First Pig Kidney Transplant in Living Patient

In March 2024, medical history was made at Massachusetts General Hospital in Boston. Surgeons successfully transplanted a genetically modified pig kidney into a 62-year-old man named Richard Slayman. This event marks a major turning point in the field of xenotransplantation and offers potential solutions to the global organ shortage crisis.

A Landmark Procedure at Mass General

The surgery took place on March 16, 2024, and lasted approximately four hours. It was led by Dr. Tatsuo Kawai, the director of the Legorreta Center for Clinical Transplant Tolerance, alongside Dr. Nahel Elias. The patient, Richard “Rick” Slayman of Weymouth, Massachusetts, was suffering from end-stage renal disease.

This operation was distinct from previous experiments. Before this surgery, pig kidneys had only been transplanted into brain-dead decedents maintained on ventilators for research purposes. This was the first time such an organ was placed inside a living, breathing patient with the intent of long-term survival.

Mr. Slayman had previously received a human kidney transplant in 2018. However, that organ began to fail roughly five years later, forcing him to resume dialysis treatments. With limited options and facing the severe physical toll of dialysis, Slayman volunteered for this experimental procedure under the FDA’s “compassionate use” protocol. This protocol allows patients with life-threatening conditions to access experimental treatments when no other comparable therapies are available.

The Science: Inside the Genetically Edited Organ

The success of this transplant relied heavily on advanced genetic engineering. The kidney was provided by eGenesis, a biotechnology company based in Cambridge, Massachusetts. Standard pig organs cannot be used in humans because the human immune system recognizes them as foreign tissue immediately. This triggers a rapid and often fatal rejection known as hyperacute rejection.

To solve this, scientists used CRISPR-Cas9 gene-editing technology to alter the pig’s DNA. The donor pig underwent a total of 69 genomic edits to make the organ compatible with a human body.

The Breakdown of the Genetic Edits

The 69 edits performed by eGenesis can be categorized into three specific goals:

• Removing Harmful Pig Genes: Three genes responsible for the rapid rejection of pig organs by humans were knocked out (removed). These genes produce sugars on the surface of pig cells that the human immune system attacks.
• Adding Human Genes: Seven human transgenes were inserted into the pig’s genome. These genes help regulate pathways related to inflammation, blood coagulation, and immune rejection. Essentially, they act as camouflage to make the pig kidney look more “human” to the recipient’s body.
• Inactivating Retroviruses: The remaining 59 edits were focused on inactivating porcine endogenous retroviruses (PERVs). These are viruses inherent in the pig’s DNA. While harmless to pigs, there is a theoretical risk they could infect humans. These edits were a crucial safety measure to prevent cross-species infection.

Immediate Results and Initial Success

The surgical team reported that the kidney began functioning almost immediately. Before the surgery was even finished, the organ turned pink and started producing urine. This immediate function is a critical indicator of success in transplant surgery.

Mr. Slayman recovered well enough to be discharged from the hospital just two weeks after the operation. Mass General doctors noted that he was leaving the hospital with the cleanest bill of health he had experienced in a long time. At the time of his discharge, he was not on dialysis, proving the pig kidney was effectively filtering waste from his blood.

Tragic Outcome and Medical Context

Sadly, approximately two months after the surgery, Richard Slayman passed away in May 2024. However, it is vital to understand the context of his death regarding the procedure.

Massachusetts General Hospital released a statement clarifying that there was no indication his death was the result of the transplant itself. Mr. Slayman had a complex medical history involving Type 2 diabetes and hypertension, which are common comorbidities for patients with end-stage renal disease. While he did not survive long-term, the fact that the organ functioned for two months without immediate rejection provided invaluable data to the medical community. It proved that a genetically edited kidney could sustain a human life outside of a clinical trial setting.

Addressing the Organ Shortage Crisis

The driving force behind this high-stakes research is the severe lack of human organs available for transplant. According to the United Network for Organ Sharing (UNOS), more than 100,000 people in the United States are currently on the waiting list for an organ transplant.

The statistics highlight the urgency of this research:

• Kidney Demand: The vast majority of patients on the waiting list require a kidney.
• Daily Fatalities: roughly 17 people die every day in the U.S. while waiting for an organ transplant.
• Dialysis Limitations: While dialysis keeps patients alive, it is not a cure. It is physically demanding, time-consuming, and only does a fraction of the work a healthy kidney performs.

Xenotransplantation represents the most promising supply chain solution. If pigs can be raised specifically for organ donation, the waiting list could theoretically be eliminated. This would allow patients to receive organs preemptively rather than waiting until they are critically ill.

Comparisons to Other Xenotransplants

The Mass General surgery is part of a broader wave of progress.

• University of Maryland Medicine: In 2022 and 2023, surgeons here performed the first and second pig heart transplants into living patients (David Bennett and Lawrence Faucette). Both patients lived for several weeks before passing away, but the surgeries advanced the understanding of cardiac xenotransplantation.
• NYU Langone and UAB: Researchers at these institutions have successfully attached pig kidneys to brain-dead recipients. These experiments were crucial stepping stones that established the safety protocols used for Mr. Slayman.

What Comes Next?

The procedure at Mass General has paved the way for larger clinical trials. eGenesis and other biotech firms are working toward full FDA approval to run formal studies. These trials will likely involve more diverse patient groups to test the longevity and reliability of the organs.

Researchers are also looking at different combinations of immunosuppressive drugs. Even with genetic editing, patients receiving pig organs still require novel drug regimens to suppress the immune system. Finding the perfect balance between preventing rejection and fighting off infection remains the primary challenge for the next phase of research.

Frequently Asked Questions

Did the patient’s body reject the kidney? While Richard Slayman eventually passed away, the hospital stated there was no immediate indication that the transplant caused his death. The kidney functioned and produced urine, suggesting that hyperacute rejection was successfully avoided.

Why are pigs used for these transplants? Pigs are the preferred candidate for xenotransplantation because their organs are roughly the same size as human organs. Additionally, pigs reproduce quickly and are already raised for food, making them easier to breed for medical purposes compared to primates.

Is this procedure available to the public? No. This surgery was performed under a special “compassionate use” authorization from the FDA. It is not yet a standard medical treatment. It will likely take years of clinical trials before this becomes a routine option for patients on the waiting list.

What is CRISPR? CRISPR is a gene-editing tool that acts like a pair of molecular scissors. Scientists use it to cut specific strands of DNA. In this case, it was used to remove pig genes that cause rejection and insert human genes to improve compatibility.

Who funded this research? Much of the foundational research was supported by biotech companies like eGenesis, as well as grants from organizations looking to solve the organ shortage crisis. Mass General Hospital and its transplant center led the clinical execution.