Pharmacokinetics and toxicology of therapeutic proteins:Advances and challenges

Significant progress has been made in understanding pharmacokinetics (PK),pharmacodynamics (PD),as well as toxicity profiles of therapeutic proteins in animals and humans,which have been in commercial development for more than three decades.However,in the PK arena,many fundamental questions remain to be resolved.Investigative and bioanalytical tools need to be established to improve the translation of PK data from animals to humans,and from in vitro assays to in vivo readouts,which would ultimately lead to a higher success rate in drug development.In toxicology,it is known,in general,what studies are needed to safely develop therapeutic proteins,and what studies do not provide relevant information.One of the major complicating factors in nonclinical and clinical programs for therapeutic proteins is the impact of immunogenicity.In this review,we will highlight the emerging science and technology,as well as the challenges around the pharmacokinetic-and safety-related issues in drug development of mAbs and other therapeutic proteins.

Quantitative determination of D_(4)-cystine in mice using LC-MS/MS and its application to the assessment of pharmacokinetics and bioavailability

Cystine is the primary source material for the synthesis of glutathione.However,the pharmacokinetics and tissue distribution of cystine are largely unknown.A surrogate analyte D_(4)-cystine was employed to generate calibration curves for the determination of levels of D_(4)-cystine and endogenous cystine in mice by liquid chromatography-tandem mass spectrometry(LC-MS/MS).Validation assessments proved the sensitivity,specificity and reproducibility of the method with a lower limit of quantification(LLOQ)of 5 ng/mL over 5e5000 ng/mL in plasma.The pharmacokinetics of D_(4)-cystine were evaluated after administering injections and oral solutions,both of which minimally impacted endogenous cystine levels.The absolute bioavailability of cystine was 18.6%,15.1%and 25.6%at doses of 25,50 and 100 mg/kg,respectively.Intravenously injected D_(4)-cystine resulted in dramatically high plasma levels with reduced levels in the brain and liver.Intragastrically administered D_(4)-cystine resulted in high levels in the plasma and stomach with relatively low levels in the lung,kidney,heart and brain.

Identification of bioactive anti-angiogenic constitutes targeting tumor endothelial cells in Shenmai Injection using multidimensional pharmacokinetics

OBJECTIVE To identify the bioactive anti-angiogenic constitutes targeting tumor endothelial cells(TECs)in Shenmai Injection(SMI).METHEODS For pharmacokinetic(PK)studies,Balb/c mice harboring human colorectal cancer(LoVo)xenografts were treated with SMI 10 mL·kg^-1 daily for 1 or 8 d.Multidimensional PK profiles of ginsenosides in plasma,subcutaneous tumors,and TECs were investigated.For PD studies,the tumor-bearing mice Intravital multi-photon imaging and CD31 immunofluorescence staining were used to evaluate the number of microves⁃sels and braches.Double staining of CD31 and α-SMA was performed to evaluate pericytes coverage ratios around vessels.ELISA was performed to determine the concentrations of VEGF and FGF in tumor tissues.For synergistic anti-tumor study,the tumor-bearing mice were treated with SMI 10 mL·kg^-1 daily,Rd 5 mg·kg^-1 daily with or without 5-FU 15 mg·kg^-1 every 3 d for 20 d.HPLC-MS/MS was used to determine the concentrations of 5-FU in plasma and tumor tissues.RESULTS SMI decreased the number of microvessels(P<0.05)and vessel branches(P<0.05)and improved vascular pericytes coverage(P<0.05).PK studies showed that the concentrations of protopanaxadiol-type(PPD)ginsenosides(Rb1,Rb2/Rb3,Rc,and Rd)in both,plasma and tumors,were higher than those of protopanaxatriol-type(Rg1 and Re)and oleanane-type(Ro)ginsenosides.Among PPD ginsenosides,Rd exhibited the greatest concentrations in tumors and TECs after repeated injection.In fact,the proportion of Rd in the detectable components of SMI gradually increased in the following order:SMI formula(2.8%),plasma(16.0%),tumor tissues(34.3%),and TECs(40.3%).In vivo bioactivity results showed that Rd 5 mg·kg^-1 daily significantly decreased the number of microvessels(P<0.05)and vessel branches(P<0.05)and increased pericytes coverage(P<0.05)while Rd 0.5 mg·kg^-1 daily,Rb1 and Rg1 had no significant effect on them.Rd 5 mg·kg^-1 suppressed the expression of VEGF and FGF simultaneously.Rd 5 mg·kg^-1 enhanced the antitumor effect of 5-FU via increasing the distribution of 5-FU in tumor tissues(P<0.05)in xenograft mice.CONCLUSION Ginsenoside Rd may be the major bioactive anti-angiogenic constituent targeting TECs after SMI treatment.

