The Food and Drug Administration (FDA) has approved Humira (adalimumab) to treat adult patients with moderately to severely active Crohn's disease, a chronic inflammatory disease of the intestines, which affects an estimated one million Americans.

Humira is a human-derived, genetically engineered monoclonal antibody (a protein that can be produced in large quantities in a manufacturing plant). The product acts to reduce excessive levels of human tumour necrosis factor (TNF) alpha, which plays an important role in abnormal inflammatory and immune responses. The labelling includes a boxed warning about potential serious adverse events.

Crohn's disease is a chronic, incurable, inflammatory bowel disease that causes diarrhoea, cramping and abdominal pain, and in some cases, abnormal connections (fistulas) leading from the intestine to the skin.

"Humira has been shown to reduce signs and symptoms, and to induce and maintain clinical remission of Crohn's disease in patients who have had an inadequate response to conventional therapy, and in those patients who did not benefit from treatment, or who were intolerant to previous treatment with Remicade (infliximab) therapy," said Dr Douglas Throckmorton, deputy director of FDA's Centre for Drug Evaluation and Research. "Today's approval provides patients and their health care providers with a new treatment option.

The product has been studied in 1,478 patients with Crohn's disease in four clinical trials comparing the drug to a placebo (contains no active ingredient) and two longer-term extension studies.

The labelling of Humira includes a boxed warning, the strongest type of label warning, that use of this product has been associated with serious, sometimes fatal, infections, including cases of tuberculosis, opportunistic infections, and sepsis. Before initiating Humira treatment, patients should be evaluated for tuberculosis risk factors and tested for latent tuberculosis infection. Other serious adverse events reported by Humira users include lymphoma, a type of cancer. The most frequent adverse events included upper respiratory infections, sinusitis, and nausea.

Humira requires subcutaneous injections (under the skin) to initiate treatment for Crohn's disease, and maintenance treatment is administered as one injection every other week.

Humira was previously approved for the treatment of three autoimmune diseases: rheumatoid arthritis, a chronic inflammation of the joints; psoriatic arthritis, which causes joint swelling and scaly skin; and ankylosing spondylitis, a systemic rheumatic disease that affects the spine and sacroiliac joints. Humira is manufactured by Abbott Laboratories, Abbott Park, Ill.