Translational population target binding model for the anti-FcRn fragment antibody efgartigimod

Efgartigimod is a human IgG1 antibody Fc-fragment that lowers IgG levels through blockade of the neonatal Fc receptor (FcRn) and is being evaluated for the treatment of patients with severe autoimmune diseases mediated by pathogenic IgG autoantibodies. Engineered for increased FcRn affinity at both acidic and physiological pH, efgartigimod can outcompete endogenous IgG binding, preventing FcRn-mediated recycling of IgGs and resulting in increased lysosomal degradation. A population pharmacokinetic-pharmacodynamic (PKPD) model including FcRn binding was developed based on data from two healthy volunteer studies after single and repeated administration of efgartigimod. This model was able to simultaneously describe the serum efgartigimod and total IgG profiles across dose groups, using drug-induced FcRn receptor occupancy as driver of total IgG suppression. The model was expanded to describe the PKPD of efgartigimod in cynomolgus monkeys, rabbits, rats and mice. Most species differences were explainable by including the species-specific in vitro affinity for FcRn binding at pH 7.4 and by allometric scaling of the physiological parameters. In vitro-in vivo scaling proved crucial for translation success: the drug effect was over/underpredicted in rabbits/mice when ignoring the lower/higher binding affinity of efgartigimod for these species versus human, respectively. Given the successful model prediction of the PK and total IgG dynamics across species, it was concluded that the PKPD of efgartigimod can be characterized by target binding. From the model, it is suggested that the initial fast decrease of measurable unbound efgartigimod following dosing is the result of combined clearance of free drug and high affinity target binding, while the relatively slow terminal PK phase reflects release of bound drug from the receptor. High affinity target binding protects the drug from elimination and results in a sustained PD effect characterized by an increase in the IgG degradation rate constant with increasing target receptor occupancy.

Review of the Existing Translational Pharmacokinetics Modeling Approaches Specific to Monoclonal Antibodies (mAbs) to Support the First-In-Human (FIH) Dose Selection

The interest in therapeutic monoclonal antibodies (mAbs) has continuously growing in several diseases. However, their pharmacokinetics (PK) is complex due to their target-mediated drug disposition (TMDD) profiles which can induce a non-linear PK. This point is particularly challenging during the pre-clinical and translational development of a new mAb. This article reviews and describes the existing PK modeling approaches used to translate the mAbs PK from animal to human for intravenous (IV) and subcutaneous (SC) administration routes. Several approaches are presented, from the most empirical models to full physiologically based pharmacokinetic (PBPK) models, with a focus on the population PK methods (compartmental and minimal PBPK models). They include the translational approaches for the linear part of the PK and the TMDD mechanism of mAbs. The objective of this article is to provide an up-to-date overview and future perspectives of the translational PK approaches for mAbs during a model-informed drug development (MIDD), since the field of PK modeling has gained recently significant interest for guiding mAbs drug development.

Pharmacokinetics and pharmacodynamics of the cytolytic anti-CD38 human monoclonal antibody TAK-079 in monkey - model assisted preparation for the first in human trial

We are studying the fully human, IgG1λ cytolytic monoclonal antibody TAK-079, which binds CD38. CD38 is expressed on plasma and natural killer (NK) cells constitutively and upregulated on subsets of B and T lymphocytes upon activation. TAK-079 cross-reacts with CD38 expressed by cynomolgus monkeys and depletes subsets of NK, B, and T cells. Therefore, safety and function of TAK-079 was evaluated in this species, prior to clinical development, using bioanalytical, and flow cytometry assays. We pooled the data from eight studies in healthy monkeys (dose range 0.03-100 mg/kg) and developed mathematical models that describe the pharmacokinetics and the exposure-effect relationship for NK cells, B cells, and T cells. NK cell depletion was identified as the most sensitive pharmacodynamic effect of TAK-079. It was adequately described with a turnover model (C₅₀  = 27.5 μg/mL on depletion rate) and complete depletion was achieved with an IV dose of 0.3 mg/kg. Intermediate effects on T-cell counts were described with a direct response model (C₅₀  = 11.9 μg/mL) and on B-cell counts with a 4-transit-compartment model (C₅₀  = 19.8 μg/mL on depletion rate). Our analyses substantiate the observation that NK, B and T cells are cleared by TAK-079 at different rates and required different time spans to replete the blood compartment. The models were used to simulate pharmacokinetic and cell depletion profiles in humans after applying a straightforward scaling approach for monoclonal antibodies in preparation for the first-in-human clinical trial.

