Incorporation of FcRn-mediated disposition model to describe the population pharmacokinetics of therapeutic monoclonal IgG antibody in clinical patients

Effect of Obesity on the Pharmacokinetics and Pharmacodynamics of Anticancer Agents

An objective of the Precision Medicine Initiative, launched in 2015 by the US Food and Drug Administration and National Institutes of Health, is to optimize and individualize dosing of drugs, especially anticancer agents, with high pharmacokinetic and pharmacodynamic variability. The American Society of Clinical Oncology recently reported that 40% of obese patients receive insufficient chemotherapy doses and exposures, which may lead to reduced efficacy, and recommended pharmacokinetic studies to guide appropriate dosing in these patients. These issues will only increase in importance as the incidence of obesity in the population increases. This publication reviews the effects of obesity on (1) tumor biology, development of cancer, and antitumor response; (2) pharmacokinetics and pharmacodynamics of small-molecule anticancer drugs; and (3) pharmacokinetics and pharmacodynamics of complex anticancer drugs, such as carrier-mediated agents and biologics. These topics are not only important from a scientific research perspective but also from a drug development and regulator perspective. Thus, it is important to evaluate the effects of obesity on the pharmacokinetics and pharmacodynamics of anticancer agents in all categories of body habitus and especially in patients who are obese and morbidly obese. As the effects of obesity on the pharmacokinetics and pharmacodynamics of anticancer agents may be highly variable across drug types, the optimal dosing metric and algorithm for difference classes of drugs may be widely different. Thus, studies are needed to evaluate current and novel metrics and methods for measuring body habitus as related to optimizing the dose and reducing pharmacokinetic and pharmacodynamic variability of anticancer agents in patients who are obese and morbidly obese.

Importance and Considerations of Antibody Engineering in Antibody-Drug Conjugates Development from a Clinical Pharmacologist's Perspective

Antibody-drug conjugates (ADCs) appear to be in a developmental boom, with five FDA approvals in the last two years and a projected market value of over $4 billion by 2024. Major advancements in the engineering of these novel cytotoxic drug carriers have provided a few early success stories. Although the use of these immunoconjugate agents are still in their infancy, valuable lessons in the engineering of these agents have been learned from both preclinical and clinical failures. It is essential to appreciate how the various mechanisms used to engineer changes in ADCs can alter the complex pharmacology of these agents and allow the ADCs to navigate the modern-day therapeutic challenges within oncology. This review provides a global overview of ADC characteristics which can be engineered to alter the interaction with the immune system, pharmacokinetic and pharmacodynamic profiles, and therapeutic index of ADCs. In addition, this review will highlight some of the engineering approaches being explored in the creation of the next generation of ADCs.

Pharmacologic Considerations in the Disposition of Antibodies and Antibody-Drug Conjugates in Preclinical Models and in Patients

The rapid advancement in the development of therapeutic proteins, including monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs), has created a novel mechanism to selectively deliver highly potent cytotoxic agents in the treatment of cancer. These agents provide numerous benefits compared to traditional small molecule drugs, though their clinical use still requires optimization. The pharmacology of mAbs/ADCs is complex and because ADCs are comprised of multiple components, individual agent characteristics and patient variables can affect their disposition. To further improve the clinical use and rational development of these agents, it is imperative to comprehend the complex mechanisms employed by antibody-based agents in traversing numerous biological barriers and how agent/patient factors affect tumor delivery, toxicities, efficacy, and ultimately, biodistribution. This review provides an updated summary of factors known to affect the disposition of mAbs/ADCs in development and in clinical use, as well as how these factors should be considered in the selection and design of preclinical studies of ADC agents in development.

