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Protein / target

B-lymphocyte antigen CD19

Encoded byCD19P15391Homo sapiensSwiss-Prot
UniProt: P15391Ensembl: ENSG00000177455HGNC: HGNC:1633NCBI Gene: 930
Clinically validated
Therapeutic maturity
9
Approved medicines
Open Targets target-level
View by indication →
30
Clinical trials
Antibody-tractable
Druggability
Approved Drug

Protein at a glance

Biological role

B cell proliferation involved in immune response

Strongest disease association

Immunodeficiency, common variable, 3

Via encoding gene CD19 · Genetic evidence · score 0.84

Therapeutic position

Established drug target

Antibodies

Derived from structured UniProt, Open Targets and literature data on this page.

Protein profile

UniProt 2026_02

Canonical identity and biological annotation from UniProt.

Function overview

Functions as a coreceptor for the B-cell antigen receptor complex (BCR) on B-lymphocytes.

View complete UniProt function annotation

Functions as a coreceptor for the B-cell antigen receptor complex (BCR) on B-lymphocytes (PubMed:29523808). Decreases the threshold for activation of downstream signaling pathways and for triggering B-cell responses to antigens (PubMed:1373518, PubMed:16672701, PubMed:2463100). Activates signaling pathways that lead to the activation of phosphatidylinositol 3-kinase and the mobilization of intracellular Ca(2+) stores (PubMed:12387743, PubMed:16672701, PubMed:9317126, PubMed:9382888). Is not required for early steps during B cell differentiation in the blood marrow (PubMed:9317126). Required for normal differentiation of B-1 cells (By similarity). Required for normal B cell differentiation and proliferation in response to antigen challenges (PubMed:1373518, PubMed:2463100). Required for normal levels of serum immunoglobulins, and for production of high-affinity antibodies in response to antigen challenge (PubMed:12387743, PubMed:16672701, PubMed:9317126)

Subcellular location

Cell membraneMembrane raft
Domains and Gene Ontology detail (17)

Domains & features

Ig-like C2-type 1Ig-like C2-type 2

Gene Ontology

  • Cexternal side of plasma membrane
  • Cextracellular exosome
  • Cmembrane raft
  • Cplasma membrane
  • Cprotein-containing complex
  • Pantigen receptor-mediated signaling pathway
  • PB cell proliferation
  • PB cell proliferation involved in immune response
  • PB cell receptor signaling pathway
  • PB-1 B cell differentiation
  • Pimmunoglobulin mediated immune response
  • Ppositive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction

556 aa · 61 kDa · 2 isoforms

Biological roles

Reactome v97

What this protein does, drawn together from its UniProt function, Gene Ontology terms and Reactome pathways.

Cell proliferation & survivalReactomeOncogenic signallingReactomeImmune signallingUniProt · GO · Reactome
View supporting evidence

Cell proliferation & survival

  • ·PIP3 activates AKT signaling
  • ·PI5P, PP2A and IER3 Regulate PI3K/AKT Signaling

Oncogenic signalling

  • ·Constitutive Signaling by Aberrant PI3K in Cancer

Immune signalling

  • ·Functions as a coreceptor for the B-cell antigen receptor complex (BCR) on B-lymphocytes…
  • ·antigen receptor-mediated signaling pathway
  • ·B cell proliferation
  • ·B cell proliferation involved in immune response
View underlying pathways (6)
PIP3 activates AKT signaling
Immunoregulatory interactions between a Lymphoid and a non-Lymphoid cell
Constitutive Signaling by Aberrant PI3K in Cancer
PI5P, PP2A and IER3 Regulate PI3K/AKT Signaling
Regulation of Complement cascade
Antigen activates B Cell Receptor (BCR) leading to generation of second messengers

Concepts derived from UniProt GO Reactome — each badge above shows which sources supported that role.

Interaction neighbourhood

STRING v12.0

Proteins with the strongest functional or physical association. Node size and line weight reflect STRING confidence; hover or select a partner to inspect one association.

