(180) Outcomes in Patients with Aplastic Anemia Treated with Horse Anti-thymocyte Globulin and/or Stem Cell Transplantation at an Academic Medical Center (Top Ten Poster)

Poster Abstract:

Background: Severe aplastic anemia (AA) is a bone marrow failure disorder. Treatment includes immunosuppressive therapy with horse anti-thymocyte globulin (HATG), eltrombopag, cyclosporine or allogeneic hematopoietic stem cell transplantation (SCT). HATG can be complicated by infusion reactions and infections (approximately 45%-67% of patients), SCT is complicated by graft rejection and graft-versus-host disease (GVHD). SCT survival has improved (70-90%) in the current era of HLA-matched donors with optimized post-transplant immunosuppression. HATG regimen demonstrates 90% survival but 30-40% relapse at 5 years.

Objectives: This study aimed to assess response outcomes and adverse events observed in patients with aplastic anemia treated with HATG and/or SCT.

Methods: This study spanning 01/01/2014 to 09/04/2023, involved 35 adult patients with AA treated with HATG and/or SCT. Around 60% were female, primarily Hispanic, and mostly presented with severe AA. In the HATG cohort, 37% received triple therapy and 58% received corticosteroids (> 20mg/day, > 1 month). SCT patients had HLA matched unrelated grafts (54%) or related grafts (46%), with 27% receiving prior HATG.

Results: Median survivals for HATG and SCT groups were 27 months (IQR: 16-49) 88% and 26 months (IQR: 11-34) 64%, respectively. Median progression-free survival was 22 months (IQR: 9-33) for HATG and 32 months (IQR: 28-42) for SCT. All SCT patients achieved complete response; HATG saw 38% (9/24) complete response and partial response each, with 20% refractory, and 4% relapsed.
Infections occurred in 8% (HATG) and 45% (SCT), with 18% of SCT cases having multiple infections. Antiviral and antipseudomonal prophylaxis were universal; antifungals were used in 83% (HATG) and 100% (SCT). Pneumocystis jiroveci prophylaxis rates were similar.
90-day mortality was 4% in HATG patients and 18% in SCT patients. Horse ATG infusion reactions were 29%; one SCT patient had chronic GVHD.

Conclusion: Both HATG (88%) and SCT cohorts (64%) showed slightly lower survival than historical data. Horse ATG's 38% complete response aligns with controls. SCT's 100% response attributed to careful recipient/donor selection and conditioning regimen. Infections were low in HATG due to prophylaxis. Almost half of SCT patients had infections despite prophylaxis, due to neutropenia/T-lymphocyte depletion/GVHD prophylaxis. Low mortality in HATG reflects proper management, while optimized SCT regimens may contribute to low GVHD rates. Both treatments are effective for AA, but risks and benefits need individual evaluation. HATG showed survival benefits but 38% relapse; SCT's 100% response rates make it a strong option despite infection risks.

References (must also be included in final poster): 1. Lertpongpiroon R, Rattarittamrong E, Rattanathammethee T, et al. Infections in patients with aplastic Anemia in Chiang Mai University. BMC Hematol. 2018;18:35. Published 2018 Dec 4. doi:10.1186/s12878-018-0129-9
2. Young NS. Aplastic Anemia. N Engl J Med. 2018;379(17):1643-1656. doi:10.1056/NEJMra1413485
3. Chen M, Liu Q, Gao Y, et al. Cyclosporine plus eltrombopag in the treatment of aplastic anemia with or without antithymocyte immunoglobulin: A multicenter real-world retrospective study [published online ahead of print, 2023 Jun 4]. Eur J Haematol. 2023;10.1111/ejh.14021. doi:10.1111/ejh.14021
4. Georges GE, Doney K, Storb R. Severe aplastic anemia: allogeneic bone marrow transplantation as first-line treatment. Blood Adv. 2018;2(15):2020-2028. doi:10.1182/bloodadvances.2018021162
5. Patel BA, Groarke EM, Lotter J, et al. Long-term outcomes in patients with severe aplastic anemia treated with immunosuppression and eltrombopag: a phase 2 study. Blood. 2022;139(1):34-43. doi:10.1182/blood.2021012130
6. Peffault de Latour R, Kulasekararaj A, Iacobelli S, et al. Eltrombopag Added to Immunosuppression in Severe Aplastic Anemia. N Engl J Med. 2022;386(1):11-23. doi:10.1056/NEJMoa2109965