New protocol opens marrow and stem cell transplantation to many more patients with blood cancer

Image credit – University of Miami Miller School of Medicine

CANCER DIGEST – June 29, 2025 – A clinical study has shown that a new protocol for stem cell or bone marrow transplantation with a commonly used immunosuppressant for patients with partially matched donors achieves outcomes comparable to patients with fully matched donors. 

The finding greatly expands the pool of potential donors for hard-to-match patients, and opens transplantation to many more patients with blood diseases, according to lead investigator Antonio Jimenez, MD of the University of Miami Miller School of Medicine.

“Outcomes were comparable to fully matched donors, which means your pool of potential donors is now huge,” senior study author Antonio Jimenez Jimenez, M.D. said in a press release. “Not only can you now offer every patient a transplant, but you can also optimize other factors when looking for a donor.” 

The trial published June 16, 2025 in the Journal of Clinical Oncology involved 145 adult patients who received stem cell transplants following a procedure to either ablate or eradicate the patient’s marrow, called myeloablative conditioning or a less intense procedure that only partially ablates the patient’s diseased bone marrow. Stem cells were then infused into the patient from partially matched people who voluntarily donated marrow or stem cells for the National Marrow Donor Program.

Matching people’s marrow is based on a set of proteins or antigens that make up the immune systems’ ability to differentiate cells that belong to the person and those that don’t or are abnormal. A complete match is when all eight of those proteins of the patient’s immune system match those of the donor. In this study the majority of patients had a match of six or seven of those eight antigens. 

When unmatched donors are used, a complication called graft versus host disease (GVHD) that can be severe occurs. The new immune system formed from the transplanted stem cells recognize the patient’s tissues as foreign and attacks them, causing diarrhea, nausea, vomiting, jaundice and rashes. To help prevent that, the patients in this study were given cyclophosphamide following the stem cell infusions.

After one year 78.6% of the patients with the reduced ablation procedure survived, and 83.8% of those who had the fully myeloablative procedure survived. In addition, six months after infusion 8% of patients in the less intense ablation group suffered moderate to severe GVHD compared to 10% of those in the intense ablation group. After one year the rates of moderate to severe GVHD was 8.6% for the reduced ablation group and 10.3% of the intense ablation group.

The researchers are continuing to follow and collect data on these patients to determine longer term outcomes. Meanwhile the investigators are conducting a similar trial using a lower dose of cyclophosphamide and another trial testing cyclophosphamide and a different mixture of drugs to try to reduce the effects of GVHD even further.

The researchers note that while about 70 percent of patients can find fully-matched donors, a significant number of people can’t, and certain populations the chances of a fully-matched donor are even lower. Consequently the findings of this study opens stem cell transplantation to many more people who could benefit from the procedure.

Source: University of Miami Miller School of Medicine press release and the Journal of Clinical Oncology