CAR T cells targeting α_vβ₃ integrin are effective against advanced cancer in preclinical models

Integrins are heterodimeric receptors that convey cell-to-cell and cell-to-matrix interactions. Integrin α_vβ₃ is expressed in several tumour entities including melanoma, glioblastoma, breast, pancreatic and prostate cancer, where it promotes tumour cell survival and metastasis. Here, we generated α_vβ₃-specific chimeric antigen receptor (CAR) T-cells and analysed their antitumour function in pre-clinical models in vitro and in vivo.

α_vβ₃-CARs comprising a super-humanised hLM609 targeting domain with either high or low affinity (hLM609v7, K _d = 3 nM vs. hLM609v11, K _d = 160 nM) and equipped with either a long or a short IgG4-Fc extracellular spacer (229 vs. 12 amino acids) were expressed in CD8⁺ and CD4⁺ T-cells through lentiviral transduction.

α_vβ₃-CAR T-cells eliminated α_vβ₃-positive tumour cells rapidly and specifically, produced IFN-γ and IL-2 (CD4⁺ > CD8⁺) and exhibited productive proliferation. In vitro, we observed the strongest reactivity with the higher-affinity hLM609v7 α_vβ₃-CAR in the short spacer configuration, consistent with the tumour membrane-distal localization of the hLM609 epitope. In a murine xenograft model of metastatic A-375 melanoma, the strongest antitumour effect was mediated by the lower-affinity hLM609v11 α_vβ₃-CAR. Notably, a single administration of hLM609v11 α_vβ₃-CAR T-cells was able to induce complete elimination of melanoma lesions, leading to long-term tumour-free survival.

These data establish α_vβ₃ integrin as a novel target for CAR T-cell immunotherapy, and affirm our previous notion that binding domain affinity and spacer length can be calibrated to augment CAR reactivity.

α_vβ₃-CAR T-cells have therapeutic potential in several prevalent solid tumours, including melanoma and triple-negative breast cancer.