A 67-year-old man lived nine months on a gene-edited pig kidney before it was removed, and eGenesis just got FDA approval to take the technology much further. Nearly 100,000 Americans on the kidney waitlist are watching closely.
A Kidney From a Different Species
Tim Andrews spent more than two years tethered to a dialysis machine. Three times a week, every week, for hours at a stretch. Then, on January 25, 2025, surgeons at Massachusetts General Hospital gave him a kidney from a pig.
Not just any pig. A pig with 69 genetic modifications, engineered by a company called eGenesis to make its organs compatible with the human body. And for 271 days, that kidney worked. Andrews went home, resumed normal activities, and described feeling "re-energized and revitalized." The cloud of dialysis, he said, had disappeared.
The kidney was eventually removed on October 23, 2025, after signs of chronic rejection set in. Andrews went back on dialysis, and he survived the procedure. But here's what matters: for nine months, a pig organ kept a living human off dialysis. That's the longest a gene-edited pig kidney has ever functioned inside a person.
Now eGenesis is pressing the accelerator. The FDA just greenlit an expanded clinical trial, and the company isn't the only one racing toward a future where pig organs could solve one of medicine's most stubborn problems.
Why Nine Months Changes Everything
To understand why 271 days is such a big deal, you need to understand how badly the organ transplant system is broken.
About 90,000 people sit on the U.S. kidney transplant waitlist right now. Last year, only around 28,000 kidney transplants were performed. That means roughly two-thirds of the people waiting didn't get one. The average wait stretches three to five years; in some regions, it's closer to ten.
And here's the grim math: approximately 13 people die every day while waiting for a kidney in the U.S.
The deceased donation system simply can't close that gap. Only about 1% of deaths occur under conditions that allow organ recovery. Even if the system ran perfectly, experts estimate it might yield only around 2,000 additional kidneys per year. The shortfall is structural.
So: what if you could grow kidneys in pigs instead?
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69 Edits and a Lot of CRISPR
Making a pig kidney work inside a human body is like trying to install a Mac operating system on a Windows computer. The hardware sort of fits, but the software screams at you.
The human immune system treats pig tissue like an invader. It attacks immediately and aggressively, a process called hyperacute rejection. Pig cells also carry viruses baked into their DNA (porcine endogenous retroviruses, or PERVs) that could theoretically jump to humans.
eGenesis tackled both problems with multiplex CRISPR editing, making dozens of changes to the pig genome simultaneously. Their edits fall into three buckets:
Removing the "attack me" signs. Three key pig genes (GGTA1, CMAH, and B4GALNT2) produce sugar molecules on cell surfaces that human antibodies recognize as foreign. Knocking out all three dramatically reduces the immune system's initial assault.
Disarming the embedded viruses. eGenesis used CRISPR to disable up to 59 copies of PERV sequences scattered across the pig genome. The result: pigs that are functionally virus-free, with over a 1,000-fold reduction in viral transmission risk.
Adding human camouflage. The company inserted multiple human genes for complement regulation, blood clotting control, and immune modulation. Think of it as dressing the pig kidney in a human disguise so the body's defenses are less likely to sound the alarm.
The final product, called EGEN-2784, comes from pigs carrying all 69 of these modifications. The organs are grown in designated pathogen-free facilities, then transplanted using conventional surgical techniques.
What the Doctors Learned (and What Still Went Wrong)
Andrews' case wasn't just a survival milestone. It was a crash course in how the human body responds to a xenograft (a transplant from another species) over months, not just days.
The kidney worked immediately after surgery. No delayed function, no need for post-operative dialysis. Andrews was discharged in February 2025 and went home.
His immune system, though, never fully accepted the organ. The adaptive immune system (T cells and B cells) stayed relatively quiet.
But the innate immune system told a different story. Monocytes and macrophages stayed chronically activated, pumping out inflammatory signals like IL-1β and GM-CSF. Over time, this persistent inflammation contributed to chronic antibody-mediated rejection.
One bright spot: doctors tracked pig donor-derived cell-free DNA (fragments of pig DNA circulating in Andrews' blood) and found it spiked during rejection episodes. This could become an early warning system for future patients, catching problems before kidney function visibly declines.
A Second Patient Is Still Going
Andrews wasn't the only one. Bill Stewart, 54, received an EGEN-2784 kidney on June 14, 2025, at the same hospital. He was discharged a week later and, as of the latest reports, remains off dialysis.
Stewart's case is still relatively early. But every additional month his kidney functions adds confidence to the data. eGenesis' expanded access program was approved for three patients total; details on the third have not been publicly disclosed.
The company's first-ever human recipient, Rick Slayman, received a gene-edited pig kidney in March 2024. His kidney functioned well enough for him to go home, but he later died from an unrelated cardiac event. His case, though short, provided crucial early safety data that helped pave the way for everything that followed.
The FDA Just Opened the Door Wider
Building on these results, eGenesis secured FDA clearance for a Phase 1/2/3 clinical trial of EGEN-2784 in patients with end-stage kidney disease. The trial is designed to enroll 33 patients total: three sentinel patients first (with a 12-week observation window between each), followed by 30 more.
The primary endpoint: safety and kidney function at 24 weeks post-transplant. Patients must be 50 or older, on dialysis, and on the kidney transplant waitlist with a low probability of receiving a human organ within five years. Lifelong monitoring for infections and graft performance is built into the protocol.
This isn't just an academic exercise. The trial structure ("Phase 1/2/3" combined) is designed to potentially support a full approval application if results hold up. Massachusetts General Hospital is the lead site.
The Competition Is Heating Up
eGenesis isn't alone in this race. United Therapeutics is arguably further ahead on the regulatory front, with its own FDA-cleared xenokidney trial (called EXPAND) already enrolling patients and a recently cleared xenoheart trial (EXPRESS). Their first UKidney transplant was performed at NYU Langone in late 2025.
Other players like Makana Therapeutics and New Zealand-based NZeno are developing their own gene-edited pig platforms, but neither has reached human trials yet. For now, the xenotransplantation field is essentially a two-horse race between eGenesis and United Therapeutics, with academic medical centers serving as critical partners for both.
The Bigger Picture
Let's zoom out. A year ago, the idea of a pig kidney keeping a human alive for nine months would have sounded like science fiction. Now it's a data point in an FDA-reviewed clinical program.
The technology isn't perfect. Chronic rejection remains the enemy, and the immunosuppression regimens are heavy. But 271 days of dialysis-free life for a patient who had no other options? That's not a footnote. That's a proof of concept that could eventually reshape transplant medicine for the nearly 100,000 Americans stuck on a waitlist with no good alternatives.
The pig kidney era isn't coming. It's already here.
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