A Pig Kidney Kept a Man Alive for 271 Days. Now the FDA Wants More.
A genetically engineered pig kidney kept a man off dialysis for 271 days, setting a new record for xenotransplantation. Now the FDA has cleared eGenesis to try it in 30 more patients, marking the biggest bet yet that pig organs could solve the kidney shortage crisis.
The Longest Nine Months in Transplant History
In January 2025, surgeons at Massachusetts General Hospital did something that would have sounded like science fiction a decade ago. They took a kidney from a genetically engineered pig and put it inside a man named Tim Andrews. He'd been stuck on dialysis for over two years, waiting for a human organ that might never come.
That pig kidney kept him off dialysis for 271 days. Nine months. Nearly three-quarters of a year with a functioning organ from another species. It's the longest a pig-to-human kidney transplant has ever worked in a living person.
And now the FDA wants eGenesis, the company behind the kidney, to do it again. Not once or twice, but in roughly 30 more patients through a formal clinical trial. This isn't compassionate use anymore. This is the real thing: a Phase 1/2/3 study designed to prove that pig kidneys can work as a genuine solution for people dying on transplant waitlists.
The Problem That Won't Go Away
Let's put some numbers around why this matters. Right now, roughly 94,000 Americans are waiting for a kidney transplant. That's not a typo. Kidneys account for about 86% of everyone on the national organ transplant waitlist.
In 2025, the U.S. performed about 27,573 kidney transplants. That sounds like a lot until you realize it's less than a third of the people waiting. The math is brutal: for every kidney that becomes available, nearly three people are left hoping for the next one.
About 12 people die every day waiting for a kidney in the United States. And here's the really grim part: 2025 was the first year this century where deceased donor kidney donations actually declined, dragging total transplant numbers down with them. The gap between supply and demand isn't shrinking. It's growing.
This is the crisis that xenotransplantation (transplanting organs across species) is trying to solve. If you could breed pigs specifically designed to grow kidneys for humans, you'd have an essentially unlimited supply of organs. The catch, of course, is making it work.
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69 Edits and a Prayer
The kidney inside Tim Andrews wasn't from any ordinary pig. eGenesis used CRISPR gene editing to make approximately 69 changes to the pig's genome. Think of it like rewriting a recipe: you're swapping out ingredients that would trigger the human immune system and adding ones that help the body accept the organ.
Those edits fall into three buckets. First, eGenesis knocked out three sugar molecules on pig cells that scream "foreign invader" to the human immune system (the biological equivalent of removing a neon "attack me" sign). Second, they inserted seven human genes to calm inflammation, regulate the immune response, and prevent blood clotting problems. Third, and perhaps most impressively, they inactivated all 59 copies of porcine endogenous retroviruses (PERVs), ancient viral DNA baked into the pig genome that could theoretically cause infections in humans.
That last part is what separates eGenesis from its main competitor, United Therapeutics, whose pig kidneys use about 10 gene edits. It's a fundamental philosophical split: eGenesis believes more editing means better outcomes, while United Therapeutics bets that fewer, more targeted changes are enough. Both approaches now have FDA-cleared clinical trials running simultaneously. The field is essentially running two parallel experiments to see which strategy wins.
What 271 Days Actually Looked Like
For most of those nine months, Andrews's pig kidney worked remarkably well. His metabolic filtration was near-normal. He had more energy. His quality of life improved. He was, by all meaningful measures, a person with a functioning kidney rather than a patient chained to a dialysis machine.
But the kidney didn't last forever. It gradually developed proteinuria (protein leaking into the urine, a sign of kidney damage) and progressive dysfunction. In October 2025, surgeons removed the pig kidney after 271 days.
What happened next, though, might be just as significant as the transplant itself. Andrews went back on dialysis briefly, and then in January 2026 received a human kidney transplant. He became the first person in history to be successfully bridged from a pig organ to a human one. That's a concept transplant doctors have been dreaming about for years: using a xenograft to keep someone alive and healthy long enough for a conventional organ to become available.
