World-First Pig Kidney Transplant

In a world first, we heard last week that US surgeons had transplanted a kidney from a gene-edited pig into a living human.

CRISPR gene editing takes advantage of a system already found in nature. CRISPR’s “genetic scissors” evolved in bacteria and other microbes to help them fend off viruses. Their cellular machinery allows them to integrate and ultimately destroy viral DNA by cutting it.

A busy time for gene-edited xenotransplantation

While CRISPR editing has brought new hope to the possibility of xenotransplantation, even recent trials show great caution is still warranted.

In 2022 and 2023, two patients with terminal heart diseases, who were ineligible for traditional heart transplants, were granted regulatory permission to receive a gene-edited pig heart. These pig hearts had ten genome edits to make them more suitable for transplanting into humans. However, both patients died within several weeks of the procedures.

Earlier this month, we heard a team of surgeons in China transplanted a gene-edited pig liver into a clinically dead man (with family consent). The liver functioned well up until the ten-day limit of the trial.

From biotech dream to clinical reality

Only a few months ago, CRISPR gene editing made its debut in mainstream medicine. In November, drug regulators in the United Kingdom and US approved the world’s first CRISPR-based genome-editing therapy for human use – a treatment for life-threatening forms of sickle-cell disease.

How is this latest example different?

The gene-edited pig kidney was transplanted into a relatively young, living, legally competent and consenting adult.

We’ll be talking more about gene-editing

Medicine and gene technology regulators are increasingly asked to approve new experimental trials using gene editing and CRISPR. However, neither xenotransplantation nor the therapeutic applications of this technology lead to changes to the genome that can be inherited.

For this to occur, CRISPR edits would need to be applied to the cells at the earliest stages of their life, such as to early-stage embryonic cells in vitro (in the lab). In Australia, intentionally creating heritable alterations to the human genome is a criminal offence carrying 15 years’ imprisonment.

Even without creating inheritable gene changes, however, xenotransplantation using CRISPR is in its infancy. For all the promise of the headlines, there is not yet one example of a stable xenotransplantation in a living human lasting beyond seven months.

But the prospect of such trials would likely require significant improvements in current outcomes to gain regulatory approval in the US or elsewhere. By the same token, regulatory approval of any “off-the-shelf” xenotransplantation organs, including gene-edited kidneys, would seem some way off.

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