RESUMEN
While an initial clinical absorption, distribution, metabolism, and excretion (ADME) study (Study 1; N = 6) with 100 mg/100 µCi [14 C]lorlatinib, radiolabeled on the carbonyl carbon, confirmed that the primary metabolic pathways for lorlatinib are oxidation (N-demethylation, N-oxidation) and N-glucuronidation, it also revealed an unanticipated, intramolecular cleavage metabolic pathway of lorlatinib, yielding a major circulating benzoic acid metabolite (M8), and an unlabeled pyrido-pyrazole substructure. Concerns regarding the fate of unknown metabolites associated with this intramolecular cleavage pathway led to conduct of a second ADME study (Study 2; N = 6) of identical design but with the radiolabel positioned on the pyrazole ring. Results were similar with respect to the overall mass balance, lorlatinib plasma exposures, and metabolic profiles in excreta for the metabolites that retained the radiolabel in both studies. Differences were observed in plasma total radioactivity exposures (2-fold area under the plasma concentration-time curve from time 0 to infinity difference) and relative ratios of the percentage of dose recovered in urine vs feces (48% vs 41% in Study 1; 28% vs 64% in Study 2). In addition, an approximately 3-fold difference in the mean molar exposure ratio of M8 to lorlatinib was observed for values derived from metabolic profiling data relative to those derived from specific bioanalytical methods (0.5 vs 1.4 for Studies 1 and 2, respectively). These interstudy differences were attributed to a combination of factors, including alteration of radiolabel position, orthogonal analytical methodologies, and intersubject variability, and illustrate that results from clinical ADME studies are not unambiguous and should be interpreted within the context of the specific study design considerations.
Asunto(s)
Radioisótopos de Carbono/metabolismo , Radioisótopos de Carbono/farmacocinética , Lactamas Macrocíclicas/metabolismo , Lactamas Macrocíclicas/farmacocinética , Administración Oral , Adolescente , Adulto , Aminopiridinas , Biotransformación , Radioisótopos de Carbono/administración & dosificación , Radioisótopos de Carbono/química , Vías de Eliminación de Fármacos , Heces/química , Voluntarios Sanos , Humanos , Lactamas , Lactamas Macrocíclicas/administración & dosificación , Lactamas Macrocíclicas/química , Masculino , Persona de Mediana Edad , Modelos Biológicos , Pirazoles , Soluciones , Adulto JovenRESUMEN
1. The metabolism, excretion and pharmacokinetics of glasdegib (PF-04449913) were investigated following administration of a single oral dose of 100 mg/100 µCi [14C]glasdegib to six healthy male volunteers (NCT02110342). 2. The peak concentrations of glasdegib (890.3 ng/mL) and total radioactivity (1043 ngEq/mL) occurred in plasma at 0.75 hours post-dose. The AUCinf were 8469 ng.h/mL and 12,230 ngEq.h/mL respectively, for glasdegib and total radioactivity. 3. Mean recovery of [14C]glasdegib-related radioactivity in excreta was 91% of the administered dose (49% in urine and 42% in feces). Glasdegib was the major circulating component accounting for 69% of the total radioactivity in plasma. An N-desmethyl metabolite and an N-glucuronide metabolite of glasdegib represented 8% and 7% of the circulating radioactivity, respectively. Glasdegib was the major excreted component in urine and feces, accounting for 17% and 20% of administered dose in the 0-120 hour pooled samples, respectively. Other metabolites with abundance <3% of the total circulating radioactivity or dose in plasma or excreta were hydroxyl metabolites, a desaturation metabolite, N-oxidation and O-glucuronide metabolites. 4. Elimination of [14C]glasdegib-derived radioactivity was essentially complete, with similar contribution from urinary and fecal routes. Oxidative metabolism appears to play a significant role in the biotransformation of glasdegib.
