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Australian researchers have demonstrated that the use of a new, less toxic drug combination after stem cell transplants for leukemia significantly improves patient outcomes post-transplant, reducing the risk of the life-threatening complication of graft versus host disease (GVHD).

The trial, led by Monash University and the Australasian Leukemia & Lymphoma Group (ALLG), will transform global blood stem cell transplant outcomes for people with high-risk blood cancers like leukemia.

"This new treatment triples the chances of a patient being alive, healthy and free of GVHD three years after stem cell transplant, " said lead researcher, Professor David Curtis, director of malignant hematology research at the Australian Center for Blood Diseases, Monash University, and clinical hematologist and senior bone marrow transplant physician at The Alfred.

Blood stem cell transplants are often lifesaving for leukemia patients, but they come with a high risk of life-threatening complications, especially in the first 100 days after transplant.

Common side effects include infections, organ damage, and the often-debilitating GVHD, an irreversible, lifelong complication.

"The trial showed the new treatment combination is simple, safe and more effective than current methods in preventing GVHD, which contributes to death or life-long illness in 20% of patients undergoing a blood stem cell transplant, " Professor Curtis said.

"The trial has established a new benchmark for treatment in matched related donor transplantation."

Results were published in the New England Journal of Medicine and presented at the European Hematology Association Meeting (EHA 2025) held in Milan, Italy, June 12–15.

These results are game-changing for stem cell transplant patients, with cyclosporin and cyclophosphamide offering a new standard of care for prevention of GVHD for patients with aggressive blood cancers undergoing transplant from a matched related blood stem cell donor.

The Medical Research Future Fund (MRFF) trial was a five-year, phase 3 randomized controlled trial that was conducted across eight hospital sites in Australia and New Zealand. It tested a new drug combination in 134 patients aged 18–70, most of whom were living with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL).

Researchers compared the standard drug combination used for the last 40 years with a new combination of cyclophosphamide and cyclosporin. The new drug combination tripled the number of patients that were alive, cured of the blood cancer and not suffering from GVHD three years after transplant (49.1% vs. 14.2% for the standard drug combination).

Additionally, the risk of serious side effects was reduced to 19.7% from 32.4%.

The success of the trial has immediate implications for clinical practice in the management of blood stem cell transplants. The simplicity and effectiveness of the new treatment, along with reduced toxicity and improved patient outcomes, will become the new standard of care GVHD prevention in matched sibling transplants.

More information: David J. Curtis et al, Graft-versus-Host Disease Prophylaxis with Cyclophosphamide and Cyclosporin, New England Journal of Medicine (2025). DOI: 10.1056/NEJMoa2503189  Journal information: New England Journal of Medicine