Improved Synthesis of Effective 3-(Indolin-6-yl)-4-(N-pyrazole-sulfonamide)-1H-pyrrolo[2,3-b]pyridine-Based Inhibitors of NADPH Oxidase 2

NADPH oxidase enzymes (NOXs) are a family of enzymes generating superoxide, which form reactive oxygen species. NOX2 activity is a causative agent for the progression of many diseases: neurodegenerative, cardiovascular, immune dysregulations, and even hereditary diseases and cancer. Administering antioxidants helps in inhibiting NOX2 activity; however, the development of selective inhibitors may provide greater improvement in the therapy of diseases. Here, an optimized synthesis of two most promising NOX2 inhibitors based on the 3-(indolin-6-yl)-4-(<i>N</i>-pyrazole-sulfonamide)-1<i>H</i>-pyrrolo [2,3-<i>b</i>]pyridine structure, namely, GSK2795039 and NCATS-SM7270, and an isomeric derivative of the same class, IMBIOC-1, is reported. The new modified procedures simplify the isolation, reduce byproduct formation, and improve the yields in 0.1-1 g scale preparations. Molecular modeling of the structures of NOX2 complexes with inhibitors validated their binding at the same site as NADPH, with IMBIOC-1 forming the largest number of intermolecular interactions with the NOX2 active site. Testing the effects of the compounds on amyloid beta-induced oxidative stress and toxicity in HMC3 microglial cells showed that all three inhibitors completely prevented the pathological amyloid-beta effect. At the same time, NCATS-SM7270 and IMBIOC-1 provided a stronger protective effect on microglial cell survival than GSK2795039, which allowed us to assert the potential of those compounds as neuroprotective agents.