Abstract 296: Identification of novel senolytic targets and development of conditionally active biologic-based-drug conjugates for targeted senescence-associated secretory phenotype elimination <i>in vivo</i>

Abstract Elimination of senescent cells has been reported to improve normal and pathological changes associated with aging and cancer in mice. However, most senolytic agents inhibit anti-apoptotic pathways that do not differentiate between hyper-inflamed senescence-associated secretory phenotype (SASP) cells from relatively non-inflamed, valuable functional senescent cells, leading to off-target effects in normal tissues. Conditionally Active Biologics (CAB) technology is a proprietary platform unique in its ability to be selectively active in the context of diseased, acidic tissues (e.g. inflamed tissue and tumor microenvironment), but not in alkaline normal tissues. The aberrant accumulation of senescent cells in aged and cancerous tissue triggers increasing inflammatory signaling through SASP, promoting aging and tumor progression. Since these cells have an acidic surface environment, similar to cancer cells, we explored whether CAB technology allows selective removal of senescent cells in SASP-associated microenvironments. In addition, to complement this selectivity, we identified more specific senolytic targets to further reduce side effects and increase the efficiency of senescence cell removal and SASP reduction. In this study we identified several novel senescence-specific surface antigens as senolytic targets both in vitro and in vivo. For the in vivo studies, we developed several fibrosis models in mice, including unilateral ureteral obstruction (UUO) in kidneys, bleomycin- or silica-induced pulmonary fibrosis in lung, high-fat diet (HFD)+CCl4-induced non-alcoholic steatohepatitis (NASH) in liver, and isoproterenol-induced cardiac fibrosis. We confirmed that the novel senescence-specific antigens we identified in our in vitro system are highly expressed in fibrotic tissues with newly induced senescent cells and associated with inflammation in in vivo models. Furthermore, these antigens were co-expressed with senescence makers SA-β-Gal, GL13, p16 and p21. Finally, we developed duocarmycin-based CAB-antibody drug conjugates (CAB-ADC) to study whether CAB-ADC reduces senescent cell occurrence in vivo. Mice treated with CAB-ADC targeting novel senescence-specific antigens showed a significant reduction of inflammatory cells infiltrated in kidneys compared to mice treated with benchmark and isotype ADCs. Thus, the CAB antibody-based therapeutic is a promising strategy for senescent cell removal in an inflammatory microenvironment using these newly identified senescence-associated targets. In conclusion, CAB technology provides a new generation of biologics with an increased safety margin and therapeutic index, selectively targeting acidic senescence cells and SASP in cancer and age-related diseases. Citation Format: Jian Chen, Jing Wang, Haizheng Liu, Gerhard Frey, Cathy Chang, William J. Boyle, Jay M. Short. Identification of novel senolytic targets and development of conditionally active biologic-based-drug conjugates for targeted senescence-associated secretory phenotype elimination in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 296.