Research shows haploidentical BMT is a suitable option for patients without a matched sibling donor
For people with severe sickle cell disease (SCD), complications like stroke, lung damage and heart problems can cause serious—even life-threatening—health issues. Allogeneic blood or marrow transplant (BMT) offers a potential cure.
Now new research from the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) shows that using reduced intensity conditioning to get the body ready for BMT, a human leukocyte antigen (HLA) haploidentical (half-matched) related donor, and an immune-suppressing drug called post-transplant cyclophosphamide (PTCy) could open the door to transplant for more patients with SCD.
Why the research is important
Allogeneic BMT uses cells from a donor. Historically, a full donor match offered the best chance for a good outcome. Unfortunately, less than 15% of patients with SCD have a matched sibling donor. Most don’t have a full unrelated donor match on the NMDP Registry SM either. In the United States SCD is most common in people who are Black or African American. But currently, Black and African American patients have a 29% chance of finding a matching, available donor on the registry.
In addition, the full intensity (myeloablative) conditioning regimen that’s used in children with SCD to get the body ready for BMT can be too toxic to use for adults. These issues can keep people with SCD from accessing BMT.
While myeloablative gene therapy and gene editing clinical trials are available for patients with SCD, those with severe SCD typically cannot participate in these trials, which eliminates another potential treatment option.
By expanding the pool of available donors beyond a full HLA match, more patients with SCD could access a potentially curative transplant.
What the researchers investigated
The BMT CTN 1507 clinical trial expanded on smaller studies that used reduced intensity haploidentical transplant with PTCy. Those studies had encouraging results, but concerns remained about graft failure and graft-versus-host disease (GHVD) when using a haploidentical donor.
Graft failure means the transplanted donor cells don’t make new white blood cells, red blood cells and platelets. GVHD is a serious complication after BMT where the donor’s cells attack the patient’s healthy cells.
This clinical trial studied patients aged 15 to 45 years old with severe SCD who had an HLA-haploidentical first-degree relative (parent or sibling) willing and able to donate bone marrow.
The patients received reduced-intensity conditioning and PTCy. The investigators wanted to understand the impact on event-free survival (EFS) at 2 years after transplant. EFS means the patient did not have graft failure, acute or chronic GVHD, or readmission to the hospital.
What the study found
This multi-center Phase II clinical trial showed positive results. The 2-year EFS (88%) and overall survival post-transplant (95%) were similar to results reported for patients with SCD who receive a matched sibling donor transplant and full intensity conditioning.
What this means for patients
These results support reduced intensity haploidentical transplant with PTCy as an appropriate and tolerable curative therapy for adults with severe SCD. This is a positive step forward and reduces a major barrier to transplant—access to a suitable donor.