monoclonal antibody
A monoclonal antibody is a laboratory-made copy of one of the immune system's guided missiles, all identical and aimed at a single target. Your body naturally makes antibodies, Y-shaped proteins that latch onto specific foreign shapes. A monoclonal antibody is a population grown from one clone, so every molecule binds exactly the same spot, giving exquisite precision.
Once bound, a therapeutic antibody can act in several ways: it may block a receptor or signalling molecule, flag the target cell for destruction by the patient's immune system, or simply mop up an excess protein. In cancer, trastuzumab binds the HER2 receptor overexpressed on some breast tumours, and rituximab binds CD20 on B-cell lymphomas. Many other monoclonal antibodies treat autoimmune and inflammatory diseases by neutralising specific immune signals.
Because they are large proteins, monoclonal antibodies are given by injection or infusion rather than swallowed, and they tend to have long half-lives, so dosing is often weekly to monthly. They are a core form of biologic therapy. Their main risks include infusion reactions and, depending on the target, increased infection risk; some can provoke immune responses against the drug itself.
Trastuzumab, a monoclonal antibody against HER2, markedly improves survival in HER2-positive breast cancer, but only in tumours that actually overexpress HER2.
Precision binding works only when the matching target is present, linking the drug to biomarker testing.
Antibody names ending in -mab signal a monoclonal antibody; subtler stems once marked how human the molecule is (fully human, humanised or chimeric), which affects how likely the body is to react against it.