RESUMO
Patients with psoriasis often take multiple medications due to comorbidities, raising concerns about drug-drug interactions (DDIs) during the development of new medicines. DDI risk assessments of a new small molecule showed risks of CYP3A4 autoinduction and being a sensitive CYP3A4 substrate. We conducted a real-world evidence (RWE) claims analysis to assess the frequency of prescription claims for up to 12 months from the date of the initial psoriasis diagnosis for drugs that may interact with CYP3A4 substrates. We used 2013 to 2018 patient data from the US Merative MarketScan Research Database. Among patients diagnosed with psoriasis, less than 1% had a claim for a moderate/strong inducer, but up to 15% had a claim for moderate/strong inhibitor. Most prescriptions for CYP3A4 inhibitors or inducers included antibiotics and anticonvulsants. While CYP3A4 inducers were rarely used, those treated received more than >90 days treatment. Then, these RWE data were used to inform the early translational medicine strategy for the new investigational drug by strategically integrating DDI evaluations into a first-in-human healthy volunteer trial prior to studies in patients with psoriasis. The resulting DDI substudy showed that the investigational small molecule did not induce midazolam clearance but was sensitive to CYP3A inhibition, leading to the decision to exclude concomitant use of strong CYP3A4 inducers or inhibitors from clinical trials.
RESUMO
Carbamazepine (CBZ) is the recommended alternative to rifampicin as a CYP3A4 inducer in drug-drug interaction studies. However, the traditional CBZ dosing paradigm can lead to several adverse events (AEs). This study tested a shorter CBZ dosing regimen using the CYP3A4-sensitive index substrate midazolam (MDZ). This was a fixed-sequence arm of an open-label, phase I study (NCT04840888). Healthy participants (n = 15) aged 18-63 years received oral doses of 1.2 mg MDZ alone (Day 1), CBZ b.i.d. alone (100 mg Days 2-4; 200 mg Days 5-7; 300 mg Days 8-10 and 12-13), and 300 mg CBZ b.i.d. plus 1.2 mg MDZ (Days 11 and 14). One participant (6.7%) experienced constipation due to treatment with CBZ plus MDZ on Day 11. One participant (6.7%) experienced urticaria (Days 12-13), and two participants (13.3%) experienced somnolence (Days 8-10) due to treatment with 300 mg CBZ b.i.d. alone. All AEs were mild. For MDZ, the geometric mean (90% CI) ratio (vs. Day 1) of the area under the curve (AUC 0-∞) was 0.28 (0.24-0.31) on Day 11 and 0.26 (0.23-0.29) on Day 14. The AUC (0-12 hours) of CBZ was 114,000 ngâh/mL on Day 11 and 105,000 ngâh/mL on Day 14. Steady-state concentrations of CBZ and induction of CYP3A4 were achieved on Day 11. The data are consistent with predictions of physiologically-based pharmacokinetic models in Simcyp. The 9-day dosing regimen for CBZ induction was well-tolerated by healthy participants, supporting the use of a shorter CBZ regimen for CYP3A4 induction studies.
RESUMO
Three structurally closely related dopamine D1 receptor positive allosteric modulators (D1 PAMs) based on a tetrahydroisoquinoline (THIQ) scaffold were profiled for their CYP3A4 induction potentials. It was found that the length of the linker at the C5 position greatly affected the potentials of these D1 PAMs as CYP3A4 inducers, and the level of induction correlated well with the activation of the pregnane X receptor (PXR). Based on the published PXR X-ray crystal structures, we built a binding model specifically for these THIQ-scaffold-based D1 PAMs in the PXR ligand-binding pocket via an ensemble docking approach and found the model could explain the observed CYP induction disparity. Combined with our previously reported D1 receptor homology model, which identified the C5 position as pointing toward the solvent-exposed space, our PXR-binding model coincidentally suggested that structural modifications at the C5 position could productively modulate the CYP induction potential while maintaining the D1 PAM potency of these THIQ-based PAMs.
