Growing Human Organs in Pigs: What Has Actually Been Done, and What Hasn’t (October 2026)

Last updated: October 1, 2026. Every figure below is traced to a named source in the reference list at the end.

Two different technologies share the headline “pig organs,” and most coverage blurs them together.

One is xenotransplantation: take a pig kidney, heart, or liver, edit its genome so a human body tolerates it better, and transplant it. This is real; it is in registered clinical trials, and a patient lived 271 days without dialysis on one.

The other is chimeric organ growth: delete a pig embryo’s ability to build, say, a kidney, inject human stem cells, and let the pig grow a kidney made largely of human cells. No such organ has ever been transplanted into anyone. The work has not progressed beyond embryos that researchers end after about a month.

My assessment, which I explain below: the first technology has a plausible path to approval within this decade. I would not expect a clinical trial of the second before 2030.

Why anyone is doing this

The US Health Resources and Services Administration reports 109,817 people on the national transplant waiting list (snapshot of July 30, 2026) and states that 12 people die each day waiting. Kidneys dominate: OPTN data from May 2026, compiled by Statista, show 95,178 of 109,307 candidates, or 87%, waiting for a kidney.

Check before you repeat a number. Many websites still say 17 deaths a day, an older figure. Official sources now say 12. The figure of 13 per day for 2023 also circulates, and the 2021 figure was 16. These are different years, not contradictory measurements.

Two technologies, side by side

The clinical record, case by case

The table lists the published or institutionally confirmed living-recipient cases I could verify. Durations are as reported by the sources linked in the references.

What the pattern actually shows

Survival went from weeks to months to nine months in under four years. The usual reading is “the pigs got better.” That is partly true, but it is not the whole explanation, and the other part matters.

AP’s account of the Andrews case notes that researchers deliberately shifted to recipients who were not as sick as the earlier patients. Bennett, for comparison, had spent roughly 40 days on ECMO before his operation, per Medscape’s report on the published case. Slayman had already lost a human kidney and carried a serious cardiac burden. Bill Stewart, who received an eGenesis kidney in June 2025, had kidney failure from high blood pressure and no other serious health problems.

So the improvement from 52 days to 271 days mixes at least two effects: better organs and regimens, and healthier recipients. No published dataset I found separates them. Anyone quoting the trend as proof of steady technical progress is overreading it. The trials under way, which use defined eligibility criteria, are what can resolve it.

Slayman: what is known and not known

Slayman received his kidney on March 16, 2024, left the hospital on April 3, and died 51 days after surgery. STAT reported at the time that he had a rejection episode before discharge, which doctors treated. Mass General’s May statement said there was no indication that his death resulted from the transplant. Six months later, surgeon Tatsuo Kawai said the cause was an unexpected cardiac event and that the autopsy showed no signs of kidney rejection.

Whether the immunosuppression he needed contributed to the cardiac event is a legitimate question. None of the sources I reviewed addresses it, so I will not guess.

Bennett: the lesson that changed screening

The pig heart used for Bennett was tested for pathogens just before shipment and again before transplant, under protocols the FDA had accepted. The University of Maryland later reported that highly sensitive testing found DNA from porcine cytomegalovirus, a latent pig virus, in the heart. Its role in his death is unresolved; the American College of Cardiology’s analysis describes reactivation as a possible contributor, not an established cause.

One correction to a common narrative: this virus is a herpes-family virus, not the endogenous retroviruses (PERVs) that gene editing targets in eGenesis pigs. Those are separate problems. Removing PERVs did not address what happened in Bennett’s case.

The 2026 data point that matters most

In September 2026, The Lancet published the Andrews case as a first-in-human “bridge to allotransplantation” study. He lived 271 days without dialysis, then received a human kidney in January 2026. According to NBC’s report, that kidney has kept him alive since.

Two details deserve equal weight with the headline:

• The bridge was incomplete. Deseret News reports that he developed clots and the organ had to be removed, and he went back on dialysis for roughly three months before the human kidney. Riella said that after the team adjusted his immunosuppression, some damage to the kidney’s filters was not reversible.
• The study was co-funded by the company that supplied the pig. AFP’s report says eGenesis helped fund it, and eGenesis’s CEO told the agency a prior pig kidney does not appear to harm a later human one, based on Andrews’s case and one other. Two patients is a hypothesis, not a safety record.

