Methods to Account for Inaccuracies in the Dosing History When Performing Population Pharmacokinetic Analysis

Purpose  To develop and assess methods to account for missing dose history (MDH). Methods  A simulation study was performed with different doses, dose times and formulations using NONMEM. Four methods were used to account for MDH, these were the ideal dose method (IDM) which uses the actual dose history, the concentration minimum method (CMM) which assumes that the nominal dose history is accurate, the extrapolation subtraction method (ESM) which estimates the residual concentration at the time of the study dose and the concentration time method (CTM) where the time of the previous dose event is estimated. The CTM is a new method. Results  The CTM was superior to ESM and CMM and provided parameter estimates that were comparable in accuracy to the IDM. Conclusions  When the nominal dosing history is available then the CTM is a simple and effective method to account for potential inaccuracies in the dose history.     

A Simple Dosing Scheme for Intravenous Busulfan Based on Retrospective Population Pharmacokinetic Analysis in Korean Patients

Busulfan is an antineoplastic agent with a narrow therapeutic window. A post-hoc population pharmacokinetic analysis of a prospective randomized trial for comparison of four-times daily versus once-daily intravenous busulfan was carried out to search for predictive factors of intravenous busulfan (iBu) pharmacokinetics (PK). In this study the population PK of iBu was characterized to provide suitable dosing recommendations. Patients were randomized to receive iBu, either as 0.8 mg/kg every 6 h or 3.2 mg/kg daily over 4 days prior to hematopoietic stem cell transplantation. In total, 295 busulfan concentrations were analyzed with NONMEM. Actual body weight and sex were significant covariates affecting the PK of iBu. Sixty patients were included in the study (all Korean; 23 women, 37 men; mean [SD] age, 36.5 [10.9] years; weight, 66.5 [11.3] kg). Population estimates for a typical patient weighing 65 kg were: clearance (CL) 7.6 l/h and volume of distribution (V_d) 32.2 l for men and 29.1 L for women. Inter-individual random variabilities of CL and V_d were 16% and 9%. Based on a CL estimate from the final PK model, a simple dosage scheme to achieve the target AUC_0-inf (defined as median AUC_0-inf with a once-daily dosage) of 26.18 mg/l·hr, was proposed: 24.79·ABW^0.5 mg q24h, where ABW represents the actual body weight in kilograms. The dosing scheme reduced the unexplained interindividual variabilities of CL and Vd of iBu with ABW being a significant covariate affecting clearance of iBU. We propose a new simple dosing scheme for iBu based only on ABW.     

Population Pharmacokinetics of Sibrotuzumab, A Novel Therapeutic Monoclonal Antibody, in Cancer Patients

Population pharmacokinetics of sibrotuzumab, a humanized monoclonal antibody directed against fibroblast activation protein, were determined after multiple intravenous infusions of dosages ranging from 5 mg/m(2) to an absolute dose of 100 mg, in patients with advanced or metastatic carcinoma. In total, 1844 serum concentrations from 60 patients in three Phase I and II clinical studies were analyzed. The structural model incorporated two disposition compartments and two parallel elimination pathways from the central compartment, one linear and one nonlinear. Finally estimated pharmacokinetic parameters (%RSE) were: linear clearance CLL 22.1 ml/h (9.6), central distribution volume V1 4.13l (3.7), peripheral volume V2 3.19l (8.8), inter-compartmental clearance Q 37.6 ml/h (9.6); for the nonlinear clearance Vmax was 0.0338 mg/h (25) and Km 0.219 microg/ml (57). At serum concentrations between approximately 20 ng/ml and 7 microg/ml, the effect of the nonlinear clearance on pharmacokinetics was marked. Only at >7 microg/ml did CLL dominate overall clearance. Interindividual variability was 57% for CLL, 20% for V1 and V2, and 29% for Vmax and was larger than the inter-occasional variability of 13%. Of the many investigated patient covariates, only body weight was found to contribute to the population model. It significantly affected CLL, V1, V2 and Vmax resulting in marked differences in the model-predicted concentration-time profiles after multiple dosing in patients with low and high body weights. In conclusion, a robust population pharmacokinetic model was developed and evaluated for sibrotuzumab, which identified a possible need to consider body weight when designing dosage regimen for future clinical cancer trials.     

