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 The procedure done at NYU Langone Health in New York City involved
use of a pig whose genes had been altered so that its tissues no
longer contained a molecule known to trigger almost immediate
rejection.
The recipient was a brain-dead patient with signs of kidney
dysfunction whose family consented to the experiment before she was
due to be taken off of life support, researchers told Reuters.
For three days, the new kidney was attached to her blood vessels and
maintained outside her body, giving researchers access to it.
Test results of the transplanted kidney's function "looked pretty
normal," said transplant surgeon Dr. Robert Montgomery, who led the
study.
The kidney made "the amount of urine that you would expect" from a
transplanted human kidney, he said, and there was no evidence of the
vigorous, early rejection seen when unmodified pig kidneys are
transplanted into non-human primates.
The recipient's abnormal creatinine level - an indicator of poor
kidney function - returned to normal after the transplant,
Montgomery said.
In the United States, nearly 107,000 people are presently waiting
for organ transplants, including more than 90,000 awaiting a kidney,
according to the United Network for Organ Sharing. Wait times for a
kidney average three-to-five years.
Researchers have been working for decades on the possibility of
using animal organs for transplants, but have been stymied over how
to prevent immediate rejection by the human body.
Montgomery's team theorized that knocking out the pig gene for a
carbohydrate that triggers rejection - a sugar molecule, or glycan,
called alpha-gal - would prevent the problem.
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 The genetically altered pig,
dubbed GalSafe, was developed by United
Therapeutics Corp's Revivicor unit. It was
approved by the U.S. Food and Drug
Administration in December 2020, for use as food
for people with a meat allergy and as a
potential source of human therapeutics.
Medical products developed from the pigs would
still require specific FDA approval before being
used in humans, the agency said.
Other researchers are considering whether
GalSafe pigs can be sources of everything from
heart valves to skin grafts for human patients.
The NYU kidney transplant experiment should pave
the way for trials in patients with end-stage
kidney failure, possibly in the next year or
two, said Montgomery, himself a heart transplant
recipient. Those trials might test the approach
as a short-term solution for critically ill
patients until a human kidney becomes available,
or as a permanent graft.
The current experiment involved a single
transplant, and the kidney was left in place for
only three days, so any future trials are likely
to uncover new barriers that will need to be
overcome, Montgomery said. Participants would
probably be patients with low odds of receiving
a human kidney and a poor prognosis on dialysis.
"For a lot of those people, the mortality rate
is as high as it is for some cancers, and we
don't think twice about using new drugs and
doing new trials (in cancer patients) when it
might give them a couple of months more of
life," Montgomery said.
The researchers worked with medical ethicists,
legal and religious experts to vet the concept
before asking a family for temporary access to a
brain-dead patient, Montgomery said.
(Reporting by Nancy Lapid; Editing by Michele
Gershberg and Bill Berkrot)
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