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The BCR::ABL1 fusion is the Philadelphia chromosome that defines chronic myeloid leukaemia and some acute lymphoblastic leukaemia. Its transcript level in blood, on the international scale, is how response to tyrosine kinase inhibitors is measured and when treatment can be stopped.
The t(9;22) translocation is confirmed at diagnosis by karyotype, FISH or PCR; thereafter quantitative RT-PCR of BCR::ABL1 mRNA on the International Scale defines response milestones (early molecular response <= 10 percent at 3 months, major molecular response <= 0.1 percent, MR4 <= 0.01 percent, MR4.5 <= 0.0032 percent) under ELN and NCCN. Imatinib, dasatinib, nilotinib, bosutinib, ponatinib and asciminib are labelled for Ph+ CML; the MRDx BCR-ABL Test (MolecularMD) is on the FDA list as the companion for nilotinib's treatment-free remission labelling (K173492, 2017), which requires sustained deep molecular response before stopping.
In plain words · The fusion that defines chronic myeloid leukaemia and a quarter of adult acute lymphoblastic leukaemia; the first cancer driver ever switched off by a pill.
The BCR::ABL1 level in your blood is the number that matters in chronic myeloid leukaemia. Below 10 percent at three months is the first milestone; 0.1 percent or lower is a major molecular response; and years at 0.01 percent or lower can allow a supervised attempt to stop treatment. A rising level is the signal to check for a resistance mutation such as T315I.
Written only from the label or guideline text cited on this page. Not medical advice; your own report and the reading your team gives it come first.
BCR::ABL1 mRNA relative to a control gene, reported as a percentage on the International Scale; major molecular response is 0.1 percent or lower, MR4 0.01 percent or lower, MR4.5 0.0032 percent or lower.
“t(9;21) Philadelphia chromosome: BCR - ABL fusion”
FDA: List of FDA-Authorized Companion Diagnostic Devices| Threshold | Drug | Cancer | Regulator | Source |
|---|---|---|---|---|
| Ph+ CML (BCR::ABL1 present) | Imatinib | Chronic myeloid leukaemia, chronic phase | FDA | label |
| Ph+ CML; treatment-free remission requires sustained deep molecular response by MRDx BCR-ABL Test | Nilotinib | Chronic myeloid leukaemia, chronic phase | FDA | label |
Also defined by European LeukemiaNet 2020 recommendations for treating CML (Hochhaus et al., Leukemia 2020): molecular response milestones.
| Device | Maker | Indication and sample | Drug | PMA / 510(k) |
|---|---|---|---|---|
| MRDx BCR-ABL Test | MolecularMD | Chronic Myeloid Leukemia - Peripheral Blood | Nilotinib | K173492 (12/22/2017) |
Matched on the name and aliases of the readout in the title, setting and summary of each trial; a match is a mention, not proof the readout was an entry criterion.
Shares BCR::ABL1 T315I, Bosutinib, Molecular response (MMR, MR4, treatment-free remission), Philadelphia chromosome (Ph+, BCR::ABL1).
Shares Bosutinib, Molecular response (MMR, MR4, treatment-free remission), Philadelphia chromosome (Ph+, BCR::ABL1), Nilotinib.
Shares Bosutinib, Nilotinib, Asciminib, Chronic myeloid leukaemia, chronic phase.
Shares Ponatinib, Asciminib, Chronic myeloid leukaemia, chronic phase, Chronic myeloid leukaemia, accelerated and blast phase.
Shares Nilotinib, Asciminib, Chronic myeloid leukaemia, chronic phase, Chronic myeloid leukaemia, accelerated and blast phase.
Shares Ponatinib, Asciminib, Dasatinib, Philadelphia chromosome-positive acute lymphoblastic leukaemia in children (Ph-positive ALL).