SLC22A1 and chronic myelogenous leukemia, BCR-ABL1 positive: Functional OCT1 activity has been implicated as a determinant of response in CML: polymorphisms like SLC22A1 rs628031 (Met408Val, linked to a splicing defect) are associated with reduced OCT1 function and have been correlated with lower rates of molecular response to imatinib [20].