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INTRODUCTION We have previously described AUTO1, a CD19 CAR with a fast off-rate CD19 binding domain, designed to reduce CAR-T immune toxicity and improve engraftment. Its clinical activity has been tested in r/r paediatric and adult B-ALL. Cumulatively, this data confirms the intended function of the receptor, with low levels of CRS/ICANS and long-term engraftment of CAR T-cells observed in both patient groups. Recently, CAR-T therapy has been explored in indolent lymphomas such as follicular (FL) and mantle cell lymphoma (MCL), but a high incidence of toxicity including Grade 3-4 ICANS has been reported. We have initiated testing of AUTO1 in the setting of indolent and high-grade B-NHL and CLL (NCT02935257). METHODS Manufacturing: CAR T-cell products were generated using a semi-automated closed process from non-mobilised leukapheresate. Study design: Subjects ≥ 16y underwent lymphodepletion with fludarabine (30mg/m 2 x3) and cyclophosphamide (60mg/kg x1) prior to AUTO1 infusion, with the exception of the DLBCL cohort who additionally received a single dose of pembrolizumab (200mg) on day -1 to potentiate CAR-T expansion. AUTO1 dose varies based on the indication. Split dosing of 230 x10^6 CD19 CAR T-cells at day 0 and day 9 is employed in the CLL cohort. A single dose of 200 x10^6 CD19 CAR T-cells is delivered to patients with B-NHL. Study endpoints include feasibility of manufacture, grade 3-5 toxicity and remission rates at 1 and 3 months. RESULTS As of 17th May 2021, we recruited 13 patients: 7 with FL, 4 with MCL, 1 DLBCL and 1 CLL. Apheresis and product manufacture was successful in all 13 patients and 9 patients were infused: 7 with FL and 2 with MCL. Three patients (1 DLBCL, 1 CLL and 1 MCL) were pending infusion at time of data cut-off and 1 patient (MCL) died due to Covid-19 prior to infusion. Patients treated with AUTO1 had a median age of 56 years (range 39-68y), had received a median of 3 prior lines of treatment (range 2-5) and all patients had stage IV disease at screening. Grade 1 CRS was reported in 4/9 and Grade 2 CRS in 1/9. 1/9 developed MAS which resolved with anakinra/dexamethasone. No ICANS was observed on study. Excellent CAR engraftment was observed and 9/9 patients were in CMR by 18FDG PET-CT post-treatment. At a median of 6.1 months (range 4.0-8.1m), 8/9 patients were disease free at last follow-up. One patient died in CMR at month 5.6 of COVID-19. CONCLUSION AUTO1 has a tolerable safety profile in adult patients with r/r B-NHL despite high disease burden. Early data shows 100% complete remission rates and excellent CAR engraftment/expansion. Additional MCL, CLL and DLBCL patients, updated data and longer follow up will be presented. Disclosures Roddie: Celgene: Consultancy, Speakers Bureau; Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau. Hartley: Astra Zeneca: Ended employment in the past 24 months; ADC Therapeutics: Consultancy, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company. Farzaneh: Autolus: Consultancy, Current equity holder in publicly-traded company. Lowdell: Autolus: Consultancy, Current equity holder in publicly-traded company. Linch: Autolus: Consultancy, Current equity holder in publicly-traded company. Pule: Autolus: Current Employment, Current equity holder in publicly-traded company. Peggs: Autolus: Consultancy, Current equity holder in publicly-traded company.

TO THE EDITOR: Addition of the CD33-targeted immunoconjugate gemtuzumab ozogamicin (GO; Pfizer) has been shown to improve the response to standard-induction chemotherapy and results in better long-term survival in adult patients with acute myeloid leukemia (AML).[1][1] The greatest impact was

Introduction: Prognosis for adult B-cell Acute Lymphoblastic Leukaemia (B-ALL) is poor and there is currently no licensed CD19 Chimeric Antigen Receptor (CAR) therapeutic. We developed a novel CD19 CAR (CAT-41BBz CAR) with a fast off-rate, designed to result in more physiological T-cell activation, reduce toxicity and improve engraftment. We describe updated data from the Phase I ALLCAR19 (NCT02935257) study of AUTO1 in relapsed/refractory adult B-ALL. Methods: Manufacturing: AUTO1 utilises non-mobilised autologous leukapheresate. The first 6 products were generated using a standard dynabead/WAVE bioreactor process and subsequent products using a semi-automated closed process. Study design: Patients aged >16y underwent lymphodepletion with fludarabine (30mg/m2 x3) and cyclophosphamide (60mg/kg x1) followed by split dose CAR T-cell infusion (Day 0: if ≥20% Bone Marrow (BM) blasts, infuse 10 x 106 CAR T-cells; if Results: As of 13 May 2020, 24 patients have been leukapheresed, 23 products manufactured and 19 patients received at least 1 dose of AUTO1. The median age was 43y (range 18-62), 26% had prior blinatumomab, 47% had prior inotuzumab ozogamicin and 63% had prior hematopoietic stem cell transplantation (HSCT). At the time of pre-conditioning, 42% had ≥50% BM blasts. No patients experienced ≥Grade 3 CRS (Lee criteria), 3/19 (16%) experienced Grade 3 ICANS that swiftly resolved with steroids. Of 19 infused patients, 16/19 (84%) achieved Minimal Residual Disease (MRD) negative complete response (CR). Currently 6 patients have died, none related to AUTO1. 11/19 (58%) patients remain on study and continue in MRD negative remission at a median follow up of 12.2 months (range 0.6-24.4m). To date, only 2 patients underwent HSCT whilst in remission. For all treated patients, the event-free survival (EFS) at 6 months was 62% and 76% for those whose products were manufactured using the closed process. Patients exhibited robust CAR expansion (mean peak CAR T levels 716,769 copies/µg DNA). Conclusions: AUTO1 has a tolerable safety profile in adult patients with r/r B-ALL despite high disease burden. Early data shows high remission rates with 84% achieving MRD negative CR. This preliminary data supports the further development of AUTO1 as a standalone treatment in patients with r/r B-ALL. Data from additional patients and longer follow up will be presented. Furthermore, data from extension cohorts of patients with low- and high- grade B-cell Non-Hodgkin's lymphoma and chronic lymphocytic leukaemia will be presented. Figure Disclosures Roddie: Celgene: Honoraria; Gilead: Honoraria; Novartis: Honoraria. O'Reilly:Gilead: Honoraria; Novartis: Honoraria, Other: Travel support. Hartley:ADC Therapeutics: Consultancy, Current equity holder in publicly-traded company, Research Funding. Linch:Autolus: Consultancy. Pule:UCLB: Patents & Royalties; Mana Therapeutics: Other: entitled to share of revenue from patents filed by UCL; Autolus: Current Employment, Other: owns stock in and receives royalties, Patents & Royalties. Peggs:Autolus: Consultancy.

Acute myeloid leukemia with t(8;21)(q22;q22) is characterized by considerable clinical and biological heterogeneity leading to relapse in up to 40% of patients. We sequenced coding regions or hotspot areas of 66 recurrently mutated genes in a cohort of 331 t(8;21) patients. At least 1 mutation, in addition to t(8;21), was identified in 95%, with a mean of 2.2 driver mutations per patient. Recurrent mutations occurred in genes related to RAS/RTK signaling (63.4%), epigenetic regulators (45%), cohesin complex (13.6%), MYC signaling (10.3%), and the spliceosome (7.9%). Our study identified mutations in previously unappreciated genes: GIGYF2, DHX15, and G2E3. Based on high mutant levels, pairwise precedence, and stability at relapse, epigenetic regulator mutations were likely to occur before signaling mutations. In 34% of RAS/RTKmutated patients, we identified multiple mutations in the same pathway. Deep sequencing (∼42 000×) of 126 mutations in 62 complete remission samples from 56 patients identified 16 persisting mutations in 12 patients, of whom 5 lacked RUNX1-RUNX1T1 in quantitative polymerase chain reaction analysis. KIThigh mutations defined by a mutant level ≥25% were associated with inferior relapse-free survival (hazard ratio, 1.96; 95% confidence interval, 1.22-3.15; P = .005). Together with age and white blood cell counts, JAK2, FLT3-internal tandem duplicationhigh, and KIThigh mutations were identified as significant prognostic factors for overall survival in multivariate analysis. Whole-exome sequencing was performed on 19 paired diagnosis, remission, and relapse trios. Exome-wide analysis showed an average of 16 mutations with signs of substantial clonal evolution. Based on the resemblance of diagnosis and relapse pairs, genetically stable (n = 13) and unstable (n = 6) subgroups could be identified.

A compact marker/suicide gene that utilizes established clinical-grade reagents and pharmaceuticals would be of considerable practical utility to T-cell cancer gene therapy. Marker genes enable measurement of transduction and allow selection of transduced cells, whereas suicide genes allow selective deletion of administered T cells in the face of toxicity. We have created a highly compact marker/suicide gene for T cells combining target epitopes from both CD34 and CD20 antigens (RQR8). This construct allows selection with the clinically approved CliniMACS CD34 system (Miltenyi). Further, the construct binds the widely used pharmaceutical antibody rituximab, resulting in selective deletion of transgene-expressing cells. We have tested the functionality of RQR8 in vitro and in vivo as well as in combination with T-cell engineering components. We predict that RQR8 will make T-cell gene therapy both safer and cheaper.

