Alemtuzumab (anti-CD52 antibody) is frequently prescribed to children with nonmalignant diseases undergoing allogeneic hematopoietic stem cell transplantation (HSCT) to prevent graft failure (GF)... Show moreAlemtuzumab (anti-CD52 antibody) is frequently prescribed to children with nonmalignant diseases undergoing allogeneic hematopoietic stem cell transplantation (HSCT) to prevent graft failure (GF) and acute graft-versus-host disease (aGVHD). The aim of this multicenter study was the characterization of alemtuzumab population pharmacokinetics to perform a novel modelbased exposure-response analysis in 53 children with nonmalignant immunological or hematological disease and a median age of 4.4 years (interquartile range [IQR], 0.8-8.7). The median cumulative alemtuzumab dose was 0.6 mg/kg (IQR, 0.6-1) administered over 2 to 7 days. A 2-compartment population pharmacokinetics model with parallel linear and nonlinear elimination including allometrically scaled bodyweight (median, 17.50 kg; IQR, 8.76-33.00) and lymphocyte count at baseline (mean, 2.24 x 10(9)/L; standard deviation +/- 1.87) as significant pharmacokinetic predictors was developed using nonlinear mixed effects modeling. Based on the model-estimated median concentration at day of HSCT (0.77 mu g/mL; IQR, 0.33-1.82), patients were grouped into a low- (<= 0.77 mu g/mL) or high- (>0.77 mu g/mL) exposure groups. High alemtuzumab exposure at day of HSCT correlated with delayed CD4(+) and CD8(+) T-cell reconstitution (P value <.0001) and increased risk of GF (P value =.043). In contrast, alemtuzumab exposure did not significantly influence the incidence of aGVHD grade >= 2, mortality, chimerism at 1 year, viral reactivations, and autoimmunity at a median follow-up of 3.3 years (IQR, 2.5-8.0). In conclusion, this novel population pharmacokinetics model is suitable for individualized intravenous precision dosing to predict alemtuzumab exposure in pediatric allogeneic HSCT for nonmalignant diseases, aiming at the achievement of early T-cell reconstitution and prevention of GF in future prospective studies. Show less
Background:Alemtuzumab is a humanized monoclonal antibody that targets the CD52 glycoprotein expressed on most lymphocytes, subsequently inducing complement-mediated and antibody-mediated... Show moreBackground:Alemtuzumab is a humanized monoclonal antibody that targets the CD52 glycoprotein expressed on most lymphocytes, subsequently inducing complement-mediated and antibody-mediated cytotoxicity. Owing to its ability to induce profound immune depletion, alemtuzumab is frequently used in patients before allogeneic hematopoietic stem cell transplantation to prevent graft rejection and acute graft-versus-host disease. In this clinical context, a stable immunoassay with high sensitivity and specificity to determine alemtuzumab levels is essential for performing pharmacokinetic and pharmacodynamic analyses; however, the available methods have several limitations. Here, we report the successful development and validation of an efficient and highly sensitive enzyme-linked immunosorbent assay technique based on commercially available reagents to quantify alemtuzumab in human serum or plasma.Methods:This enzyme-linked immunosorbent assay technique was developed and validated in accordance with the European Medicines Agency guidelines on bioanalytical method validation.Results:The assay sensitivity (lower limit of quantification) is 0.5 ng center dot mL(-1), and the dynamic range is 0.78-25 ng center dot mL(-1). To accommodate quantification of peak concentration and concentrations below the lympholytic level (<0.1 mcg center dot mL(-1)), patients' serum samples were prediluted 20-400 times according to the expected alemtuzumab concentration. The overall within-run accuracy was between 96% and 105%, whereas overall within-run precision (coefficient of variation) was between 3% and 9%. The between-run assessment provided an overall accuracy between 86% and 95% and an overall coefficient of variation between 5% and 14%.Conclusions:The developed assay provides accurate insight into alemtuzumab exposure and its effects on the clinical response to treatment, which is key to optimizing treatment strategies. Show less
Kielsen, K.; Oostenbrink, L.V.E.; Asmuth, E.G.J. von; Jansen-Hoogendijk, A.M.; Ostaijen-ten Dam, M.M. van; Ifversen, M.; ... ; Muller, K. 2021
