Seek and destroy: improving PK/PD profiles of anticancer agents with nanoparticles

Introduction: The Pharmacokinetics/pharmacodynamics (PK/PD) relationships with cytotoxics are usually based on a steepening concentration–effect relationship; the greater the drug amount, the greater the effect. The Maximum Tolerated Dose paradigm, finding the balance between efficacy, while keeping toxicities at their manageable level, has been the rule of thumb for the last 50-years. Developing nanodrugs is an appealing strategy to help broaden this therapeutic window. The fact that efficacy and toxicity with cytotoxics are intricately linked is primarily due to the complete lack of specificity toward the tumor tissue during their distribution phase. Because nanoparticles are expected to better target tumor tissue while sparing healthy cells, accumulating large amounts of cytotoxics in tumors could be achieved in a safer way.

Areas covered: This review aims at presenting how nanodrugs present unique features leading to reconsidering PK/PD relationships of anticancer agents.

Expert commentary: The constant interplay between carrier PK, interactions with cancer cells, payload release, payload PK, target expression and target engagement, makes picturing the exact PK/PD relationships of nanodrugs particularly challenging. However, those improved PK/PD relationships now make the once contradictory higher efficacy and lower toxicities requirement an achievable goal in cancer patients.     

药动药效联合模型定量分析方法的研究现状

药动药效联合模型在药理学研究中正在发挥越来越重要的作用。本文介绍了近年来该领域定量计算方面的一些新概念和新进展，包括药动学和药效学模型、药动药效联合模型的四个属性、Sheiner效应室理论应用时应该注意的问题及药动药效联合模型的计算程序等。     

PK/PD参数与抗菌药物的优化用药

反映时间依赖性抗菌药物的PK/PD参数为t>MIC,反映浓度依赖性抗菌药物的PK/PD参数为cmax/MIC或AUC/MIC。时间依赖性与浓度依赖性抗菌药物都与抗菌药物后效应(PAE)和半衰期(t1/2)密切相关。运用PK/PD参数优化抗菌药物的合理用药,叙述了时间依赖性和浓度依赖性抗菌药物及其运用PK/PD参数优化用药的注意点。     

Novel CNS drug discovery and development approach: model-based integration to predict neuro-pharmacokinetics and pharmacodynamics

Introduction: CNS drug development has been hampered by inadequate consideration of CNS pharmacokinetic (PK), pharmacodynamics (PD) and disease complexity (reductionist approach). Improvement is required via integrative model-based approaches.

Areas covered: The authors summarize factors that have played a role in the high attrition rate of CNS compounds. Recent advances in CNS research and drug discovery are presented, especially with regard to assessment of relevant neuro-PK parameters. Suggestions for further improvements are also discussed.

Expert opinion: Understanding time- and condition dependent interrelationships between neuro-PK and neuro-PD processes is key to predictions in different conditions. As a first screen, it is suggested to use in silico/in vitro derived molecular properties of candidate compounds and predict concentration-time profiles of compounds in multiple compartments of the human CNS, using time-course based physiology-based (PB) PK models. Then, for selected compounds, one can include in vitro drug-target binding kinetics to predict target occupancy (TO)-time profiles in humans. This will improve neuro-PD prediction. Furthermore, a pharmaco-omics approach is suggested, providing multilevel and paralleled data on systems processes from individuals in a systems-wide manner. Thus, clinical trials will be better informed, using fewer animals, while also, needing fewer individuals and samples per individual for proof of concept in humans.     

Model-based clinical drug development in the past,present and future: a commentary

Clinical drug development remains a mostly empirical, costly enterprise, in which decision-making is often based on qualitative assessment of risk, without properly leveraging all the relevant data collected throughout the development programme. Model-based drug development (MBDD) has been proposed by regulatory agencies, academia and pharmaceutical companies as a paradigm to modernize drug research through the quantification of risk and combination of information from different sources across time. We present here a historical account of the use of MBDD in clinical drug development, the current challenges and further opportunities for its application in the pharmaceutical industry.     

