Key Takeaways
- Pig organ transplants have reached record survival times in human patients
- FDA has approved full-scale clinical trials for genetically modified pig kidneys
- Gene editing technology CRISPR is enabling major advances in xenotransplantation
- Multiple companies are developing different approaches to overcome organ rejection
Genetically modified pig organs are moving from experimental procedures to regulated clinical trials, offering hope for solving the global organ shortage crisis. Recent breakthroughs include a record 271-day survival of a pig kidney in a human patient and FDA approvals for large-scale testing.
The Promise of Pig Organs
The global organ shortage claims countless lives daily. According to the Global Observatory on Donation and Transplantation, less than 10% of people worldwide who need transplants receive them. In America alone, approximately 13 people die each day while on waiting lists.
Pigs present an ideal solution as donor animals. They breed easily, have appropriately sized organs, and share enough physiological similarities with humans while avoiding the ethical concerns of using primates.
CRISPR Breakthroughs
Recent progress stems largely from CRISPR gene-editing technology, which earned its pioneers a Nobel Prize in 2020. This technology allows scientists to modify pig genomes to make porcine organs more compatible with human recipients.
The primary challenge remains organ rejection, where the immune system attacks foreign tissue. While human-to-human transplants require lifelong immunosuppressant drugs, cross-species transplants face even greater rejection risks.
How Gene-Edited Pigs Are Created
Companies like eGenesis, Revivicor, and ClonOrgan follow similar processes:
- Scientists take skin cells from adult pigs
- Disable 3-4 genes causing immune reactions in humans
- Insert 6-7 human genes to prevent rejection, blood clotting, and inflammation issues
- Create cloned pigs through nuclear transfer technology
The resulting “ten-edit pig” has become the standard donor formula, though companies add further modifications to differentiate their approaches.
Human Trials and Setbacks
While pig organs perform well in monkeys, human results have been mixed. Tim Andrews maintained his eGenesis-provided kidney for 271 days but eventually required its removal due to declining function. He’s now back on dialysis awaiting a human transplant.
Towana Looney, who received a Revivicor kidney in November 2024, also lost her transplant when doctors reduced her immunosuppressant drugs to fight an infection, triggering rejection.
Future Directions and New Approaches
Researchers are exploring multiple strategies to improve outcomes. eGenesis is collaborating with Eledon on tegoprubart, a new anti-rejection drug with potentially fewer side effects. Revivicor is testing ravulizumab, already used for autoimmune disorders.
Beyond kidneys, scientists are investigating other organs. Revivicor has conducted two pig-heart transplants and received approval for testing its “UThymoKidney” – a combination of pig kidney and thymus tissue that may help train the immune system to accept the new organ.
eGenesis is developing a pig-liver perfusion system that keeps the organ outside the body while connected to the circulatory system, potentially serving as a bridge until human organs become available.
Chinese research teams have reported transplanting pig livers, lungs, and kidneys into both brain-dead and living patients, indicating global interest in advancing the technology.
Currently, Bill Stewart remains the only American living with a pig kidney, but Massachusetts General Hospital plans to perform another transplant later this year, signaling continued progress in this promising field.
Correction (29 October 2025): FDA clearance was granted to United Therapeutics rather than its subsidiary Revivicor.