Some studies have suggested that cases of acute myeloid leukemia (AML) with low levels of FLT3 internal tandem duplications (FLT3(ITD)) do not have a worse prognosis if there is a concomitant NPM1 mutation, although this is controversial. To clarify this therapeutically important issue, we have analyzed FLT3(ITD) and NPM1(MUT) levels in 1609 younger adult cases of cytogenetically intermediate-risk AML. The cumulative incidence of relapse was increased in NPM1(MUT) cases by the presence of a FLT3(ITD), but did not differ markedly according to FLT3(ITD) level. This remained true when allowance was made for poor leukemic cell purity by adjustment of the FLT3(ITD) level to the measured NPM1(MUT) level. If consolidation therapies are to be determined by relapse risk, then NPM1(MUT) cases with low-level FLT3(ITD) should not be considered as good risk without further studies. AML 12 and AML 15 are registered at http://www.controlled-trials.com under ISRCTN17833622 and ISRCTN17161961, respectively.

Introduction: 2nd generation CD19 CAR T cells show unprecedented efficacy in B-ALL, but several challenges remain: (1) scaling manufacture to meet patient need and (2) feasibility of generating products from lymphopenic patients post allogeneic stem cell transplant (allo-SCT). To overcome these issues we propose: (1) use of the CliniMACS Prodigy (Miltenyi Biotec), a semi-automated cGMP platform that simplifies CAR T cell manufacture and (2) the use of matched donor T cells to overcome the challenge posed by patient lymphopenia, albeit this may come with a heightened risk of graft versus host disease (GvHD). CARD (NCT02893189) is a Phase I study of matched donor derived CD19 CAR T cells generated on the CliniMACS Prodigy in 14 adult patients with relapsed/refractory (r/r) B ALL following allo-SCT. We additionally explore the requirement for lymphodepletion (LD) in the allogeneic CAR T cell setting and report on the incidence of GvHD with this therapy. Methods: Manufacturing: CARD utilises non-mobilised matched donor leucapheresate to manufacture 2nd generation CD19CAR T cells using a closed CliniMACS® Prodigy/ TransACTTM process. Study design: Eligible subjects are aged 16-70y with r/r B ALL following allo SCT. Study endpoints include feasibility of CD19CAR T cell manufacture from allo-SCT donors on the CliniMACS Prodigy and assessments of engraftment and safety including GvHD. To assess the requirement for LD prior to CD19CAR T cells in lymphopenic post-allo-SCT patients, the study is split into Cohort 1 (no LD) and Cohort 2 (fludarabine (30 mg/m2 x3) and cyclophosphamide (300mg/m2 x3)). To mitigate for the potential GvHD risk, cell dosing on study mirrors conventional donor lymphocyte infusion (DLI) schedules and is based on total CD3+ (not CAR T) cell numbers: Dose 1=1x106/kg CD3+ T cells; Dose 2= 3x106/kg CD3+ T cells; Dose 3= 1x107/kg CD3+ T cells. Results: As of 26 July 2019, 17 matched allo SCT donors were leukapheresed and 16 products were successfully manufactured and QP released. Patient demographics are as follows: (1) median patient age was 43y (range 19-64y); (2) 4/17 had prior blinatumomab and 5/17 prior inotuzumab ozogamicin; (3) 7/17 had myeloablative allo SCT and 10/17 reduced intensity allo SCT of which 6/17 were sibling donors and 12/17 were matched unrelated donors. No patients with haploidentical transplant were enrolled. To date, 12/16 patients have received at least 1 dose of CD19CAR T cells: 7/16 on Cohort 1 and 5/16 on Cohort 2 (2/16 are pending infusion on Cohort 2 and 2/16 died of fungal infection prior to infusion). Median follow-up for all 12 patients is 22.9 months (IQR 2.9-25.9; range 0.7 - 25.9). At the time of CAR T cell infusion, 7/12 patients were in morphological relapse with >5% leukemic blasts. Despite this, CD19CAR T cells were administered safely: only 2/12 patients experienced Grade 3 CRS (UPenn criteria), both in Cohort 1, which fully resolved with Tocilizumab and corticosteroids. No patients experienced ≥Grade 3 neurotoxicity and importantly, no patients experienced clinically significant GvHD. In Cohort 1 (7 patients), median peak CAR expansion by flow was 87 CD19CAR/uL blood whereas in Cohort 2 (5 patients to date), median peak CAR expansion was 1309 CD19CAR/uL blood. This difference is likely to reflect the use of LD in Cohort 2. CAR T cell persistence by qPCR in Cohort 1 is short, with demonstrable CAR in only 2/7 treated patients at Month 2. Data for Cohort 2 is immature, but this will also be reported at the meeting in addition to potential mechanisms underlying the short persistence observed in Cohort 1. Of the 10 response evaluable patients (2/12 pending marrow assessment), 9/10 (90%) achieved flow/molecular MRD negative CR at 6 weeks. 2/9 responders experienced CD19 negative relapse (one at M3, one at M5) and 3/9 responders experienced CD19+ relapse (one at M3, one at M9, one at M12). 4/10 (40%) response evaluable patients remain on study and continue in flow/molecular MRD negative remission at a median follow up of 11.9 months (range 2.9-25.9). Conclusions: Donor-derived matched allogeneic CD19 CAR T cells are straightforward to manufacture using the CliniMACS Prodigy and deliver excellent early remission rates, with 90% MRD negative CR observed at Week 6 in the absence of severe CAR associated toxicity or GvHD. Peak CAR expansion appears to be compromised by the absence of LD and this may lead to a higher relapse rate. Updated results from Cohorts 1 and 2 will be presented. Disclosures Roddie: Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. O'Reilly:Kite Gilead: Honoraria. Farzaneh:Autolus Ltd: Equity Ownership, Research Funding. Qasim:Autolus: Equity Ownership; Orchard Therapeutics: Equity Ownership; UCLB: Other: revenue share eligibility; Servier: Research Funding; Bellicum: Research Funding; CellMedica: Research Funding. Linch:Autolus: Membership on an entity's Board of Directors or advisory committees. Pule:Autolus: Membership on an entity's Board of Directors or advisory committees. Peggs:Gilead: Consultancy, Speakers Bureau; Autolus: Membership on an entity's Board of Directors or advisory committees.

Introduction: In adults, prognosis for B-ALL is poor, patients are more vulnerable to CD19 CAR immunotoxicity and there is currently no CD19 CAR therapeutic with acceptable toxicity and durable efficacy. We have developed a novel second generation CD19CAR (CAT-41BBz CAR), with a faster off-rate but equivalent on rate than the FMC63-41BBz CAR (Kd 116 nM vs 0.9 nM, T1/2 9s vs 4.2 hours) designed to result in more physiological T-cell activation, reduce toxicity and improve engraftment. Preliminary paediatric clinical data of this novel CD19 CAR (AUTO1) supports this assertion. We here describe preliminary data from ALLCAR19 (NCT02935257), a multi-centre, Phase I clinical study of AUTO1 as therapy for r/r adult B-ALL. Methods: Manufacturing: AUTO1 utilises non-mobilised autologous leucapheresate. The first 6 trial products were generated using a standard dynal bead/WAVE Bioreactor process and subsequent products using a semi-automated closed process. Study design: ALLCAR19 is a phase I/II study recruiting subjects 16-65y with r/r B ALL. Lymphodepletion with fludarabine (30mg/m2 x3) and cyclophosphamide (60mg/kg x1) is followed by split dose CAR T cell infusion (Day 0: if ≥20% BM blasts, infuse 10 x 106 CAR T cells ; if Results: As of 24 July 2019, 16 patients have been leukaphresed, 14 products manufactured (one failed leukaphresis and one currently in manufacture) and 13 patients have received at least 1 dose of AUTO1. Of the 16 patients, median age was 35.5 (range 18-63), 10/16 (63%) had prior blinatumomab or inotuzumab ozogamicin and 12/16 (75%) had prior HSCT. At the time of pre-conditioning, 9/13 (69%) patients were in morphological relapse with >5% leukemic blasts of which 6/13 (46%) had ≥50% blast. 9/13 patients (69%) received the total target split dose of 410 x 106 CAR T cells while 1/13 patients (8%) received a reduced split total dose of 51.3 x 106 CAR T cells due to manufacturing constraints. 3/13 patients (23%) received only a first dose of 10 x 106 CAR T cells. The dose was administered safely to date: No patients experienced ≥Grade 3 CRS (using Lee criteria) and only 1/13 (8%) experienced Grade 3 neurotoxicity (dysphasia) that resolved swiftly with steroids. All patients had robust CAR expansion (median peak expansion 172 CAR/uL blood). Of the 13 patients dosed (1/13 pending 28 day follow up), 10/12 (83%) achieved MRD negative CR at 1 month and all patients had ongoing CAR T cell persistence at last follow up. Two patients experienced CD19 negative relapse (one at M3, one at M6), 1 patient died on D17 before first response evaluation, 1 died in molecular CR from sepsis, and 1 died from persistent disease. Currently, 7/12 remain on study and continue in flow/molecular MRD negative remission with a median follow up of 9.0 months (range 1.2-14.8). Conclusions: AUTO1 delivers excellent early remission rates with initial data showing 83% MRD negative CR and robust CAR expansion and persistence. Despite high tumour burden, the safety profile compares favourably to other CD19 CARs, with no cases of severe CRS and only one case of Gr3 neurotoxicity. This is consistent with experience in the paediatric cohort. Updated results will be presented. Disclosures Roddie: Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. O'Reilly:Kite Gilead: Honoraria. Farzaneh:Autolus Ltd: Equity Ownership, Research Funding. Linch:Autolus: Membership on an entity's Board of Directors or advisory committees. Pule:Autolus: Membership on an entity's Board of Directors or advisory committees. Peggs:Gilead: Consultancy, Speakers Bureau; Autolus: Membership on an entity's Board of Directors or advisory committees.