Pharmacodynamics of piperacillin in severely ill patients evaluated by using a PK/PD model

Penetration of antiinfective drugs into soft tissues is essential for antimicrobial killing at the target site, but is substantially lower in severely ill patients compared with healthy subjects. The present study was conducted to assess the antimicrobial effect of piperacillin in severely ill patients. Strains of Staphylococcus aureus and Pseudomonas aeruginosa were exposed in vitro to concentrations of piperacillin, simulating the pharmacokinetic profiles measured in soft tissue of patients and healthy subjects. The simulation for patients resulted in effective killing, whereas bacterial regrowth was detected for healthy subjects. Our in vitro simulation showed that bacterial killing may be effective in severely ill patients despite relatively low concentrations of piperacillin at the target site. This finding is due to impaired renal function and subsequently prolonged tissue and plasma half-lives of piperacillin in intensive care patients.     

构建沙格列汀PK/PD模型——模拟其在健康人群和肝损伤患者的药动学和药效学

在本次研究中,我们旨在开发和评价沙格列汀的全身生理药代动力学(WB-PBPK)/药效学(PD)模型,模拟其在健康成人及肝功能损害患者中的药代动力学和药效学特性,为特殊患者的临床药学研究提供新方法.基于文献中获取的如logD和血浆蛋白结合率等药物特征参数,建立WB-PBPK模型和PD模型.将模拟所得的血药浓度-时间曲线及...     

高效液相色谱法测定重症患者亚胺培南血药浓度及PK/PD达标率研究

目的：建立高效液相色谱法测定重症患者血浆中亚胺培南浓度,并将接受连续性肾脏替代疗法（continuous renal replacement therapy,CRRT）与未接受该疗法患者的结果进行对比,为临床调整用药提供依据。方法：以0.5 mol·L^-1的3-吗啉丙磺酸缓冲液（pH 6~8）-乙二醇-水（2：1：1）为稳定剂,以5-羟基吲哚-3-乙酸为内标,采用超滤离心管去蛋白法进行前处理,取滤过液进样。色谱柱为TSKgel ODS-100V（4.6 mm×250 mm,5 μm）,流动相为甲醇-10 mmol·L^-1磷酸二氢钾（6：94,磷酸调pH为6.7~7.0）,流速为0.9 mL·min^-1,检测波长为300 nm,柱温为30℃,进样量为30 μL。测定分析33例接受亚胺培南/西司他丁治疗的重症患者的血药谷浓度,CRRT组14例,非CRRT组19例,以100% T>MIC作为PK/PD靶目标计算用药达标率,评估给药方案。结果：亚胺培南在0.5~50 μg·mL^-1内线性关系良好,定量下限为0.5 μg·mL^-1;批内、批间RSD均小于10%;稳定性试验结果表明血浆样品在处理过程中较稳定。当MIC大于2 μg·mL^-1时,达标率显著降低,且接受CRRT治疗患者的达标率低于未接受CRRT治疗患者。结论：该方法前处理过程简单,灵敏准确,分析时间短,适用于临床亚胺培南个体化用药指导。     

Drug discovery and development: lessons from an undeveloped drug

In this article, drug discovery and preclinical development paradigms, as employed in today’s pharmaceutical companies, are discussed. The antimalarial drug, artemisinin, is given as an example of a compound that is unlikely to be developed by a modern pharmaceutical company, yet is a safe and effective drug for the treatment of a deadly disease. It is argued that the use of prespecified charts, listing undesired properties to deselect molecules may lead to missed opportunities in bringing best-in-class medications to patients. Implementation of systems pharmacology, disease progression and pharmacokinetic/pharmacodynamic models are proposed. These models offer a superior approach in selecting the best drug candidates with the highest chance of success of entry into the market.     

