Abstract 1787: Novel strategy for producing ovarian cancer-targeting antibodies using cancer-derived small extracellular vesicles

Introduction: Despite advancements in tumor-targeting agents, meta-analyses reveal that only 0.7% (mean value) of the injected therapeutic dose reaches the tumor site, leading to significant off-target adverse effects. This highlights the need for innovative targeting agents to enhance tumor-targeting efficacy. We developed a novel tumor-targeting antibody production method using cancer-derived small extracellular vesicles (sEVs). Since sEVs inherit their structure and function from their parent cells, the antibodies produced against sEVs could target both cancer cells and sEVs. Using this approach, antibody-decorated drug delivery systems may achieve enhanced tumor-targeting efficiency, overcoming the suboptimal drug concentration in the tumor. Methods: sEVs were isolated from ovarian cancer cells (OVCAR-8) and injected into mice. After confirming the specificity of the collected plasma to OVCAR-8 cells, hybridoma cells were generated by fusing the mice's B cells (antibody-producing cells) with myeloma cells. Hybridomas were screened to produce monoclonal antibodies (mAbs) with the highest cytotoxicity against OVCAR-8 cells (AB1, based on CCK8 assay) and the best OVCAR-8-targeting efficacy (AB2, determined through immunocytochemistry). The antibodies (AB1 and AB2) were purified and conjugated to paclitaxel-loaded CD8+ T cell sEVs (AB-TSEV/P). The formulations (AB1-TSEV/P and AB2-TSEV/P) were injected into OVCAR-8-bearing mice, and tumor volume and body weight were monitored over 80 days. An in vivo biodistribution study was performed using an IVIS Spectrum Imaging System based on fluorescence intensity measurement of IR-780 loaded AB-TSEV (AB-TSEV/IR) to assess tumor-specific accumulation. Results: Characterization showed that both OVCAR-8 and CD8+ T cell-derived sEVs were ∼150 nm in size. Plasma from mice injected with OVCAR-8-derived sEVs demonstrated significantly higher cytotoxicity and targeting specificity against OVCAR-8 cells than non-cancerous HOSE cells. Based on the results from antibody screening, AB1 exhibited the highest cytotoxicity to OVCAR-8 cells, while AB2 showed the best OVCAR-8 cell-targeting efficacy compared to HOSE cells. Tumor volume measurements indicated that AB1-TSEV/P and AB2-TSEV/P significantly reduced tumor growth (p<0.0001) without affecting body weight, suggesting good tolerability. Biodistribution studies showed that antibody-decorated sEVs accumulated significantly (p<0.0001) at the tumor site. Conclusions: We developed an innovative strategy for producing tumor-targeting antibodies using cancer-derived sEVs, significantly enhancing tumor-specific drug delivery. Although focused on ovarian cancer, this approach could be applied to other cancers and diseases, offering a promising method for targeted therapies and addressing the limitations of current treatments. Citation Format: Maryam Firouzi, Changsun Kang, Xiaoyu Ren, Seonghyun Ryu, Dongin Kim. Novel strategy for producing ovarian cancer-targeting antibodies using cancer-derived small extracellular vesicles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1787.