Three-quarters of kidney transplant patients who received stem cells from their organ donors successfully stopped taking immunosuppressive medications for more than two years—a medical achievement that could transform how transplants are managed.
The phase 3 clinical trial results, published in the American Journal of Transplantation, offer hope for thousands of transplant recipients who currently face a lifetime of harsh side effects from anti-rejection drugs.
The innovative approach combines a kidney transplant with an infusion of the donor’s stem cells, essentially teaching the recipient’s immune system to accept the new organ as its own. Of the 20 participants who received this dual treatment, 19 successfully discontinued all immunosuppressive medications approximately one year after their transplant.
The Challenge of Current Treatment
Traditional organ transplantation requires recipients to take immunosuppressive medications indefinitely to prevent their immune systems from attacking the transplanted organ. These drugs come with significant costs: increased susceptibility to infections and cancer, plus side effects ranging from headaches and tremors to more serious complications.
“I’ve been involved in transplant research for more than 30 years, and we’ve done quite a few amazing things. But in the scheme of things, this research is right at the very top,” noted Dr. Mark Stegall, a co-author of the study from Mayo Clinic. “It’s been a goal — to be able to safely get transplant recipients off immunosuppression — for longer than I’ve been doing this.”
How the Treatment Works
The study involved kidney recipients and their sibling donors whose tissue types closely matched across two human leukocyte antigen haplotypes. Recipients underwent a carefully orchestrated protocol that included low-dose radiation therapy and an infusion of donor stem cells eleven days after transplantation.
The stem cell product, designated MDR-101, was harvested from the same donor who provided the kidney. Recipients received a conditioning regimen with rabbit antithymocyte globulin and total lymphoid irradiation delivered in ten fractions before the stem cell infusion.
Study Results:
- 75% of participants (15 out of 20) remained free of immunosuppressive drugs for over 2 years
- 95% successfully discontinued all medications at the one-year mark
- No deaths, graft losses, or graft-versus-host disease occurred
- Participants showed improved quality of life compared to standard treatment
- Four patients eventually resumed medications due to rejection or disease recurrence
A Patient’s Perspective
Mark Welter, a Minnesota native who participated in the trial four years ago, exemplifies the treatment’s potential. Diagnosed with polycystic kidney disease, he received both a kidney and stem cells from his sister Cindy Kendall. Today, he hasn’t taken immunosuppressive medication for more than three years.
“I feel fantastic. I actually feel like I did before the transplant, which has been the greatest thing,” Welter reflected. “It’s almost like the transplant didn’t happen.”
His sister Cindy observed the transformation: “Being able to see him get off those medications has been amazing. He just gets to live his life to the fullest. He has been able to see both of his daughters get married and meet his grandchildren.”
The Science Behind Success
The treatment works by establishing what researchers call “donor mixed chimerism”—a state where both the recipient’s and donor’s blood cells coexist peacefully. When donor hematopoietic chimerism reached at least 5%, physicians could safely taper and eliminate tacrolimus by the one-year mark.
This approach represents a fundamental shift from suppressing the immune system to retraining it. Rather than permanently weakening the body’s defenses, the stem cell therapy creates a selective tolerance specifically for the transplanted organ.
Future Directions
While promising, the current protocol requires siblings with closely matching tissue types—a limitation that restricts its immediate applicability. Researchers are investigating whether the approach could work with less perfectly matched donors, potentially expanding access to this treatment.
“Even in closely matched siblings, immunosuppression is needed lifelong. We have seen stopping medications even at eight to 10 years post-transplant leads to rejection,” explained Dr. Andrew Bentall, a Mayo Clinic transplant nephrologist. “Our goal is to find ways to reduce or stop immunosuppressive medications after transplant so patients can have longer lasting kidneys with fewer side effects.”
The research forms part of Mayo Clinic’s Transforming Transplant Initiative, which aims to ensure everyone who needs a transplant can receive one while making the procedures more successful. As cellular therapies continue to evolve, this study provides a crucial proof of concept that immune tolerance in organ transplantation is not just possible—it’s achievable.
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