BCR and leukemia: Just as in the clinical data (symbols), the response to TKI therapy produces a biphasic exponential decrease in BCR-ABL1 transcripts, which decreases below 10–1, representing a so-called major molecular response (MMR or MR3), which represents a major goal of therapy in CML as the risk of relapse and leukemia-related death is virtually nonexistent once this milestone is achieved (Hochhaus et al., 2017).