Beyond kidneys

China reported the first auxiliary pig liver in a living person: the Journal of Hepatology paper describes 171 days of patient survival, but the graft itself was removed on day 38 after a complication, and the patient’s own regrown liver tissue did the long-term work. That is a milestone, but “liver survived 171 days” is a misreading. A Nature Medicine report of a pig lung described gas exchange for 216 hours, but in a brain-dead recipient. Brain-dead models do not capture months of living immune response.

The trials

Sources disagree on eGenesis’s trial size: the company-linked coverage says 30 patients, while CNN reported the CEO’s target as 33 over two and a half years. Check the trial registry entry for the authoritative number.

For timing, the National Kidney Foundation’s April 2026 explainer says experts are hopeful of approval within 5 to 10 years. That is a forecast, and the weakest tier of evidence in this article.

Chimeras: the number that went stale

Older coverage, including the version of this article I was asked to upgrade, says human cells in pig embryos reach only about 1 in 100,000. That was true in 2017: the Salk Institute’s Cell paper estimated about one human cell per 100,000 pig cells, and more than half the embryos showed stunted growth compared with controls.

It is no longer the right number. In 2023, a Guangzhou team published in Cell Stem Cell pig embryos whose developing kidneys were 50 to 60 percent human cells at days 25 to 28. They deleted two genes needed for kidney formation (SIX1 and SALL1) and engineered the human cells to resist cell death.

Why this is not a solved problem either

I recalculated the yield from the reported figures. Smithsonian’s summary reports 1,820 embryos transferred into sows, with 5 structurally normal chimeric fetuses analysed (2 at day 25, 3 at day 28). That is about 0.27%.

Three further limits:

1. It is the wrong kidney. At days 25 to 28 the tissue is the mesonephros, a transient stage. A commentary on the paper notes it is still uncertain whether the human cells persist into the metanephros, the stage that becomes the permanent kidney. The kidney has more than 70 cell types, as Science News noted, and the work did not show all of them.
2. The two percentages are not comparable. 1 in 100,000 is a whole-embryo average; 50 to 60 percent is a measurement inside a target organ whose niche was emptied by gene deletion. The roughly 50,000-fold gap overstates the real progress in a single comparable metric.
3. Cells leak. Co-author Miguel Esteban told Science that human cells may need to be engineered to prevent spread into other parts of the pig, as reported by Smithsonian.

The vascular claim, corrected

The draft said Mary and Daniel Garry’s team produced human endothelium in pig embryos in 2023. The scientific paper is from 2020: Das et al., Nature Biotechnology. The 2023 date belongs to a magazine profile. In embryos at days 17 to 18, all endothelial cells were human. The rest of the embryo was pig, and a later review summarizing the paper reported overall chimerism around 1 in 2,000 cells even with the BCL2 boost.

What Nakauchi’s rodents really established

The draft merged two experiments. In 2010, Nakauchi’s group grew a rat pancreas inside a mouse, but it was mouse-sized and yielded too few islets to treat a larger animal. In 2017 they reversed the setup, growing a mouse pancreas in a rat; islets from it normalized blood glucose in diabetic mice for over 370 days, with immunosuppression only for the first five days.

The reversal is the instructive part. The host’s body sets the size of the organ. That is why pigs, whose organs approximate human size, are the target host, and also why species differences in developmental timing hurt more as the species get further apart.

The question most coverage skips: would a pig-grown human organ really reject less?

This is the founding promise of the whole field, and it is untested in people.

My analysis, not a measured result: a chimeric kidney from the Guangzhou approach would still be roughly 40 to 50 percent pig cells, and the pig cells that matter most are the ones lining blood vessels. That is why Garry’s ETV2 work matters. As Garry told The Scientist, the primary site of rejection is the endothelium. A useful organ probably needs several niche deletions at once, so that kidney tissue and its blood vessels are both human. I found no study that has combined them.

