A U.S. man is still alive more than six months after receiving a kidney from a genetically modified pig — the longest survival yet recorded for a pig organ implanted in a living person. Researchers say the outcome represents a landmark in xenotransplantation, the experimental practice of transplanting organs from animals into humans. The recipient, Tim Andrews, 67, had end?stage kidney disease and had been on dialysis for more than two years before undergoing the operation in January. Since receiving the pig kidney, Andrews has been dialysis?free. He was one of three patients who received genetically modified pig kidneys supplied by biotechnology company eGenesis of Cambridge, Massachusetts; the procedures were performed on compassionate grounds for patients with no viable alternatives. “Reaching six months’ survival is an amazing feat,” said Wayne Hawthorne, a transplant surgeon at the University of Sydney. He noted that the first six months after transplant are the period of highest risk for both the patient and the graft, when complications such as anemia and immune rejection are most likely to emerge. “The six?month time point marks that things have gone extremely well,” Hawthorne said, adding that reaching 12 months would be another important milestone and “a fantastic long?term outcome.” The previous record for the longest?surviving genetically modified pig organ in a human was held by Towana Looney, a 53?year?old U.S. woman whose transplanted pig kidney functioned for four months and nine days before being removed due to emerging immune rejection. Managing immune rejection remains a central challenge, doctors say. The pig kidney used in Andrews’s case carried 69 genomic edits; Looney’s had fewer. All of the modified organs had certain pig genes removed and human genes inserted in an effort to make the tissue more compatible with the human immune system. Researchers do not yet know precisely how many edits are necessary to optimize compatibility and minimize rejection risk. Patients in these trials receive immunosuppressive medications and are monitored closely with wearable remote devices that allow clinicians to track vital signs and organ performance between clinic visits. Physicians are still determining the optimal regimes of drugs and the intensity of monitoring required to balance suppression of rejection against the risks of infection and other side effects. Andrews and his medical team understand that the pig kidney may not be a permanent solution. He remains on the waiting list for a human donor. If the pig kidney can safely function as a bridge — keeping him healthy enough while he waits for a human transplant — that would mark a significant clinical advance.(SD-Agencies) | 