Assuntos
Citocromo P-450 CYP3A , Receptores de Esteroides , Receptor de Pregnano X/metabolismo , Citocromo P-450 CYP3A/metabolismo , Receptores de Esteroides/química , Receptores de Esteroides/genética , Receptores de Esteroides/metabolismo , Indução EnzimáticaRESUMO
Tadalafil, a phosphodiesterase 5 inhibitor, is being investigated as a treatment for pulmonary arterial hypertension (PAH) in children aged 6 months to less than 18 years. Tadalafil pharmacokinetic (PK) data in children less than 2 years old are unavailable, therefore a physiologically based pharmacokinetic (PBPK) model was developed to enable estimation of tadalafil doses in children less than 2 years old. The model was verified in adults and extended for use in children by modifying CYP3A-mediated intrinsic clearance to include CYP3A7. To account for co-dosing of the commonly prescribed moderate CYP3A4 inducer bosentan, predicted exposures were increased by a factor of 1.54 based on changes in exposure in adults with PAH. This factor was predictable using a bosentan PBPK model. The tadalafil model was verified in children aged greater than or equal to 2 years by comparing predicted and observed exposures. Tadalafil doses for children less than 2 years old were calculated as target area under the concentration curve from zero to 24 h (AUC0-24 )/predicted AUC0-24 , with target AUC0-24 of 10,000 ng*h/ml based on adult 40 mg single dose exposures determined in patients without bosentan background treatment. These doses were 2 mg, 3 mg, 4 mg, and 6 mg, respectively, for children aged birth to less than 1 month, 1 month to less than 6 months, 6 months to less than 1 year, and 1 to less than 2 years. Due to uncertainties in CYP maturation, a nonmechanistic steady-state volume scalar, and lack of PK data in children less than 2 years old, accumulation of tadalafil to steady-state in children less than 2 years was not verifiable. Safety of proposed doses is supported by postmarketing research and investigator-led trials.
Assuntos
Hipertensão Arterial Pulmonar , Adulto , Bosentana , Criança , Pré-Escolar , Indutores do Citocromo P-450 CYP3A , Humanos , Lactente , Inibidores da Fosfodiesterase 5/farmacocinética , Inibidores da Fosfodiesterase 5/uso terapêutico , Hipertensão Arterial Pulmonar/tratamento farmacológico , Tadalafila/farmacocinéticaRESUMO
The International Consortium for Innovation and Quality (IQ) Physiologically Based Pharmacokinetic (PBPK) Modeling Induction Working Group (IWG) conducted a survey across participating companies around general strategies for PBPK modeling of induction, including experience with its utility to address various questions, regulatory interactions, and regulatory acceptance. The results highlight areas where PBPK modeling is used with high confidence and identifies opportunities where confidence is lower and further evaluation is needed. To enhance the survey results, the PBPK-IWG also collected case studies and analyzed recent literature examples where PBPK models were applied to predict CYP3A induction-mediated drug-drug interactions. PBPK modeling of induction has evolved and progressed significantly, proving to have great potential to accelerate drug discovery and development. With the aim of enabling optimal use for new molecular entities that are either substrates and/or inducers of CYP3A, the PBPK-IWG proposes initial workflows for PBPK application, discusses future trends, and identifies gaps that need to be addressed.
Assuntos
Citocromo P-450 CYP3A , Modelos Biológicos , Simulação por Computador , Sistema Enzimático do Citocromo P-450 , Interações Medicamentosas , Humanos , Fluxo de TrabalhoRESUMO
Abemaciclib is an orally administered, potent inhibitor of cyclin-dependent kinases 4 and 6 and is metabolized extensively by CYP3A4. The effects of abemaciclib on several CYPs were qualified in vitro and subsequently evaluated in a clinical study. In vitro, human hepatocytes were treated with vehicle, abemaciclib, or abemaciclib metabolites [N-desethylabemaciclib (M2) or hydroxyabemaciclib (M20)]. mRNA levels for eight CYPs were measured using reverse-transcription quantitative polymerase chain reaction, and, additionally, catalytic activities for three CYPs were determined. In the clinical study, adult patients with cancer received a drug cocktail containing CYP substrates [midazolam (3A), warfarin (2C9), dextromethorphan (2D6), and caffeine (1A2)] either alone or in combination with abemaciclib. Plasma pharmacokinetics (PK) samples were analyzed for all substrates, caffeine metabolite paraxanthine, and abemaciclib; polymorphisms of CYP2C9, CYP2D6, CYP3A4, and CYP3A5 were evaluated. In vitro, downregulation of CYP mRNA, including 1A2, 2B6, 2C8, 2C9, 2D6, and 3A, by abemaciclib and/or M2 and M20 was observed at clinically relevant concentrations. In humans, abemaciclib did not affect the PK of CYP2D6 or CYP2C9 substrates. Minor statistically significant but clinically irrelevant changes were observed for midazolam [area under the concentration versus time curve from zero to infinity (AUC0-inf) (13% lower), Cmax (15% lower)], caffeine [AUC0-inf (56% higher)], and paraxanthine: caffeine [area under the concentration versus time curve from 0 to 24 hours ratio (was approximately 30% lower)]. However, given the magnitude of the effect, these changes are not considered clinically relevant. In conclusion, the downregulation of CYP mRNA mediated by abemaciclib in vitro did not translate into clinically meaningful drug-drug interactions in patients with cancer. SIGNIFICANCE STATEMENT: Despite observations that abemaciclib alters the mRNA of various CYP isoforms in vitro, a clinical study using a drug cocktail approach found no clinically meaningful drug-drug interactions between abemaciclib and a range of CYP substrates [midazolam (CYP3A4), S-warfarin (CYP2C9), dextromethorphan (CYP2D6), and caffeine (CYP1A2)]. This lack of translation suggests greater understanding of mechanisms of CYP downregulation is needed to accurately predict clinical drug-drug interaction risk from in vitro data.