Pharmacokinetics Evaluation of Nimotuzumab in Combination with Doxorubicin and Cyclophosphamide in Patients with Advanced Breast Cancer

EGFr （Epidermal growth factor receptor） overexpression has been detected in many tumors of epithelial origin, specifically in breast cancer and it is often associated with tumor growth advantages and poor prognosis. The nimotuzumab is a genetically engineered humanized MAb （monoclonal antibody） that recognizes an epitope located in the extracellular domain of human EGFr. The aim of this study was to assess the pharmacokinetics of nimotuzumab in patients with locally advanced breast cancer who are receiving neoadyuvant therapy combined with the AC chemotherapy regimen （i.e., 60 mg/m2 of Doxorubicin and 600 mg/m2 of Cyclophosphamide in 4 cycles every 21 days）. A single center, non-controlled, open Phase I clinical trial, with histopathological diagnosis of locally advanced stage III breast cancer, was conducted in 12 female patients. Three patients were enrolled at each of the following fixed dose levels： 50, 100, 200 and 400 mg/week. Multiple intermittent short-term intravenous infusions of nimotuzumab were administered weekly, except on weeks 1 and 10, when blood samples were drawn for pharmacokinetic assessments. Nimotuzumab showed dose-dependent kinetics. No anti-idiotypic response against nimotuzumab was detected in blood samples of participants. There was not interaction between the administration of nimotuzumab and chemotherapy at the dose levels studied. The optimal biological doses ranging were estimated to be 200 mg/weekly to 400 mg/weekly.

Relationship of quantitative structure and pharmacokinetics in fluoroquinolone antibacterials

AIM： To study the relationship between quantitative structure and pharmacokinetics （QSPkR） of fluorocluinolone antibacterials.METHODS： The pharmacokinetic （PK） parameters of oral fluoroquinolones were collected from the literature. These pharmacokinetic data were averaged, 19 compounds were used as the training set, and 3 served as the test set. Genetic function approximation （GFA） module of Cerius2 software was used in QSPkR analysis.RESULTS： A small volume and large polarizability and surface area of substituents at C-7 contribute to a large area under the curve （AUC） for fluoroquinolones. Large polarizability and small volume of substituents at N-1 contribute to a long half life elimination.CONCLUSION： QSPkR models can contribute to some fluoroquinolones antibacterials with excellent pharmacokinetic properties.

Pharmacokinetics and Pharmacodynamics of Subcutaneous Single Doses of Pegylated Human G-CSF Mutant(PEG30-rhG-CSF) in Beagle Dogs