Pharmacokinetic/pharmacodynamic integration in drug development and dosage-regimen optimization for veterinary medicine

Pharmacokinetic (PK)/pharmacodynamic (PD) modeling is a scientific tool to help developers select a rational dosage regimen for confirmatory clinical testing. This article describes some of the limitations associated with traditional dose-titration designs (parallel and crossover designs) for determining an appropriate dosage regimen. It also explains how a PK/PD model integrates the PK model (describing the relationship between dose, systemic drug concentrations, and time) with the PD model (describing the relationship between systemic drug concentration and the effect vs time profile) and a statistical model (particularly, the intra- and interindividual variability of PK and/or PD origin). Of equal importance is the utility of these models for promoting rational drug selection on the basis of effectiveness and selectivity. PK/PD modeling can be executed using various approaches, such as direct versus indirect response models and parametric versus nonparametric models. PK/PD concepts can be applied to individual dose optimization. Examples of the application of PK/PD approaches in veterinary drug development are provided, with particular emphasis given to nonsteroidal anti-inflammatory drugs. The limits of PK/PD approaches include the development of appropriate models, the validity of surrogate endpoints, and the acceptance of these models in a regulatory environment.     

Discovery DMPK: changing paradigms in the eighties,nineties and noughties

Background: The science of drug metabolism and pharmacokinetics (DMPK) plays a critical role in supporting the selection of potent, selective leads that retain the appropriate physicochemical properties to ensure distribution from the site of administration into the tissue or target of interest. Historically, Discovery DMPK has bridged the gap between the disciplines of biology and medicinal chemistry thereby ensuring a clinical focus during the discovery and early development phases. Objective: Here we discuss the fundamentals of DMPK screening in drug discovery from a historical perspective, highlighting DMPK's part in improving the chances of success for novel drug candidates and suggesting new and exciting areas for future development. Conclusions: Such a broad remit has resulted in the development of a wide variety of assays, both in vitro and in vivo, focused on assessing the developability risks associated with a molecule's progression into clinical development, such as likely bioavailability in humans, the potential for drug–drug interactions, human metabolism, interactions with transporters and the potential for metabolism-mediated idiosyncratic toxicity. Arguably DMPK has already adopted many of the concepts now of interest in translational medicine and quantitative pharmacology while scientific and regulatory pressures continue to drive the subject towards better and more integrated approaches, such as systems thinking.     

A novel semi-mechanistic tumor growth fraction model for translation of preclinical efficacy of anti-glypican 3 antibody drug conjugate to human

The growing fraction (GF) of tumor has been reported as one of the predictive markers of the efficacy of chemotherapeutics. Therefore, a semi-mechanistic model has been developed that describes tumor growth on the basis of cell cycle, allowing the incorporation of the GF of a tumor in pharmacokinetic/pharmacodynamic (PK/PD) modeling. Efficacy data of anti-glypican 3 (GPC3) antibody drug conjugate (ADC) in a hepatocellular carcinoma (HCC) patient derived xenograft (PDX) model was used for evaluation of this proposed model. Our model was able to describe the kinetics of growth inhibition of HCC PDX models following treatment with anti-GPC3 ADC remarkably well. The estimated tumurostatic concentrations were used in tandem with human PKs translated from cynomolgus monkey for prediction of the efficacious dose. The projected efficacious human dose of anti-GPC3 ADC was in the range 0.20–0.63 mg/kg for the Q3W dosing regimen, with a median dose of 0.50 mg/kg. This publication is the first step in evaluating the applicability of GF in PK/PD modeling of ADCs. The authors are hopeful that incorporation of GF will result in an improved translation of the preclinical efficacy of ADCs to clinical settings and thereby better prediction of the efficacious human dose.     