Assumption Testing in Population Pharmacokinetic Models: Illustrated with an Analysis of Moxonidine Data from Congestive Heart Failure Patients

Deriving a population pharmacokinetic model from real data is always associated with numerous assumptions. Violations of these assumptions, especially if undetected, may lead to inappropriate conclusions being made from the analysis. Routinely, only a few of the assumptions are explicitly stated and justified in the reporting of a population model. Here, we attempt to be exhaustive in the presentation of the assumptions made in the course of an analysis of moxonidine pharmacokinetics. The different ways that assumptions were justified, through experience, graphical examination, or additional modeling, are outlined. Models for relaxing assumptions regarding the covariate and statistical submodels, not previously reported in the area of population pharmacokinetic modeling, are also described.     

Population pharmacokinetics of antifibroblast activation protein monoclonal antibody F19 in cancer patients

AIMS: The population pharmacokinetics of 131I-mAbF19, a radiolabelled murine monoclonal antibody against fibroblast activation protein and a potential antitumour stroma agent, were investigated during two phase I studies in cancer patients. METHODS: 131I-mAbF19 serum concentration-time data were obtained in 16 patients from two studies involving imaging and dosimetry in colorectal carcinoma and soft tissue sarcoma. Doses of 0.2, 1 and 2 mg antibody were administered as 60 min intravenous infusions. The data were analysed by nonlinear mixed effect modelling. RESULTS: The data were described by a two-compartment model. Population mean values were 109 ml h(-1) for total serum clearance, 3.1 l for the volume of distribution of the central compartment, and 4.9 l for the volume of distribution at steady state. Mean terminal half-life was 38 h. Intersubject variability was high, but no patient covariates could be identified that further explained this variability. In particular, there was no influence of tumour type or mAbF19 dose. CONCLUSIONS: The pharmacokinetics of antistromal mAbF19 were well defined in these two studies with different solid tumour types, and were comparable with those of other murine monoclonal antibodies that do not bind to normal tissue antigens or blood cells.     

Efficacy and safety of trastuzumab

The human epidermal growth factor receptor (HER) 2 is overexpressed in ～ 20 – 25% of human breast cancers and is an independent adverse prognostic factor. Targeted therapy directed against this receptor has been developed in the form of a humanised monoclonal antibody, trastuzumab. This antibody has shown activity as a single agent in metastatic breast cancer both prior to chemotherapy and in heavily pretreated patients. A pivotal Phase III trial has demonstrated that its use in combination with an anthracycline or paclitaxel results in a significant improvement in survival, time to progression, and response. This has recently been reinforced by another trial with docetaxel. The HER2 status of a tumour is a critical determinant of response to trastuzumab-based treatment. Those that express HER2 at the highest level on immunohistochemistry (IHC), 3+, derive more benefit from treatment with trastuzumab than those with overexpression at the 2+ level. Benefit correlates best with tumours that are positive on fluorescence in situ hybridisation for HER2, regardless of IHC status. Treatment with trastuzumab is generally well tolerated with a low incidence of adverse events. Some patients may experience fever, chills, dyspnoea and pain, particularly with the first administration. Unexpectedly, cardiac toxicity has developed in some patients treated with trastuzumab, and this has a higher incidence in those treated in combination with an anthracycline. ‘Cross-talk’ between the oestrogen receptor and HER2 pathway has stimulated interest in using trastuzumab in combination with endocrine therapy. Current clinical trials are investigating the role of this agent in the adjuvant setting.     

Population Pharmacokinetic Analysis of Mizolastine and Validation from Sparse Data on Patients Using the Nonparametric Maximum Likelihood Method

