Prediction of human serum concentration-time profiles of therapeutic monoclonal antibodies using common marmosets (Callithrix jacchus): initial assessment with canakinumab, adalimumab, and bevacizumab

Cynomolgus monkeys and human FcRn transgenic mice are generally used for pharmacokinetic predictions of therapeutic monoclonal antibodies (mAbs). In the present study, the application of the common marmoset, a small nonhuman primate, as a potential animal model for prediction was evaluated for the first time.Canakinumab, adalimumab, and bevacizumab, which exhibited linear pharmacokinetics in humans, were selected as the model compounds. Marmoset pharmacokinetic data were reportedly available only for canakinumab, and those for adalimumab and bevacizumab were acquired in-house.Four pharmacokinetic parameters for a two-compartment model (i.e. clearance and volume of distribution in the central and peripheral compartments) in marmosets were extrapolated to the values in humans with allometric scaling using the average exponents of the three mAbs. As a result, the observed human serum concentration-time curves of the three mAbs following intravenous administration and those of canakinumab and adalimumab following subcutaneous injections (with an assumed absorption rate constant and bioavailability) were reasonably predicted.Although further prediction studies using a sufficient number of other mAbs are necessary to evaluate the versatility of this model, the findings indicate that marmosets can be an alternative to preceding animals for human pharmacokinetic predictions of therapeutic mAbs.

Impact of LS Mutation on Pharmacokinetics of Preventive HIV Broadly Neutralizing Monoclonal Antibodies: A Cross-Protocol Analysis of 16 Clinical Trials in People without HIV

Monoclonal antibodies are commonly engineered with an introduction of Met428Leu and Asn434Ser, known as the LS mutation, in the fragment crystallizable region to improve pharmacokinetic profiles. The LS mutation delays antibody clearance by enhancing binding affinity to the neonatal fragment crystallizable receptor found on endothelial cells. To characterize the LS mutation for monoclonal antibodies targeting HIV, we compared pharmacokinetic parameters between parental versus LS variants for five pairs of anti-HIV immunoglobin G1 monoclonal antibodies (VRC01/LS/VRC07-523LS, 3BNC117/LS, PGDM1400/LS PGT121/LS, 10-1074/LS), analyzing data from 16 clinical trials of 583 participants without HIV. We described serum concentrations of these monoclonal antibodies following intravenous or subcutaneous administration by an open two-compartment disposition, with first-order elimination from the central compartment using non-linear mixed effects pharmacokinetic models. We compared estimated pharmacokinetic parameters using the targeted maximum likelihood estimation method, accounting for participant differences. We observed lower clearance rate, central volume, and peripheral volume of distribution for all LS variants compared to parental monoclonal antibodies. LS monoclonal antibodies showed several improvements in pharmacokinetic parameters, including increases in the elimination half-life by 2.7- to 4.1-fold, the dose-normalized area-under-the-curve by 4.1- to 9.5-fold, and the predicted concentration at 4 weeks post-administration by 3.4- to 7.6-fold. Results suggest a favorable pharmacokinetic profile of LS variants regardless of HIV epitope specificity. Insights support lower dosages and/or less frequent dosing of LS variants to achieve similar levels of antibody exposure in future clinical applications.

Human Dose and Pharmacokinetic Predictions for Biologics at Boehringer Ingelheim: A Retrospective Analysis

INTRODUCTION

Accurate predictions of pharmacokinetics and efficacious doses for biologics in humans are critical for selecting appropriate first-in-human starting doses and dose ranges and for estimating clinical material needs and cost of goods. This also impacts clinical feasibility, particularly for subcutaneously administered biologics.

METHODS

We performed a comprehensive comparison between predicted and observed clearances and doses in humans for a set of 22 biologic drugs developed at Boehringer Ingelheim (BI) over the last 2 decades. The analysis included biologics across three therapeutic areas comprising a wide variety of modalities: mono- and bispecific monoclonal antibodies (mAbs) and nanobodies and a Fab fragment.

RESULTS

Our analysis showed that observed clearances in humans were within twofold of predicted clearances for 17 out of 20 biologics (85%). Six biologics had uncharacteristically high observed human clearances (range 32-280 mL/h) for their respective molecular classes, impacting their clinical developability. For three molecules, molecular characteristics contributed to the high clearance. Clinically selected doses were within twofold of predicted for 58% of projects. With 42% and 25% of projects selecting clinical doses higher than two- or threefold the predicted value, respectively, the importance of better understanding not only the pharmacokinetic (PK) but also the predictivity of pharmacodynamic models is highlighted.

CONCLUSIONS

We provide a clinical pharmacology perspective on the commonly accepted twofold range of human clearance predictions as well as the implications of higher than predicted targeted efficacious plasma concentration on clinical development. Finally, an analysis of key success factors for biologics at BI was conducted, which may be relevant for the entire pharmaceutical industry. This is one of the largest retrospective analyses for biologics and provides further evidence that successful predictions of human PK and efficacious dose will be further facilitated by gathering key translational data early in research.

Physiologically based pharmacokinetic model combined with reverse dose method to study the nephrotoxic tolerance dose of tacrolimus

Nephrotoxicity is the most common side effect that severely limits the clinical application of tacrolimus (TAC), an immunosuppressive agent used in kidney transplant patients. This study aimed to explore the tolerated dose of nephrotoxicity of TAC in individuals with different CYP3A5 genotypes and liver conditions. We established a human whole-body physiological pharmacokinetic (WB-PBPK) model and validated it using data from previous clinical studies. Following the injection of 1 mg/kg TAC into the tail veins of male rats, we developed a rat PBPK model utilizing the drug concentration-time curve obtained by LC-MS/MS. Next, we converted the established rat PBPK model into the human kidney PBPK model. To establish renal concentrations, the BMCL5 of the in vitro CCK-8 toxicity response curve (drug concentration range: 2-80 mol/L) was extrapolated. To further investigate the acceptable levels of nephrotoxicity for several distinct CYP3A5 genotypes and varied hepatic function populations, oral dosing regimens were extrapolated utilizing in vitro-in vivo extrapolation (IVIVE). The PBPK model indicated the tolerated doses of nephrotoxicity were 0.14-0.185 mg/kg (CYP3A5 expressors) and 0.13-0.155 mg/kg (CYP3A5 non-expressors) in normal healthy subjects and 0.07-0.09 mg/kg (CYP3A5 expressors) and 0.06-0.08 mg/kg (CYP3A5 non-expressors) in patients with mild hepatic insufficiency. Further, patients with moderate hepatic insufficiency tolerated doses of 0.045-0.06 mg/kg (CYP3A5 expressors) and 0.04-0.05 mg/kg (CYP3A5 non-expressors), while in patients with moderate hepatic insufficiency, doses of 0.028-0.04 mg/kg (CYP3A5 expressors) and 0.022-0.03 mg/kg (CYP3A5 non-expressors) were tolerated. Overall, our study highlights the combined usage of the PBPK model and the IVIVE approach as a valuable tool for predicting toxicity tolerated doses of a drug in a specific group.

Mechanistic Model Describing the Time Course of Humoral Immunity Following Ad26.COV2.S Vaccination in Non-Human Primates

Mechanistic modeling can be used to describe the time course of vaccine-induced humoral immunity and to identify key biologic drivers in antibody production. We used a six-compartment mechanistic model to describe a 20-week time course of humoral immune responses in 56 non-human primates (NHPs) elicited by vaccination with Ad26.COV2.S according to either a single-dose regimen (1 × 1011 or 5 × 1010 viral particles [vp]) or a two-dose homologous regimen (5 × 1010 vp) given in an interval of 4 or 8 weeks. Humoral immune responses were quantified by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike-specific binding antibody concentrations as determined by spike protein-enzyme-linked immunosorbent assay. The mechanistic model adequately described the central tendency and variability of binding antibody concentrations through 20 weeks in all vaccination arms. The estimation of mechanistic modeling parameters revealed greater contribution of the antibody production mediated by short-lived cells as compared with long-lived cells in driving the peak response, especially post second dose when a more rapid peak response was observed. The antibody production mediated by long-lived cells was identified as relevant for generating the first peak and for contributing to the long-term time course of sustained antibody concentrations in all vaccination arms. The findings contribute evidence on the key biologic components responsible for the observed time course of vaccine-induced humoral immunity in NHPs and constitute a step toward defining immune biomarkers of protection against SARS-CoV-2 that might translate across species. SIGNIFICANCE STATEMENT: We demonstrate the adequacy of a mechanistic modeling approach describing the time course of binding antibody concentrations in non-human primates (NHPs) elicited by different dose levels and regimens of Ad26.COV2.S. The findings are relevant for informing the mechanism-based accounts of vaccine-induced humoral immunity in NHPs and translational research efforts aimed at identifying immune biomarkers of protection against SARS-CoV-2 infection.

