Treatment with cetuximab (Erbitux) was less effective for patients with advanced colorectal cancer with a certain gene mutation, a new study found. Scientists already knew that the presence of K-ras mutations explains about 30 to 40 percent of cases in which colorectal cancer patients fail to respond to Erbitux, developed by ImClone and sold by Bristol-Myers Squibb and Merck KGaA, and Vectibix, from Amgen. The latest findings added another 12 percent.

Researchers led by Dr. Federica Di Nicolantonio of the Institute of Cancer Research and Treatment at the University of Turin in Italy analyzed DNA from 113 tumors in advanced colorectal cancer patients. They detected a second gene, called BRAF, that may influence the patients’ response to therapy with Erbitux or Vectibix.

Erbitux blocks a protein called epidermal growth factor, that is supposed to be one of the reasons for which cancer cells multiply. The Kras gene controls the way the epidermal growth factor works. If Kras is non-mutated, then Erbitux can work at its highest potential, if not, the treatment could prove less efficient.

The findings were presented at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Geneva. The research was funded by the European Union, the Italian Association for Cancer research and the Italian Ministry for Science and Health.

In June, the European Medicines Agency, based in London, has approved the use of Erbitux, produced by Merck KGaA, as a first line treatment against colorectal cancer that has spread in the patient’s body. The German company cautioned that the medicine works best for patients that have a KRAS non-mutated, or wild-type tumor.