Previously, we reported on the peptide-HLA-I fusion protein EpCAM-ReTARGTPR, which allows us to redirect the cytotoxic activity of pre-existing anti-CMV CD8pos T cell immunity to selectively eliminate EpCAMpos cancer cells. EpCAM-ReTARGTPR consists of the CMV pp65-derived peptide TPRVTGGGAM (TPR) fused in tandem with a soluble HLA-B*07:02/β2-microglobulin (β2M) molecule and an EpCAM-directed Fab antibody fragment. To further enhance its anticancer activity, we equipped EpCAM-ReTARGTPR with the immune-potentiating cytokine muteins IL2(H16A,F42A) and IFNαR149A, respectively. Both cytokines are engineered to have attenuated affinity for their respective cytokine receptors. Compared to EpCAM-ReTARGTPR, in vitro ... More
Previously, we reported on the peptide-HLA-I fusion protein EpCAM-ReTARGTPR, which allows us to redirect the cytotoxic activity of pre-existing anti-CMV CD8pos T cell immunity to selectively eliminate EpCAMpos cancer cells. EpCAM-ReTARGTPR consists of the CMV pp65-derived peptide TPRVTGGGAM (TPR) fused in tandem with a soluble HLA-B*07:02/β2-microglobulin (β2M) molecule and an EpCAM-directed Fab antibody fragment. To further enhance its anticancer activity, we equipped EpCAM-ReTARGTPR with the immune-potentiating cytokine muteins IL2(H16A,F42A) and IFNαR149A, respectively. Both cytokines are engineered to have attenuated affinity for their respective cytokine receptors. Compared to EpCAM-ReTARGTPR, in vitro treatment of EpCAMpos carcinoma cell lines with EpCAM-ReTARGTPRvIL2 for 24 h increased the cytotoxic activity of PBMCs containing low levels of TPR-specific CD8pos T cells by ~15%, whereas EpCAM-ReTARGTPRIFNαR149A induced an increase of ~50%. Moreover, treatment for 120 h with EpCAM-ReTARGTPRIFNαR149A inhibited the proliferative capacity of the cancer cell lines OvCAR3 and PC3M by ~91% without compromising the viability of the TPR-specific CD8pos T cells and increased their capacity for IFNγ secretion. Importantly, EpCAM-ReTARGTPRIFNαR149A potently induced the elimination of primary EpCAMpos refractory carcinoma cells from a Merkel cell carcinoma (MCC) patient. Taken together, the armoring of the carcinoma-directed peptide-HLA-I fusion protein EpCAM-ReTARGTPR with IFNαR149A potently enhanced the efficacy of pre-existing anti-CMV CD8pos T cell immunity to selectively eliminate EpCAMpos cancer cells.
