CRISPR Edits Donor Stem Cells to Spare Healthy Blood — SkimNews
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- John F. DiPersio at WashU Medicine led a 30-patient phase 1/2 trial using CRISPR to remove CD33 from donor stem cells before transplantation in high-risk AML and MDS patients, with results published in Nature Medicine on September 25, 2026.
- The gene-edited product tremtelectogene empogeditemcel (trem-cel), developed and funded by Vor Biopharma, achieved engraftment in all 30 patients by day 28, with platelet production returning by day 16 on average — recovery times the authors say mirror standard stem cell transplantation.
- Nineteen patients who received the CD33-targeted antibody-drug conjugate gemtuzumab ozogamicin as post-transplant maintenance maintained their blood cell counts, suggesting the edited transplant shielded them from the severe drops in white blood cells, red blood cells, and platelets the drug typically causes.
- A separate case report published in JCO Precision Oncology in October 2025 described a patient with TP53-mutant high-risk AML who relapsed after a CD33-deleted transplant, then entered complete remission after receiving donor-derived CD33 CAR-T cells and remained cancer-free more than a year later.
- Seven patients died during the trial — four from cancer progression and three from transplant-related complications including kidney failure, liver toxicity, and sepsis — though side effects overall were comparable to standard stem cell transplantation.
- Miriam Y. Kim, MD, who first described the gene-editing approach as a postdoctoral researcher at the University of Pennsylvania, now treats patients at Siteman Cancer Center, where the trial was conducted alongside 14 other sites across the U.S. and Canada.
Why it matters: The trial delivers the first engraftment evidence in 30 patients that CRISPR-deleted CD33 donor cells can survive a CD33-targeted maintenance drug without the usual severe cytopenias, giving clinicians a concrete platform to pair stem cell transplantation with CAR-T therapy for AML and MDS — diseases where CAR-T has previously faltered because target proteins also sit on healthy myeloid cells.
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