OBJECTIVE To compare the pharmacokinetics and pharmacodynamics of PEG30-rhG-CSF administered to beagle dogs at three different dosages with PEG20-rhG-CSF administered at one dosage, and to provide an experimental basis for clinical trials.METHODS Beagle dogs received single, subcutaneous doses of PEG30-rhG-CSF at 100, 200 and 400 μg/kg or PEG20-rhG-CSF at 200 μg/kg. PEG30-rhG-CSF and PEG20-rhG-CSF concentrations in serum were analyzed using an enzymeqinked immunosorbent assay （ELISA）. WBC, ANC and PLT counts of whole blood samples were measured using fully automated analytic instrumentation. Pharmacokinetic and pharmacodynamic parameters were calculated using DAS 2.0 statistical analysis software.METHODS Beagle dogs received single, subcutaneous doses of PEG30-rhG-CSF at 100, 200 and 400 μg/kg or PEG20-rhG-CSF at 200μg/kg. PEG30-rhG-CSF and PEG20-rhG-CSF concentrations in serum were analyzed using an enzyme-linked immunosorbent assay （ELISA）. WBC, ANC and PLT counts of whole blood samples were measured using fully automated analytic instrumentation. Pharmacokinetic and pharmacodynamic parameters were calculated using DAS 2.0 statistical analysis software. RESULTS The pharmacokinetic parameters of PEG30-rhG-CSF calculated from the serum concentration data determined by ELISA were as follows： the mean elimination half-life （t1/2ke） was 40.6 h （33.5-45.4 h）; the mean time to reach peak concentration （Tmax） was 19.2 h （11.7-24.0 h）; the drug clearance from the serum （CL） was decreased with increasing doses; the peak concentration （Cmax） and the area under the serum concentration-time curve （AUC） were increased with increasing doses. For PEG20-rhG- CSF, the half-life was shorter （12 h） and Tmax was achieved much earlier （10 h） relative to PEG30-rhG-CSF. The AUC of PEG30- rhG-CSF was much greater than that of PEG20-rhG-CSF, and the relative bioavailability with a subcutaneous injection was 158.7%. Administration of single doses of PEG30-rhG-CSF resulted in substantial increases in the absolute The time to reach ANC （ANCTmax） neutrophil count （ANC）. was 72 h. The maximum observed absolute neutrophil counts （ANCmax） and the area over the baseline effect curve （AOBEC） was increased with increasing doses. The effect-elimination half-life （t1/2E） ranged from 60 h to 80 h after subcutaneous administration. The PLT count was slightly elevated 8-12 h after s.c. injection, and declined after 24 h. CONCLUSION The mean elimination half-life of PEG30-rhG- CSF was longer than that of PEG20-rhG-CSF at the same dose, and the other main pharmacokinetic and pharmacodynamic parameters of PEG30-rhG-CSF, including C ANCmax, AUC and AOBEC were much greater than those following PEG20-rhG-CSF injection.

The influence of genetic polymorphisms in drug metabolism enzymes and transporters on the pharmacokinetics of different fluvastatin formulations

The purpose of the present study was to investigate the impact of genetic polymorphism on fluvastatin pharmacokinetics.In addition,we compared the fluvastatin pharmacokinetics differences between extended-release(ER)80 mg tablet and immediate-release(IR)40 mg capsule in terms of drug metabolism enzyme and transporter genetic polymorphisms.In this open-label,randomized,two-period,two-treatment,crossover study(n=24),effects of ABCG2,SLCO1B1,ABCB1,CYP2C9 and CYP3A5 polymorphisms on the pharmacokinetics of fluvastatin were analyzed.The administration dosage for IR 40 mg and ER 80 mg were twice and once daily,respectively,for total 7 d.Blood samples for pharmacokinetic evaluation were taken on the 1st and 7th d.The lower exposure following ER was observed.For ER tablets,SLCO1B1 T521C genotype correlated with AUC 0-24 of repeat doses(P=0.010).SLCO1B1 T521C genotype had no statistically significant effect on AUC 0-24 of IR capsule of fluvastatin after single or repeated doses.In vitro study demonstrated that when the concentration of fluvastatin was low(<1μmol/l),the uptake of fluvastatin in the HEK293-OATP1B1 with SLCO1B1521TT(K m=0.18μmol/l)was faster than that with SLCO1B1521CC(K m=0.49μmol/l),On the other hand,when concentration reached to higher level(>1μmol/l),transport velocity of fluvastatin by HEK293-OATP1B1 with SLCO1B1521TT(K m=11.4μmol/l)and with SLCO1B1521TCC(K m=15.1μmol/l)tend to be the same.It suggests that the increased effect of SLCO1B1 T521C genotype on ER formulation of fluvastatin was mainly caused by lower blood concentrations.We recommend that formulation should be incorporated into future pharmacogenomics studies.

