Could Pig Organs End the Transplant Waiting List?

Pig Organs in Humans — Are We About to Solve the Organ Shortage?

Next Horizon • Science / Medicine • Updated September 2026

Genetically engineered pig organs could one day provide a new source of kidneys, hearts and livers for patients who cannot wait for a human donor.

A heart beats inside a human chest. A kidney filters blood and makes urine. A liver produces bile and proteins that help keep the body alive — including proteins that help blood clot.

Nothing about that sounds unusual — until you learn where the organs came from: genetically engineered pigs.

For decades, xenotransplantation — using cells, tissues or organs from one species to treat another — sat somewhere between serious medicine and science fiction. A pig kidney is roughly the right size for a human, but size was never the main problem. The real problem was recognition: the human immune system can spot pig tissue as foreign almost immediately and launch a powerful attack against it.

That barrier is beginning to fall.

Scientists can now breed donor pigs with carefully edited DNA. Some pig genes are switched off. A small number of human genes are added. In some donor lines, researchers also disable pieces of ancient viral DNA that are naturally built into the pig genome. The goal is not to make the pig “more human.” It is to remove the biological warning signs that make an ordinary pig organ so easy for our immune system to attack.

By September 2026, this is no longer a story built around one or two spectacular operations. A genetically edited pig kidney kept Tim Andrews off dialysis for 271 days before he successfully received a human donor kidney — the first published case showing a pig kidney used as a bridge to human transplantation. Formal kidney trials are underway, and the FDA has also cleared the first clinical trial of a genetically engineered pig heart.

So the question has changed. We already know that a pig organ can function inside a human. The harder question is whether doctors can make that function safe, repeatable and durable enough to last for years.

What Is Xenotransplantation and Why Do We Need It?

Modern transplantation has a frustrating contradiction. Surgeons know how to replace a failing kidney, liver or heart. The problem is much simpler to state and much harder to solve: there are not enough human organs available.

In the United States, more than 110,000 people currently need a lifesaving organ transplant, and more than 90,000 are waiting for a kidney. The country performed a record 49,064 organ transplants in 2025, yet demand still far exceeds the number of available human organs.

A transplantable human organ usually becomes available only when another person dies under circumstances that permit donation, or when a living donor can safely give a kidney or part of a liver. Matching, geography, organ condition and timing narrow the supply even further.

Kidney failure shows the problem especially clearly. Dialysis can keep someone alive for years by filtering waste and excess fluid from the blood, but it does not fully replace a healthy kidney. Treatment takes hours every week, can be physically exhausting, puts strain on the heart and blood vessels, and cannot reproduce every hormonal and chemical job the kidneys normally perform.

Now imagine a different system: a patient needs a kidney, and instead of waiting years for a rare human donor, the transplant center can obtain an organ from a standardized, screened donor animal bred specifically for medicine. That is the promise of xenotransplantation.

Why Are Pig Organs Used for Human Transplants?

At first glance, a non-human primate might seem like the obvious donor. Genetically, a chimpanzee or baboon is much closer to us than a pig.

In practice, pigs offer a much better mix of biology and practicality. Their organs can be close to human size, pigs grow and reproduce quickly, and humans already know how to breed them at large scale. They can also be raised in tightly controlled, germ-monitored facilities and genetically edited over multiple generations.

Using primates at the scale required to meaningfully increase the organ supply would create much greater animal-welfare, conservation and infectious-disease problems. Pigs do not make the ethics simple, but they are far more practical as a medical donor species.

Most importantly, modern gene editing gives researchers a way to redesign the specific parts of pig biology that cause trouble inside the human body.

Why Human Bodies Reject Pig Organs

An ordinary pig organ carries chemical markers on the surface of its cells that human cells do not have. To our immune system, those markers can look like bright warning labels saying: foreign tissue.

One of the best-known markers is a sugar molecule called alpha-Gal. Humans naturally carry antibodies that recognize it. If those antibodies meet alpha-Gal on the blood vessels of a pig organ, they can attack almost at once. They also switch on the complement system — a chain reaction of proteins in the blood that helps immune cells destroy threats — and can trigger inflammation and dangerous clotting.

Doctors call this hyperacute rejection. In the worst case, a newly transplanted organ can be badly damaged within minutes or hours, before it ever has a real chance to work.

