RESUMEN
Selective delta opioid receptor agonists are promising potential therapeutic agents for the treatment of various types of pain conditions. A spirocyclic derivative was identified as a promising hit through screening. Subsequent lead optimization identified compound 20 (ADL5859) as a potent, selective, and orally bioavailable delta agonist. Compound 20 was selected as a clinical candidate for the treatment of pain.
Asunto(s)
Analgésicos/administración & dosificación , Benzamidas/administración & dosificación , Benzopiranos/administración & dosificación , Dolor/tratamiento farmacológico , Receptores Opioides delta/agonistas , Administración Oral , Analgésicos/síntesis química , Analgésicos/química , Animales , Benzamidas/síntesis química , Benzamidas/química , Benzopiranos/síntesis química , Benzopiranos/química , Disponibilidad Biológica , Perros , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos , Canales de Potasio Éter-A-Go-Go/efectos de los fármacos , Humanos , Dosis Máxima Tolerada , Ratones , Estructura Molecular , Actividad Motora/efectos de los fármacos , Dimensión del Dolor/efectos de los fármacos , Ratas , Pruebas de ToxicidadRESUMEN
Novel ((2-substituted-1H-benzo[d]imidazol-1-yl)methyl)benzamides were found to be excellent P1' substituents in conjunction with unique constrained beta-amino hydroxamic acid scaffolds for the discovery of potent selective inhibitors of TNF-alpha Converting Enzyme (TACE). Optimized examples proved potent for TACE, exceptionally selective over a wide panel of MMP and ADAM proteases, potent in the suppression of LPS-induced TNF-alpha in human whole blood and orally bioavailable.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Benzamidas/química , Benzamidas/farmacología , Proteína ADAM17 , Animales , Área Bajo la Curva , Benzamidas/sangre , Benzamidas/farmacocinética , Disponibilidad Biológica , Perros , Semivida , Estructura Molecular , Ratas , Relación Estructura-ActividadRESUMEN
Potent and selective inhibitors of tumor necrosis factor-alpha converting enzyme (TACE) were discovered with several new heterocyclic P1' groups in conjunction with cyclic beta-amino hydroxamic acid scaffolds. Among them, the pyrazolopyridine provided the best overall profile when combined with tetrahydropyran beta-amino hydroxamic acid scaffold. Specifically, inhibitor 49 showed IC(50) value of 1 nM against porcine TACE and 170 nM in the suppression of LPS-induced TNF-alpha of human whole blood. Compound 49 also displayed excellent selectivity over a wide panel of MMPs as well as excellent oral bioavailability (F%>90%) in rat n-in-1 PK studies.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Benzofuranos/química , Imidazoles/química , Indoles/química , Inhibidores de Proteasas/farmacología , Pirazoles/química , Piridinas/química , Proteínas ADAM/metabolismo , Proteína ADAM17 , Administración Oral , Animales , Disponibilidad Biológica , Humanos , Ácidos Hidroxámicos/química , Lipopolisacáridos/farmacología , Inhibidores de la Metaloproteinasa de la Matriz , Estructura Molecular , Inhibidores de Proteasas/síntesis química , Inhibidores de Proteasas/farmacocinética , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
Two novel oxaspiro[4.4]nonane beta-benzamido hydroxamic scaffolds have been synthesized in enantio- and diasteriomerically pure form. These templates proved to be exceptional platforms that have led to the discovery of potent inhibitors of TACE that are active in a cellular assay measuring suppression of LPS-induced TNF-alpha. Furthermore, these inhibitors are selective against related MMPs, demonstrate permeability in a Caco-2 assay, and display good oral bioavailability.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Alcanos/química , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Inhibidores de Proteasas/química , Inhibidores de Proteasas/farmacología , Compuestos de Espiro/química , Proteína ADAM17 , Administración Oral , Alcanos/síntesis química , Alcanos/farmacocinética , Alcanos/farmacología , Animales , Disponibilidad Biológica , Células CACO-2 , Humanos , Ácidos Hidroxámicos/síntesis química , Ácidos Hidroxámicos/farmacocinética , Inhibidores de la Metaloproteinasa de la Matriz , Metaloproteinasas de la Matriz/metabolismo , Modelos Moleculares , Inhibidores de Proteasas/síntesis química , Inhibidores de Proteasas/farmacocinética , Ratas , Ratas Sprague-Dawley , Compuestos de Espiro/síntesis química , Compuestos de Espiro/farmacocinética , Compuestos de Espiro/farmacologíaRESUMEN
