Discovery and optimization of betulinic acid derivatives as novel potent CD73 inhibitors.

The vast research and clinical result have verified the success of cancer immunotherapy. However, there is also facing the enormous challenges such as lack of precise pre-clinical models, optimal combined therapy regimen and acquired resistance to immunotherapy. Adenosine is a potent immune-modulating molecule and overexpression of CD73 on tumor leads to the high concentration of adenosine. Blockade of the key adenosine-generating enzyme CD73 can be a promising strategy for cancer immunotherapy. Here, we report the discovery of betulinic acid as a novel CD73 inhibitor lead compound by a hit-based substructure search strategy. Subsequent optimization led to the discovery of betulinic acid carbamate derivative ZM514 with 5.2-fold increased potency compared to lead compound. Simultaneously, study has showed that compound ZM514 was not a cytotoxic agent while betulinic acid showed modest antiproliferative activity. The present result provides a valuable inhibitor against the promising immuno-oncology target for further development.