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.

Two Case Studies on How Study Designs Can Be Made More Informative Using Modeling and Simulation Approaches.

Drug development should extract maximum information from experiments with minimized exposure of patients or experimental animals to invasive procedures and potentially harmful effects with minimized investment of time and money. Herein, two aspects of study design are explored illustrating how information can be extracted more efficiently by investigating a range of exposures within each individual by either following responses as drug concentrations decline or by within-individual dose escalation, rather than relying on steady-state cross-sectional analyses.

Efficacy and safety of multiple doses of QGE031 (ligelizumab) versus omalizumab and placebo in inhibiting allergen-induced early asthmatic responses.

BACKGROUND: Omalizumab is an established anti-IgE therapy for the treatment of allergic diseases that prevents IgE from binding to its receptor. QGE031 is an investigational anti-IgE antibody that binds IgE with higher affinity than omalizumab. OBJECTIVE: This study compared the effects of QGE031 with those of omalizumab on clinical efficacy, IgE levels, and FcεRI expression in a clinical model of allergic asthma. METHODS: Thirty-seven patients with mild allergic asthma were randomized to subcutaneous omalizumab, placebo, or QGE031 at 24, 72, or 240 mg every 2 weeks for 10 weeks in a double-blind, parallel-group multicenter study. Inhaled allergen challenges and skin tests were conducted before dosing and at weeks 6, 12, and 18, and blood was collected until 24 weeks after the first dose. RESULTS: QGE031 elicited a concentration- and time-dependent change in the provocative concentration of allergen causing a 15% decrease in FEV1 (allergen PC15) that was maximal and approximately 3-fold greater than that of omalizumab (P = .10) and 16-fold greater than that of placebo (P = .0001) at week 12 in the 240-mg cohort. Skin responses reached 85% suppression at week 12 in the 240-mg cohort and were maximal at week 18. The top doses of QGE031 consistently suppressed skin test responses among subjects but had a variable effect on allergen PC15 (2-fold to 500-fold change). QGE031 was well tolerated. CONCLUSION: QGE031 has greater efficacy than omalizumab on inhaled and skin allergen responses in patients with mild allergic asthma. These data support the clinical development of QGE031 as a treatment of asthma.

Ethnic sensitivity assessment of pharmacokinetics and pharmacodynamics of omalizumab with dosing table expansion.

A three-part license expansion for omalizumab (Xolair(®)), humanized anti-IgE antibody, was recently made in Japan for paediatric use, additional higher doses and revised dosing frequency in allergic asthma. The dosing level and frequency of omalizumab are guided by a dosing table based on the total serum IgE and bodyweight. Nonlinear mixed-effect pharmacokinetic (PK) and pharmacodynamic (PD) modeling and simulation techniques described the binding between omalizumab and its target IgE. The population PKPD analysis was conducted using data from the nine studies included originally in the European application of dosing table expansion together with three Japanese clinical studies to assess the influence of the ethnicity. Statistically significant differences between the ethnic groups were detected. These were small, within or close to bioequivalence criteria. The model described the primary pharmacology in Caucasian and Japanese patients, both adult and paediatric, with simulations showing that the interplay between the clearance, volume and binding affinity parameters was such that there was no clinical impact of the Japanese ethnic differences on either drug PK or free IgE suppression and hence the required posology.

Revision of omalizumab dosing table for dosing every 4 instead of 2 weeks for specific ranges of bodyweight and baseline IgE.

The dosing level and frequency of omalizumab are guided by a dosing table based on total serum immunoglobulin E (IgE) and bodyweight. Using a validated, mathematical simulation model (based on concentration data from 8 studies), we evaluated the impact of a revised omalizumab dosing table (every 4 weeks dosing regimen) on the pharmacokinetic and pharmacodynamic profiles of free and total IgE. Safety analysis, in patients with high levels of exposure to omalizumab, was done using data from the clinical and post-marketing databases. The model accurately predicted observed omalizumab, free and total IgE concentrations. After reaching steady-state, the average increase in exposure was 10%, even for patients with the highest concentrations at the upper 97.5th percentile. Free IgE suppression slightly increased in the initial phase, and slightly reduced at the trough of the dosing cycle, but average suppression remained similar for both regimens. The safety profile of omalizumab was similar for patients receiving higher or lower doses. Thus, doubling the dose of omalizumab, in a subset of patients receiving 225-300 mg of omalizumab (every 2 weeks dosing regimen) can efficiently suppress free IgE without compromising safety or efficacy.

