Abstract: Totally 28 new 12N-substituted aloperine derivatives were designed, synthesized and evaluated for their down-regulating PD-L1 activities in breast cancer MDA-MB-231 cells. Among them, compound 7f could significantly down-regulate PD-L1 level in concentration- and time-dependent manners, and exhibit a low cytotoxicity. It activated the killing activity of co-cultured T cells against tumor cells in a concentration-dependent manner, showing the potential of tumor immunotherapy. Further study indicated that 7f mediated the degradation of PD-L1 through a lysosomal pathway. This study provides useful guidance for the development of aloperine compounds into new small molecule tumor immune suppressants.