A long-acting GDF15 analog causes robust, sustained weight loss and reduction of food intake in an obese nonhuman primate model

Growth Differentiation Factor-15 (GDF15) is a circulating polypeptide linked to cellular stress and metabolic adaptation. GDF15's half-life is ~3 h and activates the glial cell line-derived neurotrophic factor family receptor alpha-like (GFRAL) receptor expressed in the area postrema. To characterize sustained GFRAL agonism on food intake (FI) and body weight (BW), we tested a half-life extended analog of GDF15 (Compound H [CpdH]) suitable for reduced dosing frequency in obese cynomolgus monkeys. Animals were chronically treated once weekly (q.w.) with CpdH or long-acting GLP-1 analog dulaglutide. Mechanism-based longitudinal exposure-response modeling characterized effects of CpdH and dulaglutide on FI and BW. The novel model accounts for both acute, exposure-dependent effects reducing FI and compensatory changes in energy expenditure (EE) and FI occurring over time with weight loss. CpdH had linear, dose-proportional pharmacokinetics (terminal half-life ~8 days) and treatment caused exposure-dependent reductions in FI and BW. The 1.6 mg/kg CpdH reduced mean FI by 57.5% at 1 week and sustained FI reductions of 31.5% from weeks 9-12, resulting in peak reduction in BW of 16 ± 5%. Dulaglutide had more modest effects on FI and peak BW loss was 3.8 ± 4.0%. Longitudinal modeling of both the FI and BW profiles suggested reductions in BW observed with both CpdH and dulaglutide were fully explained by exposure-dependent reductions in FI without increase in EE. Upon verification of the pharmacokinetic/pharmacodynamic relationship established in monkeys and humans for dulaglutide, we predicted that CpdH could reach double digit BW loss in humans. In summary, a long-acting GDF15 analog led to sustained reductions in FI in overweight monkeys and holds potential for effective clinical obesity pharmacotherapy.

Application of Modelling and Simulation Approaches to Predict Pharmacokinetics of Therapeutic Monoclonal Antibodies in Pediatric Population

Ethical regulations and limited paediatric participants are key challenges that contribute to a median delay of 6 years in paediatric mAb approval. To overcome these barriers, modelling and simulation methodologies have been adopted to design optimized paediatric clinical studies and reduce patient burden. The classical modelling approach in paediatric pharmacokinetic studies for regulatory submissions is to apply body weight-based or body surface area-based allometric scaling to adult PK parameters derived from a popPK model to inform the paediatric dosing regimen. However, this approach is limited in its ability to account for the rapidly changing physiology in paediatrics, especially in younger infants. To overcome this limitation, PBPK modelling, which accounts for the ontogeny of key physiological processes in paediatrics, is emerging as an alternative modelling strategy. While only a few mAb PBPK models have been published, PBPK modelling shows great promise demonstrating a similar prediction accuracy to popPK modelling in an Infliximab paediatric case study. To facilitate future PBPK studies, this review consolidated comprehensive data on the ontogeny of key physiological processes in paediatric mAb disposition. To conclude, this review discussed different use-cases for pop-PK and PBPK modelling and how they can complement each other to increase confidence in pharmacokinetic predictions.

Translational Approach for Predicting Human Pharmacokinetics of Engineered Therapeutic Monoclonal Antibodies with Increased FcRn-Binding Mutations

INTRODUCTION

Recently, increasing FcRn binding by Fc engineering has become a promising approach for prolonging the half-life of therapeutic monoclonal antibodies (mAbs). This study is the first to investigate the optimization of an allometric scaling approach for engineered mAbs based on cynomolgus monkey data to predict human pharmacokinetics.

METHODS

Linear two-compartmental model parameters (clearance [CL]; volume of distribution in the central compartment [V_c]; inter-compartmental clearance [Q]; volume of distribution in the peripheral compartment [V_p]) after the intravenous (IV) injection of engineered mAbs (M252Y/S254T/T256E or M428L/N434S mutations) in cynomolgus monkeys and humans were collected from published data. We explored the optimal exponent for allometric scaling to predict parameters in humans based on cynomolgus monkey data. Moreover, the plasma concentration-time profile of engineered mAbs after IV injection in humans was predicted using parameters estimated based on an optimized exponent.

RESULTS

For engineered mAbs, a significant positive correlation between cynomolgus monkeys and humans was observed for CL, but not for other parameters. Whereas conventional exponents (CL: 0.8, Q: 0.75, V_c: 1.0, V_p: 0.95) previously established for normal mAbs showed poor prediction accuracy for CL and Q of engineered mAbs, the newly optimized exponents (CL: 0.55, Q: 0.6, V_c: 0.95, V_p: 0.95) achieved superior predictability for engineered mAbs. Moreover, the optimized exponents accurately predicted plasma mAb concentration-time profiles after IV injection of engineered mAbs in humans.

CONCLUSIONS

We found that engineered mAbs require specially optimized exponents to accurately predict pharmacokinetic parameters and plasma concentration-time profiles after IV injections in humans based on cynomolgus monkey data. This optimized approach can contribute to a more accurate prediction of human pharmacokinetics in the development of engineered mAbs.

An Fc variant with two mutations confers prolonged serum half-life and enhanced effector functions on IgG antibodies

The pH-selective interaction between the immunoglobulin G (IgG) fragment crystallizable region (Fc region) and the neonatal Fc receptor (FcRn) is critical for prolonging the circulating half-lives of IgG molecules through intracellular trafficking and recycling. By using directed evolution, we successfully identified Fc mutations that improve the pH-dependent binding of human FcRn and prolong the serum persistence of a model IgG antibody and an Fc-fusion protein. Strikingly, trastuzumab-PFc29 and aflibercept-PFc29, a model therapeutic IgG antibody and an Fc-fusion protein, respectively, when combined with our engineered Fc (Q311R/M428L), both exhibited significantly higher serum half-lives in human FcRn transgenic mice than their counterparts with wild-type Fc. Moreover, in a cynomolgus monkey model, trastuzumab-PFc29 displayed a superior pharmacokinetic profile to that of both trastuzumab-YTE and trastuzumab-LS, which contain the well-validated serum half-life extension Fcs YTE (M252Y/S254T/T256E) and LS (M428L/N434S), respectively. Furthermore, the introduction of two identified mutations of PFc29 (Q311R/M428L) into the model antibodies enhanced both complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity activity, which are triggered by the association between IgG Fc and Fc binding ligands and are critical for clearing cancer cells. In addition, the effector functions could be turned off by combining the two mutations of PFc29 with effector function-silencing mutations, but the antibodies maintained their excellent pH-dependent human FcRn binding profile. We expect our Fc variants to be an excellent tool for enhancing the pharmacokinetic profiles and potencies of various therapeutic antibodies and Fc-fusion proteins.

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.

Molecular Biosimilarity—An AI-Driven Paradigm Shift

Scientific, technical, and bioinformatics advances have made it possible to establish analytics-based molecular biosimilarity for the approval of biosimilars. If the molecular structure is identical and other product- and process-related attributes are comparable within the testing limits, then a biosimilar candidate will have the same safety and efficacy as its reference product. Classical testing in animals and patients is much less sensitive in terms of identifying clinically meaningful differences, as is reported in the literature. The recent artificial intelligence (AI)-based protein structure prediction model, AlphaFold-2, has confirmed that the primary structure of proteins always determines their 3D structure; thus, we can deduce that a biosimilar with an identical primary structure will have the same efficacy and safety. Further confirmation of the thesis has been established using technologies that are now much more sensitive. For example, mass spectrometry (MS) is thousands of times more sensitive and accurate when compared to any form of biological testing. While regulatory agencies have begun waiving animal testing and, in some cases, clinical efficacy testing, the removal of clinical pharmacology profiling brings with it a dramatic paradigm shift, reducing development costs without compromising safety or efficacy. A list of 160+ products that are ready to enter as biosimilars has been shared. Major actions from regulatory agencies and developers are required to facilitate this paradigm shift.

Early Feasibility Assessment: A Method for Accurately Predicting Biotherapeutic Dosing to Inform Early Drug Discovery Decisions

The application of model-informed drug discovery and development (MID3) approaches in the early stages of drug discovery can help determine feasibility of drugging a target, prioritize between targets, or define optimal drug properties for a target product profile (TPP). However, applying MID3 in early discovery can be challenging due to the lack of pharmacokinetic (PK) and pharmacodynamic (PD) data at this stage. Early Feasibility Assessment (EFA) is the application of mechanistic PKPD models, built from first principles, and parameterized by data that is readily available early in drug discovery to make effective dose predictions. This manuscript demonstrates the ability of EFA to make accurate predictions of clinical effective doses for nine approved biotherapeutics and outlines the potential of extending this approach to novel therapeutics to impact early drug discovery decisions.