LYNIFITM1CR2CD81CD79AFCGR3BVAV1FCGR3ACD22CD79BCD19

10 strongest partners — larger node and heavier line mean higher confidence

Functional and physical associations from STRING v12.0. Only associations with this protein are drawn — partner-to-partner links are not part of this evidence.

Approved medicines with mapped indications

7 medicines · 9 areas

Approved therapies targeting this protein, grouped by what they are approved to treat — the disease-first view of the medicines below. Relationships come from the canonical approved-indication graph (ChEMBL phase-4), the same source as the drug cards.

Lymphoma, Large B-Cell, Diffuse4 medicines
axicabtagene ciloleucelloncastuximab tesirinetafasitamabtisagenlecleucel
Precursor B-Cell Lymphoblastic Leukemia-Lymphoma2 medicines
blinatumomabtisagenlecleucel
Lymphoma1 medicine
tafasitamab
Lymphoma, B-Cell1 medicine
loncastuximab tesirine
Lymphoma, Follicular1 medicine
axicabtagene ciloleucel
Lymphoma, Mantle-Cell1 medicine
brexucabtagene autoleucel
Neuromyelitis Optica1 medicine
inebilizumab
Precursor Cell Lymphoblastic Leukemia-Lymphoma1 medicine
blinatumomab
Broader indication categories (1)
Neoplasms3 medicines
blinatumomabloncastuximab tesirinetafasitamab

Broad umbrella indications (e.g. “Neoplasms”). Shown here because every medicine also appears under a more specific disease above — kept for completeness, de-emphasised for clarity.

9 medicines meet Open Targets' target-level approved-medicine definition; the 7 shown here are those on this page with a canonical approved disease indication in the graph. Approved indications from ChEMBL (phase-4), via the canonical drug→disease graph.

Drugs targeting this protein

8

How approved and investigational drugs engage this protein — mechanism and action type, direct vs complex targeting, and how broadly each acts across other targets. A drug-first view (the section above groups the approved ones disease-first); direct binders with few recorded targets are listed first.

axicabtagene ciloleucel
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Lymphoma, Follicular, Lymphoma, Large B-Cell, Diffuse

Direct interaction with this protein · Only this protein recorded as a target

tisagenlecleucel
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Lymphoma, Large B-Cell, Diffuse, Precursor B-Cell Lymphoblastic Leukemia-Lymphoma

Direct interaction with this protein · Only this protein recorded as a target

inebilizumab
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Neuromyelitis Optica

Direct interaction with this protein · Only this protein recorded as a target

lisocabtagene maraleucel
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Direct interaction with this protein · Only this protein recorded as a target

loncastuximab tesirine
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Lymphoma, B-Cell, Lymphoma, Large B-Cell, Diffuse, Neoplasms

Direct interaction with this protein · Only this protein recorded as a target

tafasitamab
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Lymphoma, Lymphoma, Large B-Cell, Diffuse, Neoplasms

Direct interaction with this protein · Only this protein recorded as a target

View all 8 targeting drugs
brexucabtagene autoleucel
Narrow target profileApprovedBinding agent

B-lymphocyte antigen CD19 binding agent

Indicated for Lymphoma, Mantle-Cell

Direct interaction with this protein · Only this protein recorded as a target

blinatumomab
ApprovedCross-linking agent

B-lymphocyte antigen CD19 cross-linking agent

Indicated for Precursor B-Cell Lymphoblastic Leukemia-Lymphoma, Precursor Cell Lymphoblastic Leukemia-Lymphoma, Neoplasms

Direct interaction with this protein · 1 of 4 recorded protein targets

ChEMBL mechanism, action type, target identity and approved indications. Open Targets clinical status.

Translational evidence

Open Targets 26

Why this target matters therapeutically, strongest evidence first. Disease associations are gene-level (via the gene that encodes this protein) and open into the full confidence synthesis; the development universe, tractability and safety annotations are target-level, from Open Targets.

