NMDP’s ACCESS Trial Results Published in Journal of Clinical Oncology, Demonstrating Strong Outcomes with Mismatched Unrelated Donors in Adult Stem Cell Transplantation

June 17, 2025 at 10:14 AM EDT

Findings expand access for patients with blood cancer lacking a matched donor

Results from the ACCESS (Allogeneic Cell Transplantation Clinical Evaluation of Stem Cell Sources) study, a multicenter Phase II clinical trial sponsored by NMDP^SM, a global nonprofit leader in cell therapy, and conducted by its collaborative research program, CIBMTR® (Center for International Blood and Marrow Transplant Research®), were published in the peer-reviewed Journal of Clinical Oncology. The results demonstrate that post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis enables safe and effective hematopoietic cell transplantation (HCT) from mismatched unrelated donors (MMUD), significantly expanding access to curative therapy for patients with blood cancers.

Evaluating outcomes in two conditioning intensity groups—myeloablative (MAC) and reduced-intensity/nonmyeloablative (RIC/NMA)—the study found there was no significant difference in overall survival (OS) between patients with 7/8 HLA-matched donors and those with <7/8 matches, supporting broader donor eligibility. The one-year OS was 83.8% for MAC and 78.6% for RIC/NMA recipients. These outcomes were comparable to, or better than, historical 8/8 matched donor benchmarks (75%).

“These study results are a major step forward in making allogeneic peripheral blood stem cell transplantation more accessible for all patients who need a lifesaving procedure,” said Monzr M. Al Malki, M.D., Professor, Department of Hematology & Hematopoietic Cell Transplantation, City of Hope and ACCESS study co-chair. “By demonstrating that mismatched unrelated donors can be used safely and effectively, we are opening the door to curative therapy for patients who historically had limited or no donor options. The findings published also lay the groundwork for future Phase III trials comparing MMUD transplantation to other alternative donor strategies.”

The trial enrolled 145 adult patients with high-risk hematologic malignancies across 21 U.S. transplant centers, with 59% self-identifying as members of underrepresented racial or ethnic groups. Participants received peripheral blood stem cell (PBSC) grafts from MMUDs and were treated with a standardized PTCy-based GVHD prophylaxis regimen.

Low rates of severe GVHD were also observed, with grade III-IV acute GVHD at six months occurring in only 8% (MAC) and 10% (RIC/NMA) and severe chronic GVHD at 12 months in only 3% (MAC) and 4% (RIC/NMA) of patients. The pool of study participants included a high representation of socially vulnerable populations, with many patients reporting financial hardship and reduced physical function at baseline.

NMDP-led Donor for All research

Historically, finding an available matched, unrelated donor on international registries has been limited for patients with ethnically diverse ancestry— from as low as 29% for Black or African American patients and 48% for Latino and Hispanic patients versus 79% for non-Hispanic White patients. NMDP’s network of transplant centers, many of which participate in CIBMTR trials, are bringing new research to light that is challenging previously established HCT science.

To improve outcomes, NMDP is sponsoring a series of clinical trials studying the use of PTCy GVHD prophylaxis in MMUD HCT (patients matched at 4/8 to 7/8 alleles).

ACCESS builds upon findings from the first Donor for All trial, the groundbreaking NMDP-sponsored 15-MMUD study, which showed that PTCy was effective in decreasing risk for GVHD in adults with hematologic malignancies receiving bone marrow transplants from MMUDs. ACCESS is closed to further enrollment, with pediatric results forthcoming next year.
The OPTIMIZE trial is now enrolling and evaluating whether a reduced dose of PTCy will safely and effectively prevent GVHD while reducing infection risk in patients with hematologic malignancies receiving PBSC HCT from MMUDs.
The ACCELERATE trial will open to accrual this summer to further reduce the risk of GVHD and other post-transplant complications in patients.

“Our Donor for All research is transforming cell therapy as well as redefining donor eligibility and transplant accessibility – helping close the donor gap and extend curative therapies to every patient who needs a life-saving transplant,” Steven Devine, MD, chief medical officer, NMDP, and senior scientific director, CIBMTR, and a senior author of the study, added.

About CIBMTR®

CIBMTR® (Center for International Blood and Marrow Transplant Research®) is a nonprofit research collaboration between NMDP^SM, in Minneapolis, and the Medical College of Wisconsin®, in Milwaukee. CIBMTR collaborates with the global scientific community to increase survival and enrich quality of life for patients. CIBMTR facilitates critical observational and interventional research through scientific and statistical expertise, a large network of centers, and a unique database of long-term clinical data for more than 675,000 people who have received hematopoietic cell transplantation and other cellular therapies. Learn more at cibmtr.org.

About NMDP^SM

At NMDP^SM, we believe each of us holds the key to curing blood cancers and disorders. As a global nonprofit leader in cell therapy, NMDP creates essential connections between researchers and supporters to inspire action and accelerate innovation to find life-saving cures. With the help of blood stem cell donors from the world’s most diverse registry and our extensive network of transplant partners, physicians and caregivers, we’re expanding access to treatment so that every patient can receive their life-saving cell therapy. NMDP. Find cures. Save lives. Learn more at nmdp.org.