Influence of CYP2B6 516G > T and Long Term HAART on Population Pharmacokinetics of Efavirenz in Rwandan Adults on HIV and Tuberculosis Cotreatment

Aim: To describe the pharmacokinetic parameters of efavirenz and estimate its clearance (CL/F) accounting simultaneously for drug-drug interactions and CYP2B6 genetic polymorphism. Methods: Genotyping of 516G > T single nucleotide polymorphism of CYP2B6 was performed using a PCR-based technology and plasma efavirenz concentrations were measured by high performance liquid chromatography on blood samples from 76 HIV adults co-infected with tuberculosis who had received an efavirenz-based regimen. Data were analyzed using population modeling with NONMEM. Results: The absorption rate constant and the apparent volume of distribution in the final model were 1.9 h-1 and 580 L/70kg, respectively. The CL/F at baseline was 11.8 L/h/70kg, 8.8 L/h/70kg and 3.9 L/h/70kg for patients carrying the G/G, G/T and T/T genotypes of CYP2B6 516G > T, respectively, in patients who were administered tuberculosis (TB) treatment prior to HIV treatment (Group A);and 16.7 L/h/70kg, 10.6 L/h/70kg and 1.8 L/h/70kg for G/G, G/T and T/T genotype patients respectively, in patients with previous exposure to HIV treatment (Group B). The CL/F at baseline and steady state was always higher in Group B compared to Group A patients. Expectedly, carriers of CYP2B6 516G/G and T/T genotypes exhibited higher and lower CL/F, respectively. Conclusion: Our results indicated that the CL/F of efavirenz in the population studied was predictably different due to whether the patients were mono-treated for TB with HAART deferred or for HIV before initiation of TB therapy, and to CYP2B6 516G > T variant, implying that both CYP2B6 genetic polymorphisms and previous efavirenz-based HAART should be taken into account when adjusting efavirenz dose.

Recent advances in the translation of drug metabolism and pharmacokinetics science for drug discovery and development

Drug metabolism and pharmacokinetics(DMPK) is an important branch of pharmaceutical sciences.The nature of ADME(absorption,distribution,metabolism,excretion) and PK(pharmacokinetics) inquiries during drug discovery and development has evolved in recent years from being largely descriptive to seeking a more quantitative and mechanistic understanding of the fate of drug candidates in biological systems.Tremendous progress has been made in the past decade,not only in the characterization of physiochemical properties of drugs that influence their ADME,target organ exposure,and toxicity,but also in the identification of design principles that can minimize drug-drug interaction(DDI) potentials and reduce the attritions.The importance of membrane transporters in drug disposition,efficacy,and safety,as well as the interplay with metabolic processes,has been increasingly recognized.Dramatic increases in investments on new modalities beyond traditional small and large molecule drugs,such as peptides,oligonucleotides,and antibody-drug conjugates,necessitated further innovations in bioanalytical and experimental tools for the characterization of their ADME properties.In this review,we highlight some of the most notable advances in the last decade,and provide future perspectives on potential major breakthroughs and innovations in the translation of DMPK science in various stages of drug discovery and development.

Pharmacokinetics of the prototype and hydrolyzed carboxylic forms of ginkgolides A, B, and K administered as a ginkgo diterpene lactones meglumine injection in beagle dogs

