What is Xenotransplantation?
Xenotransplantation is the process of transplanting organs, tissues, or cells from one species to another. Scientists are exploring the use of pig organs for human transplantation because pigs have organs that are similar in size and function to human organs. This research is helping to address the shortage of human donor organs.
Why Pigs?
Pigs have been chosen for xenotransplantation for several reasons: Their organ size and function are close to that of humans; they reproduce quickly, allowing for a steady supply of organs; and scientists can genetically modify pigs to make their organs more compatible with the human immune system. Additionally, pig-derived medical products such as heart valves, insulin, and skin grafts have been used successfully in humans for decades.
What This Means for Patients
Patients who are not eligible for human transplants due to medical complexity may benefit from xenotransplants in the future. If xenotransplantation becomes widely available, it could mean:
- More available organs for patients on the transplant waitlist.
- Potentially faster access to life-saving transplants.
Where Are Pig Organs and Tissues Already Being Used?
While full organ transplants from pigs to humans are still in the early stage, some pig-derived tissues and cells are already being used in medical treatments, including:
- Heart Valves: Pig heart valves have been successfully implanted in humans for decades and are commonly used in valve replacement surgeries.
- Skin Grafts: Pig skin is used as a temporary covering for burn victims while waiting for human skin grafts.
- Corneal Transplants: Pig corneas are being explored as a treatment option for human eye diseases.
- Pancreatic Cells: Pig-derived pancreatic cells are being researched for their potential in treating type 1 diabetes by producing insulin in humans.
A Brief History of Xenotransplantation
Xenotransplantation is not a new concept. Scientists and doctors have been exploring the possibility of using animal organs in humans for over a century. Here are some key milestones:
- 1905: French surgeon Mathieu Jaboulay attempted the first xenotransplants by using pig and goat kidneys in human patients. However, these early attempts failed due to immediate rejection.
- 1963: Dr. Keith Reemtsma at Tulane University transplanted chimpanzee kidneys into humans. One patient survived for nine months before succumbing to organ rejection.
- 1984: Baby Fae, an infant born with a fatal heart defect, received a baboon heart transplant. Unfortunately, she only survived for 21 days due to immune rejection.
- 1990s: Advances in immunosuppressive drugs and genetic engineering improved the chances of xenotransplantation success.
- 2010s: Scientists began developing genetically modified pigs to remove the sugar molecule Gal-1,3-Gal, which triggers human immune rejection.
- 2022: A genetically modified pig heart was successfully transplanted into a human patient for the first time. The patient survived for two months, marking a significant milestone in xenotransplantation research.
- 2024:
- March: Richard Slayman became the first person to receive a genetically modified pig kidney transplant at Massachusetts General Hospital. The kidney functioned well, though he passed away in May from unrelated causes.
- April: Lisa Pisano underwent a pig kidney transplant combined with a heart pump at NYU Langone Health. The kidney was later removed after 47 days.
- November: Towana Looney, a dialysis patient for eight years, received a pig kidney transplant at NYU Langone Health. Her kidney was removed after 4 months.
- December: eGenesis received FDA approval to perform up to three pig‐kidney transplants in humans under a Compassionate Use (Expanded Access) protocol. This clearance allowed them to proceed with individual transplants before starting formal clinical trials.
- 2025:
- January: Tim Andrews received a pig kidney transplant at Massachusetts General Hospital. The kidney lasted a record 271 before being removed. Andrews has returned to dialysis.
- February: United Therapeutics received FDA clearance to begin clinical trials on gene-edited pig kidneys, with the first human transplant expected in mid-2025.
- June: Bill Stewart received a pig kidney transplant at Massachusetts General Hospital. As of October 2025, the kidney is functioning well.
- September: A new eGenesis trial is approved to provide gene-edited pig kidney transplants to 30 people age 50 or older who are on dialysis and the transplant list. Another developer of gene-edited pig organs, United Therapeutics, is about to start enrolling people in a similar FDA-approved study.
Key Players in Xenotransplantation Today
Several institutions are leading the way in xenotransplantation research:
- Massachusetts General Hospital (MGH): Conducted the first pig kidney transplant in a living human (2024) and continues to perform pig transplant and clinical research.
- NYU Langone Health: Has performed multiple pig kidney transplants and continues clinical research.
