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A 54-year-old New Jersey woman has become the first-ever patient to undergo combined mechanical heart pump and gene-edited pig kidney transplant surgery, doctors .

The patient, Lisa Pisano, had heart failure and end-stage kidney disease that required routine dialysis. She was not considered a candidate for human heart and kidney transplant due to her having several chronic medical conditions that made a good outcome unlikely.

Surgeons at NYU Langone Health in New York City offered her procedures in two stages. On April 4, they implanted a left ventricular assist device (LVAD). Then, on April 12, she got a xenotransplant using a gene-edited pig kidney.

The transplant was performed under the auspices of the FDA expanded access protocol, also known as "compassionate use," in which the agency allows patients with no other treatment options to try investigational therapies.

"Without the possibility of a kidney transplant, she would not have been eligible as a candidate for an LVAD due to the high mortality in patients on dialysis with heart pumps," said Nader Moazami, MD, of NYU Grossman School of Medicine, who led the heart pump procedure, in a statement. "This unique approach is the first time in the world that LVAD surgery has been done on a dialysis patient with a subsequent plan to transplant a kidney. The measure for success is a chance at a better quality of life and to give Lisa more time to spend with her family."

The kidney transplant, led by Robert Montgomery, MD, DPhil, director of the NYU Langone Transplant Institute, used a pig kidney genetically engineered to knock out the alpha-gal gene. The donor pig's thymus gland was also surgically placed under the covering of the kidney to reduce the chance of rejection. Combined, the xenokidney and the thymus tissue are called a developed by the United Therapeutics Corporation.

The xenotransplant marked the first documented instance of a mechanical heart pump recipient receiving an organ transplant of any kind.

This was the sixth human xenotransplant surgery performed by the NYU Langone Transplant Institute. Montgomery's team previously performed five xenotransplants into brain-dead individuals, but this was the institution's first attempt at transplanting into a living human.

Just last month, a team at Massachusetts General Hospital performed the world's first successful transplant of a gene-edited pig kidney into a 62-year-old man with end-stage kidney disease. This pig kidney had 69 genomic edits using CRISPR-Cas9 technology.

"We believe that kind of less is more," Montgomery said during a press conference. "The main gene edit that has been introduced into the pigs and the organs that we've been using is the fundamental problem and most of those other edits can be replaced by medications that are available to humans."

He added that adding in the thymus tissue aspect of the xenotransplant, which helps to boost some degree of tolerance and reduce immunosuppression, also differentiates their strategy from the Mass General team's method.

"I think our two biggest problems in transplantation right now are organ supply, and then for the few lucky people who are able to receive an organ, it's the complications -- the long-term complications of the drugs that they have to take in order to not reject those organs," said Montgomery. "I feel that the kidney transplant that we did is a substantial move in the direction in solving both of the largest unmet needs in transplantation."

As more cases of pig kidney xenotransplants are performed under compassionate use clearance, Montgomery said the hopes of testing this in clinical trials is getting "closer and closer."

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