Taken together, our results support that determination of PTPRG expression level by flow cytometry as a new biomarker of response to treatment with BCR-ABL1 TKIs is a useful tool for studying its role in tumor progression and predicting the response to therapeutic interventions and clinical management in patients with CML. The gene discussed is PTPRG; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.