Plate Nº 90 · recorded October 10, 2026
Health & Medicine ResearchReported finding
CRISPR-edited stem cells engrafted in all 30 patients in blood cancer trial
A 30-patient trial in Nature Medicine found CRISPR-edited donor stem cells successfully engrafted in every patient, opening a possible path to treating aggressive blood cancers without destroying healthy transplants.
By Elena Vasquez4 min read745 words
In brief
- Trial published September 25, 2026, in Nature Medicine; led by John F. DiPersio at Washington University School of Medicine with 14 other sites in the U.S. and Canada
- All 30 patients with high-risk AML or MDS achieved engraftment by day 28; platelet production returned by day 16 on average
- Nineteen patients received at least one cycle of gemtuzumab ozogamicin; average survival was just over 14 months
- Seven patients died: four from cancer progression and three from transplant-related complications including kidney failure, liver toxicity and sepsis
- A separate case report in JCO Precision Oncology (October 2025) described a patient with TP53-mutant AML who entered complete remission more than one year after receiving CD33-targeted CAR-T cells
A 30-patient clinical trial published September 25, 2026, in Nature Medicine found that CRISPR-edited stem cells successfully took hold in every patient who received them — opening a possible path to treating aggressive blood cancers without destroying the healthy cells a transplant is meant to provide.
In the phase 1/2 study, researchers used CRISPR-Cas9 to remove a protein called CD33 from donor blood stem cells before transplantation. The work took place at Siteman Cancer Center, based at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, and 14 other sites in the United States and Canada.
What problem does CD33 pose?
CD33 sits on the surface of blood-forming cells. That makes it a common target for cancer drugs. But the same protein also appears on healthy myeloid cells — including the very donor stem cells patients receive during transplantation.
Treatments aimed at CD33, such as engineered immune cells called CAR-Ts (chimeric antigen receptor T cells, which are a patient's own immune cells reprogrammed to hunt a specific protein), often cannot tell cancer from a healthy transplant. As a result, they may wipe out the very blood stem cells meant to rebuild the patient.
"The problem," said corresponding author John F. DiPersio, MD, PhD, "is that many proteins found on AML and MDS cancer cells also appear on healthy myeloid cells."
AML is acute myeloid leukemia. MDS, or myelodysplastic syndrome, is a disorder in which the bone marrow fails to make enough healthy blood cells.
How does the editing work?
Before transplant, technicians used CRISPR to delete the CD33 gene from donor stem cells. The resulting product, called tremtelectogene empogeditemcel (trem-cel), was developed by Vor Biopharma, which funded the trial.
Once inside a patient, those edited cells should make blood that lacks CD33. Any cell still carrying the protein after transplant would then most likely be a cancer cell. A CD33-directed therapy could attack the cancer while leaving the healthy donor cells alone.
What did the trial find?
All 30 patients, adults with high-risk AML or MDS, achieved engraftment by day 28 — meaning the transplanted cells had reached the bone marrow and started producing blood. Platelet production returned by day 16 on average. Both timelines match what doctors see with standard transplants.
Average survival reached just over 14 months. Nineteen patients also received at least one cycle of gemtuzumab ozogamicin, an FDA-approved antibody drug that delivers a toxin to CD33-positive cells. Across several dose levels, blood counts held steady.
"We are encouraged by the results of this study showing that a CD33-deleted stem cell transplant looks very similar to the outcomes of standard stem cell transplantation," DiPersio said. "In the future, we are hopeful we will be able to combine this with CD33-targeted immunotherapies, such as CAR-T cells, and improve treatment options for patients with these very aggressive blood cancers."
What were the side effects?
Side effects largely mirrored those of standard stem cell transplantation. Patients experienced anemia, low platelet counts, fever, infections, and graft-versus-host disease, in which donor immune cells attack the recipient's tissues.
Seven patients died during the study. Four deaths followed cancer progression. Three came from transplant-related complications: kidney failure, liver toxicity, and sepsis, a life-threatening response to infection.
Was a single patient already treated with CAR-T cells?
Yes. In a separate case report published in October 2025 in JCO Precision Oncology, DiPersio and colleagues described a patient with high-risk AML carrying a TP53 mutation, a genetic change linked to poor outcomes. After receiving a CD33-deleted transplant, the patient relapsed and was then given CD33-targeted CAR-T cells made from the same donor's T cells.
The patient entered complete remission. More than one year later, the patient remained cancer-free. All of the patient's blood cells lacked CD33, evidence that the edited donor cells had taken long-term hold in the bone marrow.
What are the limits?
The trial was small, single-arm (with no comparison group receiving standard care), and designed mainly to test safety. Survival figures are early. The gene-edited approach also depends on pairing with a CD33-directed therapy, which the team has not yet tested in a larger randomized study.
The underlying concept traces to Miriam Y. Kim, MD, now an assistant professor of medicine at WashU Medicine, who began the work as a postdoctoral researcher at the University of Pennsylvania.
via medicine.washu.edu (Original)
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