Date of Award

January 2023

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Michael Girardi

Second Advisor

W. M. Saltzman

Abstract

Encapsulation of therapeutic agents within biodegradable nanoparticles (NP) allows for gradual drug release from the nanoparticle core. When injected intravenously, our nonadhesive NPs (NNP) have previously demonstrated longer circulatory time with “stealthy” features, thus allowing for prolonged drug exposure systemically. In the murine transplantable cutaneous squamous cell carcinoma (SCC) PDVC57 model, our bioadhesive NP (BNP) loaded with chemotherapy have shown increased retention of the active agent after intratumoral (i.t.) injection, thus allowing for prolonged drug exposure when locally delivered. Monophosphoryl lipid A (MPLA) is a low-toxicity derivative of LPS with immunomodulating properties. However, MPLA, like other TLR agonists, is a small molecule with poor pharmacokinetic properties in that there is significant potential but underachievement in clinical settings. Therefore NP encapsulation of such immunomodulatory agents may allow for more effective delivery to tumor sites as well as tumor draining lymph nodes (TDLN), thereby enhancing stimulation of anti-tumor immune responses while minimizing systemic side effects. Using the biodegradable NNP and BNP, we encapsulated MPLA and measured effects on improving its immunomodulatory properties. In vitro studies demonstrated that NNP- and BNP-MPLA induce maturation of bone marrow derived dendritic cells (BMDC) with greater cytokine production capacity than that seen with free MPLA. Characterization and uptake studies of the particles in vivo demonstrated that both NNPs and BNPs are retained in lymph nodes after in vivo i.t. delivery. Using the YUMMER1.7 murine melanoma model, we also demonstrated the in vivo efficacy of NNP and BNP-MPLA in inducing antigen presenting cells (APC) in the lymph nodes with more sustained M1 macrophage and DC responses compared to the free agent. Additionally, a time course study revealed that a steady and significant increase in serum IFN-γ was sustained for up to 5 days after a single i.t. injection of NNP-MPLA or BNP-MPLA, which was not observed with the free formulation of the immunomodulator. No systemic toxicity was noted in the treated mice as assessed by weight changes. We further assessed inhibition of melanoma tumor growth in vivo using the immunogenic YUMMER1.7 model. Tumor-bearing mice received two once weekly i.t. injections of BNP-MPLA, free MPLA, or vehicle. BNP-MPLA treated tumors showed significantly reduced tumor growth, with tumor resolution in 12.5% of mice, and improved survival. We then leveraged low-dose chemotherapy in combination with the NPs to further induce an anti-tumor response. Combining adjuvant NNP-MPLA or BNP-MPLA with chemotherapy, SBI-111, significantly increased animal survival in comparison to monotherapy and fully eradicated nodular melanoma tumors in portion of the treated animals, with combination therapy SBI-111 and NNP-MPLA fully eradicating melanoma in 55.6% of mice. These results suggest that our local delivery of encapsulated MPLA via biodegradable NPs is an effective way to improve local delivery of immunomodulatory agents and that adjuvant delivery with chemotherapy is an effective way to promote an anti-tumor immune response against nodular melanoma.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 07/24/2025

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