RESUMEN
The current study was designed to investigate the influence of allosteric effectors on the metabolism of the prototypical cytochrome P450 (CYP) 3A4 substrate midazolam (MDZ), and on the determination in vitro time-dependent inhibition (TDI) of CYP3A4 using human liver microsomes (HLM). As the concentration of midazolam increased to 250 µM in HLMs, homotropic cooperativity resulted in a decrease in the 1'-hydroxymidazolam to 4-hydroxymidazolam ratio to a maximum of 1.1. The presence of varying concentrations of testosterone, progesterone (PGS), or carbamazepine (CBZ) in HLMs with MDZ could recapitulate the effect of homotropic cooperativity such that the formation rates of the 1'hydroxymidazolam and 4-hydroxymidazolam were equal even at low concentrations of MDZ. The presence of PGS (10 or 100 µM) and CBZ (100 or 1000 µM) in in vitro TDI determination of four known CYP3A4 time-dependent inactivators (clarithromycin, troleandomycin, mibefradil, raloxifene) simultaneously decreased potency and inactivation rate constant, resulting in fold changes in inactivation efficiency on average of 1.6-fold and 13-fold for the low and high concentrations of allosteric modulator tested, respectively. The formation of a metabolic-intermediate complex (MIC) for clarithromycin and troleandomycin decreased in the presence of the allosteric modulators in a concentration-dependent manner, reaching a new steady state formation that could not be overcome with increased incubation time. Maximum reduction of the MIC formed by clarithromycin was up to â¼91%, while troleandomycin MIC decreased up to â¼31%. These findings suggest that the absence of endogenous allosteric modulators may contribute to the poor translation of HLM-based drug-drug interaction predictions. SIGNIFICANCE STATEMENT: The reported overprediction of in vitro human liver microsome time-dependent inhibition of CYP3A4 and observed drug interactions in vivo remains an issue in drug development. We provide characterization of allosteric modulators on the CYP3A4 metabolism of the prototypical substrate midazolam, demonstrating the ability of the modulators to recapitulate the homotropic cooperativity of midazolam. Furthermore, we demonstrate that allosteric heterotropic cooperativity of CYP3A4 can impact the time-dependent inhibition kinetics of known mechanisms-based inhibitors, providing a potential mechanism to explain the overprediction.
Asunto(s)
Citocromo P-450 CYP3A , Midazolam , Humanos , Citocromo P-450 CYP3A/metabolismo , Midazolam/farmacología , Midazolam/metabolismo , Troleandomicina/metabolismo , Troleandomicina/farmacología , Claritromicina , Microsomas Hepáticos/metabolismo , Interacciones Farmacológicas , Carbamazepina/farmacología , Carbamazepina/metabolismoRESUMEN
Two 2-aminoimidazole-based inhibitors, LY3031207 (1) and LY3023703 (2), of the microsomal prostaglandin E synthase-1 (mPGES-1) enzyme were found to cause drug-induced liver injury (DILI) in humans. We studied imidazole ring substitutions to successfully mitigate reactive metabolite (RM) formation. These studies support the conclusion that RM formation may play a role in the observations of DILI and the consideration of 2-aminoimidazoles as structure alerts, due to the high likelihood of bioactivation to generate RMs.
Asunto(s)
Enfermedad Hepática Inducida por Sustancias y Drogas/etiología , Imidazoles/farmacología , Prostaglandina-E Sintasas/antagonistas & inhibidores , Humanos , Imidazoles/efectos adversos , Imidazoles/metabolismo , Retirada de Medicamento por Seguridad , Relación Estructura-ActividadRESUMEN
The disposition and metabolism of a Chk-1 inhibitor (LY2603618) was characterized following a 1-h intravenous administration of a single 250-mg dose of [14C]LY2603618 (50 µCi) to patients with advanced or metastatic solid tumors. LY2603618 was well tolerated with no clinically significant adverse events. Study was limited to three patients due to challenges of conducting ADME studies in patients with advanced cancer. Plasma, urine and feces were analyzed for radioactivity, LY2603618 and metabolites. LY2603618 had a half-life of 10.5 h and was the most abundant entity in plasma, accounting for approximately 69% of total plasma radioactivity. The second most abundant metabolites, H2 and H5, accounted for <10% of total circulating radioactivity. The major route of clearance was via CYP450 metabolism. The mean total recovery of radioactivity was 83%, with approximately 72% of the radioactivity recovered in the feces and approximately 11% in the urine. LY2603618 represented approximately 6% and 3% of the administered dose in feces and urine, respectively. A total of 12 metabolites were identified. In vitro phenotyping indicated that CYP3A4 was predominantly responsible for the metabolic clearance of LY2603618. Additionally, aldehyde oxidase was involved in the formation of a unique human and non-human primate metabolite, H5.
