Efalizumab is a formerly available medication

Medication

A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

 designed to treat autoimmune diseases, origianally marketed to treat psoriasis

Psoriasis

Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...

. As implied by the suffix -zumab

Nomenclature of monoclonal antibodies

The nomenclature of monoclonal antibodies is a naming scheme for assigning generic, or nonproprietary, names to monoclonal antibodies. An antibody is a protein that is produced in B cells and used by the immune system of humans and other vertebrate animals to identify a specific foreign object like...

, it is a recombinant

Recombinant DNA

Recombinant DNA molecules are DNA sequences that result from the use of laboratory methods to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms...

 humanized

Humanized antibody

Humanized antibodies are antibodies from non-human species whose protein sequences have been modified to increase their similarity to antibody variants produced naturally in humans. The process of "humanization" is usually applied to monoclonal antibodies developed for administration to humans...

 monoclonal antibody administered once weekly by subcutaneous injection

Injection (medicine)

An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...

. Efalizumab binds to the CD11a

CD11a

Integrin, alpha L , also known as ITGAL, is a human gene which functions in the immune system. It is involved in cellular adhesion and costimulatory signaling...

 subunit of lymphocyte function-associated antigen 1 and acts as an immunosuppressant

Immunosuppressant

An immunosuppressant is any substance that performs immunosuppression of the immune system. They may be either exogenous, as immunosuppressive drugs, or endogenous, as ,e. g., testosterone...

 by inhibiting lymphocyte activation and cell migration out of blood vessels into tissues. Efalizumab was associated with fatal brain infections and was withdrawn from the market in 2009.

Known side effects include bacterial sepsis

Sepsis

Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

, viral meningitis

Meningitis

Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

, invasive fungal disease and progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy , also known as progressive multifocal leukoencephalitis, is a rare and usually fatal viral disease that is characterized by progressive damage or inflammation of the white matter of the brain at multiple locations .It occurs almost exclusively in...

 (PML), a brain infection caused by reactivation of latent JC virus

JC virus

The JC virus or John Cunningham virus is a type of human polyomavirus and is genetically similar to BK virus and SV40. It was discovered in 1971 and named using the two initials of a patient with progressive multifocal leukoencephalopathy...

 infection. Four cases of PML were reported in plaque psoriasis patients, an incidence of approximately one in 500 treated patients.

Due to the risk of PML, the European Medicines Agency

European Medicines Agency

The European Medicines Agency is a European agency for the evaluation of medicinal products. From 1995 to 2004, the European Medicines Agency was known as European Agency for the Evaluation of Medicinal Products.Roughly parallel to the U.S...

 and the FDA recommended suspension from the market in the European Union

European Union

The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

and the United States, respectively. In April, 2009, Genentech Inc. announced a phased voluntary withdrawal of Raptiva from the U.S. market.