IFNA1 and chronic myelogenous leukemia, BCR-ABL1 positive: Early evidence for the role of the immune response in TFR was based on observations from many years ago that interferon alpha (IFNα) could improve TKI response due to a toxic effect on the LSCs responsible for CML recurrence [32, 33] and that prior treatment with IFNα was associated with higher rates of TFR [34–37].