surface-antigen

B7-H3 is an immune checkpoint protein overexpressed on small-cell lung, prostate and many solid tumours. Ifinatamab deruxtecan is in phase 3 for small-cell lung cancer without an expression cut-off; nothing is approved.

BCMA is the plasma-cell antigen behind the myeloma bispecifics and CAR-T cells. None of their labels requires a BCMA test; expression is near-universal, and loss through BCMA gene deletion is a documented escape route.

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.

CD20 is the B-cell antigen rituximab made famous. Rituximab and obinutuzumab labels are written for CD20-positive lymphoma and leukaemia; the newer CD20 x CD3 bispecifics assume it.

CD22 is a second B-cell antigen, kept even when CD19 is lost. Inotuzumab ozogamicin is labelled for CD22-positive acute lymphoblastic leukaemia.

CD25 is the part of the interleukin-2 receptor found on activated T cells and on some lymphoma cells; denileukin diftitox uses it as a doorway to deliver a toxin.

CD30 is the antigen of Hodgkin Reed-Sternberg cells and anaplastic large cell lymphoma. Brentuximab vedotin is labelled for Hodgkin lymphoma without a CD30 test and for peripheral T-cell lymphomas that express it.

CD33 is a myeloid antigen on the blasts of about 90 percent of acute myeloid leukaemias. Gemtuzumab ozogamicin's label requires CD33-positive disease.

CD38 is on almost every myeloma cell, so daratumumab and isatuximab are given without testing for it. The stain matters afterwards: CD38 falls after treatment and can confuse flow cytometry and blood typing.

CEACAM5 is the cell-surface form of the tumour marker CEA, high on many lung and bowel cancers. Tusamitamab ravtansine was tested in CEACAM5-high lung cancer but failed its phase 3 and no approval exists.

Claudin 18.2 is a tight-junction protein exposed on stomach cancer cells. Zolbetuximab requires at least 75 percent of tumour cells to stain moderately or strongly, the strictest expression threshold in any current label.

DLL3 sits on the surface of about 85 percent of small-cell lung cancers and almost no normal adult tissue. Tarlatamab is given without a DLL3 test.

FcRH5 is a surface protein found almost only on B cells and myeloma plasma cells, which makes it a target for T-cell engaging antibodies in multiple myeloma.

FcRH5 is a third myeloma surface target after BCMA and GPRC5D. Cevostamab, the FcRH5 x CD3 bispecific, is in phase 3; no approval or threshold exists yet.

Folate receptor alpha is a surface protein on most high-grade serous ovarian cancers. Mirvetuximab soravtansine requires FRα-positive disease, scored as at least 75 percent of cells with moderate or strong staining on the Ventana FOLR1 assay.

GPRC5D is a receptor on myeloma cells and in hair follicles, nails and taste buds. Talquetamab targets it without any test, and the side effects on skin, nails and taste follow from where it is expressed.

HER3 is a signalling partner of EGFR and HER2 present on most lung and breast cancers. Patritumab deruxtecan was studied in EGFR-mutant lung cancer without a HER3 threshold, and no approval exists.

Nectin-4 is expressed by almost every urothelial cancer, so enfortumab vedotin is given without a test. Nectin-4 amplification is being studied as a marker of especially strong response.

Tissue factor, the clotting trigger, is overexpressed on cervical and several other cancers. Tisotumab vedotin is labelled for cervical cancer without a tissue factor test.

TROP2 is on the surface of most breast and lung cancers. Sacituzumab govitecan and datopotamab deruxtecan are given without measuring it; a computational TROP2 score is being tested as a selector in lung cancer.