Suhasini Iyer

Projecting human pharmacokinetics of therapeutic antibodies from nonclinical data: What have we learned?

The pharmacokinetics (PK) of therapeutic antibodies is determined by target and non-target mediated mechanisms. These antibody-specific factors need to be considered during prediction of human PK based upon preclinical information. Principles of allometric scaling established for small molecules using data from multiple animal species cannot be directly applied to antibodies. Here, different methods for projecting human clearance (CL) from animal PK data for 13 therapeutic monoclonal antibodies (mAbs) exhibiting linear PK over the tested dose ranges were examined: simple allometric scaling (CL versus body weight), allometric scaling with correction factors, allometric scaling based on rule of exponent and scaling from only cynomolgus monkey PK data. A better correlation was obtained between the observed human CL and the estimated human CL based on cynomolgus monkey PK data and an allometric scaling exponent of 0.85 for CL than other scaling approaches. Human concentration-time profiles were also reasonably predicted from the cynomolgus monkey data using species-invariant time method with a fixed exponent of 0.85 for CL and 1.0 for volume of distribution. In conclusion, we expanded our previous work and others and further confirmed that PK from cynomolgus monkey alone can be successfully scaled to project human PK profiles within linear range using simplify allometry and Dedrick plots with fixed exponent.

Pharmacokinetics of Humanized Monoclonal Anti-Tumor Necrosis Factor-α Antibody and Its Neonatal Fc Receptor Variants in Mice and Cynomolgus Monkeys

The neonatal Fc receptor (FcRn) plays a critical role in maintaining homeostasis of IgG antibodies. Recent studies have shown that the FcRn-IgG interaction can be modulated to alter the pharmacokinetics of the antibody. This has been achieved by altering amino acid residues in the FcRn-binding domain of the antibody, resulting in a change in the pH-dependent binding affinity of the antibody to FcRn. The purpose of this study was to examine the impact of the pH-dependent FcRn binding affinity on the pharmacokinetics of the antibody with changes in the Asn434 residue. Two anti-tumor necrosis factor-α monoclonal antibody (mAb) FcRn variants (N434A and N434H) were engineered, and pharmacokinetic studies of the two FcRn variants together with the wild type (WT) were conducted in mice and cynomolgus monkeys. N434A, which had binding properties to murine FcRn similar to those of the WT, had the same pharmacokinetic profile as the WT in mice. N434H, with the highest binding affinity to murine FcRn at pH 7.4, had a faster clearance (16.1 ml/day/kg) and a lower bioavailability (61.3%) compared with the WT (5.07 ml/day/kg, 73.2%) and N434A (5.90 ml/day/kg, 72.4%) in mice. N434A and N434H, which had higher binding affinity at pH 6.0 to monkey FcRn with comparable affinity at pH 7.4, had significantly higher areas under the serum concentration-time curve from time 0 to day 7 than the WT (749 ± 71.9 and 819 ± 81.5 versus 592 ± 56.8 μg/ml · day) in monkeys. Thus, increasing the binding affinity of mAbs to FcRn at pH 6.0 while keeping a low binding affinity at pH 7.4 improves the pharmacokinetics of these molecules.

Development of a two-part strategy to identify a therapeutic human bispecific antibody that inhibits IgE receptor signaling

The development of bispecific antibodies as therapeutic agents for human diseases has great clinical potential, but broad application has been hindered by the difficulty of identifying bispecific antibody formats that exhibit favorable pharmacokinetic properties and ease of large-scale manufacturing. Previously, the development of an antibody technology utilizing heavy chain knobs-into-holes mutations and a single common light chain enabled the small-scale generation of human full-length bispecific antibodies. Here we have extended the technology by developing a two-part bispecific antibody discovery strategy that facilitates proof-of-concept studies and clinical candidate antibody generation. Our scheme consists of the efficient small-scale generation of bispecific antibodies lacking a common light chain and the hinge disulfides for proof-of-concept studies coupled with the identification of a common light chain bispecific antibody for large-scale production with high purity and yield. We have applied this technology to generate a bispecific antibody suitable for development as a human therapeutic. This antibody directly inhibits the activation of the high affinity IgE receptor FcϵRI on mast cells and basophils by cross-linking FcϵRI with the inhibitory receptor FcγRIIb, an approach that has strong therapeutic potential for asthma and other allergic diseases. Our approach for producing human bispecific full-length antibodies enables the clinical application of bispecific antibodies to a validated therapeutic pathway in asthma.

Monoclonal antibodies: what are the pharmacokinetic and pharmacodynamic considerations for drug development?

