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Patients with an ABL-class fusion have a high risk of relapse on standard chemotherapy but are sensitive to tyrosine kinase inhibitors (TKI). In UKALL2011, we screened patients with post-induction MRD ≥1% and positive patients (12%) received adjuvant TKI. As the intervention started during UKALL2011, not all eligible patients were screened prospectively. Retrospective screening of eligible patients allowed the outcome of equivalent ABL-class patients who did and did not receive a TKI in first remission to be compared. ABL-class patients who received a TKI in first remission had a reduced risk of relapse/refractory disease: 0% vs. 63% at four years (P = 0·009).

Methodology This guideline was compiled according to the British Society for Haematology (BSH) process at (http://www.bcshguidelines.com). The Grading of Recommendations Assessment, Development and Evaluation (GRADE) nomenclature was used to evaluate levels of evidence and to assess the strength of recommendations. The GRADE criteria can be found at http://www.gradeworkinggroup.org. Literature review details Ovid MEDLINE and Ovid EMBASE were searched systematically for publications in English from 1980 to the end of 2015 using the key words Transient Abnormal Myelopoiesis, Transient Myeloproliferative Disorder, Transient Leukaemia, and Down Syndrome. Specific searches relating to fetal disease and hepatic parameters were also performed. References from relevant publications were also searched. Working group membership The guideline group was selected to be representative of UK‐based medical experts with invited representatives from the British Association of Perinatal Medicine and the Royal College of Paediatrics and Child Health. Review Review of the manuscript was performed by the BSH Guidelines General Haematology Task Force, the BSH Guidelines Committee and the General Haematology sounding board of BSH. It was also placed on the members section of the BSH website for comment. Further comments were invited from a sounding board of the Childhood Leukaemia Clinicians'27 Network, the Childhood Cancer and Leukaemia Group (CCLG), the Royal College of Paediatrics and Child Health, the British Association of Perinatal Medicine (BAPM) and patient representatives identified through the Down Syndrome Association; these organisations do not necessarily approve or endorse the contents. The objective of this guideline is to provide healthcare professionals with guidance on the investigation and management of patients with Transient Leukaemia of Down Syndrome (TL‐DS). Individual patient circumstances may dictate an alternative approach. This is the first BSH guideline on this topic and is in date at time of publication. Any updates will be posted on the BSH Guidelines website (http://www.bcshguidelines.com).

Children with constitutional trisomy 21 (Down syndrome (DS)) have a unique predisposition to develop myeloid leukaemia of Down syndrome (ML-DS). This disorder is preceded by a transient neonatal preleukaemic syndrome, transient abnormal myelopoiesis (TAM). TAM and ML-DS are caused by co-operation between trisomy 21, which itself perturbs fetal haematopoiesis and acquired mutations in the key haematopoietic transcription factor gene GATA1. These mutations are found in almost one third of DS neonates and are frequently clinically and haematologcially 'silent'. While the majority of cases of TAM undergo spontaneous remission, ∼10 % will progress to ML-DS by acquiring transforming mutations in additional oncogenes. Recent advances in the unique biological, cytogenetic and molecular characteristics of TAM and ML-DS are reviewed here.

