How does the drug Rituxan work?

Rituxan (rituximab) is a type of biological drug called a monoclonal antibody, which works by targeting the CD20 protein antigen displayed on the surface of B-cells.

B-cells, which are also called B-lymphocytes, are a type of white blood cell. They are part of the body’s humoral immune response, which is mediated by antibodies (also known as immunoglobulins). When a B-cell encounters a foreign invader, a process is initiated that leads to the production of antibodies that circulate, target and destroy the invader.

How Rituxan works in patients with lymphoma and leukemia

Some health conditions also affect B-cells, like non-Hodgkin’s lymphoma (NHL) and chronic lymphocytic leukemia (CLL), which are types of blood cancer that affect B-cells. CD20 is an antigen that is displayed on certain B-cells, providing a target for Rituxan to latch onto.

Rituxan recruits a patient’s own immune system cells to attack B-cells. However, the exact methods by which Rituxan works are not completely clear. Studies suggest that Rituxan may recruit macrophages, which are also a type of white blood cell, to ‘eat’ the B-cells via a process called antibody-dependent phagocytosis. However, it is unclear to what extent Rituxan works to treat cancer via this mechanism.

Another way in which Rituxan is thought to work is via a process called antibody-dependent cellular cytotoxicity (ADCC). By recruiting natural killer cells, yet another type of white blood cell, and possibly macrophages, Rituxan is thought to bring about a process that causes B-cell death by lysis or bursting.

Complement-dependent cytotoxicity is also thought to be a mechanism via which Rituxan is able to destroy B-cells. The complement system, or complement cascade as it is also known, is a system made up of small proteins that circulate in the blood, which when activated lead to the B-cells being destroyed by phagocytosis. Rituxan is able to bind to proteins in the complement system and initiate the cascade of events that targets and destroys the B-cells that it attaches to.

Rituxan is also thought to work synergistically with the chemotherapy drugs that it is used with. It has been suggested Rituxan may induce apoptosis, or programmed cell death, in chemo-sensitized cells via direct signaling. It is thought that Rituxan may somehow sensitize cancer cells to the effects of other chemotherapy drugs.

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How Rituxan works in patients with autoimmune disorders

Rituxan depletes B-cells, which can cause swelling and joint damage in people with autoimmune disorders, such as rheumatoid arthritis. It is also thought to work by depleting B-cells in patients with the autoimmune disorders granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). Instead of producing helpful antibodies to fight off invaders, B-cells in people with GPA and MPA are thought to produce harmful inflammation-causing auto-antibodies. By reducing the number of B-cells, Rituxan helps limit the production of auto-antibodies.

Rituxan is a monoclonal antibody that can be given alone or in combination with chemotherapy. It is used for the treatment of non-Hodgkin’s lymphoma (NHL) and chronic lymphocytic leukemia (CLL), rheumatoid arthritis and other conditions. Rituxan is administered via an intravenous infusion.