A pig kidney that had been working normally in a human body was removed after nine months. Although there had been no problems, it was removed recently as a safety measure after its function declined, offering hope that xenotransplantation using other animals could help solve the chronic shortage of organ donations.
Massachusetts General Hospital (MGH) under Harvard Medical School said on the 27th (local time), "Last week we removed a gene-edited pig kidney from the body of Tim Andrews, a 67-year-old man." The patient underwent a transplant at the hospital on Jan. 25. According to the hospital, kidney function gradually declined, and the organ was removed on the 23rd.
Andrews, who had undergone dialysis for more than two years due to kidney failure, received a pig kidney transplant and lived without dialysis for 271 days, the longest on record. He is the fourth patient in the United States to receive a gene-edited pig kidney transplant. The first two patients died shortly after transplantation, and the third patient had the kidney removed after 130 days due to immune rejection. Massachusetts General Hospital said, "Mr. Andrews has set a new benchmark in the field of xenotransplantation," adding, "Mr. Andrews will now resume dialysis and remain on the waiting list for a human kidney transplant."
◇An alternative to solve the shortage of donor organs
The world faces a chronic shortage of organs for transplantation. As populations age, the number of people waiting for organ transplants increases every year, but donations are far short. In the United States, more than 100,000 people are on the organ transplant waiting list, and about 90,000 of them are waiting for kidneys. Korea is no different. Last year there were 397 brain-dead organ donors, but 54,789 people were on the transplant waiting list. An average of 8.5 people die each day while waiting.
Scientists have looked to animals for answers to the chronic shortage of transplantable organs. The approach uses mini pigs whose organ structure and size are similar to humans. Pig organs can trigger immune rejection when placed in the human body. Scientists are addressing this with humanizing genetic modifications.
The kidney transplanted into Mr. Andrews came from a pig with 69 genes edited. Some of those edits were to neutralize viral genes that could pose a risk to humans, and others altered genes to make the organ more compatible with the human body, reducing the likelihood of immune rejection. CRISPR-Cas9, an enzyme complex that cuts only the desired genes in DNA, was used.
The pig organ transplanted into Mr. Andrews was provided by eGenesis, a biotech company in Cambridge, Massachusetts. The company was founded by George Church, a Harvard University professor and a leading authority in xenogeneic gene editing. The hospital said it plans to perform one more gene-edited pig kidney transplant by the end of this year.
◇Transplants extend to pig hearts, kidneys, lungs and livers
Xenotransplantation continues to show results. In China, a study found that a patient who received a pig liver survived for 171 days. While there have been cases of transplanting pig livers into brain-dead donors, this was the first time it was transplanted into a living person.
A joint research team from Anhui Medical University and Yunnan Agricultural University in China published on the 8th in the Journal of Hepatology the results of a study in which they transplanted a pig liver into a 71-year-old man with liver cancer.
The Chinese researchers also performed humanizing gene edits using CRISPR-Cas9 first. They harvested a liver from a humanized pig in which three genes that trigger immune rejection had been removed, then resected part of it, inserted seven proteins that regulate human immune response and blood coagulation, and attached it to the patient's liver. The researchers said, "Immediately upon receiving the patient's blood flow after transplantation, the liver turned to a normal color and began secreting bile."
For one month after transplantation, albumin and coagulation factors derived from the pig were detected in the blood, and the transplanted liver increased in volume and performed metabolic functions, secreting up to 400 mL of bile per day. However, on the 38th day after transplantation, a blood clot formed in the patient's microvessels, and as the decline in organ function persisted, the pig liver was removed.
In Aug., a world-first case showed that a gene-edited pig lung transplanted into a human maintained function for nine days. A research team led by He Jianxing at the First Affiliated Hospital of Guangzhou Medical University, together with researchers from Korea, Japan and the United States, transplanted the left lung of a gene-edited pig into a brain-dead donor and confirmed that it maintained function for nine days, as reported in Nature Medicine. From Korea, Professor Jeon Kyung-man of Samsung Medical Center participated.
In Jan. 2022, the University of Maryland School of Medicine transplanted a gene-edited pig heart into a human. The 57-year-old American man who underwent the procedure died of complications two months after surgery. The following year, a 58-year-old patient received another pig heart transplant but likewise died within six weeks due to immune rejection.
Xenotransplantation has not yet been proven completely safe. It has not reached the safety level of human organ transplantation, so it cannot fully solve the chronic shortage of transplantable organs. But pig organs can be used temporarily while people wait to receive organs from other humans. In other words, it could serve as a bridge to human organ transplants.
Korea is also pursuing xenotransplantation. The Ministry of Health and Welfare is conducting a national project worth 38 billion won, aiming to enter clinical trials for xenotransplantation within five years from 2023. Optipharm, a domestic company, is developing pigs with 10 genes edited. The company said it plans to submit an investigational new drug (IND) application to the Ministry of Food and Drug Safety for xenotransplantation, including pig islets, by next year.
References
Journal of Hepatology (2025), DOI: https://doi.org/10.1016/j.jhep.2025.08.044
Nature Medicine (2025), DOI: https://doi.org/10.1038/s41591-025-03861-x