A population analysis of the kinetics of mizolastine was performed from concentrations on 449 allergic patients, using the nonparametric maximum likelihood method (NPML). A two-compartment open model with zero-order absorption was used to describe the kinetics of mizolastine after oral administration. A heteroscedastic variance model was assumed for the error. To explain the kinetic variability, eight covariates were introduced in the analysis: gender, pharmaceutical dosage form, age, body weight, serum creatinine concentration, creatinine renal clearance, plasma levels of hepatic transaminases ASAT and ALAT. Their relationships to the kinetic parameters were studied by means of the estimated distribution of each kinetic parameter conditional on different levels of each covariate. An important interindividual kinetic variability was found for all parameters. Moreover, several kinetic parameters among which the duration of absorption were found to be influenced by pharmaceutical dosage form and gender. Body weight and creatinine renal clearance were found to have a little influence on the oral clearance and the smallest disposition rate constant. This population analysis was validated on a separate group of 247 other patients. For each observed concentration of this sample, a predictive distribution was computed using the individual covariates. Predicted concentrations and standardized prediction errors were deduced. The mean and variance of the standardized prediction errors were, respectively, 0.21 and 2.79. Moreover, in the validation sample, the predicted cumulative distribution function of each observed concentration was computed. Empirical distribution of these values was not significantly different from a uniform distribution, as expected under the assumption that the population model estimated by NPML is adequate.     

A Population Pharmacokinetic Analysis of Milrinone in Pediatric Patients After Cardiac Surgery

The purpose of this study was to ascertain the optimal pharmacokinetic model for milrinone in pediatric patients after cardiac surgery when milrinone was administered as a slow loading dose followed by a constant-rate infusion. The data used for pharmacokinetic analysis were collected in a prospective, randomized, placebo-controlled multi-center trial of milrinone as prophylaxis for the development of low cardiac output syndrome after surgery for repair of complex congenital cardiac defects. Two blood samples were randomly collected from each patient for determination of plasma milrinone concentrations with subsequent population pharmacokinetic modeling. The pharmacokinetics of milrinone in pediatric patients under 6 year's age were best described by a weight-normalized one compartment model after a slow loading dose followed by a constant-rate infusion. The volume of distribution was 482 ml kg(-1) and was independent of age. Clearance was a linear function of age given by Cl = 2.42 ml kg(-1) min(-1) [1 + 0.396*age].     

Diazepam Pharamacokinetics from Preclinical to Phase I Using a Bayesian Population Physiologically Based Pharmacokinetic Model with Informative Prior Distributions in Winbugs

Modelling is an important applied tool in drug discovery and development for the prediction and interpretation of drug pharmacokinetics. Preclinical information is used to decide whether a compound will be taken forwards and its pharmacokinetics investigated in human. After proceeding to human little to no use is made of these often very rich data. We suggest a method where the preclinical data are integrated into a whole body physiologically based pharmacokinetic (WBPBPK) model and this model is then used for estimating population PK parameters in human. This approach offers a continuous flow of information from preclinical to clinical studies without the need for different models or model reduction. Additionally, predictions are based upon single parameter values, but making realistic predictions involves incorporating the various sources of variability and uncertainty. Currently, WBPBPK modelling is undertaken as a two-stage process: (i) estimation (optimisation) of drug-dependent parameters by either least squares regression or maximum likelihood and (ii) accounting for the existing parameter variability and uncertainty by stochastic simulation. To address these issues a general Bayesian approach using WinBUGS for estimation of drug-dependent parameters in WBPBPK models is described. Initially applied to data in rat, this approach is further adopted for extrapolation to human, which allows retention of some parameters and updating others with the available human data. While the issues surrounding the incorporation of uncertainty and variability within prediction have been explored within WBPBPK modeling methodology they have equal application to other areas of pharmacokinetics, as well as to pharmacodynamics.     

Anti-EGFR strategies as an incremental step for the treatment of colorectal cancer patients: moving from scientific evidence to clinical practice

The epidermal growth factor receptor (EGFR) is a 170,000 Da transmembrane glycoprotein involved in signalling pathways affecting cellular growth, differentiation and proliferation. An abnormal overexpression of the EGFR has been described in many human tumours and implicated in the development and prognosis of malignancies, thus representing not only a possible prognostic marker, but primarily a rational molecular target for a new class of anticancer agents. Several clinical trials have been reported with the use of EGFR-targeted monoclonal antibodies and tyrosine kinase inhibitors, mainly in combination with chemotherapy for advanced colorectal cancer patients. Taken together, results available so far suggest that anti-EGFR treatment strategies represent an incremental step for the the treatment of colorectal cencer patients with a manageable and acceptable toxicity profile. Nevertheless, many critical issues are yet unresolved, such as the optimal chemotherapy regimen to combine with anti-EGFR treatment and the most adequate patients setting. Moreover, the biological selection of colorectal tumours most likely to benefit from this treatment approach is still to be defined.     

