The New York Times

The United States Patent and Trademark Office has made a preliminary decision to revoke three fundamental patents on human embryonic stem cells. If the decision stands, some scientists and consumer groups say it could loosen restrictions on research in a promising new field.

Patent examiners rejected all the claims of the three patents that are based on the work of James A. Thomson of the University of Wisconsin, who is widely viewed as having been the first to isolate human embryonic stem cells and grow them in culture. The oldest patent was issued in 1998 and the most recent was issued last year.

In decisions posted on the agency’s Web site yesterday, the examiners said that Dr. Thomson’s cells appeared to be the same as, or obvious variations of, cells described in earlier scientific papers or in patents issued to others.

The decisions were the initial steps in a re-examination of the patents, but the matter is far from over. Some patent lawyers said it was not unusual for the patent office to initially reject all claims of a patent under re-examination.

The Wisconsin Alumni Research Foundation, or WARF, the patent licensing arm of the university, will now have a chance to argue its case. The patents remain in force until the issue is resolved, which could be years.

“WARF has absolute confidence in the appropriateness and legitimacy of these patents,” Carl E. Gulbrandsen, the managing director of the Wisconsin foundation, said yesterday in a statement. “It is inconceivable to us that Dr. Thomson’s discovery, which Science magazine heralded as one of the greatest scientific discoveries in history, would be found to not be worthy of a patent.”

But Daniel B. Ravicher, president and executive director of the Public Patent Foundation, the nonprofit organization that had challenged the patents, said there was now a greater likelihood that the claims would be revoked or narrowed.

“It’s not the final nail in the coffin, but it’s a heavy body blow,” Mr. Ravicher said. “This rejection is substantial, and it will cause a significant deterioration in the impact the patents will have in the marketplace.”

The Public Patent Foundation, which seeks to overturn patents it believes are not in the public interest, sought the re-examination last July. It acted with the Foundation for Taxpayer and Consumer Rights, a California consumer group that said the patents could impede that state’s $3 billion stem cell research program.

Human embryonic stem cells have the potential to turn into any type of body tissue.

Dr. Thomson’s isolation of them in 1998 set off a big effort to turn that basic technology into treatments for various diseases.

Some scientists complained, however, that the Wisconsin patents were too broad and that the university’s enforcement efforts impeded research.

At least one company, Invitrogen, has said it located some of its stem cell research abroad because the patents apply only in the United States.

Dr. Evan Snyder, director of stem cell research at the Burnham Institute in La Jolla, Calif., said WARF “hindered the field” to enhance its proprietary position, making it expensive to obtain cell lines and for scientists to collaborate. He said the patent challenge “sure had a lot of cheerleaders on the sidelines” among scientists.

Dr. Snyder conceded that WARF, in reaction to complaints, has made it easier to use the cell lines for research.

WARF, which claims that the patents apply to all human embryonic stem cells in the United States, has said its terms are reasonable. Academic researchers get free patent licenses and pay $500 for cells. Companies are charged $75,000 to $400,000.

The Geron Corporation, which financed some of Dr. Thomson’s research, has exclusive commercial rights to heart, nerve and pancreatic cells derived from the human embryonic stem cells.

The patents in contention are 5,843,780, which covers primate embryonic stem cells and was issued in 1998; 6,200,806, which covers human and primate embryonic stem cells and was issued in 2001; and 7,029,913, which covers cultures of human or primate embryonic stem cells and was issued in 2006.