Abstract B022: Targeting senescence cells in cancer and aging by conditionally active biologic therapeutics
Authors: Chen Jian , Wang Jing , Lucas Matt , Liu Haizhen , Wheeler Christina , Johnson Kyrie , Woodard Kathryn , Chang Cathy , Frey Gerhard , Boyle William J. , Short Jay M. 
Published: January 2023

Abstract
Cellular senescence is characterized by stable cell cycle arrest and a secretory program that modulates the tissue microenvironment. The aberrant accumulation of senescent cells in aged and cancerous tissue triggers inflammatory signaling through a senescence-associated secretory phenotype (SASP), promoting aging and tumor progression. Pharmacologically, clearing senescent cells has been shown to have promising effects against cancer and age-related pathologies in preclinical models as well as human pilot clinical trials. However, current senescent cell elimination strategies are focused on the rare senescence targets that are under-represented on normal cells. To date, there are no universal senescence cell specific markers. Therefore, the use of senolytics in the clinic is still limited due to their cytotoxicity to normal cells. A more effective senescence cell targeted approach is needed to reduce side effects and increase the efficiency of senescence cell removal. Conditionally Active Biologics (CAB) technology is a proprietary platform that is unique in its ability to selectively activate in the context of diseased tissues, but not normal tissues, taking advantage of the acidic pH conditions in the inflammatory tumor/aged tissue microenvironment. Senescent cells, like tumor cells, are dependent on glycolysis for energy metabolism, and thus generate a glycolytic microenvironment (GME) that resembles that of the tumor microenvironment. Since our CAB technology is already being deployed in cancer therapy by targeting cell surface markers such as AXL, ROR2, and CTLA4 in the clinical stage, we explored whether CAB technology will allow selective removal of senescent cells in SASP-associated microenvironments such as the GME. To identify senescence-specific surface antigens that are broadly and specifically upregulated in senescent cells, we screened our CAB cell surface antigen library in different senescence models including CDK4/6 inhibitor-induced senescent human breast cancer cells, human lung fibroblast cells, as well as in vivo aging mouse tissues and chronic kidney disease mouse model. We have identified several novel senescence markers which show significantly elevated expression in senescent cells. Furthermore, in vitro binding assays demonstrated that CAB antibodies targeting these senescence markers have no or very low binding to the target antigen on senescence cells in alkaline physiological conditions but have strong binding in glycolytic/acidic SASP conditions. Moreover, we performed antibody-dependent cell-mediated cytotoxicity assays for evaluating the functional activities of CAB antibodies against the senescence targets. Our data demonstrated that CAB antibodies were more potent against senescent cells compared to proliferating cells and displayed high selectivity for the glycolytic/acidic microenvironment condition. In conclusion, CAB technology should provide a new generation of biologics with an increased safety margin and therapeutic index in the clinic targeting senescence cells in cancer and age-related diseases.
Citation Format: Jian Chen, Jing Wang, Matt Lucas, Haizhen Liu, Christina Wheeler, Kyrie Johnson, Kathryn Woodard, Cathy Chang, Gerhard Frey, William J. Boyle, Jay M. Short. Targeting senescence cells in cancer and aging by conditionally active biologic therapeutics [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr B022.