RESUMO
IRAK4 is responsible for initiating signaling from Toll-like receptors (TLRs) and members of the IL-1/18 receptor family. Kinase-inactive knock-ins and targeted deletions of IRAK4 in mice cause reductions in TLR induced pro-inflammatory cytokines and these mice are resistant to various models of arthritis. Herein we report the identification and optimization of a series of potent IRAK4 inhibitors. Representative examples from this series showed excellent selectivity over a panel of kinases, including the kinases known to play a role in TLR-mediated signaling. The compounds exhibited low nM potency in LPS- and R848-induced cytokine assays indicating that they are blocking the TLR signaling pathway. A key compound (26) from this series was profiled in more detail and found to have an excellent pharmaceutical profile as measured by predictive assays such as microsomal stability, TPSA, solubility, and clogP. However, this compound was found to afford poor exposure in mouse upon IP or IV administration. We found that removal of the ionizable solubilizing group (32) led to increased exposure, presumably due to increased permeability. Compounds 26 and 32, when dosed to plasma levels corresponding to ex vivo whole blood potency, were shown to inhibit LPS-induced TNFα in an in vivo murine model. To our knowledge, this is the first published in vivo demonstration that inhibition of the IRAK4 pathway by a small molecule can recapitulate the phenotype of IRAK4 knockout mice.
Assuntos
Indóis/química , Indóis/farmacologia , Quinases Associadas a Receptores de Interleucina-1/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/química , Quinolinas/farmacologia , Animais , Feminino , Humanos , Indóis/farmacocinética , Quinases Associadas a Receptores de Interleucina-1/imunologia , Lipopolissacarídeos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Modelos Moleculares , Inibidores de Proteínas Quinases/farmacocinética , Quinolinas/farmacocinética , Transdução de Sinais/efeitos dos fármacosRESUMO
Src-null mice have higher bone mass because of decreased bone resorption and increased bone formation, whereas Abl-null mice are osteopenic, because of decreased bone formation. Compound I, a potent inhibitor of Src in an isolated enzyme assay (IC(50) 0.55 nM) and a Src-dependent cell growth assay, with lower activity on equivalent Abl-based assays, potently, but biphasically, accelerated differentiation of human mesenchymal stem cells to an osteoblast phenotype (1-10 nM). Compound I (≥0.1 nM) also activated osteoblasts and induced bone formation in isolated neonatal mouse calvariae. Compound I required higher concentrations (100 nM) to inhibit differentiation and activity of osteoclasts. Transcriptional profiling (TxP) of calvaria treated with 1 µM compound I revealed down-regulation of osteoclastic genes and up-regulation of matrix genes and genes associated with the osteoblast phenotype, confirming compound I's dual effects on bone resorption and formation. In addition, calvarial TxP implicated calcitonin-related polypeptide, ß (ß-CGRP) as a potential mediator of compound I's osteogenic effect. In vivo, compound I (1 mg/kg s.c.) increased vertebral trabecular bone volume 21% (microcomputed tomography) in intact female mice. Increased trabecular volume was also detected histologically in a separate bone, the femur, particularly in the secondary spongiosa (100% increase), which underwent a 171% increase in bone formation rate, a 73% increase in mineralizing surface, and a 59% increase in mineral apposition rate. Similar effects were observed in ovariectomized mice with established osteopenia. We conclude that the Src inhibitor compound I is osteogenic, presumably because of its potent stimulation of osteoblast differentiation and activation, possibly mediated by ß-CGRP.
Assuntos
Osteogênese/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-abl/antagonistas & inibidores , Quinases da Família src/antagonistas & inibidores , Sequência de Aminoácidos , Animais , Diferenciação Celular , Perfilação da Expressão Gênica , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacosRESUMO
Analog 8, a 3-pyridinecarbonitrile with an (E)-2-[6-[(4-methylpiperazin-1-yl)methyl]pyridin-2-yl]vinyl group at C-5, had an IC(50) value of 1.1 nM for the inhibition of PKCtheta and potently blocked the production of IL-2 in both stimulated murine T cells (IC(50)=34 nM) and human whole blood (IC(50)=500 nM).