Asunto(s)
Bencimidazoles/farmacocinética , Compuestos de Fenilurea/farmacocinética , Administración Oral , Adulto , Biotransformación , Glucurónidos/metabolismo , Voluntarios Sanos , Humanos , Masculino , Adulto JovenRESUMEN
We report the preclinical evaluation of PF-06463922, a potent and brain-penetrant ALK/ROS1 inhibitor. Compared with other clinically available ALK inhibitors, PF-06463922 displayed superior potency against all known clinically acquired ALK mutations, including the highly resistant G1202R mutant. Furthermore, PF-06463922 treatment led to regression of EML4-ALK-driven brain metastases, leading to prolonged mouse survival, in a superior manner. Finally, PF-06463922 demonstrated high selectivity and safety margins in a variety of preclinical studies. These results suggest that PF-06463922 will be highly effective for the treatment of patients with ALK-driven lung cancers, including those who relapsed on clinically available ALK inhibitors because of secondary ALK kinase domain mutations and/or brain metastases.
Asunto(s)
Antineoplásicos/administración & dosificación , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/secundario , Resistencia a Antineoplásicos/efectos de los fármacos , Lactamas Macrocíclicas/administración & dosificación , Neoplasias/tratamiento farmacológico , Proteínas Tirosina Quinasas Receptoras/genética , Aminopiridinas , Quinasa de Linfoma Anaplásico , Animales , Antineoplásicos/farmacología , Neoplasias Encefálicas/genética , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Humanos , Lactamas , Lactamas Macrocíclicas/farmacología , Ratones , Mutación , Células 3T3 NIH , Neoplasias/genética , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/farmacología , Pirazoles , Proteínas Tirosina Quinasas Receptoras/antagonistas & inhibidores , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The orally available novel small molecules PF06463922 [(10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h][2,5,11]benzoxadiazacyclotetradecine-3-carbonitrile] and PF06471402 [(10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(azeno)pyrazolo[4,3-h][2,5,11]benzoxadiazacyclo-tetradecine-3-carbonitrile] are second-generation anaplastic lymphoma kinase (ALK) inhibitors targeted to both naïve and resistant patients with non-small cell lung cancer (NSCLC) to the first-generation ALK inhibitor crizotinib. The objectives of the present study were to characterize and compare the pharmacokinetic-pharmacodynamic (PKPD) relationships of PF06463922 and PF06471402 for target modulation in tumor and antitumor efficacy in athymic mice implanted with H3122 NSCLC cells expressing a crizotinib-resistant echinoderm microtubule-associated protein-like 4 (EML4)-ALK mutation, EML4-ALK(L1196M). Furthermore, the PKPD relationships for these ALK inhibitors were evaluated and compared between oral administration and subcutaneous constant infusion (i.e., between different pharmacokinetic [PK] profiles). Oral and subcutaneous PK profiles of these ALK inhibitors were adequately described by a one-compartment PK model. An indirect response model extended with a modulator fit the time courses of PF06463922- and PF06471402-mediated target modulation (i.e., ALK phosphorylation) with an estimated unbound EC50,in vivo of 36 and 20 nM, respectively, for oral administration, and 100 and 69 nM, respectively, for subcutaneous infusion. A drug-disease model based on the turnover concept fit tumor growth curves inhibited by PF06463922 and PF06471402 with estimated unbound tumor stasis concentrations of 51 and 27 nM, respectively, for oral administration, and 116 and 70 nM, respectively, for subcutaneous infusion. Thus, the EC50,in vivo to EC60,in vivo estimates for ALK inhibition corresponded to the concentrations required tumor stasis in all cases, suggesting that the pharmacodynamic relationships of target modulation to antitumor efficacy were consistent among the ALK inhibitors, even when the PK profiles with different administration routes were considerably different.