Strongest disease associations · via encoding gene CD19

Gene-level evidence surfaced through the gene CD19that encodes this protein — not a direct protein–disease relationship. Ranked by Forefront's causal-directness weighting, so genetically- and clinically-evidenced diseases lead over ones that merely share the literature.

Immunodeficiency, common variable, 3
0.88Well supported

Genetic evidence dominant · Open Targets 0.67

Lymphoma, Large B-Cell, Diffuse
0.76Well supported

Clinical evidence dominant · Open Targets 0.62

Precursor Cell Lymphoblastic Leukemia-Lymphoma
0.73Moderately supported

Clinical evidence dominant · Open Targets 0.59

Neuromyelitis Optica
0.72Moderately supported

Clinical evidence dominant · Open Targets 0.58

Common variable immunodeficiency
0.72Moderately supported

Genetic literature evidence dominant · Open Targets 0.60

View evidence synthesis (5)
Immunodeficiency, common variable, 3Well supported
0.88
agreement 0.76–1.00
Genetic77%Animal model23%Literature0%Genetic literaturedup

Open Targets aggregate 0.67 · 3 independent evidence families · 1 not counted as duplicate

Lymphoma, Large B-Cell, DiffuseWell supported
0.76
agreement 0.61–0.92
Clinical85%Literature15%

Open Targets aggregate 0.62 · 2 independent evidence families

Precursor Cell Lymphoblastic Leukemia-LymphomaModerately supported
0.73
agreement 0.58–0.89
Clinical82%Literature18%

Open Targets aggregate 0.59 · 2 independent evidence families

Neuromyelitis OpticaModerately supported
0.72
agreement 0.56–0.88
Clinical88%Literature12%

Open Targets aggregate 0.58 · 2 independent evidence families

Common variable immunodeficiencyModerately supported
0.72
agreement 0.59–0.84
Genetic literature61%Animal model26%Literature12%

Open Targets aggregate 0.60 · 3 independent evidence families

The evidence agreement range shows how closely the independent evidence families agree — it is not a statistical confidence interval, and nothing here is fitted to outcome data. Derived from Open Targets evidence types under Forefront weighting; the per-type scores above show the calculation.

Show all associations
Immunodeficiency, common variable, 30.67
Lymphoma, Large B-Cell, Diffuse0.62
Common variable immunodeficiency0.60
Precursor Cell Lymphoblastic Leukemia-Lymphoma0.59
Neuromyelitis Optica0.58
Lymphoma, Mantle-Cell0.55
Lymphoma, Follicular0.54
Neoplasms0.53
B-cell acute lymphoblastic leukemia0.52
Agammaglobulinemia0.47

Drug development

14 compounds recorded · 9 approved · 5 in clinical development

Open Targets' development universe — every compound recorded against the target at any stage, not all approved medicines. Distinct from the 8 drugs that target this protein in Forefront's canonical graph (7 with a mapped approved indication, shown above): these count different sets and are not a subset relation.

View all recorded compounds (10)
TISAGENLECLEUCELApproval
INEBILIZUMABApproval
OBECABTAGENE AUTOLEUCELApproval
MDX-1342Phase 2
AXICABTAGENE CILOLEUCELApproval
BLINATUMOMABApproval
OBEXELIMABPhase 3
TAFASITAMABApproval
BREXUCABTAGENE AUTOLEUCELApproval
ONCOLYSIN BPhase 2

Open Targets known-drugs universe. Drug name and highest clinical stage only — the disease relationship is NOT read from this slice (it carries trial-context noise); approved indications come from the canonical graph above.

Tractability

Antibodies — Strong

Approved Drug and UniProt loc high conf support this modality.

Protein degraders — Emerging

Feasibility evidence (half-life data) — no clinical-stage drug of this modality recorded.

Other modalities — Strong

Approved Drug support this modality.

View underlying tractability evidence (6)
AB · Approved DrugAB · UniProt loc high confAB · GO CC high confAB · UniProt SigP or TMHMMPR · Half-life DataOC · Approved Drug

Raw Open Targets tractability assessment buckets, by modality.