Introduction and Objective: Inhibitors to coagulation factor VIII (FVIII) are the most serious complication of haemophilia A treatment. Previously untreated patients (PUPs) are at the greatest risk of inhibitors, which generally occur within the first 20 exposure days (ED) to FVIII. Immune tolerance induction (ITI) is the only clinically proven strategy for eradication of inhibitors. We present a case series of six PUPs with severe haemophilia A and inhibitors who underwent ITI with simoctocog alfa (Nuwiq®), a 4th generation human cell-line-derived recombinant FVIII approved for treatment of haemophilia A. Materials and Methods: Six male PUPs with severe haemophilia A who developed FVIII inhibitors after treatment with simoctocog alfa were started on ITI with simoctocog alfa. Primarily, we assessed the success of simoctocog alfa in patients with inhibitors. Success of ITI was determined based on undetectable inhibitor titre (< 0.6 BU/ml), FVIII recovery ≥ 66% and half-life ≥ 6 hours. Secondary objectives were to assess bleeding rate, tolerability and safety in patients with inhibitors treated with simoctocog alfa ITI. Results: The age of the patients at the start of ITI ranged from 8 to 186 months. Four of the patients were Caucasian, and two were African. All patients had a F8 mutation associated with high risk of ITI failure and two patients had an additional risk factor for ITI failure. The number of EDs prior to inhibitor development ranged from 9 to 33, and the peak inhibitor titre ranged from 0.9 to 114 BU. For ITI, five patients were treated with 100 IU/kg simoctocog alfa daily, and one with 90 IU/kg every other day. One patient achieved complete tolerisation and is now on prophylaxis at normal doses, having achieved an undetectable inhibitor titre after 9 months. This was despite an inhibitor titre ≥ 10 BU/mL at ITI start, which is considered a poor prognosis factor for ITI success. Three other patients achieved an undetectable inhibitor titre after 1, 6 and 18 months of ITI, and FVIII recovery has normalised but half-life remains short and they are on weaning doses as the half-life extends. One patient discontinued ITI with simoctocog alfa after 15 months due to an increasing inhibitor level. This patient was 15 years old at ITI start, and older age is associated with poor ITI outcome. Additionally, his haemophilia A was untreated for 15 years, during which time he developed severe arthropathy. One patient, who started ITI 3 months ago, has an ongoing inhibitor titre and continues on ITI with simoctocog alfa. Conclusions: In a case series of six patients treated with simoctocog alfa for ITI, who all had poor prognosis factors for ITI success, four patients (67%) to date have achieved an undetectable inhibitor titre. These data suggest that ITI with simoctocog alfa may be an effective treatment approach in haemophilia A patients with inhibitors. Disclosures Khair: Shire, SOBI, Pfizer, Roche, Novo Nordisk, Octapharma: Speakers Bureau; shire, SOBI, Pfizer, Roche: Research Funding. Liesner:Roche: Research Funding; Novo Nordisk: Research Funding, Speakers Bureau; Baxalta: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Octapharma: Consultancy, Other: Clinical study investigator for NuProtect Study (Octapharma sponsored), Research Funding, Speakers Bureau; Sobi: Speakers Bureau. Belyanskaya:Octapharma AG: Employment.

In a previous study, we reported that intramuscular (IM) triamcinolone improves symptoms in children with difficult asthma. In 2005, we revised our difficult asthma protocol to include assessment of airway inflammation, both directly using sputum induction and indirectly by measurement of exhaled nitric oxide (eNO). In this retrospective review, we aimed to describe (i) the changes in eNO and symptoms after a single 60 mg dose of IM triamcinolone and (ii) the changes in inflammatory markers in the subgroup with non-eosinophilic asthma (i.e., an induced sputum eosinophil differential count

