Importantly, LPS-challenged mice also exhibit depressive- and anxiety-like behaviors concomitant with the elevations in neurotoxic metabolites.20 Whereas evidence implicates KMO-dependent kynurenine metabolism as a likely pathogenic mechanism underlying inflammation-induced depression,28 until recently, no preclinical genetic models were available to directly test this hypothesis and brain-penetrant KMO inhibitors are not commercially available. The gene discussed is KMO; the disease is major depressive disorder.