Colon Cancer Drugs Erbitux and Vectibix May Require Gene Screening

An FDA advisory panel is scheduled to meet today to review whether the drug labels for Erbitux and Vectibix, which are used to treat colon cancer, should indicate that patients be screened for the KRAS gene mutation, as the costly drugs do not work in people with the gene mutations.

Erbitux (cetuximab) and Vectibix (panitumumab) are epidermal growth factor (EGFR) protein inhibitors. They interfere with signals in cancer cells that cause them to grow, divide and proliferate. However, for individuals with KRAS mutations, research has established that the drugs do not work.

Erbitux and Vectibix can cost between $8,000 and $10,000 a month, and use of the drugs by individuals with the gene mutations not only causes unnecessary expense, but also exposes individuals to potentially serious side effects, such as severe skin reactions.

Last year, Erbitux, which was introduced by Eli Lilly & Co’s ImClone in 2004, generated sales of $1.3 billion and Vectibix, which was introduced by Amgen, Inc. in 2006, generated sales of $170 million.

The KRAS gene mutation is present in about 40% of people with colon cancer, and the drug makers are likely to experience a drop in sales if they are required to indicate patients should be screened for the gene mutation. However, a growing number of experts have called for the screening, as the drugs should not be used in those with no chance of benefits.

KRAS screening tests are readily available, involving analysis a sample of tissue from a tumor.

The FDA panel of independent advisors will meet on December 16, 2008 to review the data and make a recommendation to the FDA about whether the drug makers should be forced to update the prescribing information to advise patients that the treatment will not work if they carry the genes.

Although the FDA is not required to follow the recommendations of their advisory panels, they usually do.