Pig Organs in People: The Record from 2021 to 2025


Moving an organ from one species into another is called xenotransplantation. For most of the twentieth century it failed within minutes or days. Between 2021 and 2025 that changed: kidneys, hearts, a liver and a lung from gene-edited pigs were placed into people, first into people who had been declared brain-dead and then into living patients who had no other option. This page goes through that record one case at a time, each from its own published report, and sets out what went wrong as plainly as what went right. It is a companion to the page on Joseph Murray and E. Donnall Thomas, whose Nobel Prize work made human-to-human transplantation routine.

Every patient described below was treated under research or compassionate-use rules. None of these operations is an available treatment, and the published reports describe survival measured in days, weeks and months, not years.


Table of Contents

  1. The Organ Shortage Behind the Research
  2. Why a Pig Organ Is Attacked Within Minutes
  3. The Gene Edits, Described Plainly
  4. Pig Kidneys in Brain-Dead People, 2021–2022
  5. Longer Studies in Brain-Dead People
  6. The First Pig Heart in a Living Person, 2022
  7. The Second Pig-Heart Recipient
  8. The First Living Pig-Kidney Recipient
  9. Pig Livers and a Pig Lung
  10. The Infection Question
  11. Ethics, Consent and the First Trials
  12. What Is Still Not Known
  13. Key Research Papers
  14. Connections
  15. Featured Videos

The Organ Shortage Behind the Research

The reason anyone is trying this is the gap between the number of people who need an organ and the number of human organs available. The United States keeps the most detailed public record. Its 2024 national kidney report, from the Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients, gives these figures (Lentine 2026):

A 2026 review of pig kidneys describes the same picture worldwide: the number of people with kidney failure keeps rising, and the supply of suitable human organs is unlikely to meet the projected demand (Makkar 2026). A 2025 review of pig hearts in the journal Circulation makes the same point about donor hearts (Phillips 2025). How people with kidney failure manage in the meantime — dialysis, a human transplant, or conservative care — is covered on the dialysis and kidney transplant page.

Pigs are the animal chosen because their organs are close to human size and the pig is, in the 2026 review's words, the most preferred donor animal for the kidney because of its physiological similarity to humans (Makkar 2026).

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Why a Pig Organ Is Attacked Within Minutes

The body's immune system treats any tissue it does not recognise as foreign. With a human donor kidney, the main problem is the human leukocyte antigen (HLA) markers that differ from person to person; that story is told on the Benacerraf, Dausset and Snell page. With a pig organ the problem starts earlier and is far more violent.

The blood vessels inside a pig organ are lined with sugar molecules that human cells do not make. The best known is alpha-gal (galactose-alpha-1,3-galactose). People already carry antibodies against such pig sugars before any transplant. When human blood first flows through an unmodified pig organ, those ready-made antibodies bind to the vessel lining, switch on the complement system (a chain of blood proteins that punches holes in cells) and trigger clotting. The organ can be destroyed within minutes to hours. This is called hyperacute rejection, and the 2026 kidney review names it, along with innate immune responses and later chronic rejection, as the main obstacles (Makkar 2026). The 2022 New York report states plainly that hyperacute rejection had been the central challenge in pig-to-human work (Montgomery 2022).

Alpha-gal is the same sugar behind alpha-gal syndrome, the tick-driven allergy to red meat. In that condition the antibody involved is immunoglobulin E, the allergy antibody; the page on the natural history of alpha-gal syndrome describes the "natural" immunoglobulin M and immunoglobulin G antibodies to alpha-gal that are found in people generally. In transplantation it is those everyday antibodies, not an allergy, that attack the organ.

Removing alpha-gal does not end the problem. The reports below describe a second wave: antibody-mediated rejection, in which antibodies against other pig markers slowly damage the organ's small blood vessels over days to weeks, and T-cell-mediated rejection, in which the immune system's T cells attack the graft directly.

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The Gene Edits, Described Plainly

The pigs used since 2021 were bred from cells whose genes had been changed in the laboratory. The changes fall into three groups.