Myelodysplastic syndromes (MDSs) are a group of hematopoietic disorders affecting the myeloid lineage, characterized by cytopenias and clonal evolution to acute myeloid leukemia (AML). We hypothesized that natural killer (NK) cells and their activating killer immunoglobulin-like receptors (aKIRs) influence the immune surveillance and clinical outcome of patients with MDSs. Here, we first examined the distribution of aKIR genes and haplotype in 2 independent cohorts of MDS and AML patients. The median number of aKIR genes was lower in MDS patients than healthy controls (2 vs 3 genes; P = .001), and lower in patients with secondary AML (progressed from MDSs) compared with de novo AML patients (2 vs 3; P = .008) and healthy controls (2 vs 3; P = .006). In a multivariate analysis, the presence of KIR haplotype A (characterized by low aKIR content 0-1) independently predicted a higher risk of conversion to AML (relative risk [RR] with 95% confidence interval [CI], 2.67 [1.13-6.71]; P = .02) and worse adjusted progression-free survival (RR with 95% CI, 2.96 [1.59-5.52]; P = .001) and overall survival (2.25 [1.17-4.31]; P = .02), compared with KIR haplotype B (multiple aKIR genes). These novel findings may help to identify MDS patients with a high risk of disease progression who would likely benefit from adoptive NK-cell therapy.

We have investigated the prognostic significance of isocitrate dehydrogenase 2 (IDH2) mutations in 1473 younger adult acute myeloid leukemia patients treated in 2 United Kingdom Medical Research Council trials. An IDH2 mutation was present in 148 cases (10%), 80% at R140 and 20% at R172. Patient characteristics and outcome differed markedly between the 2 mutations. IDH2R140 significantly correlated with nucleophosmin mutations (NPM1MUT), whereas IDH2R172 cases generally lacked other molecular mutations. An IDH2R140 mutation was an independent favorable prognostic factor for relapse (P = .004) and overall survival (P = .008), and there was no significant heterogeneity with regard to NPM1 or FLT3 internal tandem duplication (FLT3/ITD) genotype. Relapse in FLT3/ITDWTNPM1MUTIDH2R140 patients was lower than in favorable-risk cytogenetics patients in the same cohort (20% and 38% at 5 years, respectively). The presence of an IDH2R172 mutation was associated with a significantly worse outcome than IDH2R140, and relapse in FLT3/ITDWTNPM1WTIDH2R172 patients was comparable with adverse-risk cytogenetics patients (76% and 72%, respectively).

Introduction: Patients with Acute Myeloid Leukaemia (AML) who harbour a FLT3-ITD mutation have a worse prognosis characterised by increased early relapse. Outcomes following relapse in such patients are typically poor, not only because of earlier relapse, but also because of worse performance post-relapse than those who have the same remission duration but are FLT3-ITD WT. In a single centre retrospective study among relapsed patients, Ravandi et al [1] found a remission rate of 24% and median survival of only 13 weeks. There are therefore twin challenges in this population: first to reduce the early relapse rate, and also to develop more effective treatments post relapse. In the recent QUANTUM-R trial [2] for patients with relapsed or refractory disease, single agent quizartinib (AC220) was found to significantly improve median survival from 20.4 weeks to 27 weeks when compared to "doctor's choice" treatment (low-dose ara-C, MEC or FLAG-Ida). There is however, no directly comparable data for the population in the QUANTUM-R trial. To contextualise these results, especially given the potentially different outcomes by control treatment, we looked at outcomes in the UK NCRI AML15,16,17 trials in patients satisfying the eligibility criteria of QUANTUM-R. Methods: Patients aged 18+ in the UK NCRI AML15,16,17 trials were identified who harboured a FLT3 ITD mutation, were treated with intensive chemotherapy, and were either refractory to two courses of induction therapy, or relapsed within six months of transplant, or did not receive a prior transplant and had a remission duration of 6 months or less. Patients were grouped hierarchically as refractory, relapsed post transplant, or relapsed without prior transplant. Eligibility was established at the point a patient first became eligible for analysis. The primary outcome was overall survival (OS), measured from point of eligibility, with subsequent remission with or without count recovery as secondary outcome. A sensitivity analysis was performed excluding those who died within 21 days of eligibility to eliminate patients who might be thought of as too unwell to enter a post-relapse trial. Cox regression was used to identify prognostic factors for survival. Results: A total of 264 patients were identified (refractory n=58, relapsed post SCT n=49, relapsed without SCT n=157). The median age was 51 (range 18-84); 25% of patients were aged 60 or older; 44% were male, 95% had intermediate cytogenetics; 11% had secondary disease. Split by age, among those under 60 45 were refractory, 44 relapsed post SCT and 110 relapsed without SCT; for ages 60+ the figures were 13 vs 5 vs 47. Overall 17% of patients experienced a subsequent remission; with median survival of 86 days and 1 year OS of 13%. If deaths within 21 days were excluded, the remission rate improved to 21%; with a median survival of 133 days and 1 year OS of 16%. In multivariable Cox regression, age group HR for age>60 1.81 (1.33-2.47) p=0.0002) and route to eligibility (HR refractory vs relapsed no SCT 0.77 (0.55-1.07); relapsed post SCT vs no SCT 1.58 (1.11-2.25) p=0.003) were the only factors affecting survival - in particular sex, secondary disease, and ITD allelic burden were not significant. In the sensitivity analyses, only age was significant (HR 1.77 (1.24-2.53) p=0.001); with route to eligibility not significant (p=0.14). Among patients with post-relapse treatment information, 65% were treated intensively, 8% non-intensively, and 20% with palliation - other patients received experimental therapies. When restricting attention to those treated intensively, median survival was 130 days with 17% 1 year OS. Figures were not materially changed if early death was excluded. Of 215 patients who had not relapsed post transplant, 53 (25%) received a transplant post-eligibility. In these 56 patients, median survival was 301 days with 42% alive at one year. Conclusions: In relapsed/refractory AML, outcomes for FLT3-ITD mutated patients are generally poor and worse for older patients. Applying the eligibility criteria of QUANTUM-R and excluding early deaths gives outcomes comparable to the control group of the QUANTUM-R study. In the 25% of patients who proceeded to transplant survival was extended indicating that a treatment which can deliver patients to transplant has the potential to improve patient outcomes. References: [1] Ravandi F, et al. Leuk Res. 2010;34(6):752-756; [2] Cortes et al. EHA 2018, Abstr LB2600. Table. Table. Disclosures Hills: Daiichi Sankyo: Consultancy, Honoraria. Russell:Daiichi Sankyo: Consultancy; Pfizer: Consultancy, Honoraria, Speakers Bureau; Jazz Pharma: Speakers Bureau.