Modern donor pigs therefore often have three genes switched off: GGTA1, CMAH and B4GALNT2. These genes help produce surface markers that human antibodies readily recognize. Removing them is like taking several of the brightest “foreign tissue” labels off the pig organ before transplantation.

But removing pig markers is only half the job. Researchers can also add selected human genes that help the organ cope with human blood, inflammation, immune attack and clotting.

How Gene Editing Makes Pig Organs More Human-Compatible

Headlines often focus on pigs with 10, 20 or even 69 genetic changes. That number sounds dramatic, and it can give the wrong impression that scientists are trying to turn a pig into something partly human. They are not. The edits are targeted fixes for specific biological problems.

The 69-edit donor platform developed by eGenesis is a good example. The large number becomes much easier to understand when you divide it into three groups:

·         Three pig genes are switched off to remove important immune-system targets.

·         Seven human genes are added to help control immune attack, inflammation and blood clotting.

·         Fifty-nine copies of PERV DNA — ancient pig-virus sequences already built into the pig genome — are disabled.

So the headline number is less mysterious than it first appears. Most of the 69 edits are repeated changes aimed at those built-in viral sequences, not 69 different attempts to make the pig more human.

Other companies use different recipes. United Therapeutics’ UKidney, for example, comes from pigs with 10 edits: six human genes are added and four pig genes are switched off to reduce rejection and help control organ growth. No one yet knows the perfect combination. That is one of the things real clinical trials now have to discover.

Scientists modify donor pigs in several ways: removing genes that trigger human immune reactions, adding helpful human genes and disabling potentially risky PERV sequences.

Pig Kidney Transplants: The Strongest Case So Far

If xenotransplantation reaches routine medicine, the kidney currently has the clearest path to getting there first.

One reason is simple: the need is enormous. Kidneys make up the largest part of the transplant waiting list. There is also a safety advantage. If an experimental kidney fails, doctors can remove it and put the patient back on dialysis. If a transplanted heart suddenly fails, there is far less room for rescue.

In March 2024, 62-year-old Richard “Rick” Slayman became the first living person to receive an eGenesis 69-edit pig kidney at Massachusetts General Hospital. The kidney started working. His creatinine — a waste product doctors measure to judge kidney function — fell, and he no longer needed dialysis.

Then the immune system pushed back. Doctors found T-cell-mediated rejection, meaning immune cells called T cells had started attacking the kidney. That sounds like failure, but the more important part came next: doctors treated the rejection and kidney function stabilized.

Slayman died suddenly on day 52 from cardiac causes. The published case report found severe pre-existing heart disease at autopsy and no evidence that rejection of the pig kidney caused his death.

The case captured the real state of the field. Gene editing can prevent the fastest and most violent forms of rejection, but it does not make the immune system forget that the organ came from another species.

One of the strongest cases so far came from Tim Andrews. He received an eGenesis EGEN-2784 pig kidney in January 2025 and stayed off dialysis for 271 days — a record for a living human recipient at the time. Doctors successfully treated an early T-cell rejection episode. Later, while he was being treated for an infection, they had to reduce the drugs suppressing his immune system. Damage then developed in the kidney’s tiny blood vessels, and the organ eventually failed.

The story did not end there. Andrews later received a human donor kidney, and it worked immediately. Importantly, the months with a pig kidney did not appear to make a later human transplant impossible. That points to a very practical use for xenotransplantation: a pig kidney may not need to last for life. Even if it works for months or years, it could keep someone off dialysis while they wait for a human organ.

The field has also moved beyond one-off emergency authorizations. United Therapeutics’ EXPAND Phase 1/2 study of a 10-gene-edited UKidney began in 2025 and is designed to enroll up to 50 participants. eGenesis has FDA clearance for a formal EGEN-2784 trial expected to begin in 2027. For xenotransplantation, that shift from exceptional cases to standardized trials may matter as much as any single survival record.

Pig kidneys are currently the leading candidates for clinical xenotransplantation, with genetically modified organs already functioning in living patients for months.

Pig Heart Transplants: What the First Human Cases Taught Us

The public story of xenotransplantation changed dramatically in January 2022. Surgeons at the University of Maryland transplanted a genetically modified pig heart into David Bennett, a 57-year-old man with terminal heart disease who was not eligible for a standard human heart transplant.

