[The in vitro transport mechanism of bentysrepinine: a novel anti-hepatitis B virus drug candidate].

Bentysrepinine (Y101), a derivative of phenylalanine dipeptide, is a novel drug candidate for the treatment of hepatitis B virus (HBV) infection. Our previous preclinical pharmacokinetic study showed that its in vivo absorption and distribution characteristics were probably related to transmembrane transport after Y101 was administered intragastically in rats. In this study, Caco-2 and MDCK-MDR1 cell models were used to investigate interactions between Y101 and P-gp through the apparent permeation coefficient (P(app)) and efflux ratio (RE); the results showed that Y101 was a substrate of P-gp. In addition, gene-transfected cell models, HEK293-h OATP1B1, HEK293-h OATP2B1 and CHO-PEPT1 were used to evaluate the affinity to OATP1B1, OATP2B1 and PEPT1. The results suggest that Y101 has a weak inhibitory effect on OATP1B1 and OATP2B1, and Y101 may not be substrates of OATP1B1, OATP2B1 or PEPT1. The above results can be used to explain the in vivo absorption and distribution characteristics, and to provide a scientific basis for the further development of Y101.

[The in vitro inhibition and induction of cytochrome P450 activities by bentysrepinine: a novel candidate of anti-hepatitis B virus drug].

Bentysrepinine (Y101), a derivative of phenyalanine dipeptide, has a novel mechanism in the treatment of hepatitis B virus (HBV) infection with a good anti-HBV effect. In the present study, a fluorometric-based high throughput method using cytochrome P450 (CYP) screening kit was adopted to evaluate in vitro inhibition potential of Y101 on CYP isoenzymes by calculating remaining enzyme activities and inhibitory potential (IC(50) values) using the determined values of fluorescence intensity. The result showed that Y101 exhibited little activity in the inhibition of CYP1A2, CYP3A4, CYP2C9, CYP2C19 and CYP2D6 (IC(50) > 100 µmol·L(-1)). Y101 was used to treat human primary hepotocytes for 72 h, and the enzyme activities of CYP1A2, CYP2B6 and CYP3A4 were determined with a cocktail of probe substrates for the three CYP isoforms. The metabolites were simultaneously determined using a LC-MS/MS method. Y101 had no activity in the induction of CYP1A2, CYP2B6 and CYP3A4 on the basis of the following results: 1 The ratio of enzyme activities between test and control groups were all below than 1 (varied from 0.662 to 0.928); 2 The induction potential of Y101 were lower than forty percent compared with that of positive groups. The above results suggest that Y101 has little activity in the regulation of metabolic drug-drug interactions based on the CYP isoform changes following co-administration of drugs.

Effects of Drug Transporters on Pharmacological Responses and Safety.

Recently, it is realized that transporters, apart from enzymes, play a key role in drug metabolism and pharmacokinetics. More and more pharmaceutical researchers focused on transporter study and found that drug transporters not only involved in pharmacokinetics including absorption, distribution, metabolism and excretion (ADME). but also in Drug-Drug interactions (DDIs). DDIs induced by drug transporters are the important safety evaluation factors which have to be taken into account at stage of drug discovery and development. Therefore, it should pay more attention to the studies on step of preclinical and clinical trial. In this review, the author focused on the effects of drug transporters on pharmacological and safety responses, such as the effects on plasma elimination half-lives, on drug accumulation in body after repeated dosing, on potentiating either pharmacological or adverse effects and molecular mechanisms of transporter-mediated DDIs. Present studies showed that DDIs involving the drug transporters including ABC transporters, organic anion and cation transporters, peptide transporters, monocarboxylate transporters, nucleoside transporters and folate transporters, and the possible side effects derived from clinical combination therapy must pay attention. The author also discussed the molecular mechanisms of transporter-mediated DDIs by the data obtained from preclinical and clinical studies, and inferred the available curative effects and the potential risk of the drug combination involving these drug transporters, which provides a reference for the safety of clinical medication and a consideration for a successful drug discovery. This article carefully reviewed transporter-based DDIs and highlighted areas that DDIs were poorly predicted through transporters or areas are still confronted with challenges in future.

