The government on Thursday said it would adopt strict new limits on using chimpanzees in medical research, after a prestigious scientific group recommended that experiments with humans' closest relative be done only as a last resort.
The National Institutes of Health agreed that science has advanced enough that chimps seldom would be needed to help develop new medicines.
NIH Director Francis Collins temporarily barred new federal funding for research involving chimps, and said a working group will review about 37 ongoing projects involving the animals to see if they should be phased out.
Chimps' similarity to people "demands special consideration and respect," Mr. Collins said.
These apes' genetic closeness to humans has long caused a quandary. It's what has made them so valuable to scientists for nearly a century. They were vital in creating a vaccine for hepatitis B, for example, and even were shot into space to make sure the trip wouldn't kill the astronauts next in line.
But that close relationship also has had animal rights groups arguing that using chimps for biomedical research is unethical, even cruel.
Chimp research already was dwindling fast as scientists turned to less costly and ethically charged alternatives.
Thursday's decision was triggered by an uproar last year over the fate of 186 semiretired research chimps that the NIH, to save money, planned to move from a New Mexico facility to an active research lab in Texas.
Where and how to house those animals - and others scattered around the country who probably no longer will be needed - are among the issues that Mr. Collins said a government working group will decide as it determines how to implement the new research restrictions.
The Institute of Medicine's recommendation on Thursday stopped short of the outright ban that animal rights activists had pushed. Instead, it urged strict limits on biomedical research - testing new drugs or giving animals a disease - that would allow using chimps only if studies could not be done on other animals or people themselves, and if foregoing the chimp work would hinder progress against life-threatening or debilitating conditions.
The panel advised the government to limit use of chimps in behavioral and genetic research as well, saying such studies must provide insights that otherwise are unattainable - and use techniques that minimize any pain or distress.
"We understand and feel compelled by the moral cost of using chimpanzees in research," said bioethicist Jeffrey Kahn of Johns Hopkins University, who chaired the Institute of Medicine panel. "We have established criteria that will set the bar quite high for justification of the use of chimpanzees."
The U.S. is one of only two countries known to still conduct medical research with chimpanzees; the other is Gabon, in Africa. The European Union essentially banned such research last year.
Here, too, the practice was becoming uncommon. The Institute of Medicine's investigation found over the past 10 years, the NIH has paid for just 110 projects of any type that involved chimps. There are not quite 1,000 chimps available for medical research in the country.
While it's impossible to say how many have been used in privately funded pharmaceutical research, the industry is shifting to higher-tech and less costly research methods. One drug company, GlaxoSmithKline, adopted an official policy ending its use of great apes, including chimpanzees, in research.