Preclinical Characterization of ASP2713, a Novel Igβ and FcγRIIB Cross-Linking Antibody, for Prediction of Human Pharmacokinetics and Clinically Effective Dose

Previously, we reported the fundamental pharmacological characteristics of a novel Igβ and Fc gamma receptor IIB cross-linking antibody, ASP2713, as a new treatment option for systemic lupus erythematosus. The aims of the present study were to investigate ASP2713's characteristics with regard to pharmacological effect, pharmacokinetics (PK), and receptor occupancy, and to predict its human PK and clinically effective dose. The relationship between the concentration and receptor occupancy of ASP2713 for Igβ of B cell receptors was examined using whole blood B cells. Calculated EC₅₀ values in cynomolgus monkeys and healthy volunteers were 0.35 and 0.058 μg/mL, respectively. Dose-dependent inhibition of anti-tetanus toxoid (TTx) antibody production, PK, and receptor occupancy of ASP2713 in TTx-sensitized cynomolgus monkeys suggested a minimally effective dose of 1 mg/kg by single intravenous (IV) administration. Scaling-up of monkey PK parameters to humans by allometric scaling predicted a clinically effective dose of 0.4 mg/kg IV administration at 4-week intervals to maintain a trough concentration in humans which achieved the same receptor occupancy expected at the effective dose in monkeys. This study aids in understanding the characteristics of ASP2713 and can be used as a basis for clinical dose setting.

Mathematical Models to Characterize the Absorption, Distribution, Metabolism, and Excretion of Protein Therapeutics

Therapeutic proteins (TPs) have ranked among the most important and fastest-growing classes of drugs in the clinic, yet the development of successful TPs is often limited by unsatisfactory efficacy. Understanding pharmacokinetic (PK) characteristics of TPs is key to achieving sufficient and prolonged exposure at the site of action, which is a prerequisite for eliciting desired pharmacological effects. PK modeling represents a powerful tool to investigate factors governing in vivo disposition of TPs. In this mini-review, we discuss many state-of-the-art models that recapitulate critical processes in each of the absorption, distribution, metabolism/catabolism, and excretion pathways of TPs, which can be integrated into the physiologically-based pharmacokinetic framework. Additionally, we provide our perspectives on current opportunities and challenges for evolving the PK models to accelerate the discovery and development of safe and efficacious TPs. SIGNIFICANCE STATEMENT: This minireview provides an overview of mechanistic pharmacokinetic (PK) models developed to characterize absorption, distribution, metabolism, and elimination (ADME) properties of therapeutic proteins (TPs), which can support model-informed discovery and development of TPs. As the next-generation of TPs with diverse physicochemical properties and mechanism-of-action are being developed rapidly, there is an urgent need to better understand the determinants for the ADME of TPs and evolve existing platform PK models to facilitate successful bench-to-bedside translation of these promising drug molecules.

Recent Advances in Translational Pharmacokinetics and Pharmacodynamics Prediction of Therapeutic Antibodies Using Modeling and Simulation

Therapeutic monoclonal antibodies (mAbs) have been a promising therapeutic approach for several diseases and a wide variety of mAbs are being evaluated in clinical trials. To accelerate clinical development and improve the probability of success, pharmacokinetics and pharmacodynamics (PKPD) in humans must be predicted before clinical trials can begin. Traditionally, empirical-approach-based PKPD prediction has been applied for a long time. Recently, modeling and simulation (M&S) methods have also become valuable for quantitatively predicting PKPD in humans. Although several models (e.g., the compartment model, Michaelis–Menten model, target-mediated drug disposition model, and physiologically based pharmacokinetic model) have been established and used to predict the PKPD of mAbs in humans, more complex mechanistic models, such as the quantitative systemics pharmacology model, have been recently developed. This review summarizes the recent advances and future direction of M&S-based approaches to the quantitative prediction of human PKPD for mAbs.

Translational findings for odronextamab: From preclinical research to a first-in-human study in patients with CD20+ B-cell malignancies

Odronextamab is a fully‐human IgG4‐based CD20xCD3 bispecific antibody that binds to CD3 on T cells and CD20 on B cells, triggering T‐cell‐mediated cytotoxicity independent of T‐cell‐receptor recognition. Adequate safety, tolerability, and encouraging durable complete responses have been observed in an ongoing first‐in‐human (FIH) study of odronextamab in patients with relapsed/refractory (R/R) B‐cell non‐Hodgkin lymphoma (B‐NHL; NCT02290951). We retrospectively evaluated the pharmacokinetic, pharmacodynamic, and antitumor characteristics of odronextamab in a series of in vitro/in vivo preclinical experiments, to assess their translational value to inform dose escalation for the FIH study. Half‐maximal effective concentration values from in vitro cytokine release assays (range: 0.05–0.08 mg/L) provided a reasonable estimate of odronextamab concentrations in patients associated with cytokine release at a 0.5 mg dose (maximum serum concentration: 0.081 mg/L) on week 1/day 1, which could therefore be used to determine the week 1 clinical dose. Odronextamab concentrations resulting in 100% inhibition of tumor growth in a Raji xenograft tumor mouse model (1–10 mg/L) were useful to predict efficacious concentrations in patients and inform dose‐escalation strategy. Although predicted human pharmacokinetic parameters derived from monkey data overestimated projected odronextamab exposure, they provided a conservative estimate for FIH starting doses. With step‐up dosing, the highest‐tested weekly odronextamab dose in patients (320 mg) exceeded the 1 mg/kg single dose in monkeys without step‐up dosing. In conclusion, combination of odronextamab in vitro cytokine data, efficacious concentration data from mouse tumor models, and pharmacokinetic evaluations in monkeys has translational value to inform odronextamab FIH study design in patients with R/R B‐NHL.

Non-human primates in the PKPD evaluation of biologics: Needs and options to reduce, refine, and replace. A BioSafe White Paper

Monoclonal antibodies (mAbs) deliver great benefits to patients with chronic and/or severe diseases thanks to their strong specificity to the therapeutic target. As a result of this specificity, non-human primates (NHP) are often the only preclinical species in which therapeutic antibodies cross-react with the target. Here, we highlight the value and limitations that NHP studies bring to the design of safe and efficient early clinical trials. Indeed, data generated in NHPs are integrated with in vitro information to predict the concentration/effect relationship in human, and therefore the doses to be tested in first-in-human trials. The similarities and differences in the systems defining the pharmacokinetics and pharmacodynamics (PKPD) of mAbs in NHP and human define the nature and the potential of the preclinical investigations performed in NHPs. Examples have been collated where the use of NHP was either pivotal to the design of the first-in-human trial or, inversely, led to the termination of a project prior to clinical development. The potential impact of immunogenicity on the results generated in NHPs is discussed. Strategies to optimize the use of NHPs for PKPD purposes include the addition of PD endpoints in safety assessment studies and the potential re-use of NHPs after non-terminal studies or cassette dosing several therapeutic agents of interest. Efforts are also made to reduce the use of NHPs in the industry through the use of in vitro systems, alternative in vivo models, and in silico approaches. In the case of prediction of ocular PK, the body of evidence gathered over the last two decades renders the use of NHPs obsolete. Expert perspectives, advantages, and pitfalls with these alternative approaches are shared in this review.

Pharmacokinetic/pharmacodynamic modeling for dose selection for the first-in-human trial of the activated Factor XII inhibitor garadacimab (CSL312)

Factor XII (FXII) is a serine protease involved in multiple cascades, including the kallikrein–kinin system. It may play a role in diseases in which the downstream cascades are dysregulated, such as hereditary angioedema. Garadacimab (CSL312) is a first‐in‐class, fully human, monoclonal antibody targeting activated FXII (FXIIa). We describe how translational pharmacokinetic (PK) and pharmacodynamic (PD) modeling enabled dose selection for the phase I, first‐in‐human trial of garadacimab. The PK/PD data used for modeling were derived from preclinical PK/PD and safety studies. Garadacimab plasma concentrations rose with increasing dose, and clear dose‐related PD effects were observed (e.g., a mechanism‐based prolongation of activated partial thromboplastin time). The PK/PD profile from cynomolgus monkeys was used to generate minimal physiologically‐based pharmacokinetic (mPBPK) models with target‐mediated drug disposition (TMDD) for data prediction in cynomolgus monkeys. These models were later adapted for prediction of human data to establish dose selection. Based on the final mPBPK model with TMDD and assuming a weight of 70 kg for an adult human, a minimal inhibition (<10%) of FXIIa with a starting dose of 0.1 mg/kg garadacimab and a near maximal inhibition (>95%) at 10 mg/kg garadacimab were predicted. The phase I study is complete, and data on exposure profiles and inhibition of FXIIa‐mediated kallikrein activity observed in the trial support and validate these simulations. This emphasizes the utility and relevance of translational modeling and simulation in drug development.

