The U.S. Food and Drug Administration (FDA) has approved the drug cetuximab, known as Erbitux, for the treatment of advanced colorectal cancer. Studies have shown that Erbitux can shrink tumors and delay tumor growth, but it is not known if treatment will improve symptoms or help patients live longer.

Erbitux, developed by ImClone Systems Incorporated, is the first monoclonal antibody approved for treatment of colorectal cancer. It will be used in patients who are no longer responding to or cannot take the chemotherapy drug irinotecan. Erbitux works by blocking a type of protein called epidermal growth factor receptor (EGFR); the action deprives tumors of an element they need to grow. The FDA also has approved a test kit to help doctors determine which patients have these receptors and are therefore eligible for the treatment.

Erbitux is administered intravenously and can be given alone or combined with irinotecan. Potential side effects include difficulty breathing, low blood pressure, rash, fatigue, and fever. Some patients have also developed scar tissue in their lungs, called interstitial lung disease, but doctors don't know whether Erbitux caused the condition.

Erbitux was first submitted for approval in 2001, but the FDA rejected it, saying the application lacked important information about the safety and effectiveness of the drug. (The rejection led to a stock sale scandal that embroiled domestic lifestyle expert Martha Stewart.) Since then, ImClone has conducted more clinical trials and obtained much of the information sought during the first approval request, the FDA said.

The current approval was based on trials involving nearly 500 patients. Erbitux combined with irinotecan caused tumors to shrink in almost 23% of patients, and delayed tumor growth by just over 4 months. Erbitux alone caused tumors to shrink in nearly 11% of patients, and delayed tumor growth by 1.5 months.

Two more studies involving 2,000 patients are ongoing to determine if Erbitux can stop colorectal cancer from progressing or help patients live longer.