Cletoquine-d4-1 is the deuterium labeled Cletoquine. Cletoquine (Desethylhydroxychloroquine) is a major active metabolite of Hydroxychloroquine. Cletoquine is produced in the liver by CYP2D6, CYP3A4, CYP3A5, and CYP2C8 isoenzymes. Cletoquine is also a Chloroquine derivative and has the ability to against the chikungunya virus (CHIKV). Cletoquine has antimalarial effects and has the potential for autoimmune diseases treatment[1][2].