FDA“抗体偶联药物的考虑”供企业用的指导原则草案介绍

美国食品药品监督管理局（FDA）于2022年2月发布了“抗体偶联药物的考虑”供企业用的指导原则草案,旨在帮助企业和其他参与者开发细胞毒性小分子药物（有效载荷）的抗体偶联药物（ADC）。该指导原则阐述了FDA目前对ADC临床药理学开发方案的建议,包括生物分析方法、给药方案、剂量和暴露反应分析、内在因素、QTc评估、免疫原性和药物-药物相互作用。ADC主要用于治疗肿瘤,又是当前国内药物研发的热点。中国目前还没有类似的指导原则,详细介绍FDA的该指导原则,期望有助于国内对这类新药的研发与监管。     

抗体偶联药物及其体内外代谢的研究进展

抗体偶联药物（ADC）是由单克隆抗体和细胞毒性有效载荷通过连接子偶联而成,结合了单克隆抗体的高特异性靶向能力和细胞毒活性小分子高效杀伤作用的优点,实现了对癌细胞的精准高效清除,已成为抗癌药物研发的热点之一。自2000年美国食品药品监督管理局（FDA）批准第一个ADC药物吉妥珠单抗（Mylotarg）以来,迄今全球已有14个ADC药物获批上市。这类新型的抗癌药物正引领癌症靶向治疗的新时代。基于ADC药物的构建核心和抗肿瘤作用机制,对ADC药物的体内外代谢的研究进展进行综述,以期从代谢角度为ADC药物的设计、开发、临床前药理、毒理及后续研究提供参考。     

抗体偶联药物研究进展

靶向治疗已成为肿瘤治疗新趋势。抗肿瘤靶向药物与传统的细胞毒性化疗药物相比具有特异性高、选择性强和非细胞毒性等优点,抗体偶联药物（ ADC）属于抗肿瘤靶向药物,由抗体、“弹头”药物（细胞毒性药物）通过链分子连接而成。 ADC 将抗体的靶向性与细胞毒性药物的抗肿瘤作用相结合,可以降低细胞毒性抗肿瘤药物的不良反应,提高肿瘤治疗的选择性,还能更好地应对靶向单抗的耐药性问题。     

曲妥珠单抗-药物共轭物(T-DM1)临床前药物代谢动力学研究及人体药物代谢动力学预测

本试验通过临床前药物代谢动力学(PK)和毒理学研究结果,对曲妥珠单抗-药物共轭物(T-DM1)的人体PK特性进行了预测,并探讨了目前广泛采用的预测方法的不足和可能的解决途径。本试验首先进行了动物试验,包括大鼠急性毒性试验和食蟹猴PK试验,通过试验获得了T-DM1的总抗体、偶联抗体和游离小分子药物emtansine(DM1)的PK参数,随后基于这些参数,使用异速增长模型和种属-时间不变法,对总抗体和偶联抗体的人体PK特性进行了预测。此外,通过参考近年的一些相关研究,探讨了如何基于动物生理药动学(PBPK)模型,更科学地预测抗体偶联药物中小分子药物的人体PK和分布特性。     

治疗性蛋白药物的药动学和药效学评价

治疗性蛋白药物是一类用于治疗的高分子物质(>1kDa)可分为多肽和基因工程药物、单克隆抗体和基因工程抗体、重组疫苗等。与小分子药物相比,其具有高活性、特异性强、低毒性、生物功能明确、有利于临床应用的特点。由于其成本低、成功率高、安全可靠,故已成为医药产品中的重要组成部分。同时,由于该类药物为外源性蛋白,具有稳定性不高、分子量大以及物理化学性质与小分子药物不同等特点,其药动学和药效学研究面临许多困难。本文从药动学和药效学两个方面,综述治疗性蛋白药物的影响因素和研究方法。1治疗性蛋白药物的药动学1.1吸收由于蛋白质…     

抗体偶联药物临床前安全性评价考虑要点

抗体偶联药物（Antibody Drug Conjugate,ADC）,是通过连接子将高细胞毒性化合物连接到靶向肿瘤抗原的抗体上,利用抗体靶向识别将化合物递呈至肿瘤细胞表面,杀死肿瘤细胞。ADC药物同时具有抗体和化学药物属性,是将两者的优势结合,极大地提高了药物安全有效性。ADC药物结构复杂,在抗原识别表位、连接位点、连接子以及小分子药物各组分均存在特异性,所以在开展安全性评价研究时有一定的特殊性。本文将从动物种属选择、一般毒性研究、毒代动力学研究、组织交叉反应、免疫原性检测、安全药理研究、遗传毒性研究等方面,阐述ADC药物临床前安全性评价的考虑要点和研究策略。     