Omalizumab in asthma: an update on recent developments.

IgE is central to the pathophysiology of allergic asthma. Omalizumab, a humanized anti-IgE mAb, specifically binds free IgE and interrupts the allergic cascade by preventing binding of IgE with its high-affinity FcεRI receptors on mast cells, antigen-presenting cells, and other inflammatory cells. The clinical efficacy of omalizumab has been well documented in a number of clinical trials that involve adults, adolescents, and children with moderate-to-severe and severe allergic asthma. In these studies, omalizumab reduced exacerbations, asthma symptoms, inhaled corticosteroid and rescue medication use, and improved quality of life relative to placebo or best standard of care. Similar benefits have been reported in observational studies in "real-world" populations of patients. Results from recent pooled data from randomized clinical trials and from a large prospective cohort study provide reassurance about the long-term safety of omalizumab. Omalizumab dosing is individualized according to body weight and serum-IgE level, and recent adjustments to the dosing algorithm in Europe have enabled more patients to be eligible for treatment. Ongoing and future research is investigating the optimal duration of therapy, accurate predictors of response to treatment, and efficacy in nonatopic asthma as well as other IgE-mediated conditions.

Pharmacokinetic and pharmacodynamic properties of canakinumab, a human anti-interleukin-1ß monoclonal antibody.

Canakinumab is a high-affinity human monoclonal anti-interleukin-1ß (IL-1ß) antibody of the IgG1/κ isotype designed to bind and neutralize the activity of human IL-1ß, a pro-inflammatory cytokine. Canakinumab is currently being investigated on the premise that it would exert anti-inflammatory effects on a broad spectrum of diseases, driven by IL-1ß. This paper focuses on the analysis of the pharmacokinetic and pharmacodynamic data from the canakinumab clinical development programme, describing results from the recently approved indication for the treatment of cryopyrin-associated periodic syndromes (CAPS) under the trade name ILARIS®, as well as diseases such as rheumatoid arthritis, asthma and psoriasis. Canakinumab displays pharmacokinetic properties typical of an IgG1 antibody. In a CAPS patient weighing 70 kg, slow serum clearance (0.174 L/day) was observed with a low total volume of distribution at steady state (6.0 L), resulting in a long elimination half-life of 26 days. The subcutaneous absolute bioavailability was high (70%). Canakinumab displays linear pharmacokinetics, with a dose-proportional increase in exposure and no evidence of accelerated clearance or time-dependent changes in pharmacokinetics following repeated administration was observed. The pharmacokinetics of canakinumab in various diseases (e.g. CAPS, rheumatoid arthritis, psoriasis or asthma) are comparable to those in healthy individuals. No sex- or age-related pharmacokinetic differences were observed after correction for body weight. An increase in total IL-1ß was observed in both healthy subjects and all patient populations following canakinumab dosing, reflecting the ability of canakinumab to bind circulating IL-1ß. The kinetics of total IL-1ß along with the pharmacokinetics of canakinumab were characterized by a population-based pharmacokinetic-binding model, where the apparent in vivo dissociation constant, signifying binding affinity of canakinumab to circulating IL-1ß, was estimated at 1.07 ± 0.173 nmol/L in CAPS patients. During development of canakinumab a cell line change was introduced. Pharmacokinetic characterization was performed in both animals and humans to assure that this manufacturing change did not affect the pharmacokinetic/pharmacodynamic properties of canakinumab.

Population pharmacokinetic and pharmacodynamic model-based comparability assessment of a recombinant human Epoetin Alfa and the Biosimilar HX575.

