Luciferase-IN-3 (compound 5h) is an inhibitor of ATP-dependent luciferase (Firefly luciferase), the major light-emitting enzyme in fireflies and kowtow bugs. Firefly luciferase-IN-2 inhibits P. pyralis luciferase with an IC50 of 3.2 μM, while the inhibitory potency against R. reniformis is not significant.