Introduction: The number of monoclonal antibodies available for clinical use and under development has dramatically increased in the last 10 years. Understanding their pharmacokinetics and pharmacodynamics is essential for selecting the right clinical candidate, correct dose and regimen for a target indication. Areas covered: This article reviews the existing literature and knowledge of monoclonal antibodies. Specifically, the authors discuss monoclonal antibodies with respect to their pharmacokinetics (including absorption, distribution and elimination) and their pharmacodynamics. The authors also look at the pharmacokinetic/pharmacodynamic relationship, scaling from preclinical to clinical studies and selection of the first-in-human dose. Expert opinion: Monoclonal antibodies have complex pharmacokinetic and pharmacodynamic characteristics that are dependent on several factors. Therefore, it is important to improve our understanding of the pharmacokinetics and pharmacodynamics of monoclonal antibodies from a basic research standpoint. It is also equally important to apply mechanistic pharmacokinetic/pharmacodynamic models to interpret the experimental results and facilitate efforts to predict the safety and efficacy of monoclonal antibodies.

Effects of altered FcγR binding on antibody pharmacokinetics in cynomolgus monkeys.

Antibody interactions with Fcγ receptors (FcγRs), like FcγRIIIA, play a critical role in mediating antibody effector functions and thereby contribute significantly to the biologic and therapeutic activity of antibodies. Over the past decade, considerable work has been directed towards production of antibodies with altered binding affinity to FcγRs and evaluation of how the alterations modulate their therapeutic activity. This has been achieved by altering glycosylation status at N297 or by engineering modifications in the crystallizable fragment (Fc) region. While the effects of these modifications on biologic activity and efficacy have been examined, few studies have been conducted to understand their effect on antibody pharmacokinetics (PK). We present here a retrospective analysis in which we characterize the PK of three antibody variants with decreased FcγR binding affinity caused by amino acid substitutions in the Fc region (N297A, N297G, and L234A/L235A) and three antibody variants with increased FcγRIIIA binding affinity caused by afucosylation at N297, and compare their PK to corresponding wild type antibody PK in cynomolgus monkeys. For all antibodies, PK was examined at a dose that was known to be in the linear range. Since production of the N297A and N297G variants in Chinese hamster ovary cells results in aglycosylated antibodies that do not bind to FcγRs, we also examined the effect of expression of an aglycosylated antibody, without sequence change(s), in E. coli. All the variants demonstrated similar PK compared with that of the wild type antibodies, suggesting that, for the six antibodies presented here, altered FcγR binding affinity does not affect PK.

Subcutaneous bioavailability of therapeutic antibodies as a function of FcRn binding affinity in mice

The neonatal Fc receptor (FcRn) plays an important and well-known role in immunoglobulin G (IgG) catabolism; however, its role in the disposition of IgG after subcutaneous (SC) administration, including bioavailability, is relatively unknown. To examine the potential effect of FcRn on IgG SC bioavailability, we engineered three anti-amyloid β monoclonal antibody (mAb) reverse chimeric mouse IgG2a (mIgG2a) Fc variants (I253A.H435A, N434H and N434Y) with different binding affinities to mouse FcRn (mFcRn) and compared their SC bioavailability to that of the wild-type (WT) mAb in mice. Our results indicated that the SC bioavailability of mIgG2a was affected by mFcRn-binding affinity. Variant I253A.H435A, which did not bind to mFcRn at either pH 6.0 or pH 7.4, had the lowest bioavailability (41.8%). Variant N434Y, which had the greatest increase in binding affinity at both pH 6.0 and pH 7.4, had comparable bioavailability to the WT antibody (86.1% vs. 76.3%), whereas Variant N434H, which had modestly increased binding affinity at pH 6.0 to mFcRn and affinity comparable to the WT antibody at pH 7.4, had the highest bioavailability (94.7%). A semi-mechanism-based pharmacokinetic model, which described well the observed data with the WT antibody and variant I253A.H435A, is consistent with the hypothesis that the decreased bioavailability of variant I253A.H435A was due to loss of the FcRn-mediated protection from catabolism at the absorption site. Together, these data demonstrate that FcRn plays an important role in SC bioavailability of therapeutic IgG antibodies.

Preclinical Pharmacokinetic Considerations for the Development of Antibody Drug Conjugates

Antibody drug conjugates (ADCs) are an emerging new class of targeted therapeutics for cancer that use antibodies to deliver cytotoxic drugs to cancer cells. There are two FDA approved ADCs on the market and over 30 ADCs in the clinical pipeline against a number of different cancer types. The structure of an ADC is very complex with multiple components and considerable efforts are ongoing to determine the attributes necessary for clinical success. Understanding the pharmacokinetics of an ADC and how it impacts efficacy and toxicity is a critical part of optimizing ADC design and delivery i.e., dose and schedule. This review discusses the pharmacokinetic considerations for an ADC and tools and strategies that can be used to evaluate molecules at the preclinical stage.