The heart worked well enough to make history. Doctors were able to take Bennett off the machines that had been supporting his circulation, and the pig heart pumped blood through his body for weeks. He died 60 days after the transplant, after the heart developed severe problems.

The case also exposed several risks at once. Researchers detected DNA from porcine cytomegalovirus, or pCMV, in the donor heart. They also found signs of immune injury. Scientists still debate how much each factor contributed, but one lesson was hard to miss: a donor pig cannot be treated like an ordinary farm animal. It has to be bred, housed, tested and monitored under extremely strict medical conditions.

A second patient, Lawrence Faucette, received a genetically modified pig heart in September 2023. He lived for 40 days. The heart initially functioned well, but later failed in association with rejection.

Two patients surviving only weeks with pig hearts is not enough to call the procedure a clinical success. But the operations answered a question that had been theoretical for decades: a genetically modified pig heart really can keep a living human circulation going.

The next question is whether that result can be repeated safely. In May 2026, the FDA cleared United Therapeutics to proceed with EXPRESS, the first formal clinical trial of its 10-gene-edited UHeart. The study will begin cautiously, with only a small number of participants before any expansion.

Pig heart xenotransplantation has already been attempted in living patients, proving that a genetically modified pig heart can support human circulation — while also revealing major challenges with rejection and infection.

Pig Liver Transplants: The Hardest Test

A kidney filters blood. A heart pumps it. The liver is harder to summarize because it does many jobs at once. It processes nutrients, removes or changes toxins, makes bile, produces important blood proteins, helps control clotting and plays a role in the immune system.

That complexity makes a pig liver especially difficult to use in a human. The organ can appear to be working — for example, it may produce bile — while less visible problems are building. Pig proteins that control clotting do not always work normally with human platelets, the blood cells that help stop bleeding. A mismatch can lead to abnormal clots, bleeding or damage to tiny blood vessels.

In 2025, researchers reported a six-gene-edited pig liver transplanted into a brain-dead human recipient as an extra, supporting liver rather than a complete replacement. The organ produced bile within hours, made albumin — an important blood protein — and continued functioning through the planned 10-day experiment without hyperacute rejection.

The first auxiliary pig-liver transplant in a living recipient provided an even tougher test. A 10-gene-edited pig liver was connected to the circulation of a patient undergoing major surgery for liver cancer. The organ performed several liver functions and avoided immediate rejection. But later, the patient developed thrombotic microangiopathy — damage to very small blood vessels, with abnormal clotting and destruction of blood cells. Doctors removed the pig liver on day 38. The patient survived 171 days after the original operation.

That distinction matters: the pig liver did not function for 171 days. Doctors removed the pig organ on day 38; 171 days was the patient’s total survival after the original operation.

A different strategy may be more realistic in the near term. In 2026, doctors temporarily connected a genetically modified pig liver to a living patient from outside the body. Blood flowed through the pig liver for several days while the patient waited for a human liver transplant. Think of it as a biological support machine: instead of asking the pig liver to live inside the patient for years, doctors use it to buy time.

For liver failure, that may be where xenotransplantation proves useful first: not as a permanent replacement, but as a way to buy days or weeks for the patient’s own liver to recover or for a human donor organ to become available.

A pig liver may not always need to be permanently transplanted. Researchers are also exploring whether it could temporarily process a patient's blood outside the body while doctors wait for recovery or a human donor organ.

Can Pig Organs Transmit Viruses to Humans?

Rejection is only one side of the risk. A transplant patient must take drugs that weaken the immune response. Once an animal organ is placed in that patient, doctors also have to ask the opposite question: could a pig virus or another microorganism come with it?

Some pathogens can be reduced through screening, controlled breeding and biosecure facilities. Others are more complicated.

Porcine endogenous retroviruses, or PERVs, are especially unusual. Long ago, ancestors of modern pigs were infected by retroviruses, and pieces of those viruses became permanently inserted into pig DNA. Pigs now inherit those sequences from their parents. That means doctors cannot solve the issue simply by testing whether one animal currently has an infection.

Some PERVs can infect human cells in laboratory experiments. So far, researchers have not shown PERV transmission in clinical xenotransplant recipients. Still, the risk is taken seriously enough that some donor-pig platforms use CRISPR to disable these viral sequences before the animal is born.