The aim of this study was to develop an integrated pharmacokinetic and pharmacodynamic (PK/PD) model and assess the comparability between epoetin alfa HEXAL/Binocrit (HX575) and a comparator epoetin alfa by a model-based approach. PK/PD data-including serum drug concentrations, reticulocyte counts, red blood cells, and hemoglobin levels-were obtained from 2 clinical studies. In sum, 149 healthy men received multiple intravenous or subcutaneous doses of HX575 (100 IU/kg) and the comparator 3 times a week for 4 weeks. A population model based on pharmacodynamics-mediated drug disposition and cell maturation processes was used to characterize the PK/PD data for the 2 drugs. Simulations showed that due to target amount changes, total clearance may increase up to 2.4-fold as compared with the baseline. Further simulations suggested that once-weekly and thrice-weekly subcutaneous dosing regimens would result in similar efficacy. The findings from the model-based analysis were consistent with previous results using the standard noncompartmental approach demonstrating PK/PD comparability between HX575 and comparator. However, due to complexity of the PK/PD model, control of random effects was not straightforward. Whereas population PK/PD model-based analyses are suited for studying complex biological systems, such models have their limitations (statistical), and their comparability results should be interpreted carefully.

Omalizumab decreases IgE production in patients with allergic (IgE-mediated) asthma; PKPD analysis of a biomarker, total IgE.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Omalizumab is a humanized anti-IgE monoclonal antibody that binds and captures circulating IgE, preventing interaction with receptors on mast cells and basophils, thereby interrupting the allergic cascade. It has a well-characterized efficacy and safety profile in patients with asthma. While omalizumab is known to reduce serum free IgE concentrations, effects on total IgE and IgE production are less well characterized. WHAT THIS STUDY ADDS: (i) Confirmation of prior hypotheses that IgE production can decrease with time when patients are given anti-IgE therapy; (ii) guidance on a biomarker, total IgE, which can be used to ascertain whether individual patients experience a change in their IgE production; and (iii) a way to assess whether patients' IgE production has been sufficiently down-regulated such that they may consider stopping anti-IgE therapy. AIM: To determine whether excessive IgE production by patients with atopic allergic asthma decreases with omalizumab therapy. METHODS: Omalizumab, free and total IgE data were obtained from an epidemiological study and six randomized, double-blind, placebo-controlled trials in patients with allergic asthma. The binding between omalizumab and IgE together with the production and elimination of IgE were modelled as previously, except that, in order to explain why total IgE was decreasing over a period of 5 years, the expression of IgE was allowed to change. RESULTS: The prior constant IgE production model failed to converge on the data once long-term observations were included, whereas models allowing IgE production to decrease fitted. A feedback model indicated that, on average, IgE production decreased by 54% per year. This model was further developed with covariate searches indicating clinically small but statistically significant effects of age, gender, body mass index and race on some parameters. Model predictions were checked internally and externally against 3-5 year data from paediatric and adult atopic asthmatic patients and externally against extensive total IgE data from a long-duration (>1 year) phase 1 study which was not used in the model building. CONCLUSIONS: A pharmacokinetic-pharmacodynamic model incorporating omalizumab-IgE binding and feedback for control of IgE production indicates that omalizumab reduces production of IgE. This raises the possibility that indefinite treatment may not be required, only for perhaps a few years. After the initial accumulation, total IgE should provide a means to monitor IgE production and guide individual treatment decisions.

From target selection to the minimum acceptable biological effect level for human study: use of mechanism-based PK/PD modeling to design safe and efficacious biologics.

In this paper, two applications of mechanism-based modeling are presented with their utility from candidate selection to first-in-human dosage selection. The first example is for a monoclonal antibody against a cytomegalovirus glycoprotein complex, which involves an antibody binding model and a viral load model. The model was used as part of a feasibility analysis prior to antibody generation, setting the specifications for the affinity needed to achieve a desired level of clinical efficacy. The second example is a pharmacokinetic-pharmacodynamic model based on a single-dose pharmacology study in cynomolgus monkey using data on pharmacokinetics, receptor occupancy, and the dynamics of target cell depletion and recovery. The model was used to estimate the MABEL, here defined as the minimum acceptable biological effect level against which a dose is selected for a first-in-human study. From these applications, we demonstrate that mechanism-based PK/PD binding models are useful for predicting human response to biologics compounds. Especially, such models have the ability to integrate preclinical and clinical, in vitro and in vivo information and facilitate rational decision making during various stages of drug discovery and translational research.

On setting the first dose in man: quantitating biotherapeutic drug-target binding through pharmacokinetic and pharmacodynamic models.

