Chimpanzees will no longer be used for US government research and the remaining 50 chimps in federal custody will be sent to a sanctuary for retirement, health authorities said Wednesday.
The decision by the National Institutes of Health came two and a half years after the agency announced it would phase out most of its biomedical research using chimpanzees, which are humans' closest living relative and share 98 percent of the same genes.
Since 2013, no new applications for research using chimps have been approved, and last year, captive chimps were listed as endangered by the US Fish and Wildlife Service.
The NIH said the endangered designation requires researchers to obtain an extra permit for any experiments that could harm the animal, and that no such permits have been sought.
"As a result of these numerous changes over the last few years and the significantly reduced demand for chimpanzees in NIH-supported biomedical research, it is clear that we've reached a tipping point," NIH director Francis Collins said in a statement.
"In accordance with NIH's commitment in June 2013, I have reassessed the need to maintain chimpanzees for biomedical research and decided that effective immediately, NIH will no longer maintain a colony of 50 chimpanzees for future research."
The NIH-owned chimps are "now eligible for retirement" at the Federal Sanctuary System operated by Chimp Haven in Keithville, Louisiana, Collins said.
The NIH said it will continue to use other non-human primates for research.