Progettazione e caratterizzazione di costrutti supramolecolari per la fotoimmunoterapia mirata a PD-L1

The use of immunoconjugates with photosensitizing and targeting properties represents a promising strategy for cancer treatment by combining photodynamic therapy (PDT) and immunotherapy. Traditionally, the surface density of tumor-specific receptors, such as programmed death-ligand 1 (PD-L1), has been considered a critical predictor of treatment outcomes. In this study, we developed a photoactive supramolecular system that selectively targets PD-L1 to investigate whether PD-L1 expression levels can determine the efficacy of photoimmunotherapy (PIT). To this end, the photosensitizer EITC or the fluorescent probe Alexa Fluor 647 was conjugated to the FDA-approved PD-L1-binding antibody atezolizumab. We used dSTORM imaging with Alexa Fluor 647-labeled atezolizumab to quantify PD-L1 receptors on two human non-small cell lung cancer (NSCLC) cell lines with differing PD-L1 expression levels and assess atezolizumab’s binding affinity to PD-L1 on these cells. Our results confirmed that the photoimmunoconjugate was effective for PDT, but unexpectedly, there was no observed correlation between PD-L1 surface density and PIT treatment efficacy, suggesting that receptor density may not predict therapeutic outcomes. Additionally, we explored photochemical internalization (PCI) as a means to enhance intracellular delivery through light activation. Although PCI significantly improved the uptake of large molecules like gelonin, it did not enhance PDT efficacy in conjunction with PD-L1 blockade. Confocal microscopy studies further showed that PD-L1 undergoes recycling after internalization, which may reduce the long-term effectiveness of atezolizumab-based therapies by allowing re-expression of functional PD-L1 on the cell surface. These findings broaden the potential applicability of PD-L1-targeted photoimmunotherapy, indicating that even tumors with low PD-L1 expression may respond to PIT.