In the long human struggle against organ scarcity, a 66-year-old man named Tim Andrews has quietly marked a new threshold — nine months of life freed from dialysis, sustained by a kidney borrowed from a genetically rewritten pig. His case, unfolding at Massachusetts General Hospital through early 2025, does not announce a cure so much as it illuminates a path: that the gap between a failing body and a life-saving transplant might, for some, be bridged by biology we are only beginning to understand. The organ eventually failed, as the body's ancient defenses reasserted themselves, but not befor
Genetically Modified Pig Kidney Extends Dialysis-Free Survival to Nine Months
Tim Andrews spent over two years on dialysis before the experimental transplant, experiencing significant strain on his daily life from the treatment regimen.
A kidney that could work for months changes the calculus entirely.
Mark
So Andrews got a pig kidney and it worked for nine months. That's the headline. But what actually changed for him during those nine months?
Mimi
He stopped dialysis. That sounds simple, but for someone who'd been on it for more than two years, it meant getting his time back. Dialysis consumes hours—multiple sessions a week, every week. He could live differently for those nine months.
Luke
But we should be clear: the kidney eventually failed. The blood vessels were damaged. So it wasn't a permanent solution for him—it was a bridge.
Mimi
Right. But that's actually the point. The pig kidney didn't need to be permanent. It kept him stable long enough that a human kidney became available. That's a different way of thinking about xenotransplantation than we usually hear.
Mark
Why did they choose a pig? Why not some other animal?
Mimi
Size and function, mainly. Pig organs are similar enough to human organs that transplantation is biologically plausible. And they're easier to breed and modify than larger animals would be.
Luke
And they made 69 genetic edits to this particular pig. That's a lot of engineering. We should note that this is still experimental—it happened under FDA expanded access, which is for patients with serious conditions and no other options.
Mark
What happens now? Does this mean pig kidneys are ready for widespread use?
Mimi
No. This is one case. Researchers learned that a genetically modified pig organ can function in a human body for much longer than previous attempts. But they still need to solve the longer-term problems—immune rejection, blood-vessel damage, complications we haven't even encountered yet.
Luke
And the organ shortage is real. There are far more people who need kidneys than there are human donors. So the pressure to make this work is enormous. But that pressure doesn't change the fact that we're still in early stages.
Mark
What's the next step?
Mimi
Each patient teaches them something. Andrews' case shows that nine months is possible. The question now is how to extend that, and eventually how to make it reliable enough that it could help thousands of people waiting for transplants.
Luke
And whether the complications they saw in Andrews—the blood-vessel damage—are inevitable or preventable. That's the real unknown.
Der Puls
- Tens of thousands of patients languish on kidney transplant lists while the supply of human donor organs falls critically short, leaving many to deteriorate on dialysis for years with no guarantee a match will ever come.
- Tim Andrews, blood type O and facing a particularly narrow pool of compatible donors, had already spent more than two years tethered to a dialysis machine when researchers offered him an organ from a pig whose genome had been edited 69 times to suppress rejection.
- The transplanted kidney worked — immediately and remarkably — granting Andrews nine months free of dialysis before immune-driven blood-vessel damage forced its removal after 271 days, the longest any living person had carried such an organ.
- The case reframes xenotransplantation's purpose: rather than a permanent fix, a genetically modified pig kidney may serve as a vital bridge, keeping patients stable and alive long enough for a human donor organ to become available.
- Researchers now face the harder problem — understanding and preventing the immune and vascular damage that ends these transplants prematurely — before the approach can move from rare experimental procedure to a meaningful clinical tool.
In the long human struggle against organ scarcity, a 66-year-old man named Tim Andrews has quietly marked a new threshold — nine months of life freed from dialysis, sustained by a kidney borrowed from a genetically rewritten pig. His case, unfolding at Massachusetts General Hospital through early 2025, does not announce a cure so much as it illuminates a path: that the gap between a failing body and a life-saving transplant might, for some, be bridged by biology we are only beginning to understand. The organ eventually failed, as the body's ancient defenses reasserted themselves, but not before a human donor kidney arrived — and with it, a second chance that the pig kidney had helped make possible.
Tim Andrews had spent more than two years bound to a dialysis machine when Massachusetts General Hospital offered him an experimental path forward. His kidneys had failed entirely, and his O blood type narrowed an already scarce pool of compatible human donors. In January 2025, surgeons transplanted a kidney from a genetically modified pig — an organ whose genome had been rewritten 69 times to remove triggers of human immune rejection, introduce human-compatible genes, and neutralize pig retroviruses.
