Hematopoietic stem cell transplantation for Wiskott-Aldrich syndrome: an EBMT Inborn Errors Working Party analysis.

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for patients affected by Wiskott-Aldrich syndrome (WAS). Reported HSCT outcomes have improved over time with respect to overall survival, but some studies have identified older age and HSCT from alternative donors as risk factors predicting poorer outcome. We analyzed 197 patients undergoing transplant at European Society for Blood and Marrow Transplantation centers between 2006 and 2017 who received conditioning as recommended by the Inborn Errors Working Party (IEWP): either busulfan (n = 103) or treosulfan (n = 94) combined with fludarabine ± thiotepa. After a median follow-up post-HSCT of 44.9 months, 176 patients were alive, resulting in a 3-year overall survival of 88.7% and chronic graft-versus-host disease (GVHD)-free survival (events include death, graft failure, and severe chronic GVHD) of 81.7%. Overall survival and chronic GVHD-free survival were not significantly affected by conditioning regimen (busulfan- vs treosulfan-based), donor type (matched sibling donor/matched family donor vs matched unrelated donor/mismatched unrelated donor vs mismatched family donor), or period of HSCT (2006-2013 vs 2014-2017). Patients aged <5 years at HSCT had a significantly better overall survival. The overall cumulative incidences of grade III to IV acute GVHD and extensive/moderate/severe chronic GVHD were 6.6% and 2.1%, respectively. Patients receiving treosulfan-based conditioning had a higher incidence of graft failure and mixed donor chimerism and more frequently underwent secondary procedures (second HSCT, unconditioned stem cell boost, donor lymphocyte infusion, or splenectomy). In summary, HSCT for WAS with conditioning regimens currently recommended by IEWP results in excellent survival and low rates of GVHD, regardless of donor or stem cell source, but age ≥5 years remains a risk factor for overall survival.

Flow cytometry for comprehensive assessment of platelet functional activity in response to ADP stimulation.

OBJECTIVES: Flow cytometry with adenosine diphosphate (ADP) allows to characterize molecular changes of platelet function caused by this physiologically important activation, but the methodology has not been thoroughly investigated, standardized and characterized yet. We analyzed the influence of several major variables and chose optimal conditions for platelet function assessment. METHODS: For activation, 2.5 µM CaCl2 , 5 µM ADP and antibodies were added to diluted blood and incubated for 15 min. We analyzed kinetics of antibody binding and effects of their addition sequence, agonist concentration, blood dilution, exogenous calcium addition and platelet fixation. RESULTS: We tested our protocol on 11 healthy children, 22 healthy adult volunteers, 9 patients after a month on dual antiplatelet therapy after percutaneous coronary intervention (PCI), 7 adult patients and 14 children with immune thrombocytopenia (ITP). We found that our protocol is highly sensitive to ADP stimulation with low percentage of aggregates formation. The assay is also sensitive to platelet function inhibition in post-PCI patients. Finally, platelet preactivation with ITP plasma was stronger and caused increase in activation response to ADP stimulation compared to preactivation with low dose of ADP. CONCLUSIONS: Our assay is sensitive to antiplatelet therapy and platelet preactivation in ITP patients under physiological conditions with minimal percentage of aggregates formation.

Successful Treatment of Acquired Thrombotic Thrombocytopenic Purpura With Caplacizumab Combined With Plasma Exchanges and Immune Suppression in 3 Children.

Acquired thrombotic thrombocytopenic (aTTP) purpura is a life-threatening condition that can lead to devastating thromboembolic events. Recently, caplacizumab has been shown to rapidly restore platelet numbers and reduce the risk of severe end-organ damage when added to plasma exchanges (PEXs) and immunosuppression (IST). Here, we report the outcomes in 3 children with aTTP who were treated with caplacizumab in combination with PEXs and IST. In all 3 patients, platelet count increased to >15,000/mm 3 in 24 h and normalized on day 4, whereas normalization of ADAMTS13 activity >50% and elimination of the inhibitor was achieved after 18 to 89 days. Epistaxis was observed in 2 patients and was the only side effect related to caplacizumab. Caplacizumab is a promising agent for first-line treatment of children with aTTP.