Asunto(s)
Neoplasias/tratamiento farmacológico , Compuestos de Fenilurea/farmacocinética , Pirazinas/farmacocinética , Administración Intravenosa , Anciano , Cromatografía Liquida , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Heces/química , Femenino , Semivida , Humanos , Masculino , Tasa de Depuración Metabólica , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Persona de Mediana Edad , Compuestos de Fenilurea/administración & dosificación , Pirazinas/administración & dosificación , Espectrometría de Masas en TándemRESUMEN
LY2090314 (3-[9-fluoro-2-(piperidin-1-ylcarbonyl)-1,2,3,4-tetrahydro[1,4]diazepino[6,7,1-hi]indol-7-yl]-4-imidazo[1,2-a]pyridin-3-yl-1H-pyrrole-2,5-dione) is an intravenous glycogen synthase kinase-3 inhibitor in oncology trials. Drug disposition was characterized after intravenous infusion of [(14)C]LY2090314 to rats and dogs, and was related to available clinical data. LY2090314 exhibited high clearance (approximating hepatic blood flow) and a moderate volume of distribution (â¼1-2 l/kg) resulting in rapid elimination (half-life â¼0.4, 0.7, and 1.8-3.4 hours in rats, dogs, and humans, respectively). Scaled clearance from liver microsomes accurately predicted perfusion-limited clearance across species. LY2090314 was cleared by extensive metabolism, and the numerous metabolites were rapidly excreted into feces via bile (69-97% of dose; 62-93% within 0-24 hours); urinary recovery of drug-related material was low (≤3% of dose). Despite extensive metabolism, in rats and humans the parent compound was the sole identifiable drug-related moiety in plasma. Even in Mdr1a-, Bcrp-, and Mrp2-knockout rats, LY2090314 metabolites did not appear in circulation, and their urinary excretion was not enhanced, because the hypothesized impaired biliary excretion of metabolites in the absence of these canalicular transporters was not observed. Canine metabolite disposition was generally similar, with the notable exception of dog-unique LY2090314 glucuronide. This conjugate was formed in the dog liver and was preferentially excreted into the blood, where it accounted for the majority of circulating radioactivity at later times, and was predominantly recovered in urine (16% of dose). In conclusion, LY2090314 was rapidly cleared by extensive metabolism with negligible circulating metabolite exposures due to biliary excretion of metabolites into feces with no apparent intestinal reabsorption.
Asunto(s)
Antineoplásicos/farmacocinética , Glucógeno Sintasa Quinasa 3/antagonistas & inhibidores , Compuestos Heterocíclicos con 3 Anillos/farmacocinética , Maleimidas/farmacocinética , Inhibidores de Proteínas Quinasas/farmacocinética , Animales , Antineoplásicos/metabolismo , Bilis/metabolismo , Perros , Heces/química , Glucógeno Sintasa Quinasa 3 beta , Humanos , Masculino , Microsomas Hepáticos/metabolismo , Inhibidores de Proteínas Quinasas/metabolismo , Ratas , Orina/químicaRESUMEN
Dark liver pigmentation was observed in F344 rats in a subchronic toxicology study after daily dosing of LY368842 glycolate. In addition, green-colored urine was observed in some animals. To identify the source of the pigment and its potential for toxic consequences, the liver pigment was isolated from the liver tissue of rats. The resulting material was a dark brown to black powder that was insoluble in water, organic solvents, or a tissue-solubilizing agent. Several techniques, such as chemical degradation, HPLC, tandem mass spectrometry (LC/MS/MS), (1)H NMR, and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), were employed to characterize the dark liver pigment. Following oxidative degradation of the isolated pigment, degradation products related to LY368842 were identified or tentatively identified using LC/MS/MS. Two degradation products had the same protonated molecular ion at m/z 505, which is 30 amu higher than that of LY368842. The major m/z 505 product has been identified as the indole-2,3-dione oxidative product based on (1)H NMR data and confirmed by an authentic standard. In addition, monohydroxylated product was also identified in the degradation mixture. These degradation products were consistent with the metabolites found in vivo in rats. MALDI-MS analyses of liver and urine pigment both identified a product with a protonated molecular ion at m/z 977, suggesting formation of indirubin-like and indigo-like pigments. The results obtained suggest that the oxidative metabolites of LY368842 played a key role in the formation of the liver and urine pigments.
Asunto(s)
Agonistas de Receptores Adrenérgicos beta 3 , Agonistas Adrenérgicos beta/farmacología , Indoles/antagonistas & inhibidores , Hígado/metabolismo , Pigmentos Biológicos/metabolismo , Piridinas/antagonistas & inhibidores , Animales , Isatina/análogos & derivados , Isatina/análisis , Hígado/química , Hígado/efectos de los fármacos , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Estructura Molecular , Oxidación-Reducción , Pigmentos Biológicos/química , Pigmentos Biológicos/orina , Ratas , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
The metabolism and pharmacokinetics of moxonidine, a potent central-acting antihypertensive agent, were studied in four healthy subjects after a single oral administration of approximately 1 mg (approximately 60 muCi) of [(14)C(3)]moxonidine. Moxonidine was rapidly absorbed, with peak plasma concentration achieved between 0.5 to 2 h postdose. The maximal plasma concentration and the area under the curve of unchanged moxonidine are lower than those determined for radioactivity, indicating presence of circulating metabolite(s). The total recovery of radiocarbon over 120 h ranged from 99.6 to 105.2%, with 92.3 to 103.3% of the radioactivity excreted in the urine and only 1.9 to 7.3% of the dose excreted in the feces. Thus, renal elimination represented the principal route of excretion of radioactivity. Metabolites of moxonidine were identified in urine and plasma samples by high performance liquid chromatography and liquid chromatography-tandem mass spectrometry. Oxidation of moxonidine on the methyl group or on the imidazoline ring resulted in the formation of hydroxymethyl moxonidine, hydroxy moxonidine, dihydroxy moxonidine, and dehydrogenated moxonidine. Metabolite profiling results indicated that parent moxonidine was the most abundant component in the urine. The dehydrogenated moxonidine was the major urinary metabolite as well as the major circulating metabolite. Moxonidine also underwent phase II metabolism, generating a cysteine conjugate. In summary, moxonidine is well absorbed after oral administration. The major clearance pathway for moxonidine in humans is via renal elimination. Furthermore, seven metabolites were identified with three metabolites unique to humans.