Defense Date
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Pharmaceutical Sciences
First Advisor
Sandro R. P. da. Rocha
Abstract
Osteosarcoma (OS) is the third most common cancer type in children, and metastasizes almost exclusively to the lungs1. While only 20% of patients present with clinically detectable lung lesions at the time of first diagnosis, 80% of the remaining patients are expected to have clinically undetectable micrometastases2,3. Patients that develop detectable OS lung metastases (OSLM), exhibit a 5-year survival rate of < 20%, where lung disease is the leading cause of death4,5. The only potential curative intervention for OSLM is surgical resection, a procedure where outcomes are suboptimal as it is difficult to identify micrometastatic lesions6,7. Immune check point inhibitor (ICI) therapies have also shown little efficacy due to OSLM “cold tumor” characteristics8. Thus, chemotherapy continues to be standard of care treatment despite its inability to improve OSLM patient outcomes in the last four decades9. Challenges associated with chemotherapy to treat OSLM include rapid metabolism, poor biodistribution to the lung tumors, and long-term off target health effects, and sub-therapeutic doses contributing to the development of chemoresistance10 upon systemic administration6,7. Therefore, the development of safe and effective treatments for OSLM represents a critical unmet need clinical need.
GMT is used as a second line chemotherapy in the management of OSLM4. However, its systemic administration exhibits limited response rates for OSLM patients (10% for GMT alone and 20% in combination with docetaxel)11. In contrast, pre-clinical and comparative studies12–14 have shown that when aerosolized to the lungs, GMT has an established safety profile, decreased dose requirements, reduced toxicity, and is currently being investigated in ongoing clinical trials4. Further, aerosolized GMT leads to an upregulation of the Fas cell death receptor in OS tumor cells in the lungs, promoting activation of Fas/FasL mediated apoptosis15. This is important as OS cells significantly downregulate Fas expression upon metastasis to the lungs, eliminating this key apoptotic pathway15. While inhaled GMT leads to a decrease in tumor burden, it does not completely eradicate the tumor16.
Additionally, infiltrating immune cells in the OSLM TME play a critical role in tumor formation, progression, and response to therapies17. Targeting tumor associated macrophages (TAMs), the most abundant immune infiltrates in the OSLM TME with pexidartinib (CSF1 receptor inhibitor: PLX3397) may decrease total TAMs and promote the abundance of classically activated “M1-like” tumor-killing TAMs as seen with other cancer types18,19. Effective macrophage immunotherapy could thus support inhaled GMT, resulting in improved prognosis. However, PLX in high doses results in off-target hepatotoxicity20. Thus, poor lung tissue distribution, high dose requirements, and off target toxicity could be alleviated with pulmonary administration (p.a.) of PLX21.
While local lung delivery of GMT and PLX offers benefits, challenges regarding short residence time of aerosolized drugs in the lungs remains, especially for GMT16. Arikayce (a liposomal suspension formulation) is the only FDA approved nanomedicine for local lung inhalation22. Therefore, pre-formulation of GMT using liposomal nanoparticles serves as the strategy with the greatest potential for clinical translation to increase lung retention time of inhaled therapies for OSLM.
Thus, we hypothesized that GMT chemotherapy and PLX immunotherapy delivered to the lungs would improve treatment outcomes in an immune-competent OSLM mouse model. The objective(s) of this work was to (1) demonstrate that locally delivered GMT chemotherapy to the lungs improves therapeutic outcomes in an immune-competent mouse model of OSLM (2) characterize the immuno-phenotype of the OSLM TME following p.a. of PLX and evaluate overall outcomes of combination PLX+GMT therapy delivered via p.a. and (3) demonstrate that p.a of a L-GMT formulation safely alters the phenotype of OS cells in the lungs. With these 3 pharmacotherapies, we performed in vitro and in vivo experimentation that resulted in a new in-depth understanding of the overall impact of these pharmacotherapies in a murine model of the OSLM TME.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-8-2026