Genetically Modified Pig Kidney Keeps Man Alive for Nine Months Before Human Transplant
A groundbreaking xenotransplantation case has shown that a gene-edited pig kidney can keep a patient with end-stage kidney disease off dialysis for 271 days, potentially opening a new path for people waiting for scarce human donor organs.
A genetically modified pig kidney has achieved a major milestone in transplant medicine after keeping a 66-year-old man alive without dialysis for nearly nine months before he successfully received a human kidney.
The patient, Tim Andrews, became the first known person to move from a genetically modified pig kidney to a human donor kidney. Doctors say the case provides early evidence that animal organs could one day serve as a temporary “bridge” for patients waiting for a human transplant.
The findings, published in The Lancet on September 3, 2026, mark an important step in the development of xenotransplantation—the transplantation of organs between different species.
Who Is Tim Andrews?
Andrews was 66 when he received the experimental pig kidney in January 2025. He had end-stage kidney disease associated with type 2 diabetes and faced extremely limited prospects of receiving a suitable human donor kidney.
Before the experimental transplant, his condition required regular dialysis, a treatment that performs some of the functions normally carried out by healthy kidneys.
Doctors at Massachusetts General Hospital believed a genetically engineered pig kidney could provide an alternative while Andrews waited for a human organ.
The kidney came from a genetically modified Yucatan miniature pig named Wilma. It was produced by eGenesis, a biotechnology company developing genetically engineered organs for human transplantation.
The Pig Kidney Worked for 271 Days
The experimental kidney immediately began functioning after transplantation.
Most significantly, Andrews did not require dialysis for 271 days, or approximately nine months.
During that period, the pig kidney produced urine and filtered waste from his bloodstream continuously, effectively performing the basic functions expected from a functioning kidney.
This represents the longest documented dialysis-free survival following a pig kidney xenotransplant in a living human at the time of the report.
The achievement was particularly significant because previous human pig-kidney transplants had lasted substantially shorter periods.
How Was the Pig Kidney Genetically Modified?
One of the biggest challenges in transplanting an animal organ into a human is the immune system.
The human body naturally recognizes foreign tissue as a threat and can attack a transplanted organ. Scientists have therefore been modifying pig genes to make the organs more compatible with humans.
The kidneys developed by eGenesis contain extensive genetic modifications designed to:
- Reduce the risk of immune rejection
- Add human genes that may improve compatibility
- Remove or disable pig genes associated with harmful immune responses
- Inactivate pig endogenous retroviruses that could potentially pose infection risks
The goal is to make the pig organ more biologically compatible with a human recipient while reducing the possibility of rejection or cross-species infection.
Why Did the Pig Kidney Eventually Fail?
The transplant was not a permanent success.
After approximately six months, doctors began seeing damage in the small blood vessels of the transplanted kidney. This developed into microvascular injury and inflammation, eventually causing the organ to fail.
The kidney was removed after 271 days.
Importantly, researchers did not find evidence that the failure was caused by transmission of a pig pathogen. An early episode of T-cell-mediated rejection was treated successfully, while later problems involved vascular injury and inflammation.
The failure nevertheless provides researchers with valuable information about what needs to be improved before xenotransplantation can become a widely available treatment.
A Human Kidney Came Next
The most remarkable part of Andrews’ case came after the pig kidney was removed.
In January 2026, Andrews received a kidney from a deceased human donor.
The human kidney began functioning immediately, and doctors reported no evidence that the previous pig-kidney transplant had caused sensitization that would interfere with the new organ.
This made Andrews the first known patient to successfully transition from a pig kidney transplant to a human kidney transplant.
Doctors describe this possibility as a “bridge” strategy.
Instead of replacing human transplantation entirely, a genetically modified animal kidney could potentially keep a patient alive and free from dialysis until a suitable human donor organ becomes available.
Why This Could Matter for the Global Organ Shortage
The breakthrough comes against the backdrop of a severe shortage of donor organs.
For patients with end-stage kidney disease, transplantation is generally considered the preferred long-term treatment when medically appropriate. But there are not enough human donor kidneys to meet demand.
This means many patients remain on waiting lists while continuing dialysis, with some dying before a suitable organ becomes available.
Harvard Medical School researchers say xenotransplantation could potentially help close this gap by providing an alternative source of organs.
The concept could eventually change the traditional transplant model:
Human donor available → transplant
could potentially become:
Gene-edited pig kidney → temporary support → human donor kidney
That would give critically ill patients more time while they wait for a compatible human organ.
Five Patients Have Received Gene-Edited Pig Kidneys
The Andrews case is part of a broader effort at Massachusetts General Hospital.
According to the Financial Times, five patients had received genetically engineered pig kidneys at the hospital since March 2024.
The kidneys were developed by eGenesis, with researchers modifying the organs to reduce immune rejection and viral risks. Three recipients, including Andrews, were reported to have lived with the organs for more than eight months.
Earlier attempts also demonstrated both the possibilities and limitations of the technology.
In 2024, the first living human recipient of a genetically engineered pig kidney survived for 52 days following transplantation. Researchers said his subsequent death was linked to cardiac causes rather than evidence that the pig kidney itself had caused his death.
The growing number of cases is giving scientists a much larger body of information about immune rejection, blood-vessel damage, infection risks and the genetic modifications needed to make animal organs work safely in humans.
Could Pig Kidneys Eventually Become Permanent Transplants?
That remains one of the biggest questions.
The Andrews case demonstrates that a gene-edited pig kidney can function for many months, but it does not yet establish that such an organ can safely work for years.
Researchers still need to determine how to prevent late-stage vascular damage, improve immunosuppressive treatments and establish long-term safety.
The immediate goal may therefore be more modest: using pig kidneys as temporary organs for patients who are unlikely to receive a human kidney quickly.
Researchers hope that continued improvements could eventually make xenotransplants suitable as a long-term alternative in their own right.
Clinical Trials Could Expand the Research
The field is now moving beyond isolated experimental cases.
The Financial Times reports that eGenesis plans to begin a larger trial involving 33 kidney patients across as many as 10 US transplant centres in early 2027, with the longer-term objective of pursuing regulatory approval.
Such trials will be crucial because individual cases cannot establish whether the technology is consistently safe and effective.
Researchers will need to monitor larger numbers of patients for:
- Long-term kidney function
- Immune rejection
- Blood-vessel complications
- Viral and other infectious risks
- Effects of immunosuppressive medicines
- Overall survival and quality of life
A Major Step, But Not Yet a Routine Treatment
The story of Tim Andrews represents a significant scientific milestone, but experts caution against viewing it as proof that pig kidneys are ready for routine transplantation.
Only a small number of patients have received these organs, and their outcomes have varied.
The technology still requires extensive clinical testing before genetically modified pig kidneys could become a standard treatment.
Nevertheless, Andrews’ experience has demonstrated something that researchers had previously been unable to show: a genetically modified pig kidney can keep a living human off dialysis for months and can successfully be followed by a human kidney transplant.
For millions of people affected by kidney failure and the shortage of donor organs, that could be one of the most important developments in transplantation medicine in years.
The Bigger Picture
The ultimate promise of xenotransplantation is not simply replacing a human kidney with a pig kidney.
It is about changing the economics and availability of organ transplantation.
If scientists can reliably produce genetically engineered organs that are compatible with humans, transplantation could eventually become less dependent on unpredictable donor availability.
Tim Andrews’ nine-month journey does not prove that future is here yet. But it provides some of the strongest evidence so far that genetically engineered animal organs may have a practical role in keeping patients alive while they wait for a human donor—and perhaps, one day, beyond that.