Cytokine Release Syndrome during Antithymocyte Globulin/Anti-T Lymphocyte Globulin Serotherapy for Graft-versus-Host Disease Prophylaxis before Allogeneic Hematopoietic Stem Cell Transplantation: Incidence and Early Clinical Impact According to American Society of Transplantation and Cellular Therapy Grading Criteria.

Antithymocyte globulin (ATG)/anti-T lymphocyte globulin (ATLG) aids graft-versus-host disease (GVHD) prophylaxis in HLA-matched related and unrelated donor hematopoietic stem cell transplantation (HSCT). Its use is frequently accompanied by systemic infusion reactions attributable to cytokine release syndrome (CRS). However, detailed data on ATG/ATLG-induced CRS and its correlation with clinical outcome parameters are lacking. This study aimed to analyze the incidence, characteristics, risk factors, and early clinical impact of CRS during ATG/ATLG administration before allogeneic HSCT according to the American Society of Transplantation and Cellular Therapy (ASTCT) CRS grading criteria. This retrospective single-center analysis included consecutive recipients of allogeneic HSCT treated with ATG/ATLG as GVHD prophylaxis at the Medical University of Vienna between January 1, 2014, and August 15, 2021. Multivariate regression models were used to explore risk factors for CRS and its association with clinical outcomes (acute GVHD grade II-IV, clinically significant cytomegalovirus infection, nonrelapse mortality, and overall survival) at 6 months after HSCT. A total of 284 patients (median age, 54 years; interquartile range [IQR], 45 to 61 years; 120 females, 164 males) were included in the study. ATLG was used in 222 patients (78%); ATG, in 62 (22%). One hundred sixty-six patients (58%) developed CRS grade ≥1 during ATG/ATLG administration. CRS was mostly mild, with 92% of the cases CRS grade 1-2. Thirteen patients (5%) developed CRS grade 3, and 1 patient had CRS grade 4. No CRS-related death (grade 5) occurred. Patients with CRS showed a pronounced systemic inflammatory response as measured by inflammatory markers C-reactive protein, IL-6, and procalcitonin. In multivariate analysis, lymphoma as the underlying disease, high ATLG dose of 60 mg/kg, and body weight were significantly associated with CRS. Patients with CRS grade ≥1 had a higher 6-month incidence of acute GVHD II-IV compared with patients without CRS (24% versus 14%; P = .04). This effect remained statistically significant only for CRS grade 3-4 (subdistribution hazard ratio, 3.70; 95% confidence interval, 1.58 to 8.68; P < .01) after adjusting for relevant confounders. Other clinical outcome parameters were not affected by the occurrence of CRS. In our cohort, CRS defined by ASTCT grading was a frequent but mostly mild complication following ATG/ATLG administration for GVHD prophylaxis. Our data suggest a possible interaction of (higher-grade) CRS with an increased risk for developing acute GVHD. Further studies to corroborate this finding are warranted, as it could inform the investigation of additional prophylactic interventions, such as IL-6 blockade, in this setting.