The question cannot be answered directly without a first-in-human transplant. What would resolve it indirectly: showing that human-parenchyma, human-endothelium organs mature in pigs, and then measuring antibody responses in a humanized-immune-system animal. Until then, “less rejection” is a hypothesis.

My timing judgment

In 2023, Garry estimated human trials of pig-grown organs could be ready in as little as five years. I think that is optimistic. My reasons: nothing beyond a transient kidney stage has been shown; yield is under 1%; the multi-gene niche problem is unsolved; and I found no regulatory filing for a human-cell-dominant organ. Treat this as my judgment, not a fact. Xenotransplantation of gene-edited organs is the near-term story.

Ethics and rules: the brain question, answered

The most common public worry is that human cells will end up in the animal’s brain and change its cognition. The evidence is thin in both directions, so here is what exists:

• Nakauchi told Undark (September 2026) that his team’s monitoring framework requires stopping and consulting an oversight committee if human cells exceed 30 percent of a chimera’s brain. Garry said uncontrolled cell migration is not something routinely observed in the lab.
• Chimera experiments in pigs have so far ended at about a month of gestation. Nobody has studied a pig that was born and allowed to mature with human cells.
• The Guangzhou team’s own comment, quoted above, shows migration is still an open engineering problem.

My read: the brain concern is not supported by any dataset showing it happens, but no long-term dataset exists either. That is a reason for staged monitoring, not alarm.

On rules: Japan relaxed its policy in 2019, allowing Nakauchi’s group to proceed under government review, as described in a regulatory review in Cell Transplantation and summaries of the change. A press release for a 2020 survey study noted that the US National Institutes of Health had placed a funding moratorium in 2015 on introducing human stem cells into animal embryos. I could not verify the moratorium’s current status.

How much do the public polls prove?

A widely cited 2020 survey in Stem Cell Reports, “The American Public Is Ready to Accept Human-Animal Chimera Research,” found that 59% of respondents accepted the full pipeline from injecting stem cells to transplanting the resulting organ, 17% accepted none of it, and 55% of self-described conservatives accepted all of it. The sample was 430 people recruited online. A published commentary argued that attitudes are more complicated than the headline suggests. Treat the 59% as a rough signal, not a national measurement.

Who gets the organs?

No source I reviewed gives a price for a pig organ or any pricing plan. Eligibility in the first trials is narrow (age 50 and over for eGenesis; patients unlikely to get a human kidney within 5 years for United Therapeutics) and total enrollment will be under 100 people. Access in the near term will be set by trial criteria, not by markets.

How to read a pig-organ headline

Five questions sort most headlines into “real progress” and “overread”:

1. Is it a gene-edited pig organ or a human-cell organ grown in a pig? Different technologies, different evidence.
2. Was the recipient alive or brain-dead? Brain-dead models run days; living cases run months.
3. Did the graft survive or did the patient? The liver case above is the reminder.
4. How sick was the recipient? Healthier recipients flatter the results.
5. Who paid for the study and supplied the pig? Industry co-funding is normal but should be stated.

If you or someone you care for needs a kidney

These points follow from the eligibility criteria above, but I am not a medical professional, and your transplant team makes the decisions.

• The eGenesis trial requires waitlist status, dialysis dependence, and age 50 or over. If you are not yet on the waitlist, that is a prerequisite to ask your transplant center about now.
• Ask your center whether it participates in either trial. As of March 2026, the National Kidney Foundation said only a small number of centers were enrolling, with NYU Langone among them.
• A pig kidney does not currently appear to rule out a later human kidney. The evidence is Andrews’s case plus one other, reported by an interested party. Ask for the data, not the headline.

What I checked, how, and what remains unverified

To upgrade the earlier draft, I traced each claim to a primary or institutional source where one existed, and I corrected several. While cross-checking, I found the draft misdated the Garry paper (2020, not 2023), merged two Nakauchi experiments from 2010 and 2017, relied on a 2017 chimerism figure that has been overtaken by 2023 data, used waitlist numbers that are now out of date, and implied that eliminating pig retroviruses addressed the virus found in Bennett’s heart.

