A kidney from a genetically modified pig has been transplanted into a living human being for the first time.

The organ had 69 genetic alterations to make it less porcine in appearance and safer for a human recipient.

The four-hour procedure took place on March 16 and was a success, with the patient said to be recovering well.

Richard “Rick” Slayman, 62, has diabetes, high blood pressure and end-stage kidney failure.

He had previously received a human kidney transplant from a deceased donor but that organ started to fail last year.

Doctors at Massachusetts General Hospital (MGH) in Boston recommended the xenotransplantation option to Mr Slayman as a possible route to avoid more dialysis and further deterioration.

Modified pig kidneys have been given to people before as part of pioneering experiments but all previous attempts were to brain-dead individuals being kept alive by machines and the procedures were purely experimental to test out the viability of the procedure.

Mr Slayman is in hospital and recovering well. He is on a pioneering cocktail of drugs – tegoprubart from Eledon Pharmaceuticals and ravulizumab-cwvz from Alexion Pharmaceuticals – which are designed to prevent his immune system from attacking and rejecting the foreign organ.

The procedure was performed under a single FDA expanded access protocol, known as compassionate use, which gives patients with life-threatening conditions a case-by-case approval to undergo experimental procedures as a last resort.

As the first person to ever undergo such a procedure, he is being closely monitored and his prognosis remains unknown.

Three previous experiments on braindead individuals saw the transplanted porcine kidneys lasting for 77 hours, seven days and 32 days.

Last year, Harvard scientists published data on transplantation experiments on monkeys. These monkeys were given organs from e-Genesis grown Yucatan miniature pigs and had the same 69 genetic tweaks.

Of the 20 crab-eating macaques in the study, half of the animals survived for more than a month; the average length of survival was 176 days. One monkey survived for 758 days.

In early 2022, a man from the US became the first living person to ever receive a pig heart as part of an experiment and under similar conditions where there were no other viable routes for treatment.

David Bennett died at the University of Maryland two months after the procedure which was described as a “shot in the dark”.

MGH was the site of the first ever human-to-human transplant in 70 years and this procedure has been described as “a historic milestone” that will provide a lifeline to millions of patients worldwide.

“We are grateful for the courageous contribution of the patient and to the advancement of transplantation science,” said Michael Curtis, chief executive officer of eGenesis, the company which grew the genetically modified pig that provided the organ for the surgery.

“This represents a new frontier in medicine and demonstrates the potential of genome engineering to change the lives of millions of patients globally suffering from kidney failure.”

Dr Nahel Elias, one of the surgeons for the latest transplantation, added: “This seminal transplant could not be possible without collaboration and effort from multiple teams and specialists at MGH including physicians, surgeons, scientists, anesthesiologists, and nurses.”

“They participated in coordinating the patient’s care in preparation for the transplant, seeing him through the surgery, and caring for him post-operatively,” said Dr Elias who is also the surgical director for kidney transplantation.

Dr Joren C Madsen, director of the MGH transplant centre, said: “The real hero today is the patient, Mr Slayman, as the success of this pioneering surgery, once deemed unimaginable, would not have been possible without his courage and willingness to embark on a journey into uncharted medical territory.”

Dr Madsen added that the patient “becomes a beacon of hope for countless individuals”.

The UK is behind the US in the field of xenotransplantation, with moral and ethical issues preventing it from taking off on the NHS.

Experts have called for a review of the technology and possibilities in order to help shorten wait list times for human organs.