Abstract P4-01-12: BAT8006, a novel FRα ADC with strong bystander effect, for the treatment of advanced solid tumor

Abstract

Abstract FRα is overexpressed in a number of cancers, including ovarian, breast, lung cancer, and endometrial carcinoma, yet limited expression in normal tissue. Efficacy of anti-FRα ADC have been demonstrated in clinical trials for high FRα expression ovarian cancer. These results validate FRα as a viable target for cancer treatment. We have developed a novel FRα ADC with strong bystander killing effect, BAT8006, which consists of a high-affinity antibody, an enzymatically cleavable linker and a topoisomerase I inhibitor as the payload, with DAR of 8. BAT8006 shows high affinity for the FRα antigen (KD < 0.5 nM) and FRα-expressing tumor cells. Upon binding to FRα on cell surface, BAT8006 internalizes effectively and traffics to the lysosome where payload is proteolytically released. BAT8006 demonstrated potent in vitro cell growth inhibitory activity to FRα-positive cells with IC50 values of ~ 1 nM. In an in vitro bystander killing assay, proliferation of FRα-negative cells was potently inhibited by addition of culture medium of BAT8006-treated FRα-positive cells, but not that of BAT8006-treated FRα-negative cells, indicating the bystander killing effect of the released payload in the culture medium. Less than 0.03% of the payload was released from BAT8006 when incubated with human or monkey plasma for 4 days in 37oC, suggesting the stability of BAT8006 in blood circulation. BAT8006 led to potent and dose-dependent tumor regression in patient-derived xenograft (PDX) model of SCLC. Furthermore, single dose of 2.5 mg/kg of BAT8006 showed complete eradication of tumor in choriocarcinoma JeG-3 xenograft mice model. In PDX of ovarian cancer, 2.5 mg/kg of BAT8006 (DAR8) demonstrated superior tumor inhibition activity than 5 mg/kg of BAT8006 with DAR4, suggesting the high DAR approach of BAT8006 would be more effective. In addition, BAT8006 showed favorable pharmacokinetic and safety profiles in cynomolgus monkeys with the highest non-severely toxic dose (HNSTD) of 30 mg/kg when dosed once every three weeks for 3 times. Together these results indicate that BAT8006 could potentially provide a therapeutic benefit to treat FRα-positive tumors including breast cancer in clinical trial. Citation Format: siqi mai, xingxing Mei, weijia Tang, Xin Zhou, Xuekang qi, Zhi Zhong, Shuoxu Li, Jianjun fan, Jirong Gan, Binghua Tan, Yao Qi, Yanling Guo, Shengfeng li, Jin-Chen Yu. BAT8006, a novel FRα ADC with strong bystander effect, for the treatment of advanced solid tumor [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-12.