CD20

CD20 is a B-cell marker; rituximab against it was the first antibody approved for cancer, in 1997.

CD20 (MS4A1) is a B-cell tetraspanin that regulates calcium flux; it is not internalised, which favours effector-based antibodies and T-cell engagers over ADCs, and it is present on over 95% of DLBCL and, more dimly, over 90% of CLL. It is the target of rituximab, the first antibody approved for cancer in 1997, and of obinutuzumab. The CD20×CD3 bispecifics glofitamab, epcoritamab, mosunetuzumab, and odronextamab now offer off-the-shelf T-cell redirection in lymphoma without the manufacturing wait of CAR-T. Loss of CD20 expression is a recognised escape route after repeated anti-CD20 therapy, and the best sequencing of bispecifics versus CAR-T is still being worked out. The simple version is the B-cell marker that started antibody therapy for cancer and now anchors the newest T-cell engagers.

CD20: what it is and how drugs act on it · animated schematic, not to scale

Target · the protein and the cell it sits on
Drug · antibody, small molecule, cell or radioligand
Effect · signal, damage or kill

In plain words · CD20 is a B-cell marker; rituximab against it was the first antibody approved for cancer, in 1997.

1 · What it is
CD20 is a B-cell marker; rituximab against it was the first antibody approved for cancer, in 1997.
2 · What goes wrong in cancer
CD20 is a tetraspanin regulating B-cell calcium flux; it is not internalised, favouring effector-based antibodies over ADCs.
3 · How drugs use it
3 products aim at CD20: antibodies and radioligands. Because it sits on the outside of the cell, it can be reached from the bloodstream: antibodies flag the cell, ADCs deliver a toxin, radioligands deliver radiation, and CAR-T or bispecifics bring a T cell.

External identifiers

MS4A1HGNCEnsemblUniProtAlphaFold DBChEMBLOpen TargetsCIViCOncoKBCOSMICcBioPortalDepMapHuman Protein AtlasNCBI GeneOMIM

Biology

CD20 is a tetraspanin regulating B-cell calcium flux; it is not internalised, favouring effector-based antibodies over ADCs.

Where it is found

DLBCL
Follicular lymphoma
CLL
Mantle cell lymphoma

Class

surface antigen · MS4A1

Identifiers

HGNC HGNC:7315Ensembl ENSG00000156738UniProt P11836NCBI Gene 931

How often this target appears

Cancer	Prevalence	Measure	Note	Source
Diffuse large B-cell lymphoma	>95%	Surface expression		Wikipedia

Approximate, population-level figures; the measure column says what was counted. Ranges show the midpoint as a bar.

Products

3top

ApprovedRadioimmunotherapy (yttrium-90 labelled anti-CD20 antibody)

Ibritumomab tiuxetan · Zevalin

Zevalin is an antibody carrying a radioactive isotope that seeks out CD20 on lymphoma cells. It treats follicular lymphoma that has relapsed and is given as a one-off consolidation after chemotherapy.

Withdrawnradioimmunotherapy

Iodine-131 tositumomab · Bexxar

A cancer-targeting antibody carrying a radioactive form of iodine was used, as a single course, to treat a type of blood cancer called non-Hodgkin lymphoma. The manufacturer stopped selling it in 2014 because too few patients were using it.

ApprovedMonoclonal antibody (anti-CD20, chimeric)

Rituximab · Rituxan / MabThera (and biosimilars)

Rituximab was the first antibody ever approved for cancer (1997). It made chemoimmunotherapy the CLL standard for a decade, and biosimilars keep it cheap and everywhere.