Accelerated death of megakaryocytes from Wiskott-Aldrich syndrome patients.

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder caused by WAS gene mutations resulting in haematopoietic/immune cell defects. Recent studies report accelerated death of WAS platelets and lymphocytes. Data on megakaryocyte (MK) maturation, viability and their possible role in thrombocytopenia development in WAS are limited. In this study we evaluate the MK viability and morphology in untreated, romiplostim-treated WAS patients compared with normal controls. The study included 32 WAS patients and 17 healthy donors. MKs were captured from bone marrow aspirates by surface-immobilized anti-GPIIb-IIIa antibody. Viability (by phosphatidylserine [PS] externalization), distribution by maturation stages and size of MK were determined by light microscopy. MK distribution by maturation stages in patients differed from controls. 40 ± 22% of WAS MKs versus 23 ± 11% of normal MKs were at maturation stage 3 (p = 0.02), whereas 24 ± 20% in WAS and 39 ± 14% in controls had megakaryoblast morphology (p = 0.05). Romiplostim treatment changed the MK maturation stages distribution close to normal. PS-positive (PS+) MK in WAS was significantly higher (21 ± 21%) than in healthy controls (2 ± 4%, p < 0.01). WAS patients with more damaging truncating mutations and higher disease score had higher PS+ MK fraction (Spearman r = 0.6, p < 0.003). We conclude that WAS MKs have increased cell death tendency and changes in maturation pattern. Both could contribute to thrombocytopenia in WAS patients.

Recognizing Minor Leukemic Populations with Monocytic Features in Mixed-Phenotype Acute Leukemia by Flow Cell Sorting Followed by Cytogenetic and Molecular Studies: Report of Five Exemplary Cases.

Mixed-phenotype acute leukemia (MPAL), a rare and heterogeneous category of acute leukemia, is characterized by cross-lineage antigen expression. Leukemic blasts in MPAL can be represented either by one population with multiple markers of different lineages or by several single-lineage populations. In some cases, a major blast population may coexist with a smaller population that has minor immunophenotypic abnormalities and may be missed even by an experienced pathologist. To avoid misdiagnosis, we suggest sorting doubtful populations and leukemic blasts and searching for similar genetic aberrations. Using this approach, we examined questionable monocytic populations in five patients with dominant leukemic populations of B-lymphoblastic origin. Cell populations were isolated either for fluorescence in situ hybridization or for clonality assessment by multiplex PCR or next-generation sequencing. In all cases, monocytic cells shared the same gene rearrangements with dominant leukemic populations, unequivocally confirming the same leukemic origin. This approach is able to identify implicit cases of MPAL and therefore leads to the necessary clinical management for patients.

Unusual Presentation of SET::NUP214-Associated Concomitant Hematological Neoplasm in a Child-Diagnostic and Treatment Struggle.

Simultaneous multilineage hematologic malignancies are uncommon and associated with poorer prognosis than single-lineage leukemia or lymphoma. Here, we describe a concomitant malignant neoplasm in a 4-year-old boy. The child presented with massive lymphoproliferative syndrome, nasal breathing difficulties, and snoring. Morphological, immunocytochemical, and flow cytometry diagnostics showed coexistence of acute myeloid leukemia (AML) and peripheral T-cell lymphoma (PTCL). Molecular examination revealed a rare t(9;9)(q34;q34)/SET::NUP214 translocation as well as common TCR clonal rearrangements in both the bone marrow and lymph nodes. The disease showed primary refractoriness to both lymphoid and myeloid high-dose chemotherapy as well as combined targeted therapy (trametinib + ruxolitinib). Hence, HSCT was performed, and the patient has since been in complete remission for over a year. This observation highlights the importance of molecular techniques for determining the united nature of complex SET::NUP214-positive malignant neoplasms arising from precursor cells with high lineage plasticity.

Multicenter Experience of Hematopoietic Stem Cell Transplantation in WHIM Syndrome.

