A Gene-Edited Pig Kidney Bridged One Man to a Human Transplant

Tim Andrews’ case changed the practical question around pig-to-human kidney transplantation. Rather than simply asking whether a gene-edited pig kidney can work in a person, it showed that one can provide months free from dialysis and still be followed by a conventional human kidney transplant.

Andrews received an eGenesis EGEN-2784 pig kidney at Massachusetts General Hospital on January 25, 2025. The organ functioned for 271 days without dialysis before it was removed; he later received a deceased-donor human kidney. Reports describe this as the first documented transition from a pig-kidney xenotransplant to a human donor kidney transplant. 34

Why the pig kidney worked initially

EGEN-2784 was engineered with 69 genomic edits intended to make a pig organ more compatible with the human immune and circulatory systems. The changes include three deleted pig glycan antigens, seven inserted human transgenes, and inactivation of porcine endogenous retroviruses. 1

The broad goal is to reduce the immediate immune and clotting problems that can destroy an animal organ after transplantation into a human. Andrews also received immunosuppressive therapy, which remains necessary to help prevent the recipient’s immune system from attacking the graft. 3

The outcome matters because the kidney did more than survive surgery: it supported Andrews without dialysis for nearly nine months. At the time, 271 days was the reported record for dialysis-free survival with a genetically engineered pig kidney. 312

Why the graft ultimately failed

The result was not a permanent cure. After Andrews developed an infection, clinicians reduced his immunosuppression. The graft subsequently developed inflammatory injury and microvascular clotting and had to be removed. 3

That sequence illustrates the central clinical trade-off in xenotransplantation. Strong immunosuppression can help protect a transplant, but it can also make infections harder to manage. Reducing those drugs may be necessary during infection, yet can leave the graft more vulnerable to immune-mediated injury. Clotting abnormalities and longer-term graft durability remain major challenges as well. 3

Why the later human transplant is the milestone

A major concern has been whether exposure to a pig organ might sensitize a recipient’s immune system in a way that makes a later human transplant harder. Andrews’ successful deceased-donor kidney transplant indicates that a pig kidney did not prevent that next step in his case. 417

That does not settle the question for every patient. One case cannot establish the frequency of sensitization or the long-term safety of the strategy. But it provides a meaningful clinical proof of concept: a xenograft may be able to serve as a temporary bridge rather than closing the door on a standard donor kidney.

What the broader Massachusetts General Brigham experience suggests

The evidence remains early, involving a small number of highly selected recipients in expanded-access settings. Still, the direction of travel is encouraging. eGenesis has reported that three recipients had sustained kidney function for more than eight months without dialysis, and that two recipients had transitioned to human donor kidneys. 8

Separately, a woman treated at Massachusetts General Hospital had reached 285 days with a functioning pig kidney, surpassing Andrews’ previous 271-day record at the time of reporting. 7

These outcomes show that months of kidney function are increasingly achievable. They do not yet establish multi-year graft survival, a favorable risk-benefit profile compared with human transplantation, or broad eligibility for people with kidney failure.

The most plausible near-term use: a bridge to transplant

Based on the available cases, the strongest near-term role for gene-edited pig kidneys is as a bridge: providing kidney function and time away from dialysis for people awaiting a human donor organ or lacking other viable options. Andrews’ course is the clearest example so far of that model working end to end. 417

For pig kidneys to become a more durable alternative to human organs, larger studies will need to show reproducible function over much longer periods while controlling rejection, infection, clotting and potential zoonotic risks. The current cases are promising clinical signals, not conclusive evidence of a permanent replacement therapy. 13

The FDA-cleared RESTORE trial

The next test is a formal clinical study. FDA has cleared eGenesis to conduct RESTORE, a combined Phase 1/2/3 trial of EGEN-2784 in 33 people with kidney failure who are 50 to 70 years old, dialysis-dependent and waitlisted for a human kidney. The company expects the trial to begin in the first quarter of 2027 and plans to assess safety, tolerability and efficacy, including kidney function at 24 weeks after transplant.

That trial will be far more informative than individual landmark cases. Until those data arrive, Andrews’ experience is best understood as a breakthrough in bridging to transplant—and a clear reminder that the biological and clinical obstacles to long-lasting xenotransplantation are still substantial.