BCR::ABL1 transcript (Philadelphia chromosome, quantitative PCR)
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.
Overview
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.
- Target · the protein and the cell it sits on
- Drug · antibody, small molecule, cell or radioligand
- Effect · signal, damage or kill
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.
- NCT05456191 · 2026A Study to Investigate Tolerability and Efficacy of Asciminib (Oral) Versus Nilotinib (Oral) in Adult Participants (≥18 Years of Age) With Newly Diagnosed Philadelphia Chromosome Positive Chronic Myelogenous Leukemia in Chronic Phase (Ph+ CML-CP)
- NCT04971226 · 2025A Study of Oral Asciminib Versus Other TKIs in Adult Patients With Newly Diagnosed Ph+ CML-CP
- NCT03589326 · 2024PhALLCON
- NCT02744768 · 2020D-ALBA (GIMEMA LAL2116)
- NCT00481247 · 2010DASISION
- NCT03459534A Phase 3 Study for the Efficacy and Safety of Radotinib in CP-CML Patients With Failure or Intolerance to Previous TKIs
- NCT01503502A Phase II Study of Flumatinib Versus Imatinib to Treat Philadelphia Chromosome Positive Chronic Myelogenous Leukemia
- NCT06051409A Study of Olverembatinib in Patients With Newly Diagnosed Ph+ ALL (POLARIS-1)
- NCT02883049Combination Chemotherapy in Treating Young Patients With Newly Diagnosed High-Risk B Acute Lymphoblastic Leukemia and Ph-Like TKI Sensitive Mutations
- NCT03722420Randomized Evaluation of Radotinib Versus Imatinib in Phase III Study for Efficacy With Chinese Patients (RERISE China)
- NCT07387926Safety and Efficacy of Asciminib in Pediatrics and Young Adults With Relapse/Refractory (r/r) Philadelphia Positive (Ph+) or ABL-class Ph-like Acute Lymphoblastic Leukemia (ALL)
- NCT05433532Study of Azacitidine，Venetoclax，and Flumatinib in Newly Diagnosed Ph-positive Acute Leukemia and CML-AP/BP Patients
- NCT04375683Study of Efficacy and Safety of Flumatinib Combined With Chemotherapy in Ph Positive ALL
- NCT04925479Study to Determine the Dose and Safety of Asciminib in Pediatric Patients With Chronic Myeloid Leukemia
- NCT07354074Study to Determine the Efficacy and Safety of Asciminib in Pediatric Patients With Ph+ CML-CP
- NCT04233346The Study for CML Who Failed Prior TKIs or With T315I Mutation or Ph+ ALL Who Failed Prior TKIs or With T315I Mutation
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