Assuntos
Aminopiridinas/farmacocinética , Benzimidazóis/farmacocinética , Neoplasias/tratamento farmacológico , Inibidores de Proteínas Quinases/farmacocinética , Administração Oral , Adulto , Idoso , Aminopiridinas/administração & dosagem , Área Sob a Curva , Benzimidazóis/administração & dosagem , Cafeína/farmacocinética , Células Cultivadas , Citocromo P-450 CYP1A2/metabolismo , Citocromo P-450 CYP2C9/metabolismo , Citocromo P-450 CYP2D6/metabolismo , Citocromo P-450 CYP3A/metabolismo , Dextrometorfano/farmacocinética , Interações Medicamentosas , Feminino , Hepatócitos , Humanos , Masculino , Midazolam/farmacocinética , Pessoa de Meia-Idade , Neoplasias/metabolismo , Cultura Primária de Células , Inibidores de Proteínas Quinases/administração & dosagem , Varfarina/farmacocinéticaRESUMO
The drug-drug interaction profile of atorvastatin confirms that disposition is determined by cytochrome P450 (CYP) 3A4 and organic anion transporting polypeptides (OATPs). Drugs that affect gastric emptying, including dulaglutide, also affect atorvastatin pharmacokinetics (PK). Atorvastatin is a carboxylic acid that exists in equilibrium with a lactone form in vivo. The purpose of this work was to assess gastric acid-mediated lactone equilibration of atorvastatin and incorporate this into a physiologically-based PK (PBPK) model to describe atorvastatin acid, lactone, and their major metabolites. In vitro acid-to-lactone conversion was assessed in simulated gastric fluid and included in the model. The PBPK model was verified with in vivo data including CYP3A4 and OATP inhibition studies. Altering the gastric acid-lactone equilibrium reproduced the change in atorvastatin PK observed with dulaglutide. The model emphasizes the need to include gastric acid-lactone conversion and all major atorvastatin-related species for the prediction of atorvastatin PK.
Assuntos
Atorvastatina/farmacocinética , Gastroparesia/complicações , Peptídeos Semelhantes ao Glucagon/análogos & derivados , Lactonas/química , Proteínas Recombinantes de Fusão/farmacocinética , Atorvastatina/administração & dosagem , Células Cultivadas , Citocromo P-450 CYP3A , Relação Dose-Resposta a Droga , Interações Medicamentosas , Ácido Gástrico/metabolismo , Peptídeos Semelhantes ao Glucagon/administração & dosagem , Peptídeos Semelhantes ao Glucagon/farmacocinética , Hepatócitos/citologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Fragmentos Fc das Imunoglobulinas/administração & dosagem , Modelos Biológicos , Transportadores de Ânions Orgânicos , Proteínas Recombinantes de Fusão/administração & dosagemRESUMO
1. The disposition and metabolism of galunisertib (LY2157299 monohydrate, a TGF-ßRI Kinase/ALK5 Inhibitor) was characterized following a single oral dose of 150 mg of [14C]-galunisertib (100 µCi) to six healthy human subjects. 2. The galunisertib plasma half-life was 8.6 h, while the 14C half-life was 10.0 h. Galunisertib was abundant in circulation (40.3% of the 14C AUC024 h), with 7 additional metabolites detected in plasma. Two metabolites LSN3199597 (M5, mono-oxidation), and M4 (glucuronide of M3) were the most abundant circulating metabolites (10.7 and 9.0% of the 14C AUC024 h respectively). The pharmacological activity of LSN3199597 was tested and found to be significantly less potent than galunisertib. 3. The dose was recovered in feces (64.5%) and in urine (36.8%). Galunisertib was cleared primarily by metabolism, based on low recovery of parent in excreta (13.0% of dose). Due to the slow in vitro metabolism of galunisertib in suspended hepatocytes, a long term hepatocyte system was used to model the human excretion profile. 4. Expressed cytochromes P450 and hepatocytes indicated clearance was primarily CYP3A4-mediated. Mechanistic static modeling that incorporated small non-CYP-mediated metabolic clearance and renal clearance components predicted an AUC ratio of 4.7 for the effect of itraconazole, a strong CYP3A4 inhibitor, on galunisertib.
