In the CNS, the kynurenine pathway is confined to microglial cells.97 QA levels are increased and KA levels decreased in post-mortem HD patient brain.98,99 A yeast genomic screen highlighted KMO as a leading therapeutic target,100 and subsequent work in drosophila has confirmed this.101 Zwilling and colleagues102 treated R6/2 HD model mice with a KMO inhibitor compound, JM6, and found increased brain levels of KA and decreased glutamate. Here, KMO is linked to Huntington disease.