The kidney worked from the start. Andrews stopped dialysis, and what followed was not just a medical reprieve but a reclamation of daily life. By July 2025, he had already outlasted every previous recipient of a genetically modified pig kidney, surpassing the 137-day record. Each additional week offered researchers new data on how such organs behave inside a living human body.
Around the six-month mark, doctors detected deterioration in the kidney's blood vessels. The damage progressed, and after 271 days the organ was removed. Andrews returned to dialysis — but only briefly. A human donor kidney became available, and he received it in a conventional transplant, the outcome his care team had always hoped for.
His journey quietly reframes what xenotransplantation might be for. The field has long been imagined as a last resort for patients who will never find a human donor. Andrews' case suggests a different role: a genetically modified pig kidney could serve as a bridge, keeping patients stable and alive while they wait on transplant lists — buying time that dialysis alone cannot always preserve.
The nine-month milestone is meaningful, but the obstacles ahead remain formidable. Immune rejection, blood-vessel damage, and other long-term complications are not yet solved. Each patient who receives such a transplant gives scientists another chance to understand what must change before pig kidneys can reliably extend that window — and perhaps, one day, close it entirely.
Tim Andrews spent more than two years tethered to a dialysis machine, watching his life compress into the rhythm of treatment sessions. His kidneys had failed completely, no longer able to filter waste and excess fluid from his blood. At 66, with an O blood type that made finding a compatible human donor kidney harder, he faced an uncertain wait—one that could stretch for years, or might never end at all. In January 2025, Massachusetts General Hospital offered him something unprecedented: a kidney from a genetically modified pig.
The organ came from an animal whose genome had been rewritten 69 times over. Scientists had removed genes designed to trigger the human immune system's rejection response and inserted human genes to help the organ function in its new host. They had also inactivated pig retroviruses to prevent infection. This approach, called xenotransplantation, attempts to bridge a fundamental biological gap: the human body's instinct to attack anything it recognizes as foreign. A pig kidney cannot simply be placed inside a person and expected to work. It requires both genetic engineering and powerful immune-suppressing drugs to have any chance at all.
After surgery, the kidney began filtering Andrews' blood immediately. He stopped dialysis. For someone who had spent years attached to a machine for hours at a time, the shift was not merely medical—it was a reclamation of time, energy, and the texture of daily life. By July 2025, he had already become the longest-living recipient of a genetically modified pig kidney, surpassing the 137-day mark. The previous attempts had lasted far shorter periods. Researchers were learning something new with each passing week.
But around six months after transplantation, doctors detected damage to the kidney's blood vessels. The deterioration continued. After 271 days—nine months—the organ could no longer function adequately, and surgeons removed it. Andrews returned to dialysis. Yet the timing of what happened next made his case singular: a human donor kidney became available. He received it in a conventional transplant, the outcome doctors had always hoped for.
His journey reveals a possibility that xenotransplantation researchers had not emphasized before. The field is often framed as a solution for patients who cannot find human donors at all. But Andrews' experience suggests another role: a genetically modified animal kidney could keep patients stable while they wait on transplant lists, buying time that might otherwise be consumed by years of dialysis or lost entirely to illness. The pig kidney did not need to function for the rest of his life. It needed to function long enough.
The shortage of donor organs remains one of transplantation's most intractable problems. Far more people need kidneys than suitable human organs exist. Some patients spend years on dialysis; others become too sick to receive a transplant before one becomes available. Pigs are being studied because their organs are similar enough to human organs in size and function to make the biology plausible. Genetic engineering can alter the differences that cause rejection. Massachusetts General performed the world's first genetically edited pig kidney transplant into a living human in 2024. Andrews' procedure was the hospital's second.
The nine-month record is a milestone, not a solution. Andrews received his transplant under the FDA's expanded-access pathway, reserved for patients with serious conditions and limited alternatives. Researchers still do not know how to prevent immune reactions, blood-vessel damage, and other complications over much longer periods. A pig kidney that functions for days or weeks offers limited help to someone facing years of kidney failure. One that can work for months changes the calculus. Each patient gives scientists another opportunity to understand why some pig organs survive longer than others and what must change before the approach could be used widely. The next challenge is making that performance last.
Bemerkenswerte Zitate
For someone who has spent years attached to a dialysis machine, being able to live without regular treatment can change how much time and energy is consumed by kidney failure.— Medical reporting on Andrews' experience
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