Desethyl chloroquine is a major desethyl metabolite of Chloroquine. Chloroquine diphosphate is an inhibitor of autophagy and toll-like receptors (TLRs). Desethyl chloroquine possesses antiplasmodic activity^[1][2]. In Vitro: P. falciparum^[1] In Vivo: Intraperitoneal injections of Chloroquine are administered to wild-type and Huntington's disease (Q175/Q175) mice. LC-MS/MS is used to compare the levels Chloroquine and its metabolites in blood, brain and muscle tissue. Concentrations of Chloroquine are lower (5-15M), but more stable in brain tissue compared to blood or muscle between 4 and 24 hours after the last dose. Levels of the active Chloroquine metabolite Desethyl chloroquine decreased in muscle and blood over the 24 hour post-injection period, while brain Desethyl chloroquine levels are lower and rose slightly over the same time frame^[3].