CAR T cells targeting αvβ3 integrin are effective against advanced cancer in preclinical models.

OBJECTIVE: Integrins are heterodimeric receptors that convey cell-to-cell and cell-to-matrix interactions. Integrin αvβ3 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 αvβ3-specific chimeric antigen receptor (CAR) T-cells and analysed their antitumour function in pre-clinical models in vitro and in vivo.
METHODS: αvβ3-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.
RESULTS: αvβ3-CAR T-cells eliminated αvβ3-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 αvβ3-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 αvβ3-CAR. Notably, a single administration of hLM609v11 αvβ3-CAR T-cells was able to induce complete elimination of melanoma lesions, leading to long-term tumour-free survival.
CONCLUSIONS: These data establish αvβ3 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. CLINICAL IMPLICATIONS: αvβ3-CAR T-cells have therapeutic potential in several prevalent solid tumours, including melanoma and triple-negative breast cancer.