The Food and Drug Administration (FDA) approved Erbitux™ (cetuximab) for the treatment of metastatic colorectal cancer that expresses the epidermal growth factor receptor (EGFR). The FDA indication specifies that Erbitux™ be used in combination with the chemotherapy agent irinotecan (Camptosar®) in patients who stopped responding to previous therapy with irinotecan, or as a single agent in patients who are not able to tolerate irinotecan-based chemotherapy.

Colorectal cancer is the second leading cause of cancer deaths in the United States. Metastatic colorectal cancer refers to cancer that has spread from the colon or rectum to distant sites in the body, often invading vital organs. Treatment for metastatic colorectal cancer consists of chemotherapy with or without surgery and/or radiation. A critical roadblock in treatment involving chemotherapy is that patients tend to build a tolerance to a chemotherapy agent after an extended period of use, rendering the chemotherapy agent inactive against the cancer. A second hurdle involving treatment with chemotherapy is the side effects caused by treatment, which leaves a significant portion of patients not able to tolerate therapy. Since the arsenal of chemotherapy agents in the treatment of colorectal cancer is very limited, patients who stop responding to a chemotherapy agent and/or who are not able to tolerate treatment with chemotherapy are left with few effective clinical options. One area of focus in cancer research is the development of agents that prevent or reverse resistance to chemotherapy agents so anti-cancer effects can be prolonged or enhanced with specific treatments, as well as the development of agents with mild and limited side effects.

Erbitux™ is the first monoclonal antibody that has been approved for the treatment of colorectal cancer. It is targeted against the EGFR pathway, which is implicated in the initiation and/or continuation of the growth of cancerous cells. Erbitux™ binds to a specific site in the EGFR pathway, which blocks or reduces the growth-stimulatory effects of EGFR on cancer cells.

One clinical trial that prompted the FDA approval was conducted by researchers from England, who evaluated the addition of Erbitux™ to irinotecan in patients with metastatic colorectal cancer that had stopped responding to previous therapy with irinotecan. The trial included 329 patients who had stopped responding to prior irinotecan either during treatment or within 30 days following treatment. Patients were then divided into two groups: those who were treated with Erbitux™ and irinotecan and those treated with Erbitux™ only. Patients treated with Erbitux™ only were allowed to” cross over” if their cancer progressed to be treated with Erbitux™ plus irinotecan. The overall anti-cancer response rates were 23% for patients treated with Erbitux™ plus irinotecan, compared to 11% for those treated with Erbitux™. The average time to cancer progression was 4.1 months for patients treated with Erbitux™ plus irinotecan, compared to only 1.5 months for those treated with Erbitux™. The average duration of survival was 8.6 months for patients treated with Erbitux™ plus irinotecan, compared to 6.9 months for patients treated with Erbitux™ only. More patients experienced side effects in the group treated with Erbitux™ plus irinotecan, with diarrhea being the most common serious side effect.

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Patients with metastatic colorectal cancer that expresses EGFR who have stopped responding to irinotecan or who are not able to tolerate treatment with irinotecan should speak with their physician about the risks and benefits of treatment with Erbitux™.

Reference: ImClone Systems Inc. and Bristol-Myers Squibb Company. ErbituxM (Cetuximab) receives FDA approval to treat irinotecan refractory or intolerant metastatic colorectal cancer. Available at: http://www.erbitux.com/erbitux/pre/index.jsp?BV_UseBVCookie=Yes. Accessed February 2004.

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