Beta-benzamido hydroxamic acids were discovered as potent TACE inhibitors. A computer model was constructed to help understanding the binding activities and guiding SAR study. SAR optimization led to the discovery of compound 30 which met all in vitro and in vivo criteria for the program and was selected for further evaluation.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Inhibidores de Proteasas/química , Inhibidores de Proteasas/farmacología , Proteínas ADAM/química , Proteínas ADAM/metabolismo , Proteína ADAM17 , Administración Oral , Animales , Benzamidas/química , Benzamidas/farmacocinética , Benzamidas/farmacología , Sitios de Unión , Disponibilidad Biológica , Perros , Ácidos Hidroxámicos/farmacocinética , Modelos Moleculares , Inhibidores de Proteasas/farmacocinética , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , PorcinosRESUMEN
N-in-1 (or cassette) dosing pharmacokinetics (PK) has been used in drug discovery for rapid assessment of PK properties of new chemical entities. However, because of potential for drug-drug interactions this procedure is still controversial. This study was to retrospectively evaluate the N-in-1 dosing approach in drug discovery with an emphasis on the potential for drug-drug interactions. The systemic clearance, volume of distribution, oral bioavailability, and renal excretion of the 31 lead compounds in rats, dogs or chimpanzees were significantly correlated between the N-in-1 dosing and discrete studies with r values of 0.69, 0.91, 0.53, and 0.83 (p < 0.005 for all), respectively. PK parameters for 11 quality control compounds which were involved in 194 N-in-1 studies for screening approximately 1000 compounds had coefficient of variations of less than 70%. The intrinsic microsomal clearances generated from the N-in-1 and discrete incubations were nearly identical (r = 0.97, p < 0.0001). The intrinsic clearances of quality control compound from the N-in-1 incubations were consistent with its discrete CL(int) estimate (cv: 5.4%). Therefore, N-in-1 dosing is a useful approach in drug discovery to quickly obtain initial PK estimates. Potential drug-drug interactions that result in confounding PK estimates do not occur as frequently as expected.
Asunto(s)
Inhibidores del Citocromo P-450 CYP3A , Diseño de Fármacos , Evaluación Preclínica de Medicamentos/métodos , Microsomas Hepáticos , Preparaciones Farmacéuticas/administración & dosificación , Farmacocinética , Animales , Disponibilidad Biológica , Citocromo P-450 CYP3A , Perros , Interacciones Farmacológicas , Humanos , Técnicas In Vitro , Masculino , Tasa de Depuración Metabólica , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/enzimología , Modelos Biológicos , Pan troglodytes , RatasRESUMEN
Selective inhibitors of TNF-alpha Converting Enzyme (TACE) based on (1R,2S)-cyclopentyl, (3S,4S)-pyrrolidinyl, and (3R,4S)-tetrahydrofuranyl beta-benzamido hydroxamic acids have been synthesized and evaluated. This study has led to the discovery of novel inhibitors whose profiles include activity against TACE in an enzyme assay, potency in the suppression of LPS-stimulated TNF-alpha in human whole blood, selectivity against a panel of MMPs and oral bioavailability.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Proteína ADAM17 , Administración Oral , Animales , Disponibilidad Biológica , Cromatografía Líquida de Alta Presión , Inhibidores Enzimáticos/síntesis química , Humanos , Ácidos Hidroxámicos/administración & dosificación , Ácidos Hidroxámicos/síntesis química , Ácidos Hidroxámicos/farmacocinética , Ratas , EstereoisomerismoRESUMEN
