Continue to raise awareness to encourage the increase of donors. And, consequently, of transplants. But to allow all people waiting for an organ to have it quickly, we need to start exploring new opportunities. Like xenotransplants, or the use of organs of living beings belonging to different species. The growing pressure is recorded in the United States. The Food and Drug Administration (the federal agency that deals with the use of new drugs, medical devices and therapies, including transplants) is in fact evaluating the opportunity to authorize the first clinical trials to evaluate the safety and effectiveness of these procedures.
“The high safety profile of transplants has contributed to raising citizens’ awareness on these issues – he explains Wilson Bryan, the director of the transplantation and advanced therapies department of the FDA -. The time is right to start a comparison also on xenotransplants “.
The first clinical trials
The issue was the subject of an in-depth study on Nature, which reconstructed the comparison between the experts of the US regulatory body and the main specialists involved in the field of transplant surgery. If the interest of the latter in the practice was already known, what was surprising was the opening by the FDA. No gambling, but the desire to understand each other more was common. “The data available today support the launch of small trials aimed at a very select audience of patients,” he explained Allan Kirk, Duke University (Durham) transplant immunology expert, after attending the meeting. Without clinical trials, on the other hand, it will be almost impossible to answer the many questions concerning this possible therapeutic solution. A hypothesis at the moment to come. But whose fallout could be significant.
Contaminated by animal viruses: this is why the first transplanted pig heart died
Xenotransplantation: a history that has lasted for over three centuries
The transplantation of organs, tissues or cells between organisms of different species is an experimental procedure that aims to identify new sources with which to address the shortage of organs. The first reference dates back to 1667, in the context of a blood transfusion from a lamb to a man. The clinical use of animal organs was instead documented for the first time in 1905: with the transfer of a kidney from rabbit to man. Since then, several studies have been conducted considering non-human primates as donors: leveraging on the genetic ‘similarity’ that could have mitigated the risk of rejection. Other reasons (from the high risk of transmitting infections to differences in organ size, up to ethical concerns) have however prompted the scientific community to evaluate pigs as possible organ donors for humans.
Pigs first choice
Some positive findings, especially at the preclinical level, lead today to consider pigs as a probable ‘first choice’ due to the size of the animals and their physiological similarity to humans, the short period of pregnancy and the relatively large size of the pigs. at birth (an aspect that would make the number of potential donors large), the low risk of transmission of zoonoses and the possibility of intervening on the genome of these animals to reduce the risk of organ rejection.
The open questions
Could the organ of a pig be able to guarantee continuity in the life of a man who, alternatively, would be destined to die? According to US experts, the answer is almost certainly yes. And at this point it is sought without excluding any possibility. “If the ultimate goal is to be able to take an organ from a pig and transplant it into a human, the start of one or more trials is necessary,” says the veterinarian. Caroline Zeiss, professor of Comparative Anatomy and Clinical Pathology at Yale University. The open questions, on the other hand, are manifold. And they range, as it was rebuilt on Nature, from “defining the best immunosuppressive cocktail to allow humans to accept organ from another species” to “managing the infectious risk”. Infectious screening and rejection are the most difficult obstacles to overcome.
First patient with a pig’s heart died
In the wake of what happened a few months ago with the failure of the first heart xenograft, Zeiss explains: “One of the first steps to be taken is to improve viral screening procedures. Validated tests are needed to prevent silent infections, such as that from cytomegalovirus, lead to the election of infected animals as donors “. Without neglecting other aspects, such as “the selection of the most suitable pig species to apply for the role of donor” and “the management of any other chronic diseases in patients”. Several companies, which have long been engaged in studying the ‘corrections’ to be made to pig DNA to make them suitable for organ donation for humans, are also looking with interest at the possible start of the first trials.
In Italy, over 8,000 patients waiting for an organ
Meanwhile, the data of the complete report of the National Transplant Center on the activity carried out in 2021 arrive. As of December 31 last year, 8,065 patients were waiting for an organ. A figure down by almost 3% compared to 2020: a sign of a full recovery in activity, after the hardest months of the pandemic. As for the average times, he expects more for the heart (3.7 years), less for the liver (1.7 years). Periods during which some patients can leave the waiting lists due to death or the compromise of their physical condition to the point that transplantation is no longer feasible.