800,000 Americans Are on Dialysis. Two Companies Just Got FDA Clearance to Give Them Pig Kidneys Instead.

Ninety thousand dollars. That is what Medicare pays, per patient, per year, to keep someone alive on dialysis. Multiply by 800,000 Americans with end-stage renal disease, and you arrive at roughly $51 billion annually in federal spending on machines that filter blood three times a week, four hours per session, while patients sit in chairs and wait. Five-year mortality on dialysis exceeds 50%, worse than most cancers.

Meanwhile, 90,000 people sit on the kidney transplant waitlist. Only 28,000 kidney transplants were performed in 2024. Simple, permanent math: demand outstrips supply by a factor of three, and the gap grows every year because diabetes and hypertension prevalence keep climbing.

Two companies believe the answer is pigs.

The 10-Edit Bet vs. the 69-Edit Bet

United Therapeutics and eGenesis both received FDA Investigational New Drug clearance to begin formal human trials of gene-edited pig kidneys. They arrived at the same destination through radically different molecular strategies.

United Therapeutics' UKidney, which received its IND in February 2025, carries 10 gene edits. Four are knockouts: three remove glycan surface antigens (alpha-gal, Neu5Gc, and Sda) that trigger hyperacute rejection in human recipients, and one disables a growth-control gene so the pig kidney stays human-sized. Six are human gene additions designed to express proteins that dampen the complement cascade and coagulation pathways.

eGenesis' EGEN-2784, cleared in November 2025, carries 69 edits. It shares the same three glycan knockouts. But then it diverges. eGenesis used CRISPR to inactivate all copies of porcine endogenous retroviruses, or PERVs, ancient viral DNA sequences baked into every pig genome. This alone accounts for most of the additional edits. On top of PERV inactivation, eGenesis added seven human transgenes for immunological compatibility.

Feature	United Therapeutics (UKidney)	eGenesis (EGEN-2784)
Total gene edits	10	69
Glycan antigen knockouts	3 (alpha-gal, Neu5Gc, Sda)	3 (alpha-gal, Neu5Gc, Sda)
Growth control knockout	1	Not disclosed
PERV inactivation	No	Yes (~59 edits)
Human transgenes	6	7
FDA IND cleared	February 2025	November 2025
Trial population	ESRD, ineligible or 5+ year wait	ESRD, age 50+, on waitlist
Primary endpoint	24 months	24 weeks
Funding	Public company ($UTHR, ~$8B market cap)	$191M Series D (Sept 2024)

The philosophical divide is stark. United Therapeutics is making a minimalist argument: remove the obvious immune triggers, add human compatibility genes, and let modern immunosuppressive drugs handle the rest. eGenesis is making a maximalist argument: eliminate every known risk vector, including retroviruses that have never caused documented disease in humans but theoretically could.

The Living Patients

Both approaches have produced people who are alive and off dialysis. You can name every one of them.

Towana Looney, 53, received a United Therapeutics 10-edit pig kidney at NYU Langone in November 2024. She had donated her own kidney to her mother in 1999, developed kidney failure years later, and spent eight years on dialysis. Sixteen months after her xenotransplant, she is still alive and functioning. "It's a blessing," she told NYU Langone.

Tim Andrews received an eGenesis pig kidney at Massachusetts General Hospital. Before the transplant, he was wheelchair-bound, non-ambulatory, and tethered to dialysis. In June 2025, he threw the first pitch at Fenway Park. He is currently the longest-surviving pig organ recipient in history.

Bill Stewart, eGenesis's second patient, completed a two-hour bike ride a few months after his transplant.

But the field's history includes failure. Rick Slayman, who received the first living pig kidney transplant at Mass General in March 2024, died two months later. His cause of death was not definitively linked to the xenotransplant, but the outcome underscored how early this technology remains.

The Medicare Math Nobody Has Done

Here is an original calculation based on publicly available cost data.

Dialysis costs Medicare approximately $90,000 per patient per year. A conventional human kidney transplant costs roughly $250,000 to $300,000 for the procedure, hospitalization, and first-year follow-up, plus about $15,000 per year in maintenance immunosuppression afterward (according to CMS cost reports). Assume a pig kidney transplant costs the same as a human one: $275,000 all-in for year one, then $15,000 annually.

Break-even math:

Year 1: Transplant cost $275,000 vs. dialysis $90,000. Transplant loses by $185,000.
Year 2: Immunosuppression $15,000 vs. dialysis $90,000. Transplant saves $75,000. Cumulative: -$110,000.
Year 3: Saves another $75,000. Cumulative: -$35,000.
Year 4: Saves another $75,000. Cumulative: +$40,000. Break-even achieved.

A pig kidney pays for itself in under four years. If even 10% of the 800,000 dialysis patients, 80,000 people, received pig kidneys instead, the annual Medicare savings after the break-even period would be roughly $6 billion per year. If 50% did, the number approaches $30 billion annually. For context, total Medicare Part D drug spending is about $200 billion.

These numbers have a critical assumption baked in: pig kidney graft survival comparable to human kidney grafts (median 12 to 15 years). Nobody knows if that assumption holds. The longest-surviving pig kidney recipient has been alive for roughly one year. If pig kidneys last only five years, the math still works, barely, because a second pig kidney would be cheaper than five more years of dialysis. If they last only two years, the calculus collapses.