Assuntos
Isoenzimas/antagonistas & inibidores , Nitrilas/farmacologia , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Animais , Humanos , Interleucina-2/biossíntese , Camundongos , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/enzimologia , Nitrilas/química , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/química , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismoRESUMO
The 7-alkene-3-quinolinecarbonitrile 20, a potent inhibitor of Src enzymatic and cellular activity with IC(50) values of 2.1 and 58 nM, respectively, had comparable efficacy to bosutinib in a colon tumor xenograft study.
Assuntos
Antineoplásicos/química , Inibidores de Proteínas Quinases/química , Quinolinas/química , Quinases da Família src/antagonistas & inibidores , Animais , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Humanos , Camundongos , Camundongos Nus , Microssomos/metabolismo , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/síntese química , Quinolinas/farmacologia , Ensaios Antitumorais Modelo de Xenoenxerto , Quinases da Família src/metabolismoRESUMO
Src kinase signaling has been implicated in multiple mechanisms of ischemic injury, including vascular endothelial growth factor (VEGF)-mediated vascular permeability that leads to vasogenic edema, a major clinical complication in stroke and brain trauma. Here we report the effects of two novel Src kinase inhibitors, 4-[(2,4-dichloro-5-methoxyphenyl)amino]-6-methoxy-7-[3-(4-methyl-1-piperazinyl)propoxy]-3-quinolinecarbonitrile (SKI-606) and 4-[(2,4-dichloro-5-methoxyphenyl)amino]-6-methoxy-7-[4-(4-methypiperazin-1-yl)but-1-ynyl]-3-quinolinecarbonitrile (SKS-927), on ischemia-induced brain infarction and short- and long-term neurological deficits. Two well established transient [transient middle cerebral artery occlusion (tMCAO)] and permanent [permanent middle cerebral artery occlusion (pMCAO)] focal ischemia models in the rat were used with drug treatments initiated up to 6 h after onset of stroke to mimic the clinical scenario. Brain penetration of Src inhibitors, their effect on blood-brain barrier integrity and VEGF signaling in human endothelial cells were also evaluated. Our results demonstrate that both agents potently block VEGF-mediated signaling in human endothelial cells, penetrate rat brain upon systemic administration, and inhibit postischemic Src activation and vascular leakage. Treatment with SKI-606 or SKS-927 (at the doses of 3-30 mg/kg i.v.) resulted in a dose-dependent reduction in infarct volume and robust protection from neurological impairments even when the therapy was initiated up to 4- to 6-h after tMCAO. Src blockade after pMCAO resulted in accelerated improvement in recovery from motor, sensory, and reflex deficits during a long-term (3 weeks) testing period poststroke. These data demonstrate that the novel Src kinase inhibitors provide effective treatment against ischemic conditions within a clinically relevant therapeutic window and may constitute a viable therapy for acute stroke.