Pharmacokinetics/pharmacodynamics and the stages of drug development: Role of modeling and simulation

Pharmacokinetic (PK) and pharmacodynamic (PD) modeling and simulation (M&S) are well-recognized powerful tools that enable effective implementation of the learn-and-confirm paradigm in drug development. The impact of PK/PD M&S on decision making and drug development risk management is dependent on the question being asked and on the availability and quality of data accessible at a particular stage of drug development. For instance, M&S methodologies can be used to capture uncertainty and use the expected variability in PK/PD data generated in preclinical species for projection of the plausible range of clinical dose; clinical trial simulation can be used to forecast the probability of achieving a target response in patients based on information obtained in early phases of development. Framing the right question and capturing the key assumptions are critical components of the "learn-and-confirm" paradigm in the drug development process and are essential to delivering high-value PK/PD M&S results. Selected works of PK/PD modeling and simulation from preclinical to phase III are presented as case examples in this article.     

Investigation of Drug Delivery in Rats via Subcutaneous Injection: Case Study of Pharmacokinetic Modeling of Suspension Formulations

With the rising cost of drug research, “do more with less” has become a new emphasis in the pharmaceutical industry. Consequently, the early analysis of pharmacokinetic/pharmacodynamic, efficacy, and safety parameters for a new drug target is critical for ensuring informed decision-making as soon as possible during the drug discovery process. When absorption, distribution, metabolism, and excretion properties of compounds are suboptimal which is especially true during the early stages of drug discovery, obtaining the desired exposure can be challenging via the most common routes (oral, intravenous). Therefore, subcutaneous (SC) injection is often explored as an alternate route of delivery. Although SC injection is used widely in the industry, information about how to model and predict the absorption of drugs administered via SC injection is not readily available. In the current research, we analyzed the absorption behavior of 12 model compounds covering a wide range of physicochemical properties following SC injection. We introduced a compound-specific parameter, the absorption factor from single SC injections of suspension doses of each compound, to aid in modeling and predicting of drug absorption profiles. The pharmacokinetic models derived in this study are capable of describing and predicting the absorption properties of SC injection for individual compounds.     

精准药学:从转化医学到精准医学探讨新药发展

自1960年以来,美国FDA推出的基础研究-发现-设计-临床前开发-临床研究等过程的新药研发的转化研究,这种"转化研究"的"万里挑一"的模式,可以说是最早的"转化研究",对近50年的新药发展起了积极作用。随着生命科学研究的发展及成果的应用,转化研究得到快速发展,转换医学模式成为国际医学健康领域的新概念和研究模式。在美国2010年提出"精准医学"概念之后,奥巴马在他的国情咨文中提出了"精确医学"计划,希望更接近治愈癌症和糖尿病等疾病,希望将以基因为特点的大数据信息用于精准个体化药物治疗。"精准医学"作为医学的未来是人类医学的变革,长期目标是为实现多种疾病的治愈提供有价值的信息。基于精准医疗四要素中"精确、准时、共享、个体化",笔者提出"精准药学"的概念,希望它在实现"精准医疗"中发挥重要的作用,而且具有不同于"精准医学"的研究目标和研究特征。"精准药物"治疗只有实现"精准诊断"的基础上,医疗应用相关的"精准药物"才能提出"精准治疗方案",才能实现精准的个体化治疗。在"大数据"时代,基因组学是精准医学和精准药学的共同基础。但药物研发中可以认为与健康人和病人的基因有关,更与疾病的病因有关,但有些功能性疾病和病毒、细菌、寄生虫等感染性疾病的治疗还与它们的感染、复制及其酶和蛋白等生化过程有关,也与药物的制剂技术和组合有关。因此需要更广阔的知识和视野去认识研发的难度和治疗的精准性,才能开发出疗效更好、更安全、更便利、更经济的新药。     

系统生物学——药物研发的新动力

系统生物学是研究生物系统中所有组成成分以及特定条件下这些组分间相互关系的学科。它以干涉生物活动过程及人工模拟为主要手段，以生物信息为基础，是近年提出的新研究领域，其主要特点是对已有生命科学认识的系统整合。系统生物学的理论与方法以及相关的研究结果将为新药研发以及中医药研究提供新的视角与手段，成为药物研究的新动力。     

Accelerating drug development: methodology to support first‐in‐man pharmacokinetic studies by the use of drug candidate microdosing