Introduction: The increasing delineation of acute myeloid leukemia (AML) has identified a number of genetic mutations which may be amenable to targeted therapies. However, such mutations typically only occur in a minority of patients, and this relative paucity presents challenges in drug development. Even for more common mutations such as FLT3 ITD, randomised trials can take many years to complete, and there is the issue of how to deal with patients who are tested but not eligible. Earlier phase trials therefore tend to be single arm studies, and often recruit in the relapsed/refractory population, where eligibility is known up front, and it is possible to obtain an early read out for efficacy. Such is the case for the recent evaluations of enasidenib and ivosidenib in IDH1/2 mutated patients. However, with single-arm studies there a need to contextualise results. We therefore looked at outcomes from the United Kingdom NCRI trials of AML for patients with IDH1/IDH2 mutations who were relapsed or refractory to therapy. Methods: A database search identified patients within the UK NCRI AML trials with an IDH1/IDH2 mutation, who had received intensive induction and who were either: in second relapse, relapsed post-transplant, refractory to two courses of induction, or who relapsed within 1 year of remission. Outcomes were measured from the point of eligibility: patients who were multiply eligible were included only once, at their first point of eligibility. The primary outcome was overall survival, with achievement of complete remission, with or without peripheral count recovery, as secondary outcome. Cox regression analysis was used to identify prognostic factors within the cohort of patients. Cytogenetics are evaluated using the MRC classification. Results: A total of 757 patients were identified with IDH1/2 mutation (IDH1 alone n=247; IDH2 alone n=504, both n=6). Of these 211 patients satisfied the relapsed/refractory criteria (IDH1 alone n=81; IDH2 alone n=128; both IDH1/2 n=2; refractory n=28; relapsed post SCT n=34; relapsed within 1 year with no SCT n=138; second relapse n=11 - Table). Median age was 54 years (range 22-77); 51% were male; and 95% of patients had intermediate risk cytogenetics. Remissions were achieved in 43/211 patients (20%; refractory 50%; relapsed post SCT 15%; relapsed within 1 year 17%; second relapse 9% - Table). Patients with IDH1 mutations had a remission rate of 23%; for IDH2 mutated patients, the rate was 18%. Median survival was 4.4 months for IDH1 mutated patients, and 6.6 months for IDH2 mutations; 2 year survival was 17%, 21% respectively. Split by age, median survival was 4.0 and 9.4 months respectively (2-year survival 19%; 27%) for patients aged Conclusions: These results give context to the recent findings in single arm studies of ivosidenib for relapsed/refractory IDH1 mutated patients, and enasidenib for patients harbouring an IDH2 mutation. In the two studies reported, median survival was respectively 8.8 and 9.3 months, compared to 4.4 and 6.6 months in a younger group of patients identified from the UK NCRI AML trials treated with a variety of therapies. In both monotherapy trials the median survival was extended: however, reported one-year survival was not greatly improved (enasidenib 1 year survival 39% vs 34% for the NCRI cohort; ivosidenib, approximately 35% vs 32%). The difference in survival for IDH2 mutated patients in the NCRI cohort, by age and route to eligibility indicates that the interpretation of the results of single arm studies, in a heterogeneous condition such as AML, is fraught with difficulties. Ideally the magnitude of benefit should be assessed using randomised data from large scale collaborations and platform trials. Table: Outcomes for IDH1/IDH2 mutated relapsed/refractory patients in the UK NCRI AML trials. Disclosures Hills: Daiichi Sankyo: Consultancy, Honoraria. Russell:Daiichi Sankyo: Consultancy; Jazz Pharma: Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau.

Background: The International Prognostic Index (IPI) was first described in 1993 and is the most widely used prognostication tool in diffuse large B-cell lymphoma (DLBCL). Five independent risk factors for OS: age (≤60 yrs versus >60 yrs), stage (I/II versus III/IV), number of extranodal (EN) sites (≤1 versus >1), performance status (PS) (0-1 versus ≥2) and serum lactate dehydrogenase (LDH) (normal versus elevated) were used to design a prognostic model which stratified patients into 4 prognostic groups according to the number of risk factors present: low (0-1), low-intermediate (2), high-intermediate (3), and high-risk (4-5); predicting 5-yr OS rates of 73%, 51%, 43% and 26% and 5-yr relapse-free survival (RFS) rates of 70%, 50%, 49%, 40% respectively. For patients aged ≤60 yrs 3 risk factors (stage, PS and LDH level) remained independently significant for OS, and an age-adjusted (aa) model (the aa-IPI) was proposed which predicted 5-yr OS for the low (0), low-intermediate (1), high-intermediate (2) or high-risk (3) groups of 83%, 69%, 46% and 32% respectively (Shipp et al, 1993). The British Columbia Cancer Agency re-evaluated the role of IPI in the rituximab era in their registry-based cohort of 365 patients in 2007. Although the IPI remained predictive, only 2 (rather than 4) prognostic groups were identified and the authors recommended use of the Revised-IPI (R-IPI) where redistribution of the absolute number of IPI risk factors better stratified patients into 3 prognostic groups: very good (0) good (1,2) and poor (3-5) (Savage et al, 2007). However, a subsequent analysis of pooled data from 3 prospective trials (Ziepert et al, 2010) confirmed that the IPI remained highly predictive of outcomes in the rituximab era. Here we report an evaluation of prognostic indices within the UK NCRI R-CHOP 14 vs 21 prospective trial cohort (Cunningham et al, 2013). Methods: The IPI and R-IPI were applied to the R-CHOP 14 versus 21 trial cohort (n=1,080) and for the subgroup of patients aged ≤60 yrs (n=515) and correlated with OS and progression-free survival (PFS). For patients aged ≤60 yrs the aa-IPI was applied in addition. It was not possible to evaluate the NCCN-IPI in our cohort as absolute LDH values were not collected at enrolment. The association between baseline clinical factors (age, gender, PS, stage, presence of >1 EN site of disease, presence of an elevated LDH, disease bulk and B symptoms) and patient outcomes were investigated in univariable and multivariable analysis (MVA). Performance of the prognostic indices was compared using the Concordance Probability Estimate (CPE) and Akaike's Information Criterion (AIC): CPE evaluates discriminatory power to assess the strength of statistical models (higher values indicate better discrimination); AIC estimates the quality of statistical models relative to each other in terms of fitting the data (lower values indicate a better model fit). Results: After a median follow-up of 6.5 years, both the IPI and R-IPI were significantly associated with OS (Figure 1) and PFS; the IPI performed better than the R-IPI for OS and PFS in terms of discrimination and model fit (Table 1). All IPI factors were significantly associated with OS, and remained in MVA with the exception of disease stage. For patients aged ≤60 yrs, the IPI, R-IPI and aa-IPI were all strongly associated with OS and PFS; the IPI performed best overall of the 3 prognostic indices in terms of discrimination and model fit (Table 2). All individual IPI risk factors, excepting stage, were again found to be significantly associated with OS in MVA for patients aged ≤60 yrs. Conclusion: For the entire DLBCL cohort both the IPI and R-IPI identified meaningful prognostic groups for OS and PFS. Although the IPI outperformed the R-IPI, neither index identified a patient subgroup with an OS of Disclosures Cunningham: Roche pharmaceuticals: Research Funding. Hawkes:Bristol Myers Squibb: Other: Speaker fee, Research Funding; Merck KGA: Research Funding; Astra Zeneca: Research Funding; Merck Sharpe Dohme: Research Funding; Celgene: Other: Advisory board, Research Funding; Takeda: Other: Speaker fee; Merck: Other: Advisory board; Roche: Other: Speaker fee; advisory board. Pocock:Kent & Canterbury Hospital: Employment. Ardeshna:Celgene: Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Other: Conference expenses, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees. Radford:Celgene: Research Funding; Takeda: Consultancy, Research Funding, Speakers Bureau; ADC Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy, Speakers Bureau; GlaxoSmithKline: Equity Ownership; Novartis: Consultancy, Speakers Bureau; AstraZeneca: Equity Ownership; BMS: Consultancy, Speakers Bureau; Pfizer: Research Funding. McMillan:Celgene: Honoraria, Other: travel support; BMS: Honoraria; Amgen: Honoraria; Takeda: Other: travel support; Roche: Consultancy, Honoraria, Other: travel support; Pfizer: Research Funding; MSD: Honoraria. Johnson:Janssen: Consultancy, Research Funding; Epizyme: Consultancy, Honoraria, Research Funding; Boeringher Ingelheim: Consultancy; Kite: Consultancy; Incyte: Consultancy; Bristol-Myers Squibb: Honoraria; Takeda: Honoraria, Travel, accommodations, expenses; Novartis: Honoraria; Celgene: Honoraria; Eisai: Research Funding; Zenyaku Kogyo: Other: Travel, accommodations, expenses; Genmab: Consultancy.

Mutations in the isocitrate dehydrogenase gene (IDH1) were recently described in patients with acute myeloid leukemia (AML). To investigate their prognostic significance we determined IDH1 status in 1333 young adult patients, excluding acute promyelocytic leukemia, treated in the United Kingdom MRC AML10 and 12 trials. A mutation was detected in 107 patients (8%). Most IDH1+ patients (91%) had intermediate-risk cytogenetics. Mutations correlated significantly with an NPM1 mutation (P < .0001) but not a FLT3/ITD (P = .9). No difference in outcome between IDH1+ and IDH1− patients was found in univariate or multivariate analysis, or if the results were stratified by NPM1 mutation status. However, when stratified by FLT3/ITD status, an IDH1 mutation was an independent adverse factor for relapse in FLT3/ITD− patients (P = .008) and a favorable factor in FLT3/ITD+ patients (P = .02). These results suggest that metabolic changes induced by an IDH1 mutation may influence chemoresistance in a manner that is context-dependent.

