The ability of Vɣ9+ ɣ&dgr; T cells to target cancer cells via recognition of phosphoantigens has resulted in treatments such as ImmuniCell®, which is currently being evaluated in an adaptive phase II/III study. In addition, we have developed ɣ&dgr; T cells expressing chimeric antigen receptors (CARs) to maximise the therapeutic potential of both ɣ&dgr; T cell and CAR-T therapy. We rationally designed a CAR construct that takes advantage of the defined antigen specificity of Vɣ9+ ɣ&dgr; T cells resulting in a potential cellular therapy with enhanced effector functions whilst minimising ‘on-target, off-tumour’ side effects.
A CD19 targeting CAR was designed comprising costimulatory domains from CD28 and CD137 (‘signal-2’). This design was tested against a classical CAR, comprising the aforementioned costimulatory domains plus a ‘signal-1’ providing CD3&zgr; activation domain. Vɣ9+ ɣ&dgr; T cells from healthy individuals were expanded in culture, and CAR expression achieved by lentiviral transduction. Ability of transduced ɣ&dgr; &Tgr; cells to target CD19+ cancer cell lines, RAMOS and DAUDI, was assessed using a flow cytometry based cytotoxicity assay.
ɣ&dgr; T cells were successfully transduced with both CAR constructs, these were discriminated by qPCR using two primer sets. ɣ&dgr; &Tgr; cells transduced with either construct exhibited increased cytotoxicity against the CD19+ DAUDI and RAMOS target cells. Strikingly, a 3-fold increase in cytotoxicity was measured against RAMOS cells, which usually display low sensitivity to unmodified ɣ&dgr; &Tgr; cell-mediated killing.
We have demonstrated a novel ɣ&dgr; specific CAR design that does not require incorporation of a CD3&zgr; signalling domain to elicit effector function. ‘Signal 1’ is provided by the ɣ&dgr; T cell receptor (TCR) resulting in a TCR-tuneable CAR construct. As healthy cells do not accumulate phosphoantigens, this CAR design should only elicit effector function against cancer cells, reducing ‘on-target, off tumour’ side effects – a major safety concern. Moreover, CAR expressing ɣ&dgr; &Tgr; cells may result in a potent targeted treatment, as both phosphoantigens and the CAR target contribute to identification and killing of cancerous cells in vivo.
Clinical trial identification
Legal entity responsible for the study
TC BioPharm Limited
TC BioPharm Limited
M.D. Leek: Founder and employee of the presenting institution - TC BioPharm. A. Patakas, A. Hannigan, D. Paruzina: Employee of the institution submitting this abstract.