NEW YORK (AP) _ Thimble-size implants allowed guinea pigs and a monkey churn out a protein that can treat hemophilia, researchers reported in a study that suggests a new approach to treatment.

The animals did not have the bleeding disorder, so the study didn't directly test whether the implants could reverse the disease.

But blood samples showed the implants converted a natural protein from the animals into useful amounts of an activated form, called Factor VIIa, that is now used in hemophilia treatment.

The work was reported in the March issue of the journal Nature Biotechnology by Dr. Harvey Pollard of the Uniformed Services University School of Medicine in Bethesda, Md., and colleagues.

Hemophilia is caused by the lack of a clot-promoting protein, usually one called Factor VIII. Patients can be treated with infusions of that protein. But some 15 percent of such patients develop antibodies that inactivate the infused protein. They can be treated with infusions of Factor VIIa instead, but that is expensive and the protein disintegrates quickly.

The implants could avoid both those drawbacks, as well as the antibody problem, the researchers said.

The implants are porous chambers containing a substance that converts Factor VII to Factor VIIa. The monkey, which had three implants in its abdomen, generated Factor VIIa for a month before the implants were removed for inspection. However, the production petered out over that period, and Pollard said it is not clear why.

Pollard said he hopes human testing can begin within a year or two.