抗体偶联药物的分子特点及其药代动力学研究考虑

随着我国药物研发和临床试验水平的不断提高,近年来抗体偶联药物(Antibody-Drug Conjugate, ADC)的相关研究和注册申报也正在增多。ADC类药物由抗体、连接子和小分子毒素组成,在兼具高度靶向性和高细胞毒性优势的同时,由于其结构的多样性和复杂性,以及循环系统中释放的小分子毒素含量较低等特殊性,给其药代动力学研究带来了诸多挑战。本文将从ADC药物的分子设计、药代动力学特征和目标分析物等方面讨论,以期帮助读者更好的理解ADC药物的药代动力学研究。     

抗体偶联药物分析方法的概述及进展北大核心CSCD

单克隆抗体药物的靶点选择性非常高,但其药理活性普遍比较低。近年来抗体偶联药物(antibody-drug conjugate,ADC)的出现,正好弥补了单克隆抗体药物的缺点。ADC是一类通过化学偶联子将单克隆抗体和不同数目的小分子细胞毒素(效应分子)偶联起来的药物。这种新型的药物结合了单克隆抗体的高特异性和小分子毒素的高活性。ADC药物的分析工作非常困难和费时,主要归因于分析物的多样性及分析方法的复杂性。本文将对目前在ADC药物研究的不同方面如理化性质表征、药代动力学和药效学研究、以及免疫原性评价等所用的分析方法做出归纳和阐述,并讨论这些方法所面临的困难和挑战。     

抗肿瘤抗体偶联药物临床药理学研究的若干问题与考虑

抗体偶联药物(antibody-drug conjugates, ADC)由靶向特异性抗原的抗体药物与有效载荷(如小分子细胞毒药物)通过连接子偶联而成，兼具传统小分子细胞毒药物的强大杀伤效应和抗体药物的肿瘤靶向性。截至2022年2月，美国食品药品监督管理局(FDA)已批准12个ADC抗肿瘤药物。本文通过分析已批准ADC药物的临床药理学审评报告结合相关指导原则，梳理ADC药物临床药理学的研究要点，发现在ADC药物研发中，除临床药理学方面的常规研究外，由于ADC特殊的抗肿瘤作用机制，其剂量选择以及特殊人群用药有着特殊的考虑。希望本文对国内研发人员在开发ADC药物时有所启示。     

一种药动学一药效学相关性分析新方法:人工神经网络法

对生物活性物质的药动学（PK）一药效学（PD）相关性进行统计分析，可获得药物的一般测量值（如血浆浓度）与药理效能之间的明确关系。这在新药筛选、药品开发以及剂型优化等方面极为重要。常用的PK－PD模拟分析方法有连接模型法（linkmodel）和间接响应模型法（Indirectresponsemodel）等。这些模拟方法有许多局限性，如必须知道药物作用机理等信息，而人工神经网络（ANNS）模拟方法在模拟PK－PK相关性时能克服这些缺陷。ANNS分析方法是一类仿生物神经网络原理的信息处理系统，与传统的信息处理方法不同。ANNS具有并行性、容错性…     

Factors influencing the choice of monoclonal antibodies for antibody–drug conjugates

In antibody–drug conjugates (ADCs), monoclonal antibodies (mAbs) act as carriers for a cytotoxic payload providing the therapy with targeted action against cells expressing a target cell surface antigen. An appropriate choice of mAb is crucial to developing a successful ADC for clinical development. However, problems such as immunogenicity, poor pharmacokinetic (PK) and pharmacodynamic (PD) profiles and variable drug–antibody ratios (DARs) plague ADCs. In this review, we detail recent mAb-based innovations and factors that should be considered to overcome these problems to achieve a new generation of more effective ADC therapeutics.     