DPC 333 ((2R)-2-((3R)-3-amino-3{4-[2-methyl-4-quinolinyl) methoxy] phenyl}-2-oxopyrrolidinyl)-N-hydroxy-4-methylpentanamide)) is a potent and selective inhibitor of tumor necrosis factor (TNF)-alpha-converting enzyme (TACE). It significantly inhibits lipopolysaccharide-induced soluble TNF-alpha production in blood from rodents, chimpanzee, and human, with IC(50) values ranging from 17 to 100 nM. In rodent models of endotoxemia, DPC 333 inhibited the production of TNF-alpha in a dose-dependent manner, with an oral ED(50) ranging from 1.1 to 6.1 mg/kg. Oral dosing of DPC 333 at 5.5 mg/kg daily for 2 weeks in a rat collagen antibody-induced arthritis model suppressed the maximal response by approximately 50%. DPC 333 was distributed widely to tissues including the synovium, the site of action for antiarthritic drugs. Pharmacokinetic and pharmacodynamic studies in chimpanzee revealed a systemic clearance of 0.4 l/h/kg, a V(ss) of 0.6 l/kg, an oral bioavailability of 17%, and an ex vivo IC(50) for the suppression of TNF-alpha production of 55 nM (n = 1). In a phase I clinical trial with male volunteers after single escalating doses of oral DPC 333, the terminal half-life was between 3 and 6 h and the ex vivo IC(50) for suppressing TNF-alpha production was 113 nM. Measurement of the suppression of TNF-alpha production ex vivo may serve as a good biomarker in evaluating the therapeutic efficacy of TACE inhibitors. Overall, the pharmacological profiles of DPC 333 support the notion that suppression of TNF-alpha with TACE inhibitors like DPC 333 may provide a novel approach in the treatment of various inflammatory diseases including rheumatoid arthritis, via control of excessive TNF-alpha production.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Antiinflamatorios/farmacocinética , Antiinflamatorios/uso terapéutico , Artritis Experimental/tratamiento farmacológico , Endotoxemia/tratamiento farmacológico , Quinolinas/farmacocinética , Quinolinas/uso terapéutico , Proteína ADAM17 , Adulto , Animales , Antiinflamatorios/sangre , Artritis Experimental/sangre , Artritis Experimental/patología , Perros , Método Doble Ciego , Endotoxemia/sangre , Endotoxemia/inducido químicamente , Femenino , Humanos , Lipopolisacáridos , Masculino , Ratones , Ratones Endogámicos BALB C , Pan troglodytes , Quinolinas/sangre , Ratas , Ratas Endogámicas , Líquido Sinovial/química , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores , Factor de Necrosis Tumoral alfa/sangreRESUMEN
DPC168, a benzylpiperidine-substituted aryl urea CCR3 antagonist evaluated in clinical trials, was a relatively potent inhibitor of the 2D6 isoform of cytochrome P-450 (CYP2D6). Replacement of the cyclohexyl central ring with saturated heterocycles provided potent CCR3 antagonists with improved selectivity against CYP2D6. The favorable preclinical profile of DPC168 was maintained in an acetylpiperidine derivative, BMS-570520.
Asunto(s)
Compuestos de Bencilo/química , Compuestos de Bencilo/farmacología , Inhibidores del Citocromo P-450 CYP2D6 , Compuestos de Fenilurea/química , Piperidinas/química , Piperidinas/farmacología , Receptores de Quimiocina/antagonistas & inhibidores , Animales , Compuestos de Bencilo/síntesis química , Bioensayo , Células Cultivadas , Humanos , Ratones , Pan troglodytes , Compuestos de Fenilurea/farmacología , Piperidinas/síntesis química , Receptores CCR3 , Relación Estructura-ActividadRESUMEN
A new P1' group for TACE inhibitors was identified by eliminating the oxygen atom in the linker of the original 4-(2-methylquinolin-4-ylmethoxy)phenyl P1' group. Incorporation of this 4-(2-methylquinolin-4-ylmethyl)phenyl group onto different beta-aminohydroxamic acid cores provided compound 18, which demonstrated potent porcine TACE (p-TACE) and human whole blood activity, excellent PK properties, and good selectivity against a variety of MMPs.
