Organ Transplants From Pigs Progress: A New Era in Xenotransplantation

The shortage of available human organs for transplant has been a medical crisis for decades. However, 2024 marked a historic turning point in the field of xenotransplantation, the process of transplanting organs from one species to another. With the first successful transplants of gene-edited pig kidneys into living human recipients, science is moving closer to a sustainable solution for end-stage organ failure.

The Breakthrough Cases of 2024

For years, scientists tested pig organs on non-human primates or brain-dead human bodies to assess safety. That changed dramatically in March 2024. Surgeons at Massachusetts General Hospital performed the world’s first transplant of a genetically edited pig kidney into a living patient, 62-year-old Richard Slayman.

Mr. Slayman, who was suffering from end-stage kidney disease, received the organ under the FDA’s “compassionate use” protocol. This rule allows patients with life-threatening conditions to access experimental treatments when no other options exist. Remarkably, the kidney began producing urine and filtering waste almost immediately. Mr. Slayman was discharged from the hospital two weeks later, marking a monumental success for the field. Although he passed away in May 2024 due to underlying health issues, the hospital noted there was no indication that the transplant itself was the cause of death.

Shortly after, in April 2024, surgeons at NYU Langone Health performed a similar procedure on Lisa Pisano. She received both a pig kidney and a mechanical heart pump. While the organ functioned for 47 days, it had to be removed due to limited blood flow related to the heart pump, not rejection of the organ itself. These two cases have provided invaluable data that animal trials simply could not offer.

How Gene Editing Makes It Possible

Pig organs are anatomically similar to human organs in size and function, making them the ideal candidate for xenotransplantation. However, the human immune system is designed to attack foreign tissue instantly. To solve this, scientists rely on advanced gene-editing technology, specifically CRISPR-Cas9.

The kidneys used in these recent surgeries were provided by eGenesis, a biotechnology company based in Cambridge, Massachusetts. eGenesis did not just make minor tweaks; they engineered a pig donor with 69 specific genomic edits.

The editing process involves three critical steps:

• Knock-Outs: Scientists remove (or “knock out”) three genes responsible for the rapid production of sugars found on the surface of pig cells. These sugars are what usually trigger an immediate, hyper-acute rejection by the human immune system.
• Knock-Ins: To make the organ appear “friendlier” to the body, scientists insert (or “knock in”) seven human genes involved in regulating inflammation and immunity. This helps the organ survive long-term.
• Viral Safety: The remaining 59 edits involve inactivating porcine endogenous retroviruses (PERVs). These are viral remnants hidden in pig DNA that could potentially jump to humans. eGenesis successfully neutralized these risks to prevent zoonotic infection.

The Companies and Hospitals Leading the Charge

This medical revolution is a collaborative effort between top-tier academic medical centers and private biotechnology firms.

eGenesis is currently the primary supplier for these high-complexity gene-edited kidneys. Their approach differs slightly from Revivicor, a subsidiary of United Therapeutics. Revivicor was responsible for providing the genetically modified pig hearts used in transplants at the University of Maryland Medical Center in 2022 and 2023. While Revivicor focuses on a “10-gene” pig (removing the alpha-gal sugar and adding human regulators), eGenesis focuses on the more extensive 69-edit model to ensure viral safety.

On the clinical side, three institutions are at the forefront:

1. Massachusetts General Hospital: Performed the first living kidney transplant.
2. NYU Langone Health: Performed the second living kidney transplant and has conducted extensive studies on brain-dead decedents.
3. University of Alabama at Birmingham (UAB): UAB has been instrumental in running pre-clinical trials, specifically the “Parsons Model,” where pig kidneys were tested in brain-dead recipients to establish safety protocols before moving to living patients.

Addressing the Organ Shortage Crisis

The driving force behind this research is sheer necessity. According to the Health Resources and Services Administration, over 103,000 men, women, and children are on the national transplant waiting list in the United States. Seventeen people die every day waiting for an organ transplant.

Kidneys are in the highest demand. Roughly 85% of patients on the waiting list need a kidney. Dialysis serves as a treatment, but it is physically demanding and significantly lowers a patient’s quality of life compared to a functioning transplant.

If xenotransplantation becomes FDA-approved for general use, it could transform the supply chain. Pig kidneys could serve as a “bridge to transplant,” keeping a patient alive until a human organ becomes available. Eventually, they could become “destination therapy,” meaning the pig organ serves as the permanent replacement.

Remaining Challenges and Future Outlook

Despite the excitement, significant hurdles remain. The recent deaths of the first recipients, while not directly attributed to immediate organ rejection, highlight the fragility of the patients usually selected for these trials. These patients often have multiple severe comorbidities (heart failure, diabetes) that complicate recovery.

Doctors are also still learning the optimal immunosuppression regimen. Because the organs are not human, standard anti-rejection drugs may need to be paired with newer agents, such as tegoprubart, an experimental antibody used in recent trials to protect the pig kidney.

The next step is formally structured clinical trials. Instead of one-off compassionate use cases, hospitals plan to enroll small groups of patients to gather standardized data. If these trials prove successful, we could see gene-edited pig organs becoming a standard medical resource within the next decade.

Frequently Asked Questions

Why are pigs used for transplants instead of monkeys? Pigs are preferred because their organs grow to human size quickly (within six months) and they are already raised for food, which presents fewer ethical concerns compared to using non-human primates. Additionally, primates pose a higher risk of transmitting diseases to humans.

Is it safe to receive a pig organ? Recent advances have significantly improved safety. By using gene editing to remove retroviruses and immune-triggering sugars, the risk of immediate rejection and infection has been lowered. However, it is still an experimental procedure with risks involving long-term rejection and immune complications.

How much does a pig kidney transplant cost? Currently, these are experimental procedures covered by research grants or hospital funding. There is no set commercial price yet. If approved, the cost would likely be comparable to human organ transplants, potentially saving money long-term by reducing the need for years of expensive dialysis.

When will this be available to the public? It will likely take several years of clinical trials before xenotransplantation is widely available. Experts remain cautiously optimistic that it could become a routine option for high-risk patients by the late 2020s or early 2030s.