Population Pharmacokinetic and Exposure-Response Analyses of Baloxavir Marboxil in Adults and Adolescents Including Patients With Influenza

Baloxavir marboxil, a prodrug that is metabolized to baloxavir acid, suppresses viral replication by inhibiting cap-dependent endonuclease. Our aim is to characterize its pharmacokinetics and exposure-response relationships. Population pharmacokinetic analysis of the baloxavir acid was performed using 8310 plasma concentration data points from 1109 subjects. Exposure-response analyses were performed regarding the time to alleviation of symptoms and the reduction in the influenza virus titer. A 2-compartment model with first-order absorption and lag time well described the plasma concentration data for baloxavir acid, and body weight and race were found to be the most important factors influencing the clearance and distribution volume. A dose regimen based on the body weight (40 mg for patients weighing <80 kg and 80 mg for patients weighing ≥80 kg) could provide sufficient exposures for expecting efficacy irrespective of body weight or race; however, the exposures were dependent on the body weight and race. Exposure-response analyses suggested that the reduction in the influenza virus titer was greater in any exposure-based groups in baloxavir marboxil treatment than in the oseltamivir phosphate treatment and placebo groups. In conclusion, the population pharmacokinetic model and exposure-response relationships would be useful for understanding the pharmacokinetic and pharmacodynamic characteristics of baloxavir acid.     

基层医院1268例患者鼻饲给药合理性调查分析

目的:探讨基层医院鼻饲给药的合理性及影响因素,提出合理化建议,促进基层医院鼻饲给药的合理化和规范化.方法:采用回顾性分析方法,抽查2017—2018年南方医科大学附属小榄医院住院患者鼻饲给药情况,利用HIS系统和Excel软件对鼻饲给药病例数、剂型分布、联合用药及不合理用药等情况进行分类、汇总和分析.结果:共抽查鼻饲用...     

人表皮生长因子受体2、增殖细胞核抗原表达与乳腺癌患者病理特征相关性分析

目的:探讨人表皮生长因子受体2(HER-2)、增殖细胞核抗原(Ki67)表达与乳腺癌患者病理特征的相关性。方法:选取某院乳腺癌患者98例(2018年4月~2019年4月),均行Ki67、HER-2检测,分析HER-2、Ki67阳性率及与乳腺癌患者病理特征(TNM分期)的相关性。结果:乳腺癌Ⅰ、Ⅱ、Ⅲ期Ki67阳性率为57.89%、79.17%、50.00%,HER-2阳性率为55.26%、85.42%、91.67%(P<0.05),Ki67、HER-2与乳腺癌TNM分期均呈正相关(P<0.05)。结论:HER-2、Ki67与乳腺癌患者病理特征有相关性,有助于乳腺癌恶性程度评估。     

Pharmacokinetics of a Mouse/Human Chimeric Monoclonal Antibody (C-17-1 A) in Metastatic Adenocarcinoma Patients

The pharmacokinetic characteristics of a mouse/human chimeric monoclonal antibody (C-17-1A) were determined in 10 patients with metastatic adenocarcinoma following the administration of either 10-mg or 40-mg infusions as a single or multiple dose. The administration of single 10-mg (n = 5) and 40-mg (n = 5) doses infused over 1 hr resulted in mean apparent steady-state distribution volumes of 4.13 ± 0.97 and 5.16 ± 1.92 liters, respectively, indicating that C-17-1A appears to distribute throughout the vascular compartment and into limited extracellular fluid volume. The disposition of C-17-1A was adequately characterized using a two-compartment open model with mean distribution half-lives of 15.8 and 18.5 hr and mean elimination half-lives of 90.0 and 97.6 hr for the 10- and 40-mg groups, respectively. A linear relationship was observed between AUC and dose (µLg/kg). The clearance of C-17-1A was correlated linearly with total Ig, IgG, and tumor size. Multiple administration of either 10-mg (n = 3) or 40-mg (n = 3) doses of C-17-1A infused over 1 hr every 14 days for a total of three doses resulted in superimposable mean serum concentration versus time data and consistent mean pharmacokinetic characteristics. These data indicate that C-17-1A exhibits linear, nonsaturable distribution and elimination characteristics in man over the dose range studied (i.e., 130 to 880 µg/kg). The multiple-dose pharmacokinetics of C-17-1A were predictable, indicating a lack of an antibody response to C-17-1A over a period of 42 days. The clearance of C-17-1A exhibited large interindividual variability with significant correlations to circulating IgG levels and tumor size.     