Assuntos
Compostos de Anilina/uso terapêutico , Isquemia Encefálica/tratamento farmacológico , Fármacos Neuroprotetores/uso terapêutico , Nitrilas/uso terapêutico , Piperazinas/uso terapêutico , Inibidores de Proteínas Quinases/uso terapêutico , Quinolinas/uso terapêutico , Quinases da Família src/antagonistas & inibidores , Compostos de Anilina/administração & dosagem , Compostos de Anilina/química , Compostos de Anilina/farmacocinética , Animais , Plaquetas/efeitos dos fármacos , Plaquetas/enzimologia , Encéfalo/efeitos dos fármacos , Encéfalo/enzimologia , Encéfalo/metabolismo , Isquemia Encefálica/enzimologia , Permeabilidade Capilar , Células Cultivadas , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/enzimologia , Citometria de Fluxo , Humanos , Injeções Intravenosas , Masculino , Estrutura Molecular , Fármacos Neuroprotetores/administração & dosagem , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/farmacocinética , Testes Neuropsicológicos , Nitrilas/administração & dosagem , Nitrilas/química , Nitrilas/farmacocinética , Piperazinas/administração & dosagem , Piperazinas/química , Piperazinas/farmacocinética , Inibidores de Proteínas Quinases/administração & dosagem , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacocinética , Quinolinas/administração & dosagem , Quinolinas/química , Quinolinas/farmacocinética , Ratos , Ratos Wistar , Fatores de TempoRESUMO
A series of 5-vinyl phenyl sulfonamide-3-pyridinecarbonitriles were prepared and evaluated as PKCtheta inhibitors. Optimization resulted in the identification of compound 15 with an IC(50) value 0.44 nM for the inhibition of PKCtheta with 150-fold selectivity over PKCdelta.
Assuntos
Isoenzimas/antagonistas & inibidores , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Piridinas/síntese química , Piridinas/farmacologia , Sulfonamidas/síntese química , Sulfonamidas/farmacologia , Desenho de Fármacos , Estrutura Molecular , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/química , Estereoisomerismo , Relação Estrutura-Atividade , Sulfonamidas/químicaRESUMO
A series of 4-anilino-7-pyridyl-3-quinolinecarbonitriles was prepared as Src kinase inhibitors. A systematic SAR study of substitutions on both the pyridine ring and the 3-quinolinecarbonitrile core established the requirements for optimal activity. The lead compound, 17, showed potent activity in both the Src enzyme assay and cell assays, and demonstrated in vivo anti-tumor activity in a xenograft model.
Assuntos
Aminoquinolinas/química , Compostos de Anilina/química , Antineoplásicos/química , Inibidores de Proteínas Quinases/química , Quinolinas/química , Quinases da Família src/antagonistas & inibidores , Aminoquinolinas/síntese química , Aminoquinolinas/farmacologia , Compostos de Anilina/síntese química , Compostos de Anilina/farmacologia , Animais , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Humanos , Camundongos , Camundongos Nus , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/síntese química , Quinolinas/farmacologia , Ratos , Relação Estrutura-Atividade , Ensaios Antitumorais Modelo de Xenoenxerto , Quinases da Família src/metabolismoRESUMO
Thieno[2,3-b]pyridine-5-carbonitrile 16 with a 4-methyl-5-indolylamine at C-4 and a 5-methoxy-2-(dimethylamino)-methylphenyl group at C-2 had an IC(50) value of 16 nM for the inhibition of PKCtheta. While moderate inhibition of PKCdelta was also observed (IC(50)=130 nM), 16 had IC(50) values of greater than 5 microM against Lyn and other members of the Src kinase family.
Assuntos
Química Farmacêutica/métodos , Indóis/síntese química , Isoenzimas/antagonistas & inibidores , Nitrilas/química , Proteína Quinase C/antagonistas & inibidores , Piridinas/química , Desenho de Fármacos , Inibidores Enzimáticos/farmacologia , Humanos , Indóis/farmacologia , Concentração Inibidora 50 , Modelos Químicos , Nitrilas/síntese química , Nitrilas/farmacologia , Proteína Quinase C-theta , Relação Estrutura-Atividade , Quinases da Família src/antagonistas & inibidoresRESUMO
We earlier reported that 3-pyridinecarbonitriiles with a 4-methylindolyl-5-amino group at C-4 and a phenyl group at C-5 were inhibitors of PKCtheta. Keeping the group at C-4 of the pyridine core constant, we varied the water solubilizing group on the phenyl ring at C-5 and then replaced the C-5 phenyl ring with several monocyclic heteroaryl rings, including furan, thiophene and pyridine. Analog 6e with a 4-methylindol-5-ylamino group at C-4 and a 5-[(4-methylpiperazin-1-yl)methyl]-2-furyl group C-5 had an IC50 value of 4.5 nM for the inhibition of PKCtheta.