Microdosing of experimental therapeutics in humans offers a number of benefits to the drug development process. Microdosing, conducted under an exploratory Investigational New Drug (IND) application, entails administration of a sub‐pharmacological dose of a new chemical entity (NCE) that allows for early evaluation of human pharmacokinetics. Such information can be pivotal for: (1) selecting a compound for full drug development from a small group of candidates; (2) defining the amount of material needed for early development; and (3) setting the initial Phase I dose regimen in humans. Appropriate safety studies must be conducted to support microdosing in humans, but the requirements are generally less extensive than those needed to support a traditional IND. To date, microdosing has not been broadly applied by the pharmaceutical industry due to concerns about analytical sensitivity and the possibility of non‐linear pharmacokinetics at extremely low doses. The primary method for detecting analytes following microdosing until now has been accelerator mass spectrometry, which is expensive, not generally available, and requires test agents to be radiolabeled. Presented in this report is an example of pharmacokinetics analysis using LC/MS/MS following microdosing of an experimental agent in cynomolgus monkeys. The results show good linearity in plasma pharmacokinetics for oral doses of 10 mg/kg (therapeutic dose) and 0.0005 mg/kg (microdose) of the test agent. The results also demonstrate the feasibility of applying standard laboratory analytics to support microdosing in humans and raise the possibility of establishing an animal model to screen for compounds having non‐linear pharmacokinetics at low dose levels. Drug Dev. Res. 68:14–22, 2007. © 2007 Wiley‐Liss, Inc.     

The teaching of drug development to medical students: collaboration between the pharmaceutical industry and medical school

Collaboration between the medical school at Leicester and a local pharmaceutical company, AstraZeneca, led to the design and implementation of an optional third year special science skills module teaching medical students about drug discovery and development. The module includes didactic teaching about the complexities of the drug discovery process leading to development of candidate drugs for clinical investigation as well as practical experience of the processes involved in drug evaluation preclinically and clinically. It highlights the major ethical and regulatory issues concerned with the production and testing of novel therapies in industry and the NHS. In addition it helps to reinforce other areas of the medical school curriculum, particularly the understanding of clinical study design and critical appraisal. The module is assessed on the basis of a written dissertation and the critical appraisal of a drug advertisement. This paper describes the objectives of the module and its content. In addition we outline the results of an initial student evaluation of the module and an assessment of its impact on student knowledge and the opinion of the pharmaceutical industry partner. This module has proven to be popular with medical students, who acquire a greater understanding of the work required for drug development and therefore reflect more favourably on the role of pharmaceutical companies in the UK.     

Current status and future perspective on preclinical pharmacokinetic and pharmacodynamic (PK/PD) analysis: Survey in Japan pharmaceutical manufacturers association (JPMA)

Preclinical pharmacokinetic/pharmacodynamic (PK/PD) analysis is an efficient tool for the translational research and proof of mechanism/concept in animals. The questionnaire survey on the practice of preclinical PK/PD analysis was conducted in the member companies of the Japan Pharmaceutical Manufacturers Association (JPMA). According to the survey, 60% of companies conducted preclinical PK/PD analysis and its impact for drug development was different between each of the companies. The frequently analyzed therapeutic areas of preclinical PK/PD analysis were neurology, inflammation and metabolic disease, and those are different from the therapeutic area (infectious disease and oncology) in which PK/PD analysis was considered as effective by the present survey. Many companies which have used preclinical PK/PD analysis for the translation to human PK/PD and for the prediction of dose/regimen had good communication with other research & development (R&D) departments (e.g. pharmacology/clinical pharmacology). The increase in resources for preclinical PK/PD analysis including education was highly demanded. As a future perspective, the closer collaboration between pharmacokinetics scientists, pharmacologists, toxicologists and clinical pharmacologists and the increase in resources including upskilling and the comprehension of preclinical PK/PD analysis by the project team are considered to lead to efficient contributions to improve the success ratio of drug discovery and development.