Asunto(s)
Antineoplásicos/farmacología , Antineoplásicos/farmacocinética , Inhibidores de Proteínas Quinasas/farmacología , Inhibidores de Proteínas Quinasas/farmacocinética , Proteínas Tirosina Quinasas Receptoras/antagonistas & inhibidores , Proteínas Tirosina Quinasas Receptoras/metabolismo , Aminopiridinas , Quinasa de Linfoma Anaplásico , Animales , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Línea Celular Tumoral , Crizotinib , Femenino , Lactamas , Lactamas Macrocíclicas/farmacocinética , Lactamas Macrocíclicas/farmacología , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/metabolismo , Ratones , Ratones Desnudos , Proteínas Asociadas a Microtúbulos/metabolismo , Modelos Biológicos , Pirazoles/farmacocinética , Pirazoles/farmacología , Piridinas/farmacocinética , Piridinas/farmacología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
An orally available macrocyclic small molecule, PF06463922 [(10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h][2,5,11]benzoxadiazacyclotetradecine-3-carbonitrile], is a selective inhibitor of anaplastic lymphoma kinase (ALK) and c-Ros oncogene 1 (ROS1). The objectives of the present study were to characterize the pharmacokinetic-pharmacodynamic relationships of PF06463922 between its systemic exposures, pharmacodynamic biomarker (target modulation), and pharmacologic response (antitumor efficacy) in athymic mice implanted with H3122 non-small cell lung carcinomas expressing echinoderm microtubule-associated protein-like 4 (EML4)-ALK mutation (EML4-ALK(L1196M)) and with NIH3T3 cells expressing CD74-ROS1. In these nonclinical tumor models, PF06463922 was orally administered to animals with EML4-ALK(L1196M) and CD74-ROS1 at twice daily doses of 0.3-20 and 0.01-3 mg/kg per dose, respectively. Plasma concentration-time profiles of PF06463922 were adequately described by a one-compartment pharmacokinetic model. Using the model-simulated plasma concentrations, a pharmacodynamic indirect response model with a modulator sufficiently fit the time courses of target modulation (i.e., ALK phosphorylation) in tumors of EML4-ALK(L1196M)-driven models with EC50,in vivo of 36 nM free. A drug-disease model based on an indirect response model reasonably fit individual tumor growth curves in both EML4-ALK(L1196M)- and CD74-ROS1-driven models with the estimated tumor stasis concentrations of 51 and 6.2 nM free, respectively. Thus, the EC60,in vivo (52 nM free) for ALK inhibition roughly corresponded to the tumor stasis concentration in an EML4-ALK(L1196M)-driven model, suggesting that 60% ALK inhibition would be required for tumor stasis. Accordingly, we proposed that the EC60,in vivo for ALK inhibition corresponding to the tumor stasis could be considered a minimum target efficacious concentration of PF06463922 for cancer patients in a phase I trial.
Asunto(s)
Antineoplásicos/sangre , Lactamas Macrocíclicas/farmacocinética , Modelos Biológicos , Inhibidores de Proteínas Quinasas/sangre , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Proteínas Tirosina Quinasas Receptoras/antagonistas & inhibidores , Administración Oral , Aminopiridinas , Quinasa de Linfoma Anaplásico , Animales , Antineoplásicos/administración & dosificación , Antineoplásicos/farmacología , Línea Celular Tumoral , Femenino , Humanos , Lactamas , Lactamas Macrocíclicas/farmacología , Ratones , Células 3T3 NIH , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/farmacología , PirazolesRESUMEN
Although crizotinib demonstrates robust efficacy in anaplastic lymphoma kinase (ALK)-positive non-small-cell lung carcinoma patients, progression during treatment eventually develops. Resistant patient samples revealed a variety of point mutations in the kinase domain of ALK, including the L1196M gatekeeper mutation. In addition, some patients progress due to cancer metastasis in the brain. Using structure-based drug design, lipophilic efficiency, and physical-property-based optimization, highly potent macrocyclic ALK inhibitors were prepared with good absorption, distribution, metabolism, and excretion (ADME), low propensity for p-glycoprotein 1-mediated efflux, and good passive permeability. These structurally unusual macrocyclic inhibitors were potent against wild-type ALK and clinically reported ALK kinase domain mutations. Significant synthetic challenges were overcome, utilizing novel transformations to enable the use of these macrocycles in drug discovery paradigms. This work led to the discovery of 8k (PF-06463922), combining broad-spectrum potency, central nervous system ADME, and a high degree of kinase selectivity.
