Further validation of predicted targets using a panel of 105 circulating plasma metabolites in PAH patients confirmed the association of right ventricular‐pulmonary vascular dysfunction with circulating indoleamine 2,3‐dioxygenase (IDO)‐dependent tryptophan metabolites (TMs), tricarboxylic acid intermediates and purine metabolites.7 Reports from recent study are also congruent with these findings where they demonstrate a strong strength of association between patient survival and metabolic profiles in PAH.8 Here, IDO1 is linked to pulmonary arterial hypertension.