Glaxo's Tykerb reduces breast cancer stem cells

LONDON, April 17 (Reuters) - GlaxoSmithKline Plc's (GSK.L) new cancer drug Tykerb can decrease tumour-causing breast cancer stem cells, offering the hope it may help stop disease from recurring, scientists said on Thursday.

Tykerb, also known as lapatinib, targets the cell surface receptors that play an important role in many types of cancer.

Dr. Angel Rodriguez from the Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, said it reduced cancer stem cells in the primary breast cancers of women receiving treatment ahead of surgery.

A trial involving 45 patients showed there was significant tumour regression after only six weeks of use, he told the 6th European Breast Cancer Conference in Berlin.

The findings suggest that targeting specific signalling inhibitors responsible for stem cell self-renewal may be an effective method of long-term eradication of cancer.

"This indicates that the stem cells themselves should be the specific target of chemotherapy drugs," Rodriguez said.

"Rather than the broad brush approach, in which cells are killed indiscriminately, targeting the stem cells may be more effective and also prevent some of the unpleasant side effects associated with conventional chemotherapy treatment."

Scientists believe that cancer stem cells come into being through damage to their own DNA, which affects the regulation of their self-renewal. The stem cell population then continues to renew itself as it generates new cells for the tissue.

"This means that, unlike other cells, the stem cell has lost control over its own population size," Rodriguez said.

Tykerb -- a rival to Herceptin from Roche Holding AG (ROG.VX) and Genentech Inc DNA.N -- is seen by Glaxo as a potential blockbuster in the long term, although sales to date have been slow.

In United States, it costs between $2,000 and $3,000 a month, according to Rodriguez. (Reporting by Ben Hirschler; Editing by Quentin Bryar)