The Properties of Cysteine-Conjugated Antibody-Drug Conjugates Are Impacted by the IgG Subclass

Among the numerous antibody-drug conjugate (ADC) clinical candidates, one of the most prevalent types utilizes the interchain cysteines in antibodies to conjugate auristatin via a maleimide-containing linker. In this class of ADCs, there are a paucity of systematic studies characterizing how IgG subclass influences the biophysical properties and in vivo pharmacokinetics of the ADC molecules. In the current investigation, we studied cysteine-conjugated ADCs using a model system consisting of human IgG1, IgG2, and IgG4 antibodies with the same variable region. Our findings identified some unforeseen differences among the three ADCs. Drug conjugation profiling by LC-MS revealed that 50% of inter heavy-light chain disulfide bonds are disrupted to conjugate drugs in IgG1 antibody while only 10% in IgG2 antibody and 20% in IgG4 antibody. The solution behavior of the ADCs was interrogated in concentrating experiments and diffusion interaction parameter measurements. We found that drug conjugation affected the solution property of the three antibodies differently, with the IgG2-based ADC having the most increased propensity to aggregate. Rat PK studies using a sensitive LC-MS-based bioanalytical method showed that the IgG1-based ADC has poor peripheral linker-payload stability while the IgG2- and IgG4-based ADCs are stable. The conjugate stability of the IgG2-based ADC was further confirmed in a cynomolgus monkey PK study. Overall, the IgG2-based ADC exhibited the best PK/conjugate stability but also the most deterioration in stability among the three ADCs. Our findings provide important information and present multifactorial considerations for the selection of IgG subclass during ADC drug discovery when employing stochastic cysteine conjugation.     

Effect of Conjugation Site and Technique on the Stability and Pharmacokinetics of Antibody-Drug Conjugates

Appropriate selection of conjugation sites and conjugation technologies is now widely accepted as crucial for the success of antibody-drug conjugates (ADCs). Herein, we present ADCs conjugated by different conjugation methods to different conjugation positions being systematically characterized by multiple in vitro assays as well as in vivo pharmacokinetic (PK) analyses in transgenic Tg276 mice. Conjugation to cysteines, genetically introduced at positions N325, L328, S239, D265, and S442, was compared to enzymatic conjugation via microbial transglutaminase (mTG) either to C-terminal light (LC) or heavy chain (HC) recognition motifs or to endogenous position Q295 of a native antibody. All conjugations yielded homogeneous DAR 2 ADCs with similar hydrophobicity, thermal stability, human neonatal Fc receptor (huFcRn) binding, and serum stability properties, but with pronounced differences in their PK profiles. mTG-conjugated ADC variants conjugated either to Q295 or to LC recognition motifs showed superior PK behavior. Within the panel of engineered cysteine variants L328 showed a similar PK profile compared to previously described S239 but superior PK compared to S442, D265, and N325. While all positions were first tested with trastuzumab, L328 and mTG LC were further evaluated with additional antibody scaffolds derived from clinically evaluated monoclonal antibodies (mAb). Based on PK analyses, this study confirms the newly described position L328 as favorable site for cysteine conjugation, comparable to the well-established engineered cysteine position S239, and emphasizes the favorable position Q295 of native antibodies and the tagged LC antibody variant for enzymatic conjugations via mTG. In addition, hemizygous Tg276 mice are evaluated as an adequate model for ADC pharmacokinetics, facilitating the selection of suitable ADC candidates early in the drug discovery process.     

Immunogenicity of Antibody Drug Conjugates: Bioanalytical Methods and Monitoring Strategy for a Novel Therapeutic Modality

Immunogenicity (the development of an adaptive immune response reactive with a therapeutic) is a well-described but unwanted facet of biotherapeutic development. There are commonly applied procedures for immunogenicity risk assessment, testing strategies, and bioanalysis. With some modifications, these can be applied to new biotherapeutic modalities. For novel therapies such as antibody-drug conjugates (ADCs), the unique structural components may contribute additional complexities to both immunologic responses and bioanalytical methods. US product inserts (USPIs) for two commercially available ADCs detail the incidence of immunogenicity; however, the body of literature on immunogenicity of ADCs is limited. We recently participated in a conference session on this topic (Annual meeting of the American Association of Pharmaceutical Scientists, held November 2013 in San Antonio, TX, USA. The meeting featured the Symposium: Immunogenicity Assessment for Novel Antibody Drug Conjugates, Nonclinical to Clinical) which prompted an effort to share our perspectives on how immunogenicity risk assessment, testing strategies, and bioanalytical methods can be adapted to reflect the complexity of ADC therapeutics.KEY WORDS: antibody-drug conjugate (ADC), antidrug antibodies (ADA), bioanalytical, immunogenicity, oncology     

Impact of Shed/Soluble targets on the PK/PD of approved therapeutic monoclonal antibodies

Introduction: Suboptimal treatment for monoclonal antibodies (mAbs) directed against endogenous circulating soluble targets and the shed extracellular domains (ECD) of the membrane-bound targets is an important clinical concern due to the potential impact of mAbs on the in vivo efficacy and safety. Consequently, there are considerable challenges in the determination of an optimal dose and/or dosing regimen.

