PD-L1-blocking antibodies produce significant clinical benefit in selected cancer patients by reactivating functionally-impaired antigen-experienced anticancer T cells. However， the efficacy of current PD-L1-blocking antibodies is potentially reduced by 'on-target/off-tumor' binding to PD-L1 widely expressed on normal cells. This lack of tumor selectivity may induce a generalized activation of all antigen-experienced T cells which may explain the frequent occurrence of autoimmune-related adverse events during and after treatment. To address these issues， we constructed a bispecific antibody (bsAb)， designated PD-L1xEGFR， to direct PD-L1-blockade to EGFR-expressing cancer cells and to more selectively re... More
PD-L1-blocking antibodies produce significant clinical benefit in selected cancer patients by reactivating functionally-impaired antigen-experienced anticancer T cells. However， the efficacy of current PD-L1-blocking antibodies is potentially reduced by 'on-target/off-tumor' binding to PD-L1 widely expressed on normal cells. This lack of tumor selectivity may induce a generalized activation of all antigen-experienced T cells which may explain the frequent occurrence of autoimmune-related adverse events during and after treatment. To address these issues， we constructed a bispecific antibody (bsAb)， designated PD-L1xEGFR， to direct PD-L1-blockade to EGFR-expressing cancer cells and to more selectively reactivate anticancer T cells. Indeed， the IC50 of PD-L1xEGFR for blocking PD-L1 on EGFR cancer cells was ∼140 fold lower compared to that of the analogous PD-L1-blocking bsAb PD-L1xMock with irrelevant target antigen specificity. Importantly， activation status， IFN-γ production， and oncolytic activity of anti-CD3xanti-EpCAM-redirected T cells was enhanced when cocultured with EGFR-expressing carcinoma cells. Similarly， the capacity of PD-L1xEGFR to promote proliferation and IFN-γ production by CMVpp65-directed CD8 effector T cells was enhanced when cocultured with EGFR-expressing CMVpp65-transfected cancer cells. In contrast， the clinically-used PD-L1-blocking antibody MEDI4736 (durvalumab) promoted T cell activation indiscriminate of EGFR expression on cancer cells. Additionally， in mice xenografted with EGFR-expressing cancer cells In-PD-L1xEGFR showed a significantly higher tumor uptake compared to In-PD-L1xMock. In conclusion， PD-L1xEGFR blocks the PD-1/PD-L1 immune checkpoint in an EGFR-directed manner， thereby promoting the selective reactivation of anticancer T cells. This novel targeted approach may be useful to enhance efficacy and safety of PD-1/PD-L1 checkpoint blockade in EGFR-overexpressing malignancies.