From Experiment to Expansion
The 271-day case was part of a tiny expanded-access program at MGH; only three patients were treated in total. But the results were convincing enough for the FDA to take a major step forward.
eGenesis received IND (Investigational New Drug) clearance for EGEN-2784, their gene-edited pig kidney product, in September 2025. The trial is designed as a seamless Phase 1/2/3 study, meaning it can progress from early safety evaluation all the way to the data needed for commercial approval without stopping to redesign between phases.
The key details: patients must be 50 or older, on dialysis, and actively on the kidney transplant waitlist. The primary evaluation happens at 24 weeks (about six months) after transplant, measuring safety, kidney survival, and renal function. But recipients will be monitored for life, because when you're putting pig organs in humans, you want to know what happens in year five, year ten, and beyond.
eGenesis plans to treat about 33 patients over roughly 2.5 years, spacing out the transplants so doctors can review safety data between procedures. It's careful, methodical, and exactly the kind of stepwise approach regulators want to see when the science is this new.
The Race Is On
eGenesis isn't alone in this space. United Therapeutics and its subsidiary Revivicor launched their own FDA-cleared pig kidney trial (called EXPAND) with plans to enroll up to 50 patients at multiple centers. Their UKidney product uses a different, less extensively edited pig, creating a natural experiment in competing genetic engineering strategies.
Meanwhile, Makana Therapeutics is carving out a niche in pig liver xenotransplantation, targeting a different organ but the same underlying crisis of shortage.
The infrastructure buildout tells you how seriously these companies are taking the opportunity. eGenesis is preparing two facilities capable of producing about 1,000 donor pigs per year and is investing $200 million in breeding centers across Texas and Minnesota. United Therapeutics has a $75 million facility in Virginia. These aren't pilot projects. They're industrial-scale operations betting that xenotransplantation will become a routine part of medicine.
The Uncomfortable Questions
For all the optimism, transplant experts are keeping their enthusiasm in check. The 271-day kidney ultimately failed. The rejection patterns in pig-to-human transplants look different from those in human-to-human transplants, with more antibody-mediated rejection and clotting problems that doctors are still learning to manage.
There are also ethical questions that don't have easy answers. These early trials are enrolling some of the most vulnerable patients in medicine: older people on dialysis with limited options. The informed consent conversations must be extraordinarily nuanced, balancing genuine hope against experimental uncertainty.
And then there's the access question. Even if pig kidneys work brilliantly in clinical trials, who gets them first? At what cost? Will insurance cover a $200,000 pig organ transplant (hypothetically) when the patient might need another one in a year? These conversations are already beginning in transplant policy circles, because the timeline from "interesting experiment" to "real clinical option" is shrinking fast.
Why This Moment Feels Different
Xenotransplantation has been "five years away" for about forty years. So why should anyone believe this time is different?
Because the data are different. eGenesis's preclinical work in monkeys showed median survival of 176 days, with at least one animal surviving over two years (758 days) with a pig kidney. The human results are now tracking in the same ballpark. And critically, the FDA isn't just allowing one-off compassionate cases anymore; it's clearing structured, multi-patient clinical trials designed to support eventual commercial approval.
The organ shortage kills roughly 5,600 Americans every year on the transplant waitlist alone. That number has been climbing for decades, and conventional solutions (more organ donors, better preservation technology, policy reforms) haven't been enough to close the gap. Modeling studies suggest that even a modest 10% expansion of the kidney waitlist would require about 2,800 additional kidneys that simply don't exist in the human donor pool.
Pig kidneys might not be the answer for every patient. But 271 days of dialysis-free life, from an organ grown in a genetically engineered pig, is no longer a proof of concept. It's a proof of possibility. And with 30 more patients about to find out whether that possibility holds up, the next chapter of this story will be written in hospital rooms, not just laboratories.
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