The number of edits varies widely between programmes. The pig hearts used in Maryland and in the New York brain-dead heart studies carried 10 edits (Griffith 2022; Moazami 2023). The Massachusetts kidney carried 69 (Kawai 2025). At the other end, the New York team's 61-day study used a kidney with only the single alpha-gal knock-out, paired with the pig's own thymus tissue (Montgomery 2026). Which combination works best has not been settled.

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Pig Kidneys in Brain-Dead People, 2021–2022

Before trying a pig organ in a living patient, two teams used a new kind of study: the "decedent model". A person who has been declared brain-dead, whose family agrees, is kept on a ventilator while a pig organ is attached and studied for a set time. Nobody can be harmed by organ failure, and the organ meets real human blood.

The Alabama study

The University of Alabama at Birmingham team removed both of a brain-dead man's own kidneys and transplanted two kidneys from a gene-edited pig, after a new cross-match test showed the recipient's blood was compatible (Porrett 2022). As reported:

The New York study

At New York University (NYU) Langone, surgeons attached kidneys from alpha-gal knock-out pigs, each carrying a patch of the pig's own thymus tissue, to two brain-dead recipients and followed them for 54 hours (Montgomery 2022). As reported:

A later, much more detailed examination of two pig kidneys from these brain-dead studies told a less tidy story. Using tissue staining, gene-activity profiling and other methods, an international team found early signs of antibody-mediated rejection: inflammation in the tiny vessels, antibody deposits, activated vessel lining and positive cross-match tests against the pig cells (Loupy 2023). Their conclusion was that, despite good short-term results and no hyperacute injury, antibody-mediated rejection might already be under way.

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Longer Studies in Brain-Dead People

A week of body chemistry, Alabama

The Alabama team transplanted 10-gene-edited pig kidneys into another brain-dead adult whose own kidneys had been removed and measured the body's salt, water and hormone balance for seven days (Judd 2024). Mean blood pressure stayed above 60 mmHg. The pig kidneys released renin, a blood-pressure hormone, and responded to the human water-balance hormone vasopressin. Urine output fell from 37 litres to 6 litres per day, creatinine fell to 0.9 mg/dL by day seven, and filtering measured between 90 and 240 mL per minute.

Two pig hearts, New York

The NYU team placed hearts from 10-gene-edited pigs into two brain-dead people and monitored them for 66 hours (Moazami 2023). Both hearts worked well immediately and kept working through the study. In one case heart function declined after the operation, which the authors attributed to a size mismatch between the pig and the recipient. They found no cellular or antibody-mediated rejection and no transmission of pig infections.

61 days with one pig kidney, New York

The longest decedent study published so far kept a brain-dead person supported for a planned 61 days with a kidney from a pig carrying only the alpha-gal knock-out, using immune-suppressing drugs already approved for human transplants (Montgomery 2026). As reported:

The authors conclude that these pre-existing T cells, and antibodies against pig markers that have not yet been identified, are a major challenge even with strong immune suppression.

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The First Pig Heart in a Living Person, 2022

On 7 January 2022, surgeons at the University of Maryland transplanted a heart from a 10-gene-edited pig into a 57-year-old man with end-stage heart failure (Mohiuddin 2023). He could not walk, was kept alive by a heart-lung bypass machine (venoarterial extracorporeal membrane oxygenation, ECMO) and was not a candidate for a human heart (Griffith 2022). His immune suppression was built around a drug that blocks the CD40 signal between immune cells.

What went right. He came off the bypass machine, and the pig heart worked normally without apparent rejection for about seven weeks (Griffith 2022).

What went wrong. On day 49 the heart wall suddenly thickened and stiffened and the heart failed; life support was withdrawn on day 60. At autopsy the pig heart was swollen with fluid and nearly double its original weight. The first report, in 2022, described scattered heart-muscle cell death and leaked red cells but no small clots, and said these findings were not consistent with typical rejection (Griffith 2022).