Ginkgo diterpene lactones meglumine injection(GDLI)is a commercially available product used for neuroprotection.However,the pharmacokinetic properties of the prototypes and hydrolyzed carboxylic forms of the primary components in GDLI,i.e.,ginkgolide A(GA),ginkgolide B(GB),and ginkgolide K(GK),have never been fully evaluated in beagle dogs.In this work,a simple,sensitive,and reliable method based on ultra-fast liquid chromatography-tandem mass spectrometry(UFLC-MS/MS)was developed,and the prototypes and total amounts of GA,GB,and GK were determined in beagle dog plasma.The plasma concentrations of the hydrolyzed carboxylic forms were calculated by subtracting the prototype concentrations from the total lactone concentrations.For the first time,the pharmacokinetics of GA,GB,and GK were fully assessed in three forms,i.e.,the prototypes,the hydrolyzed carboxylic forms,and the total amounts,after intravenous administration of GDLI in beagle dogs.It was shown that ginkgolides primarily existed in the hydrolyzed form in plasma,and the ratio of hydrolysates to prototype forms of GA and GB decreased gradually to a homeostatic ratio.All of the three forms of the three ginkgolides showed linear exposure of AUC to the dosages.GA,GB,and GK showed a constant half-life approximately 2.7,3.4,and 1.2 h,respectively,which were consistent for the forms at three dose levels(0.3,1.0,and 3.0 mg·kg^(-1))and after a consecutive injection of GDLI for 7 days(1.0 mg·kg^(-1)).

Identification of bioactive anti-angiogenic components targeting tumor endothelial cells in Shenmai injection using multidimensional pharmacokinetics

Shenmai injection(SMI)is a well-defined herbal preparation that is widely and clinically used as an adjuvant therapy for cancer.Previously,we found that SMI synergistically enhanced the activity of chemotherapy on colorectal cancer by promoting the distribution of drugs in xenograft tumors.However,the underlying mechanisms and bioactive constituents remained unknown.In the present work,the regulatory effects of SMI on tumor vasculature were determined,and the potential anti-angiogenic components targeting tumor endothelial cells(TECs)were identified.Multidimensional pharmacokinetic profiles of ginsenosides in plasma,subcutaneous tumors,and TECs were investigated.The results showed that the concentrations of protopanaxadiol-type(PPD)ginsenosides(Rb1,Rb2/Rb3,Rc,and Rd)in both plasma and tumors,were higher than those of protopanaxatriol-type(Rg1 and Re)and oleanane-type(Ro)ginsenosides.Among PPD-type ginsenosides,Rd exhibited the greatest concentrations in tumors and TECs after repeated injection.In vivo bioactivity results showed that Rd suppressed neovascularization in tumors,normalized the structure of tumor vessels,and improved the anti-tumor effect of 5-fluorouracil(5 FU)in xenograft mice.Furthermore,Rd inhibited the migration and tube formation capacity of endothelial cells in vitro.In conclusion,Rd may be an important active form to exert the anti-angiogenic effect on tumor after SMI treatment.

Effect of age on the pharmacokinetics of polymorphic nimodipine in rats after oral administration

The previous investigation has proved that their existed pharmacokinetic difference between the different crystal forms of the polymorphic drugs after oral administration.However,no systemic investigations have been made on the change of this pharmacokinetic difference,resulted either from the physiological or from the pathological factors.In this paper,we used polymorphic nimodipine(Nim) as a model drug and investigated the effect of age difference(2- and 9-month old) on the pharmacokinetics after oral delivery in rats.As the results shown,for L-form of Nim(L-Nim),the AUC0–24 hin 2-month-old rats was 343.68747.15 ng h/m L,which is 23.36% higher than that in 9-month-old rats.For H-form of Nim(H-Nim),the AUC0–24 hin 2-monthold rats was 140.91719.47 ng h/m L,which is 54.64% higher than that in 9-month-old rats.The AUC0–24 h ratio between H-Nim and L-Nim was 2.44 in 2-month-old rats and 3.06 in 9-month-old rats.Since age difference could result in unparallelled change of the absorption and bioavailability of the polymorphic drugs,the results in this experiment are of value for further investigation of crystal form selection in clinical trials and rational clinical application of the polymorphic drugs.