Asunto(s)
Antineoplásicos/síntesis química , Encéfalo/metabolismo , Lactamas Macrocíclicas/síntesis química , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Proteínas Tirosina Quinasas Receptoras/antagonistas & inhibidores , Aminopiridinas , Quinasa de Linfoma Anaplásico , Animales , Antineoplásicos/farmacocinética , Antineoplásicos/farmacología , Cristalografía por Rayos X , Resistencia a Antineoplásicos , Humanos , Lactamas , Lactamas Macrocíclicas/farmacocinética , Lactamas Macrocíclicas/farmacología , Ratones , Microsomas Hepáticos/metabolismo , Modelos Moleculares , Mutación , Células 3T3 NIH , Pirazoles , Ratas , Proteínas Tirosina Quinasas Receptoras/genética , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Crizotinib (1), an anaplastic lymphoma kinase (ALK) receptor tyrosine kinase inhibitor approved by the U.S. Food and Drug Administration in 2011, is efficacious in ALK and ROS positive patients. Under pressure of crizotinib treatment, point mutations arise in the kinase domain of ALK, resulting in resistance and progressive disease. The successful application of both structure-based and lipophilic-efficiency-focused drug design resulted in aminopyridine 8e, which was potent across a broad panel of engineered ALK mutant cell lines and showed suitable preclinical pharmacokinetics and robust tumor growth inhibition in a crizotinib-resistant cell line (H3122-L1196M).
Asunto(s)
Resistencia a Antineoplásicos/genética , Mutación Puntual , Inhibidores de Proteínas Quinasas/farmacología , Pirazoles/farmacología , Piridinas/farmacología , Proteínas Tirosina Quinasas Receptoras/genética , Quinasa de Linfoma Anaplásico , Crizotinib , HumanosRESUMEN
The fibroblast growth factor receptors (FGFR) play a major role in angiogenesis and are desirable targets for the development of therapeutics. Groups of Wistar Han rats were dosed orally once daily for 4 days with a small molecule pan-FGFR inhibitor (5mg/kg) or once daily for 6 days with a small molecule MEK inhibitor (3mg/kg). Serum phosphorous and FGF23 levels increased in all rats during the course of the study. Histologically, rats dosed with either drug exhibited multifocal, multiorgan soft tissue mineralization. Expression levels of the sodium phosphate transporter Npt2a and the vitamin D-metabolizing enzymes Cyp24a1 and Cyp27b1 were modulated in kidneys of animals dosed with the pan-FGFR inhibitor. Both inhibitors decreased ERK phosphorylation in the kidneys and inhibited FGF23-induced ERK phosphorylation in vitro in a dose-dependent manner. A separate cardiovascular outcome study was performed to monitor hemodynamics and cardiac structure and function of telemetered rats dosed with either the pan-FGFR inhibitor or MEK inhibitor for 3 days. Both compounds increased blood pressure (~+ 17 mmHg), decreased heart rate (~-75 bpm), and modulated echocardiography parameters. Our data suggest that inhibition of FGFR signaling following administration of either pan-FGFR inhibitor or MEK inhibitor interferes with the FGF23 pathway, predisposing animals to hyperphosphatemia and a tumoral calcinosis-like syndrome in rodents.
Asunto(s)
Sistema Cardiovascular/fisiopatología , Factores de Crecimiento de Fibroblastos/metabolismo , Receptores de Factores de Crecimiento de Fibroblastos/antagonistas & inhibidores , Transducción de Señal , Animales , Secuencia de Bases , Sistema Cardiovascular/metabolismo , Línea Celular , Cartilla de ADN , Factor-23 de Crecimiento de Fibroblastos , Humanos , Fosforilación , Ratas , Ratas WistarRESUMEN
Repaglinide is mainly metabolized by cytochrome P450 enzymes CYP2C8 and CYP3A4, and it is also a substrate to a hepatic uptake transporter, organic anion transporting polypeptide (OATP)1B1. The purpose of this study is to predict the dosing time-dependent pharmacokinetic interactions of repaglinide with rifampicin, using mechanistic models. In vitro hepatic transport of repaglinide, characterized using sandwich-cultured human hepatocytes, and intrinsic metabolic parameters were used to build a dynamic whole-body physiologically-based pharmacokinetic (PBPK) model. The PBPK model adequately described repaglinide plasma concentration-time profiles and successfully predicted area under the plasma concentration-time curve ratios of repaglinide (within ± 25% error), dosed (staggered 0-24 hours) after rifampicin treatment when primarily considering induction of CYP3A4 and reversible inhibition of OATP1B1 by rifampicin. Further, a static mechanistic "extended net-effect" model incorporating transport and metabolic disposition parameters of repaglinide and interaction potency of rifampicin was devised. Predictions based on the static model are similar to those observed in the clinic (average error â¼19%) and to those based on the PBPK model. Both the models suggested that the combined effect of increased gut extraction and decreased hepatic uptake caused minimal repaglinide systemic exposure change when repaglinide is dosed simultaneously or 1 hour after the rifampicin dose. On the other hand, isolated induction effect as a result of temporal separation of the two drugs translated to an approximate 5-fold reduction in repaglinide systemic exposure. In conclusion, both dynamic and static mechanistic models are instrumental in delineating the quantitative contribution of transport and metabolism in the dosing time-dependent repaglinide-rifampicin interactions.