The classical treatment algorythm of idiopathic severe aplastic anemia (SAA) forsees, if a sibling donor is not available in the family, a first line option represented by immunosuppressive therapy (IST) with ATG and Cyclosporine A (CsA). IST provides a very good survival rate but a fairly high rate of failures (no response, relapse, need for transplant). This is particularly important in childhood and adolescence where faulty hematopoiesis represents a relevant limitation of quality of life. The option of haematopoietic stem cell transplantation (HSCT) from matched unrelated donor (MUD) as front line treatment with no prior failed IST, has never been investigated so far. This study provides for the first time the outcome analysis of 29 consecutive SAA patients who received an upfront unrelated donor HSCT without prior IST, in 9 UK Centres and compares each of these patient with 3 matched controls from the data base of the SAAWP of the EBMT who, in a similar time-span, underwent Matched Sibling Donor (MSD) HSCT. Twenty four patients received HLA-A,-B,-C,-DQ-,-DRB1 matched MUD HSCTs whilst 5 received single antigen/allele Mismatched Unrelated Donor (MMUD) grafts. The conditioning regimen was FCC (Fludarabine, Cyclophosphamide and Alemtuzumab) with the addition of low dose (3cGy) TBI for the MMUD HSCTs. GVHD prophylaxis was with CsA +-Mycophenolate. The primary endpoints were overall survival (OS) and event free survival (EFS). Events were death, disease recurrence, second HSCT, clinical PNH and post-transplant malignancies. Complete remission (CR) was defined as Hb > 10 g/dl, neutrophil count > 1x 109/l and platelet count > 100x109/l. The 87 (3 for each MUD/MMUD HSCT) patients from the EBMT data base who underwent MSD HSCT as first line treatment were matched to the upfront MUD/MMUD cohort by age, gender, time from diagnosis to HSCT and source of stem cells. Their median follow-up was 1.6 years (range 0.01-9.39). In the upfront MUD/MMUD cohort there were 12 males (41%) and 17 females (59%). Median age at HSCT was 8.46 years (range 1.73-19.11), 72% was aged below and 28% above 12 years; median interval from diagnosis to HSCT was 0.39 years (range 0.19-1.35) with 72 % receiving bone marrow and 28% peripheral blood stem cells. The median follow-up was 1.7 years (range 0.19-8.49). The median time to neutrophil recovery (>0.5 x 109/l) was 18 days (range 9-29) and the median time to platelet recovery (>50 x 109/l) was 19 days (range 10-40). The 100 day cumulative incidence (CI) of grade II-IV acute GVHD was 10 ± 6% ; there was only one case of grade III-IV acute GVHD (frequency of 3.5%). The 1 year CI of chronic GVHD was 19 ± 8%. There were 5/29 cases (frequency of 17,2 %), 4 in the MUD and 1 the MMUD subset. Chronic GVHD was limited in all cases and restricted to skin. There were only 2 events in this cohort; one primary graft failure following a HLA-A MMUD HSCT who has now successfully received a second HSCT and one death due to idiopathic pneumonia syndrome. No post-treatment malignancies occurred at last follow-up. The other 27 patients are in CR at last follow-up. The median interval diagnosis-neutrophil recovery was similar in MUD/MMUD (0.39 years; range 0.19-1.35) vs MSD transplants (0,31 years; range 0,1- 0,45) (p=0.93). The 2 year OS was 96%±4% in the upfront MUD/MMUD cohort vs 91%±3% of the MSD cohort (p=0.30). The 2 year EFS was 92%±5% in the upfront cohort vs 87%±4% in MSD (p=0.37) (Fig 1). The 2 year CI of rejection was 4%±4% in the MUD/MMUD vs .1%±1% in the MSD group (p=0.48). This is the first controlled study indicating that in idiopathic SAA of childhood and adolecence upfront MUD/MMUD HSCT using FCC as conditioning regimen, has similar outcome to MSD HSCT. MUD HSCT may be considered a feasible and successful treatment option when children lack a MSD and a MUD is readily available. Figure 1 Figure 1. Comparison of EFS between upfront MUD/MMUD and front-line MSD HSCT. Events were: death, disease recurrence, second HSCT, clinical PNH and post-transplant- malignancies. Table 1 EFS N events 2-yrs Pr (%) (SE) p-value MUD/MMUD 29 2 92 (5) 0.37 MSD 87 11 87 (4) Disclosures Dufour: Pfizer: Consultancy.