Ordinary pig viruses matter too. The pCMV signal detected in the first pig-heart recipient became a warning to the entire field about how aggressively donor animals need to be screened.

This is why infection is not only a private risk for the recipient. In theory, an animal virus could change inside a human host and eventually become able to spread to other people. There is no evidence that modern pig-organ transplantation has caused such an outbreak, but the possibility is serious enough that recipients may need virus monitoring for many years, possibly for life.

Immune Rejection Is Still the Main Barrier

It is tempting to think scientists can simply keep deleting pig genes until the human immune system gives up. Unfortunately, the immune system is much more complicated than one on-off switch.

Several defenses work at the same time. Antibodies can bind to the organ. T cells and other immune cells can attack it. Proteins in the blood can amplify the response. Inflammation and clotting can damage its tiny blood vessels. Stop one pathway, and another may still become a problem.

A detailed 2026 study of the first living recipient of the 69-edit eGenesis kidney showed this clearly. Doctors had removed most T cells from the bloodstream, yet an early T-cell rejection episode still occurred. Immune cells hiding in tissues and lymph nodes were enough to matter.

The good news is that doctors were able to treat the rejection. The bad news is what this may require: strong drugs that hold the immune system back.

Use too little immune-suppressing medicine and the pig organ may be attacked. Use too much and the patient becomes more vulnerable to serious infections and other complications. The real goal is not simply to keep a pig organ alive at any cost. It is to find a level of treatment a patient can realistically live with for years.

Gene editing can remove some of the signals that make pig organs look foreign to the human immune system, but recipients still require powerful anti-rejection treatment.

Even a Gene-Edited Pig Organ Is Still a Pig Organ

Even if rejection were solved, a second problem would remain: pig biology is still pig biology. Pig and human proteins, hormones and clotting systems are similar enough to work together in many ways, but they are not identical.

A pig kidney has to respond to human blood pressure, salt levels and hormones. A pig liver releases pig versions of proteins into human blood. A pig heart has to adapt to the demands of a human body day after day, potentially for years.

Even organ growth matters. Some donor pigs have the growth-hormone receptor gene switched off partly to reduce the risk that an organ continues growing too much after transplantation.

This is why a successful first week proves only so much. A pig organ can work beautifully at first and still develop problems months later because of slow immune damage, injured blood vessels or small biological mismatches that only become obvious with time.

The Animal-Welfare Question

If xenotransplantation succeeds at scale, medicine could eventually require large populations of genetically engineered pigs raised specifically as organ donors.

Supporters point out that humans already raise and kill vast numbers of pigs for food, and argue that using a much smaller number to save human lives can be justified. Critics answer that donor pigs are not simply agricultural animals: they may be cloned or selectively bred, heavily engineered and kept in unusually controlled environments because a routine infection could make their organs unusable.

That raises real questions. How much space and enrichment should donor pigs receive? Does extreme biosecurity conflict with normal animal behavior? Is it acceptable to engineer an animal specifically so that its body is more useful to another species?

Religious and cultural views will differ as well. Some patients may refuse pig organs even if the technology becomes safe. Others facing dialysis, heart failure or imminent death may see the choice very differently.

Xenotransplantation Ethics Go Beyond the Patient

Most medical consent focuses on the risks and benefits to the individual patient. Xenotransplantation adds a public-health layer that ordinary transplantation usually does not.

Imagine that a recipient wants to stop participating in follow-up years after receiving a pig organ. In most medical research, participants retain a strong right to withdraw. But if long-term surveillance is partly intended to detect a potentially transmissible animal virus, the decision could affect family members, healthcare workers and the public.

That is why xenotransplant trials can ask more of patients than an ordinary transplant study. Recipients may need long-term blood tests, repeated screening for pig pathogens and, in some protocols, special discussions about what monitoring could mean for people who live closely with them.

There is also the question of fairness. Xenotransplantation could technically increase the organ supply and still fail to solve the wider problem if each procedure is so expensive that only a small number of wealthy health systems can offer it.

So a real solution to the organ shortage has to do more than keep an organ alive. Hospitals must also be able to produce the organs safely, transport them, regulate the process and afford the treatment at a scale that helps more than a handful of patients.

Could Pig Organs Actually End the Transplant Waiting List?

Possibly — but only if we are precise about what “solve” means.