Modification of the Fc Region of a Human Anti-oncostatin M Monoclonal Antibody for Higher Affinity to FcRn Receptor and Extension of Half-life in Cynomolgus Monkeys

The purpose of this study was to evaluate the pharmacokinetics (PK) of anti-oncostatin M (OSM) IgG1 monoclonal antibodies, CNTO 1119 and its Fc variant (CNTO 8212), which incorporates the LS(Xtend) mutation to extend terminal half-life (T_1/2 ), after a single intravenous (IV) or subcutaneous (SC) administration in cynomolgus monkeys, and to predict human PK. In study 1, single doses of CNTO 1119 and CNTO 8212 were administered IV or SC at 3 mg/kg to cynomolgus monkeys (n = 3 per group). In study 2, single doses of CNTO 8212 were administered IV at 1, 5 or 20 mg/kg, or SC at 5 mg/kg to cynomolgus monkeys (n = 5 per group). Serial blood samples were collected for assessment of serum concentrations of CNTO 1119 and/or CNTO 8212. A two-compartment population PK model with first-order elimination was utilized to simultaneously describe the serum concentrations of CNTO 1119 and CNTO 8212 over time after IV and SC administration in cynomolgus monkeys. The typical population PK parameter estimates for CNTO 1119 in cynomolgus monkeys were clearance (CL) = 2.81 mL/day/kg, volume of distribution of central compartment (V₁ ) = 31.3 mL/kg, volume of distribution of peripheral compartment (V₂ ) = 23.3 mL/kg, absolute bioavailability (F) = 0.84 and T_1/2 = 13.4 days. In comparison, the typical population PK parameter estimates for CNTO 8212 in cynomolgus monkeys were CL = 1.41 mL/day/kg, V₁ = 39.8 mL/kg, V₂ = 32.6 mL/kg, F = 0.75 and T_1/2 = 35.7 days. The mean CL of CNTO 8212 was ~50% lower compared with that for CNTO 1119 in cynomolgus monkeys. The overall volume of distribution (V₁ +V₂ ) for CNTO 8212 was about 32% larger compared with that for CNTO 1119, but generally similar to the vascular volume in cynomolgus monkeys. The T_1/2 of CNTO 8212 was significantly (p < 0.05) longer by about 2.7-fold than that for CNTO 1119 in cynomolgus monkeys. Thus, the modification of the Fc portion of an anti-OSM IgG1 mAb for higher FcRn binding affinity resulted in lower systemic clearance and a longer terminal half-life in cynomolgus monkeys. CNTO 8212 demonstrated linear PK after a single IV dose (1-20 mg/kg) in cynomolgus monkeys. The predicted human PK parameters suggest that CNTO 8212 is likely to exhibit slow clearance and long terminal half-life in human beings and may likely allow less frequent dosing in the clinical setting.

Pharmacokinetics and immunogenicity investigation of a human anti-interleukin-17 monoclonal antibody in non-naïve cynomolgus monkeys

The pharmacokinetics (PK) of biologic therapeutics, especially monoclonal antibodies (mAbs), in monkeys generally presents the most relevant predictive PK information for humans. However, human mAbs, xenogeneic proteins to monkeys, are likely to be immunogenic. Monkeys previously treated with a human mAb (non-naïve) may have developed antidrug antibodies (ADAs) that cross-react with another test mAb in subsequent studies. Unlike PK studies for small-molecule therapeutics, in which animals may be reused, naïve monkeys have been used almost exclusively for preclinical PK studies of biologic therapeutics to avoid potential pre-existing immunologic cross-reactivity issues. The propensity and extent of pre-existing ADAs have not been systematically investigated to date. In this study, the PK and immunogenicity of mAb A, a human anti-human interkeukin-17 mAb, were investigated in a colony of 31 cynomolgus monkeys previously exposed to other human mAbs against different targets. We screened the monkeys for pre-existing antibodies to mAb A prior to the PK study and showed that 44% of the monkeys had pre-existing cross-reactive antibodies to mAb A, which could affect the PK characterization of the antibody. In the subcolony of monkeys without measurable pre-existing ADAs, PK and immunogenicity of mAb A were successfully characterized. The impact of ADAs on mAb A PK was also demonstrated in the monkeys with pre-existing ADAs. Here we report the results and propose a pragmatic approach for the use of non-naïve monkeys when conducting PK studies of biologic therapeutics.

Non-Clinical Pharmacokinetics, Prediction of Human Pharmacokinetics and First-in-Human Dose Selection for CNTO 5825, an Anti-Interleukin-13 Monoclonal Antibody