Pharmacokinetics of monoclonal antibodies ]nd Fc-fusion proteins

There are many factors that can influence the pharma- cokinetics （PK） of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediatad recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic anti. bodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation, Glycosyla- tion of a mAb or Fc.fusion protein can have a significant impact on the PK of these molecules, mAb charge can be important and variants with pl values of 1-2 unit difference are likely to impact PK with lower pl values being favorable for a longer half.life. Most mAbs display target mediated drug disposition （TMOO）, which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody （ADA） response and off.target binding, which require careful consideration during the discovery stage, mAbs are primarily absor- bed through the lymphatics via convection and can be conveniently administered by the subcutaneous （sc） route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be rea- sonably estimated using cynomolgus monkey data and allometric scaling methods.

Pharmacokinetics of acteoside following single dose intragastric and intravenous administrations in dogs

Acteoside(verbascoside), a phenylethanoid glycoside widely distributed in various plants, has been shown to have potential activity against Alzheimer's disease, attracting great attentions recently. The present study was designed to develop a selective and sensitive LC-MS/MS method for the determination of acteoside in biological samples and carry our a phamacokinetic(PK) study in beagle dogs. The PK parameters were calculated using non-compartmental models. Following a single-dose oral administration, acteoside was rapidly absorbed and eliminated, with Tmax being between 30 to 45 min and terminal half-life being about 90 min. The areas under the time-concentration curve(AUC) were 47.28 ± 8.74, 87.86 ± 13.33, and 183.14 ± 28.69 mg·min·L-1 for oral administration of 10, 20, and 40 mg·kg-1, respectively, demonstrating that the exposure of acteoside proportionally increased with the dose level. The absolute bioavailability of acteoside was around 4%. For all the PK parameters, there were large variations between individual dogs. In conclusion, the pharmacokinetic characteristics observed in the present study can be of great value to help better understand the pharmacological properties of acteoside and to improve the outcome of its clinical use.

天然冰片在不同年龄和性别小鼠体内的含量及樟脑转化量的比较研究

目的研究年龄和性别等因素对天然冰片在小鼠体内的含量及樟脑转化情况的影响。方法分取不同周龄和性别的小鼠,在灌服天然冰片后,以气质联用法测定小鼠体内的血浆及肝、脑、肾等器官中天然冰片和樟脑的含量,并对结果进行比较分析。结果从年龄因素看,幼龄鼠与成年鼠相比,天然冰片在幼龄小鼠体内的血药浓度及肝、肾、脑中的含量均明显高于成年小鼠,而樟脑的转化量基本相当;从性别因素看,雌性及雄性鼠体内的天然冰片及樟脑转化量无显著性差异。结论年龄因素对天然冰片在小鼠体内的含量水平有明显影响,性别因素基本无影响;而樟脑在小鼠体内的转化量则不受年龄及性别的影响。

天然冰片在小鼠组织内的GC-MS测定法和组织分布研究

目的:建立天然冰片在小鼠组织内含量测定的GC-MS法并进行组织分布研究,初步探索天然冰片的归经特征。方法:采用DB-5MS弹性毛细管色谱柱(0.25mm×30m×0.25μm);电子轰击(EI)电离方式,轰击能量为70eV,倍增电压1100V;选择性离子检测(SIM),天然冰片m/z 95,内标萘m/z128;小鼠组织样品用生理盐水匀浆后,加入萘作为内标,用正己烷振荡萃取,取上清液进样测定。组织分布研究以天然冰片的CMC-Na溶液给小鼠灌胃,在不同时间点分批处死小鼠后取各组织样本,经处理后用GC-MS法测定组织中的天然冰片含量。结果:本研究建立的天然冰片GC-MS测定方法,在22ng·mL^(-1)～22μg·mL^(-1)范围内响应信号(Y)与天然冰片浓度(X)呈良好线性关系,Y=0.000486X+0.00036,R^2=0.999(n=3),最低检测限为10ng·mL^(-1),定量下限为22ng·mL^(-1),日内精密度为3.72～6.11%,日间精密度为7.29～17.6%,相对回收率和提取回收率分别为85.95～107.93%和93.04～103.03%。组织分布研究结果表明,天然冰片分布于大部分组织,单个组织内天然冰片浓度随时间延长呈现多峰现象;天然冰片在肝脏内含量最高,在心、脑、肾等重要组织内的含量也较高。结论:本研究建立的GCMS测定方法准确、可靠,可用于天然冰片在动物体内的定量分析;天然冰片在不同组织内的分布有明显差异,肝、肾、心、脑中分布含量较高;天然冰片的归经特征中有归心经的趋势。

