2-Amino-4-(2-aminophenyl)-4-oxobutanoic acid is a ketone and an amino acid derivative with diverse biological functions, including vasodilatory, immunoregulatory and neuromodulatory activities. 2-Amino-4-(2-aminophenyl)-4-oxobutanoic acid is a precursor for niacin. Aberrant production of 2-Amino-4-(2-aminophenyl)-4-oxobutanoic acid is associated with neurological disease-related cognitive deficits and depressive symptoms. Overexpressed in certain cancer cell types, 2-Amino-4-(2-aminophenyl)-4-oxobutanoic acid could potentially be used as a biomarker to assess cancer risk.