Tim Andrews lived 271 days without dialysis after receiving a gene-edited pig kidney transplant, then went on to receive a human kidney. That sequence, reported by surgeons at Massachusetts General Hospital in The Lancet, is the first time a living person has moved from a pig kidney to a human kidney. For the field of porcine kidney xenotransplantation as a bridge to human transplant, it is a milestone for xenotransplantation kidney research, and in the same breath it remains a single case that does not prove the bridge strategy works generally or that it is available to anyone on the kidney transplant waiting list today.
A record bridge in one patient with end-stage kidney disease
Andrews had end-stage kidney disease, the stage at which the kidneys can no longer keep up and dialysis or transplant becomes necessary. He had a prolonged expected wait for a deceased-donor kidney and no suitable living donor. On January 25, 2025, at age 66, he received a genetically engineered pig kidney at Massachusetts General Hospital under an FDA Expanded Access Investigational New Drug application. Expanded Access is a pathway that lets a seriously ill patient receive an investigational treatment outside a trial when no comparable option exists.
The pig kidney worked right away. Andrews stayed off dialysis for 271 days, the longest dialysis-free survival yet reported after a pig kidney xenotransplant in a living person. Xenotransplantation simply means transplanting living cells, tissues, or organs from one species into another, in this case from pig to human.
In January, 2026, he received a deceased-donor human kidney. The hospital team reported immediate function of the human graft with no evidence of sensitization during follow-up. Sensitization means the immune system has built antibodies that would attack a new organ, so a finding of no sensitization mattered because one fear was that a pig organ might close the door to a later human organ. In this one patient, it did not, and that single observation, not a general rule, is the heart of the bridge claim.
Why the kidney transplant waiting list makes a bridge tempting
Most people on the US national transplant waiting list are waiting for a kidney. National waiting-list data put the total list at 109,817 people, with about 12 people dying each day while waiting, and a July 30, 2026 snapshot counted 95,492 people waiting for a kidney, about 85 percent of the list. Kidney transplants in 2025 totaled 27,574. The gap between need and supply is the reason researchers are testing whether a pig kidney could keep someone alive and off dialysis while waiting, yet none of those figures say anything about whether the bridge approach itself will succeed beyond this one patient.
Intelligent Living has tracked the science leading up to this point, from early genetically engineered pig kidneys tested in animals and brain-dead recipients to the ethical questions now that gene-edited pig organs are entering real-world clinical use. This case is the next step in that arc, a living recipient who actually crossed from pig organ to human organ, still only one person.
Inside the gene-edited pig kidney
The donor organ, designated EGEN-2784 and supplied by eGenesis, came from a Yucatan miniature pig and carried about 69 genomic edits. Plainly put, the edits had three jobs:
- Remove pig warning flags. Deletion of major glycan xenoantigens removed sugar molecules on pig cells that human immune systems attack on sight. Without this step, a process called hyperacute rejection can destroy the organ within minutes or hours.
- Add human camouflage. Insertion of seven human transgenes added human regulatory signals meant to calm complement and clotting pathways, the parts of immunity and blood chemistry that injure foreign tissue.
- Disable hidden pig viruses. Inactivation of porcine endogenous retroviruses, viral sequences embedded in pig DNA, was designed to reduce infection risk from pig to human.
What editing does not do is equally important. It does not make the organ human, it does not remove the need for strong immune-suppressing drugs, and it does not guarantee durability. Those limits showed up directly in this patient’s course, and they apply even more strongly to anyone imagining this as an available therapy.
Day 14 rejection, six stable months, then failure
The hospital team monitored kidney function, rejection, antibody development, and pig-to-human infection, including advanced sequencing to look for pig microbes. The published first-in-human report describes this sequence:
- Immediate function. The pig kidney began filtering blood right after transplant on January 25, 2025.
- Day 14 setback. A biopsy showed T-cell-mediated rejection, meaning the patient’s own T cells, the immune system’s attack coordinators, infiltrated the graft. Treatment resolved that episode.
- About six months of stability. Graft function held steady while immunosuppression stayed at full strength.
