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Rebecca Olin, MD, MS


Anti-CD117 Monoclonal Antibody Plus Nonmyeloablative Conditioning in Older Patients With AML

By: Cordi Craig, MS
Posted: Friday, July 16, 2021

Although nonmyeloablative conditioning is generally more tolerable among older or vulnerable populations with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS), it has been associated with higher relapse rates. Lori S. Muffly, MD, MS, of Stanford University, California and colleagues reported early-phase results with JSP191, a first-in-class monoclonal antibody that inhibits stem cell factor binding to CD117, as a component of a nonmyeloablative conditioning regimen during the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 7035). JSP191, in combination with nonmyeloablative conditioning consisting of low-dose radiation and fludarabine, appeared to be effective among high-risk, older adults with measurable residual disease (MRD)-positive MDS or AML.

In this small phase I trial, the researchers evaluated the safety and tolerability of allogeneic hematopoietic cell transplantation conditioning using JSP191, low-dose radiation, and fludarabine in six older patients with high-risk MDS or AML. MRD was detected using cytogenetics, the difference from normal flow cytometry, or next-generation sequencing. Some of the secondary endpoints included engraftment, donor chimerism, and MRD clearances.

The study team recorded no infusion toxicities or serious JSP191-related adverse events, and all patients are still on trial. All subjects were engrafted with neutrophil recovery 19 to 26 days following transplantation, and they achieved at least 94% donor myeloid chimerism in the blood 28 days after transplantation. The three patients who were evaluable 90 days after transplantation showed complete donor total chimerism, myeloid chimerism, and MRD elimination.

Disclosure: For full disclosures of the study authors, visit

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