Clinical trials

30

Trials of drugs that target this protein — reached indirectly through those drugs, so a trial listed here studies the drug, not the protein. Ranked by active status, then clinical phase and recency, and spread across the targeting drugs.

Efficacy and Safety of Low-Dose Blinatumomab in the Treatment of Refractory Autoimmune Encephalitis and Autoimmune CerebellitisPHASE4

NOT_YET_RECRUITING · via blinatumomab · NCT07686042

Prospective Clinical Study of Axicabtagene Ciloleucel for Consolidation After First-line Treatment of High-risk Large B-cell LymphomaPHASE4

RECRUITING · via axicabtagene ciloleucel · NCT06609304

A Long-term, Open-label, Low-interventional Safety Study of Inebilizumab in the Treatment of NMOSD (N-MOmentum LT)PHASE4

ACTIVE_NOT_RECRUITING · via inebilizumab · NCT06180278

A Randomized, Multi-center, Phase 3 Study of Tafasitamab and Lenalidomide in Combination With Gemcitabine and Oxaliplatin Versus Rituximab in Combination With Gemcitabine and Oxaliplatin in Patients With Relapsed/Refractory Diffuse Large B-Cell LymphomaPHASE3

RECRUITING · via tafasitamab · NCT06521255

View all trials (26)
Blinatumomab Sequential Donor Lymphocyte Infusion in Acute B Lymphocytic Leukemia Observation of Therapeutic Effect in Patients With Recurrence After Allogeneic Hematopoietic Stem Cell TransplantationPHASE4

RECRUITING · via blinatumomab · NCT06339775

A Phase 2/3, Randomized, Double-blind, Multicenter, Placebo-controlled Study of Inebilizumab in Participants With Autoimmune HepatitisPHASE3

NOT_YET_RECRUITING · via inebilizumab · NCT07598825

A Phase 3, Randomized, Open-Label, Multicenter Study Evaluating the Efficacy of KITE-753 Versus Axicabtagene Ciloleucel in Participants With Relapsed or Refractory Large B-Cell Lymphoma After First-Line TherapyPHASE3

RECRUITING · via axicabtagene ciloleucel · NCT07479797

A Phase 2/3, Randomized, Open-Label, Comparison Study of MK-1045 Versus Blinatumomab in Participants With Relapsed or Refractory CD19+ B-Cell Acute Lymphoblastic Leukemia (B-ALL)PHASE2/PHASE3

RECRUITING · via blinatumomab · NCT07570173

International Study for Treatment of Childhood Relapsed Precursor B-Cell ALL 2020 A Randomized Phase III Study Conducted by the Resistant Disease Committee of the International BFM Study GroupPHASE3

NOT_YET_RECRUITING · via blinatumomab · NCT07476729

Framework for Optimizing, Refining, and Unifying Management of HSCT in Pediatric ALLPHASE2/PHASE3

NOT_YET_RECRUITING · via blinatumomab · NCT07297914

A Phase 3 Randomized Controlled Trial of Rondecabtagene Autoleucel , an Autologous, Dual-targeting CD19/CD20 CAR T-Cell Product Candidate, Vs. Investigator's Choice of CD19 CAR T-Cell Therapy in Patients With Relapsed or Refractory Large B-Cell Lymphoma in the Second-line SettingPHASE3

RECRUITING · via axicabtagene ciloleucel · NCT07188558

Efficacy and Safety of Blinatumomab for Treatment of Refractory Myasthenia Gravis.PHASE2/PHASE3

NOT_YET_RECRUITING · via blinatumomab · NCT06836973

Chinese Children's Cancer Group-2025 Protocol for Newly Diagnosed Low Risk Childhood B-cell Acute Lymphoblastic LeukemiaPHASE2/PHASE3

RECRUITING · via blinatumomab · NCT06882057

Chinese Children's Cancer Group-2025 Protocol for Newly Diagnosed for Intermediate/High Risk Childhood B-cell ALLPHASE2/PHASE3