生理药动学模型及其在中药研究中的应用

在比较药动学中经典房室模型和生理药动学模型(PBPK模型)的基础上,介绍了生理药动学模型在中药研究中的作用。与经典房室模型相比,生理药动学模型可以模拟和预测药物在器官和组织内的药动学过程,提供难以(或无法)通过实验获取的药代参数(如代谢速率常数等),预测和外推药物的药动过程和提供内剂量经时过程,在药代药动层面辅助药物的作用机制研究等方面具有更大的优势。在中药研究过程中,生理药动学模型可以在完善中药药性(归经)理论、探索中药复方配伍规律、探索含马兜铃酸类药物及有毒中药的作用机理等方面可发挥积极作用。

Potential synergic mechanism of Wutou-Gancao herb-pair by inhibiting efflux transporter P-glycoprotein

Wutou-Gancao herb-pair is extensively used to attenuate the toxicity and enhance the efficacy of aconite.In this study,potential synergic mechanism of the herb pair was investigated by utilizing multiple ap-proaches.In silico and in vitro Caco-2 cell models were applied to study the potential binding mode of bioactive ingredients existing in liquorice with P-glycoprotein(P-gp),as well as the inhibition effects on P-gp.Additionally,anti-inflammatory activity of aconitine(AC)combined with active ingredients of liquorice,as well as pharmacokinetic patterns of AC after co-administration was investigated.Anti-inflammatory effect of AC(1 mg/kg)in rats was enhanced in combination with bioactive ingredients of liquorice(10 mg/kg).In the meanwhile,the exposure of AC in vivo was altered,in terms of Cmax and AUC.For instance,the Cmax and AUC were increased to 1.9 and 1.3 folds,respectively,when used in combination with liquiritigenin.The in silico study revealed the potential binding mode with outward facing conformation of P-gp.The resulting data obtained from transport of rhodamine-123(Rh-123)across Caco-2 cell monolayer further indicated that the function of P-gp was inhibited by chemicals in liquorice.The synergic effect was therefore proposed to be attributed to inhibition of P-gp by liquorice since AC has been demonstrated to be the substrate of P-gp.The resuls revealed that potential synergic mechanism of Wutou-Gancao herb-pair by inhibiting function of key efflux transporter P-gp to enhance the exposure of AC in systematic circulation,and further the anti-inflammatory effect,which helps clarify the compatibility rationale of these two herbs.

Simultaneous quantitation of atorvastatin and its two active metabolites in human plasma by liquid chromatography/(–) electrospray tandem mass spectrometry

A sensitive, accurate and selective liquid chromatography-tandem mass spectrometry method （LC-MS/MS） was developed and validated for the simultaneous quantitation of atorvastatin （AT） and its equipotent hydroxyl metabolites, 2-hydroxy atorvastatin （2-AT） and 4-hydroxy atorvastatin （4-AT）, in human plasma. Electrospray ionization （ESI） interface in negative ion mode was selected to improve the selectivity and the sensitivity required for this application. Additionally, a solid phase extraction （SPE） step was performed to reduce any ion-suppression and/or enhancement effects. The separation of all compounds was achieved in less than 6 min using a C18 reverse-phase fused-cores column and a mobile phase, composed of a mixture of 0.005%formic acid in water：acetonitrile：methanol （35：25：40, v/v/v）, in isocratic mode at a flow rate of 0.6 mL/min. The method has lower limit of quantitation （LLOQ） of 0.050 ng/mL for all analytes. The method has shown tremendous reproducibility, with intra-and inter-day precision less than 6.6%, and intra- and inter-day accuracy within 74.3% of nominal values, for all analytes, and has proved to be highly reliable for the analysis of clinical samples.