Pig kidneys enter trials

A man named Tim Andrews lived 271 days with a pig's kidney inside him. It was edited in 69 places to keep his body from rejecting it, and for most of a year it worked — the longest any gene-edited pig kidney has lasted in a living person. Then it began to fail, the surgeons removed it, and within months a human donor kidney came through. The pig organ had been exactly what it was meant to be: a bridge.

Sixty-nine gene edits to one pig, and the longest a kidney from it has run is still under a year.

That story, and the surgeries that came before it, were compassionate-use cases — last resorts granted one patient at a time. What changed in late 2025 is the paperwork. The FDA cleared eGenesis in September and United Therapeutics' EXPAND trial began transplanting patients in November, the first formal, multi-patient studies of pig kidneys with enrollment criteria, controlled variables, and survival endpoints. EXPAND's opening cohort is six transplants across two hospitals; eGenesis's runs to roughly 33.

The number to hold onto is on the other side: about 90,000 Americans wait for a kidney, and some 800,000 are on dialysis. A herd of edited pigs is, in principle, an inexhaustible supply. The trials are small and the organs still fail, but a regulator only authorizes a numbered cohort once it judges the one-offs have shown enough — the moment a frontier procedure becomes a process you can actually measure.