- University of Maryland Medical Center: Conducted the first pig heart transplant in a human in 2022 and continues xenotransplantation research.
- Columbia University: As part of its Kidney and Pancreas Transplant Program, scientists are conducting research across immunology and xenotransplantation to achieve induction of xenograft tolerance.
The Biggest Challenge: Organ Rejection
One of the main obstacles in xenotransplantation is that the human immune system sees pig organs as foreign and attacks them immediately, a reaction called hyperacute rejection. This is mainly because pig cells have a sugar molecule called Gal-1,3-Gal, which human bodies recognize as a threat. Rejection isn’t just immune-based — coagulation (blood clotting) is also a key hurdle in pig-to-human transplants.
How Scientists Are Solving This Problem
Researchers have developed several strategies to overcome rejection:
- Genetic Modification of Pigs – Scientists have removed the Gal-1,3-Gal sugar from pig cells using gene-editing technology. This makes pig organs less likely to trigger an immune attack.
- Improving Immune Compatibility – By selectively breeding pigs with certain immune system traits, scientists have increased the success rate of organ acceptance in animal studies.
- Short-Term Immunosuppression – Just like with human organ transplants, medications can be used to temporarily suppress the immune system and help the body accept the new organ.
Where Are We Now?
As of 2025, several patients have received genetically modified pig kidneys that functioned without hyperacute rejection, marking significant progress. Xenotransplantation is still in the early stage, but progress is being made. Recent studies have shown that genetically modified pig kidneys and hearts can function in human recipients for extended periods. Researchers continue to refine the process to make xenotransplantation safer and more effective.
What’s Next?
Ongoing research is focusing on:
- Further improving genetic modifications to prevent rejection.
- Ensuring long-term survival of transplanted pig organs in human patients.
- Understanding how xenotransplantation might impact overall health and longevity.
- Immunology and tolerance to reduce (or eliminate) the need for immunosuppressive medication (moonshot goal!)
Final Thoughts
Xenotransplantation has the potential to revolutionize organ transplantation, offering hope to patients in need of life-saving organs. The goal is not to replace human donors, but to expand access and save lives where human options fall short. While it is not yet widely available, rapid advancements in research are bringing us closer to making it a reality.
Justin is the Director of External Affairs at OpenBiome, overseeing all outward facing
communications, including to researchers, clinicians, patients, media, and the general
public.
Before joining OpenBiome, Justin completed a PhD in the MIT Department of Biology in
2018 where he used frog embryos to model human face development. At OpenBiome,
Justin is excited to be combining his passions for science and communication, and to be
part of a team accelerating microbiome research to improve heath for all.
Michael is an Executive Director leading Digital Health within the Business Development Innovative Technologies function at Bristol Myers Squibb. Michael is responsible for evaluation and execution of Business Development investments and transactions in support of Digital Innovation priorities at BMS.
During his 28 years at Bristol Myers Squibb, Michael has worked across Europe, Asia Pacific and the US in a variety of roles leading and developing high performing, diverse teams, while growing his responsibility and knowledge of the Biopharmaceutical Industry.
Prior to his current role, Michael had responsibility for Alliance Management with a specific focus on late-stage partnerships including: clinical collaborations, translational medicine and diagnostics partnerships, digital partnerships as well as commercial alliances.
Michael has also held roles at BMS responsible for oversight of IT, Infrastructure, and adjacent services in support of Business Development priorities (M&A, divestitures, strategic alliances, collaborations and licensing) at Bristol Myers Squibb. This involved the full spectrum of the deal lifecycle from pre-deal diligence, operational and synergy reviews, ‘Day-1’ planning and post-deal implementation support.
In addition to his IT/Corporate Services experience in supporting Business Development, Michael has supported Manufacturing Operations Globally, Product & Process Development, Engineering & Quality functions.
Michael began his career in Ireland as Chemist with Bristol Myers Squibb in 1994, after completing his Bachelor of Science Degree in Industrial Chemistry and Business Administration postgraduate studies. Michael currently resides in Princeton, NJ.
Sophie M. Balzora MD, FACG, is a Clinical Associate Professor at the NYU Grossman School of Medicine. Dr. Balzora has focused her academic efforts on improving physician engagement and enhancing the patient experience through objective structured clinical exams (OSCEs).
