanding of this emerging therapeutic target. To that end, we first developed [11C]GW441756 ([11C]9), a high affinity photoisomerizable pan-Trk inhibitor as a lead radiotracer for our PET program. Efficient carbon-11 radiolabeling afforded [11C]9 in equimolar E:Z isomeric composition in high radiochemical yields (isolated RCY, 25.9 ± 5.7 %). In vitro autoradiographic studies in rat brain and TrkB-expressing human neuroblastoma cryosections confirmed that [11C]9 specifically binds to Trk receptors in vitro. MicroPET studies revealed that binding of [11C]9 in the rodent brain is mostly nonspecific despite initial high brain uptake (SUVmax = 2.0). Modeling studies of the 4-aza-2-oxindole scaffold led to the successful identification of a small series of high affinity fluorinated and methoxy derivatized pan-Trk inhibitors based on our lead compound 9. Out of this series, the fluorinated compound 10 was selected for initial evaluation and radiolabeled with fluorine-18 (isolated RCY, 2.5 ± 0.6 %). Compound [18F]10 demonstrated excellent Trk selectivity in a panel of cancer relevant kinase targets and a promising in vitro profile. Preliminary microPET evaluation in rat revealed a moderate initial brain uptake (SUVmax = 0.8) but superior SUVs after 20 min and up to >220% at 60 min compared to the lead [11C]9. The results presented herein constitute the first report of radiolabeled Trk-targeted probes which permeate the BBB and display favourable physico-chemical properties as potential PET tracers.ACS Chemical Neuroscience 10/2014; 6(2). DOI:10.1021/cn500193f · 4.21 Impact Factor