{"entity":{"id":"bcr-abl1-transcript","kind":"biomarker","name":"BCR::ABL1 transcript (Philadelphia chromosome, quantitative PCR)","aka":["BCR-ABL1","BCR::ABL1","BCR-ABL","Philadelphia chromosome positive","Ph+","Ph-positive","BCR-ABL1 IS","BCR-ABL1 international scale","MMR","MR4","MR4.5","major molecular response"],"tldr":"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.","summary":"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.","asOf":"2026-09-23","links":[{"label":"Gleevec prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=211ef2da-2868-4a77-8055-1cb2cd78e24b"},{"label":"FDA: List of FDA-Authorized Companion Diagnostic Devices","url":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"}],"tags":["biomarker","cml"],"related":["bcr-abl1-t315i"],"cancers":["cml","cml-chronic-phase","cml-advanced-phase","all-leukemia","all-paediatric-ph-positive"],"sections":[],"technologies":[],"targets":[],"drugs":["imatinib","dasatinib","nilotinib","bosutinib","ponatinib","asciminib"],"companies":[],"institutions":[],"pathways":[],"terms":["philadelphia-chromosome","molecular-response","mrd"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"bcr-abl","measurement":"sequencing-variant","scoringRule":{"text":"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.","quote":"t(9;21) Philadelphia chromosome: BCR - ABL fusion","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools","sourceLabel":"FDA: List of FDA-Authorized Companion Diagnostic Devices"},"thresholds":[{"value":"Ph+ CML (BCR::ABL1 present)","drugId":"imatinib","cancerId":"cml-chronic-phase","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=211ef2da-2868-4a77-8055-1cb2cd78e24b","quote":"Newly diagnosed adult and pediatric patients with Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in chronic phase.","status":"current"},{"value":"Ph+ CML; treatment-free remission requires sustained deep molecular response by MRDx BCR-ABL Test","drugId":"nilotinib","cancerId":"cml-chronic-phase","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6093952a-5248-45cb-ad17-33716a411146","quote":"Adult and pediatric patients greater than or equal to 1 year of age with newly diagnosed Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in chronic phase.","status":"current"}],"definedBy":{"label":"European LeukemiaNet 2020 recommendations for treating CML (Hochhaus et al., Leukemia 2020): molecular response milestones","url":"https://doi.org/10.1038/s41375-020-0776-2"},"tests":["foundationone-heme","neotype-profiles"],"assays":[],"companionDiagnostics":[{"device":"MRDx BCR-ABL Test","maker":"MolecularMD","drugs":["nilotinib"],"indication":"Chronic Myeloid Leukemia - Peripheral Blood","pma":"K173492 (12/22/2017)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"}],"forPatient":"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."},"route":"/biomarkers/bcr-abl1-transcript/","neighbours":{"biomarker":[{"id":"bcr-abl1-t315i","kind":"biomarker","name":"BCR::ABL1 T315I","route":"/biomarkers/bcr-abl1-t315i/"}],"cancer":[{"id":"all-leukemia","kind":"cancer","name":"Acute lymphoblastic leukaemia","route":"/cancers/all-leukemia/"},{"id":"cml","kind":"cancer","name":"Chronic myeloid leukaemia (CML)","route":"/cancers/cml/"},{"id":"cml-advanced-phase","kind":"cancer","name":"Chronic myeloid leukaemia, accelerated and blast phase","route":"/cancers/cml-advanced-phase/"},{"id":"cml-chronic-phase","kind":"cancer","name":"Chronic myeloid leukaemia, chronic phase","route":"/cancers/cml-chronic-phase/"},{"id":"all-paediatric-ph-positive","kind":"cancer","name":"Philadelphia chromosome-positive acute lymphoblastic leukaemia in children (Ph-positive ALL)","route":"/cancers/all-paediatric-ph-positive/"}],"drug":[{"id":"asciminib","kind":"drug","name":"Asciminib","route":"/drugs/asciminib/"},{"id":"bosutinib","kind":"drug","name":"Bosutinib","route":"/drugs/bosutinib/"},{"id":"dasatinib","kind":"drug","name":"Dasatinib","route":"/drugs/dasatinib/"},{"id":"imatinib","kind":"drug","name":"Imatinib","route":"/drugs/imatinib/"},{"id":"nilotinib","kind":"drug","name":"Nilotinib","route":"/drugs/nilotinib/"},{"id":"ponatinib","kind":"drug","name":"Ponatinib","route":"/drugs/ponatinib/"}],"term":[{"id":"mrd","kind":"term","name":"Minimal / molecular residual disease (MRD)","route":"/terms/mrd/"},{"id":"molecular-response","kind":"term","name":"Molecular response (MMR, MR4, treatment-free remission)","route":"/terms/molecular-response/"},{"id":"philadelphia-chromosome","kind":"term","name":"Philadelphia chromosome (Ph+, BCR::ABL1)","route":"/terms/philadelphia-chromosome/"}],"target":[{"id":"bcr-abl","kind":"target","name":"BCR::ABL1 (Philadelphia chromosome)","route":"/targets/bcr-abl/"}]}}