For the past decade, many researchers have complained bitterly that a trio of hotly contested patents has thwarted potentially life-saving research involving embryonic stem cells. Now, a decision to overturn one of these claims may radically change the notion of what's patentable in the life sciences.

The patents, held by the Wisconsin Alumni Research Foundation (WARF) and based on work by University of Wisconsin–Madison stem cell pioneer James Thomson, cover preparations of primate and human embryonic stem cells and methods for deriving them. In 2006, the New York–based Public Patent Foundation (PPF) led efforts to challenge the three patents on grounds that the claims were too broad and not sufficiently unique compared to similar techniques in mice.

The US Patent and Trademark Office ultimately ruled in WARF's favor, in 2008, after the foundation narrowed its claims. Two of those decisions were final, but, because a system for appealing patents was put in place in 1999 applying to all patents from then on, and the third claim was filed in 2001, the PPF could legally appeal the third decision.

On 28 April, the US patent agency upheld the PPF's appeal. The reversal serves as a precedent should WARF attempt to defend the other two patents against new lawsuits as well, says Dan Ravicher, executive director of the PPF, which also led the successful campaign against Myriad's two breast cancer gene patents in partnership with the American Civil Liberties Union. The court's opinion “directly impacts the one patent, but there's no argument that it would not similarly invalidate the other two patents had we had the right to appeal them, as well,” Ravicher says.

Greg Bonfiglio, managing partner of Proteus Venture Partners, a Palo Alto, California-based investment and advisory firm for regenerative medicine companies, says the ruling now sets a higher bar on obviousness for all biomedical patents. “The line has now been drawn much more broadly,” he says. “One way to read this opinion is, 'anything that was done in mouse is now not patentable in humans.'”

If the patent office adopts that view, the WARF decision could potentially affect the intellectual property landscape for induced pluripotent stem (iPS) cells. “The cases going forward, whether they're embryonic stem cells or iPS cells, are going to be narrow,” says David Resnick, a patent attorney with Nixon Peabody in Boston.

So far, the Patent and Trademark Office has awarded only one iPS-related patent, granted to San Diego stem cell company Fate Therapeutics, and the patent is fairly limited in scope (Nat. Med. 16, 246, 2010).