CRISPR-edited donor stem cells may make blood cancer therapy safer

September 25, 2026 at 06:28 PM2 min

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A clinical trial led by Washington University School of Medicine in St. Louis found that genetically modifying donor stem cells to remove the CD33 protein could make follow-up cancer treatments safer and potentially more effective. The study, conducted at Siteman Cancer Center and 14 other sites in the U.S. and Canada, was published in Nature Medicine. The approach aims to allow CAR-T therapy to attack cancer cells while sparing healthy transplanted cells.

Key Facts

The clinical trial involved patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) who received donor stem cells genetically modified to remove the CD33 protein.
The study was conducted at Siteman Cancer Center, based at Barnes-Jewish Hospital and WashU Medicine, and 14 other sites in the U.S. and Canada.
Results were published in Nature Medicine.
Corresponding author John F. DiPersio, MD, PhD, is the Virginia E. & Sam J. Golman Professor of Medicine at WashU Medicine and directs WashU Medicine's Center for Gene and Cellular Immunotherapy.
The underlying idea was first described by Miriam Y. Kim, MD, now an assistant professor of medicine at WashU Medicine, who began the research as a postdoctoral researcher at the University of Pennsylvania.

CAR-T Therapy Challenge

CAR-T therapy has proved highly effective against some aggressive blood cancers, but it has not worked as well against diseases such as acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Many proteins found on AML and MDS cancer cells also appear on healthy myeloid cells, including donor stem cells used in transplantation. If CAR-T cells are programmed to attack one of those shared proteins, they may destroy healthy blood stem cells along with the cancer. That damage can trigger a dangerous inflammatory response and may weaken the cancer treatment because large numbers of CAR-T cells end up attacking healthy targets instead of concentrating on malignant cells.

CD33 Removal Strategy

In the clinical trial, patients with AML and MDS received donor stem cells that had been genetically modified to remove a protein called CD33. The goal was to create healthy blood cells that would no longer be vulnerable to treatments designed to attack CD33. John F. DiPersio, MD, PhD, the corresponding author, said the gene editing approach could help overcome a major obstacle that has limited CAR-T cell therapy in certain blood cancers. DiPersio stated, "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."