A genetically engineered pig kidney transplanted into a man declared brain-dead continued to “function well” after 32 days, US surgeons who carried out the procedure have said.

This represents the longest period that a gene-edited pig kidney has functioned in a human.

Surgeons at New York University (NYU) Langone Health said that this is the latest step towards “the advent of an alternate, sustainable supply of organs for transplant”.

The procedure, performed on July 14, 2023, was the fifth xenotransplant, where non-human tissues are transplanted into humans, to be performed at the New York facility.

Observation is ongoing, and the study will continue through mid-September 2023.

The research, which study leaders say could save many lives in the future, was made possible by the family of the 57-year-old male who had elected to donate his body to science.

Pig kidney

“This work demonstrates a pig kidney – with only one genetic modification and without experimental medications or devices – can replace the function of a human kidney for at least 32 days without being rejected,” Dr. Robert Montgomery, surgeon and director of the NYU Langone Transplant Institute, said.

Dr. Montgomery performed the world’s first genetically modified pig kidney transplant into a human on September 25, 2021.

The first hurdle to overcome in xenotransplants is preventing the human body rejecting the animal organ when it is connected to the circulatory system.

This study involved “knocking out” a gene which has been identified as being responsible for a rapid rejection of pig organs by humans.

The pig’s thymus gland, which is responsible for educating the immune system, was also embedded underneath the outer layer of the kidney to prevent delayed immune responses.

Both of the transplant recipients’ native kidneys were surgically removed. One pig kidney was then transplanted and started producing urine immediately without any signs of rejection.

Levels of creatinine, a bodily waste product found in the blood and an indicator of kidney function, were in the optimal range during the length of the study, and there was no evidence on biopsy of rejection.

While previous genetically engineered pig-organ transplants have incorporated up to 10 genetic modifications, this latest study shows that a single-gene knockout pig kidney can still perform optimally for at least 32 days without rejection.

“We’ve now gathered more evidence to show that, at least in kidneys, just eliminating the gene that triggers a hyperacute rejection may be enough along with clinically approved immunosuppressive drugs to successfully manage the transplant in a human for optimal performance – potentially in the long-term,” Dr. Montgomery said.


In the US, there are more than 103,000 people on the waiting list for transplant, with nearly 88,000 of those waiting for a kidney, according to recent official data.

In 2022, about 26,000 people received a kidney transplant. Nearly 808,000 people in the US have end-stage kidney disease.

“There are simply not enough organs available for everyone who needs one.

“Too many people are dying because of the lack of available organs, and I strongly believe xenotransplantation is a viable way to change that,” Dr. Montgomery said.

Monitoring of the pig kidney recipient will continue for another month with permission from the family.