Enhancing T cell cytotoxicity against lung cancer with an αPD-L1 protein engager and gemcitabine combination therapy

The overexpression of programmed cell death ligand 1 (PD-L1), a critical immune checkpoint protein, is associated with poor prognosis and reduced survival in lung cancer patients. Monoclonal antibodies targeting the PD-1/PD-L1 axis have been approved to disrupt this interaction and prevent immune cell exhaustion. Herein, to enhance the efficacy of PD-1/PD-L1 blockade, we investigated a bispecific αPD-L1 × αCD3 protein engager (αPD-L1 × αCD3 BIPE). The αPD-L1 × αCD3 BIPE consists of an anti-CD3 single-chain variable fragment (scFv) linked to an anti-PD-L1 scFv, allowing it to bind to CD3-positive T cells simultaneously and PD-L1-overexpressing cancer cells. In co-culture assays with T cells and non-small cell lung cancer (NSCLC) cell lines-A549, NCI-H460, and NCI-H1975-treatment with the BIPE significantly enhanced T-cell-mediated cytotoxicity. The killing efficiency correlated with PD-L1 expression levels, with the highest cytotoxic activity observed in NCI-H1975 (high PD-L1 expression), followed by NCI-H460 (moderate PD-L1 expression) and A549 (low PD-L1 expression). Furthermore, combining the BIPE with the standard chemotherapeutic agent gemcitabine further improved anti-tumor activity. This effect was likely due to gemcitabine-induced upregulation of PD-L1 and MHC class I expression on cancer cells, enhancing T-cell recognition and cytotoxicity. These findings suggest that combining αPD-L1 × αCD3 BIPE with gemcitabine is promising for enhancing immune checkpoint blockade and augmenting anti-tumor immunity in NSCLC.