The fuller 2023 analysis in The Lancet points to three overlapping causes (Mohiuddin 2023):

The team states that hyperacute rejection was avoided. A later review of infections in pig donors notes that porcine circovirus was also detected in the transplanted heart and in the patient (Mueller 2024).

Heart failure itself — what it is and how it is usually treated — is covered on the heart failure page.

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The Second Pig-Heart Recipient

The Maryland team's second case, published in 2025, was designed around the lessons of the first: a healthier recipient and more sensitive screening of the donor pig for viruses (Griffith 2025). The recipient was a 58-year-old man whose heart failure, caused by damage from coronary artery disease, had progressed to the point of depending on heart-stimulating drugs, and who was not a candidate for standard advanced treatments. He received a 10-gene-edited pig heart and an immune-calming antibody that blocks the CD40 ligand signal.

What went right. The heart pumped and relaxed very well for the first several weeks. No sign of porcine cytomegalovirus multiplying in the heart was found.

What went wrong. The heart then developed rapidly worsening stiffness, thickening of both ventricle walls and, finally, near-complete loss of its pumping strength, so the bypass machine was started on day 31. After 40 days the patient chose to move to comfort care. As in the first case, the tissue showed little immune-cell invasion but did show injury to the capillary lining, swelling and early scarring. The authors conclude that ways of overcoming antibody-mediated rejection are needed to move the field forward.

Summing up both cases, the 2025 Circulation review states that the two recipients survived 40 and 60 days and that the pig heart failed before death in both (Phillips 2025). A 2026 review of all living recipients describes both hearts as ultimately limited by antibody-mediated rejection and infectious complications (Ladowski 2026).

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The First Living Pig-Kidney Recipient

At Massachusetts General Hospital in Boston, a 62-year-old man on hemodialysis received a pig kidney with 69 gene edits (Kawai 2025). He had had diabetes for many years, advanced blood-vessel disease, and great difficulty keeping a working dialysis access. The report in the New England Journal of Medicine appeared in 2025.

What went right. The kidney worked immediately. His creatinine fell promptly and steadily, and he no longer needed dialysis.

What went wrong. On day 8 he had an episode of T-cell-mediated rejection, which stronger immune suppression reversed. Despite steady kidney function, he died suddenly of heart causes on day 52. The autopsy found severe coronary artery disease and scarring of the heart muscle, with no evident rejection of the pig kidney (Kawai 2025). The 2026 review of living recipients describes the death as an unrelated heart-rhythm event (Ladowski 2026).

How a pig kidney ran a human body

A companion report followed his body chemistry over 51 days after the operation (Lee 2025). The pig kidney cleared waste, balanced blood salts and made concentrated urine, and it supported blood pressure and sodium handling even though the body's main blood-pressure hormone system (renin-angiotensin-aldosterone) was less active than usual. The reported differences from a human kidney were:

The authors present these as areas needing further research. The wider background on kidney failure is on the kidney disease page.

Other pig-kidney recipients

News reports describe further living pig-kidney recipients at hospitals in the United States in 2024 and 2025. The PubMed records read for this page did not include full peer-reviewed case reports of those patients, so their outcomes are not described here. The 2026 review of peer-reviewed experience in living recipients covers one kidney case, the Massachusetts one (Ladowski 2026).

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Pig Livers and a Pig Lung

By 2025 teams in China had moved beyond kidneys and hearts.

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The Infection Question

Any transplant can carry an infection from donor to recipient. With pigs the worry is a pig germ adapting to people — a new "xenozoonosis" — in a recipient whose immune system is deliberately suppressed. The infectious-disease community of the American Society of Transplantation set out its guidance in 2023 (Mehta 2023):

The first Maryland heart showed why testing matters. A 2024 review notes that porcine cytomegalovirus and porcine circovirus were found in the transplanted heart and in the patient, and argues that validated detection methods are needed for donor pigs and recipients before and after transplant; the concept of "designated pathogen-free" donor pigs was developed for this purpose, and confirming the absence of latent viruses is hard (Mueller 2024). The brain-dead studies reported no detected transmission of porcine retroviruses (Porrett 2022) and no zoonotic transmission (Moazami 2023), but those studies lasted hours to weeks.