PURPOSE: WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome is a rare disease, caused by CXCR4 gene mutations, which incorporates features of combined immunodeficiency, congenital neutropenia, and a predisposition to human papillomavirus infection. Established conventional treatment for WHIM syndrome does not fully prevent infectious complications in these patients. Only single case reports of hematopoietic stem cell transplantation (HSCT) efficacy in WHIM have been published. METHODS: To summarize current information on HSCT efficacy in disease treatment, seven pediatric patients with WHIM syndrome who underwent allogeneic HSCT were identified in five centers worldwide. RESULTS: All patients presented early after birth with neutropenia. Two of seven patients exhibited severe disease complications: poorly controlled autoimmunity (arthritis and anemia) in one and progressive myelofibrosis with recurrent infections in the other. The remaining patients received HSCT to correct milder disease symptoms (recurrent respiratory infections, progressing thrombocytopenia) and/or to preclude severe disease course in older age. All seven patients engrafted but one developed graft rejection and died of infectious complications after third HSCT. Three other patients experienced severe viral infections after HSCT (including post-transplant lymphoproliferative disease in one) which completely resolved with therapy. At last follow-up (median 6.7 years), all six surviving patients were alive with full donor chimerism. One patient 1.4 years after HSCT had moderate thrombocytopenia and delayed immune recovery; the others had adequate immune recovery and were free of prior disease symptoms. CONCLUSION: HSCT in WHIM syndrome corrects neutropenia and immunodeficiency, and leads to resolution of autoimmunity and recurrent infections, including warts.

Efficacy and safety of a reduced dose of plerixafor in combination with granulocyte colony-stimulating factor in healthy haploidentical stem cell donors.

BACKGROUND AND OBJECTIVES: Implementation of the technique of immunomagnetic selection requires the procurement of a large number of CD34+ cells from haploidentical donors within a single apheresis procedure. The release of stem cells with granulocyte colony-stimulating factor (G-CSF) alone is unsatisfactory in a number of donors, and plerixafor, a CXCR4 chemokine receptor antagonist, could be used as an additional mobilization agent. The aim of our study was to examine whether a lower dose of plerixafor (0.12 mg/kg) can provide sufficient increase in CD34+ cells in the peripheral blood of allogeneic healthy donors in comparison with a historical control group. In addition, we assessed the risk of inability to provide the recipient with a transplant containing the optimal dose of 8-10 × 106 CD34+ cells/kg body weight of the recipient. MATERIALS AND METHODS: In a prospective, single-arm study, we examined the results of 105 mobilizations in healthy adult haploidentical donors with G-CSF and plerixafor at a dose of 0.12 mg/kg. The historical control group consisted of 106 mobilizations with G-CSF and plerixafor at 0.24 mg/kg. RESULTS: The median increase in the number of CD34+ cells from day 4 to day 5 of mobilization was 69 cells/µl (range, 28-240) versus 77 cells/µl (24-217) in the groups of 0.12 and 0.24 mg/kg of plerixafor, respectively (p-value 0.255). The apheresis products contained a median of 14.4 × 106 /kg recipient body weight CD34+ cells versus 12.9 × 106 /kg in the groups that received 0.12 and 0.24 mg/kg of plerixafor, respectively (p-value 0.118). The obtained differences were not significant, which means the application of a decreased dose of plerixafor did not affect the results of mobilization. CONCLUSION: The obtained differences in collection were not significant, and thus the application of a decreased dose of plerixafor did not affect the results of mobilization.

Pediatric patients with acute lymphoblastic leukemia treated with blinatumomab in a real-world setting: Results from the NEUF study.

