Umbilical cord mesenchymal stem cell-derived extracellular vesicles (UC-MSC-EVs) have become an emerging strategy for treating various autoimmune and metabolic disorders, particularly diabetes. Delivery of UC-MSC-EVs is essential to ensure optimal efficacy of UC-MSC-EVs. To develop safe and superior EVs-based delivery strategies, we explored nuclear techniques including positron emission tomography (PET) to evaluate the delivery of UC-MSC-EVs in vivo. In this study, human UC-MSC-EVs were first successfully tagged with I-124 to permit PET determination. Intravenous (I.V.) and intra-arterial (I.A.) administration routes of [¹²⁴I]I-UC-MSC-EVs were compared and evaluated by in vivo PET-CT imaging and ex vivo biodistribution in a non-diabetic Lewis (LEW) rat model. For I.A. administration, [¹²⁴I]I-UC-MSC-EVs were directly infused into the pancreatic parenchyma via the celiac artery. PET imaging revealed that the predominant uptake occurred in the liver for both injection routes, and further imaging characterized clearance patterns of [¹²⁴I]I-UC-MSC-EVs. For biodistribution, the uptake (%ID/gram) in the spleen was significantly higher for I.V. administration compared to I.A. administration (1.95 ± 0.03 and 0.43 ± 0.07, respectively). Importantly, the pancreas displayed similar uptake levels between the two modalities (0.20 ± 0.06 for I.V. and 0.24 ± 0.03 for I.A.). Therefore, our initial data revealed that both routes had similar delivery efficiency for [¹²⁴I]I-UC-MSC-EVs except in the spleen and liver, considering that higher spleen uptake could enhance immunomodulatory application of UC-MSC-EVs. These findings could guide the development of safe and efficacious delivery strategies for UC-MSC-EVs in diabetes therapies, in which a minimally invasive I.V. approach would serve as a better delivery strategy. Further confirmation studies are ongoing.

Bispecific T-cell engaging antibodies (BiTES), comprising dual anti-CD3 and anti-tumor antigen scFv fragments, are important therapeutic agents for the treatment of cancer. The dual scFv construct for BiTES requires proper protein folding while their small molecular size leads to rapid kidney clearance. An intact (150 kDa) anti-tumor antigen antibody to CEA was joined in high yield (ca. 30%) to intact (150 kDa) anti-murine and anti-human CD3 antibodies using hinge region specific Click chemistry to form dual-specific, bivalent BiTES (dbBiTES, 300 kDa). dbBiTEs were tested in vitro by EM, flow cytometry and cell cytoxicity and in vivo by PET tumor imaging and redirected T-cell therapy. The interlocked hinge regions are compatible with a structural model that fits the electron micrographs of 300 kDa particles. Compared to intact anti-CEA antibody, dbBiTES exhibit high in vitro cytotoxicity, high in vivo tumor targeting as demonstrated by PET imaging, and redirected dbBiTE coated T-cells (1 microgram/10 million cells) that kill CEA+ target cells in vivo in CEA transgenic mice. dbBiTE redirected T-cell therapy is a promising, efficient approach for targeting and killing cancer cells.

Background/Objectives: Immunocytokines (ICKs) are antibody–cytokine fusion proteins that deliver cytokines directly to tumors to increase immune responses, which are otherwise absent or limited by the delivery of antibodies alone. Tumor-associated glycoprotein-72 (TAG72) is overexpressed in numerous solid tumors. Methods: An anti-TAG72-IL-2 fusion protein was expressed in mammalian cells and tested in vitro for binding and bioactivity, and in vivo in two models. Results: In vitro studies showed high antigen specificity against TAG-72-positive tumor cell lines and IL-2 activity in CD25 (IL-2R)-positive reporter cells. To study the anti-tumor activity of huCC49-IL-2 in an immunocompetent model, the TAG-72 expression was established in murine mammary and colorectal cells by transfection with murine st6galnac-I gene (mSTn). Four daily doses of anti-TAG72-IL-2 monotherapy for TAG-72-expressing orthotopic murine mammary tumors in immunocompetent mice resulted in minimal whole-body toxicity and significant tumor growth reduction mediated by tumor infiltration of IFNγ⁺ CD8⁺ T cells. When mammary tumors were pretreated with image-guided fractionated radiation therapy (IGRT) followed by anti-TAG72-IL-2 therapy, an improved tumor growth inhibition was observed along with an increased tumor infiltration of IFNγ⁺ CD8⁺ T cells and a significant reduction in Foxp3⁺ CD4⁺ cells. Anti-TAG72-IL-2 monotherapy in TAG-72⁺ colorectal tumors led to a significant tumor reduction but also cures (4/7), with a rejection of rechallenges with both TAG-72-positive and -negative MC38 cells, thus demonstrating evidence of immune memory and antigen spreading. Conclusions: antiTAG-72-IL-2 therapy showed strong anti-tumor effects driven by activated CD8⁺ T cells making it a promising approach to the treatment of TAG-72⁺ tumors.

Bispecific T-cell engaging antibodies (BiTES), comprising dual anti-CD3 and anti-tumor antigen scFv fragments, are important therapeutic agents for the treatment of cancer. The dual scFv construct for BiTES requires proper protein folding while their small molecular size leads to rapid kidney clearance. Here we show that an intact (150 kDa) anti-tumor antigen antibody to CEA was joined in high yield (ca. 30%) to intact (150 kDa) anti-murine and anti-human CD3 antibodies using hinge region specific Click chemistry to form dual-specific, bivalent BiTES (db BiTES, 300 kDa). The interlocked hinge regions are compatible with a structural model that fits the electron micrographs of the 300 kDa particles. Compared to intact anti-CEA antibody, dbBiTES maintain high in vivo tumor targeting as demonstrated by PET imaging, and redirect dbBiTE coated T-cells (1 microgram/10 million cells) to kill CEA⁺ target cells both in vitro, and in vivo in CEA transgenic mice.