Every 8 minutes, another person is added to the national organ transplant waiting list. Currently, over 103,000 people in the United States are waiting for an available transplant. Many of them will not receive one due to the increasing rate of organ shortages seen all over the country. A recent approval from the U.S. Food and Drug Administration to two biotech companies for research evaluating xenotransplantation — the transplantation of animal organs into humans — has given the medical community hope for the future of organ transplantation.
Clinical trials will be conducted by the United Therapeutics Corporation and eGenesis. eGenesis plans to conduct its analysis with three patients under an Expanded Access Protocol study. The first patient underwent surgery on January 25 and has since been discharged from the hospital. The company reported that there will be a six-month waiting period between the first and second transplant, and another three months before the third.
Starting in mid-2025, United Therapeutics will begin transplantation on a group of six patients between the ages of 55 and 70 with end-stage renal disease. Additionally, the number of patients could rise as high as 50 by the end of the trial period if initial operations are determined to be successful. After surgery, the patients will be monitored over 24 weeks and required to attend regular follow-ups for the rest of their lives to observe any possible complications, such as organ rejection or zoonotic disease.
Researchers have determined that pig kidneys are the most suitable for cross-species transplantation due to their size and similarity to human kidney function. United Therapeutics has developed a xenokidney — dubbed UKidney by the company — by genetically modifying pigs with 10 gene edits, consisting of the addition of six human genes and four pig genes. These gene modifications aim to prevent rejection by the human immune system.
Meanwhile, eGenesis pigs have undergone 69 gene edits, 59 of which exist to inactivate viruses integrated into the pig’s genome. With further genetic research, scientists aim to make long-term immunosuppression unnecessary for patients.
Opponents have questioned the safety and ethicality of the FDA’s decision. Authors affiliated with the Physicians Committee for Responsible Medicine recently published a paper outlining their concerns with the risk of infectious disease transmission to recipients, healthcare workers, and their communities. To combat these concerns, both eGenesis and United Therapeutics are reported to raise and regularly screen their pigs in strict, pathogen-free facilities.
Medical ethicists have pointed out that the large quantity of unknown risks undermines patient consent. In an extreme scenario, an animal organ recipient “could become infected with an undetected pathogen from the porcine source,” said Christopher Bobier, an associate professor specializing in bioethics and health policy at Central Michigan University College of Medicine.
Others express apprehension with the study over the potential cost of pig organ transplants, the allocation of available xeno-organs, and whether or not they will receive insurance coverage. Many critics argue that the funding put towards xenotransplantation studies should instead be invested in more ethical and viable biotechnology, such as regenerative therapies, STEM cell research and bioprinting.
“I would much rather see us putting our time and resources into other things, into preventing organ failure, into treating organ failure, into organ regeneration,” said L. Syd Johnson, a bioethicist at SUNY Upstate Medical University in Syracuse. Johnson has also spoken out about the psychological and social harm the pigs could face under lab conditions.
The future of animal-to-human organ transplantation remains to be seen as eGenesis and United Therapeutics begin conducting trials. While both these companies have experience with xenotransplantation, none of the surgeries performed were part of a formal multi-patient study and were only given to critically ill patients with no other treatment options.
With the FDA approval comes an opportunity for the collection of data on the safety and efficacy of a potentially revolutionary breakthrough in the medical field. “We are entering a transformative era in organ transplantation,” said Mike Curtis, president and chief executive of eGenesis.
