Structure-activity relationship studies of phenothiazine derivatives as a new class of ferroptosis inhibitors together with the therapeutic effect in an ischemic stroke model

Ferroptosis is a new type of programmed cell death discovered recently and has been demonstrated to be involved in a number of human diseases such as ischemic stroke. Ferroptosis inhibitors are expected to have potential to treat these diseases. Herein, we report the identification of promethazine derivatives as a new type of ferroptosis inhibitors. Structure-activity relationship (SAR) analyses led to the discovery of the most potent compound 2-(1-(4-(4-methylpiperazin-1-yl)phenyl)ethyl)-10H-phenothiazine (51), which showed an EC50 (half maximal effective concentration) value of 0.0005 μM in the erastin-induced HT1080 cell ferroptosis model. In the MCAO (middle cerebral artery occlusion) ischemic stroke model, 51 presented an excellent therapeutic effect. This compound also displayed favorable pharmacokinetic properties, in particular, a good ability to permeate the blood-brain barrier. Overall, 51 could be a promising lead compound for the treatment of ferroptosis related diseases and deserves further investigations.