Date of Award
Summer 8-15-2021
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Immunotherapy has advanced significantly in recent years due to its promising clinical outcomes in a variety of malignancies and holds great promise in becoming the “cure” for cancer. Cancer immunotherapy is the treatment that stimulates a person’s own immune system to recognize, target, and eliminate cancer cells. As the field progresses with emerging and novel strategies, the ability to manipulate the immune system while mitigating toxicities is the goal for clinical translation. To control for both efficacy and safety, biomaterials have been incorporated into immunotherapies to achieve tissue- and/or cell-specific immunomodulation, overcome immunosuppression, and address tumor microenvironment heterogeneity.T cell-based immunotherapy, such as chimeric antigen receptor (CAR)-T cells, has shown promising clinical outcomes in many cancers. CAR-T cells are autologous T cells that have been virally transfected to express an engineered CAR construct, containing a synthesized fragment that targets the desired surface antigen on the target cell. However, this therapy has significant limitations such as toxicity, the long-term safety profile of the viral vector, the need to perform quality control testing frequently throughout the production of CAR-T cells, the high costs associated with extensive labor and expensive facility equipment, complex production, and the inability to target multiple tumor antigens with one CAR-T cell. In addition to CAR-T cells, T cell-based therapy can be pursued with T cell engagers (TCEs). TCEs consists of two single chain variable fragments which are connected by a protein linker. One of the domains recognizes a tumor-associated surface antigen, while the other recognizes the T cell using the CD3 receptor. TCEs demonstrate high potency and efficacy against tumor cells and exploit the use of endogenous T cells, circumventing the limitation of genetically engineering extracted patient T cells to express CARs. The disadvantages of TCEs, however, include toxicity, laborious and tedious production, short pharmacokinetics (PK), and the inability to target multiple cancer surface markers Moreover, both CART and TCE therapies confer the development of antigen-less clones, causing tumor escape and relapse in multi-clonal diseases; and inability to induce T cell persistent activation, ultimately causing T cell exhaustion. We developed nanoparticle-based bispecific T cell engagers (nanoBTCEs), which are liposomes decorated with anti-CD3 monoclonal antibodies targeting T cells, and monoclonal antibodies targeting one cancer antigen. NanoBTCEs 1) have a long half-life of about 60 hours, which enables once-a-week administration instead of continuous infusion; 2) induce T cell activation in the presence of Waldenstrom Macroglobulinemia (WM) and multiple myeloma (MM) cells; and 3) induce T cell-mediated cancer cell lysis of WM and MM cells. Due to the nanoparticulate nature of nanoBTCEs, we solved the PK problem, enabled simple and cheap production, and created an off-the-shelf platform for cancer immunotherapy. For multi-clonal diseases such as MM, we also developed nanoparticle-based multispecific T cell engagers (nanoMuTEs), which are liposomes decorated with anti-CD3 monoclonal antibodies targeting T cells, and monoclonal antibodies targeting more than one cancer antigen. NanoMuTEs targeting multiple cancer antigens showed greater efficacy in MM cells in vitro and in vivo, compared to nanoBTCEs targeting only one cancer antigen. Unlike nanoBTCEs, treatment with nanoMuTEs didn’t cause downregulation (or loss) of a single antigen and prevented the development of antigen-less tumor escape. Our nanoparticle-based immuno-engaging technology provides a solution for the major limitations of current immunotherapy technologies. In addition, a major disadvantage TCEs have is that their T cell activation and persistence is weaker than CAR-T cells, which is why CAR-T cells have a greater anti-tumor response compared to TCEs. Methods to activate T cells include the use of lectins, such as phytohemagglutinin (PHA) which is commonly only used for research purposes ex vivo, but not in vivo. PHA binds to glycoproteins on the T cell receptor and stimulates T cells more significantly compared to other forms of T cell activators such as phorbol 12-myristate 13- acetate, ionomycin, and concanavalin A. Yet, PHA has not been used to activate T cells in vivo, for immunotherapy, due to its biological instability and toxicity. The instability stems from its protein-nature, which causes its degradation and short bioavailability profile in the blood while toxicity can cause death due to agglutination of red and white blood cells. Therefore, to take full advantage of PHA as an immune activator, an approach of circumventing the limitations of PHA while also preserving function is needed. We report the encapsulation of PHA in a liposome which increased the in vivo stability, reduce toxicity, and activated T cells in vitro and in vivo, and induced killing of tumor cells in vitro and in vivo. The liposomal PHA is a new form of pan- cancer immunotherapy which acts regardless of tumor antigens and thus does not induce antigen- less tumor escape while also circumventing current obstacles of T cell exhaustion. In conclusion, our nanoTCE platform uses nanoparticles to create a relatively simple, reproducible, and off-the-shelf solution to overcome the major limitations of current immunotherapy techniques such as TCEs and CAR-T cells. The nanoTCE targets each antigen with the high specificity of monoclonal antibodies which enables the creation of a more robust immunotherapy technology to take advantage of the immune system for an effective response. Our system enables the customization of the nanoTCE as an immunotherapy with the use of existing monoclonal antibodies for the targeting of any desired cancer or immune cell antigen. This simple, customizable, specific, translational, and efficacious nanoTCE platform provides the flexibility to engage any immune cell for the treatment of the cancer of interest and can be used for personalized medicine based on the cancer antigens presented by the patient’s tumor.
Language
English (en)
Chair
Abdel Kareem Azab
Committee Members
Samuel Achilefu, Hong Chen, Michael Kinch, Laura Sun,