Assuntos
Isoenzimas/antagonistas & inibidores , Isoenzimas/metabolismo , Nitrilas/química , Nitrilas/farmacologia , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/química , Piridinas/farmacologia , Animais , Concentração Inibidora 50 , Isoenzimas/genética , Camundongos , Camundongos Knockout , Proteína Quinase C/genética , Proteína Quinase C-theta , Relação Estrutura-Atividade , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismoRESUMO
A series of 4-indolylamino-5-phenyl-3-pyridinecarbonitrile inhibitors of PKCtheta were synthesized as potential anti-inflammatory agents. The effects of specific substitution on the 5-phenyl moiety and variations of the positional isomers of the 4-indolylamino substituent were explored. This study led to the discovery of compound 12d, which had an IC(50) value of 18nM for the inhibition of PKCtheta.
Assuntos
Isoenzimas/antagonistas & inibidores , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Piridinas/síntese química , Trifosfato de Adenosina/química , Animais , Anti-Inflamatórios/farmacologia , Química Farmacêutica/métodos , Desenho de Fármacos , Humanos , Concentração Inibidora 50 , Isoenzimas/química , Camundongos , Modelos Químicos , Estrutura Molecular , Isoformas de Proteínas , Proteína Quinase C/química , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/farmacologia , Piridinas/farmacologia , Relação Estrutura-AtividadeRESUMO
A series of 5-vinyl-3-pyridinecarbonitriles were synthesized and evaluated as PKCtheta inhibitors. The systematic optimization of 4-[(4-methyl-1H-indol-5-yl)amino]-5-[(E)-2-phenylvinyl]-3-pyridinecarbonitrile 3 resulted in the identification of compound 23e as a potent PKCtheta inhibitor with good selectivity over PKCdelta.
Assuntos
Isoenzimas/antagonistas & inibidores , Nitrilas/química , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Piridinas/química , Animais , Humanos , Isoenzimas/metabolismo , Microssomos/metabolismo , Nitrilas/síntese química , Nitrilas/farmacologia , Proteína Quinase C/metabolismo , Proteína Quinase C-delta/antagonistas & inibidores , Proteína Quinase C-delta/metabolismo , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/síntese química , Piridinas/farmacologia , Ratos , Relação Estrutura-AtividadeRESUMO
The key intermediate, 4-chloro-5-iodo-3-pyridinecarbonitrile, allowed for ready optimization of the PKCtheta inhibitory activity of a series of 3-pyridinecarbonitriles. Analog 13b with a 4-methylindol-5-ylamino group at C-4 and a 4-(2-(4-methylpiperazin-1-yl)ethoxy)phenyl group at C-5 had an IC(50) value of 7.4nM for the inhibition of PKCtheta.
Assuntos
Indóis/química , Isoenzimas/antagonistas & inibidores , Nitrilas/química , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Piridinas/química , Animais , Indóis/síntese química , Indóis/farmacologia , Isoenzimas/metabolismo , Camundongos , Nitrilas/síntese química , Nitrilas/farmacologia , Proteína Quinase C/metabolismo , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/síntese química , Piridinas/farmacologia , Relação Estrutura-AtividadeRESUMO
We previously reported that a 3-pyridinecarbonitrile analog with a furan substituent at C-5 and a 4-methylindol-5-ylamino substituent at C-4, 1, was a potent inhibitor of PKCtheta (IC50=4.5 nM). Replacement of the C-5 furan ring of 1 with bicyclic heteroaryl rings, led to compounds with significantly improved potency against PKCtheta. Analog 6b with a 4-methylindol-5-ylamino group at C-4 and a 5-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-2-yl group at C-5 had an IC50 value of 0.28 nM for the inhibition of PKCtheta.
