The GSK-OncoMed pact is the first major deal focused on cancer stem cell R&D, which is undergoing explosive growth. John Bates, the director of Biopharm Reports, in Cambridge, UK, says the number of companies devoted to this research has grown from 17 in April 2007 to nearly 40 today. What's more, patents covering developments in cancer stem cells doubled to about 70 in 2007, he adds. The problem is that not everyone even believes that targeting cancer stem cells will yield therapeutic benefits.
George Schreiner, CEO with Raven Biotechnologies in San Francisco, attributes the burst of commercial interest to recent evidence of cancer stem cells in solid tumors. Scientists have suspected since the 1950s that the cells play a role in blood tumors, such as acute myeloid leukemia, but their existence in solid tumors became evident only in 2003. That's when Michael Clarke, currently associate director of Stanford University's Institute for Stem Cell and Regenerative Medicine, and his then post-doc, Mohamed Al-Hajj, claimed to find cancer stem cells in breast tumors. The cells had two markers that are now synonymous with cancer stem cells: high expression of the antigen CD44 and low expression of antigen CD24. Isolated on the basis of these markers, the human cells were cultured and introduced into immunocompromised mice. Clarke and Al-Hajj found that only a few of the cells could spawn aggressive, metastatic tumors in the animals. Those findings bolstered a theory that solid tumors arise from a small population of cancer stem cells that, like normal stem cells, have the capacity for self-renewal. Clarke and his colleague Max Wicha, the director of the University of Michigan Comprehensive Cancer Center, founded OncoMed to pursue clinical opportunities in cancer stem cells in 2004. They now sit on the company's scientific advisory board.
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