CHICAGO (Reuters) - The U.S. National Institutes of Health (NIH) will sharply curtail medical research studies using chimpanzees, humans' closest relative in the animal kingdom, after an expert panel said such studies are rarely warranted.

NIH Director Dr. Francis Collins said on Thursday his agency will adopt new recommendations from the Institute of Medicine (IOM), part of the National Academies of Sciences, that will limit research funded by the agency involving chimpanzees.

After very serious and careful consideration, I have decided to accept the IOM committee recommendations, Collins told reporters on a telephone briefing.

He said effective immediately, the NIH will stop accepting any applications for research grants using chimpanzees until the agency can get rules in place that will allow it to adhere to the new guidelines.

The NIH in 2010 asked the IOM to reassess the use of chimpanzees in medical research in light of new technologies that provide for other testing methods.

In its report, issued on Thursday, the IOM panel of experts said use of chimpanzees in government-funded medical research should be reserved only for studies where no suitable alternative is available or where testing in people would be unethical, and only for life-threatening or debilitating conditions.

Research use of animals that are so closely related to humans should not proceed unless it offers insights not possible with other animal models and unless it is of sufficient scientific or health value to offset the moral costs, Jeffrey Kahn of Johns Hopkins Berman Institute of Bioethics in Baltimore, who chaired the committee.

We found very few cases that satisfy these criteria, Kahn said in a statement.

MINIMIZING PAIN AND DISTRESS

The report was initially requested by the U.S. Congress, which has been considering legislation that would ban research on chimpanzees and other great apes, which use tools and have complex social structures.

Congress became interested after animal rights groups protested NIH's decision to transfer chimpanzees housed at Alamogordo, a primate reserve facility that does not have an active chimpanzee research primate facility.

The chimps were set to be transferred to the Southwest National Primate Research Center, a setting where active research was allowed. Animals rights groups, including the Humane Society of the United States, instead wanted the chimps to be permanently retired.

The controversy prompted members of the Senate to call for an assessment of how chimpanzees are used in biomedical research.

The European Union banned research on use of all great apes in 2010. The EU ban also includes a provision using these animals in cases where no other suitable alternative could be found.

In its report, the panel of IOM experts said the NIH should limit the use of chimpanzees in behavioral research to studies that provide insights into behavior, mental health, emotion, or cognition that could not be obtained otherwise.

It also said current research on monoclonal antibodies, drugs that use molecules engineered to help the immune system, could continue. Such research is a major area for biotechnology companies and has led to the development of live-saving medicines worth billions of dollars.

The report said NIH should require these studies to be performed only on animals that do not resist participating, using techniques that are minimally invasive and reduce potential pain and distress.

Researchers who conduct studies with chimpanzees must house them in appropriate physical and social environments, or in natural habitats.

Collins said NIH has more than 600 chimpanzees in its research facilities, and it will soon start figuring out what to do with them, including assessing how many are needed for research in the event of a global disease pandemic.

He estimates that NIH currently is funding about 27 grants involving chimpanzee research outside of the agency, and there are about 10 studies going on within NIH.

We would guess that something like 50 percent of those may no longer fit the principles and criteria laid out in the IOM report, Collins said.

The IOM did not address use of chimpanzees in research done by industry, but Kahn, writing in the journal Science, urged companies to take up the same standard.

The group was split on whether chimpanzees should be used in research for a hepatitis C vaccine, a disease that affects 3.2 million Americans and can cause liver disease and cancer.

Chimpanzees and humans are the only two species that are susceptible to HCV infection, and no other suitable animal models currently exist to test a vaccine.

(Editing by Michele Gershberg and Sandra Maler)