Antibody-drug conjugate (ADC) joint disposition properties and their clinical utilities for comparative assessments in terms of favorable pharmacokinetic (PK) characteristics.

Abstract

e15005 Background: PK characterization of ADCs is often fragmented using separate analyses of individual analytes. As such it is difficult to compare among ADCs in terms of PK characteristics critical for understanding the fate of an ADC complex as a whole and its clinical implications. While several integrated PK models have been applied to clinical datasets, these have been mostly for the purpose of identifying covariate effects on PK parameters. In this abstract, we propose 3 joint disposition metrics for integrated PK characterization of ADCs based on a combination of concentrations of ADC, payload (PL), conjugated payload (CPL), and total mAb (TAb, ADC plus unconjugated mAb) in the blood, and for defining what are favorable PK characteristics for ADCs. Methods: The joint disposition metrics representing linker stability (AUCmAb/AUCTab), therapeutic exposure ratio (CLPL/CLADC) and effective drug-antibody ratio (DAR) (AUCCPL/AUCADC), were derived mathematically from a framework of typical ADC designs and verified via modeling approaches using PK data of 3 clinical candidates, an anti-Trop2 ADC (PF-06664178) [King GT, et al. Invest New Drugs 2018;36(5):836-847], an anti-Notch3 ADC (PF-06650808) [Rosen LS, et al. Invest New Drugs 2020;38(1):120-130], and an anti-PTK7 ADC (PF-06647020) [Maitland ML, et al. Clin Cancer Res 2021;27(16):4511-4520]. Furthermore, the joint disposition metrics were calculated for a number of FDA-approved or otherwise well documented ADCs, which were selected as the information on ADC, payload and TAb analytes is available, to examine their clinical utilities in assessing among ADCs in terms of favorable PK characteristics. Results: The validity of the joint disposition metrics was demonstrated and verified for integrated PK characterization of ADCs. Estimates of the joint disposition metrics, for the linker stability, therapeutic exposure ratio and effective DAR, were obtained for the selected ADCs products and candidates (Table below), consistent with the expectation based on clinical experience. Conclusions: Three joint disposition metrics were derived for integrated PK characterization of ADCs using conventional PK analytes. Their clinical utilities were explored in assessing among ADCs in terms of favorable PK characteristics. Analyses of additional ADCs may be needed to further validate these metrics for broader usage.[Table: see text]