Asunto(s)
Proteínas ADAM/antagonistas & inhibidores , Química Farmacéutica/métodos , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/síntesis química , Ácidos Hidroxámicos/química , Proteínas ADAM/sangre , Proteína ADAM17 , Animales , Perros , Diseño de Fármacos , Inhibidores Enzimáticos/farmacología , Humanos , Concentración 50 Inhibidora , Modelos Químicos , Conformación Molecular , Oxígeno/química , Ratas , Relación Estructura-Actividad , PorcinosRESUMEN
The chimpanzee (CHP) was evaluated as a pharmacokinetic model for humans (HUMs) using propranolol, verapamil, theophylline, and 12 proprietary compounds. Species differences were observed in the systemic clearance of theophylline (approximately 5-fold higher in CHPs), a low clearance compound, and the bioavailability of propranolol and verapamil (lower in CHPs), both high clearance compounds. The systemic clearance of propranolol (approximately 1.53 l/h/kg) suggested that the hepatic blood flow in CHPs is comparable to that in humans. No substantial differences were observed in the in vitro protein binding. A preliminary attempt was made to characterize cytochrome P450 (P450) activities in CHP and HUM liver microsomes. Testosterone 6beta-hydroxylation and tolbutamide methylhydroxylation activities were comparable in CHP and HUM liver microsomes. In contrast, dextromethorphan O-demethylation and phenacetin O-deethylation activities were approximately 10-fold higher (per mg protein) in CHP liver microsomes. Intrinsic clearance estimates in CHP liver microsomes were higher for propranolol (approximately 10-fold) and theophylline (approximately 5-fold) and similar for verapamil. Of the 12 proprietary compounds, 3 had oral clearances that differed in the two species by more than 3-fold, an acceptable range for biological variability. Most of the observed differences are consistent with species differences in P450 enzyme activity. Oral clearances of proprietary compounds in HUMs were significantly correlated to those from CHPs (r = 0.68; p = 0.015), but not to estimates from rat, dog, and monkey. In summary, the chimpanzee serves as a valuable surrogate model for human pharmacokinetics, especially when species differences in P450 enzyme activity are considered.
Asunto(s)
Pan troglodytes/fisiología , Preparaciones Farmacéuticas/metabolismo , Farmacocinética , Acetaminofén/farmacocinética , Antagonistas Adrenérgicos beta/farmacocinética , Analgésicos no Narcóticos/farmacocinética , Animales , Western Blotting , Broncodilatadores/farmacocinética , Bloqueadores de los Canales de Calcio/farmacocinética , Cromatografía Líquida de Alta Presión , Humanos , Técnicas In Vitro , Masculino , Espectrometría de Masas , Microsomas Hepáticos/metabolismo , Modelos Biológicos , Propranolol/farmacocinética , Unión Proteica , Ratas , Ratas Sprague-Dawley , Especificidad de la Especie , Espectrometría de Fluorescencia , Espectrofotometría Ultravioleta , Teofilina/farmacocinética , Verapamilo/farmacocinéticaRESUMEN
In this communication we describe the design, synthesis, and evaluation of novel sultam hydroxamates 4 as MMP-2, -9, and -13 inhibitors. Compound 26 was found to be an active inhibitor (MMP-2 IC(50) = 1 nM) with 1000-fold selectivity over MMP-1 and good oral bioavailability (F = 43%) in mouse. An X-ray crystal structure of 26 in MMP-13 confirms the key hydrogen bonds and prime side binding in the active site.
Asunto(s)
Ácidos Hidroxámicos/síntesis química , Inhibidores de la Metaloproteinasa de la Matriz , Sulfonamidas/síntesis química , Administración Oral , Animales , Disponibilidad Biológica , Cristalografía por Rayos X , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Metaloproteinasa 13 de la Matriz , Ratones , Modelos Moleculares , Relación Estructura-Actividad , Sulfonamidas/química , Sulfonamidas/farmacologíaRESUMEN
Modifications of the lead TACE inhibitor 1 (N-hydroxy-trans-2-[[4-(4-quinolinyloxymethyl)anilinyl]carbonyl]-1-cyclohexanecarboxamide) at the cyclohexyl ring and the quinoline moiety led to the identification of a series of piperidine containing TACE inhibitors with potent activity in the inhibition of TNF-alpha release in the whole blood assay (WBA). The most potent analogue IM491 [N-hydroxy-(5S,6S)-1-methyl-6-[[4-(2-methyl-4-quinolinylmethoxy)anilinyl]carbonyl]-5-piperidinecarboxamide] exhibited an IC(50) value of 20 nM in WBA with excellent selectivity over MMP-1, -2 and -9 and is orally bioavailable with an F value of 43% in beagle dogs.