Asunto(s)
Carbamatos/farmacología , Citocromo P-450 CYP3A/biosíntesis , Modelos Teóricos , Transportadores de Anión Orgánico/antagonistas & inhibidores , Piperidinas/farmacología , Rifampin/farmacología , Carbamatos/sangre , Interacciones Farmacológicas , Inducción Enzimática , Humanos , Transportador 1 de Anión Orgánico Específico del Hígado , Piperidinas/sangre , Rifampin/sangreRESUMEN
Inhibition of the Smoothened (Smo) represents a promising therapeutic strategy for treating malignant tumors that are dependent on the Hedgehog (Hh) signaling pathway. PF-5274857 is a novel Smo antagonist that specifically binds to Smo with a K(i) of 4.6 ± 1.1 nmol/L and completely blocks the transcriptional activity of the downstream gene Gli1 with an IC(50) of 2.7 ± 1.4 nmol/L in cells. This Smo antagonist showed robust antitumor activity in a mouse model of medulloblastoma with an in vivo IC(50) of 8.9 ± 2.6 nmol/L. The downregulation of Gli1 is closely linked to the tumor growth inhibition in patched(+/-) medulloblastoma mice. Mathematical analysis of the relationship between the drug's pharmacokinetics and Gli1 pharmacodynamics in patched(+/-) medulloblastoma tumor models yielded similar tumor and skin Gli1 IC(50) values, suggesting that skin can be used as a surrogate tissue for the measurement of tumor Gli1 levels. In addition, PF-5274857 was found to effectively penetrate the blood-brain barrier and inhibit Smo activity in the brain of primary medulloblastoma mice, resulting in improved animal survival rates. The brain permeability of PF-5274857 was also confirmed and quantified in nontumor-bearing preclinical species with an intact blood-brain barrier. PF-5274857 was orally available and metabolically stable in vivo. These findings suggest that PF-5274857 is a potentially attractive clinical candidate for the treatment of tumor types including brain tumors and brain metastasis driven by an activated Hh pathway.
