Outcomes of Tocilizumab for Cytokine Release Syndrome after Post-Transplant Cyclophosphamide.

Cytokine release syndrome (CRS) is common after allogeneic hematopoietic cell transplantation (alloHCT) using post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis. Although tocilizumab effectively manages CRS, its impact on transplant outcomes in the PTCy setting remains unclear. We performed a single-center retrospective study of adult patients undergoing PTCy-based alloHCT from 2014 to 2024. Patients who received tocilizumab for CRS were matched 1:1 with patients with CRS who did not receive tocilizumab using propensity score matching. Of 346 patients, 190 (55%) developed CRS. Greater HLA mismatch and peripheral blood graft source (versus bone marrow) were the only independent risk factors for CRS. Among those with CRS, 46 (24%) received tocilizumab; after propensity score matching, 40 patients were included per group. Tocilizumab was associated with shorter CRS duration (median 2 versus 3 d), but also with delayed neutrophil engraftment (median 19 versus 17 d) and higher 100-d bacterial infection rates (65% versus 28%). Tocilizumab use was linked to lower grade II to IV acute GVHD (HR 0.52, 95% CI 0.30 to 0.92; P = .02) and all-grade chronic GVHD (HR 0.35, 95% CI 0.15 to 0.81; P = .02), with nonsignificant trends toward reduced grade III to IV acute GVHD (HR 0.40, 95% CI 0.13 to 1.24; P = .11) and moderate-to-severe chronic GVHD (HR 0.41, 95% CI 0.14 to 1.14; P = .09). No significant differences were seen in relapse, non-relapse mortality, GVHD-free/relapse-free survival, or overall survival. In PTCy-based alloHCT, tocilizumab for CRS was associated with reduced grade II to IV acute GVHD and all-grade chronic GVHD, at the expense of delayed neutrophil engraftment and increased early bacterial infections.