Constructing a Prediction Interval for Time to Reach a Threshold Concentration Based on a Population Pharmacokinetic Analysis: An Application to Basiliximab in Renal Transplantation

Basiliximab is an immunosuppressant chimeric monoclonal antibody directed to the human interleukin-2 receptor -chain used for prevention of acute rejection episodes in organ transplantation. The minimally effective serum concentration necessary to saturate receptor epitopes in kidney transplant patients is 0.2 g/ml. To guide dose selection for Phase 3 efficacy trials, a population pharmacostatistical model was fitted to intensively sampled Phase 2 pharmacokinetic data. This served as a basis from which to examine candidate dose regimens with respect to the duration over which receptor-saturating concentrations would be achieved posttransplant. Three prediction methods were assessed: one based on simulations, and two others based on first-order approximation using either inverse regression or inversion of confidence intervals. An 80% prediction interval was generated by each method to evaluate its predictive performance against prospectively collected Phase 3 data in 39 renal transplant patients who received two injections of 20mg basiliximab, one prior to surgery and one on Day 4 posttransplant. All methods provided correct prediction of the duration of receptor-saturating concentration. As anticipated, the best performance was obtained from the simulation method which predicted 30 values in the 80% prediction interval, 19.7–52.7 days. The actually observed 80% interval from the Phase 3 data was 23.7–58.3 days.     

Cetuximab: an IgG1 monoclonal antibody for the treatment of epidermal growth factor receptor-expressing tumours

The epidermal growth factor receptor (EGFR) plays an essential role in normal cell growth and differentiation and in the survival of healthy and cancerous cells. EGFR expression is a common feature of non-haematological malignancies and is associated with poor clinical prognosis. Cetuximab is an IgG₁ monoclonal antibody that blocks EGFR activation. It has efficacy alone, and in combination with irinotecan, in the treatment of metastatic colorectal cancer that has progressed on irinotecan-containing therapy. It has been approved for use in combination with irinotecan in both Switzerland and the US and as monotherapy in the US. Cetuximab also has efficacy in cancers of the head and neck and non-small cell lung cancer. Cetuximab is well-tolerated and does not exacerbate the side effects of co-administered cytotoxic chemotherapy.     

三阴乳腺癌患者的临床病理特征及预后情况分析

目的 探讨三阴乳腺癌(triple negative breast cancer,TNBC)患者的临床病理特征及预后情况.方法 选取2009年7月-2011年7月收治的360例乳腺癌患者的病例资料,按免疫组织化学检测结果分为非三阴性乳腺癌(nTNBC)组和TNBC组,每组180例.比较两组的临床病理资料,从而对TNBC组临床病理特征及预后情况进行分析.结果 两组患者的发病年龄、临床分期、肿瘤病灶直径、淋巴结转移和组织学分级比较差异具有统计意义(P＜0.01,P＜0.05).TNBC组局部复发率和远端转移率高于nTNBC组(P＜0.01,P＜0.05).TNBC组无病生存率和总生存率均低于nTNBC组(P＜0.05).结论 TNBC多见于50岁以上的女性,肿瘤分化差、恶性程度高,患者手术预后效果不佳,死亡率较其他类型乳腺癌疾病高.     

EGFR靶向药物个体化治疗转移性结直肠癌的研究进展

靶向表皮生长因子受体(epidermal growth factor receptor,EGFR)单抗目前已成为晚期结直肠癌治疗的一个突破,对此类药物相关基因的研究也开创了结直肠癌个体化治疗的先河。EGFR信号转导系统中EGFR基因、配体以及下游的KRAS,BRAF和PIK3CA基因一直都是研究的热点。本文就EGFR靶向药物疗效相关预测因子的研究现状做一综述。