CNTO 5825 is a human anti-interleukin-13 (IL-13) monoclonal antibody (mAb) that inhibits binding of human IL-13 to IL-13Rα1 and IL-13Rα2. The purpose of this investigation was to predict human pharmacokinetics (PK) of CNTO 5825 using different allometric approaches and non-clinical PK data in order to select the right and safe doses for first-in-human (FIH) study. After intravenous (IV) administration of CNTO 5825, clearance (CL) ranged from 9.98 to 11.49 ml/day/kg in rats and from 5.78 to 7.19 ml/day/kg in cynomolgus monkeys. The volume of distribution at steady-state (Vss) in rats was large (151.52-155.64 ml/kg) compared to cynomolgus monkey (49.77-61.10 ml/kg). The terminal half-life (T1/2 ) ranged from 12.29 to 14.15 days in rats and from 6.61 to 7.73 days in cynomolgus monkeys. The PK of CNTO 5825 was linear in 1-10 mg/kg dose range in both species. The bioavailability after subcutaneous (SC) administration was 94% and 79% in rats and cynomolgus monkeys, respectively. The predicted CL and Vss based on allometric methods and PK data from rats and monkeys were within twofold of observed CL and Vss in human beings; the predicted CL and Vss in human beings (70 kg) based on time-invariant method with combined PK data from rats and monkeys were 4.84 ± 1.13 ml/day/kg and 68.93 ± 35.55 ml/kg, respectively. The selected doses for the FIH study based on time-invariant method and no observed adverse effect level in toxicity studies in rats and monkeys provided exposures that were subsequently shown to be well tolerated and safe in human beings.

Onartuzumab (MetMAb): using nonclinical pharmacokinetic and concentration-effect data to support clinical development

PURPOSE

We characterized the pharmacokinetics of onartuzumab (MetMAb) in animals and determined a concentration-effect relationship in tumor-bearing mice to enable estimation of clinical pharmacokinetics and target doses.

EXPERIMENTAL DESIGN

A tumor growth inhibition model was used to estimate tumoristatic concentrations (TSC) in mice. Human pharmacokinetic parameters were projected from pharmacokinetics in cynomolgus monkeys by the species-invariant time method. Monte Carlo simulations predicted the percentage of patients achieving steady-state trough serum concentrations (Ctrough ss) ≥TSC for every 3-week (Q3W) dosing.

RESULTS

Onartuzumab clearance (CL) in the linear dose range was 21.1 and 12.2 mL/d/kg in mice and cynomolgus monkeys with elimination half-life at 6.10 and 3.37 days, respectively. The estimated TSC in KP4 pancreatic xenograft tumor-bearing mice was 15 μg/mL. Projected CL for humans in the linear dose range was 5.74 to 9.36 mL/d/kg with scaling exponents of CL at 0.75 to 0.9. Monte Carlo simulations projected a Q3W dose of 10 to 30 mg/kg to achieve Ctrough ss of 15 μg/mL in 95% or more of patients.

CONCLUSIONS

Onartuzumab pharmacokinetics differed from typical bivalent glycosylated monoclonal antibodies with approximately 2-times faster CL in the linear dose range. Despite this higher CL, xenograft efficacy data supported dose flexibility with Q1W to Q3W dose regimens in the clinical setting with a TSC of 15 μg/mL as the Ctrough ss target. The projected human efficacious dose of 10 to 30 mg/kg Q3W should achieve the target TSC of 15 μg/mL. These data show effective pharmacokinetic/pharmacodynamic modeling to project doses to be tested in the clinic.

Correlations between pharmacokinetics of IgG antibodies in primates vs. FcRn-transgenic mice reveal a rodent model with predictive capabilities

Transgenic mice expressing human neonatal Fc receptor (FcRn) instead of mouse FcRn are available for IgG antibody pharmacokinetic (PK) studies. Given the interest in a rodent model that offers reliable predictions of antibody PK in monkeys and humans, we set out to test whether the PK of IgG antibodies in such mice correlated with the PK of the same antibodies in primates. We began by using a single research antibody to study the influence of: (1) different transgenic mouse lines that differ in FcRn transgene expression; (2) homozygous vs. hemizygous FcRn transgenic mice; (3) the presence vs. absence of coinjected high-dose human intravenous immunoglobulin (IVIG), and (4) the presence vs. absence of coinjected high-dose human serum albumin (HSA). Results of those studies suggested that use of hemizygous Tg32 mice (Tg32 hemi) not treated with IVIG or HSA offered potential as a predictive model for PK in humans. Mouse PK studies were then done under those conditions with a panel of test antibodies whose PK in mice and primates is not significantly affected by target binding, and for which monkey or human PK data were readily available. Results from the studies revealed significant correlations between terminal half-life or clearance values observed in the mice and the corresponding values reported in humans. A significant relationship in clearance values between mice and monkeys was also observed. These correlations suggest that the Tg32 hemi mouse model, which is both convenient and cost-effective, can offer value in predicting antibody half-life and clearance in primates.

Issues, challenges, and opportunities in model-based drug development for monoclonal antibodies

Over the last two decades, there has been a simultaneous explosion in the levels of activity and capability in both monoclonal antibody (mAb) drug development and in the use of quantitative pharmacologic models to facilitate drug development. Both of these topics are currently areas of great interest to academia, the pharmaceutical and biotechnology industries, and to regulatory authorities. In this article, we summarize convergence of these two areas and discuss some of the current and historical applications of the use of mathematical-model-based techniques to facilitate the discovery and development of mAb therapeutics. We also consider some of the current issues and limitations in model-based antibody discovery/development and highlight areas of further opportunity.