This timeline features some of the key events in xenotransplantation from the early 1900s until 2017.
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.
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 (formerly Diacrin) 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.
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.
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.
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.
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.