REGN1908-1909 monoclonal antibodies block Fel d 1 in cat allergic subjects: Translational pharmacokinetics and pharmacodynamics

REGN1908‐1909, a 1:1 cocktail of two fully human IgG₄ monoclonal antibodies (mAbs), REGN1908 and REGN1909, is being evaluated for treatment of cat allergy. Both REGN1908 and REGN1909 bind to the dominant cat allergen, Fel d 1. Adults with cat allergy confirmed by skin prick test (SPT) were randomized to single subcutaneous administration of placebo (n = 6) or REGN1908‐1909 at doses of 150 (n = 6), 300 (n = 6), or 600 mg (n = 6). Blood samples were taken at prespecified time points for pharmacokinetic (PK) analysis and exploratory evaluation of biomarkers (IgE and SPT). Safety was assessed. Drug concentration‐time profiles in serum for ascending doses of REGN1908‐1909 were consistent with linear PKs. Noncompartmental analysis showed that maximum concentration (C_max) and exposure increased proportionately with dose, with similar time to maximum concentration (T_max) for REGN1908 and REGN1909 (6.2 to 8.2 days across doses), and a longer terminal half‐life for REGN1908 (~ 30 days) relative to REGN1909 (~ 21 days). Adverse events were not dose dependent; there were no dose‐limiting toxicities. REGN1908‐1909 is characterized by linear and dose‐proportional kinetics of the two individual mAb components. A single 600 mg dose maintains total mAb mean concentrations in serum above the target (mean of ~ 10 mg/L) for 8–12 weeks. Maintaining this mean target concentration resulted in translational pharmacodynamic effects: maximal mast cell degranulation in a passive cutaneous anaphylaxis mouse model, and maintenance of clinical efficacy measured by Total Nasal Symptom Score in a previous proof‐of‐mechanism study.

Multiscale pharmacokinetic modeling of systemic exposure of subcutaneously injected biotherapeutics

Subcutaneously injected formulations have been developed for many biological products including monoclonal antibodies (mAbs). A knowledge gap nonetheless remains regarding the absorption and catabolism mechanisms and kinetics of a large molecule at the administration site. A multiscale pharmacokinetic (PK) model was thus developed by coupling multiphysics simulations of subcutaneous (SC) absorption kinetics with whole-body pharmacokinetic (PK) modeling, bridged by consideration of the presystemic clearance by the initial lymph. Our local absorption simulation of SC-injected albumin enabled the estimation of its presystemic clearance and led to the whole-body PK modeling of systemic exposure. The local absorption rate of albumin was found to be influential on the PK profile. Additionally, nineteen mAbs were explored via this multiscale simulation and modeling framework. The computational results suggest that stability propensities of the mAbs are correlated with the presystemic clearance, and electrostatic charges in the complementarity-determining region influence the local absorption rate. Still, this study underscores a critical need to experimentally determine various biophysical characteristics of a large molecule and the biomechanical properties of human skin tissues.

Comparison of Various Approaches to Translate Non-Linear Pharmacokinetics of Monoclonal Antibodies from Cynomolgus Monkey to Human

BACKGROUND AND OBJECTIVES

The prediction of pharmacokinetics of monoclonal antibodies (mAbs) exhibiting non-linear pharmacokinetics in preclinical species to human is challenging, and very limited scientific work has been published in this field of research. Therefore, we have conducted an elaborate comparative assessment to determine the most reliable preclinical to clinical scaling strategy for mAbs with non-linear pharmacokinetics.

METHODS

We have compared three different scaling approaches to predict human pharmacokinetics from cynomolgus monkey. In the first approach, cynomolgus monkey pharmacokinetic parameters estimated using a two-compartment model with parallel linear and non-linear elimination were allometrically scaled to simulate human pharmacokinetics. In the second approach, allometric exponents were integrated with a minimal physiologically based pharmacokinetic (mPBPK) model to translate human pharmacokinetics. In the third approach, we have employed a species time-invariant method, wherein a two-compartment model with parallel linear and non-linear elimination was used as a framework model for simulation of the human profile.

RESULTS

Human exposure parameters projected by an integrated allometric method were only within two fold for approximately 45-70% of predictions at different doses of five mAbs evaluated, while approximately 70-80% of Cmax and AUC predictions by integrated mPBPK modelling as well as the species time-invariant method were within two-fold error. The average fold error for clearance predictions by the integrated mPBPK method was 1.10-1.45 fold, whilst for the species time-variant and integrated allometric methods, the average fold error was between 1.04 and 1.37 fold and 1.24 and 2.13 fold, respectively.

CONCLUSIONS

Our findings suggest that the species time-variant method and mPBPK proposed by us can be employed to reliably translate non-linear pharmacokinetics of mAbs from cynomolgus monkey to human.

Pediatric Dose Selection for Therapeutic Proteins

In selecting optimal dosing regimens in support of the clinical use of monoclonal antibodies and other therapeutic proteins in pediatric indications, the unique pharmacokinetic properties of this class of biologics, as well as the underlying physiologic and pathophysiologic processes and their modulation by childhood growth and development, needs to be appreciated. During drug development, first-in-pediatric dose selection is a capstone event in the pediatric investigation plan that relies heavily on extrapolation of pharmacokinetic and pharmacodynamic data from adult to pediatric populations. It is facilitated by combinations of pharmacometric approaches, including allometry, physiologically based pharmacokinetic modeling, and population pharmacokinetic analyses, although data on reliability and qualification of some of these tools in the context of therapeutic proteins are still limited but emerging. Presented data suggest nonlinear relationships between body weight and both clearance and volume of distribution for therapeutic proteins in pediatric populations, with allometric exponents of 0.75 and 0.8, respectively. For newborns and infants (<1 year), even higher nonlinearity seems to occur. Translation of the quantitative characterization of the pediatric pharmacokinetics of therapeutic proteins into dosing regimens for the drug label requires compromising between precision dosing and clinical practicability, with tiered dosing algorithms based on size or age strata being the currently most frequently applied methodology.

Translational PK/PD and model-informed development of JNJ-67842125, a Fab reversal agent for JNJ-64179375, a long-acting thrombin inhibitor

BACKGROUND AND PURPOSE

Antigen-binding fragment (F_ab ) reversal agents were developed to reverse, in bleeding emergency, the long-acting anticoagulant effect of JNJ-64179375 (JNJ-9375), a monoclonal antibody that binds exosite-1 on thrombin.

EXPERIMENTAL APPROACH

The pharmacokinetic and pharmacodynamic (PK/PD) activities of three reversal agents of varying in vitro binding affinities to JNJ-9375 were characterised in cynomolgus monkeys. The time course of JNJ-9375 anticoagulant activity and reversal effects of each agent were evaluated. A mechanism-based PK/PD model, which integrated free serum concentrations of reversal agent, total and free serum concentrations of JNJ-9375, and thrombin time, was developed to quantitatively relate JNJ-9375 neutralisation to reversal of induced thrombin time prolongation. Model-based allometric scale-up of the lead reversal agent and the PK/PD relationship of JNJ-9375 in healthy volunteers were utilised to predict clinical dosing regimens.

KEY RESULTS

Lowering of free JNJ-9375 by the reversal agents corresponded with reversal of thrombin time prolongation. Total JNJ-9375 displayed typical mAb clearance at 2.75 ml·day^-1 ·kg^-1 , whereas reversal agents cleared faster between 1400 and 2400 ml·day^-1 ·kg^-1 . The model-estimated in vivo K_D values for JNJ-9375 reversal agents were 9 nM (ICHB-256), 0.4 nM (ICHB-281) and 13.7 pM (ICHB-164), in rank-ordered agreement of their K_D values determined in vitro. The three reversal agents exhibited different neutralisation characteristics in vivo, governed primarily by their binding kinetics to JNJ-9375. The model predicted a priori free JNJ-9375 kinetics after dosing ICHB-164 (JNJ-67842125) and JNJ-9375 under a different regimen.

CONCLUSION AND IMPLICATIONS

The results enabled selection of JNJ-67842125 as the reversal agent for JNJ-9375.

The neutralizing antibody, LY-CoV555, protects against SARS-CoV-2 infection in nonhuman primates

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) poses a public health threat for which preventive and therapeutic agents are urgently needed. Neutralizing antibodies are a key class of therapeutics that may bridge widespread vaccination campaigns and offer a treatment solution in populations less responsive to vaccination. Here, we report that high-throughput microfluidic screening of antigen-specific B cells led to the identification of LY-CoV555 (also known as bamlanivimab), a potent anti-spike neutralizing antibody from a hospitalized, convalescent patient with coronavirus disease 2019 (COVID-19). Biochemical, structural, and functional characterization of LY-CoV555 revealed high-affinity binding to the receptor-binding domain, angiotensin-converting enzyme 2 binding inhibition, and potent neutralizing activity. A pharmacokinetic study of LY-CoV555 conducted in cynomolgus monkeys demonstrated a mean half-life of 13 days and a clearance of 0.22 ml hour-1 kg-1, consistent with a typical human therapeutic antibody. In a rhesus macaque challenge model, prophylactic doses as low as 2.5 mg/kg reduced viral replication in the upper and lower respiratory tract in samples collected through study day 6 after viral inoculation. This antibody has entered clinical testing and is being evaluated across a spectrum of COVID-19 indications, including prevention and treatment.