BACKGROUND: Prior to regulatory approval of blinatumomab in pediatric patients with relapsed/refractory Philadelphia chromosome-negative B-cell precursor acute lymphoblastic leukemia (R/R Ph- BCP-ALL), blinatumomab was made available via an expanded access program (EAP). PROCEDURE: This retrospective observational study included patients receiving blinatumomab in the EAP between January 1, 2014 and June 30, 2017 who were followed until death, entry into a clinical trial, end of follow-up, or end of the study period (December 31, 2017), whichever occurred first. RESULTS: Among 113 children enrolled, 72 were diagnosed with R/R Ph- BCP-ALL and 41 were minimal residual disease positive (MRD+, either Ph- or Ph+). In the R/R group, 38 (53%) patients achieved hematological response within two cycles. Of these, 19 (50%) proceeded to hematopoietic stem cell transplantation (HSCT) without bridging myelosuppressive therapy. Of 36 patients in the R/R group evaluable for MRD, 30 (83%) had an MRD response. In the R/R group, median relapse-free survival was 5.4 months and median overall survival (OS) was 8.2 months. Of 36 patients in the MRD+ group who were evaluable for MRD after two cycles, 27 (75%) had an MRD response. Overall, 24 (59%) of the MRD+ patients proceeded to HSCT without other bridging therapy. Median disease-free survival was 13.6 months; median OS was not reached. CONCLUSIONS: In this real-world pediatric cohort, blinatumomab was effective within two cycles. Over half of patients with R/R Ph- BCP-ALL achieved hematological response and most achieved MRD response in the MRD+ group, confirming the efficacy of blinatumomab in pediatric trials.

Healthy pediatric platelets are moderately hyporeactive in comparison with adults' platelets.

Studies on platelet function in children older than neonatal period are few and their results are controversial. The pediatric platelets were alternatively reported to be more active or less active than adults' ones. We compared platelet function in the several age groups of children to adults and evaluated the age when platelet function reaches the adults' status. The study included 76 healthy children and 49 healthy adult volunteers. Types of platelet activation used included: collagen-related peptide (CRP) and PAR-1 activating peptide SFLLRN; SFLLRN, PAR-4 activating peptide AYPGKF and adenosine diphosphate (ADP); ADP. The parameters determined included forward (FSC) and side scatter (SSC), CD42b, CD61, CD62P, PAC-1, annexin V binding and mepacrine release levels. Resting pediatric platelets were similar to adults' platelets except for 1.2-fold decreased FSC and dense granules volume in youngest children, and 2.5-fold increased annexin V level in children aged 1-10 years. After CRP+SFLLRN stimulation, pediatric platelets had a 1.2-fold lower alpha- and 1.1-fold lower dense granule release than adults. For SFLLRN+AYPGKF+ADP stimulation, this was observed only for youngest children. The response to ADP stimulation was identical for pediatric platelets and adults. Pediatric platelets have lower granular release than adults' platelets, which persists until the age of 18.

Lineage Conversion in Pediatric B-Cell Precursor Acute Leukemia under Blinatumomab Therapy.

We report incidence and deep molecular characteristics of lineage switch in 182 pediatric patients affected by B-cell precursor acute lymphoblastic leukemia (BCP-ALL), who were treated with blinatumomab. We documented six cases of lineage switch that occurred after or during blinatumomab exposure. Therefore, lineage conversion was found in 17.4% of all resistance cases (4/27) and 3.2% of relapses (2/63). Half of patients switched completely from BCP-ALL to CD19-negative acute myeloid leukemia, others retained CD19-positive B-blasts and acquired an additional CD19-negative blast population: myeloid or unclassifiable. Five patients had KMT2A gene rearrangements; one had TCF3::ZNF384 translocation. The presented cases showed consistency of gene rearrangements and fusion transcripts across initially diagnosed leukemia and lineage switch. In two of six patients, the clonal architecture assessed by IG/TR gene rearrangements was stable, while in others, loss of clones or gain of new clones was noted. KMT2A-r patients demonstrated very few additional mutations, while in the TCF3::ZNF384 case, lineage switch was accompanied by a large set of additional mutations. The immunophenotype of an existing leukemia sometimes changes via different mechanisms and with different additional molecular changes. Careful investigation of all BM compartments together with all molecular -minimal residual disease studies can lead to reliable identification of lineage switch.

Quantification of NG2-positivity for the precise prediction of KMT2A gene rearrangements in childhood acute leukemia.

