Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation.

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells

Treosulfan Exposure Predicts Thalassemia-free Survival In Patients With Beta Thalassemia Major (TM) Undergoing Allogeneic Hematopoietic Cell Transplantation

A toxicity-reduced conditioning regimen with Treosulfan, Fludarabine, and Thiotepa in patients with high-risk β- thalassemia major has significantly improved HCT outcomes. However, complications resulting from regimen-related toxicities (RRTs), mixed chimerism, and graft rejection remain a challenge. We evaluated the dose-exposure-response relationship of Treosulfan and its active metabolite S, S-EBDM, in a uniform cohort of patients with β-thalassemia major to identify whether therapeutic drug monitoring (TDM) and dose adjustment of Treosulfan is feasible. Plasma Treosulfan/S, S-EBDM levels were measured in seventy-seven patients using a validated LC-MS/MS method, and the PK parameters were estimated using nlmixr2. The influence of Treosulfan & S, S-EBDM exposure, and GSTA1/NQO1 polymorphisms on graft rejection, RRTs, chimerism status, and 1-year Overall Survival (OS), and Thalassemia Free Survival (TFS) were assessed. We observed that Treosulfan exposure was lower in patients with graft rejection than those without (1655 vs. 2037 mg*h/L, p=0.07). Pharmacodynamic modeling analysis to identify therapeutic cut-off revealed that Treosulfan exposure ≥1660 mg*hr/L was significantly associated with better 1-year TFS (97% vs. 81%, p=0.02) and a trend to better 1-year OS (90% vs. 69%, p=0.07). Further, multivariate analysis adjusting for known PreHCT risk factors also revealed Treosulfan exposure <1660mg*h/L (HR=3.23; 95% CI=1.12-9.34; p=0.03) and GSTA1*B variant genotype (HR=3.75; 95% CI=1.04-13.47; p=0.04) to be independent predictors for inferior 1-year TFS. We conclude that lower Treosulfan exposure increases the risk of graft rejection and early transplant-related mortality affecting TFS. As no RRTs were observed with increasing Treosulfan exposure, TDM-based dose adjustment could be feasible and beneficial

Prognostic plasma biomarkers of early complications and graft‐versus‐host disease in patients undergoing allogeneic hematopoietic stem cell transplantation

Abstract Early complications post hematopoietic stem cell transplantation (HSCT) such as sinusoidal obstruction syndrome (SOS) and graft versus host disease (GVHD) can be life threatening. Although several biomarkers have been identified to correlate with these complications and their response to treatment, these are yet to be used in clinical practice. Here, we evaluated circulating endothelial cells (CECs) (n = 26) and plasma biomarkers (ST2, REG3α, VCAM1, ICAM1, TIM3) (N = 210) at early time points, to determine their association with early complications post‐HSCT. Elevated CEC counts at the end of conditioning was associated with GVHD, indicating endothelial damage during HSCT. Plasma levels of REG3α, VCAM1, ICAM1, and TIM3 on day 14 (D14) and D14 ICAM1 and D28 ST2 were significantly higher in patients with SOS and aGVHD, respectively. Upon sub‐group analysis, D28 ST2, D14/D28 REG3α, and D14 ICAM1 levels were significantly higher in patients with gastrointestinal GVHD, while D28 ST2 was higher in those with skin/liver GVHD. High ST2 levels on D28 was significantly associated with non‐relapse mortality (NRM) and overall survival. Our results suggest that elevated ST2 levels on D28 could predict the likelihood of developing aGVHD and could influence NRM and OS

Identification of novel HPFH-like mutations by CRISPR baseediting that elevate the expression of fetal hemoglobin

Naturally occurring point mutations in the HBG promoter switch hemoglobin synthesis from defective adult beta-globin to fetal gamma-globin in sickle cell patients with hereditary persistence of fetal hemoglobin (HPFH) and ameliorate the clinical severity. Inspired by this natural phenomenon, we tiled the highly homologous HBG proximal promoters using adenine and cytosine base editors that avoid the generation of large deletions and identified novel regulatory regions including a cluster at the -123 region. Base editing at -123 and -124 bp of HBG promoter induced fetal hemoglobin (HbF) to a higher level than disruption of well-known BCL11A binding site in erythroblasts derived from human CD34+ hematopoietic stem and progenitor cells (HSPC). We further demonstrated in vitro that the introduction of -123T > C and -124T > C HPFH-like mutations drives gamma-globin expression by creating a de novo binding site for KLF1. Overall, our findings shed light on so far unknown regulatory elements within the HBG promoter and identified additional targets for therapeutic upregulation of fetal hemoglobin.ISSN:2050-084