Estimation of Clearance and Bioavailability of Therapeutic Monoclonal Antibodies from Only Subcutaneous Injection Data in Humans Based on Comprehensive Analysis of Clinical Data

Introduction

Theoretically, the separate estimation of clearance (CL) and bioavailability (F) requires both intravenous and extravascular injection data. This study investigated whether CL and subcutaneous F of therapeutic monoclonal antibodies (mAbs) in humans can be separately estimated from subcutaneous injection data only.

Methods

First, the geometric mean of linear pharmacokinetic parameters (CL, intercompartmental CL [Q], volume of distribution in the central compartment [V_c], and volume of distribution in the peripheral compartment [V_p]) after intravenous injection for mAbs in humans that have been reported in public data sources was estimated from 103 mAbs with linear pharmacokinetics and 44 mAbs with nonlinear pharmacokinetics. Next, we estimated the CL and F of 25 mAbs with linear pharmacokinetics from plasma/serum mAb concentration–time profiles after subcutaneous injection in humans by fixing the geometric mean of Q, V_c, and V_p based on the public data. Moreover, the plasma/serum concentration–time profile of 25 mAbs after intravenous injection was simulated using the estimated CL and the geometric mean of Q, V_c, and V_p.

Results

There were no significant differences in parameters among subclasses (immunoglobulin [Ig] G1, 2, and 4) or in linearity (derivation from linear and nonlinear pharmacokinetics). Using only subcutaneous injection data, we successfully estimated the CL of 23/25 mAbs (92%) and F of all 25 mAbs (100%) within 1.5-fold of the observed value. Moreover, overall, the simulated concentration–time profiles were largely consistent with observed data (90.8% within 1.5-fold of the observed values).

Conclusions

This approach does not require intravenous injection data to separately estimate CL and F after subcutaneous injection in humans and can therefore accelerate the clinical development of mAbs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01023-z.

Recent Achievements and Challenges in Prolonging the Serum Half-Lives of Therapeutic IgG Antibodies Through Fc Engineering

Association of FcRn molecules to the Fc region of IgG in acidified endosomes and subsequent dissociation of the interaction in neutral pH serum enables IgG molecules to be recycled for prolonged serum persistence after internalization by endothelial cells, rather than being degraded in the serum and in the lysosomes inside the cells. Exploiting this intracellular trafficking and recycling mechanism, many researchers have engineered the Fc region to further extend the serum half-lives of therapeutic antibodies by optimizing the pH-dependent IgG Fc-FcRn interaction, and have generated various Fc variants exhibiting significantly improved circulating half-lives of therapeutic IgG antibodies. In order to estimate pharmacokinetic profiles of IgG Fc variants in human serum, not only a variety of in vitro techniques to determine the equilibrium binding constants and instantaneous rate constants for pH-dependent FcRn binding, but also diverse in vivo animal models including wild-type mouse, human FcRn transgenic mouse (Tg32 and Tg276), humanized mouse (Scarlet), or cynomolgus monkey have been harnessed. Currently, multiple IgG Fc variants that have been validated for their prolonged therapeutic potency in preclinical models have been successfully entered into human clinical trials for cancer, infectious diseases, and autoimmune diseases.

Improving priors for human monoclonal antibody linear pharmacokinetic parameters by using half-lives from non-human primates

Obtaining a good prior for the linear pharmacokinetics of new monoclonal antibodies (mAbs) would be an advantage not only for designing first-in-human (FIH) studies but also for stabilizing fitting of data with non-linear target-mediated disposition models. We estimated the pharmacokinetics from FIH studies for five mAbs using a two-compartment model, both separately and together, using a simple pool, a third hierarchical level of random effects for between mAb differences and non-human-primate half-lives as a predictor covariate for said differences. There was good agreement between compounds for the rapidly accessible central volume of 2.9 L (70 kg human), but clearances and peripheral volumes differed with terminal half-lives ranging from 15 to 28 days. The simple pool of human studies gave inter-individual variability estimates of 32% coefficient of variation (CV) for clearance and 33% CV for peripheral volume, larger than for separate fits (13-26% CV and 15-35% CV for clearance and volume respectively). Using third level hierarchical random effects gave inter-individual variability estimates close to those of separate fits (24% and 16% CV respectively). The between-mAb differences became predictable if non-human primate body weight scaled terminal half-life estimates were included as covariates on clearance and peripheral volume. In conclusion, ignoring inter-mAb variation leads to inflated estimates of inter-individual variability and unrealistic simulations for FIH studies. However, by using 70 kg body weight scaled terminal half-life estimates from non-human primates one can account for between-mAb differences and provide non-inflated priors for the linear pharmacokinetic parameters of new mAbs.

Allometric scaling of therapeutic monoclonal antibodies in preclinical and clinical settings

Constant technological advancement enabled the production of therapeutic monoclonal antibodies (mAbs) and will continue to contribute to their rapid expansion. Compared to small-molecule drugs, mAbs have favorable characteristics, but also more complex pharmacokinetics (PK), e.g., target-mediated nonlinear elimination and recycling by neonatal Fc-receptor. This review briefly discusses mAb biology, similarities and differences in PK processes across species and within human, and provides a detailed overview of allometric scaling approaches for translating mAb PK from preclinical species to human and extrapolating from adults to children. The approaches described here will remain vital in mAb drug development, although more data are needed, for example, from very young patients and mAbs with nonlinear PK, to allow for more confident conclusions and contribute to further growth of this field. Improving mAb PK predictions will facilitate better planning of (pediatric) clinical studies and enable progression toward the ultimate goal of expediting drug development.

Pharmacokinetic prediction of an antibody in mice based on an in vitro cell-based approach using target receptor-expressing cells

In vivo pharmacokinetics (PK) studies using mice and monkeys are the main approaches for evaluating and predicting the PK of antibodies, and there is a strong demand for methods that do not require animal experiments. In this work, we focused on quantitatively predicting the nonlinear PK of an antibody based on cell-based assays. An anti-mouse Fc gamma receptor IIB antibody was used as a model antibody. To determine the PK parameters related to nonspecific elimination in vivo, the plasma concentration profile at 100 mg/kg, at which target-specific clearance is saturated, was analyzed by a 2-compartment model. To estimate the parameters related to target-specific elimination, the Michaelis–Menten constant (K_m) and the maximum elimination rate (V_max) were determined by an uptake assay using Chinese hamster ovary (CHO) cells expressing the target receptor. Finally, the integration of all of these parameters permitted the PK to be predicted at doses ranging from 1 to 100 mg/kg regardless of whether target-specific clearance was saturated or nonsaturated. The findings presented herein show that in vitro assays using target-expressing cells are useful tools for obtaining PK parameters and predicting PK profiles and, in some cases, eliminate the need for in vivo PK studies using experimental animals.

Simple Approach to Accurately Predict Pharmacokinetics of Therapeutic Monoclonal Antibodies after Subcutaneous Injection in Humans

BACKGROUND AND OBJECTIVE

The subcutaneous injection of therapeutic monoclonal antibodies is increasingly used in the treatment of several diseases because of its convenience. Thus, a simple and accurate method of predicting the pharmacokinetics of monoclonal antibodies after a subcutaneous injection in humans would be a valuable tool for preclinical/clinical development. In this study, we investigated whether the pharmacokinetics of monoclonal antibodies after a subcutaneous injection in humans can be predicted using only pharmacokinetic data after a subcutaneous injection in cynomolgus monkeys.

METHODS

First, we compared the accuracy of three approaches to predict the apparent clearance (CL/F) and apparent volume of distribution (V_d/F) for 15 monoclonal antibodies in humans (1) allometric scaling from cynomolgus monkeys; (2) geometric mean of reported values in humans; (3) estimation from a regression line based on CL/F in humans [only V_d/F]). Then, using the predicted CL/F and V_d/F, and the geometric mean of reported absorption rate constant of mAbs the plasma concentration-time profiles of 13 monoclonal antibodies after subcutaneous injections in humans were simulated.

RESULTS

In a comparison of approaches, the first approach showed the best prediction accuracy for CL/F with an exponent of 0.9 (100% and 73% prediction accuracy within 2- and 1.5-fold of the observed value),and the third approach was the best for V_d/F (100% prediction accuracy within 1.5-fold of the observed value). Next, using the first approach for CL/F and the third approach for V_d/F, we accurately predicted the plasma concentration-time profiles of 13 monoclonal antibodies after subcutaneous injections in humans.

CONCLUSION

This simple approach can be applied in preclinical and clinical settings to predict the pharmacokinetics of monoclonal antibodies after subcutaneous injections in humans. Further, this approach requires only CL/F after a subcutaneous injection in cynomolgus monkeys, contributing to animal welfare and reducing costs.

