• Posted October 13, 2023

Monkey Given Gene-Edited Pig Kidney Still Alive Two Years Later

Two years after a gene-edited pig kidney was transplanted into a monkey, researchers report the monkey is still alive.

"We're the only group in the field to comprehensively address safety and efficacy of our donor organ with these edits,"said study co-author Dr. Mike Curtis, president and CEO of eGenesis, a company working on innovation in the field of organ transplantation.

What researchers did was genetically modify Yucatan pigs to make it possible to transfer their kidneys to another species without rejection. The findings were published online Oct. 11 in the journal Nature.

The Yucatan pig was chosen because it weighs about 150 pounds, similar to an average woman, and has kidneys comparable in size to a human.

Organ transplant has always involved the recipient having to take drugs to suppress their immune system and prevent rejection.

In past pig-to-primate donations, scientists needed to use quantities of immunosuppressants too high to use in human donation.

For this trial, they instead were able to make effective enough genetic modifications and use a level of medication a human could tolerate.

One of the gene modifications knocked out part of the genes that make glycol antigens, structures made of sugar molecules that can trigger kidney rejection from the recipient, CNN reported.

Unlike in past research, in which the animals didn't live long, this time two additional gene edits were important to extending the monkeys' lives.

Scientists inserted seven human genes that regulate kidney rejection pathways in the second edit. They inactivated androgynous retroviruses, which are remnants of ancient but inactive viral infections in pigs.

Together, these gene edits and the immunosuppressive drugs supported long-term survival.

The pig kidneys, some without all of the gene edits, were transplanted into 20 monkeys.

The monkeys then lived for various lengths of time. They lived 50 days or fewer in those without the full edits. Among those who received the full edits, five lived for more than a year. One lived for two years.

A single donated kidney appeared to work as well as two natural kidneys, the researchers reported.

These aren't the first pig organs used in research meant to save humans.

Dr. Robert Montgomery, director of the NYU Langone Transplant Institute, told CNN that the new trial is "an important contribution showing improved survival of extensively gene-edited pig kidneys in nonhuman primates."

Montgomery led a team that transplanted a genetically modified pig kidney into a human in July. He wasn't involved in this kidney research.

In that case, doctors removed the organ after two months, as planned, but it functioned the entire time. It was the longest documented case of a transplant between two species of its kind, CNN reported.

The new study is good support for moving to human clinical trials "sooner rather than later,"Montgomery said, but he cautioned that there is some theoretical risk in introducing the "vast array of gene edits"that the authors did on the donor pigs.

"Unintended off-target effects of these edits and inconsistent levels of transgene expression between pigs will be difficult to assess and will present a burdensome regulatory challenge,"he told CNN.

Some moderate successes in transplants from animals to humans include a January 2022 case in which researchers at the University of Maryland transplanted a heart from a genetically modified pig into a man with terminal heart disease. The transplant went well, but he died two months later.

The procedure was repeated in another man in September. He is still alive, CNN reported.

More than 90,000 people in the United States are on a waiting list for a new kidney. About 13 people die each day while waiting for a kidney transplant. About 8% to 16% of people have kidney problems around the world, CNN reported.

More information

The U.S. Health Resources and Services Administration has more on organ donation.

SOURCE: CNN