There is a groundbreaking breakthrough in medicine that has renewed optimism in the fight for the thousands of people on the waiting list for a kidney transplant. Tim Andrews, a 66 year old American man suffering from end-stage kidney failure, had a pig’s kidney, genetically modified, working inside his body for 271 days. Andrews was transplanted with the uniquely modified kidney on 25 January 2025 at the Mass General Brigham in Boston. The kidney originated from a Yucatan miniature pig, which had been subject to significant gene editing using CRISPR by biotech company eGenesis.
Multiple genes contributing to human immune incompatibility were deleted as well as several human genes inserted to allow the organ to better match the recipient. Any viral producing sequences were also disabled. The kidney was fully functional within the first few minutes following transplantation.
Andrews enjoyed almost nine months free of dialysis burden. He felt positive because his doctor told him he was given a 9% chance of receiving a human kidney within 5 years. Frequent iron measurements and observation allowed physicians to modify immunosuppressive drug doses to ensure a positive outcome. Brown indicators of immune response were subdued. The kidney continued to perform the necessary function of filtering the bloods. By October 2025 the pig kidney was beginning to deteriorate as a consequence of microvascular inflammation and injury.
The surgeons took it out and Andrews reverted to dialysis for 82 days. By January 2026 he received a suitable human donor kidney allograft from a deceased donor. This second transplant was a success. Data later published in The Lancet, confirmed that the human organ was functioning well with no indication that the earlier pig kidney had sensitized Andrews’ immune system against human tissue.
This is a landmark case on many accounts: it is both the longest-lasting time that a person has lived without dialysis following a pig kidney transplant and the first ever case of a planned ‘bridging’ pig-to-human organ transplant. The team of scientists led by Dr Leonardo Riella and Dr Tatsuo Kawai stressed the importance of this achievement in context of the ongoing crisis of shortage of human organs: ‘this shortage remains a crisis. Many patients wait for years on the waiting list as their health declines during dialysis’.
Addressing this issue has been Xenotransplantation, a field long under investigation. Simple, otherwise unaltered or with minimal modification kept organs could only keep animals alive for days or weeks. This gene-edited kidney’s ability to put up months of reliable function indicates how much we have moved forward and such organs could avoid patients having to go through the physical effects of over long term dialysis, this way remaining fit for a future human transplant.
Andrews remains under close surveillance during his slow recovery process. The human kidney has demonstrated immediate and lasting functional capacity; tests have revealed no new antibody formation which might present future difficulties. The next difficulties, the team stresses, are fine-tuning the gene edits, enhancing the longevity of the kidney and screening a large group of patients for safety.