Subcutaneous Site-of-Absorption Study with the Monoclonal Antibody Tocilizumab in Minipigs: Administration Behind Ear Translates Best to Humans

Minipigs have been proposed as animal model to study the subcutaneous (SC) absorption of monoclonal antibodies (mAb), because they are more translatable to humans than other species. However, the minipig SC tissue structure differs markedly depending on its location. This study explored different SC administration sites for mAb SC administration, to explore which site translates best to humans. The study assessed the SC absorption of tocilizumab (Actemra®) following administration at several injection sites: Inguinal area, flank, caudal to the ear, and interscapular area, in comparison with an IV group. After SC administration, tocilizumab absorption was most rapid from the inguinal administration site, and slowest after administration behind the ear, with absorption from the other sites in between. Tocilizumab bioavailability was 98.6, 88.3, 74.1, and 86.3% after administration in inguinal area, flank, behind the ear, and interscapular area, as determined by non-compartmental analysis. Fitting of a single first-order absorption rate constant by compartmental analysis was dissatisfactory. A combined fitting of all data was done assuming two different kinds of SC depots, one undergoing fast absorption, the other undergoing a slower absorption. The split between these absorption depots differed across administration sites, with absorption from "fast depot" in inguinal area > flank > interscapular area > behind the ear. Comparisons with clinical data show that tocilizumab PK after SC administration behind the ear translates best to humans, considering both bioavailability and rate of absorption. Whether this translation from minipigs to humans is prototypic for other mAb remains to be confirmed.

New insights into the vancomycin-induced nephrotoxicity using in vitro metabolomics combined with physiologically based pharmacokinetic modeling

Vancomycin is a first-line treatment for invasive infections caused by multidrug-resistant gram-positive bacteria. However, vancomycin-induced nephrotoxicity is an increasing burden, particularly in patients with complex life-threatening conditions. Vancomycin-induced nephrotoxicity associated with clinically relevant exposure on the target site has not been well defined. This study aimed to acquire the concentration of vancomycin in the renal tubules and kidneys in humans using physiologically based pharmacokinetic (PBPK) modeling and simulation. Based upon the exposure of vancomycin in the renal tubule, the toxicity of vancomycin in human renal proximal tubular epithelial cells was examined with the XTT assay and in vitro metabolomics analysis. A rat PBPK model predicting plasma and kidney concentration-time profiles of vancomycin matched the observed behavior after a single administration of 10 mg/kg. The concentration of vancomycin in renal tubules was about 40-50 times higher than that in plasma. The human PBPK model transferred from the rat model predicted renal tubule concentrations of vancomycin as 316.1-2136.6 μg/mL at 500 mg every 6 hours, and 199.0-3932.5 μg/mL at 1000 mg every 12 hours. Vancomycin showed significant nephrotoxicity at 4 mg/mL in XTT assessment. In total, 11 lysophosphatidylcholines and one lysophosphatidylethanolamine were identified by metabolomics analysis. The concentration-dependent increase was evident in the release of lysophospholipids after vancomycin treatment (0.125-4 mg/mL) for 24 hours. Our study revealed the relationship between the exposure of vancomycin in the kidney and toxicity of vancomycin at clinically relevant concentrations achieved from a mechanical PBPK model. A series of lysophospholipids as potential metabolic markers of renal toxicity were identified.

Dose Correction for a Michaelis-Menten Approximation of a Target-Mediated Drug Disposition Model with a Multiple Intravenous Dosing Regimens

This study aimed to develop a method for implementing dose correction in a Michaelis-Menten (M-M) approximation of a target-mediated drug disposition (TMDD) model with multiple intravenous (IV) bolus administrations. We derived the formula of a correction factor (Fcorr) for each dose in a multiple IV bolus dosing regimens for M-M model. Fcorr depends on the residual free drug amount prior IV bolus dosing event and dose amount. We conducted a stochastic simulation and estimation (SSE) exercise based on therapeutic antibody PK parameters to evaluate the effect of Fcorr on parameter estimation. Previously published clinical PK data of recombinant human erythropoietin (rHuEPO) from four clinical trials in healthy subjects receiving multiple IV bolus doses were analyzed by both M-M model with and without dose correction (MMC and MMNC) as well as the rapid-binding/quasi-steady-state (RB/QSS) TMDD models. Our results showed that MMNC introduced bias to fixed-effect parameter estimates and overestimated random-effect variables. Compared with MMC, MMNC was not able to adequately characterize the nonlinearity in the PK data of antibody and rHuEPO. The MMC-based simulation demonstrated that thricely weekly 10 IU/kg rHuEPO dosing regimen yielded Fcorr = 0.5. This result suggested that the lower-than-expected exposure for rHuEPO at low dose is due to target binding. An M-M approximation of the TMDD model should include a dose correction to avoid model misfitting and potential bias in the estimated PK parameters.

Target-Mediated Drug Disposition Pharmacokinetic/Pharmacodynamic Model-Informed Dose Selection for the First-in-Human Study of AVB-S6-500

AVB-S6-500 neutralized growth arrest-specific 6 (GAS6) protein and effectively inhibited AXL signaling in preclinical cancer models. A target-mediated drug disposition (TMDD) pharmacokinetic/pharmacodynamic (PK/PD) model was used to select first-in-human (FIH) doses for AVB-S6-500 based on predicted target (GAS6) suppression in the clinic. The effect of TMDD on AVB-S6-500 clearance was incorporated into a standard two-compartment model, providing parallel linear and nonlinear clearance. Observed AVB-S6-500 and GAS6 concentration data in cynomolgus monkeys and relevant interspecies differences were used to predict the PK (serum concentration)/PD (GAS6 suppression) relationship in humans. Human exposure and GAS6 suppression were simulated for the proposed FIH doses of 1, 2.5, 5, and 10 mg/kg. A dose of 1 mg/kg was selected to target GAS6 suppression for 2 weeks in the initial healthy volunteer study. The cynomolgus monkey:human ratios for the highest proposed FIH dose were anticipated to yield more than a 10-fold margin to the nonclinical no observed adverse event level while maintaining > 90% GAS6 suppression. In human subjects, the first dose (1 mg/kg) model-projected and clinically observed maximal concentration (Cmax ) was within 10% of predicted; repeat dosing at 5 mg/kg was within 1% (Cmax ) and 45% (area under the serum concentration-time curve from time 0 to end of dosing interval) of predicted. Predicted GAS6 suppression duration of 14 days was accurate for the 1 mg/kg dose. A PK/PD model expedited clinical development of AVB-S6-500, minimized exposure of patients with cancer to subtherapeutic doses, and rationally guided the optimal dosing in patients.

Clinical and Pharmacologic Features of Monoclonal Antibodies and Checkpoint Blockade Therapy in Multiple Myeloma

Background:

Survival of multiple myeloma patients has considerably improved in the last decades thanks to the introduction of many new drugs, including immunomodulatory agents, proteasome inhibitors and, more recently, monoclonal antibodies.

Methods:

We analyzed the most recent literature focusing on the clinical and pharmacologic aspects of monoclonal antibody-based therapies in multiple myeloma, including monoclonal antibodies directed against plasma cell antigens, as well as checkpoint blockade therapy directed against immune inhibitory molecules, used as single agents or in combination therapy.

Results:

Anti-CD38 monoclonal antibodies including daratumumab, isatuximab and MOR202 have shown outstanding results in relapsed and/or refractory multiple myeloma patients. The addition of daratumumab to bortezomib-dexamethasone or lenalidomidedexamethasone substantially improved patients’ outcome in this patient population. The anti- SLAMF7 molecule elotuzumab in combination with lenalidomide-dexamethasone showed to be superior to lenalidomide-dexamethasone alone, without adding meaningful toxicity. Checkpoint blockade therapy in combination with immunomodulatory agents produced objective responses in more than 50% of treated patients. However, this combination was also associated with an increase in toxicity and a thorough safety evaluation is currently ongoing.

Conclusion:

Monoclonal antibodies are reshaping the standard of care for multiple myeloma and ongoing trials will help physicians to optimize their use in order to further improve patients’ outcome.

