New Aplastic Anemia Preconditioned with Fludarabine, Thiotepa, Cyclophosphamide, and Anti-Thymocyte Globulin

Aplastic anemia (AA) is one of life-threatening hematological disorder that can be cured by hematopoietic stem cell transplantation. When the absence of a matched sibling donor, haploidentical stem cell transplantation (haplo-HSCT) becomes an alternative choice for AA patients. We used a prospective study aimed to confirm the feasibility of Thiotepa-based modified post-transplantation cyclophosphamide (PTCY) strategy in haplo-HSCT for AA patients. We analyzed the outcomes of 15 patients who had undergone haplo-HSCT between October 2021-May 2023 in our clinical center. The modified condition regimen consisted of anti-thymoglobulin/antilymphocyte globulin, fludarabine, thiotepa, busulfan and modified low and high-dose cyclophosphamide, mycophenolate mofetil (MMF) and tacrolimus (FK-506)/cyclosporin (CsA) were administered as graft versus host disease (GVHD) prophylaxis after transplantation. The median follow-up time was 267 (range 97-532) days. All 15 patients were successfully implanted (100%), the median times for neutrophil and platelet engraftment were 14 (range 12-19) days and 12 (range 8-25) days, respectively. But one patient developed secondary graft failure because of infected with COVID-19、cytomegalovirus and H1N1. Fortunately, she subsequently underwent a successful secondary haplo-HSCT. The most common regimen-related toxicity was canker sore, hemorrhagic cystitis occurred in 3 patients during transplantation. The cumulative incidence of grade Ⅰ-Ⅱ aGVHD and cGVHD were 13.3% and 6.7% respectively, whereas the incidence of grade Ⅲ-Ⅳ aGVHD was not found so far. All 15 patients are alive, with a failure-free survival rate of 100% and GVHD relapse-free survival rate of 100%. The efficacy evaluation of haplo-HSCT, 14 patients achieved CR and 1 patient achieved PR. Because of 7 patients received the prevention strategy of Letermovir since August 2022, the reactivation rate of cytomegalovirus (CMV) was only 20% and 60% of Epstein-Barr virus (EBV) reactivation, but the CMV diseases and post-transplantation lymphoproliferative disorder (PTLD) were rare. Our study using Thiotepa-based modified haplo-HSCT demonstrated an encouraging result with prolonged survival and reduced complications for aplastic anemia patients.