Discovery of Small and Bifunctional Molecules Targeting PD-L1/CD73 for Cancer Dual Immunotherapy

In this work, a series of bifunctional PD-L1/CD73 (cluster of differentiation 73) small-molecule inhibitors were designed and synthesized. Among them, CC-5 showed the strongest PD-L1 inhibitory effects with an IC₅₀ of 6 nM and potent anti-CD73 activity with an IC₅₀ of 0.773 μM. The high PD-L1/CD73 inhibitory activity of CC-5 was further confirmed by SPR assays with K_D of 182 nM for human PD-L1 and 101 nM for CD73, respectively. Importantly, CC-5 significantly suppressed tumor growth in a CT26 and B16–F10 tumor model with TGI of 64.3% and 39.6%, respectively. Immunohistochemical (IHC) and flow cytometry analysis of tumor-infiltrating lymphocytes (TILs) indicated that CC-5 exerted anticancer effects via activating the tumor immune microenvironment. Collectively, CC-5 represents the first dual PD-L1/CD73 inhibitor worthy of further research as a bifunctional immunotherapeutic agent.