Tim Andrew lived for nine months with a genetically modified pig kidney, until it had to be removed. This animal was also the first non-human liver transplanted into a person, although he ended up dying. Research in xenotransplantation has begun a new stage led by the United States and China.
The lack of human organs made science wonder if pig organs would be viable. An investigation that took important steps, especially last year, when the US also authorized the first clinical trials, but that has a long road ahead.
The new push began about four years ago, especially thanks to the CRISPR genetic editing technique, which allows modifications to be made in pigs “with great ease, compared to what was before,” Rafael Matesanz, founder of the Spanish National Transplant Organization, told EFE.
In 2021, xenotransplants of kidneys from genetically modified pigs to brain-dead people began and in 2022 the first was done to a living recipient, it was from the heart and the patient died after two months.
During the year just ended, “very important steps have been taken to achieve the great panacea: organs from pigs that are really useful for transplants,” he added.
Last year, the first liver transplant was performed on a living person, the lung transplant on a brain-dead person, or the record set by Andrew, until his kidney had to be removed due to rejection, compared to the four months that Towana Looney, an American woman, kept it.
The latter was carried out in 2024 by a team from the Langone Health hospital, New York University, led by Robert Montgomery, who highlighted to EFE that the US Food and Drug Administration (FDA) authorized, also in 2025, the first clinical trials with kidneys.
The time from the first gene-edited pig kidney xenotransplant to a brain-dead person, which was done at NYU Langone in 2021, to the first patient enrollment in a clinical trial “has been extremely rapid.”
This authorization is, he said, what was needed for “xenotransplantation to become mainstream in the treatment of chronic kidney disease.”
The trials for final approval “will take a few years to complete and, if the results demonstrate safety and efficacy, xenotransplantation (kidney) will become widespread immediately.”
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FDA cleared another trial for liver xenotransplantation
The FDA also authorized another trial in 2025, which has not yet started, for liver xenotransplantation, not as a definitive therapy, but as a bridge to achieving a human one, Matesanz added.
Clinical trials “change everything”, because they go from being used for very specific cases to something structured. Data will be compared to see if survivals are reasonable and “it will take at least a couple of years to assess whether it is worth continuing.”
Both the first xenotransplantation of a genetically modified pig liver to a living person, and the lung transplant to a brain-dead person, who remained stable and functional during the nine days of follow-up, were carried out by Chinese researchers.
The United States and China are the protagonists of the latest advances in this field and Matesanz considers that “at the moment there is, so to speak, a technological race” between the two.
“The difficult thing,” he said, “is not to place the organ, but to generate the animals with the appropriate genetic mutations” to avoid rejection and diseases. Rejection is, by far, the biggest obstacle and “it is about finding the genetic puzzle so that that organ is tolerated.”
In the United States there are companies such as Revivicor (United Therapeutics) and eGenesis, and in China, at least two others, dedicated to creating transgenic cedars, which have from more than 60 mutations to only three, he adds.
You have to see “who comes up with the perfect formula”, determine which molecules should be removed and added, and, when this is achieved, almost all companies will adopt a similar one.
To date, the greatest advances have occurred in kidney xenotransplantation, an organ that has shown that it is capable of “performing all fundamental functions for long periods of time,” Montgomery highlighted.
Furthermore, it is the organ that undergoes “by far” the most transplants among humans, “so having another source of kidneys will have an enormous impact.”
Xenotransplants have, “from an ethical point of view, many edges” and Matesanz considers that survival is the fundamental one, especially with the kidney, which is not a vital organ given the other current options.
With information from EFE
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