Application of a fluorine strategy in the lead optimization of betulinic acid to the discovery of potent CD73 inhibitors

Novel active fluorinated betulinic acid derivatives have been discovered by a fluorine scanning strategy. Three compounds ZM522 , ZM553 and ZM557 showed the 7-fold, 5-fold and 8-fold increased activities compared with that of the positive drug APCP against human CD73 enzyme. • Novel active fluorinated betulinic acid derivatives have been discovered by a fluorine scanning strategy. • Compounds ZM522 , ZM553 and ZM557 exhibited the inhibitory activity with the IC 50 value of 0.56 uM, 0.74 uM and 0.47 uM, respectively. • Compounds ZM522 and ZM553 exhibited effective INF-γ elevation and indicated the regulation of rescued T cells activation. The ecto-5'-nucleotidase (CD73) is an important enzyme in the adenosine pathway and catalyzes the extracellular hydrolysis of adenosine monophosphate (AMP) yielding adenosine which is involved in the inflammation and immunosuppression. Inhibitors of CD73 have potential as novel immunotherapy agents for the treatment of cancer and infection. In this study, we discovered a series of fluorinated betulinic acid derivatives as potent CD73 inhibitors by a fluorine scanning strategy. Among these, three compounds ZM522 , ZM553 and ZM557 exhibited inhibitory activity with IC 50 values of 0.56 uM, 0.74 uM and 0.47 uM, respectively. In addition, these compounds showed a 7-fold, 5-fold and 8-fold increase in activity compared to the positive control drug α, β-methylene adenosine diphosphate (APCP) against the human CD73 enzyme. Two of these ( ZM522 and ZM553 ) also exhibited effective interferon gamma (INF-γ) elevation and indicated the regulation of rescued T cell activation. Therefore, our study provides both a lead optimization strategy and potential compounds for further development of small molecule CD73 inhibitors.