Xenotransplantation

Xenotransplantation is transplanting organs across species — in current practice, kidneys (and hearts) from pigs whose genomes have been edited with CRISPR to remove the antigens that trigger immediate rejection and to add human-compatible genes. The driver is organ shortage: "the greatest crisis we have right now in transplantation" (Leonardo Riella, MGH).

Two roles

1. Destination therapy — the pig organ is the patient's long-term organ. Every case before 2025 was this: a last resort for patients ineligible for a human organ.
2. Bridge to allotransplantation — the pig organ keeps the patient alive and off dialysis until a human organ is available. First done, and first described in The Lancet, with the Tim Andrews case (MGH, 2025–26).

The Andrews case (n=1)

• 66-year-old man with end-stage renal failure deteriorating on dialysis; eGenesis gene-edited pig kidney transplanted January 2025 under FDA Expanded Access.
• Immediate function; 271 days dialysis-free, the longest reported at the time (MGH's 2024 case: 52 days, death from unrelated cardiac causes).
• Failure path: infection → immunosuppression reduced at ~6 months → microvascular injury and inflammation → graft failure. An earlier T-cell-mediated rejection episode had been treated successfully. No pig pathogens transmitted.
• Human kidney, January 2026: immediate function and no sensitisation detected — the result the bridge concept depends on, since the worry is that a pig organ primes the immune system against a later human one.

What is not yet shown

• Graft durability beyond ~9 months; the microvascular-injury failure mode is unsolved and bears on immunosuppression protocols, donor gene edits and monitoring.
• Generalisation: one patient, one centre, industry-funded (MGH + eGenesis; multiple author ties to eGenesis).
• Cost and the regulatory path from Expanded Access to formal trials.

Related

• A Transplanted Pig Kidney Buys Time for a Human One (Economist) — source article (2026-09-12, lede-only capture, supplemented by the MGB release).
• Edible Medical Sensors (Economist) — the other device/medicine frontier in the Medicine & prevention topic.