Assuntos
Radioisótopos de Carbono , Inibidores do Citocromo P-450 CYP3A , Itraconazol , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Pirazóis , Quinolinas , Receptores de Fatores de Crescimento Transformadores beta/antagonistas & inibidores , Administração Oral , Adulto , Idoso , Inibidores do Citocromo P-450 CYP3A/administração & dosagem , Inibidores do Citocromo P-450 CYP3A/farmacocinética , Fezes , Feminino , Humanos , Itraconazol/administração & dosagem , Itraconazol/farmacocinética , Masculino , Pessoa de Meia-Idade , Pirazóis/administração & dosagem , Pirazóis/farmacocinética , Quinolinas/administração & dosagem , Quinolinas/farmacocinética , Receptor do Fator de Crescimento Transformador beta Tipo I , UrinaRESUMO
Evacetrapib is an investigational cholesteryl ester transfer protein inhibitor (CETPi) for reduction of risk of major adverse cardiovascular events in patients with high-risk vascular disease. Understanding evacetrapib disposition, metabolism, and the potential for drug-drug interactions (DDI) may help guide prescribing recommendations. In vitro, evacetrapib metabolism was investigated with a panel of human recombinant cytochromes P450 (CYP). The disposition, metabolism, and excretion of evacetrapib following a single 100-mg oral dose of (14)C-evacetrapib were determined in healthy subjects, and the pharmacokinetics of evacetrapib were evaluated in the presence of strong CYP3A or CYP2C8 inhibitors. In vitro, CYP3A was responsible for about 90% of evacetrapib's CYP-associated clearance, while CYP2C8 accounted for about 10%. In the clinical disposition study, only evacetrapib and two minor metabolites circulated in plasma. Evacetrapib metabolism was extensive. A mean of 93.1% and 2.30% of the dose was excreted in feces and urine, respectively. In clinical DDI studies, the ratios of geometric least squares means for evacetrapib with/without the CYP3A inhibitor ketoconazole were 2.37 for area under the curve (AUC)(0-∞) and 1.94 for C max. There was no significant difference in evacetrapib AUC(0-τ) or C max with/without the CYP2C8 inhibitor gemfibrozil, with ratios of 0.996 and 1.02, respectively. Although in vitro results indicated that both CYP3A and CYP2C8 metabolized evacetrapib, clinical studies confirmed that evacetrapib is primarily metabolized by CYP3A. However, given the modest increase in evacetrapib exposure and robust clinical safety profile to date, there is a low likelihood of clinically relevant DDI with concomitant use of strong CYP3A or CYP2C8 inhibitors.
