New gene mutation linked to cancer drugs' success

LONDON Oct 23 (Reuters) - Scientists have uncovered a second gene mutation that determines which patients will respond to the bowel cancer drugs Erbitux and Vectibix, opening the way to still more targeted treatment.

Treating patients based on their genetic make-up is a growing trend in oncology, and the latest research, reported at a medical meeting in Geneva on Thursday, suggests multiple mutations have a role to play.

Experts already knew that Erbitux, developed by ImClone IMCL.O and sold by Bristol-Myers Squibb (BMY.N) and Merck KGaA (MRCG.DE), and Vectibix, from Amgen (AMGN.O), only work in tumours containing the normal, or wild-type, version of a gene known as KRAS.

Now a second gene, called BRAF, has also been shown to be involved, though to a lesser extent.

KRAS mutations explain about 30-40 percent of cases in which patients fail to respond to Erbitux and Vectibix. But results of a study presented by Federica Di Nicolantonio of the University of Turin School of Medicine in Italy suggest that BRAF mutations may account for another 12 percent.

The research was presented at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Geneva.

Experts have argued about the market impact of using genetic markers as way to pre-select patients for treatment with costly modern cancer drugs.

Drug companies have welcomed the development, arguing it is good for long-term sales, but some analysts say sales are likely to take at least a short-term hit. (Reporting by Ben Hirschler, editing by Will Waterman)