In Down syndrome (DS), trisomy 21 (T21) causes perturbation of fetal liver (FL) hematopoiesis leading to expansion of megakaryocyte-erythroid (MK-E) progenitors. On this background, FL hematopoietic stem/progenitor cells (HSPC) may acquire GATA1 gene mutations which usually present as a neonatal preleukemic condition, Transient Myeloproliferative Disorder (TMD). TMD develops only in fetal life and most cases spontaneously regress after birth, suggesting unique features of the T21 fetal microenvironment may be important in driving both abnormal DS FL hematopoiesis and mutant GATA1 clones in TMD. Previous work showed activation of insulin-like growth factor (IGF) signalling in TMD and DS-AMKL and fetal-specific IGF dependence of murine MK development implicating T21 in altered fetal IGF signalling. To investigate the role of IGF signalling in fetal MK-E development in DS FL without GATA1 mutations, we performed gene expression profiling (GEP) of DS FL (n=5) and normal FL CD34+ cells (n=3). GSEA showed significant enrichment of IGF targets. We therefore measured expression of the principal IGF receptor, IGF1R, on DS FL HSPC (n=6). Surface IGF1R was uniformly expressed on all DS FL HSPC subpopulations. However, there was no difference in IGF1R surface or gene expression between DS and normal FL HSPC (n=8) suggesting that increased IGF1R expression on TMD and DS-AMKL cells is an early event and may reflect their fetal rather than T21 origin. To determine if the enrichment of IGF targets in DS FL HSPC might reflect increased IGF production in the FL microenvironment, we compared IGF expression in DS FL mesenchymal stromal cells (MSC)(n=4) and hepatocytes with normal FL MSC (n=4). Both DS and normal FL MSC expressed large amounts of IGF2, but little or no IGF1 with no difference between DS and normal MSC. Similarly, IGF2 was expressed by IHC at similar levels in both DS and normal fetal hepatocytes and MSC whereas IGF1 was barely detectable. Normal and DS fetal bone marrow (BM) MSC also expressed high levels of IGF2, but not IGF1 in contrast to adult BM MSC. Thus, IGF2 is the main IGF produced in the human fetal hematopoietic environment. Consistent with a specific role in DS FL hematopoiesis, IGF2 caused marked proliferation of DS FL clonogenic MK and MK-E cells (n=3) and stimulated MK proliferation in liquid culture while in normal FL, IGF2 stimulated EPO-independent BFU-E and Pre-BFU-E but had no effect on MK cells. Since differential effects of IGF2 on DS/normal FL HSPC might be due to altered expression of the Insulin Receptor (InsR), which binds IGF2 with low affinity, we compared InsR surface and gene expression in DS and normal FL HSPC but found no significant difference. IGF2 also binds to IGF2R, a negative regulator of IGF2, however there was no difference in IGF2R expression between DS and normal FL HSPC. Co-culture of normal FL CD34+ cells with DS or normal FL MSC (n=3) promoted MK and erythroid cell proliferation and differentiation. Since the effect of DS FL MSC on normal FL CD34+ cells was significantly greater (~4-fold) than that of normal FL MSC, the data above suggest this is unlikely to be due to IGF2 alone. To investigate whether T21 alters the MSC secretome, we performed GEP of DS FL MSC (n=3) and compared this with normal FL MSC (n=5). Both normal FL and DS FL expressed known hematopoietic cytokine genes, including SCF, CXCL12, G-CSF, M-CSF, Flt3 and IL-6, as well as IGF2 but not IGF1, EPO or TPO. Of the top 80 differentially expressed genes (Fold Change>2), ~40% encode secreted proteins, including several which affect IGF availability. Conclusion: T21 perturbs FL hematopoiesis through both HSPC-intrinsic mechanisms, including changes in IGF responsiveness, and through alterations to the FL microenvironment. Disclosures No relevant conflicts of interest to declare.

Abstract 11 Stem cell transplantation (SCT) is currently the only curative option for sickle cell disease. Cerebrovascular disease (CVD) is one of the main indications to undertake this procedure as even with best conventional approaches there is a significant risk of recurrence or progression and there is evidence that SCT arrests disease progression, though more detailed study of outcomes is awaited. Early studies of SCT in sickle cell disease showed a high rate of neurological complications that led to the optimization of protocols. We conducted a retrospective analysis of related SCT in children with severe SCD between 2001 and 2010 at our institution to study the effect of transplantation. 