Half-Matched Bone Marrow Transplant Expands Treatment Options for Children and Young Adults with Severe Aplastic Anemia

Half-Matched Bone Marrow Transplant Expands Treatment Options for Children and Young Adults with Severe Aplastic Anemia

10/21/2026

@HopkinsKimmel researchers report promising results using half-matched family donors for bone marrow transplants, expanding access to potentially curative treatment for children and young adults with severe aplastic anemia who lack fully matched donors. ›

Researchers at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center and Johns Hopkins Children's Center report that bone marrow transplant using half-matched family donors achieved a 96% survival rate among children, adolescent, and young adult patients with severe aplastic anemia, a rare, life-threatening disorder in which the bone marrow fails to produce enough healthy blood cells. The approach expands access to potentially curative treatment for patients who do not have a fully matched donor.

The findings from the study, supported in part by the National Cancer Institute, were published Aug. 3 in Blood Advances. They suggest that the treatment may be an effective first option for young patients with severe aplastic anemia, including those who have not received previous treatment and those whose disease has returned or failed to completely respond to up-front therapies.

Severe aplastic anemia occurs when the bone marrow fails to produce sufficient red blood cells, that carry oxygen, white blood cells that fight infection, and platelets that help blood clot. Bone marrow transplantation can cure the disease by replacing damaged blood-forming cells with healthy donor cells. The researchers say only about 25% to 30% of patients have a fully matched sibling donor, and finding an unrelated matched donor can be especially difficult for patients from racial and ethnic minority populations who are underrepresented in donor registries.

The Kimmel Comprehensive Cancer Center-developed approach uses haploidentical (half-matched) donors, such as parents, siblings or other relatives, greatly expanding the pool of potential donors. Patients receive reduced-intensity treatment, which uses lower doses of chemotherapy and radiation therapy to prepare their bodies for transplantation. The drug cyclophosphamide is given after transplantation to help prevent graft-versus-host disease (GVHD), a potentially serious complication in which donor immune cells attack the patient's healthy organs and tissues.

"One of the greatest challenges in treating severe aplastic anemia has been finding a suitable donor quickly enough to provide patients with a potentially curative transplant," says senior study author Kenneth Cooke, M.D., the Herman and Walter Samuelson Professor of Oncology and director of the pediatric bone marrow transplant program. "This approach allows us to use readily available family donors while achieving excellent survival and very low rates of serious complications."

The research team, led by Cooke, Heather Symons, M.D., M.H.S., associate professor of oncology and clinical director of pediatric blood and bone marrow transplant, and Amy DeZern, M.D., M.H.S., professor of oncology and vice chair for hematologic malignancies, reviewed outcomes for 31 patients, ages 2 to 20, who underwent bone marrow transplantation at Johns Hopkins between 2014 and 2024. Of these, 23 received the reduced-intensity transplant approach with posttransplant cyclophosphamide, including 21 who received bone marrow from half-matched family donors and two from fully matched siblings. Eight patients received standard-of-care transplants from matched siblings, using a different combination of drugs before and after transplantation.

Among the 23 patients treated with posttransplant cyclophosphamide, 22 survived, for an overall survival rate of 96%. All 14 patients whose disease had returned or failed to respond to previous treatment survived, as did eight of nine patients who had not received previous treatment. All eight patients receiving standard-of-care matched-sibling transplants also survived.

The researchers also found that transplanted donor cells successfully established themselves and continued producing healthy blood cells in nearly all patients receiving the newer approach. At one year, surviving patients had at least 95% donor-derived blood cells, indicating strong, lasting engraftment. All surviving patients remained independent of blood transfusions at their last follow-up.

Serious GVHD was uncommon, and 95% of surviving patients no longer required medications to suppress their immune systems one year after transplantation. Long-term complications were generally infrequent, although some patients experienced kidney problems or changes in reproductive hormone function.

"These findings show that we can overcome longstanding barriers to donor availability while achieving durable engraftment and excellent survival," says pediatric oncologist Margarita Dionysiou, M.D., the first author on the study. "For children and young adults with severe aplastic anemia, this approach offers an opportunity for a cure without the delays associated with searching for a fully matched donor."

The findings build upon decades of research advances at the Kimmel Comprehensive Cancer Center using cyclophosphamide to manage GVHD and to prove that half-matched bone marrow transplant was as safe and effective as fully matched transplants.

The researchers caution that the study was relatively small and that longer follow-up is needed to fully assess potential late effects.

In addition to Cooke, DeZern, Symons and Dionysiou, other researchers contributing to the study were Yiouli Ktena, Challice Bonifant, Allen Chen, Nicolas Llosa, Elias Zambidis, and Richard Jones.

The research was supported by the National Cancer Institute grant R50CA282101,the Seadream Family Foundation, Inc., and the Ashworth/Welch Charitable Fund.

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