Assuntos
Aminopiridinas/química , Isoenzimas/antagonistas & inibidores , Nitrilas/química , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Piridinas/química , Aminopiridinas/síntese química , Aminopiridinas/farmacologia , Animais , Benzofuranos/síntese química , Benzofuranos/química , Benzofuranos/farmacologia , Meia-Vida , Humanos , Interleucina-2/metabolismo , Isoenzimas/metabolismo , Camundongos , Microssomos Hepáticos/metabolismo , Nitrilas/síntese química , Nitrilas/farmacologia , Proteína Quinase C/metabolismo , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/síntese química , Piridinas/farmacologia , Ratos , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Insulin-like growth factor receptor (IGF-1R) is a growth factor receptor tyrosine kinase that acts as a critical mediator of cell proliferation and survival. Inhibitors of this receptor are believed to provide a new target in cancer therapy. We previously reported an isoquinolinedione series of IGF-1R inhibitors. Now we have identified a series of 3-cyanoquinoline compounds that are low nanomolar inhibitors of IGF-1R. The strategies, synthesis, and SAR behind the cyanoquinoline scaffold will be discussed.
Assuntos
Antineoplásicos/síntese química , Nitrilas/síntese química , Quinolinas/síntese química , Receptor IGF Tipo 1/antagonistas & inibidores , Humanos , Nitrilas/farmacologia , Quinolinas/farmacologia , Relação Estrutura-AtividadeRESUMO
PKCtheta is a serine/threonine kinase involved in the regulation of IL2 production in T cells. It has recently become an attractive therapeutic target for a variety of immunological disorders. We describe the optimization of the enzymatic and cellular potency of a series of 5-vinyl-3-pyridinecarbonitrile inhibitors of PKCtheta. A binding model was developed that explains much of the SAR observed for this series, including the enzymatic potency observed for 19. An analysis of functional potency against various physiochemical parameters suggests that cellular potency is correlated with LogD(7.4), but not with cLogP, PAMPA permeability, or TPSA.
Assuntos
Isoenzimas/antagonistas & inibidores , Nitrilas/síntese química , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Piridinas/síntese química , Compostos de Vinila/síntese química , Animais , Simulação por Computador , Concentração Inibidora 50 , Isoenzimas/metabolismo , Cinética , Espectroscopia de Ressonância Magnética , Camundongos , Camundongos Endogâmicos C57BL , Modelos Moleculares , Nitrilas/química , Nitrilas/farmacologia , Proteína Quinase C/metabolismo , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Piridinas/química , Piridinas/farmacologia , Espectrometria de Massas por Ionização por Electrospray , Relação Estrutura-Atividade , Compostos de Vinila/química , Compostos de Vinila/farmacologiaRESUMO
A series of 2-alkenyl thieno[2,3-b]pyridine inhibitors of PKCtheta were synthesized as potential inflammatory modulators. This series led to the discovery of 2-alkenyl amides, which are exceptionally potent and selective inhibitors of PKCtheta. Compound 8 has an IC(50) of 3.8nM against PKCtheta and shows excellent selectivity over a variety of PKC isoforms.
Assuntos
Isoenzimas/antagonistas & inibidores , Nitrilas/síntese química , Nitrilas/farmacologia , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Tiofenos/síntese química , Tiofenos/farmacologia , Animais , Técnicas de Química Combinatória , Camundongos , Modelos Químicos , Estrutura Molecular , Nitrilas/química , Proteína Quinase C-theta , Inibidores de Proteínas Quinases/química , Relação Estrutura-Atividade , Tiofenos/químicaRESUMO
The thieno[2,3-b]pyridine-5-carbonitrile with a 5-indolylamine at C-4 and a phenyl group at C-2 had a moderate activity against PKCtheta. Optimization of the groups at C-4 and C-2 led to analog 29, which has an IC(50) value of 7.5nM for the inhibition of PKCtheta.