Preclinical pharmacokinetics, pharmacodynamics, tissue distribution, and tumor penetration of anti-PD-L1 monoclonal antibody, an immune checkpoint inhibitor

ABStract MPDL3280A is a human monoclonal antibody that targets programmed cell death-1 ligand 1 (PD-L1), and exerts anti-tumor activity mainly by blocking PD-L1 interaction with programmed cell death-1 (PD-1) and B7.1. It is being investigated as a potential therapy for locally advanced or metastatic malignancies. The purpose of the study reported here was to characterize the pharmacokinetics, pharmacodynamics, tissue distribution and tumor penetration of MPDL3280A and/or a chimeric anti-PD-L1 antibody PRO304397 to help further clinical development. The pharmacokinetics of MPDL3280A in monkeys at 0.5, 5 and 20 mg·kg−1 and the pharmacokinetics / pharmacodynamics of PRO304397 in mice at 1, 3 10 mg·kg−1 were determined after a single intravenous dose. Tissue distribution and tumor penetration for radiolabeled PRO304397 in tumor-bearing mouse models were determined. The pharmacokinetics of MPDL3280A and PRO304397 were nonlinear in monkeys and mice, respectively. Complete saturation of PD-L1 in blood in mice was achieved at serum concentrations of PRO304397 above ∼0.5 µg·mL−1. Tissue distribution and tumor penetration studies of PRO304397 in tumor-bearing mice indicated that the minimum tumor interstitial to plasma radioactivity ratio was ∼0.3; saturation of target-mediated uptake in non–tumor tissues and desirable exposure in tumors were achieved at higher serum concentrations, and the distribution into tumors was dose-and time-dependent. The biodistribution data indicated that the efficacious dose is mostly likely higher than that estimated based on simple pharmacokinetics/pharmacodynamics in blood. These data also allowed for estimation of the target clinical dose for further development of MPDL3280A.

Modeling approach to investigate the effect of neonatal Fc receptor binding affinity and anti-therapeutic antibody on the pharmacokinetic of humanized monoclonal anti-tumor necrosis factor-α IgG antibody in cynomolgus monkey.

PURPOSE Several neonatal Fc receptor (FcRn) variants of an anti-tumor necrosis factor (TNF)-α humanized monoclonal IgG antibodies (mAbs) were developed but the effect of their differential FcRn binding affinities on pharmacokinetic (PK) behavior were difficult to be definitively measured in vivo due to formation of anti-therapeutic antibody (ATA). A semi-mechanistic model was developed to investigate the quantitative relationship between the FcRn binding affinity and PK of mAbs in cynomolgus monkey with the presence of ATA. METHODS PK and ATA data from cynomolgus monkeys which received a single intravenous dose of adalimumab, wild-type or two FcRn variant (N434H and N434A) anti-TNF-α mAbs were included in the analysis. Likelihood-based censored data handling method was used to include many PK observations with BQL values for model development. A fully integrated PK-ATA model was developed and used to fit simultaneously to the PK/ATA data. RESULTS AND CONCLUSIONS The PK and ATA time-profiles and effect of FcRn-binding affinity on PK of mAbs were well described by the model and the parameters were estimated with good precision. The model was used successfully to construct quantitative relationships between FcRn binding affinity and PK of anti-TNF-α mAbs in the presence of the ATA-mediated elimination and interferences.

Projecting human pharmacokinetics of monoclonal antibodies from nonclinical data: comparative evaluation of prediction approaches in early drug development.

Currently, more than 350 monoclonal antibodies (mAbs) and mAb derivatives are under development as therapeutics. The prediction of mAb pharmacokinetics (PK)/pharmacodynamics (PD) plays a key role in starting dose selection for first-in-human (FIH) studies. This article presents a brief overview of the biology and mechanisms of absorption, distribution, metabolism and excretion (ADME) for mAbs. In addition, a detailed review of mAb human PK/PD prediction from nonclinical data is provided, including allometry for mAbs with linear or nonlinear PK, species-invariant time method, physiologically based PK (PBPK) modeling and target-mediated drug disposition (TMDD) model, bioavailability projection and immunogenicity impact on PK prediction. Finally, from an industry perspective a decision tree of mAb human PK projection is proposed to facilitate drug development.