{"entity":{"id":"cd19-expression","kind":"biomarker","name":"CD19 expression (CD19-positive)","aka":["CD19-positive","CD19+","CD19 expression","CD19 positive B-ALL","CD19 loss","CD19-negative relapse"],"tldr":"CD19 is the B-cell surface protein that blinatumomab, CAR-T cells and several antibodies aim at. Blinatumomab's label requires CD19-positive leukaemia; the CAR-T labels assume it, and losing CD19 is the commonest way the disease escapes.","summary":"CD19 is read by flow cytometry on blood or marrow blasts, or by immunohistochemistry on lymphoma tissue. Blinatumomab (Blincyto) is labelled for CD19-positive B-cell precursor ALL (in remission with MRD of 0.1 percent or more, in consolidation, and relapsed or refractory); tisagenlecleucel, axicabtagene ciloleucel, lisocabtagene maraleucel and brexucabtagene autoleucel are CD19-directed CAR-T products whose labels describe the disease by histology rather than by a CD19 threshold; tafasitamab and loncastuximab tesirine are CD19-directed antibodies for DLBCL. Antigen loss or lineage switch after CD19-directed therapy is documented in the labels' clinical sections and is the reason CD22- and CD20-directed options exist.","asOf":"2026-09-23","links":[{"label":"BLINCYTO prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=38b482a8-960b-4591-9857-5031ecb830aa"}],"tags":["biomarker","surface-antigen"],"related":["cd22-expression","cd20-expression"],"cancers":["all-leukemia","all-paediatric-relapsed","dlbcl","follicular-lymphoma","mantle-cell-lymphoma"],"sections":[],"technologies":[],"targets":[],"drugs":["blinatumomab","tisagenlecleucel","axicabtagene-ciloleucel","lisocabtagene-maraleucel","brexucabtagene-autoleucel","tafasitamab","zynlonta"],"companies":[],"institutions":[],"pathways":[],"terms":["flow-cytometry","antigen-escape","mrd"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"cd19","measurement":"ihc-score","scoringRule":{"text":"CD19 detected on leukaemia blasts by flow cytometry (the label states CD19-positive without a percentage); for CAR-T and lymphoma antibodies no measurement is required.","quote":"CD19-positive B-cell precursor acute lymphoblastic leukemia (ALL) in first or second complete remission with minimal residual disease (MRD) greater than or equal to 0.1%.","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=38b482a8-960b-4591-9857-5031ecb830aa","sourceLabel":"BLINCYTO prescribing information"},"thresholds":[{"value":"CD19-positive (flow cytometry, no percentage stated)","drugId":"blinatumomab","cancerId":"all-leukemia","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=38b482a8-960b-4591-9857-5031ecb830aa","quote":"BLINCYTO is a bispecific CD19-directed CD3 T-cell engager indicated for the treatment of adult and pediatric patients one month and older with: CD19-positive B-cell precursor acute lymphoblastic leukemia (ALL) in first or second complete remission with minimal residual disease (MRD) greater than or equal to 0.1%.","status":"current"}],"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"Almost every B-cell leukaemia and lymphoma is CD19-positive, so a positive result mainly confirms that blinatumomab, CAR-T cells and the CD19 antibodies are options. If the disease comes back after one of these treatments, CD19 is re-checked, because a CD19-negative relapse needs a treatment aimed at a different target such as CD22."},"route":"/biomarkers/cd19-expression/","neighbours":{"biomarker":[{"id":"cd20-expression","kind":"biomarker","name":"CD20 expression (CD20-positive)","route":"/biomarkers/cd20-expression/"},{"id":"cd22-expression","kind":"biomarker","name":"CD22 expression (CD22-positive)","route":"/biomarkers/cd22-expression/"},{"id":"cd30-expression","kind":"biomarker","name":"CD30 expression (CD30-positive)","route":"/biomarkers/cd30-expression/"}],"cancer":[{"id":"all-leukemia","kind":"cancer","name":"Acute lymphoblastic leukaemia","route":"/cancers/all-leukemia/"},{"id":"dlbcl","kind":"cancer","name":"Diffuse large B-cell lymphoma","route":"/cancers/dlbcl/"},{"id":"follicular-lymphoma","kind":"cancer","name":"Follicular lymphoma","route":"/cancers/follicular-lymphoma/"},{"id":"mantle-cell-lymphoma","kind":"cancer","name":"Mantle cell lymphoma","route":"/cancers/mantle-cell-lymphoma/"},{"id":"all-paediatric-relapsed","kind":"cancer","name":"Relapsed and refractory acute lymphoblastic leukaemia in children","route":"/cancers/all-paediatric-relapsed/"}],"drug":[{"id":"axicabtagene-ciloleucel","kind":"drug","name":"Axicabtagene ciloleucel","route":"/drugs/axicabtagene-ciloleucel/"},{"id":"blinatumomab","kind":"drug","name":"Blinatumomab","route":"/drugs/blinatumomab/"},{"id":"brexucabtagene-autoleucel","kind":"drug","name":"Brexucabtagene autoleucel","route":"/drugs/brexucabtagene-autoleucel/"},{"id":"lisocabtagene-maraleucel","kind":"drug","name":"Lisocabtagene maraleucel","route":"/drugs/lisocabtagene-maraleucel/"},{"id":"zynlonta","kind":"drug","name":"Loncastuximab tesirine","route":"/drugs/zynlonta/"},{"id":"tafasitamab","kind":"drug","name":"Tafasitamab","route":"/drugs/tafasitamab/"},{"id":"tisagenlecleucel","kind":"drug","name":"Tisagenlecleucel","route":"/drugs/tisagenlecleucel/"}],"term":[{"id":"antigen-escape","kind":"term","name":"Antigen escape (antigen loss, lineage switch)","route":"/terms/antigen-escape/"},{"id":"flow-cytometry","kind":"term","name":"Flow cytometry (immunophenotyping)","route":"/terms/flow-cytometry/"},{"id":"mrd","kind":"term","name":"Minimal / molecular residual disease (MRD)","route":"/terms/mrd/"}],"target":[{"id":"cd19","kind":"target","name":"CD19","route":"/targets/cd19/"}]}}