RESUMEN
OBJECTIVE: TGF-beta plays a significant role in vascular injury-induced stenosis. This study evaluates the efficacy of a novel, small molecule inhibitor of ALK5/ALK4 kinase, in the rat carotid injury model of vascular fibrosis. METHODS AND RESULTS: The small molecule, SM16, was shown to bind with high affinity to ALK5 kinase ATP binding site using a competitive binding assay and biacore analysis. SM16 blocked TGF-beta and activin-induced Smad2/3 phosphorylation and TGF-beta-induced plasminogen activator inhibitor (PAI)-luciferase activity in cells. Good overall selectivity was demonstrated in a large panel of kinase assays, but SM16 also showed nanomolar inhibition of ALK4 and weak (micromolar) inhibition of Raf and p38. In the rat carotid injury model, SM16 dosed once daily orally at 15 or 30 mg/kg SM16 for 14 days caused significant inhibition of neointimal thickening and lumenal narrowing. SM16 also prevented induction of adventitial smooth muscle alpha-actin-positive myofibroblasts and the production of intimal collagen, but did not decrease the percentage of proliferative cells. CONCLUSIONS: These results are the first to demonstrate the efficacy of an orally active, small-molecule ALK5/ALK4 inhibitor in a vascular fibrosis model and suggest the potential therapeutic application of these inhibitors in vascular fibrosis.
Asunto(s)
Compuestos de Azabiciclo/farmacología , Traumatismos de las Arterias Carótidas/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Receptores de Factores de Crecimiento Transformadores beta/antagonistas & inhibidores , Receptores de Activinas Tipo I/antagonistas & inhibidores , Adenosina Trifosfato/metabolismo , Administración Oral , Animales , Compuestos de Azabiciclo/administración & dosificación , Compuestos de Azabiciclo/metabolismo , Sitios de Unión , Traumatismos de las Arterias Carótidas/patología , Traumatismos de las Arterias Carótidas/fisiopatología , Línea Celular , Fibroblastos/efectos de los fármacos , Fibroblastos/patología , Fibrosis , Humanos , Masculino , Mioblastos del Músculo Liso/efectos de los fármacos , Mioblastos del Músculo Liso/patología , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/metabolismo , Ratas , Ratas Sprague-Dawley , Receptor Tipo I de Factor de Crecimiento Transformador beta , Factor de Crecimiento Transformador beta/fisiologíaRESUMEN
Novel tricyclic imidazoline antagonists of the adenosine A1 receptor are described. For key compounds, the selectivity level over other adenosine receptor subtypes is examined along with their in vivo effects in a rat diuresis model. Compound 14, the (R)-isomer of 7,8-dihydro-8-ethyl-2-(4-bicyclo[2.2.2]octan-1-ol)-4-propyl-1H-imidazo[2,1-i]purin-5(4H)-one, is a particularly potent adenosine A1 receptor antagonist with good selectivity over the other three adenosine receptor subtypes: A1 (human) Ki=22 nM; A2A (human) Ki=4400 nM; A2B (human) Ki=580 nM; A3 (human) Ki>or=10,000 nM. Imidazoline 14 is a competitive adenosine A1 receptor antagonist with a pA2 value of 8.88 and is highly soluble in water (>100 mg/mL). In addition, it has an oral bioavailability of 84% and an oral half-life of 3.8 h in rats. When orally administered in a rat diuresis model, compound 14 promoted sodium excretion (ED50=0.01 mg/kg). This level of efficacy is comparable to that of BG9928, a selective adenosine A1 receptor antagonist that is currently in clinical trials as a treatment for congestive heart failure. Additional modifications to 14 also showed that the bridgehead hydroxyl group could be replaced with a propionic acid (compound 36) without a significant loss in binding affinity or in vivo activity.
Asunto(s)
Antagonistas del Receptor de Adenosina A1 , Compuestos Bicíclicos con Puentes/síntesis química , Compuestos Heterocíclicos con 3 Anillos/síntesis química , Imidazolinas/síntesis química , Purinas/síntesis química , Administración Oral , Animales , Disponibilidad Biológica , Compuestos Bicíclicos con Puentes/farmacocinética , Compuestos Bicíclicos con Puentes/farmacología , Corteza Cerebral/metabolismo , Cuerpo Estriado/metabolismo , Semivida , Atrios Cardíacos/efectos de los fármacos , Compuestos Heterocíclicos con 3 Anillos/farmacocinética , Compuestos Heterocíclicos con 3 Anillos/farmacología , Humanos , Imidazolinas/farmacocinética , Imidazolinas/farmacología , Técnicas In Vitro , Natriuresis/efectos de los fármacos , Purinas/farmacocinética , Purinas/farmacología , Ensayo de Unión Radioligante , Ratas , Receptores de Adenosina A2/metabolismo , Solubilidad , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
In the search for a selective adenosine A1 receptor antagonist with greater aqueous solubility than the compounds currently in clinical trials as diuretics, a series of 1,4-substituted 8-cyclohexyl and 8-bicyclo[2.2.2]octylxanthines were investigated. The binding affinities of a variety of cyclohexyl and bicyclo[2.2.2]octylxanthines for the rat and human adenosine A1, A2A, A2B, and A3 receptors are presented. Bicyclo[2.2.2]octylxanthine 16 exhibited good pharmaceutical properties and in vivo activity in a rat diuresis model (ED50=0.3 mg/kg po). Optimization of the bridgehead substituent led to propionic acid 29 (BG9928), which retained high potency (hA1, Ki=7 nM) and selectivity for the adenosine A1 receptor (915-fold versus adenosine A2A receptor; 12-fold versus adenosine A2B receptor) with improved oral efficacy in the rat diuresis model (ED50=0.01 mg/kg) as well as high oral bioavailability in rat, dog, and cynomolgus monkey.
Asunto(s)
Antagonistas del Receptor de Adenosina A1 , Xantinas/síntesis química , Administración Oral , Animales , Disponibilidad Biológica , Encéfalo/metabolismo , Línea Celular , Cricetinae , Cricetulus , Diuresis/efectos de los fármacos , Perros , Atrios Cardíacos/efectos de los fármacos , Humanos , Técnicas In Vitro , Macaca fascicularis , Masculino , Ensayo de Unión Radioligante , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , Xantinas/farmacocinética , Xantinas/farmacologíaRESUMEN
During the search for second-generation adenosine A(1) receptor antagonist alternatives to the clinical candidate 8-(3-oxa-tricyclo[3.2.1.0(2,4)]oct-6-yl)-1,3-dipropyl-3,7-dihydro-purine-2,6-dione (BG9719), we developed a series of novel xanthines substituted with norbornyl-lactones that possessed high binding affinities for adenosine A(1) receptors and in vivo activity.