重组人^125I—CTLA4Ig在大鼠体内吸收、组织分布及排泄的药代动力学研究

目的:研究重组人单克隆抗体 CTLA4Ig 经静脉单次给药后在 Wistar 大鼠体内的药代动力学、组织分布及排泄过程,评价剂量与药代动力学参数之间的关系。方法:54只 Wistar 大鼠(雌雄各半)分为9组(雌雄各3只),3组分别单次给药(100,30,10 mg·kg~(-1),按不同时间点采血分离血浆,TCA 沉淀法测定~(125)I-CTLA4Ig 的放射强度,用所得结果评价~(125)I-CTLA41g 在大鼠体内的暴露情况,根据非房室统计矩模型用 WinNolin 药代软件进行曲线拟合并计算药代动力学参数;其余6组单次给药30mg·kg~(-1),其中4组大鼠给药后不同时间麻醉处死、解剖测定~(125)I-CTLA4Ig 组织分布,另外1组给药后收集不同时段的尿粪评价~(125)I-CTLA4Ig 的排泄过程,最后1组麻醉后插管给药收取胆汁评价胆汁排泄。结果:Wistar 大鼠分别静脉单次注射高、中、低(100,30,10mg·kg~(-1))后,T_(1/2)分别为(41.25±0.90)h、(47.25±1.79)h 和(54.81±1.96)h,CLs 与 Vss 随着剂量的减小发生减少的变化,血药浓度-时间曲线下面积 AUC_(INF)(h·μg·mL~(-1))分别为35833.37±2618.69,14171.04±1118.25,6186.85±480.35,剂量之比为10:3:1,对应的 AUC 比值为5.8:2.3:1,剂量与 AUC 成正相关性,AUC=0.524·Dose 0.5821,相关系数 R~2=0.9975,但是 AUC 的增加量小于剂量的增加量;单次静脉给药~(125)I-CTLA4Ig 30mg·kg~(-1)后,肝肾组织中~(125)I-CTLA4Ig 的含量最高,脑含量最低;120h 经尿粪排泄量占总给药量的68.98%和6.88%;胆汁在给药后28h 其排泄量相当于总给药量的5.80%。结论:在本实验的剂量范围内,剂量与 AUC 成正相关性,AUC 的增加量小于剂量的增加量,预示在以上剂量范围内 CTLA4Ig 在 Wiatar 大鼠血浆中的浓度变化可能呈非线性药代动力学特点;肾脏为~(125)I-CTLA4Ig 的主要排泄器官;胆汁的排泄量提示~(125)I-CTLA4Ig 在大鼠体内存在肝肠循环的代谢特征。     

Absorption, distribution, metabolism, and elimination of 8-2 fluorotelomer alcohol in the rat.

The absorption, distribution, metabolism, and elimination of [3-14C] 8-2 fluorotelomer alcohol (8-2 FTOH, C7F1514CF2CH2CH2OH) following a single oral dose at 5 and 125 mg/kg in male and female rats have been determined. Following oral dosing, the maximum concentration of 8-2 FTOH in plasma occurred by 1 h postdose and cleared rapidly with a half-life of less than 5 h. The internal dose to 8-2 FTOH, as measured by area under the concentration-time curve to infinity, was similar for male and female rats and was observed to increase in a dose-dependent fashion. The majority of the 14C 8-2 FTOH (> 70%) was excreted in feces, and 37-55% was identified as parent. Less than 4% of the administered dose was excreted in urine, which contained low concentrations of perfluorooctanoate (approximately 1% of total 14C). Metabolites identified in bile were principally composed of glucuronide and glutathione conjugates, and perfluorohexanoate was identified in excreta and plasma, demonstrating the metabolism of the parent FTOH by sequential removal of multiple CF2 groups. At 7 days postdose, 4-7% of the administered radioactivity was present in tissues, and for the majority, 14C concentrations were greater than whole blood with the highest concentration in fat, liver, thyroid, and adrenals. Distribution and excretion of a single 125-mg/kg [3-14C] 8-2 FTOH dermal dose following a 6-h exposure in rats was also determined. The majority of the dermal dose either volatilized from the skin (37%) or was removed by washing (29%). Following a 6-h dermal exposure and a 7-day collection period, excretion of total radioactivity via urine (< 0.1%) and feces (< 0.2%) was minor, and radioactivity concentrations in most tissues were below the limit of detection. Systemic availability of 8-2 FTOH following dermal exposure was negligible.     

Caco-2细胞模型及其对黄酮类成分作用机制研究进展

Caco-2细胞模型作为ADME/Tox研究平台中肠吸收模型之一,已广泛用于药物动力学研究,可通过体外试验预测药物在体内的吸收和代谢,阐明药物在体内的吸收机制、毒性、药物吸收过程中的相互作用、药物的化学结构和体内转运关系以及药物代谢稳定性等。以黄酮类成分为代表,介绍Caco-2细胞模型在中药有效成分吸收代谢机制研究方面的应用进展。     

Evaluation of Prediction Accuracy for Volume of Distribution in Rat and Human Using In Vitro,In Vivo,PBPK and QSAR Methods

Volume of distribution at steady state (V_ss) is an important pharmacokinetic parameter of a drug candidate. In this study, V_ss prediction accuracy was evaluated by using: (1) seven methods for rat with 56 compounds, (2) four methods for human with 1276 compounds, and (3) four in vivo methods and three Kp (partition coefficient) scalar methods from scaling of three preclinical species with 125 compounds. The results showed that the global QSAR models outperformed the PBPK methods. Tissue fraction unbound (f_u,t) method with adipose and muscle also provided high V_ss prediction accuracy. Overall, the high performing methods for human V_ss prediction are the global QSAR models, Øie-Tozer and equivalency methods from scaling of preclinical species, as well as PBPK methods with Kp scalar from preclinical species. Certain input parameter ranges rendered PBPK models inaccurate due to mass balance issues. These were addressed using appropriate theoretical limit checks. Prediction accuracy of tissue Kp were also examined. The f_u,t method predicted Kp values more accurately than the PBPK methods for adipose, heart and muscle. All the methods overpredicted brain Kp and underpredicted liver Kp due to transporter effects. Successful V_ss prediction involves strategic integration of in silico, in vitro and in vivo approaches.     

