KP metabolites
KP metabolites were analysed using plasma samples. The analytical method was adopted from Final concentrations of internal working solution.3-HK: 3-hydroxykynurenine; KynA: kynurenic acid; QUIN: quinolinic acid.For description of plasma extraction and preparation, see The levels of KynA and anthranilic acid were below detectable threshold for, respectively, 81% and 50% of participants at baseline and 43% and 33% of participants at week 4, so we could not include them in the statistical analysis.