Assessment and Confirmation of Species Difference in Nonlinear Pharmacokinetics of Atipamezole with Physiologically Based Pharmacokinetic Modeling

Atipamezole, an α ₂-adrenoceptor antagonist, displayed nonlinear pharmacokinetics (PK) in rats. The aim of this study was to understand the underlying mechanisms of nonlinear PK in rats and linear PK in humans and develop physiologically based PK models (PBPK) to capture and validate this phenomenon. In vitro and in vivo data were generated to show that metabolism is the main clearance pathway of atipamezole and species differences exist. Where cytochrome P450 (P450) was responsible for the metabolism in rats with a low Michaelis constant, human-specific UDP-glucuronosyltransferase 2B10- and 1A4-mediated N-glucuronidation was identified as the leading contributor to metabolism in humans with a high V _max capacity. Saturation of metabolism was observed in rats at pharmacologically relevant doses, but not in humans at clinically relevant doses. PBPK models were developed using GastroPlus software to predict the PK profile of atipamezole in rats after intravenous or intramuscular administration of 0.1 to 3 mg/kg doses. The model predicted the nonlinear PK of atipamezole in rats and predicted observed exposures within 2-fold across dose levels. Under the same model structure, a human PBPK model was developed using human in vitro metabolism data. The PBPK model well described human concentration-time profiles at 10-100 mg doses showing dose-proportional increases in exposure. This study demonstrated that PBPK is a useful tool to predict human PK when interspecies extrapolation is not applicable. The nonlinear PK in rat and linear PK in human were characterized in vitro and allowed the prospective human PK via intramuscular dosing to be predicted at the preclinical stage. SIGNIFICANCE STATEMENT: This study demonstrated that PBPK is a useful tool for predicting human PK when interspecies extrapolation is not applicable due to species unique metabolism. Atipamezole, for example, is metabolized by P450 in rats and by N-glucuronidation in humans that were hypothesized to be the underlying reasons for a nonlinear PK in rats and linear PK in humans. This was testified by PBPK simulation in this study.

A Physiologically-Based Pharmacokinetic Model for the Prediction of Monoclonal Antibody Pharmacokinetics From In Vitro Data

Monoclonal antibody (mAb) pharmacokinetics (PK) have largely been predicted via allometric scaling with little consideration for cross-species differences in neonatal Fc receptor (FcRn) affinity or clearance/distribution mechanisms. To address this, we developed a mAb physiologically-based PK model that describes the intracellular trafficking and FcRn recycling of mAbs in a human FcRn transgenic homozygous mouse and human. This model uses mAb-specific in vitro data together with species-specific FcRn tissue expression, tissue volume, and blood-flow physiology to predict mAb in vivo linear PK a priori. The model accurately predicts the terminal half-life of 90% of the mAbs investigated within a twofold error. The mechanistic nature of this model allows us to not only predict linear PK from in vitro data but also explore the PK and target binding of mAbs engineered to have pH-dependent binding to its target or FcRn and could aid in the selection of mAbs with optimal PK and pharmacodynamic properties.

PKPD Assessment of the Anti-CD20 Antibody Obinutuzumab in Cynomolgus Monkey is Feasible Despite Marked Anti-Drug Antibody Response in This Species

The pharmacokinetics (PK) of the anti-CD20 monoclonal antibody obinutuzumab was assessed after single intravenous dosing to cynomolgus monkeys. In addition, the pharmacokinetic-pharmacodynamic (PKPD) relationship for B-cell depletion was characterized. The PKPD model was used to estimate the B-cell repopulation during the recovery phase of chronic toxicology studies, thereby supporting the study design, in particular planning the recovery phase duration. Marked immunogenicity against obinutuzumab was observed approximately 10 days after single dose, leading to an up to ∼30-fold increase in obinutuzumab clearance in the affected monkeys. Despite this accelerated clearance, the PK could be characterized, either by disregarding the clearance in noncompartmental PK analysis or by capturing it explicitly as an additional time-dependent clearance process in compartmental modeling. This latter step was crucial to model the PKPD of B-cells as an indirect response to obinutuzumab exposure, showing that-without immune response-the limiting factor is obinutuzumab elimination with concentrations below 0.02 μg/mL required for initiation of B-cell recovery. Overall, the results demonstrate that despite a marked anti-drug antibody response in the nonclinical animal species, the PK and PKPD of obinutuzumab could be characterized successfully by appropriately addressing the immune-modulated clearance pathway in data analysis and modeling.

Quantitative Systems Pharmacology Model of a Masked, Tumor-Activated Antibody

PROBODY therapeutics (Pb‐Tx) are protease‐activatable prodrugs of monoclonal antibodies (mAbs) designed to target tumors where protease activity is elevated while avoiding normal tissue. They are composed of a parental mAb, a mask that inhibits antibody binding to target, and a protease‐cleavable substrate between the mask and the mAb. We report a quantitative systems pharmacology model for the rational design and clinical translation of Pb‐Tx. The model adequately described monkey pharmacokinetic data following the administration of six anti‐CD166 Pb‐Tx of varying mask strength and substrate cleavability and captured the trend of decreasing Pb‐Tx systemic clearance with increasing mask strength. Projections to humans suggested both higher levels of Pb‐Tx in tumor relative to parental mAb and an optimal mask strength for maximizing tumor receptor–mediated uptake. Simulations further suggested the majority of circulating species in humans would be intact/masked Pb‐Tx, with no significant flux of cleaved/activated species from tumor to the systemic compartment.

Preclinical and translational pharmacokinetics of a novel THIOMAB™ antibody-antibiotic conjugate against Staphylococcus aureus

DSTA4637S, a novel THIOMAB™ antibody-antibiotic conjugate (TAC) against Staphylococcus aureus (S. aureus), is currently being investigated as a potential therapy for complicated S. aureus bloodstream infections. DSTA4637S is composed of a monoclonal THIOMAB^TM IgG1 recognizing S. aureus linked to a rifamycin-class antibiotic (dmDNA31) via a protease-cleavable linker. The pharmacokinetics (PK) of DSTA4637A (a liquid formulation of DSTA4637S) and its unconjugated antibody MSTA3852A were characterized in rats and monkeys. Systemic concentrations of three analytes, total antibody (TAb), antibody-conjugated dmDNA31 (ac-dmDNA31), and unconjugated dmDNA31, were measured to describe complex TAC PK in nonclinical studies. In rats and monkeys, following intravenous administration of a single dose of DSTA4637A, systemic concentration-time profiles of both TAb and ac-dmDNA31 were bi-exponential, characterized by a short distribution phase and a long elimination phase as expected for a monoclonal antibody-based therapeutic. Systemic exposures of both TAb and ac-dmDNA31 were dose proportional over the dose range tested, and ac-dmDNA31 cleared 2-3 times faster than TAb. Unconjugated dmDNA31 plasma concentrations were low (<4 ng/mL) in every study regardless of dose. In this report, an integrated semi-mechanistic PK model for two analytes (TAb and ac-dmDNA31) was successfully developed and was able to well describe the complicated DSTA4637A PK in mice, rats and monkeys. DSTA4637S human PK was predicted reasonably well using this model with allometric scaling of PK parameters from monkey data. This work provides insights into PK behaviors of DSTA4637A in preclinical species and informs clinical translatability of these observed results and further clinical development. Abbreviations: ADC: Antibody-drug conjugate; AUC_inf: time curve extrapolated to infinity; ac-dmDNA31: antibody-conjugated dmDNA31; C_max: maximum concentration observed; DAR: drug-to-antibody ratio; CL: clearance; CL_D: distribution clearance; CL₁: systemic clearance of all DAR species; k_DC: deconjugation rate constant; PK: Pharmacokinetics; IV: Intravenous; IgG: Immunoglobulin G; mAb: monoclonal antibody; S. aureus: Staphylococcus aureus; TAC: THIOMAB^TM antibody-antibiotic conjugate; TDC: THIOMAB^TM antibody-drug conjugate; TAb: total antibody; t_{1/2, λz}: terminal half-life; vc linker: valine-citrulline linker; V_ss: volume of distribution at steady state; V_c: volume of distribution for the central compartment; V_p: the volume of distribution for the peripheral compartment.

Prediction of Human Nonlinear Pharmacokinetics of a New Bcl-2 Inhibitor Using PBPK Modeling and Interspecies Extrapolation Strategy

S 55746 ((S)-N-(4-hydroxyphenyl)-3-(6-(3-(morpholinomethyl)-1,2,3,4-tetrahydroisoquinoline-2-carbonyl)benzo[d][1,3]dioxol-5-yl)-N-phenyl-5,6,7,8-tetrahydroindolizine-1-carboxamide) is a new selective Bcl-2 (B-cell lymphoma 2) inhibitor developed by Servier Laboratories and used to restore apoptosis functions in cancer patients. The aim of this work was to develop a translational approach using physiologically based (PB) pharmacokinetic (PK) modeling for interspecies extrapolation to anticipate the nonlinear PK behavior of this new compound in patients. A PBPK mouse model was first built using a hybrid approach, defining scaling factors (determined from in vitro data) to correct in vitro clearance parameters and predicted Kp (partition coefficient) values. The qualification of the hybrid model using these empirically determined scaling factors was satisfactorily completed with rat and dog data, allowing extrapolation of the PBPK model to humans. Human PBPK simulations were then compared with clinical trial data from a phase 1 trial in which the drug was given orally and daily to cancer patients. Human PBPK predictions were within the 95% prediction interval for the eight dose levels, taking into account both the nonlinear dose and time dependencies occurring in S 55746 kinetics. Thus, the proposed PK interspecies extrapolation strategy, based on preclinical and in vitro information and physiologic assumptions, could be a useful tool for predicting human plasma concentrations at the early stage of drug development.

