Abstract 3251: QTOLIMOD: A specific TLR9 agonist nanomedicine with high anti-solid tumor activity
Authors: Su Fei , Bai Jun , Li Chen , Wu Yujing , Li Jing , Zhao Xiaobin , Yang Yongsheng , Lee Robert J. 
Published: March 2024

Background Toll-like receptor 9 (TLR9) agonists are extensively studied for cancer treatment, but face challenges in delivery, clearance, and side effects. Our study showed that QTOLIMOD, a 26nt CpG-ODN delivered via QTsomeTM lipid nanoparticle, significantly inhibited tumor growth in MC38-bearing mice (TGI%=99.06%, p&lt;0.001). Here, we report QTOLIMOD's potential for complete tumor rejection, prevention of recurrence, and advantages in safety and immune-cell induction.

Methods C57BL/6 mice were subcutaneously inoculated with 1 × 106 MC38 cells. To assess drug tissue distribution, Cy5-labeled naked CpG-ODN or QTOLIMOD were intratumorally injected and in vivo imaging was conducted. ELISA was utilized to determine the levels of cytokines in serum and tumor samples. Once the tumor volume reached an average size of 80-100 mm3, mice were grouped and intratumorally injected with saline, vehicle, or QTOLIMOD. Tumor volume was calculated using the formula: length × width2 × 1/2.

Results Following intratumoral injection of QTOLIMOD or naked CpG-ODN, free CpG-ODN were significantly reduced within 24 hours, while QTOLIMOD exhibited extended duration of action up to 7 days. Anatomical examination revealed that a dose of 5 mg/kg naked CpG-ODN caused liver and spleen enlargement in mice, whereas QTOLIMOD at the same dose did not cause the adverse events. Immunohistochemical assay indicated a significant increase in the infiltration of macrophages, dendritic cells, and CD8+ T cells at the tumor site after dosing. IL-10, IFN-γ, and IL-12 were significantly upregulated in the tumor samples, but not in the serum. In a dose escalation experiment, tumor suppression were observed with intratumoral injection of 0.5, 1, 1.5, or 2 mg/kg (every 3 days, 5 doses), resulting in tumor growth inhibition rates ranging from 92.5% to 98.8%. In the QTOLIMOD treated groups, complete tumor rejection was achieved in 4 out of 6 animals in the 0.5 mg/kg group and in all animals in the 1-2 mg/kg groups within 56 days. To investigate the effect of QTOLIMOD on tumor recurrence, cured mice were re-inoculated with MC38 tumor cells at a distant site. All cured mice rejected newly inoculated tumors without additional injection, resulting in 100% survival for up to 60 days. In a dosing frequency experiment, mice were administered with QTOLIMOD at 1 mg/kg once every 3, 5, 7, or 14 days for a total of 5 doses. The results suggested that fortnightly dosing of QTOLIMOD is more effective than more frequent dosing.

Conclusions QTOLIMOD exhibits a high intratumoral retention rate, resulting in increased safety, while effectively promoting the expansion and infiltration of immune cells associated with tumors. Moreover, QTOLIMOD demonstrates potent efficacy in inhibiting tumor growth, potentially leading to complete eradication. Furthermore, treatment with QTOLIMOD effectively prevents tumor from recurrence, offering promising long-term effect.

Citation Format: Fei Su, Jun Bai, Chen Li, Yujing Wu, Jing Li, Xiaobin Zhao, Yongsheng Yang, Robert J. Lee. QTOLIMOD: A specific TLR9 agonist nanomedicine with high anti-solid tumor activity [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 3251.