Delivery Of Immunomodulators To The Acidic Tumor Microenvironment By Ultra-Ph Sensitive Nanoparticle Technology

Background: Immunotherapy has become a powerful strategy for cancer treatment. Immunomodulators such as cytokines (e.g. IL-2) and engineered antibody fragments (e.g. bispecific diabodies) can induce anti-tumor immune responses, but their clinical applications are limited by the unfavorable pharmacokinetic properties that can elicit serious dose-limiting toxicities (e.g. vascular leak syndrome). We have developed an ultra-pH sensitive nanoparticle platform, ONM-400, that delivers biomacromolecules to the acidic tumor microenvironment (TME) with high specificity. At normal physiological pH, the nanoparticles exist as intact micelles, stabilizing the payload, while at acidic tumor pH, they dissociate into unimers, releasing the payload. The feasibility of selectively targeting the acidic TME by this technology has been successfully validated by imaging of different types of tumors in a Phase 1 clinical trial. Using this platform, we have encapsulated and delivered IL-2 and an antibody fragment Fab to the TME to improve their pharmacokinetic properties. Methods: Multiple strategies have been exploited to encapsulate IL-2 and Fab antibody fragment including mixing, single emulsion, acid/base titration, double emulsion/solvent evaporation, and covalent conjugation. ONM-400•IL-2 and ONM-400•Fab complexes were purified by ultracentrifugation and characterized by dynamic light scattering. Encapsulation efficiency (EE) and drug loading (DL) were measured for each formulation using gel electrophoresis. In addition, IL-2 and Fab were labeled with a near-infrared dye (IRDye 800CW) to study the in vivo tumor accumulation and biodistribution after intravenous injection in mice bearing orthotopic head and neck tumors using a LI-COR Pearl camera. Results: ONM-400 nanoparticles were able to encapsulate IL-2 and Fab with high loading. In vivo imaging of ONM-400•IL-2 and ONM-400•Fab showed significantly higher tumor accumulation and less signal in the bladder compared to free IL-2 or Fab at the same dose after IV injection. ONM-400 formulations provided longer and increased exposure in tumor compared to the free biomacromolecules which decreased overtime. Quantitative analysis of the tumor signal at different time points indicated an alteration of the pharmacokinetics for IL-2 and Fab after encapsulation by ONM-400 nanoparticles. Biodistribution at 24h further revealed a lower accumulation in kidney and higher accumulation in tumor with ONM-400•IL-2 and ONM-400•Fab than free IL-2 or Fab respectively. Conclusion: The ONM-400 nanoparticles can efficiently encapsulate immunomodulators and alter their pharmacokinetics in vivo. These results suggest a great potential for using this ultra-pH sensitive nanoparticle technology to deliver immunomodulators to improve their efficacy and safety profile. Citation Format: Xinliang Ding, Jason Miller, Ashley Campbell, Jonathan Almazan, Stephen Gutowski, Tian Zhao. Delivery of immunomodulators to the acidic tumor microenvironment by ultra-pH sensitive nanoparticle technology [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2867.