A decade ago, the United States granted a series of patents that some say changed the embryonic stem cell (ESC) field forever. The Wisconsin Alumni Research Foundation (WARF) received three broad patents related to a method for isolating human ESCs that was developed by James Thomson at the University of Wisconsin–Madison. These patents, which effectively covered all ESC lines regardless of who made them or how they are generated, were so far reaching, many critics argued, that they effectively put a stranglehold on the ESC field. Indeed, only one company—Menlo Park, Calif.–based Geron Corp.—has ever received approval from the US Food and Drug Administration to test ESC-derived products in the clinic. Companies working with ESCs "are walking on very thin ice right now," says Jeanne Loring, director of the Scripps Research Institute's Center for Regenerative Medicine in La Jolla, Calif., who founded the now-defunct ESC-based biotech company Arcos BioScience.
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