T cell circuits that sense antigen density with an ultrasensitive threshold

Abstract

Overexpressed tumor associated antigens (e.g., HER2 and epidermal growth factor receptor) are attractive targets for therapeutic T cells, but toxic “off-tumor” cross-reaction with normal tissues expressing low levels of target antigen can occur with Chimeric Antigen Receptor (CAR) T cells. Inspired by natural ultrasensitive response circuits, we engineered a two-step positive feedback circuit that allows T cells to discriminate targets based on a sigmoidal antigen density threshold. In this circuit, a low affinity synthetic Notch receptor for HER2 controls the expression of a high affinity CAR for HER2. Increasing HER2 density thus has cooperative effects on T cells—it both increases CAR expression and activation—leading to a sigmoidal response. T cells with this circuit show sharp discrimination between target cells expressing normal amounts of HER2 and cancer cells expressing 100-fold more HER2, both in vitro and in vivo.

More Than Meets the Eye: Scientific Rationale behind Molecular Imaging and Therapeutic Targeting of Prostate-Specific Membrane Antigen (PSMA) in Metastatic Prostate Cancer and Beyond

“…Cohorts 1 and 2 allow the maximum tolerated dose of CART-PSMA-TGFβRDN cells to be identified, while cyclophosphamide in cohort 3 before CAR T cells is used as conditioning chemotherapy. New approaches to design CAR T cells might increase possibilities to develop efficient PSMA-based T cell therapies [ 117 ].…”

Pharmacologic Control of CAR T Cells

“…However, small pharmacologic molecules may also display drawbacks such as a paucity of tissue specificity responsible for an extended diffusion in the body and, in some cases, of cell penetration to reach the target. Beyond the use of small molecules, it is worth mentioning recent efforts to provide non-invasive control over the time, location, and dosage of CARs using either reversible optogenetic or rational designs of dual antigen sensing, such as inhibitory CARs or synNotch positive-feedback circuits sensing antigen threshold [ 128 , 129 , 130 , 131 ].…”

Doubling down with CAR-T cell cancer immunotherapy: a two-step recognition circuit enables discrimination between target antigen high and low cancer cells

“…In a recent article published in Science by Hernandez-Lopez et al chimeric antigen receptor (CAR) expressing T (CAR-T) cells with a two-step recognition system successfully discriminated between target cells expressing high and low levels of their target antigen, which enabled the specific rejection of solid tumour xenograft. 1 …”

“…Hernandez-Lopez et al in a recent publication offered an elegant, new approach termed “two-step recognition circuit”. 1 The authors have developed a synNotch-controlled gene expression system in which low affinity HER-2 specific CAR recognizing high, but not low, levels of HER-2 expressed on tumour cells induces the expression of a high affinity HER-2-specific 2nd generation CAR on the T-cell surface (Fig. 1 ).…”

“…Interestingly, the authors have shown that CAR-T cells with the two-step recognition circuit efficiently killed spheroids of HER-2-high tumour cells, kept some killing activity on proximal HER-2-low spheroids but lost this killing activity on more distant HER-2-low cells. 1 This characteristic is beneficial as it enables killing of tumour variant with lower target antigen expression in the tumour microenvironment, while sparing more distal cells with low levels of the same target antigen. Hernandez-Lopez et al utilized the sequence of 4D5-8 or trastuzumab, which is an established therapy in breast and gastric cancers.…”