Abstract 5087: ILB-3101, a novel B7H3-targeting ADC with Eribulin as payload, demonstrates strong tumor killing activities and favorable PK/TOX profile in preclinical evaluation

Abstract B7H3, a B7 family member of immune checkpoint proteins, is overexpressed in a broad spectrum of malignant tumors. It has become an attractive target for cancer therapies in recent years. ILB-3101, a potential best-in-class ADC, was constructed by conjugating a potent mitotic inhibitor Eribulin to a proprietary anti-B7H3 mAb through a proprietary linker. This ADC molecule has been developed and preclinically evaluated as both the 1st line ADC treatment with B7H3 expressed patients in Eribulin sensitive cancer types and the later line treatment for patients whose cancer are B7H3 positive but TopoI inhibitor resistant. The humanized antibody of ILB-3101 is IgG1 type and shows high affinity to both human and monkey B7H3 proteins. It also shows better internalization than benchmark antibodies such as that of DS-7300 analog. The DAR value of ILB-3101 is 3.5. ILB-3101 has potent and dose-dependent cytotoxicity to B7H3-positive tumor cells and shows better activities than DS-7300 analog as positive control. In vivo studies based on xenograft tumor models reveal that ILB-3101 has potent anti-tumor activities in various tumor types including TNBC, sarcoma, ovarian cancer and AML etc., which are superior or comparable to DS-7300 analog. Furthermore, ILB-3101 shows strong anti-tumor activity on Dxd based ADC resistant tumors in xenograft tumor models. The PK study of ILB-3101 in cynomolgus monkeys shows dose-dependent exposure and desirable PK profile. ILB-3101 was well tolerated in cynomolgus monkeys with HNSTD at 6 mg/kg. No serious adverse events were observed, and the main safety findings were limited and reversible hematological and immunological effects, which are consistent with the safety profile of Eribulin as an approved chemotherapy. The in vitro and in vivo preclinical results above demonstrate that ILB-3101 has good efficacy and safety profile and it is a promising and potentially best-in-class B7H3 targeting ADC drug candidate. ILB-3101 is worthy of further translational research and clinical trials. Its IND application has been submitted in China, followed by US FDA filing soon. Citation Format: Yushuan Shang, Junzhuan Qiu, Yanfei Xin, Min Zhao, Qiang Liu, Zhengsheng Wang, Xiaojing Gong, Yan Xu, Yan Li, Mingde Xia, Rulei Chen. ILB-3101, a novel B7H3-targeting ADC with Eribulin as payload, demonstrates strong tumor killing activities and favorable PK/TOX profile in preclinical evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5087.