Although the three (perhaps four) phases of clinical drug development are well known, it is relatively unappreciated that there are similar phases in pre-clinical development. These consist of 'Phase I' the initial, normally Research Discovery driven pharmacology; 'Phase II' non-good laboratory practice (GLP) dose range finding, followed by pivotal 'Phase III' GLP toxicology. Together with an array of in vitro experiments comparing species, these stages should enable an integrated safety assessment prior to entry into man, documenting to investigators and authorities evidence that the new pharmaceutic is unlikely to cause harm. Following the lessons learned from TeGenero TGN1412 and subsequent updates to regulatory guidelines, there are aspects peculiar to biotherapeutics, especially those that target key body systems, where calculations could be made for doses for human studies using pharmacokinetic and pharmacodynamic models. Two of these are exemplified in this paper. In the first, target-mediated drug disposition, where the binding of the drug to a cellular target quantitatively affects the pharmacokinetics, enables occupancy to be estimated without recourse to independent assays. In the second, assaying captured soluble target, as drug-target complexes, allows estimation of the concentration of the free ligand ensuring that in initial clinical studies, soluble targets are not overly suppressed. To support this methodology, it has been demonstrated using omalizumab, free and total IgE data that such analyses do predict the suppression of the free unbound ligand with reasonable accuracy. Overall, the objective of the process is to deliver a justification, through consideration of drug-target binding, of a safe starting and therapeutically relevant escalation doses for human studies.

Relationship between omalizumab pharmacokinetics, IgE pharmacodynamics and symptoms in patients with severe persistent allergic (IgE-mediated) asthma.

AIMS: Omalizumab, a subcutaneously administered anti-IgE antibody, is effective for moderate-to-severe persistent allergic asthma. The aims were to (i) describe the population pharmacodynamics of free IgE with a mechanism-based, nonlinear, omalizumab-IgE binding model; (ii) deduce a target-free IgE suppression level by correlation with clinical outcomes; and (iii) check the adequacy of current approved dosing tables and explore potential doses and regimens beyond. METHODS: Concentration data (omalizumab, free and total IgE) were obtained from 1781 patients aged 12-79 years, in four sparsely sampled randomized, placebo-controlled studies and 152 subjects in a richly sampled single-dose study. NONMEM predictive performance across the range of bodyweights (39-150 kg) and baseline IgE (19-1055 IU ml(-1)) was checked by simulation. Predicted free IgE levels were correlated with time-averaged patient diary clinical outcomes. RESULTS: The model accurately predicted observed omalizumab, free and total IgE concentrations. Free IgE concentrations correlated well with clinical signs and symptoms, allowing a target concentration of 14 ng ml(-1), at the midpoint of 4-week clinical observation periods, to be set for determining the dose and regimen for omalizumab. CONCLUSIONS: The omalizumab-IgE binding model is predictive for free IgE and demonstrates a nonlinear time-dependent relationship between free IgE suppression and clinical outcomes in asthma. Although currently approved dosing tables are close to optimal, it should be possible to treat patients with higher levels of baseline IgE if higher doses can be administered.

Asthma symptom re-emergence after omalizumab withdrawal correlates well with increasing IgE and decreasing pharmacokinetic concentrations.

BACKGROUND: Physicians have questioned whether omalizumab can be discontinued or the dose reduced after clinical improvement is seen in patients with severe asthma. OBJECTIVES: To examine the relationships among omalizumab, free IgE, and clinical outcomes in a randomized, placebo-controlled trial in patients with severe persistent allergic asthma following a posology based on pretreatment total IgE and body weight. METHODS: A pharmacokinetic-pharmacodynamic binding model was used to calculate free IgE, omalizumab, and total IgE concentrations during the 28-week treatment and 16-week follow-up of the INvestigation of Omalizumab in seVere Asthma TrEatment (INNOVATE) study. These were plotted against the mean changes in the total asthma symptom score, morning peak expiratory flow, and rescue medication use for physician-defined treatment responders and nonresponders. RESULTS: The model accurately fitted omalizumab and free and total IgE, allowing reconstruction of the entire time course for each patient. Free IgE was rapidly suppressed below the 50 ng/mL (20.8 IU/mL) target, although there was a notable period before clinical measures stabilized. After treatment cessation, free IgE and omalizumab returned toward baseline and, after a delay, asthma symptoms re-emerged. Model-derived omalizumab and free IgE concentrations correlated well with changes in clinical outcomes, particularly in omalizumab-treated responders. Asthma symptoms exhibited different correlations during response onset compared with response offset (hysteresis), indicative of physiological time delays between changes in IgE levels and pulmonary function. CONCLUSION: Omalizumab and free IgE correlated well with clinical symptoms. Reducing omalizumab doses below those in the dosing table cannot be recommended; the resulting increase in free IgE would cause a deterioration in asthma control.

