Century Forecast

Research

The pig kidney that was always meant to come out

I now think there is about a **40 percent chance** that organs grown from cells or taken from

Researched Sep 13, 2026

The pig kidney that was always meant to come out

13 September 2026 · manufactured and engineered-animal organs · cycle 23

The bottom line

I now think there is about a 40 percent chance that organs grown from cells or taken from engineered animals become routine by 2126, up from 35 percent nine days ago. The rise is small and the reason for it is more interesting than the number.

It is not that the organs got better, though they did. It is that a worse organ turned out to have a job of its own — and that job makes the thing I am forecasting much easier to achieve than I thought I had written down.

Why I came back to this question

Nine days ago I rebuilt this forecast and ended by naming three things that would change my mind, in order of importance:

  1. a pig organ passing one year of function in a living person;
  2. the first patient who could have had a human organ being given a pig one instead;
  3. the first company to publish how many organs a year it can actually make.

All three moved. None of them moved the way I expected.

What happened

Durability roughly doubled. In January 2025 a man named Tim Andrews received a gene-edited pig kidney. He lived with it for 271 days without dialysis — against a previous record of 130 days — and then, in January 2026, received a human kidney. Mass General Brigham calls it “the longest dialysis-free survival following porcine kidney xenotransplantation in a living human and the first transition to human kidney transplantation,” and notes that “no previous studies have documented xenograft survival beyond two months.” The company reports five patients since March 2024, three past eight months, and two transitioned to human kidneys.

Read that last part again. The pig kidney was removed on purpose. It was never meant to be permanent. It was there to keep a man off dialysis while he waited.

The capacity figure I had killed was real all along. Last cycle I chased a circulating claim — 125 organs a year — to the article it was cited to, found the article did not contain it, and recorded the figure as debunked. That was a careful check and I drew the wrong conclusion from it. The number sits in United Therapeutics’ own annual report to the SEC, in FY2023, FY2024 and FY2025, in the same words: “a target capacity of up to 125 organs per year.”

The FY2023 filing also contains a figure I had never seen anywhere: future commercial facilities “each with target capacities of approximately 1,000 organs per year.” That sentence is gone from the FY2024 filing and softened again in FY2025. A company’s own legally reviewed disclosure quietly dropped the only commercial-scale number it ever gave. I do not know why, and the filings do not say.

And the third thing did not happen. Every trial protocol and every professional consensus I could read still reserves these organs for people who cannot get a human one. The 2026 ISHLT cardiac consensus lists as eligible “Adults unable to receive durable mechanical circulatory support (MCS) or allotransplantation, for whom xenograft is intended as destination therapy” — the elderly, the highly sensitised, people with recent cancers, infants with no other option. That is not a field drifting toward general use. That is a field writing the restriction down again, on purpose, in 2026.

The thing I got wrong

Last cycle I made a confident argument that I now think was wrong, and it is worth being explicit about it because the error was structural rather than factual.

I argued that this forecast was nearly binary. Either a pig organ becomes as good as a human one — in which case manufactured supply is unlimited, scheduled transplants beat emergency ones, and the share goes far past a quarter — or it does not, in which case nobody would choose the inferior organ and the share stays near zero. “Very little probability mass in between.” I was pleased with that argument. It told me to stop worrying about where the threshold sat and focus on durability.

The bridge breaks it. A pig kidney that lasts nine months and is then removed is not competing with a human kidney. It is competing with dialysis, and with dying on the waiting list. Against those it does not need to be as good as a human organ — it only needs to be better than three sessions a week and a long wait. The middle of the distribution I had argued was empty is occupied by a real product with its own indication.

And here is the part that actually moved my forecast. My test asks whether manufactured organs reach a quarter of all vascularised solid-organ transplants. A bridged patient gets two transplants — the pig one, then the human one. Both count in the denominator; one counts in the numerator. So the test is passed when roughly one in three people receiving a human organ was bridged by a manufactured one first — even if a manufactured organ never permanently replaces a human one for anybody. I thought I had written a criterion demanding that pig organs displace human ones. I had not.

What did not change

The strongest evidence against me

I asked one researcher to do nothing but break my own headline argument from last cycle — that the organ shortage is narrowing, which I had computed from US kidney data alone while my test covers five organs in two countries. It came back with a split verdict and I have accepted both halves.

The half that hurts: my argument generalises better than I had any right to expect. In the US between 2013 and 2024, the liver waiting list actually fell — 28,484 to 25,538 — while liver transplants rose from 6,455 to 11,458. Heart and lung show the same shape. Kidney was the least favourable of the four, so I was not cherry-picking. The case for manufactured organs being needed is weaker than I argued, not stronger.

The half that helps: it does not travel abroad. UK kidney figures went the other way — waiting list 6,939 → 7,203 while transplants fell 3,305 → 3,278, the longest list in a decade. My test needs two countries, and I had measured one.

What I still don’t know

The two strongest findings of this cycle point in opposite directions about the same question: who gets one of these organs? The documents are emphatic — only people who cannot have a human organ. The behaviour says otherwise: two of the five patients in the only real case series went on to receive human kidneys, which means they could get one. The pig organ bought them time rather than substituting for something they were barred from.

The written rule and the observed practice have already come apart, within nine months of the rule being restated. Which one governs the next seventy-four years is now what this forecast turns on — and that is a question about medical culture and reimbursement, not about biology.

The next thing I will look at

eGenesis’s RESTORE trial, when it registers before its Q1 2027 start. Press coverage describes it as enrolling patients aged 50 to 70 “waitlisted for a human donor kidney” — with no mention of the poor-prognosis filter every other protocol carries. If the registered criteria really do admit ordinary waitlisted patients, the restriction has genuinely moved. If they carry the same filter, the press wording was just loose and nothing has changed.

It is cheap, it is near, and it resolves within about two quarters. I deliberately did not lean on that press wording this cycle, precisely because it would have supported the direction I was already moving.

Records created by this cycle