If “solve” means human donor transplantation disappears in the next few years, then no. Human organs remain the standard of care, and no pig organ has yet shown the years — let alone decades — of dependable function expected from an established transplant treatment.

If it means creating a second organ supply large enough to reduce deaths and years spent waiting, the possibility is becoming much harder to dismiss.

Kidneys may arrive first because demand is enormous and dialysis provides a fallback. Pig livers may first become temporary bridges for acute liver failure. Hearts will require especially convincing safety and durability because a failed cardiac graft leaves much less room for rescue.

There may never be one universal “human-compatible pig.” Different organs may need different genetic designs. A kidney donor might need one set of changes. A liver may need extra protection against clotting problems. A heart may need additional changes to control growth and protect blood vessels.

What Could Xenotransplantation Look Like in 2 Years?

The immediate future is not about millions of pig-organ transplants. It is about reproducibility.

Formal kidney and heart trials will start answering questions that one-off emergency procedures cannot. Do different patients develop the same types of rejection? Can hospitals reliably keep donor pigs free of dangerous infections? Which immune-suppressing drugs work best? And which gene edits are actually necessary rather than simply possible?

The most important milestone may sound less dramatic than the first pig heart or the first 69-edit kidney: several patients receiving the same engineered organ under the same protocol and obtaining broadly similar results.

That is the point when xenotransplantation starts to look less like a succession of extraordinary experiments and more like a medical treatment.

What Could Xenotransplantation Look Like in 5 Years?

By the early 2030s, if current trials are successful, pig kidneys could have a defined role for selected patients with end-stage kidney disease — especially people facing years of dialysis and a very low probability of receiving a human kidney in time.

A pig kidney might initially be used as a bridge rather than a lifetime replacement. That would still matter enormously. Even two or three years without dialysis could improve daily life, protect the patient’s health and buy time for a human donor kidney to become available.

Pig-liver systems may first be used as temporary support during sudden liver failure or as a bridge to a human transplant. Pig-heart transplantation may remain limited to highly specialized centers until doctors can predict long-term survival much more reliably.

We should also expect donor pigs to change. The first successful commercial design may not be the 10-edit or 69-edit pig being tested today. Clinical data will tell researchers which modifications help, which are unnecessary and which new problems need to be engineered around.

What Could Xenotransplantation Look Like in 10 Years?

The most radical possibility is not simply that pig organs become available. It is that transplantation begins to change from something dependent almost entirely on rare human donors into something that can be planned and produced.

Today, a donor kidney can become available with little warning. In a mature xenotransplant system, an organ could come from a standardized line of donor pigs raised under strict pathogen-control rules, with its genetic profile known long before surgery.

Hospitals might eventually be able to choose the right organ size and genetic design for a patient. Supply could be planned instead of depending on whether a suitable human donor happens to appear at the right moment.

Xenotransplantation may also develop alongside other technologies. Lab-grown tissues, organs made from stem cells, 3D bioprinting and regenerative medicine are all chasing the same goal: replacing damaged human organs without depending on a scarce donor supply.

Pig organs may turn out to be the final answer. Or they may become the bridge technology that saves hundreds of thousands of lives until fully human replacement organs can be grown on demand.

The Strange Future of Organ Transplantation

There is something wonderfully strange about the whole idea. One of the most advanced uses of CRISPR and modern genetics may ultimately depend on an animal humans domesticated thousands of years ago.

Yet the last few years have changed what is reasonable to imagine. Pig kidneys have kept living patients off dialysis for months. Pig hearts have supported human circulation. Pig livers have performed useful functions both inside the body and while connected from outside it. Rejection that once would have destroyed an organ almost immediately can sometimes be treated, and formal clinical trials are now replacing isolated experimental cases.

None of this means the problem is solved. An organ that works for months is not automatically an organ that will work for years. Slow rejection, infections, clotting problems, biological mismatches, the side effects of immune-suppressing drugs, animal welfare, public acceptance, regulation and cost are all still serious obstacles.

Still, xenotransplantation has crossed an important line. For decades, the dream was simply to make a pig organ work inside a human at all. Now the challenge is more practical — and in some ways harder: how do we turn success measured in weeks or months into reliable organ function measured in years?

If researchers can solve that, one of transplantation medicine’s oldest limitations could begin to disappear. A patient might no longer need a rare human donor to become available before a lifesaving organ can be transplanted.