New approach to measure protein binding based on a parallel artificial membrane assay and human serum albumin.

We report here a new, label-free approach to measure serum protein binding constants. The assay is able to measure HSA K d values in the milli-molar to micromolar range. The protein is not immobilized on any surface and the assay self-corrects for nonspecific adsorption. No mass balance is required to get accurate binding constants and it is not necessary to wait for equilibrium to extract the binding constant. The assay runs in a 96-well format using commercially available parts and is, therefore, relatively easy to implement and automate. As the chemical membranes used are not water permeable, there is no volume change due to the osmotic pressure and pretreatment (soaking) is not necessary. The concept can potentially be extended to other proteins and could thus serve as a label-free technique for general binding constant measurements.

A mechanism-based binding model for the population pharmacokinetics and pharmacodynamics of omalizumab.

AIM: Omalizumab, a humanized IgG monoclonal antibody that binds to human immunoglobulin E (IgE), interrupts the allergic cascade in asthmatic patients. The aim was to compare simultaneously drug exposure and IgE biomarker responses in Japanese and White patient populations. METHODS: An instantaneous equilibrium drug-ligand binding and turnover population model was built from 202 Japanese patients. A posterior predictive evaluation for the steady-state distributions of omalizumab and IgE was then carried out against 531 White patients. RESULTS: The mean parameters estimated from the Japanese patients were as follows: omalizumab clearance 7.32 +/- 0.153 ml h(-1), IgE clearance 71.0 +/- 4.68 ml h(-1) and the difference between that for omalizumab and the complex 5.86 +/- 0.920 ml h(-1), the volume of distribution for omalizumab and IgE 5900 +/- 107 ml, and that for the complex 3630 +/- 223 ml, the rate of IgE production 30.3 +/- 2.04 microg h(-1). Half-lives of IgG (23 days) and IgE (2.4 days) were close to previous reports. The dissociation constant for binding, 1.07 nM, was similar to in vitro values. Clearance and volume of distribution for omalizumab varied with bodyweight, whereas the clearance and rate of production of IgE were predicted accurately by baseline IgE. Overall, these covariates explained much of the interindividual variability. CONCLUSIONS: The predictiveness of the Japanese model was confirmed by Monte-Carlo simulations for a White population, also providing evidence that the pharmacokinetics of omalizumab and IgE were similar in these two populations. Furthermore, the model enabled the estimation of not only omalizumab disposition parameters, but also the binding with and the rate of production, distribution and elimination of its target, IgE.

On the prediction of the human response: a recycled mechanistic pharmacokinetic/pharmacodynamic approach.

Although it is routine to predict the blood or plasma pharmacokinetics of compounds for man based upon preclinical studies, the real value of such predictions only comes when linked to drug effects. In the first example, the immunomodulator, FTY720, the first sphingosine-1-phosphate receptor agonist, stimulates the sequestration of lymphocytes into lymph nodes thus removing cells from blood circulation. A prior physiology-based pharmacokinetic model fitted the concentration-time course of FTY720 in rats. This was connected to an indirect response model of the lymphocyte system to characterise the cell trafficking effects. The IC(50) of FTY720 was different in the rat compared with the monkey; man was assumed to be similar to the monkey. The systemic lymphocyte half-lives were also different between species. To make predictions of the pharmacodynamic behaviour for man, two elements are required, i) systemic exposure, in this case from an upscaled physiology based model, and ii) an estimate of lymphocyte turnover in man, gained from the literature from other drug treatments. Predictions compared well with clinical results. The second example is the monoclonal antibody Xolair, designed to bind immunoglobulin E for atopic diseases. A mechanism based two-site binding model described the kinetics of both Xolair and endogenous IgE. This model has been reused for other monoclonal antibodies designed to bind fluid-phase ligands. Sensitivity analysis shows that if differences across species in the kinetics of the endogenous system are not accounted for, then pharmacokinetic/pharmacodynamic models may give misleading predictions of the time course and extent of the response.