Design and Conduct Considerations for First-in-Human Trials

A milestone step in translational science to transform basic scientific discoveries into therapeutic applications is the advancement of a drug candidate from preclinical studies to initial human testing. First-in-human (FIH) trials serve as the link to advance new promising drug candidates and are conducted primarily to determine the safe dose range for further clinical development. Cross-functional collaboration is essential to ensure efficient and successful FIH trials. The aim of this publication is to serve as a tutorial for conducting FIH trials for both small molecule and biological drug candidates with topics covering regulatory requirements, preclinical safety testing, study design considerations, safety monitoring, biomarker assessment, and global considerations. An emphasis is placed on FIH trial design considerations, including starting dose selection, study size and population, dose escalation scheme, and implementation of adaptive designs. In light of the recent revision of the European Medicines Agency (EMA) guideline on FIH trials to promote safety and mitigate risk, we also discuss new measures introduced in the guideline that impact FIH trial design.

Pharmacokinetics, Pharmacodynamics, and Safety of E6011, a Novel Humanized Antifractalkine (CX3CL1) Monoclonal Antibody: A Randomized, Double-Blind, Placebo-Controlled Single-Ascending-Dose Study

E6011 is a novel humanized antifractalkine (FKN) monoclonal antibody being developed as a therapeutic target for Crohn's disease, rheumatoid arthritis, and primary biliary cholangitis. This study was a randomized, double-blind, placebo-controlled single-ascending-dose study of intravenous administration of E6011 (0.0006-10 mg/kg) in healthy Japanese adult men (n = 64). The starting dose was the minimum anticipated biological effect level (MABEL). MABEL was estimated by extrapolating results of a pharmacokinetic/pharmacodynamic (PK/PD) model relating E6011 exposure and suppression of free soluble FKN using data obtained from cynomolgus monkeys. Safety assessments consisted of monitoring and recording adverse events, laboratory tests, vital signs, intensive electrocardiograms, and chest x-rays. Blood samples to determine PK, PD (serum total FKN concentration), and serum anti-E6011 antibody were collected. Noncompartmental analysis was used to derive PK parameters. Single intravenous infusions of E6011 were safe and well tolerated in healthy subjects. Serum E6011 concentrations showed triphasic elimination. An increase in serum total FKN concentration was observed, confirming target engagement. The dose strategy for patient studies is to select regimens that will attain a minimum serum E6011 exposure of 10 μg/mL, identified as the minimum concentration needed to saturate the target-mediated elimination pathway. Model-based drug development from preclinical stage was successful in identifying dose regimens for clinical testing.

Improvement of pharmacokinetic properties of therapeutic antibodies by antibody engineering

Monoclonal antibodies (mAbs) have become an important therapeutic option for several diseases. Since several mAbs have shown promising efficacy in clinic, the competition to develop mAbs has become severe. In efforts to gain a competitive advantage over other mAbs and provide significant benefits to patients, innovations in antibody engineering have aimed at improving the pharmacokinetic properties of mAbs. Because engineering can provide therapeutics that are more convenient, safer, and more efficacious for patients in several disease areas, it is an attractive approach to provide significant benefits to patients. Further advances in engineering mAbs to modulate their pharmacokinetics were driven by the increase of total soluble target antigen concentration that is often observed after injecting a mAb, which then requires a high dosage to antagonize. To decrease the required dosage, several antibody engineering techniques have been invented that reduce the total concentration of soluble target antigen. Here, we review the various ways that antibody engineering can improve the pharmacokinetic properties of mAbs.

Tutorial on Monoclonal Antibody Pharmacokinetics and Its Considerations in Early Development

The tutorial introduces the readers to the fundamentals of antibody pharmacokinetics (PK) in the context of drug development. Topics covered include an overview of antibody development, PK characteristics, and the application of antibody PK/pharmacodynamics (PD) in research and development decision-making. We also discuss the general considerations for planning a nonclinical PK program and describe the types of PK studies that should be performed during early development of monoclonal antibodies.

Prediction of non-linear pharmacokinetics in humans of an antibody-drug conjugate (ADC) when evaluation of higher doses in animals is limited by tolerability: Case study with an anti-CD33 ADC

For antibody-drug conjugates (ADCs) that carry a cytotoxic drug, doses that can be administered in preclinical studies are typically limited by tolerability, leading to a narrow dose range that can be tested. For molecules with non-linear pharmacokinetics (PK), this limited dose range may be insufficient to fully characterize the PK of the ADC and limits translation to humans. Mathematical PK models are frequently used for molecule selection during preclinical drug development and for translational predictions to guide clinical study design. Here, we present a practical approach that uses limited PK and receptor occupancy (RO) data of the corresponding unconjugated antibody to predict ADC PK when conjugation does not alter the non-specific clearance or the antibody-target interaction. We used a 2-compartment model incorporating non-specific and specific (target mediated) clearances, where the latter is a function of RO, to describe the PK of anti-CD33 ADC with dose-limiting neutropenia in cynomolgus monkeys. We tested our model by comparing PK predictions based on the unconjugated antibody to observed ADC PK data that was not utilized for model development. Prospective prediction of human PK was performed by incorporating in vitro binding affinity differences between species for varying levels of CD33 target expression. Additionally, this approach was used to predict human PK of other previously tested anti-CD33 molecules with published clinical data. The findings showed that, for a cytotoxic ADC with non-linear PK and limited preclinical PK data, incorporating RO in the PK model and using data from the corresponding unconjugated antibody at higher doses allowed the identification of parameters to characterize monkey PK and enabled human PK predictions.

Linear pharmacokinetic parameters for monoclonal antibodies are similar within a species and across different pharmacological targets: A comparison between human, cynomolgus monkey and hFcRn Tg32 transgenic mouse using a population-modeling approach

The linear pharmacokinetics (PK) of therapeutic monoclonal antibodies (mAbs) can be considered a class property with values that are similar to endogenous IgG. Knowledge of these parameters across species could be used to avoid unnecessary in vivo PK studies and to enable early PK predictions and pharmacokinetic/pharmacodynamic (PK/PD) simulations. In this work, population-pharmacokinetic (popPK) modeling was used to determine a single set of ‘typical’ popPK parameters describing the linear PK of mAbs in human, cynomolgus monkey and transgenic mice expressing the human neonatal Fc receptor (hFcRn Tg32), using a rich dataset of 27 mAbs. Non-linear PK was excluded from the datasets and a 2-compartment model was applied to describe mAb disposition. Typical human popPK estimates compared well with data from comparator mAbs with linear PK in the clinic. Outliers with higher than typical clearance were found to have non-specific interactions in an affinity-capture self-interaction nanoparticle spectroscopy assay, offering a potential tool to screen out these mAbs at an early stage. Translational strategies were investigated for prediction of human linear PK of mAbs, including use of typical human popPK parameters and allometric exponents from cynomolgus monkey and Tg32 mouse. Each method gave good prediction of human PK with parameters predicted within 2-fold. These strategies offer alternative options to the use of cynomolgus monkeys for human PK predictions of linear mAbs, based on in silico methods (typical human popPK parameters) or using a rodent species (Tg32 mouse), and call into question the value of completing extensive in vivo preclinical PK to inform linear mAb PK.

Translational PK-PD modeling analysis of MCLA-128, a HER2/HER3 bispecific monoclonal antibody, to predict clinical efficacious exposure and dose

Introduction MCLA-128 is a bispecific monoclonal antibody targeting the HER2 and HER3 receptors. Pharmacokinetics (PK) and pharmacodynamics (PD) of MCLA-128 have been evaluated in preclinical studies in cynomolgus monkeys and mice. The aim of this study was to characterize the PK and PD of MCLA-128 and to predict a safe starting dose and efficacious clinical dose for the First-In-Human study. Methods A PK-PD model was developed based on PK data from cynomolgus monkeys and tumor growth data from a mouse JIMT-1 xenograft model. Allometric scaling was used to scale PK parameters between species. Simulations were performed to predict the safe and efficacious clinical dose, based on AUCs, receptor occupancies and PK-PD model simulations. Results MCLA-128 PK in cynomolgus monkeys was described by a two-compartment model with parallel linear and nonlinear clearance. The xenograft tumor growth model consisted of a tumor compartment with a zero-order growth rate and a first-order dying rate, both affected by MCLA-128. Human doses of 10 to 480 mg q3wk were predicted to show a safety margin of >10-fold compared to the cynomolgus monkey AUC at the no-observed-adverse-effect-level (NOAEL). Doses of ≥360 mg resulted in predicted receptor occupancies above 99% (C_max and C_ave). These doses showed anti-tumor efficacy in the PK-PD model. Conclusions This analysis predicts that a flat dose of 10 to 480 mg q3wk is suitable as starting dose for a First-in-Human study with MCLA-128. Flat doses ≥360 mg q3wk are expected to be efficacious in human, based on receptor occupancies and PK-PD model simulations.