Abstract
Simple SummaryChimeric antigen receptor (CAR) T cell therapy can be associated with substantial side effects primarily due to intense immune activation following treatment, or target antigen recognition on off-tumor tissue. Consequently, temporal and tunable control of CAR T cell activity is of major importance for the clinical translation of innovative CAR designs. This work demonstrates the transcriptional regulation of an anti-CD20 CAR in primary T cells using a drug inducible zinc finger-based transcription factor. The switch system enables titratable induction of CAR expression and CAR T cell effector function with the clinically relevant inducer drug tamoxifen and its metabolites both in vitro and in vivo, whereby CAR activity is strictly dependent on the presence of the inducer drug. The results obtained can readily be transferred to other CARs for which an improved control of expression is required.Chimeric antigen receptor (CAR) T cell therapy has emerged as an attractive strategy for cancer immunotherapy. Despite remarkable success for hematological malignancies, excessive activity and poor control of CAR T cells can result in severe adverse events requiring control strategies to improve safety. This work illustrates the feasibility of a zinc finger-based inducible switch system for transcriptional regulation of an anti-CD20 CAR in primary T cells providing small molecule-inducible control over therapeutic functions. We demonstrate time- and dose-dependent induction of anti-CD20 CAR expression and function with metabolites of the clinically-approved drug tamoxifen, and the absence of background CAR activity in the non-induced state. Inducible CAR T cells executed fine-tuned cytolytic activity against target cells both in vitro and in vivo, whereas CAR-related functions were lost upon drug discontinuation. This zinc finger-based transcriptional control system can be extended to other therapeutically important CARs, thus paving the way for safer cellular therapies.
Highlights
Adoptive transfer of Chimeric antigen receptor (CAR)-modified T cells is emerging as a promising treatment modality for a broad range of cancers
Most advanced in current clinical development is the treatment of B cell malignancies including acute and chronic B cell leukemia as well as B cell non-Hodgkin lymphoma with anti-CD19 CAR T cells that have recently been approved by the FDA [1,2,3]
For drug controlled transcription of the anti-CD20 CAR, a synthetic transcription factor composed of the N1 zinc finger protein, a modified ligand-binding domain of the estrogen receptor (G525R), and the transcriptional activation domain VP64 was constructed based on sequences reported by Beerli et al [35] (Figure 1a)
Summary
Adoptive transfer of CAR-modified T cells is emerging as a promising treatment modality for a broad range of cancers. Most advanced in current clinical development is the treatment of B cell malignancies including acute and chronic B cell leukemia as well as B cell non-Hodgkin lymphoma with anti-CD19 CAR T cells that have recently been approved by the FDA [1,2,3]. Despite a pooled overall response rate of 71% across patients with B cell malignancies refractory to standard therapies [4], CAR T cell therapy is associated with unique acute and chronic side effects [5]. Even low expression of the target antigen on normal tissue can result in on-target/off-tumor toxicities. On-target/off-tumor toxicities of CARs targeting alternative, non-B cell antigens may cause life-threatening toxicities if tissues of vital organs are damaged [13,14]
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