Antibody-drug conjugates (ADC)
Antibody-drug conjugates (ADCs) link a highly potent cytotoxic drug to a monoclonal antibody that recognizes a specific protein on cancer cells, so the chemotherapy is delivered mainly where the antibody binds. They sit on the border between chemotherapy and targeted therapy: the payload works like a classic cytotoxic drug, but the antibody gives it precision. Approved examples include trastuzumab emtansine in HER2-positive breast cancer and brentuximab vedotin in Hodgkin lymphoma, and newer conjugates are now used in breast, urothelial and other cancers.
How it works
Every conjugate has three parts: a monoclonal antibody that recognizes an antigen on cancer cells, a chemical linker, and a very potent cytotoxic drug — the payload. After the antibody binds its antigen, the whole complex is taken up into the cell, where the linker is cleaved in lysosomes and the drug is released; the freed payload damages the cell's DNA or its division machinery and leads to cell death. Some released drugs can also diffuse into neighbouring tumour cells (the so-called bystander effect), which can increase efficacy but may also add toxicity.
Linker stability is critical: it should hold the drug to the antibody while the conjugate circulates in the blood and release it only inside the target cell. Even with this precision, ADCs are not free of side effects — part of the payload is released outside the tumour, and the target antigens can also be present on some healthy cells. This combination of a targeted carrier with a cytotoxic payload is why ADCs are classified at the boundary of targeted therapy and chemotherapy.
Used in
Urinary Bladder
C67
enfortumab vedotin is an established option in advanced urothelial cancer