A phase 2 clinical trial will test whether removing a specific type of T cell from donor stem cell grafts can reduce graft-versus-host disease (GVHD) after stem cell transplantation. Mast cell leukemiaMast cell leukemia The most severe subtype of SM, caused by the rapid buildup of immature mast cells in the bone marrow and blood. Mast cell leukemia accounts for less than 5% of SM cases and has a poor prognosis., an advanced subtype of systemic mastocytosis (SM), is among the diseases eligible for the study.
In allogeneic hematopoietic stem cell transplantation, healthy stem cells from a donor are given to a patient in the hope that they will help the patient’s bone marrow make healthy blood cells instead of diseased ones. While it can cure disease, it carries risks.
Learn more: “What is a stem cell transplant for systemic mastocytosis?”
GVHD is a serious condition that can happen after stem cell transplantation. GVHD occurs when immune cells from the donor recognize the recipient’s tissues as foreign and mount an immune response against them. This can damage organs such as the skin, liver and intestines, and can sometimes become life-threatening.
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The study will examine if removing a specific type of immune cell — CD45RA-positive naïve T cells — from donor stem cell grafts can reduce the risk of GVHD. Naïve T cells haven’t yet encountered anything that will provoke an immune response and are ready to be activated. The researchers noted that removing these T cells may help prevent the immune response seen in GVHD.
Previous studies on removing naïve T cells have shown promising but mixed results. An early trial found a low rate of chronic GVHD, although acute GVHD was not reduced. A later analysis of three phase 2 trials also found low rates of chronic and severe acute GVHD.
The trial is located at the Fred Hutchinson Cancer Center/University of Washington in Seattle, and will enroll 52 adults older than 60 with several blood cancers, including mast cell leukemia. It is not yet recruiting, with enrollment expected to begin in January 2027. Patients with mast cell leukemia must be in morphological remission, with less than 5% blast cells in the bone marrow.
Before transplantation, participants will receive cyclophosphamide and fludarabine chemotherapy and total-body irradiation to destroy the diseased cells. They will then receive donor stem cells that have been processed to remove CD45RA-positive naïve T cells.
The main goal of the study is to assess GVHD relapse-free survival one year after transplantation. This measure looks at how long participants remain alive without disease relapse, severe acute GVHD or chronic GVHD. Researchers will also evaluate overall survival, relapse, graft failure and treatment-related mortality.
Read more about MCL: “Subtypes explained: What is mast cell leukemia?”
