Background: IL-6 mediates graft-vs.-host disease (GVHD) in experimental models of allogeneic stem cell transplantation. The addition of a humanized anti-IL-6R mAb (Tocilizumab; TCZ) to standard GVHD prophylaxis has shown in promise in reducing the incidence of acute GVHD in two prospective phase I/II clinical studies. Aims: To determine the efficacy of TCZ in preventing grade II-IV acute GVHD in patients with acute leukaemia or myelodysplasia undertaking 8/8 matched related sibling (MSD) or matched unrelated donor (MUD) allogeneic HPCT after myeloablative (MAC) or reduced intensity conditioning (RIC) across five Australian transplant centers. Methods: 145 patients (50 MSD and 95 MUD) were randomly assigned to either placebo or TCZ (8mg/kg; max dose 800mg) on day-1 of conditioning. Patients and physicians were both blinded to treatment. RIC patients all received Flu/Mel (n=81, 56%) while MAC patients received Cy/TBI (n=46, 32%) or Bu/Cy (n=18, 12%). All patients received T-replete PBPC grafts, and standard GVHD prophylaxis cyclosporine and day 1 (15mg/m2), 3, 6 and 11 (10mg/m2) methotrexate. The primary endpoint was incidence of grade II-IV acute GVHD. A planned substudy analyzed the MUD cohort. Secondary endpoints included day 180 grade II-IV acute GVHD free-survival (GVHD-FS), transplant-related mortality (TRM), progression-free survival (PFS), overall survival (OS), time to engraftment and rates of infection. The study was powered to observe a 50% reduction in the incidence of grade II-IV acute GVHD at day +100 for the entire and MUD cohorts, assuming a 50-55% baseline in the control group. Competing risk (death) regression adjusted hazard ratio (HR) was estimated to evaluate the GVHD-related outcomes in TCZ vs. placebo groups. Results: With a median follow up of 746 days, the overall incidence of grade II-IV GVHD at day 100 for the entire cohort was 36% vs. 27% for placebo vs. TCZ respectively (HR: 0.69; 95% CI 0.38-1.26; p=0.23), and 45% vs. 32% (HR: 0.61; 95% CI 0.31-1.22; p=0.16) for the MUD subgroup. The incidence of grade II-IV GVHD at day 180 for the entire cohort was 40% vs. 29% for placebo vs. TCZ respectively (HR: 0.68; 95% CI 0.38-1.22; p=0.19), and 48% vs. 32% (HR: 0.59; 95% CI 0.30-1.16; p=0.13) for the MUD subgroup. The incidence of severe grade III/IV GVHD at day 100 for the entire cohort was similar, 13% vs. 14% for placebo vs. TCZ respectively (HR: 1.04; 95% CI 0.42-2.61; p=0.93), and 10% vs. 14% for the MUD subgroup (HR: 1.42; 95% CI 0.41-4.95; p=0.59). A trend to improved GVHD-FS was noted in the TCZ-treated MUD subgroup, 52% vs. 68% for placebo vs. TCZ treated (HR: 1.70; 95% CI 0.86-3.37; p=0.13). For the entire cohort, TRM occurred in 8% of placebo-treated vs. 11% of TCZ-treated patients respectively (HR: 1.37; 95% CI 0.48-3.96; p=0.56); Progressions were similar at 25% vs. 33% (HR:1.44; CI 0.78-2.63, p=0.24) and OS was 79% vs. 71% (HR: 0.69; CI 0.35-1.34, p=0.27). No significant differences were seen in these outcomes in the MUD cohort. Day to neutrophil engraftment was marginally delayed in TCZ-treated patients, with median time to neutrophil ≥0.5 of 15 days (range 11-24 days) vs. 18 days (range 9-35 days) for placebo vs. TCZ-treated patients respectively (95% CI 1.3-4.7; p=0.001). Time to platelet engraftment was also marginally delayed in TCZ-treated patients, with median time to plts≥20 of 16 days (range 9-36 days) vs. 19 days (range 11-389 days) (95% CI 0.4-5.6; p=0.022). The median time to neutrophil and platelet engraftment in TCZ-treated patients were each 2 days slower in the MUD cohort (p=0.016 and p=0.22 for neutrophils and plts respectively). Two TCZ-treated patients died beyond day 30 (at day 31 and 32) with incomplete neutrophil recovery. The incidence of 1 or more grade 