Elucidating The Roles Of Antibody Pharmacokinetics And Maleimide Stability In The Toxicology Of Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) continue to emerge as effective therapeutics in a variety of oncology indications, with two agents currently approved and many more in late-stage clinical trials. These ADCs employ drug-linkers that were developed many years ago, and are now recognized to have properties that may adversely impact the activity and toxicology of the ADCs prepared with them. Two such properties that are now well appreciated are the reversibility of maleimide-based drug conjugation, and the impact of drug conjugation on the pharmacokinetics of the ADC. We recently reported advances in drug-linker design that independently address both of these properties, resulting in the irreversible conjugation of drugs which have minimal impact on antibody pharmacokinetics, even at high levels of drug loading (Nature Biotechnology 32, 1059-1062 (2014), Nature Biotechnology 33, 733-735 (2015)). We have now prepared drug-linkers of monomethylauristatin E (MMAE) that orthogonally employ these features to enable a systematic evaluation of the relative contributions of maleimide instability and accelerated plasma clearance on the in vivo behavior of MMAE ADCs. Biodistribution studies with these molecules have revealed that the concentration of released MMAE in normal tissues is greatly impacted by the rate of ADC clearance (fast clearance results in greater Cmax of free drug), while stabilization of the maleimide has a relatively small effect. These differences in observed free drug concentrations were paralleled in tolerability studies, with ADC clearance rates exerting a greater impact on hematology parameters than maleimide stability. Collectively, these results suggest that ADC pharmacokinetics dominate the biodistribution and toxicology profiles for a given drug payload, with conjugate stability playing a relatively minor role. Citation Format: Haley Neff-LaFord, Franciso Zapata, Wendi Schultz, Cindy Balasubramanian, Paul Pittmen, Shawna Hengel, Russell Sanderson, Nagendra Chemuturi, Jocelyn Setter, Robert P. Lyon. Elucidating the roles of antibody pharmacokinetics and maleimide stability in the toxicology of antibody-drug conjugates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 70. doi:10.1158/1538-7445.AM2017-70