We investigated the benefit of adding all-trans retinoic acid (ATRA) to chemotherapy for younger patients with nonacute promyelocytic acute myeloid leukemia and high-risk myelodysplastic syndrome, and considered interactions between treatment and molecular markers. Overall, 1075 patients less than 60 years of age were randomized to receive or not receive ATRA in addition to daunorubicin/Ara-C/thioguanine chemotherapy with Ara-C at standard or double standard dose. There were data on FLT3 internal tandem duplications and NPM1 mutations (n = 592), CEBPA mutations (n = 423), and MN1 expression (n = 195). The complete remission rate was 68% with complete remission with incomplete count recovery in an additional 16%; 8-year overall survival was 32%. There was no significant treatment effect for any outcome, with no significant interactions between treatment and demographics, or cytarabine randomization. Importantly, there were no interactions by FLT3/internal tandem duplications, NPM1, or CEBPA mutation. There was a suggestion that ATRA reduced relapse in patients with lower MN1 levels, but no significant effect on overall survival. Results were consistent when restricted to patients with normal karyotype. ATRA has no overall effect on treatment outcomes in this group of patients. The study did not identify any subgroup of patients likely to derive a significant survival benefit from the addition of ATRA to chemotherapy. This study is registered at http://www.controlled-trials.com under ISRCTN17833622.

An internal tandem duplication in the fms-like tyrosine kinase 3 gene (FLT3/ITD) is associated with poor prognosis in acute myeloid leukemia (AML), but the impact of mutant level, size, and interaction with nucleophosmin 1 (NPM1) mutations remains controversial. We evaluated these characteristics in a large cohort of young adult AML patients. There was a highly significant trend for worsening in relapse risk (RR) and overall survival (OS) with increasing FLT3/ITD mutant level (P < .001 for both), and even in the low level mutant group (1%-24% of total FLT3 alleles), RR was significantly worse than in the FLT3 wild-type (WT) group (P < .001). In multivariate analysis, mutant level was the most powerful prognostic factor for RR. Mutant size and number had no significant impact on outcome. The beneficial impact of an NPM1 mutation on RR and OS was seen in FLT3/ITD(+) as well as FLT3/WT patients; both markers were highly significant independent predictors of outcome (P < .001). Stratification using both markers identified 3 prognostic groups: good (FLT3/ITD(-)NPM1(+)), intermediate (FLT3/ITD(-)NPM1(-) or FLT3/ITD(+)NPM1(+)), and poor (FLT3/ITD(+)NPM1(-)). Patients with high FLT3/ITD mutant level (greater than 50%) or FLT3/ITD(+) in the absence of an NPM1 mutation may be good candidates for more experimental therapeutic approaches.

The prognostic impact of tyrosine kinase domain (TKD) mutations of the fms-like tyrosine kinase-3 (FLT3) gene in acute myeloid leukemia (AML) is currently uncertain. To resolve this issue we screened 1107 young adult nonacute promyelocytic leukemia AML patients with known FLT3 internal tandem duplication (ITD) status for FLT3/TKDs; they were detected in 127 (11%) cases. Mutations were associated with a high white cell count (P =.006) and patients with inv(16) (P = .005) but were infrequent in patients with adverse cytogenetics and secondary AML. Overall survival (OS) at 5 years was 53% and 37% for FLT3/TKD mutant and wild-type patients respectively (odds ratio, 0.72; 95% confidence interval, 0.58 to 0.89; P = .002). For both the cumulative incidence of relapse and OS the difference in outcome between FLT3/ITDs and FLT3/TKDs was highly significant (P < .001). In multivariate analysis, impact of FLT3/TKDs on OS when including all mutant-positive patients was not significant, but patients with high-level mutations (more than 25% mutant) had a significantly improved outcome (P = .004). The novel finding that biologically distinct activating mutations of the same gene can be associated with markedly different clinical outcomes has implications for risk stratification and therapy and is significant to the understanding of chemoresistance in AML.

The pathogenesis of acute myeloid leukemia (AML) involves the cooperation of mutations promoting proliferation/survival and those impairing differentiation. The RAS pathway has been implicated as a key component of the proliferative drive in AML. We have screened AML patients, predominantly younger than 60 years and treated within 2 clinical trials, for NRAS (n = 1106), KRAS (n = 739), and HRAS (n = 200) hot-spot mutations using denaturing high-performance liquid chromatography or restriction fragment length polymorphism (RFLP) analysis. NRAS mutations were confirmed in 11% of patients (126/1106) and KRAS mutations in 5% (39/739). No HRAS mutations were detected in 200 randomly selected samples. Codons most frequently mutated were N12 (43%), N13 (21%), and K12 (21%). KRAS mutations were relatively overrepresented in French-American-British (FAB) type M4 (P < .001). NRAS mutation was over-represented in the t(3;5)(q21 approximately 25;q31 approximately q35) subgroup (P < .001) and underrepresented in t(15;17)(q22;q21) (P < .001). KRAS mutation was overrepresented in inv(16)(p13q22) (P = .004). Twenty-three percent of KRAS mutations were within the inv(16) subgroup. RAS mutation and FLT3 ITD were rarely coexistent (14/768; P < .001). Median percentage of RAS mutant allele assayed by quantitative RFLP analysis was 28% (N12), 19% (N13), 25% (N61), and 21% (K12). RAS mutation did not influence clinical outcome (overall/disease-free survival, complete remission, relapse rate) either for the entire cohort or within cytogenetic risk groups.

We report the outcomes after reduced-intensity conditioning allogeneic stem cell transplantation (RIT) for non-Hodgkin lymphoma (NHL) in 88 patients (low-grade NHL [LG-NHL], n = 41; high-grade NHL [HG-NHL], n = 37; mantle cell lymphoma [MCL], n = 10). Thirty-seven patients had previously received autografts, and 21 were in complete remission (CR) at transplantation. Conditioning therapy consisted of alemtuzumab, fludarabine, and melphalan. Sixty-five patients received peripheral blood stem cells (PBSCs) from HLA-identical siblings, and 23 received bone marrow (BM) from matched unrelated donors. Prophylaxis for graft-versus-host disease (GVHD) consisted of cyclosporin A. Grade III-IV acute GVHD developed in 4 patients, and chronic GVHD developed in 6 patients. With a median follow-up of 36 months (range, 18-60 months), the actuarial overall survival (OS) rates at 3 years were 34% for HG-NHL, 60% for MCL, and 73% for LG-NHL (P < .001). The 100-day and 3-year transplant-related mortality (TRM) rates for patients with LG-NHL were 2% and 11%, respectively, and were better (P = .01) than they were for patients with HG-NHL (27% and 38%, respectively). The actuarial current progression-free survival (PFS) rate at 3 years, including the rate for patients who achieved remission after donor lymphocyte infusion (DLI) for progression, was 65% for LG-NHL, 50% for MCL, and 34% for HG-NHL (P = .002). Twenty-one patients underwent DLI for matched related donor (MD)-persistent disease or relapse, and 15 underwent DLI for mixed hematopoietic chimerism. Patients who experienced relapses of LG-NHL and chronic lymphocytic leukemia (CLL) achieved excellent PFS with extremely low TRM and GVHD, even when matched related donors were unavailable. (Blood. 2004;104:3865-3871)

Data on the application of donor lymphocyte infusions (DLIs) following reduced-intensity transplantation (RIT) remain limited. Persistence of host antigen-presenting cells might increase the efficacy or toxicity of cellular immunotherapies. We report the results of dose-escalating DLIs in 46 patients undergoing RIT, who received a total of 109 infusions to treat mixed chimerism or residual or progressive disease. Diagnoses were myeloma (n = 19), Hodgkin lymphoma (n = 13), non-Hodgkin lymphoma (n = 10), and other (n = 4). Thirty-two had an HLA-matched family donor and 14 an unrelated donor. Grades II to IV graft-versus-host disease (GVHD) occurred in 5 sibling and 7 unrelated donor recipients. GVHD was more common (P = .002), occurred at lower T-cell doses, and was more severe in the unrelated donor cohort. Conversion from mixed to multilineage full donor chimerism occurred in 30 of 35 evaluable patients. Presence of mixed chimerism in the granulocyte lineage at the time of DLI did not predict for chimerism response or GVHD. Disease responses occurred in 63% of patients with myeloma and 70% of those with Hodgkin lymphoma and were not predicted by changes in chimerism. These data support the presence of clinically relevant graft-versus-Hodgkin activity and indicate that DLI may be associated with a significantly increased toxicity in unrelated compared to sibling donor transplant recipients receiving identical treatment protocols.

