Even with marginal niacin, but adequate Trp, intake,clinical or subclinical pellagra can be induced by drugs interfering withone or more enzymes of the KP, e.g. by TDO inhibition by some antibioticsand antiviral drug or kynureninase inhibition by hydrazine compounds oroestrogens [7, 131]. The gene discussed is TDO2; the disease is Vitamin B3 deficiency.