Remote control of CAR T cell therapies by thermal targeting

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Miller, Ian Contado
Kwong, Gabriel A.
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In 2017, the FDA approved two T cell therapies – Kymriah and Yescarta – for multiple relapsed or refractory hematological malignancies. In addition to providing new treatment options for patients with few viable alternatives, these approvals served as a watershed moment for an emerging class of cellular therapies based on T cells. As the use of these ‘living drugs’ grows, scientists, engineers, and clinicians continue to improve their therapeutic and safety profiles by developing new mechanisms to control immune cell activity in the body. Currently, the limited ability to control cytotoxicity within immunosuppressive tumors contributes to poor CAR T cell responses against solid malignancies. Systemic delivery of biologic drugs such as cytokines or checkpoint blockade inhibitors can augment T cell activity despite off-target toxicity in healthy tissues that narrows their therapeutic window. Thus, localizing the activity of adjuvant drugs and cytotoxicity of T cells to the tumor microenvironment constitutes an important goal for future immunotherapies. In this context, this thesis presents a remote control platform that enables localized control of engineered T cell activity via targeted thermal treatments. By re-engineering the cellular response to mild hyperthermia, I enhance the anti-tumor activity of therapeutic T cells through the heat-induced expression of immunostimulatory genes including Chimeric Antigen Receptors (CARs), cytokine superagonists, and Bispecific T cell Engagers (BiTEs). Aim 1 describes efforts to construct thermal gene switches using truncated sections of an endogenous heat shock promoter. It also introduces a photothermal method for targeted in vivo heating as well as pulsatile heating regimens which improve thermal tolerance and enhance switch activity in engineered cells compared to continuous heat treatments with an identical AUC. Aim 2 describes the design of synthetic thermal gene switches which exhibit lower basal activity and enhanced specificity for thermal cues compared to genomic sequences. In primary human T cells, these synthetic thermal gene switches enable control of critical effector functions such as proliferation and cytotoxicity against cancer cells. Using adoptive cell transfer in murine models of cancer, I demonstrate that photothermal control of engineered T cells improves their anti-tumor activity and treatment outcome. In the future, thermal control of engineered T cells could provide finer control of their in vivo activity and improve the safety and efficacy of next generation cellular therapies.
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