MAO-B-IN-45 is a dual inhibitor of ferroptosis and MAO-B. It selectively inhibits MAO-B with an IC50 of 87.47 nM, demonstrating a selectivity over MAO-A by more than 229 times. In vitro, MAO-B-IN-45 exhibits significant anti-ferroptosis activity by modulating iron metabolism pathways and the GSH-GPX4 axis. Additionally, it improves cognitive and behavioral deficits in 3×Tg (APP/Tau/Ps1) Alzheimer's disease mice and significantly reduces levels of ferritin heavy chain 1 (FTH1), β-amyloid protein (APP), and Tau protein phosphorylation (p-Tau) in their brains.

MAO-B-IN-45 (compound 21d) is a reversible hMAO-B inhibitor with a Ki of 100.6 nM, demonstrating significant inhibitory activity with inhibition rates of 94.81% at 10 μM and 76.31% at 1 μM. The compound exhibits good safety in PC12 and HT22 cells at concentrations ranging from 0.1 to 75 μM over 24 hours. Additionally, MAO-B-IN-45 effectively reduces ferroptosis induced by RSL or Erastin in HT22 cells in a dose-dependent manner at concentrations of 1-50 μM for 24 hours. In HT22 cells, it also decreases reactive oxygen species (ROS) production at 10-50 μM for 24 hours. Furthermore, MAO-B-IN-45, at 15-100 μM over 24 hours, effectively inhibits ferroptosis by reducing iron accumulation and enhancing glutathione (GSH)-dependent pathways in HT22 cells.

MAO-B-IN-45 (Compound 21d) administered at a dosage of 10 mg/kg intraperitoneally, daily for 35 days, alleviates memory and cognitive impairments in a 3×Tg (APP/Tau/Ps1) mouse model of Alzheimer's disease and demonstrates good safety in vivo.