Outpatient subcutaneous alemtuzumab is feasible and safe for aplastic anemia and associated with high response rates.

• Subcutaneous alemtuzumab shows high efficacy for AA with a 59.4% response rate at 12 months, better than with rabbit ATG.

• Alemtuzumab was associated with low-grade adverse events and 70% 4-year survival, being a viable alternative where horse ATG is unavailable.

Immunosuppressive therapy (IST) using horse antithymocyte globulin (h-ATG) combined with cyclosporine (CsA) and eltrombopag is the standard care for aplastic anemia (AA) in patients without a suitable matched donor. However, in many countries, h-ATG use has been discontinued, leaving rabbit ATG (r-ATG), which has a lower response rates and poorer survival, as the only alternative. In previous studies, alemtuzumab (ALZ), a humanized monoclonal antibody targeting CD52, combined with CsA resulted in an adequate ORR in AA patients. This study describes a multicenter, international retrospective analysis of ALZ for treating AA. We analyzed a series of patients who received subcutaneous ALZ for AA in four centers in Brazil and the United Kingdom from March 2009 to January 2024. We analyzed 64 ALZ treatments in 61 AA adult patients, 76% with SAA or very severe aplastic anemia (VSAA). Overall response rate (ORR) was 59.4% at 12 months (complete: 21.9%, partial: 37.5%). Cumulative incidence (CI) of response was 54.7% at 6 months, and 59.4% at 12 months. Younger patients (under 65) had higher CI of response (67% vs. 31%, P=0.03), as well as patients treated with a total dose of 103 mg (70% vs. 38%, P=0.02). Overall survival (OS) was 86% at 1 year, 78% at 2 years, and 70% at 4 years, significantly higher in responders (90% vs. 44%, P<0.0001). Adverse events were of low grade, and infectious events were infrequent. Subcutaneous ALZ is a feasible, effective, and safe alternative to r-ATG for AA patients requiring immunosuppressive treatment where h-ATG access is limited.