Abstract 2013: Oxidized anthracycline payloads induce anti-tumor immunogenic cell-death and show linker-dependent tolerability when delivered as ADCs

Abstract

Abstract Novel payloads with orthogonal mechanisms of action (MOAs) to established ADC technologies are important for expanding the utility of antibody-drug conjugates (ADCs) in cancer treatment. Anthracyclines, a class of cytotoxic small molecules that include important clinical chemotherapeutics such as doxorubicin, have long been of interest to the ADC field due to their high potency and unique MOA. Interest in anthracyclines has increased in recent years due to their status as canonical inducers of immunogenic-cell death (ICD), a feature that may lead to more durable tumor regressions and increased synergy with immune checkpoint blockade. In this work, we investigate several drug-linkers based on oxidized derivatives of the highly potent anthracycline analogue PNU-159682. Resultant ADCs are potent and immunologically specific with linker-dependent bystander activity in co-culture cytotoxicity assays displaying heterogeneous antigen (Ag+/Ag-) expression. Rodent in vivo anti-tumor activity and tolerability are shown with significant differences emerging between the toxicity profile of the cleavable and non-cleavable analogues. In vitro, tumor cells treated with anthracycline ADCs showed key hallmarks of ICD including markers of endoplasmic reticulum (ER) stress and the induction of ICD damage-associated molecular patterns (DAMPs) such as HMGB1 and ATP. In vivo mouse xenograft studies show increased tumoral F4/80+ macrophage infiltration by IHC in anthracycline ADC treated animals relative to controls. ADCs delivering monomethyl auristatin E (MMAE) show comparable activity in ICD assays, confirming MMAE as an ICD inducing ADC payload alongside canonical inducers such as anthracyclines. Our results indicate there is a therapeutic window in rodents alongside ICD induction by anthracycline ADCs, positioning anthracyclines as a potentially impactful class of ADC payloads. Citation Format: Joseph Z. Hamilton, Kerry Klussman, Rebecca Mahzereh, Jessica Simmons, Michelle Ulrich, Shyra J. Gardai, Peter D. Senter, Patrick J. Burke. Oxidized anthracycline payloads induce anti-tumor immunogenic cell-death and show linker-dependent tolerability when delivered as ADCs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2013.