The PERV Question

The biggest scientific disagreement between the two companies is whether porcine endogenous retroviruses matter.

PERVs are remnants of ancient viral infections embedded in pig DNA. Every pig carries them. In laboratory settings, PERV sequences can infect human cells in culture. In the real world, decades of clinical xenotransplantation (pig heart valves, pig skin grafts for burn patients, pig insulin before recombinant versions) have produced zero documented cases of PERV transmission to humans.

eGenesis argues that long-term, whole-organ transplantation into immunosuppressed patients is categorically different from short-term tissue exposure. An immunosuppressed patient with a permanent pig organ provides exactly the conditions, chronic immune suppression plus continuous viral reservoir contact, under which a retrovirus might activate. eGenesis spent years developing the CRISPR tools to inactivate all PERV copies simultaneously, which required hitting dozens of genomic targets in a single editing campaign.

United Therapeutics' position, by omission, is that PERV inactivation adds complexity without proven clinical benefit. More edits mean more potential off-target effects, longer development timelines, and higher manufacturing costs for the engineered pig herds.

Neither company is wrong yet. That answer will emerge from years of patient monitoring. If a PERV-related adverse event occurs in a United Therapeutics patient but not in an eGenesis patient, the 69-edit approach wins overnight. If no PERV event occurs in either group after a decade of follow-up, eGenesis spent years solving a problem that did not exist. This is the most expensive molecular biology bet in clinical medicine right now, and it will take a decade to settle.

What the Public Thinks

A UNOS survey of 1,400 adults conducted between April and July 2024 found that nearly nine in ten respondents support porcine xenotransplantation. But support was not uniform. Black respondents and Muslim respondents expressed lower support, with concerns centering on patient safety, religious dietary prohibitions, and disease transmission from animal-derived organs. Over 60% of all respondents reported concern about safety or animal-derived disease regardless of their overall support.

These survey results matter because transplant eligibility committees at major hospitals factor patient willingness and social support into candidacy decisions. A technology that 12% of the population opposes on principle will face access disparities layered on top of the existing racial disparities in kidney disease. Black Americans are three times more likely to develop end-stage renal disease than white Americans but are underrepresented on transplant waitlists.

Limitations

This analysis rests on a foundation of single-digit patients. No randomized controlled trial data exists for pig kidney transplantation. All surviving patients received organs under compassionate use or expanded access protocols, which select for the sickest and most motivated candidates, introducing survivorship bias in both directions. The procedure cost of a xenotransplant is unknown and could be substantially higher than a conventional transplant due to the engineered pig supply chain, specialized surgical protocols, and extended immunosuppression monitoring. Long-term graft survival is genuinely unknown: the longest-surviving recipient has been living with a pig kidney for approximately one year. The PERV inactivation question, the core scientific disagreement between the two companies, cannot be resolved with current data. Finally, eGenesis is a private company, and its detailed financial data, pig herd production capacity, and adverse event data are not publicly accessible.

The Strongest Case Against

The strongest argument against pig kidney optimism is the immunosuppression trap. Even with 69 gene edits, recipients need chronic immunosuppressive drugs, the same medications that make conventional transplant patients vulnerable to infections, cancers, and metabolic complications. If pig kidneys do not last as long as human kidneys (median human kidney graft survival: 12 to 15 years from a deceased donor, 15 to 20 from a living donor), patients face serial transplants, each carrying surgical risk and requiring a new pig kidney from a supply chain that does not yet exist at scale. Three pig kidneys over a lifetime may not beat an improved dialysis regimen, especially as artificial kidney research (the Kidney Project at UCSF) progresses toward implantable devices that would eliminate dialysis sessions entirely without requiring immunosuppression. Pig kidneys might be a bridge to a bridge, solving a 2026 problem with a solution that is obsolete by 2036.

What You Can Do

If you or someone you know is on dialysis: Both trials are enrolling. United Therapeutics' trial targets ESRD patients who are either ineligible for conventional transplant or unlikely to receive a kidney within five years. eGenesis's Phase I/II/III study targets dialysis-dependent patients age 50 and older who are already on the transplant waitlist. Search ClinicalTrials.gov for "xenotransplantation kidney" to find enrollment sites. Neither trial requires you to live near a major research hospital for initial screening.

If you are a nephrologist: Begin familiarizing yourself with xenotransplant immunosuppression protocols now. The regimens differ from conventional transplant protocols, and the monitoring requirements are more intensive, including regular screening for PERV markers. Both companies will need clinical sites beyond their initial trial centers as enrollment expands.

If you are an investor: United Therapeutics ($UTHR) is publicly traded with an $8 billion market cap. eGenesis closed a $191 million Series D in September 2024. The addressable market, $51 billion in annual Medicare dialysis spending, is real and growing. But the risk is binary: if pig kidneys last 10+ years, these companies will become among the most valuable in medicine. If graft survival is measured in months, the entire field collapses. Watch the patient survival data quarterly.

The Bottom Line

For the first time in the history of organ transplantation, the supply constraint is not human generosity. It is molecular biology. Two companies have bet billions that CRISPR can turn a pig into a universal organ donor. They disagree on how many edits that requires. Both have patients who are alive, off dialysis, and doing things, throwing baseballs, riding bikes, that they could not do six months ago. Sample size is absurdly small. The stakes, 800,000 Americans filtering their blood through machines three times a week while waiting for a phone call that statistically will never come, are not.