Asunto(s)
Inhibidores Enzimáticos/síntesis química , Metaloendopeptidasas/antagonistas & inhibidores , Succinatos/síntesis química , Proteínas ADAM , Proteína ADAM17 , Diseño de Fármacos , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Cinética , Modelos Moleculares , Conformación Molecular , Relación Estructura-Actividad , Succinatos/química , Succinatos/farmacologíaRESUMEN
PURPOSE: The purpose of this study was to develop and validate an animal model of drug disposition in synovial fluid (SF) by comparing microdialysis with arthrocentesis using the anti-arthritic drug methotrexate (MTX). METHODS: Microdialysis probes were calibrated in vitro with the no net flux method using dog synovial fluid. The probes were implanted surgically into the stifle joint space of four dogs and were dialyzed overnight using a portable microinfusion pump. The membrane integrity of the probes was monitored by retrodialysis using an internal standard. After an intravenous bolus of 2.5 mg/kg of MTX, unbound concentrations in synovial fluid, as well as total plasma concentrations, were measured by liquid chromatography tandam mass spectrometer (LC/MS/MS) in samples collected from 0 to 48 h postdose. RESULTS: The probe membrane remained intact at least 48 h after implantation. The mean probe recovery and unbound fraction of MTX in SF were 46.8% and 44.8%, respectively. The unbound fraction of MTX was 44% in synovial fluid. MTX penetrated into the joint space rapidly, with maximal concentrations of 6.6 microM reached at approximately 1 h postdose. The unbound MTX area under the curve in SF was approximately 40% of the total area under the curve in plasma. These data agree well with the previous data obtained for MTX using arthrocentesis. CONCLUSION: In contrast with arthrocentesis, microdialysis enables the collection of multiple serial SF samples from individual animals with minimal trauma and potential blood contamination. This animal model should prove valuable for studying the disposition of new antiarthritis compounds or biomarkers in SF.
Asunto(s)
Antirreumáticos/farmacocinética , Metotrexato/farmacocinética , Microdiálisis , Modelos Animales , Líquido Sinovial/efectos de los fármacos , Líquido Sinovial/metabolismo , Animales , Perros , Estudios de Factibilidad , Cromatografía de Gases y Espectrometría de Masas , Masculino , Metotrexato/química , Paracentesis , Líquido Sinovial/químicaRESUMEN
Elevated levels of tumor necrosis factor-alpha (TNF-alpha) have been associated with several inflammatory diseases, and therefore, strategies for its suppression have become important targets in drug discovery. Our efforts to suppress TNF-alpha have centered on the inhibition of TNF-alpha converting enzyme (TACE) through the use of hydroxamate inhibitors. Starting from broad-spectrum matrix metalloproteinase (MMP) inhibitors, we have designed and synthesized novel benzothiadiazepines as potent and selective TACE inhibitors. The benzothiadiazepines were synthesized with variation in P1 and P1' in order to effect potency and selectivity. The inhibitors were evaluated versus porcine TACE (pTACE), and the initial selectivity was assessed with counterscreens of MMP-1, -2, and -9. Several potent and selective inhibitors were discovered with compound 41 being the most active against pTACE (K(i) = 5 nM) while still maintaining good selectivity versus the MMP's (at least 75-fold). Most compounds were assessed in the human peripheral blood mononuclear cell assay (PBMC) and the human whole blood assay (WBA) to determine their ability to suppress TNF-alpha. Compound 32 was the most potent compound in the PBMC assay (IC(50) = 0.35 microM), while compound 62 was the most active in the WBA (IC(50) = 1.4 microM).