RESUMO
AIMS: Evacetrapib is a cholesteryl ester transfer protein (CETP) inhibitor under development for reducing cardiovascular events in patients with high risk vascular disease. CETP inhibitors are likely to be utilized as 'add-on' therapy to statins in patients receiving concomitant medications, so the potential for evacetrapib to cause clinically important drug-drug interactions (DDIs) with cytochromes P450 (CYP) was evaluated. METHODS: The DDI potential of evacetrapib was investigated in vitro, followed by predictions to determine clinical relevance. Potential DDIs with possible clinical implications were then investigated in the clinic. RESULTS: In vitro, evacetrapib inhibited all of the major CYPs, with inhibition constants (K(i)) ranging from 0.57 µM (CYP2C9) to 7.6 µM (CYP2C19). Evacetrapib was a time-dependent inhibitor and inducer of CYP3A. The effects of evacetrapib on CYP3A and CYP2C9 were assessed in a phase 1 study using midazolam and tolbutamide as probe substrates, respectively. After 14 days of daily dosing with evacetrapib (100 or 300 mg), midazolam exposures (AUC) changed by factors (95% CI) of 1.19 (1.06, 1.33) and 1.44 (1.28, 1.62), respectively. Tolbutamide exposures (AUC) changed by factors of 0.85 (0.77, 0.94) and 1.06 (0.95, 1.18), respectively. In a phase 2 study, evacetrapib 100 mg had minimal impact on AUC of co-administered simvastatin vs. simvastatin alone with a ratio of 1.25 (1.03, 1.53) at steady-state, with no differences in reported hepatic or muscular adverse events. CONCLUSIONS: Taken together, the extent of CYP-mediated DDI with the potential clinical dose of evacetrapib is weak and clinically important DDIs are not expected to occur in patients taking concomitant medications.
Assuntos
Anticolesterolemiantes/farmacologia , Benzodiazepinas/farmacologia , Proteínas de Transferência de Ésteres de Colesterol/antagonistas & inibidores , Células Cultivadas , Inibidores do Citocromo P-450 CYP3A/farmacologia , Método Duplo-Cego , Interações Medicamentosas , Humanos , Microssomos Hepáticos/enzimologia , Midazolam/farmacocinética , Sinvastatina/farmacocinética , Tolbutamida/farmacocinéticaRESUMO
The glycogen synthase kinase-3 inhibitor LY2090314 specifically impaired CYP2B6 activity during in vitro evaluation of cytochrome P450 (P450) enzyme induction in human hepatocytes. CYP2B6 catalytic activity was significantly decreased following 3-day incubation with 0.1-10 µM LY2090314, on average by 64.3% ± 5.0% at 10 µM. These levels of LY2090314 exposure were not cytotoxic to hepatocytes and did not reduce CYP1A2 and CYP3A activities. LY2090314 was not a time-dependent CYP2B6 inhibitor, did not otherwise inhibit enzyme activity at concentrations ≤10 µM, and was not metabolized by CYP2B6. Thus, mechanism-based inactivation or other direct interaction with the enzyme could not explain the observed reduction in CYP2B6 activity. Instead, LY2090314 significantly reduced CYP2B6 mRNA levels (Imax = 61.9% ± 1.4%; IC50 = 0.049 ± 0.043 µM), which were significantly correlated with catalytic activity (r(2) = 0.87, slope = 0.77; Imax = 57.0% ± 10.8%, IC50 = 0.057 ± 0.027 µM). Direct inhibition of constitutive androstane receptor by LY2090314 is conceptually consistent with the observed CYP2B6 transcriptional suppression (Imax = 100.0% ± 10.8% and 57.1% ± 2.4%; IC50 = 2.5 ± 1.2 and 2.1 ± 0.4 µM for isoforms 1 and 3, respectively) and may be sufficiently extensive to overcome the weak but potent activation of pregnane X receptor by ≤10 µM LY2090314 (19.3% ± 2.2% of maximal rifampin response, apparent EC50 = 1.2 ± 1.1 nM). The clinical relevance of these findings was evaluated through physiologically based pharmacokinetic model simulations. CYP2B6 suppression by LY2090314 is not expected clinically, with a projected <1% decrease in hepatic enzyme activity and <1% decrease in hydroxybupropion exposure following bupropion coadministration. However, simulations showed that observed CYP2B6 suppression could be clinically relevant for a drug with different pharmacokinetic properties from LY2090314.
Assuntos
Citocromo P-450 CYP2B6/biossíntese , Citocromo P-450 CYP2B6/genética , Inibidores do Citocromo P-450 CYP2D6/farmacologia , Drogas em Investigação/farmacologia , Transcrição Gênica/efeitos dos fármacos , Transcrição Gênica/fisiologia , Bupropiona/farmacologia , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Interações Medicamentosas/fisiologia , Drogas em Investigação/química , Feminino , Hepatócitos/efeitos dos fármacos , Hepatócitos/enzimologia , Compostos Heterocíclicos com 3 Anéis/farmacologia , Humanos , Masculino , Maleimidas/farmacologiaRESUMO
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.
