Identification and synthesis of substituted pyrrolo[2,3-d]pyrimidines as novel firefly luciferase inhibitors

A novel firefly luciferase inhibitor (3a) with a pyrrolo[2,3-d]pyrimidine core was identified in a cell-based NF-κB luciferase reporter gene assay. It potently inhibited the firefly luciferase derived from Photinus pyralis with an IC50 value of 0.36 ± 0.05 μM. Kinetic analysis of 3a inhibition showed that it is predominantly competitive with respect to d-luciferin and uncompetitive with respect to ATP. Therefore, several pyrrolo[2,3-d]pyrimidine analogues were prepared to further investigate the structure-activity relationship (SAR) for luciferase inhibition. The most potent inhibitor of this series was 4c, which showed an IC50 value of 0.06 ± 0.01 μM. In addition, molecular docking studies suggested that both 3a and 4c could be accommodated in the d-luciferin binding pocket, which is expected for a predominantly competitive inhibitor with respect to d-luciferin.