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Ethics, Consent and the First Trials

The brain-dead model. A 2026 scoping review collected 26 publications on pig organs in brain-dead recipients: 11 experimental studies reporting 13 cases from the United States and China, covering kidney, heart, liver and lung, and 15 commentaries (Jin 2026). Most studies showed good immediate function without hyperacute rejection. The commentaries raised limits of study design, the short observation periods and ethical oversight, including informed consent. The authors describe the model as offering short-term insight while posing persistent ethical and regulatory challenges.

Regulation and public trust. A 2026 review of governance states that in the United States, transplants of pig organs into living patients have been authorized under the Food and Drug Administration's Expanded Access program, that clinical pig liver and kidney transplants have been reported in China, and that during 2025 the first clinical trials of pig kidney and pig liver transplants were approved in the United States (Fovargue 2026). The review lists issues still to be settled before those trials begin: which regulator is responsible, how informed consent is written, and how recipients are monitored over the long term. It argues that starting trials too soon, or without suitable regulation, could damage public trust in this technology and in science more widely.

Who receives a pig organ. Every living recipient described on this page had no realistic alternative: no human heart could be offered, or dialysis access was failing, or a cancer could not be removed. The 2026 review of living recipients names optimal patient selection as one of the key open challenges (Ladowski 2026).

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What Is Still Not Known

The Burnet and Medawar page explains immune tolerance, the idea behind several of these approaches — teaching the immune system to accept a graft, as the New York team attempted with the pig's thymus tissue.

