Abstract 689: Strong anti-tumor activity and stability of IL-2/anti IL-2 conjugate SLC-3010 in preclinical experiments

To achieve successful anti-cancer response with IL-2, it is necessary to develop a method delivering selective IL-2 signaling on CD8 T and NK cells than Tregs We report preclinical results with SLC-3010 that consist of IL-2 conjugate with anti-IL-2 antibody named TCB2 TCB2 is a humanized mouse antibody that specifically recognize the epitope on IL-2 where interact with CD25 as demonstrated with crystallography To develop SLC-3010, stable cell lines producing wild type human IL-2 or TCB2 were separately manufactured using mammalian cell system The pharmacokinetics analysis of SLC-3010 revealed 8-12h of half-life in mouse Although SLC-3010 dose not employ any artificial linker between IL-2 and TCB2, the half-life of SLC-3010 is comparable with other IL-2 based molecules thereby demonstrating stable binding of TCB2 against IL-2 under physiological condition In mouse model, single dosing of SLC-3010 preferentially stimulates CD8 T cells than Tregs in both secondary lymphoid organ and tumor microenvironment SLC-3010 exhibited strong anti-tumor activity which is demonstrated with circulating B cell lymphoma, metastatic solid tumor, and traditional solid tumor models Furthermore, synergistic anti-tumor response was observed by SLC-3010 with various anti-cancer drugs including chemotherapeutic reagents, targeted therapeutics, and checkpoint inhibitors such as anti PD-1 and anti CTLA-4 Once the transplanted tumor was completely cured by SLC-3010, the mice acquired strong memory response against the rejected tumor indicating strong immunological memory formation against recurrent tumors Non-human primate (NHP) efficacy test revealed that single dosing of SLC-3010 expanded CD8 T and NK cells in dose dependent manner, hence the number of CD8 T cells were increased up to 5 fold in the PBMC population with non-toxic dose of SLC3010 The peak of response in NHP was day 6-7 as analyzed the number of CD8 T cells in PBMC The strong activation of CD8 and NK cells with NHP model indicating that the binding of TCB2 and IL-2 is stable in the system as well The SLC-3010 induced selective stimulation of CD8 T cells was also demonstrated with human T cells using humanized NSG mice thereby providing an insight for developing future clinical trials with SLC-3010. Citation Format: Geon-A Kim, Da-Eun Kim, Yoo-Jin Kim, Kyung-Mi Han, Hee-Sung Kim, Soon-Hye Park, Jae-Hyun Park, Eun-Jihn Roh, Gil-Tae Wie, Jun-Young Lee. Strong anti-tumor activity and stability of IL-2/anti IL-2 conjugate SLC-3010 in preclinical experiments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 689.