Asunto(s)
Benzodiazepinonas/síntesis química , Inhibidores Enzimáticos/síntesis química , Ácidos Hidroxámicos/síntesis química , Metaloendopeptidasas/antagonistas & inhibidores , Tiazepinas/síntesis química , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores , Proteínas ADAM , Proteína ADAM17 , Animales , Benzodiazepinonas/química , Benzodiazepinonas/farmacología , Proteínas Sanguíneas/metabolismo , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Humanos , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Leucocitos Mononucleares/efectos de los fármacos , Inhibidores de la Metaloproteinasa de la Matriz , Modelos Moleculares , Unión Proteica , Relación Estructura-Actividad , Porcinos , Tiazepinas/química , Tiazepinas/farmacología , Factor de Necrosis Tumoral alfa/biosíntesisRESUMEN
Anti-succinate hydroxamates with cyclic P1 motifs were synthesized as aggrecanase inhibitors. The N-methanesulfonyl piperidine 23 and the N-trifluoroacetyl azetidine 26 were the most potent aggrecanase inhibitors both having an IC(50)=3nM while maintaining >100-fold selectivity over MMP-1, -2, and -9. The cyclic moieties were also capable of altering in vivo metabolism, hence delivering low clearance compounds in both rat and dog studies as shown for compound 14.
Asunto(s)
Endopeptidasas/metabolismo , Ácidos Hidroxámicos/síntesis química , Ácidos Hidroxámicos/farmacología , Inhibidores de Proteasas/síntesis química , Inhibidores de Proteasas/farmacología , Animales , Bovinos , Perros , Semivida , Ácidos Hidroxámicos/farmacocinética , Indicadores y Reactivos , Isoenzimas/antagonistas & inhibidores , Inhibidores de Proteasas/farmacocinética , RatasRESUMEN
New gamma-lactam TACE inhibitors were designed from known MMP inhibitors. A homology model of TACE was built and examined to identify the S1' site as the key area for TACE selectivity over MMPs. Rational exploration of the P1'-S1' interactions resulted in the discovery of the 3,5-disubstituted benzyl ether as a TACE-selective P1' group. Further optimization led to the discovery of IK682 as a selective and orally bioavailable TACE inhibitor.
Asunto(s)
Ácidos Hidroxámicos/síntesis química , Lactamas/síntesis química , Metaloendopeptidasas/antagonistas & inhibidores , Inhibidores de Proteasas/síntesis química , Proteínas ADAM , Proteína ADAM17 , Administración Oral , Animales , Disponibilidad Biológica , Perros , Ácidos Hidroxámicos/química , Ácidos Hidroxámicos/farmacología , Lactamas/química , Lactamas/farmacología , Metaloproteinasa 3 de la Matriz/química , Modelos Moleculares , Inhibidores de Proteasas/química , Inhibidores de Proteasas/farmacología , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , PorcinosRESUMEN
N-[(3-fluorophenyl)methyl]glycyl-N-[3-[((3-aminophenyl)sulfonyl)- 2-(aminophenyl)amino]-(1S,2S)-2-hydroxy-1-(phenylmethyl)propyl]- 3-methyl-L-valinamide (DPC 681, DPC(1)) on oral coadministration with ritonavir (RTV) in rats caused a significant increase in systemic exposure to DPC. Following a single oral dose of [(14)C]DPC with and without RTV pretreatment in rats, and subsequent analysis of whole-body sections, prepared at 1 and 7 or 8 h postdose, using whole-body autoradiography showed an increase in radioactivity in tissues (e.g., brain, and testes) upon coadministration. The distribution of radioactivity in the brain parenchyma and ventricles was different, such that the concentration of radioactivity was greater in cerebrospinal fluid (CSF) than in central nervous system. Thus, the use of CSF concentration of the total radioactivity as a surrogate for brain penetration would result in an overestimation. DPC was determined to be metabolized prominently by rCYP3A4. The increased tissue exposure to DPC in rats could largely be attributed to inhibition of CYP3A1/2 by RTV. DPC was also a good substrate for P-glycoprotein (Pgp), with K(m) of 4 microM and V(max) of 13 pmol/min. The Pgp-mediated transport of DPC across Caco-2 cells was readily saturated at >or=10 microM and was inhibited significantly by RTV at 5 to 10 microM. The data above and the reported RTV concentrations suggested that both the Pgp and CYP3A4 inhibition by RTV may play a significant role in enhancing the systemic and tissue exposure to DPC in humans.