Asunto(s)
2,2'-Dipiridil/análogos & derivados , Proteínas Hedgehog/antagonistas & inhibidores , Proteínas Hedgehog/metabolismo , Meduloblastoma/tratamiento farmacológico , Piperazinas/farmacología , Receptores Acoplados a Proteínas G/antagonistas & inhibidores , 2,2'-Dipiridil/farmacología , Animales , Antineoplásicos , Barrera Hematoencefálica/efectos de los fármacos , Barrera Hematoencefálica/metabolismo , Línea Celular Tumoral , Células HEK293 , Humanos , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Meduloblastoma/patología , Ratones , Ratones SCID , Ratones Transgénicos , Receptores Patched , Ratas , Ratas Wistar , Receptores de Superficie Celular/genética , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal/efectos de los fármacos , Receptor Smoothened , Proteína con Dedos de Zinc GLI1RESUMEN
Proper characterization of animal models used for efficacy and safety assessment is crucial. The present study focuses on characterizing proteins that are important components of the absorption, distribution, metabolism, and elimination of xenobiotics. Hepatic gene expression of Cyp2b10, Cyp2c29, Cyp3a11, Cyp2e1, Cyp4a10, Nr1i2, Nr1i3, slco1a1, slco1a4, slco1b2, abcb1b, abcc2, and abcg2 was examined using the real-time polymerase chain reaction method in male db/db mice, a commonly used type II diabetes model. We evaluated age and disease effects on gene expression and enzymatic activity in 10- and 25-week-old db/db and 25-week-old C57BLKS/J (strain-matched lean control) mice. Functional analysis was conducted in hepatic microsomes for Cyp2b, Cyp2c, and Cyp3a using cytochrome P450-specific substrates. There were no significant age- or disease-dependent changes in the expression of Cyp3a11 and Cyp3a activity in the db/db mice. The mRNA levels and the activities of Cyp2b10 and Cyp2c29 in the 25-week-old db/db mice decreased significantly compared with those of the 10-week-old db/db mice. There was a significant age-dependent increase in Cyp4a10 expression noted. The most marked expression change in db/db mice versus a control was the â¼400-fold reduction of mRNA expression of slco1a1. Slco1a4 and sloc1b2 showed increased expression compared with that in an age-matched control, whereas abcb1b showed decreased expression. No expression changes were observed for Cyp2e1, Nr1i2, Nr1i3, abcc2, and abcg2. Our data demonstrate that significant expression and activity differences exist between the db/db and the lean control mice, which are probably age- and disease-dependent.
Asunto(s)
Sistema Enzimático del Citocromo P-450/genética , Diabetes Mellitus Tipo 2/metabolismo , Hígado/metabolismo , Proteínas de Transporte de Membrana/genética , Receptores Citoplasmáticos y Nucleares/genética , Factores de Edad , Animales , Glucemia/análisis , Peso Corporal , Receptor de Androstano Constitutivo , Sistema Enzimático del Citocromo P-450/análisis , Sistema Enzimático del Citocromo P-450/fisiología , Insulina/sangre , Masculino , Proteínas de Transporte de Membrana/análisis , Ratones , Ratones Endogámicos C57BL , ARN Mensajero/análisis , Receptores Citoplasmáticos y Nucleares/análisisRESUMEN
Because rifampin (RIF) induces hepatic enzymes and inhibits uptake transporters, dosing a drug that is a dual substrate of enzymes and uptake transporters on the final day of an inducing regimen should exhibit less inductive effect than dosing on the following day in the absence of RIF, since RIF decreases drug uptake into liver. In vitro and in vivo rat studies were conducted using digoxin as a model substrate. Digoxin was administered to an uninduced control group to obtain baseline values. The second group (induced with dexamethasone) received digoxin alone, mimicking administration of a test drug 1 day following completion of an induction regimen, whereas the third group (induced) received digoxin with RIF mimicking the concomitant dosing on the final day of an induction regimen. Results from hepatocyte concentration-time course studies showed that compared with uninduced control (26.9 +/- 1.3 microM . min/mg), digoxin area under the time-concentration curve (AUC) in induced cells when no RIF is present decreased significantly (13.7 +/- 0.9 microM . min/mg; p < 0.01), suggesting induction of Cyp3a. However, digoxin AUC for induced cells in the presence of RIF (27.3 +/- 0.9 microM . min/mg) matched the control. Rat pharmacokinetic studies showed that compared with digoxin clearance in uninduced controls (7.08 +/- 1.57 ml/min/kg), digoxin clearance in induced rats increased 2-fold (15.6 +/- 3.7 ml/min/kg; p < 0.001), but when RIF was coadministered in the induced rats, digoxin clearance (7.14 +/- 1.24 ml/min/kg) overlapped with control. That is, concomitant dosing of RIF and digoxin masked the inductive effect. To observe full inductive effects, test drugs should be administered 1 day after final dosing of RIF to minimize potential organic anion transporting polypeptide inhibition effects.
