Abstract LB085: Antitumor activity of AZD0754, a dnTGFbRII armored STEAP2 targeted CAR-T therapy, in preclinical models of prostate cancer

Abstract Prostate cancer is traditionally considered an immunologically “cold” tumor type rendering patients insensitive to immunotherapy. Targeting surface antigens on tumors through cellular therapy can induce a potent anti tumor immune response to “heat up” the tumor microenvironment. However, many antigens expressed on prostate tumors are also found on normal tissues, potentially causing on-target, off-tumor toxicities and a sub-optimal therapeutic index. Our target discovery and validation efforts identified STEAP2 as a superior prostate antigen for therapeutic targeting. Importantly, STEAP2 is a highly prevalent prostate cancer antigen displaying high, homogeneous cell surface expression across all stages of disease. A novel lead generation approach facilitated the development of a potent and specific armored STEAP2 CAR-T therapeutic candidate, AZD0754. This second generation CAR-T product is armored with a dominant-negative TGFβRII, thereby bolstering activity in the TGFβ-rich immunosuppressive environment of prostate cancer. Armored STEAP2 CAR-T cells demonstrate favorable in vitro properties, robust dose dependent in vivo efficacy in STEAP2 expressing cell line- and patient derived- mouse xenograft models and encouraging preclinical safety. Taken together, this data builds confidence in the specificity and potency of this potential first in class STEAP2 targeted CAR-T therapy and supports future clinical development. Citation Format: Dewald van Dyk, Peter Zanvit, Christine Fazenbaker, Kelly McGlinchey, Weichuan Luo, Jessica Pezold, John Meekin, Chien-ying Chang, Benjamin Clark, Philip L. Martin, Clare Hoover, Eric Tu, Ryan Gilbreth, Mark Cobbold, Gordon Moody, Emily E. Bosco. Antitumor activity of AZD0754, a dnTGFbRII armored STEAP2 targeted CAR-T therapy, in preclinical models of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB085.