Impaired survival of patients with non donor-specific anti-HLA antibodies before HLA-mismatched allogeneic stem cell transplantation

Background: While the detrimental role of donor-specific anti-HLA antibodies (DSAs) is well-described in the setting of hematopoietic stem cell transplantation (HSCT), few studies focus on non donor-specific ones and with controversial results. Methods: We here report our monocenter experience on 64 adult patients receiving allogeneic HSCT from a HLA-mismatched donor between 2014 and 2022 who were tested for the presence of anti-HLA antibodies before transplant, focusing on fifteen patients with non donor-specific anti-HLA antibodies. Results: The survival of patients with non donor-specific anti-HLA antibodies was inferior with respect to patients without anti-HLA antibodies and similar to patients with DSAs. Median survival of patients with non donor-specific anti-HLA antibodies was 21 months (95 % CI: 9-42) vs. 61 months (95 % CI: 17-77) among the anti-HLA antibody-negative patients, with a significantly higher mortality incidence rate ratio (3.3 times-fold greater, p = 0.01). No pattern of death causes was found CONCLUSIONS: In this monocenter series of HLA-mismatched HSCTs, impaired survival was observed in adult patients having non donor-specific anti-HLA antibodies before transplant, similar to those with DSAs. Our findings support those antibodies as a negative predictive factor even if they are not directed against the donor, thus warranting further investigation on larger cohorts.