- Infection forced a tradeoff. When a bacterial infection developed, and it was not a pig-derived infection, doctors reduced immunosuppression to let the patient fight the infection. Lowering those drugs carries a known cost: the immune system can turn back toward the graft.
- Vessel injury and failure. Microvascular inflammation with endothelial injury appeared, injuring the tiny blood vessels inside the kidney, and progressed to thrombotic microangiopathy, clotting damage in those small vessels, despite a persistently negative donor-specific crossmatch. No pig pathogen transmission was detected. The graft failed and was removed at 271 days.
- Return to dialysis, then a human kidney. Andrews went back on dialysis for 82 days before the deceased-donor human transplant in January 2026, so the bridge carried him most, not all, of the way.
That failure mechanism is itself useful knowledge, and it is also a warning. Future work on dosing of immune suppression, additional genetic edits, and closer monitoring of vessel injury all flow from this one detailed failure, but one detailed failure cannot tell doctors how often the same sequence would recur.
Bridge versus destination, and living versus brain-dead research
Two distinctions keep this story honest.
Bridge versus destination. A bridge organ keeps a patient alive and off dialysis until a human organ arrives. A destination organ would be the final therapy, meant to last for years. Lead author Leonardo Riella framed the vision as bridge first and destination only later, if long-term safety and durability are ever established. This case tested only the bridge idea, and only once, and the bridge did not carry him continuously to the human organ, as the dialysis gap above shows.
Living recipients versus brain-dead models. Earlier milestones, including the widely reported NYU work in brain-dead recipients, showed a pig kidney could function in a human body for weeks. Those models cannot show dialysis independence over months, response to infection, or a later human transplant. This living-recipient case does, but again only in one person.
| Context | What it showed | What it did not show |
|---|---|---|
| Brain-dead recipient studies | Short-term function and surgical feasibility | Long survival, dialysis freedom, or later human transplant |
| Rick Slayman 2024, first living pig kidney recipient at Mass General | Pig kidney could work in a living patient; course ended at 52 days with death from cardiac causes unrelated to the graft | Durability beyond two months or any bridge onward |
| Tim Andrews 2025 to 2026 | 271 dialysis-free days, then a successful human transplant with no sensitization in this patient | That the next patient would have the same result |
What this one case proved, and what remains unproven
Proved in this patient: a gene-edited pig kidney can support a living person without dialysis for 271 days; an early rejection episode can be reversed; a later infection-driven reduction in immunosuppression can precede vessel injury and graft loss.
Unproven for the field: how often a pig kidney would last this long, which patients could qualify, what the right immune-suppression balance is during infection, whether vessel injury can be predicted or prevented, what long-term safety looks like, and whether any of this shortens waiting-list suffering at scale. The FDA xenotransplantation guidance still treats these procedures as closely monitored investigational work with donor screening, recipient follow-up, and safety reporting, not routine care.
Frequently Asked Questions
How long did the pig kidney last?
271 days without dialysis, from January 25, 2025 until removal. That is the longest such span reported in a living person, and it is still one measurement in one patient rather than an expected duration.
Did the pig kidney block the later human transplant?
In this case, no. The team reported no blocking sensitization and immediate human graft function. Whether that would hold for others is unknown.
Why did the pig kidney fail?
After about six months, infection led doctors to lower immunosuppression, and the graft then developed microvascular inflammation and clotting injury that progressed to organ failure. The published report ties the failure to that vessel-level injury rather than to pig infection, which was not detected.
Is a pig kidney bridge available now?
No. This was an Expanded Access case, the first recipient in a planned three-patient study, not an approved therapy or an open trial result. Patients on the waiting list cannot request this as care today.
How is this different from earlier pig kidney news?
Brain-dead recipient studies showed short-term function. The 2024 living-recipient case showed feasibility but ended at 52 days. This is the first living case to document months off dialysis followed by a human transplant, which is why it matters and why it still proves only possibility, not reliability.
Conclusion: a door opened, not a path proven
One man crossed from a pig kidney to a human kidney with 271 dialysis-free days in between, and that crossing leaves a detailed map of both promise and failure points for the scientists who follow. Holding both facts together is the only honest way to read it: a genuine first that could one day ease the wait for thousands, and a single experimental result that changes nothing about anyone’s options this week.
