GSK's lapatinib is first drug to target breast cancer tumorigenic stem cells

UK drug major GlaxoSmithKline presented results from a prospective study which showed that its drug lapatinib decreases tumorigenic stem cells in primary breast cancers of women on neoadjuvant treatment, at the sixth European Breast Cancer Conference, held in Berlin, Germany.

In the trial, 45 patients with locally-advanced ErbB2 over-expressing breast cancer, received lapatinib before surgery, initially as a single agent for the first six weeks, followed by a combination of lapatinib plus weekly Herceptin (trastuzumab) and three-weekly docetaxel for 12 weeks. Biopsies were taken at time of diagnosis and after six weeks of lapatinib, and assessed for tumorigenic cells. Results showed significant tumor regression (median decrease of -60.8%, p=0.001) in primary tumors after only six weeks of single-agent lapatinib therapy. Unlike treatment with chemotherapy, the GSK drug decreased tumorigenic breast cancer stem cells from 10.6% to 4.7%. The pathologic complete response rate following combination treatment (lapatinib plus trastuzumab and docetaxel) was 63%.

The US Food and Drug Administration approved the drug last year under the brand name Tykerb (Marketletter March 19, 2007). The FDA cleared the targeted oral agent in combination with Roche's Xeloda (capecitabine) for patients who failed to respond to the Swiss drug major's breakthrough drug Herceptin. This approval marked lapatinib's first entry into a market worth $35.0 billion a year.