Everolimus-inhibited multiple isoforms of UDP-glucuronosyltransferases (UGTs).

1. Everolimus is an inhibitor of mammalian target of rapamycin (mTOR) and has been clinically utilized to prevent the rejection of organ transplants. This study aims to determine the inhibition of everolimus on the activity of phase-II drug-metabolizing enzymes UDP-glucuronosyltransferases (UGTs). 2. The results showed that 100 µM of everolimus exerted more than 80% inhibition toward UGT1A1, UGT-1A3 and UGT-2B7. UGT1A3 and UGT2B7 were selected to elucidate the inhibition mechanism, and in silico docking showed that hydrogen bonds and hydrophobic interactions mainly contributed to the strong binding of everolimus toward the activity cavity of UGT1A3 and UGT2B7. Inhibition kinetic-type analysis using Lineweaver-Burk plot showed competitive inhibition toward all these UGT isoforms. The inhibition kinetic parameters (Ki) were calculated to be 2.3, 0.07 and 4.4 µM for the inhibition of everolimus toward UGT1A1, UGT-1A3 and UGT-2B7, respectively. 3. In vitro-in vivo extrapolation (IVIVE) showed that [I]/Ki value was calculated to be 0.004, 0.14 and 0.002 for UGT1A1, UGT-1A3 and UGT-2B7, respectively. Therefore, high DDI potential existed between everolimus and clinical drugs mainly undergoing UGT1A3-catalyzed glucuronidation.

Inhibition of human CYP3A4 and CYP3A5 enzymes by gomisin C and gomisin G, two lignan analogs derived from Schisandra chinensis.

Gomisin C (GC) and gomisin G (GG) are two lignan analogs isolated from the Traditional Chinese Medicine Schisandra chinensis which possesses multiple pharmacological activities. However, the potential herb-drug interactions (HDI) between these lignans and other drugs through inhibiting human cytochrome P450 3A4 (CYP3A4) and CYP3A5 remains unclear. In the present study, the inhibitory action of GC and GG on CYP3A4 and CYP3A5 were investigated. The results demonstrated that both GC and GG strongly inhibited CYP3A-mediated midazolam 1'-hydroxylation, nifedipine oxidation and testosterone 6ß-hydroxylation. Notably, the inhibitory intensity of GC towards CYP3A4 was stronger than CYP3A5 when using midazolam and nifedipine as substrates. While inhibition of GC towards CYP3A5 was weaker than CYP3A4 when using testosterone as substrate. In contrast, GG showed a stronger inhibitory activity on CYP3A5 than CYP3A4 without substrate-dependent behavior. In addition, docking simulations indicated that the π-π interaction between CYP3A4 and GC, and hydrogen-bond interaction between CYP3A5 and GG might result in their different inhibitory actions. Furthermore, the AUC of drugs metabolized by CYP3A was estimated to increase by 8%-321% and 2%-3190% in the presence of GC and GG, respectively. These findings strongly suggested that GC and GG showed high HDI potentials, and the position of methylenedioxy group determined their different inhibitory effect towards CYP3A4 and CYP3A5, which are of significance for the application of Schisandra chinensis-containing herbs.

The Inhibition of the Components from Shengmai Injection towards UDP-Glucuronosyltransferase.

The mechanism of shengmai injection- (SMI-) related drug-drug interaction remains unclear. Evaluation of the inhibition potential of SMI's ingredients towards UDP-glucuronosyltransferases (UGTs) activity will provide a new insight to understand SMI-related drug-drug interaction. In vitro incubation system to model UGT reaction was used. Recombinant UGT isoforms-catalyzed 4-methylumbelliferone (4-MU) glucuronidation and UGT1A4-catalyzed trifluoperazine (TFP) glucuronidation reactions were employed to phenotype the inhibition profile of maidong's components towards the activity of UGT isoforms. Different inhibition potential of maidong's components towards various UGT isoforms was observed. Based on the inhibition kinetic investigation results, ophiopogonin D (OD) noncompetitively inhibited UGT1A6 and competitively inhibited UGT1A8, ophiopogonin D' (OD') noncompetitively inhibited UGT1A6 and UGT1A10, and ruscorectal (RU) exhibited competitive inhibition towards UGT1A4. The inhibition kinetic parameters were calculated to be 20.6, 40.1, 5.3, 9.0, and 0.02 µM, respectively. In combination with our previous results obtained for the inhibition of UGT isoforms by ginsenosides and wuweizi components, the important SMI ingredients exhibiting strong inhibition towards UGT isoforms were highlighted. All the results obtained in the present study provide a new insight to understand SMI-related drug-drug interaction.

Comparison of inhibition capability of scutellarein and scutellarin towards important liver UDP-glucuronosyltransferase (UGT) isoforms.

Scutellarin is an important bioactive flavonoid extracted from Erigeron breviscapus (Vant.) Hand-Mazz, and scutellarein is the corresponding aglycone of scutellarin. The present study aims to compare the inhibition potential of scutellarin and scutellarein towards several important UDP-glucuronosyltransferase (UGT) isoforms, including UGT1A1, UGT1A6, UGT1A9 and UGT2B7. It was demonstrated that scutellarein exerted stronger inhibition towards the tested UGT isoforms than scutellarin. Furthermore, the inhibition kinetic type and parameters (Ki ) were determined for the scutellarein's inhibition towards these UGT isoforms. Competitive inhibition of scutellarein towards all these UGT isoforms was demonstrated, and the Ki values were calculated to be 0.02, 5.0, 5.8 and 35.9 µM for UGT1A1, 1A6, 1A9 and 2B7, respectively. Using in vivo maximum plasma concentration of scutellarein in rat, the in vitro-in vivo extrapolation was performed to predict in vivo situation, indicating the most possible in vivo adverse effects due to the inhibition of scutellarein towards UGT1A1. All these results remind us to monitor the utilization of scutellarin and scutellarein, and the herbs containing these two components.

Optimal duration of fluorouracil-based adjuvant chemotherapy for patients with resectable gastric cancer.

BACKGROUND: Although several clinical trials have suggested that postoperative adjuvant chemotherapy can improve survival of patients with gastric cancer, the optimal treatment duration has not been studied. This retrospective analysis evaluated the outcomes of patients with gastric cancer treated with six cycles of fluorouracil-based treatment compared with a cohort treated with four or eight cycles. METHODS: We retrospectively identified 237 patients with stage IB-IIIC gastric cancer who received four, six, or eight cycles of fluorouracil-based adjuvant chemotherapy administered every 3 weeks after radical gastrectomy. The endpoint was overall survival (OS). Factors associated with prognosis were also analyzed. RESULTS: The estimated 3-year OS rates for the four-, six-, and eight-cycle cohorts were 54.4%, 76.1%, and 68.9%, respectively; and the estimated 5-year OS rates were 41.2%, 74.0%, and 65.8%, respectively. Patients who received six cycles were more likely to have a better OS than those who received four cycles (P = 0.002). Eight cycles failed to show an additional survival benefit (P = 0.454). In the multivariate analysis, the number of chemotherapy cycles was associated with OS independent of clinical covariates (P<0.05). Subgroup analysis suggested that among patients in all age groups examined, male patients, and subgroups of fluorouracil plus oxaliplatin combined chemotherapy, stage III, poor differentiation, and gastrectomy with D2 lymphadenectomy, six cycles of adjuvant chemotherapy were associated with a statistically significant benefit of OS compared with four cycles (P<0.05). CONCLUSIONS: Six cycles of adjuvant chemotherapy might lead to a favorable outcome for patients with gastric cancer, and two further cycles could not provide an additional clinical benefit.