Asunto(s)
Hígado/metabolismo , Rifampin/farmacología , Animales , Área Bajo la Curva , Digoxina/farmacocinética , Hepatocitos/metabolismo , Masculino , Proteína 1 de Transporte de Anión Orgánico/fisiología , Ratas , Ratas WistarRESUMEN
The effects of hepatic uptake and efflux transporters on erythromycin (ERY) disposition and metabolism were examined by comparing results from rat hepatic microsomes, freshly isolated hepatocytes, and in vivo studies. Uptake studies carried out in freshly isolated rat hepatocytes showed that ERY and its metabolite (N-demethyl-ERY) are substrates of Oatp1a4 and Oatp1b2. Whereas rifampin and GG918 [GF120918: N-{4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)-ethyl]-phenyl}-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamine] exerted minimal effects on metabolism in microsomes, rifampin (2.5 microM) and GG918 (0.5 microM) significantly decreased and increased ERY metabolism in hepatocytes, respectively. Concentration-time course studies further demonstrated that, compared with the intracellular N-demethyl-ERY control area under the curve (AUC) (0.795 +/- 0.057 microM . min), a decreased AUC (0.513 +/- 0.028 microM . min, p < 0.005) was observed when ERY was coincubated with rifampin, and an increased AUC (2.14 +/- 0.21 microM . min, p < 0.05) was found when GG918 was present. The results of the i.v. bolus studies showed that, compared with the ERY clearance of the controls (47.2 +/- 12.5 ml/min/kg for the rifampin group and 42.1 +/- 5.7 for the GG918 group), a decreased blood clearance, 29.8 +/- 6.1 ml/min/kg (p < 0.05) and 21.7 +/- 9.0 ml/min/kg (p < 0.01), was observed when rifampin or GG918, respectively, was coadministered. When either inhibitor was codosed with ERY, volume of distribution at steady state was unchanged, but t1/2 and mean residence time significantly increased compared with the controls. Hepatic uptake and efflux transporters modulate intracellular concentrations of ERY, thereby affecting metabolism. The interplay of transporters and enzymes must be considered in evaluating potential drug-drug interactions.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Eritromicina/metabolismo , Eritromicina/farmacocinética , Hepatocitos/efectos de los fármacos , Transportadores de Anión Orgánico/antagonistas & inhibidores , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Acridinas/farmacología , Animales , Antibacterianos/metabolismo , Antibacterianos/farmacocinética , Células Cultivadas , Hepatocitos/metabolismo , Técnicas In Vitro , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Transportadores de Anión Orgánico/metabolismo , Ratas , Ratas Wistar , Rifampin/farmacología , Tetrahidroisoquinolinas/farmacologíaRESUMEN
The effects of hepatic uptake and efflux transporters on metabolism of digoxin were examined in isolated rat hepatocytes versus microsomes. The metabolic clearance estimated from microsomes was 4.59 +/- 0.69 ml/min/kg. However, the metabolic clearance estimated from hepatocytes was 15.9 +/- 3.0 ml/min/kg. The former did not correlate with in vivo clearance (12.9 ml/min/kg) for digoxin. Rifampin (an organic anion-transporting peptide 2 inhibitor) or GG918 [GF120918 (N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide)] (a potent P-glycoprotein inhibitor) were used to estimate effects of uptake or efflux transporters on digoxin metabolism. Whereas both inhibitors exerted minimal effects on metabolism in microsomes, rifampin and GG918 significantly decreased and increased digoxin metabolism in hepatocytes, respectively. Concentration-time course studies further demonstrated that, compared with the area under the curve (AUC) of control (15.6 +/- 0.1 microM . min), an increase of AUC (20.1 +/- 0.5 microM . min, p < 0.005) was observed when digoxin was coincubated with rifampin and a decrease of AUC (14.1 +/- 0.1 microM . min, p < 0.01) when GG918 was also present. Digoxin primary metabolite concentrations changed directionally in an inverse manner with parent drug concentrations, as would be expected. These results strongly suggest that the hepatic uptake and efflux transporters that are found in hepatocytes, but not in microsomes, modulate intracellular concentration of digoxin and thus affect metabolism. We conclude that the interplay of transporters and enzymes must be considered in defining the intrinsic metabolic clearance of the liver and in evaluating potential drug-drug interactions.