Author ORCID Identifier

0000-0001-9384-1287

Date of Graduation

5-2022

Document Type

Dissertation (PhD)

Program Affiliation

Cancer Biology

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

David Piwnica-Worms, M.D., Ph.D.

Committee Member

Scott Evans, M.D.

Committee Member

Jeffrey Molldrem, M.D.

Committee Member

Padmanee Sharma, M.D., Ph.D.

Committee Member

Wendy Woodward, M.D., Ph.D.

Abstract

Radioimmunotherapy involves the selective targeting of therapeutic radionuclides to cancer-associated cell surface antigens using monoclonal antibodies. Radioimmunotherapy has been successful in treating hematologic cancers, such as non-Hodgkin’s Lymphoma. However, treatment of solid tumors by radioimmunotherapy remains a challenge, driven in part by a lack of high affinity antibodies against highly tumor-selective surface antigens. Herein, we characterize novel anti-B7-H3 immuno-conjugates for PET imaging and RIT of solid tumors in preclinical models.

Human B7-H3 (CD276) protein is highly expressed on solid tumor cell surfaces and endovascular surfaces in a wide variety of cancers (colon, breast, pancreatic, prostate, head and neck, glioblastoma, ovarian, and non-squamous cell lung cancer), and is low or absent in normal tissues, an ideal RIT target. First, we developed in-house a high affinity (picomolar) dual species (human, mouse) anti-B7-H3 antibody (MIL33B), validated through biolayer interferometry and ELISA. AF594-labeled MIL33B showed membrane-associated staining of tumor cells natively expressing or induced to overexpress B7-H3, displacement by unlabeled MIL33B, and no staining in knockout cell lines and isotype control, confirming specificity. MIL33B labeled with 89Zr (89Zr-DFO-MIL33B) for PET/CT imaging demonstrated high retention in multiple syngeneic tumor models transfected with human B7-H3 compared to vector controls or tumors imaged with isotype control antibody (89Zr-DFO-IgG2a) and in immunodeficient tumor models with high B7-H3 tumor expression compared to B7-H3 KO tumors.

Next, a single intravenous administration of MIL33B labeled with Yttrium-90 (90Y-DOTA-MIL33B; 100 mCi), a therapeutic beta-emitter, induced complete tumor regression and long-term survival of greater than 50% of mice harboring established syngeneic subcutaneous CT26 tumors, a radio-resistant colorectal cell type transfected with human B7-H3 (CT26 hB7-H3) compared to with tumors transfected with vector control (CT26 vector). Mice whose tumors regressed in response to 90Y-DOTA-MIL33B treatment developed immunologic memory and in vivo depletion assays demonstrated that CD8b+ cells were necessary to confer the therapeutic effects of 90Y-DOTA-MIL33B. These results point to the promise of 90Y-DOTA-MIL33B radioimmunotherapy as a treatment for solid tumors and as a potential immune modulator.

Keywords

solid tumors, radioimmunotherapy, theranostics, PET, B7-H3, antibody, beta-emitters

Available for download on Thursday, April 27, 2023

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