As Chair of ACG’s Public Relations Committee, Dr. Balzora’s primary goal is to disseminate the College’s message of the importance of colorectal cancer awareness to the general public and arm its members with tools to do the same. She is a member and incoming Vice Chair of ACG’s Diversity, Equity, and Inclusion Committee, and co-founder of ACG’s #DiversityinGI Social Media Campaign. In October 2020, her work in the College has been recognized with the ACG President’s Special Recognition Award.
Dr. Balzora serves on the Patient Education Sub-Committee of the Crohn’s and Colitis Foundation (CCF)’s National Scientific Advisory Committee, the social media team of the CCF’s Inflammatory Bowel Disease (IBD) Journal, and as a member of Fight CRC’s Health Equity Committee. She has also recently been accepted into the inaugural cohort of the Office of Diversity Affairs’ Faculty Leadership Development Program through the NYU Langone Academy.
Dr. Wyborski received his B.S. (Chemistry) from the University of Notre Dame and his doctorate (Biochemistry) from Indiana University (Bloomington). He completed a postdoctoral fellowship focused on neuronal gene expression in the lab of Dr. David Gottlieb in the Department of Neuroscience at Washington University at St. Louis School of Medicine.
Dr. Wyborski is currently the Director of IBD Ventures Investments at the Crohn’s and Colitis Foundation where he oversees a growing portfolio of therapeutics, devices, diagnostics, and digital health applications focused on improving IBD patients’ lives. He began his drug development career at Pfizer where he conducted preclinical research in the therapeutic areas of neuroscience, cardiovascular, and inflammation. He led discovery programs in neurotrophic factors, nuclear receptors, and kinases. After his time at Pfizer, he led a research group in the consumer product field by developing products for skin care. Prior to coming to the Foundation, Russ was a Director of Technical Operations at BioMotiv, a start-up company which functioned as a Drug Development Accelerator in Cleveland, OH. In this role, he conducted technical diligence on potential new investments while leading a company (Koutif Therapeutics) through IND filing for an inhibitor of an E3 Ligase for Crohn’s Disease. He has consulted for several academic technology transfer offices at institutions such as the University of Pittsburgh, Cleveland Clinic, Case Western Reserve University and Cincinnati Children’s Hospital Medical Center. He is passionate about accelerating the development of novel therapeutics for patient’s unmet needs.
Tina Aswani-Omprakash is an award-winning Crohn’s advocate and patient leader based out of New York City. Tina maintains a blog and advocacy platform called Own Your Crohn’s (https://ownyourcrohns.com) and co-founded South Asian IBD Alliance (SAIA) (https://www.southasianibd.org/) to form a patient-clinician led non-profit initiative in order to minimize disparities and improve education in the growing South Asian IBD population.
Tina’s overarching aim is to normalize the rhetoric around chronic illnesses and disabilities in order to help diverse groups of patients own their ailments to live fuller, happier lives. Via her writing, lobbying, social media advocacy and speaking engagements, she spearheads public health causes, including those proposing research for and creating awareness for IBD, life-saving ostomy surgery, fistulizing disease and initiatives supporting health equity for women and racial & ethnic minorities.
Tina is pursuing her Master’s degree in Public Health at Mount Sinai’s Icahn School of Medicine and will be graduating in 2023. Additionally, she has spoken at many premier GI conferences worldwide and has co-authored several research papers in prominent journals (JAMA, Gastroenterology, Crohn’s & Colitis 360), a guidebook on IBD care and a series of websites on Crohn’s-related ostomy surgery. Tina does consulting work as a patient advisor for non-profits, clinical research organizations as well as ostomy manufacturers, in addition to pharmaceutical and digital health companies. Her aim is to help companies recognize disparities and unmet needs in minority health populations.
Tina has been featured in The New York Times, on the cover of American College of Gastroenterology (ACG) Magazine and in Gastroenterology & Endoscopy News as well as Health Magazine for her trailblazing advocacy work. The Crohn’s & Colitis Foundation recognized Tina in 2021 for her phenomenal leadership and powerful impact on the IBD community with the Above & Beyond Volunteer Award. Tina’s blog was also recognized as a 2020 Best Blog by Healthline and she was awarded the 2019 Healio Gastroenterology Disruptive Innovator Award by ACG for moving the needle on GI care for patients.