Although nonmyeloablative conditioning regimen transplantations (NMTs) induce engraftment of allogeneic stem cells with a low spectrum of toxicity, graft-versus-host disease (GVHD) remains a significant cause of morbidity and mortality. In vivo T-cell depletion, using alemtuzumab, has been shown to reduce the incidence of GVHD. However, this type of maneuver, although reducing GVHD, may have an adverse impact on disease response, because NMTs exhibit their antitumor activity by relying on a graft-versus-malignancy effect. To explore the efficacy of alemtuzumab compared with methotrexate (MTX) for GVHD prophylaxis, we have compared the results in 129 recipients of a sibling NMT enrolled in 2 prospective studies for chronic lymphoproliferative disorders. Both NMTs were based on the same combination of fludarabine and melphalan, but the United Kingdom regimen (group A) used cyclosporin A plus alemtuzumab, whereas the Spanish regimen (group B) used cyclosporin A plus MTX for GVHD prophylaxis. Patients receiving alemtuzumab had a higher incidence of cytomegalovirus (CMV) reactivation (85% versus 24%,P

FLT3 mutations, either internal tandem duplications (ITDs) or aspartate residue 835 (D835) point mutations, are present in approximately one third of patients with acute myeloid leukemia (AML) and have been associated with an increased relapse rate. We have studied FLT3 mutations in paired presentation and relapse samples to ascertain the biology of these mutations and to evaluate whether they can be used as markers of minimal residual disease. At diagnosis, 24 patients were wild-type FLT3, and 4 acquired a FLT3 mutation at relapse (2 D835+, 2 ITD+), with a further patient acquiring an ITD at second relapse. Of 20 patients positive at diagnosis (18 ITD+, 2 D835+), 5 who were all originally ITD+ had no detectable mutation at relapse, as determined by a sensitive radioactive polymerase chain reaction. One of these patients had acquired an N-Ras mutation not detectable at presentation. Furthermore, another patient had a completely different ITD at relapse, which could not be detected in the presentation sample. These results indicate that FLT3 mutations are secondary events in leukemogenesis, are unstable, and thus should be used cautiously for the detection of minimal residual disease.

A nonmyeloablative conditioning regimen was investigated in 47 patients with hematological malignancy receiving allogeneic progenitor cells from matched, unrelated donors. The median patient age was 44 years. The majority of patients had high-risk features, including having failed a prior transplantation (29 individuals). Twenty of the transplants were mismatched for HLA class I and/or class II alleles. Recipient conditioning consisted of 20 mg CAMPATH-1H on days −8 to −4, 30 mg/m2fludarabine on days −7 to −3, and 140 mg/m2 melphalan on day −2. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporine A alone. Primary graft failure occurred in only 2 of 44 evaluable patients (4.5%). Chimerism studies in 34 patients indicated that the majority (85.3%) attained initial full donor chimerism. Only 3 patients developed grade III to IV acute GVHD, and no patients have yet developed chronic extensive GVHD. The estimated probability of nonrelapse mortality at day 100 was 14.9% (95% confidence interval [CI], 4.7%-25.1%). With a median follow-up of 344 days (range, 79-830), overall and progression-free survivals at 1 year were 75.5% (95% CI, 62.8%-88.2%) and 61.5% (95% CI, 46.1%-76.8%), respectively. In summary, a nonmyeloablative regimen incorporating in vivo CAMPATH-1H is effective in promoting durable engraftment in most patients and in reducing the risk of severe GVHD following matched unrelated donor transplantation.

Calreticulin mutations (CALR(MUT)) are found in a significant proportion of patients with essential thrombocythemia (ET) lacking JAK2(V617F) or MPL mutations. They are associated with substantially different hematological and clinical features and define a distinct subtype of ET. We show here that their presence is significantly correlated with a clonal X chromosome inactivation pattern (XCIP). Of 105 female ET patients investigated, 61 had an interpretable XCIP, and a clonal pattern was observed in 88% of CALR(MUT) patients compared with 26% of JAK2(V617F) (P = .0002) and 9% of JAK2(V617F)/MPL/CALR wild-type patients (P.0001). Neutrophil CALR(MUT) level was significantly higher than JAK2(V617F) level (median, 50% vs 18%; P.0001), and wild-type myelopoiesis was suppressed in CALR(MUT) but not JAK2(V617F) patients. These data are suggestive of truly monoclonal hematopoiesis in CALR(MUT) patients and provide further evidence that the biology associated with CALR mutations is markedly different from that of JAK2(V617F) mutations.

Severe congenital neutropenia (SCN) was originally described as an autosomal recessive disorder. Subsequently, autosomal dominant and sporadic forms of the disease have been recognized. All forms are manifest by persistent severe neutropenia and recurrent bacterial infection. In contrast, cyclical hematopoiesis is characterized by periodic neutropenia inter-spaced with (near) normal neutrophil counts. Recently, linkage analysis on 13 affected pedigrees identified chromosome 19p13.3 as the likely position for mutations in cyclical hematopoiesis. Heterozygous mutations in the ELA2 gene encoding neutrophil elastase were detected in all families studied. Further work also demonstrated mutations in ELA2 in sporadic and autosomal dominant SCN. However, all mutations described to date are heterozygous and thus appear to act in a dominant fashion, which is inconsistent with an autosomal recessive disease. Therefore, the current study investigated whether mutations in ELA2could account for the disease phenotype in classical autosomal recessive SCN and in the sporadic and autosomal dominant types. All 5 exons of ELA2 and their flanking introns were studied in 18 patients (3 autosomal recessive, 5 autosomal dominant [from 3 kindreds], and 10 sporadic) using direct automated sequencing. No mutations were found in the autosomal recessive families. A point mutation was identified in 1 of 3 autosomal dominant families, and a base substitution was identified in 8 of 10 patients with the sporadic form, though 1 was subsequently shown to be a low-frequency polymorphism. These results suggest that mutations in ELA2are not responsible for classical autosomal recessive Kostmann syndrome but provide further evidence for the role of ELA2 in SCN.

The prevention of apoptosis is a key function of growth factors in the regulation of erythropoiesis. This study examined the role of the constitutively active serine/threonine kinase glycogen synthase kinase-3 (GSK3), a target of the phosphoinositide-3-kinase (PI3K)/Akt pathway, in the regulation of apoptosis in primary human erythroid progenitors. GSK3 phosphorylation at its key regulatory residues S21 (α isoform) and S9 (β isoform) was high in steady-state culture, disappeared on growth factor withdrawal, and returned in response to treatment of cells with either erythropoietin or stem cell factor. Phosphorylation correlated with a PI3K-dependent reduction of 25% to 30% in measured GSK3 activity. LY294002, a specific inhibitor of PI3K, induced apoptosis in growth factor–replete erythroid cells to a degree similar to growth factor deprivation, whereas the Mek1 inhibitor U0126 had no effect, implicating PI3K and not mitogen-activated protein kinase in survival signaling. Growth factor–deprived erythroblasts, which undergo apoptosis rapidly, were protected from apoptosis by both lithium chloride, a GSK3 selective inhibitor, and inhibition of caspase activity. However, the clonogenic potential of single cells, which more accurately reflects cell survival, was maintained by lithium chloride, but not by caspase inhibition. Furthermore, lithium chloride, but not caspase inhibition, prevented the appearance of the conformational form of Bax associated with apoptosis induction. In summary, GSK3 activity is suppressed by erythropoietin and stem cell factor in human erythroid progenitor cells, and increased GSK3 activity, brought about by growth factor withdrawal, may regulate commitment to cell death through a caspase-independent pathway that results in a conformational change in Bax.

Arachidonic acid (AA) generated by phospholipase A(2) (PLA(2)) is thought to be an essential cofactor for phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Both enzymes are simultaneously primed by cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha). The possibility that either unprimed or cytokine-primed responses of PLA(2) or NADPH oxidase to the chemotactic agents formyl-methionyl-leucyl-phenylalanine (FMLP) and complement factor 5a (C5a) could be differentially inhibited by inhibitors of the mitogen-activated protein (MAP) kinase family members p42(ERK2) (PD98059) and p38(SAPK) (SB203580) was investigated. PD98059 inhibited the activation of p42(ERK2) by GM-CSF, TNF-alpha, and FMLP, but it did not inhibit FMLP-stimulated superoxide production in either unprimed or primed neutrophils. There was no significant arachidonate release from unprimed neutrophils stimulated by FMLP, and arachidonate release stimulated by calcium ionophore A23187 was not inhibited by PD98059. In contrast, PD98059 inhibited both TNF-alpha- and GM-CSF-primed PLA(2) responses stimulated by FMLP. On the other hand, SB203580 inhibited FMLP-superoxide responses in unprimed as well as TNF-alpha- and GM-CSF-primed neutrophils, but failed to inhibit TNF-alpha- and GM-CSF-primed PLA(2) responses stimulated by FMLP, and additionally enhanced A23187-stimulated arachidonate release, showing that priming and activation of PLA(2) and NADPH oxidase are differentially dependent on both the p38(SAPK) and p42(ERK2) pathways. Studies using C5a as an agonist gave similar results and confirmed the findings with FMLP. In addition, methyl arachidonyl fluorophosphonate (MAFP), the dual inhibitor of c and iPLA(2) enzymes, failed to inhibit superoxide production in primed cells at concentrations that inhibited arachidonate release. These data demonstrate that NADPH oxidase activity can be dissociated from AA generation and indicate a more complex role for arachidonate in neutrophil superoxide production.