Absorption, distribution, metabolism, and excretion of [1-¹⁴C]-perfluorohexanoate ([¹⁴C]-PFHx) in rats and mice

The absorption, tissue distribution, elimination, and metabolism of [1-¹⁴C]-PFHx in rats and mice dosed orally at 2 or 100 mg/kg was evaluated following a single dose or after 14 consecutive doses. Absorption was rapid in rats as evidenced by a short time to maximum concentration (C_max) of 30 min in male rats and 15 min in female rats at both the 2 and 100 mg/kg dose level. The plasma elimination half-life was somewhat longer in males (1.5-1.7 h) than in females (0.5-0.7 h). Absorption in the mouse was also rapid with the maximum plasma concentration occurring between 15 and 30 min after dosing. The maximum concentration was not appreciably different between male and female mice (8 μg equiv./g at 2 mg/kg; ∼350 μg equiv./g at 100 mg/kg). The primary route of elimination was via the urine. PFHx was not metabolized in rat or mouse hepatocytes, nor were any metabolites observed after oral dosing in either rodent species. Essentially 100% of the dose was eliminated in urine within 24 h demonstrating that PFHx is readily absorbed and bioavailability approaches 100%, even at a dose as high as 100 mg/kg. The route and extent of elimination was unchanged after 14 days of daily dosing. Tissues were collected at three time points (rat: 0.5, 2, and 24 h; mice: 0.25, 1, and 24 h) after dosing to investigate the tissue clearance kinetics of PFHx following a single dose at 2 or 100 mg/kg. In all tissues except skin, PFHx was not quantifiable 24 h after dosing in both sexes of the two species.     

Kinetic modelling of in vitro cell-based assays to characterize non-specific bindings and ADME processes in a static and a perfused fluidic system

Recently, physiologically based perfusion in vitro systems have been developed to provide cell culture environment close to in vivo cell environment (e.g., fluidic conditions, organ interactions). In this work, we model and compare the fate of a chemical, benzo[a]pyrene (B[a]P), in a perfusion and a standard (static well-plate) system. These in vitro systems are composed of Caco-2 and HepG2 cells so as to mimic absorption across the small intestine and intestinal and hepatic metabolism. Compartmental models were developed and calibrated with B[a]P kinetics data in the culture medium to estimate the apparent permeability of Caco-2 cells, the in vitro biotransformation of B[a]P, as well as the different routes of loss by non-specific adsorption. Our results show that non-specific binding is the main process responsible for the depletion of B[a]P in the culture media: at steady state, only 40% and 24% of the total concentration of B[a]P are bioavailable in the static and perfused systems, respectively. We also showed that Caco-2 permeability in the perfused culture system is closer to in vivo conditions than the one obtained in the static system and that higher cellular metabolic activities are observed in static conditions. Perfused in vitro systems combined with kinetic modelling are promising tools for studying in vitro the different processes involved in the toxicokinetics of xenobiotics.     

Report from the EPAA workshop: In vitro ADME in safety testing used by EPAA industry sectors

There are now numerous in vitro and in silico ADME alternatives to in vivo assays but how do different industries incorporate them into their decision tree approaches for risk assessment, bearing in mind that the chemicals tested are intended for widely varying purposes? The extent of the use of animal tests is mainly driven by regulations or by the lack of a suitable in vitro model. Therefore, what considerations are needed for alternative models and how can they be improved so that they can be used as part of the risk assessment process? To address these issues, the European Partnership for Alternative Approaches to Animal Testing (EPAA) working group on prioritisation, promotion and implementation of the 3Rs research held a workshop in November, 2008 in Duesseldorf, Germany. Participants included different industry sectors such as pharmaceuticals, cosmetics, industrial- and agro-chemicals. This report describes the outcome of the discussions and recommendations (a) to reduce the number of animals used for determining the ADME properties of chemicals and (b) for considerations and actions regarding in vitro and in silico assays. These included: standardisation and promotion of in vitro assays so that they may become accepted by regulators; increased availability of industry in vivo kinetic data for a central database to increase the power of in silico predictions; expansion of the applicability domains of in vitro and in silico tools (which are not necessarily more applicable or even exclusive to one particular sector) and continued collaborations between regulators, academia and industry. A recommended immediate course of action was to establish an expert panel of users, developers and regulators to define the testing scope of models for different chemical classes. It was agreed by all participants that improvement and harmonization of alternative approaches is needed for all sectors and this will most effectively be achieved by stakeholders from different sectors sharing data.     

Pharmacophore modeling, 3D-QSAR studies, and in-silico ADME prediction of pyrrolidine derivatives as neuraminidase inhibitors

Neuraminidase (NA) is a major glycoprotein of influenza virus which is essential for viral infection. It offers a potential target for antiviral drug development. To develop potent NA inhibitors, pharmacophore models were generated by genetic algorithm with linear assignment for hypermolecular alignment of data sets. 3D-QSAR studies were carried out on 49 molecules. Both comparative molecular field analysis (q(2) = 0.720 and r(2) = 0.947) and comparative molecular similarity indices analysis (q(2) = 0.644 and r(2) = 0.885) yielded reasonable results. A preliminary pharmacokinetic profile of these neuraminidase inhibitors was predicted using Volsurf module.