PDI-1

PDI-1 is a **small molecule antagonist** specifically designed to inhibit the interaction between **programmed death 1 (PD-1)** and **programmed death ligand-1 (PD-L1)**, both key immune checkpoint proteins. By competitively blocking PD-1/PD-L1 binding, PDI-1 relieves PD-1/PD-L1-induced T cell exhaustion, enhancing T cell-mediated immune responses against tumor cells. In preclinical models, PDI-1 demonstrated potent anti-tumor activity both in vitro and in vivo, increased cytotoxicity and cytokine production by activated T cells, and produced anti-tumor effects comparable to the anti-PD-L1 monoclonal antibody atezolizumab. The drug's mechanism represents an alternative or complementary approach to antibody-based immune checkpoint inhibitors[1].