Abstract LB001: Encapsulation of IL-12 with an ultra pH-sensitive nanoparticle platform improves tolerability and promotes antitumor response in mice

Abstract Background: Interleukin-12 is a potent proinflammatory cytokine that proliferates and activates T cells, NK cells and differentiates Th1 cells. Translation of IL-12 for cancer treatment has been hindered by lethal toxicities due to cytokine release syndrome and there are currently no approved IL-12 therapies. To minimize the severe toxicities while maintaining potency, we have developed ON-BOARD, an ultra-pH sensitive nanoparticle platform for masked and targeted delivery of payloads to the acidic tumor microenvironment. The clinical feasibility of ON-BOARD has been demonstrated by high tumor specificity of pegsitacianine in multiple tumor types from the Phase I and II clinical trials. Herein we report encapsulation and masked delivery of IL-12 to tumor-bearing mice using ON-BOARD, demonstrating significantly improved tolerability, anti-tumor efficacy, and potential for clinical translation. Methods: A mouse IL-12 fused with Fc was formulated in ON-BOARD nanoparticles. Particle properties were characterized and lead formulations were identified by in vitro screening to determine pH-mediated bioactivity in reporter and ELISA assays and stability in mouse plasma. In vivo studies were performed to compare the activity of unencapsulated IL-12 to ON-BOARD/IL-12 formulations. PD response was evaluated by measuring systemic cytokine levels in plasma, while clinical chemistry was performed to evaluate liver and kidney functions. Anti-tumor efficacy of ON-BOARD/IL-12 formulations was performed in mice bearing syngeneic MC38 colorectal cancer tumors compared to unencapsulated IL-12. Results: ON-BOARD/IL-12 formulations showed high encapsulation efficiency (>85%) and drug loading up to 20% wt. in uniformly distributed stable particles (Dh<50nm). pH-specific payload release was confirmed in vitro with >100-fold activation window between the acid-activated and intact formulations. Following incubation in mouse plasma the lead ON-BOARD formulations showed stable IL-12 encapsulation by an ELISA assay. In vivo, ON-BOARD/IL-12 formulations demonstrated significantly improved tolerability compared to unencapsulated IL-12. When dosed at 5µg/dose compared to unencapsulated protein at 1 µg/dose, ON-BOARD/IL-12 demonstrated reduced body weight loss (<2% vs 13%) and decreased liver injury markers AST and ALT. Analysis of systemic cytokines (IFNγ, IL-6, IL-10, TNFα, etc) showed significantly lower levels for ON-BOARD formulations including >1,000-fold reduction in plasma IFNγ level which is known to be directly induced by IL-12 signaling. ON-BOARD/IL-12 formulations also demonstrated strong anti-tumor efficacy in MC38 tumor-bearing animals with >95% TGI and complete responders. Conclusions: The ON-BOARD platform demonstrated potential for masking toxicity and facilitating tumor-specific delivery of IL-12 proteins for cancer therapy. Citation Format: Qingtai Su, Stephen Gutowski, Irina Kalashnikova, Austin Burcham, Bhargavi Allu, Zirong Chen, Zhichen Sun, Jinming Gao, Ruolan Han, Jason B. Miller, Tian Zhao. Encapsulation of IL-12 with an ultra pH-sensitive nanoparticle platform improves tolerability and promotes antitumor response in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB001.