RECRUITING · via blinatumomab · NCT06764238

Safety and Efficacy of Blinatumomab in Refractory Myasthenia GravisPHASE2/PHASE3

NOT_YET_RECRUITING · via blinatumomab · NCT06684184

Efficacy Study of Blinatumomab Clean Up Early Residual Disease for Newly Diagnosed Pediatric B Lymphoblastic LeukemiaPHASE2/PHASE3

RECRUITING · via blinatumomab · NCT06607419

A Global Study of Novel Agents in Paediatric and Adolescent Relapsed and Refractory B-cell Non-Hodgkin LymphomaPHASE2/PHASE3

RECRUITING · via loncastuximab tesirine · NCT05991388

A Randomized, Open-label, Multi-center Phase III Trial Comparing Tisagenlecleucel to Standard of Care in Adult Participants With Relapsed or Refractory Follicular Lymphoma (FL)PHASE3

ACTIVE_NOT_RECRUITING · via tisagenlecleucel · NCT05888493

An Adaptive Phase 3, Randomized, Open-Label, Multicenter Study to Compare the Efficacy and Safety of Axicabtagene Ciloleucel Versus Standard of Care Therapy as First-Line Therapy in Subjects With High-Risk Large B-Cell Lymphoma (ZUMA-23)PHASE3

ACTIVE_NOT_RECRUITING · via axicabtagene ciloleucel · NCT05605899

Interfant-21 International Collaborative Treatment Protocol for Infants Under One Year With KMT2A-rearranged Acute Lymphoblastic Leukemia or Mixed Phenotype Acute Leukemia.PHASE3

RECRUITING · via blinatumomab · NCT05327894

Phase 3 Study of MT-0551 in Patients With Systemic Sclerosis (Placebo-Controlled Double-Blind Study)PHASE3

ACTIVE_NOT_RECRUITING · via inebilizumab · NCT05198557

A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study to Evaluate the Efficacy and Safety of Tafasitamab Plus Lenalidomide in Addition to Rituximab Versus Lenalidomide in Addition to Rituximab in Patients With Relapsed/Refractory (R/R) Follicular Lymphoma Grade 1 to 3a or R/R Marginal Zone LymphomaPHASE3

ACTIVE_NOT_RECRUITING · via tafasitamab · NCT04680052

A Randomized, Double-blind, Multicenter, Placebo-controlled Phase 3 Study With Open-label Period to Evaluate the Efficacy and Safety of Inebilizumab in Adults With Myasthenia GravisPHASE3

ACTIVE_NOT_RECRUITING · via inebilizumab · NCT04524273

A Phase 3 Randomized Study of Loncastuximab Tesirine Combined With Rituximab Versus Immunochemotherapy in Patients With Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL) (LOTIS-5)PHASE3

ACTIVE_NOT_RECRUITING · via loncastuximab tesirine · NCT04384484

A Phase 3 Trial Investigating Blinatumomab (NSC# 765986) in Combination With Chemotherapy in Patients With Newly Diagnosed Standard Risk or Down Syndrome B-Lymphoblastic Leukemia (B-ALL) and the Treatment of Patients With Localized B-Lymphoblastic Lymphoma (B-LLy)PHASE3

ACTIVE_NOT_RECRUITING · via blinatumomab · NCT03914625

International Collaborative Treatment Protocol for Children and Adolescents With Acute Lymphoblastic Leukemia - AIEOP-BFM ALL 2017PHASE3

RECRUITING · via blinatumomab · NCT03643276

Phase Ib/II of the Combination of Fludarabine, Cytarabine, Idarubicin, G-CSF (FLAG-Ida) With Venetoclax and Asciminib in Patients With Advanced Phase Chronic Myeloid Leukemia and Philadelphia Chromosome-Positive Acute Myeloid LeukemiaPHASE1/PHASE2