3 or higher liver toxicity (LT) was similar between groups, occurring in 14% of placebo-treated patients vs. 15% of TCZ-treated patients respectively (OR: 1.14; 95% CI 0.45-2.88; p=0.79). Grade 2 or higher infection adverse events occurred in 64% of placebo-treated patients vs. 71% of TCZ-treated patients respectively (OR: 1.34; 95% CI 0.67-2.71; p=0.41). Conclusion: In a phase III randomized, double-blind trial, TCZ administered at D-1 showed non-significant trends to reduced incidence of grade II-IV GVHD and improved acute GVHD-free survival in recipients of HLA-matched MUD donors, but no improvements in long term-survival. Study power was compromised by lower rates of acute GVHD in the control group than anticipated. Disclosures Ritchie: Novartis: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy; BMS: Research Funding; Takeda: Research Funding; Beigene: Research Funding; Imago: Research Funding; Sanofi: Honoraria. Gottlieb:Novartis: Consultancy; AbbVie: Consultancy; University of Sydney: Employment; Merck: Consultancy; Gilead: Consultancy; Haemalogix P/L: Membership on an entity's Board of Directors or advisory committees, Research Funding. Paul:Novo Nordisk: Consultancy, Research Funding; Sanofi: Consultancy, Speakers Bureau; Roche: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Hill:Roche: Other: Investigator driven trial funding; Pharamcyclics: Consultancy, Research Funding; CSL: Consultancy, Research Funding; Implicit Bioscience: Consultancy, Research Funding. OffLabel Disclosure: Use of Tocilizumab for the prevention of acute GVHD

Voriconazole‐associated periostitis (VAP) is an underrecognized and unpredictable side effect of long‐term voriconazole therapy. We report two cases of VAP occurring in the post‐transplant setting: a 68‐year‐old lung transplant recipient who required ongoing voriconazole therapy, in whom urinary alkalinization was used to promote fluoride excretion and minimize voriconazole‐related skeletal toxicity, and a 68‐year‐old stem‐cell transplant recipient with a high voriconazole dose requirement, identified on pharmacogenomic testing to be a CYP2C19 ultrarapid metabolizer, the dominant enzyme in voriconazole metabolism. This is the first reported case of pharmacogenomic profiling in VAP and may explain the variability in individual susceptibility to this uncommon adverse effect. Our findings provide new insights into both the management and underlying pathophysiology of VAP. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Background: Interleukin-6 (IL-6) promotes the differentiation of pathogenic T cells and represents a dominant pathway of cytokine-dysregulation and graft-versus-host disease (GVHD). Cytomegalovirus (CMV) reactivation is a common and life-threatening infectious complication following allogenic bone marrow transplantation (BMT). The role of T cell immunity is long-established, and our group recently demonstrated that CMV strain-specific immunoglobulins (Ig) are critical in preventing CMV reactivation in preclinical models (Martins JP et al, Science 2019). Methods and Results: In a phase I/II clinical trial (Kennedy GA et al, Lancet Onc. 2014), we observed unexpectedly low rates of CMV reactivation following IL-6 receptor (IL-6R) blockade with tocilizumab (TCZ) compared to historical control (8/35 vs 20/43, P < 0.05). We used our preclinical models of murine CMV (MCMV) reactivation to pursue the mechanisms. We transplanted bone marrow (BM) and T cells from naïve B6 donors into CMV-latently infected B6D2F1 recipients and monitored MCMV reactivation. Ablation of IL-6R in donor T cells (using B6 CD4 cre x IL-6R fl/fl transgenic mice; IL-6R -/-) significantly reduced MCMV reactivation 5 weeks after BMT, as measured by plasma viremia and infectious viral