Areas covered: This review outlines the impact of shed antigen targets from membrane-bound proteins and soluble targets on the PK and/or PD of therapeutic mAbs that have been approved in the last decade. We discuss various bioanalytical techniques that have facilitated the interpretation of the PK/PD properties of therapeutic mAbs and also considered the factors that may impact such measurements. Quantitative approaches include target-mediated PK models and bi- or tri-molecular interaction PK/PD models that describe the relationships between the antibody PK and the ensuing effects on PD biomarkers, to facilitate the mAb PK/PD characterization.

Expert commentary: The proper interpretation of PK/PD relationships through the integrated PK/PD modeling and bioanalytical strategy facilitates a mechanistic understanding of the disease processes and dosing regimen optimization, thereby offering insights into developing effective therapeutic regimens. This review provides an overview of the impact of soluble targets or shed ECD on mAb PK/PD properties. We provide examples of quantitative approaches that facilitate the characterization of mAb PK/PD characteristics and their corresponding bioanalytical strategies.     

抗体偶联药物研究进展

抗体偶联药物(antibody drug conjugates,ADCs)是通过化学键将毒性小分子与单克隆抗体偶联的靶向抗肿瘤药物,其充分利用了抗体的特异性和毒性小分子的高抗肿瘤活性,达到了高效低毒的目的。抗体、连接物以及毒性小分子是ADCs的3个重要组成部分,文章介绍了ADCs制备中靶点选择,抗体小型化和人源化改造,高活性毒性小分子使用,可断开和不可断开连接物的特点以及越来越受关注的定点偶联策略,为ADCs临床前研发提供依据。     

Antibody Drug Conjugates: Nonclinical Safety Considerations

Antibody drug conjugates (ADCs) are biopharmaceutical molecules consisting of a cytotoxic small molecule covalently linked to a targeted protein carrier via a stable cleavable or noncleavable linker. The process of conjugation yields a highly complex molecule with biochemical properties that are distinct from those of the unconjugated components. The impact of these biochemical differences on the safety and pharmacokinetic (PK) profile of the conjugate must be considered when determining the types of nonclinical safety studies required to support clinical development of ADCs. The hybrid nature of ADCs highlights the need for a science-based approach to safety assessment that incorporates relevant aspects of small and large molecule testing paradigms. This thinking is reflected in current regulatory guidelines, where sections pertaining to conjugates allow for a flexible approach to nonclinical safety testing. The aim of this article is to review regulatory expectations regarding early assessment of nonclinical safety considerations and discuss how recent advances in our understanding of ADC-mediated toxicity can be used to guide the types of nonclinical safety studies needed to support ADC clinical development. The review will also explore nonclinical testing strategies that can be used to streamline ADC development by assessing the safety and efficacy of next generation ADC constructs using a rodent screen approach.KEY WORDS: antibody drug conjugates, regulatory guidance, safety assessment, therapeutic index     

Development and Translational Application of an Integrated,Mechanistic Model of Antibody-Drug Conjugate Pharmacokinetics

Antibody drug conjugates (ADC), in which small molecule cytotoxic agents are non-specifically linked to antibodies, can enable targeted delivery of chemotherapeutics to tumor cells. ADCs are often produced and administered as a mixture of conjugated antibodies with different drug to antibody ratios (DAR) resulting in complex and heterogeneous disposition kinetics. We developed a mechanism-based platform model that can describe and predict the complex pharmacokinetic (PK) behavior of ADCs with protease-cleavable valine-citrulline (VC) linker linked to Monomethylmonomethyl auristatin F/E by incorporating known mechanisms of ADC disposition. The model includes explicit representation of all DAR species; DAR-dependent sequential deconjugation of the drug, resulting in the conversion of higher DAR to lower DAR species; and DAR-dependent antibody/ADC clearance. PK profiles of multiple analytes (total antibody, drug-conjugated antibody, and/or antibody-conjugated drug) for different ADC molecules and targets in rodents and cynomolgus monkeys were used for model development. The integrated cross-species model was successful in capturing the multi-analyte PK profiles after administration of purified ADCs with defined DAR species and ADCs with mixtures of DAR. Human PK predictions for DSTP3086S (anti-STEAP1-vc-MMAE) with the platform model agreed well with PK (total antibody and antibody-conjugated drug concentrations) measurements in the dose-ranging phase I clinical study. The integrated model is applicable to various other ADCs with different formats, conjugated drugs, and linkers, and provides a valuable tool for the exploration of mechanisms governing disposition of ADCs and enables translational predictions.     