Evidence ranking, from strongest to weakest:

1. Peer-reviewed papers and institutional reports, such as the Das 2020 and Wang 2023 papers and the University of Maryland case report.
2. Official statistics, such as HRSA waitlist counts.
3. Hospital and company statements, which are reliable on facts and unreliable on interpretation.
4. News reports of trial results, which I used mainly for dates and durations.
5. Expert forecasts, such as the 5-to-10-year approval estimate and Garry’s 2023 timeline.

Limits of my work: I read abstracts, institutional releases and news coverage for most papers, not every full text. I could not access the full Lancet paper. The figures I calculated myself are the 0.27% yield and the roughly 50,000-fold comparison, both from reported numbers. I did not find the current status of the NIH moratorium or any published price for pig organs.

Frequently asked questions

Has a human organ grown in a pig been transplanted into a person?
No. The furthest chimera work is a part-human kidney precursor in pig embryos at days 25 to 28.

Has a pig organ been transplanted into a living person?
Yes: hearts (2022, 2023), kidneys (2024 onward) and an auxiliary liver (2024, China). None is an approved treatment.

What is the longest a pig kidney has worked in a living human?
271 days, in Tim Andrews, as published in The Lancet in September 2026. A Mass General doctor told journalists that another patient had passed that mark, per Smithsonian, citing New Scientist. That case awaits publication.

Are pig organs available outside clinical trials?
No. The two FDA-cleared kidney trials are the formal route.

What’s the difference between a pig organ and a chimeric organ?
A pig organ is made of pig cells with edited genes. A chimeric organ is intended to be made mostly of human cells grown in a gene-edited pig embryo.

Will pig organs end the transplant shortage?
No evidence supports that yet. The trials aim to show safety and 24-week function in a few dozen patients; the waiting list is over 109,000.

References

Waitlist data

• HRSA, Organ Donation Statistics, July 30, 2026 snapshot.
• OPTN data via Statista, Candidates by organ, May 2026.

Xenotransplantation

• Riella L, Borges T, Rosales I, et al. Porcine kidney xenotransplantation as a bridge to allotransplantation: a first-in-human study. The Lancet, 2026. DOI 10.1016/S0140-6736(26)01295-X. Summaries: Medical Xpress, NBC, Deseret News, AOL/CNN, AFP.
• AP, Tim Andrews resumes dialysis after 271 days.
• STAT, Slayman rejection episode, April 2024; Boston Globe on cause of death, November 2024.
• University of Maryland, Bennett findings; ACC analysis; Medscape.
• CNN/AOL, Looney and Andrews; Smithsonian, 271-day removal.
• eGenesis, IND clearance; CNN, trial plans; NYU Langone, EXPAND first surgery.
• National Kidney Foundation, Xenotransplantation explained by experts, April 2026.
• Zhang W, et al. Genetically engineered pig-to-human liver xenotransplantation. Journal of Hepatology, 2025. DOI 10.1016/j.jhep.2025.08.044. Press release; EMJ summary.
• He J, et al. Pig-to-human lung xenotransplantation in a brain-dead recipient. Nature Medicine, 2025; commentary.

Chimeras

• Wang J, et al. Cell Stem Cell 30:1235, 2023. ScienceDaily; Science News; Smithsonian; commentary.
• Das S, et al. Generation of human endothelium in pig embryos deficient in ETV2. Nature Biotechnology, 2020. Link.
• Yamaguchi T, et al. Interspecies organogenesis generates autologous functional islets. Nature 542:191, 2017. Link; Nature Reviews Endocrinology summary (covers the 2010 Cell study).
• The Scientist, Chimera research opens new doors, 2023; dvm360, Salk 2017 report.
• Undark, Engineering Animals to Grow Human Organs, September 25, 2026.

Ethics, policy and public opinion

• Brown JL, et al. Technological and Regulatory Review on Human-Animal Chimera Research. Cell Transplantation, 2023. Link.
• Crane AT, et al. The American Public Is Ready to Accept Human-Animal Chimera Research. Stem Cell Reports 15:804, 2020. Press release; commentary.
• Doolly summary of Japan’s 2019 policy change.

This article is informational and is not medical advice. If you are considering a transplant or a clinical trial, discuss it with your transplant team.