NOT_YET_RECRUITING · via blinatumomab · NCT07604233

A Phase II Randomized Study of Blinatumomab With or Without Revumenib for Patients With KMT2A-Translocation B-Cell Acute Lymphoblastic Leukemia (ALL)/ Acute Leukemia With Ambiguous Lineage (ALAL) With Persistent Measurable Residual Disease (MRD)PHASE2

NOT_YET_RECRUITING · via blinatumomab · NCT07636564

Phase 2 Study to Assess the Safety and Efficacy of Subcutaneous Blinatumomab in Patients With Measurable Residual Disease Positive B-cell Acute Lymphoblastic LeukemiaPHASE2

NOT_YET_RECRUITING · via blinatumomab · NCT07192237

A Phase 2 Open-label Multicenter Study to Evaluate the Pharmacokinetics, Pharmacodynamics, Safety and Tolerability of Inebilizumab in Children From 2 Years to Less Than 18 Years of Age With Generalized Myasthenia Gravis (gMG)PHASE2

RECRUITING · via inebilizumab · NCT06987539

ClinicalTrials.gov via the drug-target graph.

What's happening now

12

Recent therapeutic activity around this target — regulatory actions, clinical trials and safety signals for 7 drugs that target this protein, plus publications where such a drug is a genuine subject. Every item is reached indirectly through the drug, not the protein itself; incidental mentions (a paper that merely measures a drug) and press items are excluded.

  1. Trial status changed2026-07-20

    A Phase II Trial of Tafasitamab and Lenalidomide Followed by Tafasitamab and ICE as Salvage Therapy for Transplant Eligible Patients With Relapsed/ Refractory Large B-Cell Lymphoma

    Status changed to Active, not recruiting · ClinicalTrials.gov · via tafasitamab

  2. Trial status changed2026-07-17

    A Phase 1b Open-Label Study to Evaluate the Safety and Anti-cancer Activity of Loncastuximab Tesirine in Combination With Other Anti-cancer Agents in Patients With Relapsed or Refractory B-cell Non-Hodgkin Lymphoma (LOTIS-7)

    Status changed to Active, not recruiting · ClinicalTrials.gov · via loncastuximab tesirine

  3. New publication2024-07-08
    A systematic review and meta-analysis of nonrelapse mortality after CAR T cell therapy.

    Nature medicine · 2024 · 190 citations · Europe PMC · via axicabtagene ciloleucel

  4. Regulatory approval2022-12-20

    Approval: Zynlonta (EMA)

    ema · regulatory · ema · via loncastuximab tesirine

  5. Regulatory approval2022-04-25

    Approval: Uplizna (EMA)

    ema · regulatory · ema · via inebilizumab

  6. Regulatory approval2022-04-04

    Approval: Breyanzi (EMA)

    ema · regulatory · ema · via lisocabtagene maraleucel

  7. New publication2021-12-11
    Axicabtagene Ciloleucel as Second-Line Therapy for Large B-Cell Lymphoma.

    The New England journal of medicine · 2022 · 1,202 citations · Europe PMC · via axicabtagene ciloleucel

  8. Regulatory approval2021-08-26

    Approval: Minjuvi (EMA)

    ema · regulatory · ema · via tafasitamab

  9. New publication2018-12-01
    Tisagenlecleucel in Adult Relapsed or Refractory Diffuse Large B-Cell Lymphoma.

    The New England journal of medicine · 2019 · 3,115 citations · Europe PMC · via tisagenlecleucel

  10. Regulatory approval2018-08-23

    Approval: Kymriah (EMA)

    ema · regulatory · ema · via tisagenlecleucel

  11. New publication2018-02-01
    Tisagenlecleucel in Children and Young Adults with B-Cell Lymphoblastic Leukemia.

    The New England journal of medicine · 2018 · 4,269 citations · Europe PMC · via tisagenlecleucel

  12. Regulatory approval2015-11-23

    Approval: Blincyto (EMA)

    ema · regulatory · ema · via blinatumomab

Objective event titles are shown unmodified; the event kind and significance line are derived from structured fields. Forefront AttentionEvent stream aggregating Europe PMC Regulatory filings ClinicalTrials.gov.