This publication includes the work of several individuals who at some stage of the study provided either their technical assistance in conducting experiments or operational assistance in managing the studies. The authors particularly acknowledge B Begley, D Delinsky, R Demers, S Daupree, V Kempf, B Nofsinger, W Ward, D Wentzel, P Wheelan, D Stephens, D Humphries, A Underberg, D Sullivan and A Febock for their contributions. The authors also thank R Pacifici (Chief Scientific Officer, CHDI) for his constant support for this kynurenine pathway methods validation study.