It has long been known that there is a link between neuron glial antigen 2 (NG2) surface expression and KMT2A gene rearrangements in acute leukemia (AL). However, the exact levels of NG2 positivity that predict the presence of KMT2A rearrangement are not known. The current study focuses on a cohort of 505 pediatric AL patients who showed any level of positive NG2 expression (greater than 1% of cells) for whom comprehensive genetic data were available. NG2 expression was measured as either the percentage of positive cells or the number of molecules on the cell surface. KMT2A gene rearrangements were identified by FISH. The fusion partner was detected with RT-PCR, LDI-PCR or anchored multiplex PCR followed by high-throughput sequencing. KMT2A-positive samples comprised a substantial proportion of the NG2-positive cohort (180 of 505, 36%), with a total of 19 different types of translocation. Despite its occurrence in other AL genetic subgroups, NG2 expression was significantly increased in AL patients with KMT2A rearrangements in terms of both the cell percentage and number of molecules per cell. The threshold levels (TL) for NG2-positivity were established by ROC analysis of the whole cohort and separately for children less than 1 years old and older with lymphoblastic (ALL) and myeloid (AML) leukemia. The lowest TL was defined in infants with ALL (7%), while in older children, the threshold was higher (12%). In AML patients, the situation was reversed, with 28% NG2-positivity in infants and 14% in patients >1 year old. The defined TLs resulted in improved diagnostic performance compared to the conventional thresholds of 10% and 20% for all patient groups.

Efficacy of romiplostim in treatment of thrombocytopenia in children with Wiskott-Aldrich syndrome.

Wiskott-Aldrich syndrome (WAS) is a life-threatening primary immunodeficiency associated with bleeding of variable severity due to thrombocytopenia. Correction of the thrombocytopenia is of paramount importance for most WAS patients. We report a retrospective analysis of the safety and efficacy of romiplostim treatment in reducing thrombocytopenia and bleeding tendency in 67 children (median age 1·3 years) with genetically confirmed WAS, followed in eight months (range, 1-12 months). Complete or partial primary responses regarding platelet counts were observed in 22 (33%) and 18 (27%) subjects, respectively. Yet, even in the non-responder group, the risk of haemorrhagic events decreased significantly, to 21%, after the first month of treatment. The responses tended to be durable and stable over time, with no significant fluctuations in platelets counts. The results of this retrospective study of a large cohort of WAS patients demonstrates that romiplostim can be used to increase platelet counts and reduce the risks of life-threatening bleeding in WAS patients awaiting haematopoietic stem cell transplantation or forgoing the procedure for various reasons.

Blinatumomab following haematopoietic stem cell transplantation - a novel approach for the treatment of acute lymphoblastic leukaemia in infants.

Blinatumomab with subsequent haematopoietic stem cell transplantation was applied in 13 infants with acute lymphoblastic leukaemia (ALL). Eight patients were treated in first remission due to slow clearance of minimal residual disease (MRD); one for MRD-reappearance after long MRD negativity, one for primary refractory disease and three during relapse treatment. In slow MRD responders, complete MRD response was achieved prior to transplantation, with an 18-month event-free survival of 75%. In contrast, only one of five patients with relapsed/refractory ALL is still in complete remission. These data provide a basis for future studies of immunotherapy in very high-risk infant ALL.

Mismatched related vs matched unrelated donors in TCRαß/CD19-depleted HSCT for primary immunodeficiencies.

