Ebselen (also called PZ 51, DR3305, and SPI-1005), is a synthetic organoselenium molecule under preliminary investigation as a drug candidate.

[1] It is being developed by the Seattle biotechnology company, Sound Pharmaceuticals, Inc.[1] Ebselen has been entered into clinical trials as a lead compound intended for the potential treatment of various diseases.

[2] Its most advanced clinical trial is a Phase III study in people with Meniere's disease, completed in July 2024.

[1][4] Generally, synthesis of the characteristic scaffold of ebselen, the benzoisoselenazolone ring system, can be achieved either through reaction of primary amines (RNH2) with 2-(chloroseleno)benzoyl chloride (Route I),[5] by ortho-lithiation of benzanilides followed by oxidative cyclization (Route II) mediated by cupric bromide (CuBr2),[6] or through the efficient Cu-catalyzed selenation / heterocyclization of o-halobenzamides, a methodology developed by Kumar et al.[7] (Route III).

[8] Ebselen is in preliminary clinical development for the potential treatment of hearing loss and depression, among other medical indications.