Assuntos
Neoplasias/tratamento farmacológico , Compostos de Fenilureia/farmacocinética , Pirazinas/farmacocinética , Administração Intravenosa , Idoso , Cromatografia Líquida , Relação Dose-Resposta a Droga , Interações Medicamentosas , Fezes/química , Feminino , Meia-Vida , Humanos , Masculino , Taxa de Depuração Metabólica , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Pessoa de Meia-Idade , Compostos de Fenilureia/administração & dosagem , Pirazinas/administração & dosagem , Espectrometria de Massas em TandemRESUMO
The disposition and metabolism of isopropyl N-[(2S)-7-cyano-4-(2-pyridylmethyl)-2,3-dihydro-1H-cyclopenta[b]indol-2-yl]carbamate (LY2452473; a selective androgen receptor modulator) in humans was characterized after a single 15-mg (100 µCi) oral dose of [¹4C]LY2452473 to six healthy male subjects. LY2452473 was absorbed rapidly (time to reach maximum plasma concentration for both LY2452473 and total radioactivity was 2-3 h) and cleared slowly (plasma terminal t(½) of 27 h for LY2452473 and 51 h for the total radioactivity). LY2452473 and metabolites S5 (acetylamine) and S12 (hydroxylation on the cyclopentene) were major circulating entities in plasma, accounting for approximately 42, 21, and 35% of the total radioactivity exposure, respectively, as calculated from relative area under the concentration versus time curves from zero to 48 h derived from the plasma radiochromatograms. The radioactive dose was almost completely recovered after 312 h with 47.9% of the dose eliminated in urine and 46.6% in feces. Minimal LY2452473 was detected in excreta, indicating that metabolic clearance was the main route of elimination. Multiple metabolic pathways were observed with no single metabolic pathway accounting for more than 30% of the dose in excreta. Metabolite S10 (a diol across the cyclopenta-indole linkage) was the largest excretory metabolite (approximately 14% of the dose). S10 displayed interesting chemical and chromatographic properties, undergoing conversion to the corresponding epoxide under acidic conditions and conversion back to the diol under neutral conditions. An in vitro phenotyping approach indicated that CYP3A4 was the largest contributor to LY2452473 depletion.
Assuntos
Carbamatos/farmacocinética , Receptores Androgênicos/metabolismo , Adulto , Área Sob a Curva , Citocromo P-450 CYP3A/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
The biotransformation of prasugrel to R-138727 (2-[1-2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl]-4-mercapto-3-piperidinylidene]acetic acid) involves rapid deesterification to R-95913 (2-[2-oxo-6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl]-1-cyclopropyl-2-(2-fluorophenyl)ethanone) followed by cytochrome P450 (P450)-mediated formation of R-138727, the metabolite responsible for platelet aggregation. For identification of the P450s responsible for the formation of the active metabolite, the current studies were conducted with R-95913 as the substrate. Incubations required supplementation with reduced glutathione. Hyperbolic kinetics (K(m) 21-30 microM), consistent with a single enzyme predominating, were observed after incubations with human liver microsomes. Correlation analyses revealed a strong relationship between R-138727 formation and CYP3A-mediated midazolam 1'-hydroxylation (r(2) = 0.98; p < 0.001) in a bank of characterized human liver microsomal samples. The human lymphoblast-expressed enzymes capable of forming R-138727, in rank order of rates, were CYP3A4>CYP2B6>CYP2C19 approximately CYP2C9>CYP2D6. A monoclonal antibody to CYP2B6 and the CYP3A inhibitor ketoconazole substantially inhibited R-138727 formation, whereas inhibitors of CYP2C9 (sulfaphenazole) and CYP2C19 (omeprazole) did not. Scaling of in vitro intrinsic clearance values from expressed enzymes to the whole liver using a relative abundance approach indicated that either CYP3A4 alone or CYP3A4 and CYP2B6 are the major contributors to R-138727 formation. R-95913 and R-138727 were also examined for their ability to inhibit metabolism mediated by five P450s. R-138727 did not inhibit the P450s tested. In vitro, R-95913 inhibited CYP2C9, CYP2C19, CYP2D6, and CYP3A, with K(i) values ranging from 7.2 microM to 82 microM, but did not inhibit CYP1A2. These K(i) values exceed circulating concentrations in humans by 3.8- to 43-fold. Therefore, neither R-95913 nor R-138727 is expected to substantially inhibit the P450-mediated metabolism of coadministered drugs.