loads in the liver (Fig 1A). Next, we examined the contribution of donor T and B cells to the suppression of MCMV reactivation by IL-6R inhibition. At 2 - 3 weeks after BMT and prior to MCMV reactivation, cytokine (IFNɣ/TNF) secretion from CD4 + T cells (in response to MCMV infected DC) was not detectable; MCMV m38 tetramer + CD8 T cells were present at very low frequencies (< 0.1% of CD8 T cells) which were not altered by IL-6R ablation. The frequency of CXCR-5 +PD-1 + T FH cells was comparable or lower in IL-6R -/- vs wild-type (WT) T cells after BMT. Transplant of BM from B6.μMT mice (unable to generate mature B cells and plasma cells) did not increase MCMV viremia (Fig 1B), excluding a role for donor B cells. Thus, early MCMV reactivation in the presence of IL-6 is independent of MCMV-specific T cells and donor B cells. To study the effects of IL-6 on recipient-derived humoral immunity we quantified MCMV-specific IgG in plasma after BMT and found that levels were significantly higher in recipients of IL-6R -/- T cells (Fig 1C). Furthermore, MCMV-IgG levels in plasma correlated with MCMV viremia (r = - 0.72, P < 0.0001) and viral loads in liver (r = - 0.68, P < 0.0001). MCMV-IgG2a, which can only be generated by B6D2F1 recipients, was significantly higher in recipients of IL-6R -/- T cells, confirming that differences in humoral responses were of recipient-origin. To define relevant mechanisms, we examined the kinetics of IgG after BMT by monitoring the loss of murine IgG (transferred on day 0) in plasma (Fig 1D). Recipients of IL-6R -/- T cells showed significantly slower loss of IgG than recipients of WT T cells, with or without GVHD prophylaxis with cyclosporine (CSA). Thus, ablation of IL-6 signaling in donor T cells is associated with reduced loss of recipient IgG and protection from MCMV reactivation, an outcome which seems independent of the effects of IL-6 on GVHD. We correlated our findings with data from a recent randomized, placebo-controlled, double-blind phase III clinical trial of TCZ administration on Day -1 of BMT (Kennedy GA et al, Blood 2021). TCZ reduced CMV reactivation in at risk seropositive BMT recipients of volunteer unrelated donor grafts regardless of acute GVHD (all at risk recipients, TCZ vs. control: 12/26 vs 21/28, P = 0.03; at risk without grade 2-4 GVHD, TCZ vs control: 6/18 vs 9/13, P = 0.03). TCZ did not alter the frequency of B cells or the frequency and function of HCMV-specific CD8 + T cells, quantified by HCMV-pMHC tetramer-staining and HCMV peptide-specific cytokine (IFNγ/TNF) secretion. In contrast, levels of HCMV-specific IgG at day +30 in HCMV-seropositive recipients were significantly higher in the TCZ versus control group (Fig 1E). Consistent with our preclinical studies, the level of HCMV-IgG significantly and inversely correlated with early HCMV reactivation (within 35 days) after transplant. Conclusion: These data confirm the importance of recipient-derived humoral immunity in controlling early CMV reactivation in clinical BMT recipients. Critically, we demonstrate the ability of IL-6R blockade to maintain protective humoral responses until effective donor-derived adaptive immunity can be generated. Figure 1 Figure 1. Disclosures Boeckh: Merck: Consultancy, Research Funding; SymBio Pharmaceuticals: Consultancy; Helocyte: Consultancy; Evrys Bio: Consultancy; Moderna: Consultancy; Gilead: Consultancy, Research Funding; AlloVir: Consultancy; GSK: Consultancy. Hill: Generon corporation: Consultancy; NapaJun Pharma: Consultancy; Compass Therapeutics: Research Funding; Syndax Pharmaceuticals: Research Funding; Applied Molecular Transport: Research Funding; iTeos Therapeutics: Consultancy, Research Funding; Roche: Research Funding; Neoleukin Therapeutics: Consultancy.