Veena A. Thomas, Shufang Liu, Sara C. Humphreys, Kevin D. Cook, Kip Conner, Ana R. Correia, Alex W. Jacobitz, Melissa Yang, Ronya Primack, Marcus Soto, Rupa Padaki, Mariusz Lubomirski, Richard Smith, Marissa Mock, Isabel Figueroa
aDepartment Pharmacokinetics and Drug Metabolism, Amgen Inc., South San Francisco, U.S.A
Objectives: In this investigation, we test the hypothesis that within a PBPK framework, experimentally determined in vitro physiochemical assay metrics could serve as covariates of pinocytosis or convective transport to explain the inter-antibody variability in mAb mouse plasma PK. The objective is to triage and de-risk antibodies in early discovery preclinical screening allowing a priori characterization of mAb PK concentration-time profiles.
Methods: A diverse panel of 56 mAbs were evaluated for PK in wild-type mice. These 56 mAbs demonstrated an eight-fold variability in the area under the curve (: 1.74×106 -1.38×107 ng∙h/mL) and a ten-fold difference in clearance (2.55 – 26.4 mL/day/kg) formed the training set for this investigation. The mAbs were subjected to ten in vitro assays to measure major physiochemical attributes including neonatal Fc receptor (FcRn) chromatography, AlphaScreen FcRn binding assay, hydrophobic interaction chromatography, affinity chromatography self-interaction nanoparticle spectroscopy, in silico determined isoelectric point, heparin chromatography, baculovirus particle binding assay, membrane preparation binding assay, poly-D-lysine binding assay, polyethyleneimine binding assay, and thermolysin stability assay.
Results: Using a PBPK framework, mAb-dependent coefficients F1 and F2 modulating pinocytosis rate and convective transport, respectively, were estimated for each mAb with mostly good precision (coefficient of variation <30%). F1 was estimated to be the mean and standard error of 0.961±0.593, and F2 was estimated to be 2.13±2.62. Using principal component analysis to correlate the regressed values of F1/F2 versus the multidimensional dataset comprised of our panel of in vitro assays, we found that heparin chromatography retention time emerged as the predictive covariate to the mAb-specific F1, whereas F2 variability cannot be well explained by these assays. A sigmoidal relationship between F1 and the identified covariate was incorporated within the PBPK framework and characterized the training data well. The predictive utility of the developed PBPK model was evaluated against a separate panel of 14 mAbs biased toward high clearance, among which area under the curve of PK data of 12 mAbs was predicted within 2.5-fold error, and the positive and negative predictive values for clearance prediction were 85% and 100%, respectively.
Conclusions: With the inclusion of heparin chromatography to inform model-estimated pinocytosis, our validated application of PBPK modeling to predict mAb clearance preclinically in wild-type mice provides further validation of a similar approach in humans that was recently published by Hu et al. [1]. Taken together, these studies further substantiate mounting evidence that nonspecific binding, largely modulated by interactions between positively charged patches on the mAb surface and negatively charged surfaces in the systemic circulation, the interstitium, the cell surface, and within endosomes, is a significant driver of mAb PK and an attribute that should routinely be evaluated in vitro using heparin chromatography prior to testing in vivo in animals and humans.
References:
[1] Hu S, Datta-Mannan A, D’Argenio DZ. Physiologically Based Modeling to Predict Monoclonal Antibody Pharmacokinetics in Humans from in vitro Physiochemical Properties. MAbs 2022; 14:2056944.
Reference: PAGE 32 (2024) Abstr 10774 [www.page-meeting.org/?abstract=10774]
Poster: Methodology - Model Evaluation