TCRαß+/CD19+ graft depletion effectively prevents graft-versus-host disease (GVHD). In the current study, we compared the outcomes of hematopoietic stem cell transplantation (HSCT) with TCRαß+/CD19+ depletion from matched unrelated donors (MUDs) and mismatched related donors (MMRDs) in patients with primary immunodeficiency (PID). A total of 98 pediatric patients with various PIDs underwent HSCT with TCRαß+/CD19+ graft depletion from MUDs (n = 75) and MMRDs (n = 23). All patients received a fludarabine-/treosulfan-based conditioning regimen, with 73 also receiving a second alkylating agent. For GVHD prophylaxis, all but 2 received serotherapy (antithymocyte globulin) before HSCT and a short course of posttransplant immunosuppression. Neutrophil and platelet engraftment in both the MUD and MMRD groups occurred on days 14 and 13, respectively. The incidence of secondary graft failure was 0.16 and 0.17 (P = .85), respectively. The cumulative incidence of acute GVHD grade 2 to 4 was 0.17 in the MUD group and 0.22 in the MMRD group (P = .7). The incidence of cytomegalovirus (CMV) viremia was 0.5 in the MUD group and 0.6 in the MMRD group (P = .35). The frequency of CMV disease was high (17%), and the most common manifestation was retinitis. The kinetics of immune recovery was similar in both groups. The overall survival was 0.86 in the MUD group and 0.87 in the MMRD group (P = .95). In our experience, there was no difference in the outcomes of HSCT performed from MUD and MMRD. Hence, given the immediate availability of donors, in the absence of HLA-identical siblings, HSCT with TCRαß+/CD19+ graft depletion from MMRDs can be considered as the first choice in patients with PID.

Phase 2 study of nilotinib in pediatric patients with Philadelphia chromosome-positive chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is rare in children and accounts for ≤15% of all myeloid leukemia cases. When we initiated this study with nilotinib, imatinib was the only tyrosine kinase inhibitor indicated for pediatric patients with Philadelphia chromosome-positive (Ph+) CML in chronic phase (CP); alternative treatment options were needed, particularly for patients who developed resistance or intolerance (R/I) to imatinib. This phase 2 study enrolled pediatric patients with either Ph+ CML-CP R/I to imatinib or dasatinib or newly diagnosed Ph+ CML-CP. Data presented are from analyses with minimum follow-up of up to 24 cycles (1 cycle is 28 days). Fifty-nine patients with Ph+ CML-CP were enrolled, and 58 were treated (R/I, n = 33; newly diagnosed, n = 25). Major molecular response (MMR) rate at cycle 6 in the R/I cohort was 39.4% (primary end point); 57.6% of patients achieved or maintained MMR and 81.8% achieved or maintained complete cytogenetic response (CCyR) by 24 cycles. In patients with newly diagnosed disease, rates of MMR by cycle 12 and CCyR at cycle 12 were 64.0% each (primary end points); by cycle 24, cumulative MMR and CCyR rates were 68.0% and 84.0%, respectively. The safety profile of nilotinib in pediatric patients was generally comparable with the known safety profile in adults, although cardiovascular events were not observed in this study, and hepatic laboratory abnormalities were more frequent; no new safety signals were identified. In summary, nilotinib demonstrated efficacy and a manageable safety profile in pediatric patients with Ph+ CML-CP. This trial was registered at www.clinicaltrials.gov as #NCT01844765.

Immunophenotypic changes of leukemic blasts in children with relapsed/refractory B-cell precursor acute lymphoblastic leukemia, who have been treated with Blinatumomab.

Not available.

Efficacy and safety of ruxolitinib in ineffective erythropoiesis suppression as a pretransplantation treatment for pediatric patients with beta-thalassemia major.

BACKGROUND: Ineffective erythropoiesis (IE) is the most prominent feature of transfusion-dependent beta-thalassemia (TDT), which leads to extramedullary hemopoiesis. The rejection rate in allogeneic hematopoietic stem cell transplantation (HSCT) is high in heavily transfused patients with TDT accompanied by prominent IE. Therefore, a pretransplantation treatment bridging to HSCT is often used to reduce allosensitization and IE. Ruxolitinib is a JAK-1/JAK-2 inhibitor and has showed its efficacy in suppressing IE and the immune system. A previously published study on RUX in adult patients with TDT has revealed that this treatment significantly reduces spleen size and is well tolerated. PROCEDURE: Ten patients (5-14 years old) with TDT and an enlarged spleen were enrolled. The dose of ruxolitinib was adjusted for age: for patients <11 years: 40-100 mg/m2 total daily dose and for patients >11 years: 20-30 mg/m2 total daily dose. HSCT was performed in 8 of 10 patients. RESULTS: After the first 3 months of ruxolitinib therapy, spleen volume decreased in 9 of 10 cases by 9.1%-67.5% (M = 35.4%) compared with the initial size (P = 0.003). The adverse events of ruxolitinib (infectious complications, moderate thrombocytopenia, and headache) were successfully managed by reducing the dose. The outcomes of HSCT were favorable in seven of eight cases. CONCLUSION: Ruxolitinib is promising as a short-term pre-HSCT treatment for pediatric patients with TDT and pronounced IE.