The Targeted-liposome Delivery System of Antitumor Drugs.

The liposome delivery system has been intensively explored as novel drug delivery system (DDS) for antitumor drugs, due to its safety, selective cytotoxicity, long circulation and slow elimination in blood, which is favorable for cancer therapy. The liposome-based chemotherapeutics are used to treat a variety of cancers to enhance the therapeutic index of antitumor drugs. Here, the author reviewed the important targets for cancer therapy and the pharmacokinetic behavior of liposomal drugs in vivo, as well as the application of the targeting liposomal system in cancer therapy. Considering further application for clinical use, the great challenges of the liposome-based delivery system were also proposed as follows: 1) prepare stealth liposome with steric stabilization and further enhance the therapeutic effects and safety; 2) explore more safe clinical targets and complementary or different types of targeting liposome; 3) thirdly, more investment is needed on the research of pharmacokinetics of the elements such as the ligands (antibody), PEG and lipids of liposome delivery system as well as safety evaluation. Considering the complex process of the liposomal encapsulation drugs in vivo, the author inferred that there are maybe different forms of the encapsulation drug to be internalized by the tumor tissues at the same time and space, although there are little reports on it.

Inhibitory effect of medicinal plant-derived carboxylic acids on the human transporters hOAT1, hOAT3, hOATP1B1, and hOATP2B1.

A significant number of organic carboxylic acids have been shown to influence the absorption and distribution of drugs mediated by organic anion transporters (OATs). In this study, uptake experiments were performed to assess the inhibitory effects of cinnamic acid, ferulic acid, oleanolic acid, deoxycholic acid, and cynarin on hOAT1, hOAT3, hOATP1B1, and hOATP2B1. After a drug-drug interaction (DDI) investigation, cinnamic acid, ferulic acid, deoxycholic acid, and cynarin were found and validated to inhibit hOAT1 in a competitive manner, and deoxycholic acid was found to be an inhibitor of all four transporters. The apparent 50% inhibitory concentrations of cinnamic acid, ferulic acid, deoxycholic acid, and cynarin were estimated to be 133.87, 3.69, 90.03 and 6.03 µmol·L(-1) for hOAT1, respectively. The apparent 50% inhibitory concentrations of deoxycholic acid were estimated to be 9.57 µmol·L(-1) for hOAT3, 70.54 µmol·L(-1) for hOATP1B1, and 168.27 µmol·L(-1) for hOATP2B1. Because cinnamic acid, ferulic acid, and cynarin are ingredients of food or food additives, the present study suggests there are new food-drug interactions to be disclosed. In addition, deoxycholic acid may be used as a probe for studying the correlation of OATs and OATPs.

Herb-drug interactions involving drug metabolizing enzymes and transporters.

Herbal medicines and their active ingredients are widely used worldwide, and they have become an important part of clinical medicine. The combined use of herbs and drugs has increased the possibility of pharmacokinetic and pharmacodynamic interactions. Clinical studies have demonstrated that the combined use of herbs and drugs can enhance or attenuate the drug efficacy and toxicity. The herb-drug combinations may reduce a drug efficacy and lead to treatment failure when long-term administration. Case reports detailing serious clinical adverse reactions have promoted studies on the interactions between herbs and drugs. This review highlights recent knowledge to discuss herb-drug interactions involving metabolizing enzymes and drug transporters. Drug transporters are widely present in body and play an important role in the absorption, distribution, excretion and metabolism, efficacy, and toxicity of drugs. Investigation of transporters has developed rapidly since 1990s, the effects of many transporters on the pharmacokinetics of drugs and herb-drug interactions have been reported. Some concepts on drug transporters issued experimentally and clinically drug-drug and herb-drug interactions have applied in many studies. Methodology studies are very important for understanding the mechanism, considerations and evaluation of experiments and clinical studies on drug metabolizing enzymes and transporters in drug-drug interactions.