Najibi Seyedeh A, Pranto S M Al Muied, Haroon Muhammad, Nielsen Amy E, Mancini Rock J
Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA.
Astante Therapeutics Inc., 201 E. Fifth Street, Cincinnati, OH 45202, USA.
Pharmaceuticals (Basel). 2025 May 27;18(6):804. doi: 10.3390/ph18060804.
Despite broad anti-cancer efficacy as Toll-Like Receptor (TLR) 7/8 agonists, imidazoquinolines remain limited in use via systemic administration or in situ vaccination therapies due to inflammatory toxicity. One approach to address this challenge involves better targeting the action of imidazoquinolines by caging them as glycoconjugate prodrugs. Within cancer cells, imidazoquinoline glycoconjugates are activated by hydrolases prior to efflux by ABC transport proteins, where they then elicit tumoricidal effects from the assistance of bystander immune cells, such as tumor-infiltrating lymphocytes and associated macrophages, in local proximity. While this concept of Bystander-Assisted ImmunoTherapy (BAIT) has been established at a molecular level in vitro, tolerability or efficacy of BAIT has not been reported in vivo. Here, we evaluate the MTD and tumor growth delay efficacy of a lead BAIT prodrug (BAIT628) in a male C57BL/6 mouse TRAMP-C2 prostate cancer model to further establish this methodology. Overall, we find that systemic BAIT628 is well tolerated at over 5-fold the dose-limiting inflammatory toxicity of the parent imidazoquinoline (up to 5 mg/mouse/day I.P. for 10 days). Analyzing serum cytokines reveals that IL-10 production, elicited by the mannoside caging group, likely contributes to the enhanced MTD. Using BAIT628 as an in situ vaccination immunotherapy (seven times over 3 weeks) resulted in significant tumor growth delay and increased survival, both alone and in combination with a murinized α-PD-L1 checkpoint blockade. The tumor histology of tumor-infiltrating immune cell subsets (CD4, CD8, CD11c) reveals significant increases in CD11c populations, consistent with TLR7/8 agonism. Overall, BAIT628 is well tolerated and exhibits significant efficacy in the TRAMP-C2 model. These results demonstrate how the BAIT approach can optimize imidazoquinolines for in vivo tolerability and subsequent efficacy as cancer immunotherapeutics.
尽管咪唑喹啉作为Toll样受体（TLR）7/8激动剂具有广泛的抗癌功效，但由于炎症毒性，其通过全身给药或原位疫苗接种疗法的应用仍然有限。应对这一挑战的一种方法是通过将咪唑喹啉作为糖缀合物前药进行笼蔽，从而更好地靶向其作用。在癌细胞内，咪唑喹啉糖缀合物在被ABC转运蛋白外排之前被水解酶激活，然后在局部附近的旁观者免疫细胞（如肿瘤浸润淋巴细胞和相关巨噬细胞）的协助下引发杀肿瘤作用。虽然旁观者辅助免疫疗法（BAIT）这一概念已在体外分子水平得到确立，但尚未有关于BAIT在体内的耐受性或疗效的报道。在此，我们在雄性C57BL/6小鼠TRAMP-C2前列腺癌模型中评估了一种先导BAIT前药（BAIT628）的最大耐受剂量（MTD）和肿瘤生长延迟疗效，以进一步确立该方法。总体而言，我们发现全身给药的BAIT628在超过母体咪唑喹啉剂量限制炎症毒性5倍以上的剂量下具有良好的耐受性（腹腔注射高达5mg/小鼠/天，持续10天）。分析血清细胞因子发现，甘露糖苷笼蔽基团引发的IL-10产生可能有助于提高MTD。使用BAIT628作为原位疫苗接种免疫疗法（3周内进行7次），无论是单独使用还是与鼠源化α-PD-L1检查点阻断联合使用，均导致显著的肿瘤生长延迟和生存率提高。肿瘤浸润免疫细胞亚群（CD4、CD8、CD11c）的肿瘤组织学显示CD11c群体显著增加，这与TLR7/8激动作用一致。总体而言，BAIT628在TRAMP-C2模型中耐受性良好且具有显著疗效。这些结果证明了BAIT方法如何优化咪唑喹啉在体内的耐受性以及随后作为癌症免疫治疗药物的疗效。
