rituximab
Meaning of rituximab: Because CD20 is absent from stem cells and from antibody-producing plasma cells, the B cell population rebuilds and existing immunity is largely kept.
Definition of rituximab
Rituximab is a laboratory-made antibody that locks onto CD20, a protein on the surface of B lymphocytes, one of the two main kinds of lymphocyte. Marking those cells causes the immune system to destroy them, emptying the body of B cells for months. It is used where B cells drive the problem, in several lymphomas and leukemias and in a number of autoimmune diseases.
How does it destroy the cells it binds?
An antibody does not kill anything by itself; it marks a target for something else to act on. Once rituximab coats a B cell, three things can follow. Immune cells that recognize the antibody's tail attach and kill the cell. The complement system, a cascade of blood proteins, assembles on the coated surface and punches through it. And the binding itself can trigger the cell's own self-destruct program. Rituximab is a chimeric antibody, meaning the part that grips CD20 came originally from mouse cells and was grafted onto a human framework, which is one reason reactions during the first infusion are relatively common.
What is it used for?
| Group | Examples |
|---|---|
| B cell cancers | Several forms of non-Hodgkin lymphoma and chronic lymphocytic leukemia, usually combined with chemotherapy |
| Autoimmune disease | Rheumatoid arthritis after other treatments, vasculitis associated with particular antibodies, pemphigus vulgaris |
It is not a standard treatment for classical Hodgkin lymphoma, because the malignant cells there usually do not carry CD20 and so present nothing for the drug to bind.
What are the main considerations?
Reactions during infusion, with fever, chills, rash or breathlessness, are most likely with the first dose and are managed by slowing the rate and giving medication beforehand. The depleting effect lasts many months, so infections are more frequent afterward and response to vaccination is reduced while B cells are absent. Hepatitis B can reawaken in someone who has carried the virus quietly for years, which is why that status is established before treatment starts. A rare brain infection, progressive multifocal leukoencephalopathy, has been reported. Treatment is usually given by infusion into a vein, though an injection under the skin is available for some conditions.
Used in a sentence
Rituximab was included in the treatment regimen for the patient's B-cell lymphoma.
Good to know
Rituximab targets a protein carried by B lymphocytes generally rather than by cancer cells specifically, so normal B cells are removed alongside malignant ones and the immune effects persist for months.