Abstract 6739: Efficacy and toxicity of microbial mimetic mesoporous silica nanoparticles in a mouse model of ovarian cancer

Abstract Ovarian cancer is predominately left undetected and untreated until the later stages of the disease where it becomes incredibly difficult to treat. Preclinical studies demonstrate that immunotherapy can be highly effective. Our lab has been working on an immunotherapy approach to treat women with ovarian cancer that utilizes mesoporous silica nanoparticles(MSN). MSN that present pathogen-associated molecular patterns (PAMPS) are able to significantly reduce tumor burden in mouse models of serous epithelial ovarian cancer when administered by intraperitoneal injection. These microbial mimetic particles are decorated with polyethyleneimine (PEI), CpG oligonucleotide, and monophosphoryl lipid A (MPLA). When in the presence of antigen presenting cells, they bind to Toll-like receptors (TLR) present on the cell surface and within the endosome. To better understand mechanisms underlying their efficacy, we injected fluorescent MSN-PEI-CpG-MPLA (100 or 500 nm) or unmodified MSN into mice with advanced ovarian cancer. The particles, regardless of the presence of TLR-agonists, were rapidly internalized by myeloid cells, with trafficking almost exclusively to immune clusters located in tumor-burdened adipose tissues when administered by intraperitoneal injection. Conversely, intravenous injection of MSN-PEI-CpG-MPLA led to predominate accumulation in liver, with no particles found in tertiary lymphoid clusters 24 hours post injection. Furthermore, unlike intraperitoneal injection, intravenous injection of MSN-PEI-CpG-MPLA was without therapeutic effect. Currently we are studying MSN safety and the impact of administration route and dose on efficacy and cytotoxicity. In summary, MSN, with and without TLR agonists, are trafficked by myeloid cells to tumor-burdened fat-associated lymphoid clusters when administered by intraperitoneal injection. Intraperitoneal injection of TLR-agonist modified MSN effectively reduces tumor burden in mice with ovarian cancer. Citation Format: Lorel Y. Medina, Rita E. Serda, Benjamin Marwedel, Melanie S. Jun, Josh Adogola. Efficacy and toxicity of microbial mimetic mesoporous silica nanoparticles in a mouse model of ovarian cancer [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 6739.