Xenotransplantation – timeline
This timeline features some of the key events in xenotransplantation from the early 1900s onwards. For a more detailed history see our History of xenotransplantation article.
1902 – Reconnecting blood vessels for organ transplants
Alexis Carrel at the Rockefeller Institute in New York describes how blood vessels could be reconnected in transplanted organs. Carrel receives the Nobel prize for this work in 1912.
1902–1923 – First attempts at organ xenotransplants
Transplants with pig, goat, sheep and monkey organs are attempted, but all fail, with patients surviving only hours or days after transplantation. No further animal to human transplants are tried again until 1963, after immunosuppressing drugs are developed.
1944 – Immune system causes transplant rejection
Peter Medawar from the University of London shows that transplants are failing because of an immune system reaction.
1954 – First successful human to human transplant
First successful human to human transplant of a kidney between identical twin brothers.
1960 – Acquired immune tolerance
Peter Medawar receives the Nobel prize for discovering that it is possible to induce tolerance to transplanted tissue.
Peter Medawar
Sir Peter Medawar (1915–1987) was a highly influential scientist who, along with Sir Frank Macfarlane Burnet, received the Nobel Prize in Physiology or Medicine in 1960 for their discovery of acquired immunological tolerance.
1960 – First immunosuppressive drugs identified
A number of researchers independently demonstrate that a drug called 6-MP can delay rejection of tissue and organs transplanted between the same species.
1963 – Baboon kidney transplant
Baboon kidneys are transplanted into six patients in Denver by Dr Thomas Starzl. The patients survive between 19–98 days.
1963 – Chimpanzee kidney transplant
Chimpanzee kidneys are transplanted into 13 patients by Keith Reemtsma at Tulane University in Louisiana. One patient survives for 9 months.
1964 – Chimpanzee heart transplant
The first animal to human heart transplant is carried out by James Hardy at the University of Mississippi, but it fails rapidly.
1969–1974 – Chimpanzee liver transplant
The world’s first chimpanzee liver transplants are done on three children between 1969 and 1974 but none of them survives for more than 2 weeks.
1977 – Baboon and chimpanzee hearts used as back-up pumps
Christiaan Barnard uses baboon and chimpanzee hearts as temporary back-up pumps in two patients with heart failure after surgery, but the treatment does not help the patients survive.
1978 – Pig skin used to treat burns patients
Burns patients treated with pig skin grafts have faster healing times and less pain than patients treated with standard paraffin gauze dressings.
1984 – Baboon heart transplant in baby
Baby Fae, an infant born with a severe heart defect, receives a baboon heart, but only lives for 20 days after the transplant.
1992–1993 – Baboon to human liver transplant
Dr Thomas Starzl transplants baboon livers into two patients. One of the patients survives for 70 days with little evidence of rejection.
1995 – Transgenic pigs prevent transplant rejection
Dr David White in Cambridge, UK, creates transgenic pigs that have a human protein to prevent their tissues and organs being rejected by the immune system. Several other labs investigate similar strategies.
1995 – Baboon to human bone marrow transplant for HIV
Jeff Getty, a patient infected with human immunodeficiency virus (HIV), receives baboon bone marrow to treat his illness. Baboon bone marrow has a natural resistance to HIV. His symptoms improve for a while, but the baboon cells die after about 2 weeks.
1996 – Pig cell transplant for type 1 diabetes
Living Cell Technologies (now called Algorae Pharmaceuticals Ltd) transplants encapsulated pig islet cells into type 1 diabetic patient Michael Helyer. The treatment is successful and allows Michael to reduce insulin injections.
Find out more in the article, Trialling pig cell transplants.
1997 – Pig nerve cell transplants for Parkinson’s disease
Foetal pig nerve cells are used to treat patients with Parkinson’s disease with some success.
Xenotransplantation saves Jim
Injecting a human brain with pig cells — an example of science fiction, or modern medicine?
1997 – Pig liver used to keep patient alive
Robert Pennington, a 20-year-old with liver failure, is kept alive by passing his blood through transgenic pig livers, which had been genetically modified so they would not be recognised by the recipient’s immune system. This procedure is carried out for 7 hours over 3 days until a suitable liver becomes available. This procedure is done a few weeks before a worldwide ban on xenotransplants.
Xenotransplantation saves Robert
Filtering human blood through a pig's liver — science fiction, or modern medicine?
1997 – Worldwide ban on all xenotransplantation
Concerns about the risk of infecting human recipients with animal endogenous retroviruses lead to a worldwide ban or moratorium on animal to human transplants. Pig endogenous retrovirus (PERV) is of particular concern.
Pig cell transplants and PERV
Pig to human transplants, or xenotransplants, were banned in 1997 because of concerns about transmission of pig diseases to humans. This followed the discovery that pig endogenous retrovirus (PERV) from a pig cell line could infect human cells in a test tube. PERV is found in all pigs’ DNA as an inactive provirus, but it could potentially become active and release viral particles in other species. The pigs that LCT uses for transplant have PERV in very low amounts compared to other breeds. Since 1997, LCT and other research labs have shown that PERV does not infect human cells.
Questions to consider
What is unusual about PERV?
Why is it a concern for pig to human transplants?
Teaching points
Learn more about diseases that might be transmitted from pigs to humans.
See the article Pig viruses and pig testing.
1997–1999 – Risk of infectious disease assessed
Several groups publish findings showing no evidence of PERV infection in human recipients of pig tissues.
2000–2011 – Ban on xenotransplantation is lifted in some countries
The ban on xenotransplantation is lifted in some countries and applications for trials with xenotransplants are assessed on a case-by-case basis.
2007–2011 – Clinical trials of pig cell transplants continue
Russia, New Zealand and Argentina all approve clinical trials of pig cells for the treatment of type 1 diabetes. Find out more in the article Pig cell transplants.
Clinical trials of pig cell transplants
LCT is testing its encapsulated pig cell product DIABECELL in patients with a rare complication of type 1 diabetes called unaware hypoglycaemia. Patients with this complication are unable to tell when their blood sugar is low and may become unconscious before they realise. Clinical trials on a small number of patients with unaware hypoglycaemia have shown that the product is safe, can improve their blood sugar control and reduce the amount of insulin they need to inject.
2012–2017 – Clinical trials of pig cell transplants to treat Parkinson’s disease
New Zealand gives approval for transplanting pigs cells into human brains to treat Parkinson’s disease. Phase II tests are underway in 2016 and if these are succesful LCT will apply to launch their treatment in 2017.
2022 – First heart transplant from a genetically modified pig
A US man became the first person in the world to get a heart transplant from a genetically-modified pig. Doctors were granted a special dispensation by the US medical regulator to carry out the procedure, on the basis that the patient would otherwise have died. The patient survived for 2 months after the transplant.
World-first heart transplant
On 7 January 2022, Professor Bartley P Griffith performed the first successful transplant of a genetically modified pig heart to a human.
2024 – First genetically modified pig transplant
In March 2024 surgeons at a hospital in Massachusetts, United States, transplanted the kidney of a genetically modified pig into a human recipient.
