In the human urine sample used in method validation, S-(2-succinyl)-l-Cys (S2C) and 5-hydroxy-l-Lys (5-OH-Lys, 2nd GC–MS peak) were found to be the most abundant metabolites followed by CML, CEL and CEA. The gene discussed is CEL; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.