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Key Research Papers

  1. Lentine KL, Smith JM, Lyden GR, Miller JM, Booker SE, Dolan TG, et al. OPTN/SRTR 2024 Annual Data Report: Kidney. Am J Transplant. 2026;26(8S1):S22-S145. PubMed PMID: 42276698
  2. Makkar D, Gakhar D, Rakha A. Xeno kidney: revolutionizing kidney disease treatment. Front Nephrol. 2026;6:1707170. PubMed PMID: 41800117
  3. Niu D, Wei HJ, Lin L, George H, Wang T, Lee IH, et al. Inactivation of porcine endogenous retrovirus in pigs using CRISPR-Cas9. Science. 2017;357(6357):1303-1307. PubMed PMID: 28798043
  4. Porrett PM, Orandi BJ, Kumar V, Houp J, Anderson D, Cozette Killian A, et al. First clinical-grade porcine kidney xenotransplant using a human decedent model. Am J Transplant. 2022;22(4):1037-1053. PubMed PMID: 35049121
  5. Montgomery RA, Stern JM, Lonze BE, Tatapudi VS, Mangiola M, Wu M, et al. Results of Two Cases of Pig-to-Human Kidney Xenotransplantation. N Engl J Med. 2022;386(20):1889-1898. PubMed PMID: 35584156
  6. Loupy A, Goutaudier V, Giarraputo A, Mezine F, Morgand E, Robin B, et al. Immune response after pig-to-human kidney xenotransplantation: a multimodal phenotyping study. Lancet. 2023;402(10408):1158-1169. PubMed PMID: 37598688
  7. Judd E, Kumar V, Porrett PM, Hyndman KA, Anderson DJ, Jones-Carr ME, et al. Physiologic homeostasis after pig-to-human kidney xenotransplantation. Kidney Int. 2024;105(5):971-979. PubMed PMID: 38290599
  8. Moazami N, Stern JM, Khalil K, Kim JI, Narula N, Mangiola M, et al. Pig-to-human heart xenotransplantation in two recently deceased human recipients. Nat Med. 2023;29(8):1989-1997. PubMed PMID: 37488288
  9. Montgomery RA, Stern JM, Fathi F, Suek N, Kim JI, Khalil K, et al. Physiology and immunology of a pig-to-human decedent kidney xenotransplant. Nature. 2026;650(8100):218-229. PubMed PMID: 41233546
  10. Griffith BP, Goerlich CE, Singh AK, Rothblatt M, Lau CL, Shah A, et al. Genetically Modified Porcine-to-Human Cardiac Xenotransplantation. N Engl J Med. 2022;387(1):35-44. PubMed PMID: 35731912
  11. Mohiuddin MM, Singh AK, Scobie L, Goerlich CE, Grazioli A, Saharia K, et al. Graft dysfunction in compassionate use of genetically engineered pig-to-human cardiac xenotransplantation: a case report. Lancet. 2023;402(10399):397-410. PubMed PMID: 37393920
  12. Griffith BP, Grazioli A, Singh AK, Tully A, Galindo J, Saharia KK, et al. Transplantation of a genetically modified porcine heart into a live human. Nat Med. 2025;31(2):589-598. PubMed PMID: 39779924
  13. Phillips KG, Aljabban I, Wolbrom DH, Griesemer A, Leacche M, McGregor C, et al. Cardiac Xenotransplantation: Current State and Future Directions. Circulation. 2025;152(1):58-73. PubMed PMID: 40623074
  14. Kawai T, Williams WW, Elias N, Fishman JA, Crisalli K, Longchamp A, et al. Xenotransplantation of a Porcine Kidney for End-Stage Kidney Disease. N Engl J Med. 2025;392(19):1933-1940. PubMed PMID: 39927618
  15. Lee SA, Lafargue MC, Williams WW, Safa K, Palsson R, Al Jurdi A, et al. Physiologic Homeostasis in a Living Human after Pig Kidney Xenotransplantation. Nat Commun. 2025;16(1):8453. PubMed PMID: 41006232
  16. Tao KS, Yang ZX, Zhang X, Zhang HT, Yue SQ, Yang YL, et al. Gene-modified pig-to-human liver xenotransplantation. Nature. 2025;641(8064):1029-1036. PubMed PMID: 40140580
  17. Zhang W, Xu Q, Xu K, Jiang R, Wang S, Zheng M, et al. Genetically engineered pig-to-human liver xenotransplantation. J Hepatol. 2026;84(3):587-598. PubMed PMID: 41076089
  18. He J, Shi J, Yang C, Peng G, Ju C, Zhao Y, et al. Pig-to-human lung xenotransplantation into a brain-dead recipient. Nat Med. 2025;31(10):3388-3393. PubMed PMID: 40855190
  19. Mehta SA, Saharia KK, Nellore A, Blumberg EA, Fishman JA. Infection and clinical xenotransplantation: Guidance from the Infectious Disease Community of Practice of the American Society of Transplantation. Am J Transplant. 2023;23(3):309-315. PubMed PMID: 36695690
  20. Mueller NJ, Scobie L. Potential Infectious Complications in Pig Xenograft Donors and Recipients. Transpl Int. 2024;37:13594. PubMed PMID: 39882566
  21. Jin Z, Yang S, Sasai M, Tsukamoto Y, Yamamoto Y. Human Brain-Dead Recipient Model in Solid Organ Xenotransplantation: A Scoping Review of Technical and Ethical Issues. Xenotransplantation. 2026;33(3):e70145. PubMed PMID: 42216419
  22. Fovargue S. Governance, regulation and public trust in xenotransplantation. Curr Opin Organ Transplant. 2026;31(1):21-26. PubMed PMID: 41479220
  23. Ladowski JM, Meier RPH. Xenotransplantation in living human recipients: Where we stand in 2026: Vital Insights into Xenotransplantation. Am J Transplant. 2026;26(5):913-915. PubMed PMID: 41935634

PubMed Topic Searches

  1. PubMed: pig kidney xenotransplantation in humans
  2. PubMed: pig heart xenotransplantation in humans
  3. PubMed: xenotransplantation in brain-dead (decedent) recipients
  4. PubMed: porcine cytomegalovirus and xenotransplantation
  5. PubMed: antibody-mediated rejection of pig xenografts

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Connections

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