Bench to bedside translation of antibody drug conjugates using a multiscale mechanistic PK/PD model: a case study with brentuximab-vedotin

To build a multiscale mechanism based pharmacokinetic?Cpharmacodynamic (PK/PD) model for antibody drug conjugates (ADCs), using brentuximab-vedotin as an example, for preclinical to clinical translation of ADC efficacy. Brentuximab-vedotin experimental data, collected from diverse publications, were employed in the following steps to build and validate the model: (1) characterization of ADC and payload PK at the cellular level, (2) characterization of payload PK in plasma and tumor tissue of xenograft mouse, (3) characterization of ADC PK in mouse plasma, (4) prediction of the tumor payload concentrations in xenograft mouse by integrating parameters obtained from steps 1?C3 with the novel tumor disposition model for ADC, (5) characterization of preclinical brentuximab-vedotin tumor growth inhibition data using the novel PK/PD model, (6) characterization of ADC and payload PK in cancer patients, and (7) prediction of clinical responses of brentuximab-vedotin using the PK/PD model, by integrating PK parameters obtained from step 6, and translated mouse parameters from step 5; and comparing them with clinical trial results. The tumor disposition model was able to accurately predict xenograft tumor and plasma payload concentrations. PK/PD model predicted progression free survival rates and complete response rates for brentuximab-vedotin in patients were comparable to the observed clinical results. It is essential to understand and characterize the disposition of ADC and payload, at the cellular and physiological level, to predict the clinical outcome of ADC. A first of its kind mechanistic model has been developed for ADCs, which can integrate preclinical biomeasures and PK/PD data, to predict clinical response.     

Antibody Drug Conjugates: Design and Selection of Linker,Payload and Conjugation Chemistry

Antibody drug conjugates (ADCs) have emerged as an important pharmaceutical class of drugs designed to harness the specificity of antibodies with the potency of small molecule therapeutics. The three main components of ADCs are the antibody, the linker, and the payload; the majority of early work focused intensely on improving the functionality of these pieces. Recently, considerable attention has been focused on developing methods to control the site and number of linker/drug conjugated to the antibody, with the aim of producing more homogenous ADCs. In this article, we review popular conjugation methods and highlight recent approaches including “click” conjugation and enzymatic ligation. We discuss current linker technology, contrasting the characteristics of cleavable and non-cleavable linkers, and summarize the essential properties of ADC payload, centering on chemotherapeutics. In addition, we report on the progress in characterizing to determine physicochemical properties and on advances in purifying to obtain homogenous products. Establishing a set of selection and analytical criteria will facilitate the translation of novel ADCs and ensure the production of effective biosimilars.KEY WORDS: ADC, antibody drug conjugate, biopharmaceutics, enzymatic ligation, therapeuticsAntibody drug conjugates (ADCs) couple the highly desirable pharmacokinetic (PK) profile and targetability of monoclonal antibodies (mAbs) with the potent cytotoxicity of small molecule drugs. Such a combination can potentially minimize dose-limiting toxicities while maximizing desired therapeutic effects. Yet, initial ADCs pairing standard anti-cancer agents, such as doxorubicin, were ineffective in clinical trials (1). These failures were linked to (1) the limited number of drug molecules that can be conjugated to one antibody without affecting antigen binding and (2) the limited number of antigens on target cell surfaces, preventing therapeutic levels of drug accumulation in cells. To date, the most successful approaches to overcome these challenges are improved linker technology and the selection of extremely potent drugs to the pair with the antibody (e.g., ado-trastuzumab emtansine and brentuximab vedotin) (2,3). Innovations in linker design are focused on multiple issues ranging from serum stability to mechanism of release to drug to antibody ratio (DAR). As linkers become increasingly sophisticated, more emphasis is being placed on the methods of bioconjugation between linker and antibody, with the goal of producing homogeneous ADC populations. Several methods of characterization are now employed to assess the composition of such conjugates and to increase our understanding of correlations between ADC structure and efficacy. These many facets of ADC synthesis will be addressed in this review.