CD73-IN-19 (Compound 4ab) is a CD73 inhibitor (with a 44% inhibition rate of CD73 enzymatic activity at 100 μM). CD73-IN-19 (at 10 μM and 100 μM) can completely antagonize the blockade of T cell proliferation induced by TCR (T cell receptor) triggering (which is induced by CD73 activity), and it can also inhibit the hA2A receptor activity in HEK-293 cells ( K i is 3.31 μM). CD73-IN-19 holds promise for research in the field of immune diseases.