Assuntos
Antineoplásicos/farmacologia , Isoenzimas/antagonistas & inibidores , Nitrilas/farmacologia , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Piridinas/farmacologia , Tiofenos/farmacologia , Animais , Antineoplásicos/síntese química , Linhagem Celular Tumoral/efeitos dos fármacos , Linhagem Celular Tumoral/patologia , Concentração Inibidora 50 , Camundongos , Camundongos Knockout , Modelos Químicos , Nitrilas/síntese química , Inibidores de Proteínas Quinases/síntese química , Piridinas/síntese química , Ratos , Relação Estrutura-Atividade , Tiofenos/síntese químicaRESUMO
A more efficient preparation of 4-[(2,4-dichloro-5-methoxyphenyl)amino]-7-fluoro-6-methoxy-3-quinolinecarbonitrile (2), the penultimate intermediate in the synthesis of bosutinib (1a), was developed. New 7-alkoxy-4-phenylamino-3-quinolinecarbonitrile Src inhibitors were prepared from 5 and 9, the 6-ethoxy and 6-hydrogen analogs of 2. In addition, the fluoro group of 2 was readily displaced by primary and secondary amines to give 7-amino analogs. Two of these 7-amino analogs, 15 and 18, were potent Src inhibitors with in vivo activity.
Assuntos
Nitrilas/síntese química , Inibidores de Proteínas Quinases/síntese química , Quinolinas/síntese química , Quinases da Família src/antagonistas & inibidores , Aminas , Animais , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , Nitrilas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/farmacologia , Ratos , Relação Estrutura-AtividadeRESUMO
With high-throughput screening, substituted dibenzo[c,f][2,7]naphthyridine 1 was identified as a novel potent and selective phosphoinositide-dependent kinase-1 (PDK-1) inhibitor. Various regions of the lead molecule were explored to understand the SAR requirement for this scaffold. The crystal structure of 1 with kinase domain of PDK-1 confirmed the binding in the active site. The key interaction of the molecule with the active site residues, observed SAR, and the biological profile are discussed in detail.
Assuntos
Naftiridinas/síntese química , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Quinases Dependentes de 3-Fosfoinositídeo , Sítios de Ligação , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Naftiridinas/química , Proteínas Serina-Treonina Quinases/química , Relação Estrutura-AtividadeRESUMO
Src up-regulation is a common event in human cancers. In colorectal cancer, increased Src levels are an indicator of poor prognosis, and progression to metastatic disease is associated with substantial increases in Src activity. Therefore, we examined the activity of SKI-606, a potent inhibitor of Src and Abl kinases, against colon tumor lines in vitro and in s.c. tumor xenograft models. SKI-606 inhibited Src autophosphorylation with an IC(50) of approximately 0.25 micromol/L in HT29 cells. Phosphorylation of Tyr(925) of focal adhesion kinase, a Src substrate, was reduced by similar concentrations of inhibitor. Antiproliferative activity on plastic did not correlate with Src inhibition in either HT29 or Colo205 cells (IC(50)s, 1.5 and 2.5 micromol/L, respectively), although submicromolar concentrations of SKI-606 inhibited HT29 cell colony formation in soft agar. SKI-606 also caused loosely aggregated Colo205 spheroids to condense into compact spheroids. On oral administration to nude mice at the lowest efficacious dose, peak plasma concentrations of approximately 3 micromol/L, an oral bioavailability of 18%, and a t(1/2) of 8.6 hours were observed. SKI-606 was orally active in s.c. colon tumor xenograft models and caused substantial reductions in Src autophosphorylation on Tyr(418) in HT29 and Colo205 tumors. SKI-606 inhibited HT29 tumor growth on once daily administration, whereas twice daily administration was necessary to inhibit Colo205, HCT116, and DLD1 tumor growth. These results support development of SKI-606 as a therapeutic agent for treatment of colorectal cancer.