RESET: A reversible TCR-coupled antigen receptor with superior targeting sensitivity and pharmacologically controlled anti-tumor activity

Chimeric antigen receptor (CAR) T cells are effective cancer therapies, particularly in indications with high, stable, and tumor-specific antigen expression. Other settings may require improved targeting sensitivity, controllable targeting selectivity, and/or additional potency enhancements to achieve robust efficacy. Here, we describe a novel receptor architecture called RESET (rapamycin-enabled, switchable endogenous T-cell receptor) that combines: (i) cell surface antigen targeting; (ii) small-molecule regulation; and (iii) the signaling proficiency and inherent sensitivity of native T-cell receptors. RESET-T cells outperformed both constitutive and drug-regulated CAR-T cells and show hallmarks of TCR activation that suggest improved fidelity to native T-cell responses. Pharmacological control then increases safety through toggling T-cell activation between active and resting states and may mitigate T- cell exhaustion caused by continuous antigen exposure. This convergence of drug-regulated targeting and natural immune receptor signal transduction may better replicate the kinetics and physiology of a classical T-cell responses and potentiate more successful and safer immunotherapies. T cells from N=4 healthy donors were transduced with RESET, DARIC, CAR, TCR, or untransduced control were cultured either alone or with A549 cells engineered to overexpress the antigen of interest (CD33 or MAGEA4-HLA-A:0201) in the presence or absence of 1nM rapamycin for 18h. Following coculture, T cells were isolated from tumor cells using MACS sorting, tested for purity using flow cytometry, then RNA was isolated and evaluated by RNA-seq.