Plerixafor added to G-CSF allows mobilization of a sufficient number of hematopoietic progenitors without impacting the efficacy of TCR-alpha/beta depletion in pediatric haploidentical and genoidentical donors failing to mobilize with G-CSF alone.

BACKGROUND: Collection of a large number of early hematopoietic progenitors is essential for allogeneic apheresis products intended for TCR-alpha/beta depletion. MATERIALS AND METHODS: We added plerixafor 0.24 mg/kg body weight (bw) on day 4 of high-dose filgrastim mobilization 10 hours prior to apheresis in 16 (30.5%) pediatric allogeneic donors who failed to recover a sufficient number of CD34+ cells. RESULTS: On day 4 of G-CSF, the median CD34+ cell count in peripheral blood was 6 per µL (range 4-9 per µL) in 6 poor mobilizers and 16 per µL (range 12-19 per µL) in insufficient mobilizers. In all donors, the threshold of 50 CD34+ cells/µL was achieved, and the median increase was 14.8-fold in poor mobilizers and 6.5-fold in insufficient mobilizers, whereas it was 3.45-fold increase in those mobilized with G-CSF alone. DISCUSSION: In all donors, a predefined number of >10 × 106 CD34+ cells/kg of recipient bw before depletion was reached in the apheresis product. The use of plerixafor did not affect the purity of further TCR-alpha/beta depletion. Side effects were mild to moderate and consisted of nausea and vomiting. CONCLUSION: Thus, the safety and high efficacy of plerixafor was proven in healthy pediatric allogeneic hematopoietic cell donors.

Romiplostim treatment for children with immune thrombocytopenia: Results of an integrated database of five clinical trials.

BACKGROUND: Treatment for chronic immune thrombocytopenia (cITP) in children is largely limited to immunosuppressive agents. Thrombopoietin receptor agonists (TRAs) have been used to treat cITP in adults for over a decade. The objective of this integrated analysis was to examine the safety and efficacy of the TRA romiplostim in children with ITP. METHODS: We examined efficacy and safety in children with ITP across five romiplostim trials: final data from two double-blind placebo-controlled trials and two open-label extensions, and interim data from an ongoing single-arm trial. RESULTS: Patients (n = 24 initially placebo; n = 262 initially romiplostim) had a median age of 10.0 years (Q1: 6.0, Q3: 13.0), ITP duration of 1.9 years (Q1: 1.0, Q3: 4.0), and baseline platelet count of 14.3 × 109 /L (Q1: 7.5, Q3: 23.0). Among 282 patients receiving romiplostim, median treatment duration was 65 weeks (range 8-471 weeks) and median weekly dose was 6.6 µg/kg (range 0.1-9.7 µg/kg). Overall, 89% of romiplostim-treated patients had platelet responses. Nineteen patients (7%) maintained treatment-free responses for ≥6 months while withholding all ITP therapy. Grade 3 and 4 adverse events of bleeding occurred in 10% and <1% of romiplostim-treated patients, respectively. Twenty-five percent of patients had a serious adverse event, most commonly epistaxis (6%). Seven patients (2%) had neutralizing antibodies against romiplostim postbaseline and none had neutralizing antibodies against endogenous thrombopoietin. Efficacy and safety results appeared similar between children with ITP for ≤12 months and >12 months at baseline. CONCLUSIONS: Across five pediatric clinical trials, romiplostim was well tolerated. Most patients had a platelet response; some maintained responses for at least 6 months while withholding all ITP therapy.