For the first time ever, a genetically engineered pig kidney has continued functioning over a month after being transplanted into a human patient, raising hopes that one day these organs can serve as an alternate, sustainable source for transplants.

Surgeons at NYU Langone transplanted the kidney on July 14 into a brain-dead, 57-year-old man whose family donated his body to science. It is the fifth xenotransplant performed by the health system and the longest successful one involving a kidney.

To avoid organ rejection, the surgical team negated the gene encoding alpha-gal, a biomolecule that instigates rapid-antibody-mediated rejection of pig organs in humans. They also placed the pig’s thymus gland underneath the kidney’s outer layer to prevent delayed immune responses. Whereas previous genetically engineered pig organ transplants required 10 genetic modifications, this procedure incorporated one.

“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,” said lead surgeon Dr. Robert Montgomery, chair of the department of surgery and director of the NYU Langone Transplant Institute, in a statement.

Montgomery and his colleagues removed both the man’s human kidneys to completely sustain him on the pig one, which began producing urine immediately without signs of rejection. They applied immunosuppression medications and performed enhanced screening for porcine cytomegalovirus (pCMV), which has been linked to organ failure, in the donor pig to ensure the transplant was safe to use.

The man, who is hooked up to a ventilator, undergoes weekly biopsies. Staff have reported optimal levels of creatinine, an indicator of kidney function, and found no signs of pCMV. They also survey for porcine endogenous retrovirus (PERV) and six other viruses.

The case is part of a larger study overseen by a specific research ethics oversight board at NYU Langone. Over 103,000 people in the U.S. require a transplant, and nearly 88,000 need a kidney, according to the Organ Procurement and Transplantation Network.

Earlier this year, the U.S government increased the number of eligible management competitors for the OPTN to reduce waiting times and associated deaths.

Montgomery performed the first transplant of a genetically modified pig kidney in 2021 and a similar procedure the same year. Two others with pig hearts were performed at the Transplant Institute in 2022. Additionally, surgeons at the University of Maryland in early 2022 transplanted a gene-edited pig heart into a man, who lived for two months.

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

The kidney and thymus gland came from a GalSafe pig, an animal engineered by Revivicor Inc., a subsidiary of United Therapeutics Corporation.

With permission from the family, ethics committee approval, and support from United Therapeutics, the study will continue into mid-September.

Montgomery says these findings and using a pig deemed safe by the FDA bring this research one step closer to being approved for a clinical trial phase.

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