20 patients (11 male, 9 female) received a BMT for sickle CVD (n=11) or recurrent vaso-occlusive crises (n=9). One patient with CVD was a second procedure following primary graft failure in a previous sibling transplant. CVD was investigated with clinical history and examination, transcranial Doppler ultrasound, magnetic resonance imaging/magnetic resonance angiography and psychometric testing using WISC-IV: 7 patients had no evidence of CVD, 5 had silent infarcts, 6 ischaemic stroke and 2 Moya-Moya disease. The median age at transplantation was 136 months (range 34 – 210 months). Donor source was HLA-matched siblings in 18 patients, one 9/10 mismatched sibling and HLA-matched relative in another. Bone marrow was used in all (n=19) but one patient who received combined bone marrow and umbilical cord. All patients (n=18) but two received conditioning with oral busulfan 14 mg/kg, cyclophosphamide 200 mg/kg and alemtuzumab 0.3 mg/kg; 1 patient received fludarabine 160 mg/m2, treosulfan 42 mg/m2, thiotepa 10mg/kg and ATG (Thymoglobulin) 11.25 mg/kg and 1 patient received oral busulfan 16mg/kg, cyclophosphamide 200 mg/kg and antilymphocyte globulin (45 mg/kg). GvHD prophylaxis was provided with ciclosporin and short course methotrexate (n=18), ciclosporin and MMF (n=1) and ciclosporin alone (n=1). Mean cell dose was 3.70 × 108 TNC/kg (range 1.45 – 6.16 × 108 TNC/kg). Neutrophil engrafment (>0.5 × 109/L) occurred at a median of 19.5 days (range 12 – 28 days) and platelet engrafment (>50 × 109/L) at median of 26 days (range 21 – 52 days). The median follow up is 974 days (range 270 – 3622 days). 18 patients achieved stable donor haemopoiesis, one patient suffered secondary graft failure due to Parvovirus B19 infection and one patient died on day +21 post-transplant due to sepsis and multi-organ failure. No significant sickle related neurological events occurred during these transplants. All 18 patients with long-term engraftment achieved radiological stabilization of the underlying CVD. Imaging performed at least 12 months post SCT showed no further changes from pre-transplant images. There were no clinical neurological events after SCT. Psychometric testing demonstrated improvements in all areas in patients transplanted for silent infarcts, particularly those affecting processing speed. In summary, SCT appears safe even in patients with severe CVD, arrests further progression and shows functional improvement. Disclosures: No relevant conflicts of interest to declare.

Abstract 1673 Introduction: Mature B-cell lymphoproliferative disorders that present with a leukemic phase may have overlapping morphological and immunophenotypic features. Accurate diagnosis is essential to determine prognosis and therapy. B-cell chronic lymphocytic leukaemia (B-CLL) and mantle cell lymphoma (MCL) both express CD5 but usually have divergent clinical courses. Conventional markers are able to discriminate in many cases but a significant proportion of cases require more detailed analysis. CD200 is a membrane glycoprotein that has been reported to differentiate between B-CLL and MCL. It is expressed on resting and activated T and B cells, but not on NK cells, monocytes, granulocytes or platelets. We prospectively assessed the utility of this antibody in a single centre, servicing haematology units in North London. Methods: Over a 12 month period we prospectively assessed the expression of CD200 (Clone MRC OX-104, BD Pharmingen) on neoplastic cells of patients with presenting with mature B-cell lymphoproliferative disorders. EDTA anti-coagulated peripheral blood and bone marrow underwent a lyse/wash technique before being acquired on a BD FACS Canto II flow cytometer equipped with DIVA 6.1.2 software. A lymphoid gating strategy was used to analyse the data and expression of more than 20% of nucleated cells referenced to a negative internal control was considered positive. A diagnosis was made using all available data according to the WHO classification of haematopoietic tumours, including the 5 point CLL score. The predictive value of CD200 expression was subsequently assessed. Results: There were 100 patients (58M: 42F) with a median age of 70 years (range 29–92). CD200 was present on the neoplastic cells of all 78 patients with B-CLL; in all 7 MCL patients CD200 was negative; 15 patients had CD5 negative B-cell lymphoproliferative disorder with variable expression of CD200. The specificity of CD200 negativity in the setting of CD5 positive B-cell clone was 100% for MCL. The positive predictive value of CD200 for CLL was 97.5% with a sensitivity of 100% and a Pearson's correlation coefficient of 1. Conclusion: Our results confirm CD200 expression in the neoplastic cells of B-CLL patients but not in MCL. This antibody may contribute to the accurate differentiation between B-CLL and MCL in patients presenting with the diagnostic problem of a CD5- positive lymphoproliferative disorder. We propose to add CD200 to our diagnostic B-cell lymphoma panel. Further studies are needed to determine whether CD200 could replace other immunophenotypic strategies currently used in this situation, such as CD23, FMC7 and intensity of CD22/CD79b expression. Disclosures: No relevant conflicts of interest to declare.