Abstract 4033: Leukocyte-based biomimetic nanoparticles for combined targeted and immunotherapy in osteosarcoma
Authors: Romano Gabriele , Ha Binh , Yustein Jason T. , Taraballi Francesca 
Published: March 2024

Osteosarcoma is the most diffuse bone cancer in the pediatric population, with most patients showing resistance to therapy. All patients are administered systemic high-dose cytotoxic chemotherapy regimens. Many targeted and immune therapy approaches are currently in clinical trials for treating osteosarcoma, but single treatments are not showing promise. While combined targeted and immunotherapy appears to be a possible avenue, developing solutions for patients who show intolerable toxicity or lack of synergy is critical. Nanoparticles (NPs) have successfully been used to prolong the half-life of drugs, favor extended release, reduce systemic toxicity, and reach beyond biological barriers. Biomimetic NPs represent an emerging class of NPs as a system to mimic naturally occurring processes. One class of biomimetic NPs is leukosomes, leukocyte-based biomimetic NPs that target inflamed tissues. Leukosomes are synthesized by integrating proteins isolated from the membranes of circulating leukocytes in the NPs' wall. Leukosomes' biomolecular profile helps them adhere to tumor-inflamed vasculature and promotes their self-tolerance and ability to evade immune clearance from the mononuclear phagocyte system (MPS). We have demonstrated the feasibility of a "one-two punch" approach for leukosome-mediated bone cancer treatment. Specifically, the first "punch" (a multi tyrosine kinase inhibitor, mTKI) induces an immunogenic response, which is subsequently targeted by leukosomes delivering a second class of compounds (immunomodulating nucleic acids, second "punch"). Indeed, even a single mTKI administration increases the amount of leukosomes localized to tumors, which is amplified by a second dosage in a dose-dependent manner. Importantly, leukosome infiltration was paralleled by an increase in immune infiltration, especially in Cd8+ T-cell abundance and macrophages. After several iterations and protocol adjustments, leukosome compositions and microfluidic parameters have been optimized to load either siRNA or mRNA. Current experiments are optimizing the "second punch" targeting immune checkpoint inhibitors (siRNAs vs. PD1/PDL-1). Interestingly, we showed the leukosomes produced using the membranes of human or mouse macrophages pre-treated with LPS show increased surface concentration of adhesion molecules (e.g., Siglec-1) that further enhance their localization at the inflamed site while decreasing filtration by the MPS. In addition to increased delivery to the tumor site, this strategy reduces the therapeutic strain because it is sequential ("one-two punch") and uses nucleic acids instead of antibodies to target immune checkpoints. Overall, our work describes a novel rationale-based sequential approach that can be paradigm-shifting in the field as it harnesses treatment-induced inflammation to boost intratumoral drug delivery.

Citation Format: Gabriele Romano, Binh Ha, Jason T. Yustein, Francesca Taraballi. Leukocyte-based biomimetic nanoparticles for combined targeted and immunotherapy in osteosarcoma [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 4033.