A novel conditioning regimen for hematopoietic stem cell transplantation (SCT) from haploidentical donors in patients with severe thalassemia appears to be safe and efficacious, yielding results similar to those for patients with fully matched donors, according to study results published in Biology of Blood and Marrow Transplantation.

Investigators initiated the program with high-risk thalassemia patients who had matched donors and found it to be safe and efficacious. They then hypothesized that they could expand the donor pool for SCT in patients with severe thalassemia to include haploidentical related donors using the same strategy.

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The program consisted of a pharmacological pretransplant immune suppression phase (2 courses of dexamethasone and fludarabine) followed by pretransplant conditioning (fludarabine and intravenous busulfan), post-transplant graft-versus-host disease (GVHD) prophylaxis (cyclophosphamide, tacrolimus, and mycophenolate mofetil), and supportive care (penicillin V and ciprofloxacin as antibacterial prophylaxis and itraconazole as antifungal prophylaxis).

In total, 83 patients with transfusion-dependent thalassemia (median age, 12 years; range, 1-28) received transplants. Median follow-up was 15 months (range, 7-53). The 3-year overall and event-free survival rates were both 96% (95% CI, 85.7%-98.4%).

Among the first 31 patients, 2 primary graft failures occurred; the investigators noted that both occurred in patients who had high titers of antidonor-specific human leukocyte antigen antibodies (anti-DSA; > 1:3000). This prompted the team to adjust the first phase of the program to include bortezomib and rituximab for patients with high anti-DSA titers. No additional primary graft failures occurred, and no secondary graft failures occurred.

Adverse events included severe GVHD (6 patients), grade 1 to 2 mucositis (25 patients), grade 3 mucositis (10 patients), cytomegalovirus reactivation (15 patients), cytomegalovirus (2 patients), BK virus cystitis (23 patients), adenovirus cystitis (3 patients), herpes zoster reactivation (1 patient), gram-negative septicemia (5 patients), and gram-negative septicemia (2 patients). There were 4 patient deaths that resulted from pneumonia (2 patients), GVHD complications (1 patient), and bacterial sepsis (1 patient).

“The present study demonstrated that outcomes after haplo[identical] SCT in patients with severe thalassemia are acceptable, and now very similar to what’s expected with allo[geneic] SCT using matched donors,” the investigators concluded.

Reference

1.     Anurathapan U, Hongeng S, Pakakasama S, et al. Hematopoietic stem cell transplantation for severe thalassemia patients from haploidentical donors using novel conditioning regimen [published online January 10, 2020]. Biol Blood Marrow Transplant.  doi:10.1016/j.bbmt.2020.01.002