Minimal physiologically-based pharmacokinetic model to investigate the effect of pH dependent FcRn affinity and the endothelial endocytosis on the pharmacokinetics of anti-VEGF humanized IgG1 antibody in cynomolgus monkey

In this study, we developed a first minimal physiologically-based pharmacokinetic (mPBPK) model to investigate the complex interaction effects of endocytosis rate/FcRn binding affinity at both acidic/physiological pH on the pharmacokinetics (PK) of the anti-VEGF IgG₁ antibodies. The data used in this study were the PK of the native IgG and humanized anti-VEGF IgG₁ antibodies with a wide range FcRn-binding at both acidic and physiological pH in the cynomolgus monkey. The basic structure of the developed mPBPK models consisted of plasma, tissue and lymph compartments. The tissue compartment was subdivided into vascular, endothelial and interstitial spaces. Non-equilibrium binding mechanism was used to describe the FcRn-IgG interaction in the endosome. The fittings in the final model with three pH systems in the endosome compartment showed a good fit based on the visualization of the fitted graphs and the coefficient of variations of the estimated parameters (CV < 50%). The quantitative endocytosis/FcRn binding affinity PK relationships was constructed using the final model to provide better understanding of complex interaction effects of endocytosis rate and FcRn binding on PK of anti-VEGF IgG₁ antibodies. This result may serve as an important model-based drug discovery platform to guide the design and development of the future generation of anti-VEGF IgG₁ or other therapeutic IgG₁ antibodies. In addition, the mPBPK model developed in cynomolgus monkey was successfully used to predict the PK of the anti-VEGF IgG₁ antibody (bevacizumab) in human subjects.

Effects of the FcRn developmental pharmacology on the pharmacokinetics of therapeutic monoclonal IgG antibody in pediatric subjects using minimal physiologically-based pharmacokinetic modelling

The aim of this study was to investigate neonatal Fc receptor (FcRn) concentration developmental pharmacology in adult and pediatric subjects using minimal physiologically-based pharmacokinetic (mPBPK) modelling. Three types of pharmacokinetic (PK) data for three agents (endogenous/exogenous native IgG, bevacizumab and palivizumab) were used. The adult group contained six subjects with weights from 50 to 100 kg. For pediatric subjects, seven age groups were assumed, with five subjects each having the weight of 95%, 75%, 50%, 25% and 5% percentile of the population. A first evidence-based rating system to evaluate the quality of the source data used to derive pediatric-specific mPBPK model parameter was proposed. A stepwise approach was used to examine the best combination of age/weight effect on the parameters of the mPBPK model in adult and pediatric subjects. IgG synthesis rate (K_syn), extravasation rate (ER) and FcRn were fitted simultaneously to the PK of bevacizumab and native-IgG in both adult and pediatric. All fitting showed good fits based on the graphs and the coefficient of variation of the fitted parameters (< 50%). Estimated weight-normalized K_syn increased while weight-normalized FcRn and ER decreased with increasing age. The age and weight effect on FcRn were successfully estimated from the data. The final mPBPK model developed with native IgG and bevacizumab was able to predict the PK of palivizumab in pediatric subjects. Implementation of the mPBPK model enables us to analyze the relationships of age, weight, FcRn, ER and K_syn in both adult and pediatric subject. This information may benefit the understanding of complex interaction between the FcRn developmental pharmacology and PK parameters, and improve the prediction of the antibody disposition in pediatric subjects.

Factors Affecting the Pharmacology of Antibody-Drug Conjugates

Major advances in therapeutic proteins, including antibody-drug conjugates (ADCs), have created revolutionary drug delivery systems in cancer over the past decade. While these immunoconjugate agents provide several advantages compared to their small-molecule counterparts, their clinical use is still in its infancy. The considerations in their development and clinical use are complex, and consist of multiple components and variables that can affect the pharmacologic characteristics. It is critical to understand the mechanisms employed by ADCs in navigating biological barriers and how these factors affect their biodistribution, delivery to tumors, efficacy, and toxicity. Thus, future studies are warranted to better understand the complex pharmacology and interaction between ADC carriers and biological systems, such as the mononuclear phagocyte system (MPS) and tumor microenvironment. This review provides an overview of factors that affect the pharmacologic profiles of ADC therapies that are currently in clinical use and development.