The activation of phospholipase A2 (PLA2) with release of eicosanoids and prostanoids in mature myeloid cells and the augmentation (priming) of this activity by cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) are central to the inflammatory process. Yet, there are few data concerning PLA2 activity and its regulation by growth factors in primary hematopoietic cells. We therefore analyzed the PLA2activity of mobilized human CD34 antigen-positive (CD34+) stem cells by quantitation of the extracellular release of3H-arachidonate. The PLA2 activity of CD34+ cells stimulated with calcium ionophore (A23187) was of similar magnitude to that of mature neutrophils and monocytes. Preincubation of CD34+ cells with stem cell factor (SCF) before A23187-stimulation resulted in primed PLA2 activity, whereas interleukin-3 (IL-3), GM-CSF, and tumor necrosis factor  had no significant effect. When CD34+ cells were induced to differentiate, PLA2 activity remained responsive to SCF for several days, but after 8 days, at which stage morphological and functional evidence of maturation was occurring, priming of PLA2 by SCF could no longer be elicited, whereas responses to GM-CSF and IL-3 had developed. The further metabolism of arachidonic acid to eicosanoids by CD34+ cells was not detected by either thin-layer chromatography, enzyme immunoassay, or differential spectroscopy. SCF stimulated the rapid but transient activation of ERK2 (p42 MAP kinase) in CD34+ cells, and we used the MAP kinase kinase inhibitor, PD 098059, which at 30 μmol/L blocks ERK2 activation in CD34+ cells, to investigate whether SCF-mediated priming of arachidonate release was mediated by this kinase. PD 098059 only partially inhibited A23187-stimulated PLA2 activity primed by SCF, suggesting the involvement of ERK2 and possibly a further signal transduction pathway. Methyl arachidonyl fluorophosphonate (5 μmol/L), a dual inhibitor of i and cPLA2 isoforms, completely inhibited arachidonate release without affecting ERK2 activation, demonstrating the lack of cellular toxicity. These data provide the first evidence that primitive myeloid cells have the capacity to release arachidonate, which is regulated by an early acting hematopoietic growth factor important for the growth and survival of these cells.

Essential thrombocythemia (ET) is traditionally considered to be a clonal disorder. No specific karyotypic abnormalities have been described, but the demonstration of clonality using X-chromosome inactivation patterns (XCIPs) has been used to differentiate ET from a non-clonal reactive thrombocytosis. However, these assays may be difficult to interpret, and contradictory results have been reported. We have studied 46 females with a diagnosis of ET according to the Polycythemia Vera Study Group (PVSG) criteria. XCIP results in 23 patients (50%) were uninterpretable due to either constitutive or possible acquired age-related skewing. Monoclonal myelopoiesis could be definitively shown in only 10 patients. Thirteen patients had polyclonal myelopoiesis, and in 8, it was possible to exclude clonal restriction to the megakaryocytic lineage. Furthermore, there was no evidence of clonal progenitors in purified CD34+CD33− and CD34+CD33+ subpopulations from bone marrow of 2 of these 13 patients. There was no difference between patients with monoclonal and polyclonal myelopoiesis with respect to age or platelet count at diagnosis, duration of follow-up, incidence of hepatosplenomegaly, or hemorrhagic complications. However, polyclonal patients were less likely to have experienced thrombotic events (P = .039). These results suggest that ET is a heterogeneous disorder, and the clinical significance of clonality status warrants investigation in a larger study.

Intermittent painful crises due to vasoocclusion are the major clinical manifestation of sickle cell disease (SCD), but subclinical episodes may also occur. There is sparse evidence for the involvement of neutrophils in the pathophysiology of SCD, but production of cytokines by the damaged endothelium might influence neutrophil function and modulate responses to subsequent cytokine exposure. In addition, the activation of neutrophils in the microcirculation could itself exacerbate vasoocclusion. To test whether neutrophil inflammatory responses were altered in SCD, neutrophil phospholipase A2 and NADPH oxidase activity in response to in vitro priming by granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-α (TNF-α) were measured both during and between painful crises. Resting levels of neutrophil phospholipase A2 activity in steady-state SCD (4.0% ± 0.5% of total cell radioactivity) were raised relative to control values (2.0% ± 0.2%, n = 10, P = .008). There was no defect of agonist-stimulated phospholipase A2 or NADPH oxidase activity in steady-state SCD; however, the ability of phospholipase A2 to respond to priming with GM-CSF was attenuated to 63% ± 17% of control values (n = 10,P = .04). Similarly, neutrophil NADPH oxidase activity after priming with GM-CSF and TNF-α was, respectively, 65% ± 11% (n = 7, P = .03) and 57% ± 7% of control (n = 10, P = .007) in steady-state disease, and was further reduced during painful vasoocclusive crises to 34% ± 9% and 25% ± 3% of control for GM-CSF and TNF-α, respectively. These data were not explained by poor splenic function or any racial factor, as normal cytokine responses were seen in splenectomized patients in remission from Hodgkin's disease and in healthy Afro-Caribbean subjects. Abnormal neutrophil cytokine priming responses were not observed in either patients with rheumatoid arthritis or iron-deficiency anemia. Our findings are indicative of an ongoing inflammatory state in SCD between painful crises involving neutrophil activation and an abnormality of cytokine-regulated neutrophil function, which may compromise the host defenses against certain microorganisms.

The transmigration of hematopoietic progenitor cells (HPCs) across vascular endothelium is a critical step in the homing of transplanted stem cells, but the molecular basis for this is unknown. We used mobilized peripheral blood CD34+ selected cells and cultured bone marrow microvascular (BMECs) and human umbilical vein endothelial cells (HUVECs) to investigate the adhesion and transendothelial migration of HPCs. Colony-forming cells (CFCs) in freshly isolated CD34+ cells showed high levels of adhesion to both forms of endothelium (28% ± 4% and 38% ± 6% of granulocyte-macrophage colony-forming cells [GM-CFCs] adhering to HUVECs and BMECs, respectively), but were unable to migrate to any significant extent across either (1.0% ± 0.3% and 1.1% ± 0.6% of GM-CFCs migrating across HUVECs and BMECs, respectively). Greater than 95% of peripheral blood CD34+ cells are in G0/G1 of the cell cycle, but after 48 to 72 hours of stimulation with growth factors (interleukin-3 [IL-3] 12 ng/mL, stem cell factor 10 ng/mL, and IL-6 10 ng/mL), 28% ± 5% of cells were in S+G2/M. Growth factor stimulation had no effect on the adhesion of mobilized CFCs but resulted in enhanced migration of these cells (9.8% ± 1.6% and 12.6% ± 3.1% of GM-CFCs migrating across HUVECs and BMECs, respectively; P < .01, n = 6). Assessment of cell proliferation by the3H-thymidine suicide method showed that, whereas 11.7% ± 3.3% of proliferating CFCs transmigrated across endothelium, only 1.3% ± 0.3% of nonproliferating CFCs did so (P < .05, n = 5). Transmigration of growth factor-activated CFCs was inhibited by anti-CD18 monoclonal antibody (MoAb; 50% ± 18% inhibition) and by anti–platelet endothelial cell adhesion molecule-1 (PECAM-1) MoAb (70.8% ± 7.1% inhibition; P < .05, n = 3). IL-1 stimulation of HUVECs had no significant effect on CD34+cell transmigration, but caused marked enhancement of neutrophil migration. Stem cell homing may depend, in part, on the ability of local cytokines to upregulate the transmigratory ability of these cells. The transmigration of HPCs shares at least some molecular pathways with that of mature cells (CD18 and PECAM-1), but is differently affected by endothelial activation.

We report here a naturally occurring isoform of the human β chain common to the receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 (GMRβC) with a truncated intracytoplasmic tail caused by deletion of a 104-bp exon in the membrane-proximal region of the chain. This β intracytoplasmic truncated chain (βIT) has a predicted tail of 46 amino acids, instead of 432 for βC, with 23 amino acids in common with βC and then a new sequence of 23 amino acids. In primary myeloid cells, βIT comprised approximately 20% of the total β chain message, but was increased up to 90% of total in blast cells from a significant proportion of patients with acute leukemia. Specific anti-βITantibodies demonstrated its presence in primary myeloid cells and cell lines. Coexpression of βIT converted low-affinity GMRα chains (KD 2.5 nmol/L) to higher-affinity αβ complexes (KD 200 pmol/L). These could bind JAK2 that was tyrosine-phosphorylated by stimulation with GM-CSF. βITdid not support GM-CSF–induced proliferation when cotransfected with GMRα into CTLL-2 cells. Therefore, it may interfere with the signal-transducing properties of the βC chain and play a role in the pathogenesis of leukemia.

Mobilized peripheral blood progenitors (CD34+ cells) have been shown to be either in the G0 or G1 phase of the cell cycle. In this study, it is shown that they are small cells with low protein content suggestive of G0. Support for this is provided by showing that the principal E2F complex consists of hypophosphorylated p130, E2F-4, and DP-1. The E2F-4 is more highly phosphorylated than in quiescent T cells. In response to cytokines in vitro, the CD34+ cells start to enter G1 within 8 hours and enter S-phase at about 48 hours. As cells enter G1, E2F-4 is dephosphorylated to several hypophosphorylated forms and three new DNA-binding complexes appear, including one containing E2F-4, DP-1, and p107. We suggest that mobilized CD34+ cells may be maintained in G0 by p130, E2F-4, and DP-1 and the coordinate dephosphorylation of E2F-4 and hyperphosphorylation of p130 may be central to the initiation of proliferation.

