Two-Year Outcomes of the ACCESS Trial for Mismatched Donor Transplants

Heather Stefanski, MD, PhD, representing the National Marrow Donor Program, provides a detailed overview of the ACCESS study (NCT04904588), a clinical trial initiated in 2021 to evaluate the efficacy of post-transplant cyclophosphamide (PTCy) in patients undergoing mismatched unrelated donor (MMUD) stem cell transplantation. The primary objective of the research was to assess overall survival and safety when using donors who are not a perfect genetic match. The data presented at the European Blood and Marrow Transplantation Society Annual Meeting focuses on 2-year outcomes, a critical milestone in transplant medicine because many complications, such as late-onset chronic graft-vs-host disease (GVHD) or disease relapse, can manifest after the initial 12-month recovery period.

The findings from the 12-year analysis remain highly encouraging, as the survival rates and clinical outcomes appeared essentially stable compared to earlier data. Notably, the research team did not observe a significant increase in chronic GVHD, which is a common concern when utilizing mismatched donors. Additionally, there was no substantial uptick in relapse rates during the second year of follow-up. This stability suggests that the PTCy regimen effectively mitigates the risks traditionally associated with mismatched transplants, allowing patients to undergo these procedures with a safety profile comparable to those receiving fully matched grafts.

One of the most transformative aspects of the ACCESS study is its impact on healthcare equity and donor accessibility. Stefanski emphasizes that over 50% of the study participants identified as being from diverse racial or ethnic backgrounds. Historically, patients from minority groups have faced significant barriers to finding a fully matched donor on the registry due to the complexity of HLA diversity.

By proving that mismatched transplantations can be performed safely with PTCy, the study essentially expands the donor pool for populations that previously had a very low probability of finding a match. This shift in clinical practice means that life-saving transplant is now reachable for a broad population of patients who historically would never have proceeded to transplant. Ultimately, these results signify a major step forward in ensuring that ethnic background and other reasons for poor donor matching no longer serve as a barrier to receiving a curative stem cell transplant.