Antitumor agent-169 (Compound B3) is a dual inhibitor of PD-1/PD-L1 interaction and PARP7, with IC50 values of 0.426 μM and 2.50 nM, respectively. It exhibits affinity for human PD-L1 with a Ki of 20.2 nM and can restore T cell function by increasing IFN-γ secretion. Antitumor agent-169 inhibits cell viability in MDA-MB-231 and Jurkat T cells, demonstrates antitumor activity against melanoma in mouse models, and possesses favorable pharmacokinetic properties.