Differentially and functionally distinct T cell subsets are involved in the development of complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about... Show moreDifferentially and functionally distinct T cell subsets are involved in the development of complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about factors regulating their recovery after HSCT. In this study, we investigated associations between immune-regulating cytokines, T cell differentiation, and clinical outcomes. We included 80 children undergoing allogeneic HSCT for acute leukemia using bone marrow or peripheral blood stem cells grafted from a matched sibling or unrelated donor. Cytokines (IL-7, IL-15, IL-18, SCF, IL-6, IL-2, and TNF-alpha) and active anti-thymocyte globulin (ATG) levels were longitudinally measured along with extended T cell phenotyping. The cytokine profiles showed a temporary rise in IL-7 and IL-15 during lymphopenia, which was strongly dependent on exposure to active ATG. High levels of IL-7 and IL-15 from graft infusion to day +30 were predictive of slower T cell recovery during the first 2 mo post-HSCT; however, because of a major expansion of memory T cell stages, only naive T cells remained decreased after 3 mo (p < 0.05). No differential effect was seen on polarization of CD4(+) T cells into Th1, Th2, or Th17 cells or regulatory T cells. Low levels of IL-7 and IL-15 at day +14 were associated with acute graft-versus-host disease grades II-IV in ATG-treated patients (p = 0.0004 and p = 0.0002, respectively). Children with IL-7 levels comparable to healthy controls at day +14 post-HSCT were less likely to develop EBV reactivation posttransplant. These findings suggest that quantification of IL-7 and IL-15 may be useful as biomarkers in assessing the overall T cell depletion and suggest a potential for predicting complications after HSCT. Show less
Oostenbrink, L.V.E.; Pool, E.S.; Jol-van der Zijde, C.M.; Jansen-Hoogendijk, A.M.; Vervat, C.; Halteren, A.G.S. van; ... ; Mohseny, A.B. 2021
The use of HLA-mismatched (un)related donors is historically associated with a higher incidence of transplant-related complications and mortality. However, the use of such donors may overcome the... Show moreThe use of HLA-mismatched (un)related donors is historically associated with a higher incidence of transplant-related complications and mortality. However, the use of such donors may overcome the limited availability of HLA-matched donors for patients with beta-thalassemia major (TM) and sickle cell disease (SCD). We investigated hematopoietic stem cell transplantation (HSCT) outcomes of pediatric TM and SCD patients treated with a mismatched donor using a treosulfan-based conditioning in combination with ATG and post-transplant cyclophosphamide (PT-CY) and compared these results to the clinical outcome of patients treated by matched donor HSCT without PT-CY. Thirty-eight children (n = 24 HLA-identical or 10/10-matched donors; n = 14 HLA-mismatched donors), who received a non-depleted bone marrow graft were included. Event-free survival (EFS) and GvHD were not higher in the mismatched PT-Cy group as compared to the matched group. Moreover, despite delayed neutrophil engraftment (day +22 vs. +26, p = 0.002) and immune recovery in the mismatched PT-Cy group, this did not result in more infectious complications. Therefore, we conclude that in the absence of an HLA-identical or a matched unrelated donor, HSCT with a mismatched unrelated or haploidentical donor in combination with ATG plus PT-CY can be considered a safe and effective treatment option for pediatric hemoglobinopathy patients. Show less
Oostenbrink, L.V.E.; Jol-van der Zijde, C.M.; Kielsen, K.; Jansen-Hoogendijk, A.M.; Ifversen, M.; Muller, K.G.; ... ; Tol, M.J.D. van 2019
Mannose-binding lectin (MBL) is an activator of the lectin pathway of the C' system and hence an important component of the innate immune system. Although reports are conflicting, MBL deficiency... Show moreMannose-binding lectin (MBL) is an activator of the lectin pathway of the C' system and hence an important component of the innate immune system. Although reports are conflicting, MBL deficiency has been reported to influence the infection susceptibility in hematology/oncology patients or recipients of allogeneic hematopoietic SCT (HSCT). MBL levels and the occurrence of infections were retrospectively analyzed in 98 pediatric HSCT patients. MBL deficiency in recipients was not corrected by HSCT using a donor with normal MBL production. In addition, low serum MBL concentrations were not associated with increased susceptibility to any type of infections post-HSCT in this cohort of pediatric HSCT recipients. Bone Marrow Transplantation (2010) 45, 289-293; doi:10.1038/bmt.2009.159; published online 13 July 2009 Show less