The Bcl-2 protein is capable of preventing apoptosis, and in vitro evidence suggests a role in drug resistance. It is expressed and the gene is rearranged in a proportion of cases of large-cell non-Hodgkin's lymphoma (NHL), but the clinical significance of these findings is controversial. The purpose of this study was to determine the influence of both Bcl-2 expression and major breakpoint region (MBR) bcl-2 rearrangement in a large cohort of prospectively accrued patients with intermediate-grade B-cell NHL treated in a standardized manner. All patients with Working Formulation F, G, or H NHL treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy in British National Lymphoma investigation studies between July 1974 and April 1992 were considered for this study if the appropriate paraffin blocks were available. Paraffin sections from the diagnostic specimen were analyzed for evidence of MBR rearrangement using a polymerase chain reaction-based method, and for Bcl-2 expression using immunohistochemistry. Failure to achieve complete remission (CR), relapse, death from NHL, and deaths from all causes were used as end points to measure CR rate, actuarial relapse rate, actuarial survival from NHL, and actuarial overall survival. One hundred sixty-one suitable patients were identified and tested for the bcl-2 MBR translocation, with 27 (17%) found to be positive; 153 of these patients were tested with immunocytochemistry, and 84 (55%) showed evidence of Bcl-2 expression. For patients who achieved CR from the initial treatment, the relapse rate was significantly higher in those with Bcl-2 expression than in those without. In addition, multivariate analysis identified Bcl-2 expression as the only factor significantly related to relapse rate in the subjects measured. The cause-specific survival for NHL in the series as a whole was significantly lower in patients with Bcl-2 expression than in those without. MBR status had no significant influence on any of the outcome measures, but the number of MBR-positive patients was relatively small, and larger studies are required. In conclusion, in Working Formulation F, G, and H NHL of B-cell type, expression of Bcl-2 protein predicted independently for relapse.

Introduction: Central nervous system (CNS) relapse of diffuse large B-cell lymphoma (DLBCL) represents a major clinical challenge and is fatal in most patients. Recently Schmitz et al (J ClinOncol 2016), defined an effective risk model, the CNS-IPI, to identify those at highest risk of CNS relapse, based on the international prognostic index (IPI) score and presence of renal or adrenal involvement. For DLBCL patients receiving R-CHOP-like regimens +/- intrathecal methotrexate, the risk of CNS relapse for low, intermediate and high-risk patients was Aim: To assess CNS relapse rates in an intermediate-high risk cohort of patients with DLBCL treated with the R-CODOX-M R-IVAC regimen, incorporating multiple CNS-penetrating agents. Methods: Patients with newly diagnosed DLBCL and an IPI score ≥3 were enrolled in a prospective, multi-centre, phase 2 trial (McMillan et al, Hematol Oncol 2015; 31(S1), 130a) and treated with modified CODOX-M and IVAC, including high dose intravenous methotrexate, cytarabine, ifosfamide and etoposide with 8-12 intrathecal injections (Mead et al, AnnOncol 2002; 23(8):1264-74); plus 8 doses of rituximab. The primary endpoint was progression-free survival (PFS). CNS involvement was diagnosed according to neurological signs, radiological findings and/or demonstration of malignant lymphocytes within the cerebrospinal fluid. Involvement ofextranodal sites was prospectively documented at registration and at relapse. Presence of CNS, adrenal and renal involvement was confirmed using case report forms prior to this post hoc analysis. Results: 108 patients were treated at 32 UK sites between May 2008 and April 2013. Median age was 50 years (18-65 years). Eight patients (7.4%) had CNS involvement at baseline. Eighty-two patients (75.9%) received 4 cycles of treatment. At a median follow-up of 45 months, PFS and overall survival were 65.5% (95% CI: 55.5 - 73.8) and 73.7% (64.0 - 81.2), respectively. Progression or relapse within the CNS occurred in 5 patients (4.6%; Table 1) at a median of 5.5 months after registration (0.9-9.1 months). All patients died within 9 months of CNS relapse, 4 due to DLBCL and one treatment-related death. Excluding those with CNS involvement at baseline or incomplete information (n=4; 2 with missing baseline information (no CNS relapse) and 2 awaiting confirmation of CNS status at relapse), CNS-IPI was evaluable in 96 patients, of which 95% had an elevated LDH, 57% had a performance status of ≥2, and 8% were ≥60 years. All patients had stage III-IV disease, 76% had >1 extranodalsite and 27% had renal or adrenal involvement. Forty-one patients (43%) were intermediate risk (2-3 factors) and 55 (57%) were high risk (4-6 factors) for CNS relapse. 2-year CNS relapse rates were 0% for intermediate risk and 6.2% (2.0 - 18.1) for high risk patients (Figure 1). Of the 3 CNS relapses in high risk patients, 2 occurred concurrently with systemic relapse; there was only one episode of isolated CNS relapse. Of the 8 patients with CNS involvement at baseline, 2 (25%) developed CNS relapse, including 1 isolated CNS relapse. One further patient died of refractory DLBCL whilst 5 (62.5%) are alive and progression free with a minimum of 28 months follow-up. Conclusions: Inclusion of CNS-directed therapy intrinsic to the R-CODOX-M IVAC regimen resulted in very low rates of CNS relapse. Although patient numbers and low event rates make direct comparison difficult, results appear promising alongside historical results with R-CHOP chemotherapy. CNS relapse rates for both intermediate and high risk patients in this trial were below the 95% confidence intervals for CNS relapse reported in large training and validation cohorts by Schmitz et al (0% vs 2.2 - 4.4 and 2.3 - 5.5 for intermediate risk patients and 6.2% vs 6.3 - 14.1 and 7.9 - 16.1 for high risk). Of note, only 2 patients in the whole cohort progressed with isolated CNS disease, one of whom had CNS disease at diagnosis. Thus, where systemic disease was fully treated, treatment failure due to inadequate CNS penetration was rare. Reasonable outcomes were achieved in patients with CNS involvement at diagnosis but greater patient numbers are required to further evaluate this regimen in secondary CNS lymphoma. Table 1 PFS events and CNS relapse rates Table 1. PFS events and CNS relapse rates Figure 1 CNS relapse rates according to CNS-IPI and presence of CNS disease at baseline Figure 1. CNS relapse rates according to CNS-IPI and presence of CNS disease at baseline Disclosures Phillips: Roche: Consultancy. Patmore:Roche: Honoraria; Janssen Cilag: Honoraria. Ardeshna:Roche: Membership on an entity's Board of Directors or advisory committees, Other: Conference Expenses, Research Funding. Montoto:Roche: Honoraria; Gilead: Research Funding.

Introduction: The discovery of 3 distinct molecular subgroups of diffuse large B-cell lymphoma (DLBCL) according to cell-of-origin (COO): germinal centre B-cell (GCB), activated B-cell (ABC) and type III/unclassifiable by gene expression profiling (GEP) (Alizadeh et al, Nature 2000; Rosenwald et al, NEJM 2002) was a key advance in understanding the disease biology. The ABC subtype is associated with inferior survival which has persisted in the rituximab era (Lenz et al, NEJM 2008). Determination of COO by GEP has not been incorporated into routine practice however due to a lack of accessibility and requirement for fresh frozen tissue. Barrans et al (BJH 2012) recently demonstrated that COO could be accurately classified by the Illumina DASL® platform, using RNA extracted from routinely processed FFPE tissue from a population-based cohort of 172 R-CHOP-treated patients, and predicted clinical outcome. The aim of this analysis was to determine GEP-based DLBCL COO using the Illumina DASL® platform, to correlate results with outcome, and to validate this methodology using FFPE tissue samples from patients enrolled in the prospective phase III R-CHOP 14 v 21 trial. Methods: The UK NCRI R-CHOP-14 v 21 trial assessed R-CHOP given 2-weekly versus 3-weekly in 1080 previously untreated DLBCL patients aged ≥18 years and enrolled from 2005-2008. We previously reported that R-CHOP-14 was not superior to R-CHOP-21 for overall survival (OS), progression-free survival (PFS), response rate or safety. COO as determined by the Hans classifier (n=560) was not prognostic for OS (Cunningham et al, Lancet 2013). All patients with sufficient FFPE material remaining were included in this analysis. RNA was extracted and GEP was performed using the Illumina DASL® platform. Cases were classified as ABC, GCB or type III according to the DAC classifier (Care et al, Plos One 2013). Response was assessed using IWG 1999 criteria. PFS and OS were calculated from date of randomisation and analysed using Kaplan-Meier and Cox regression methods. Results: 369 patients had sufficient FFPE material remaining for analysis. COO classification was as follows: ABC 15.2% (n=56), GCB 46.3% (n=171), type III 38.5% (n=142). Baseline characteristics are shown in Table 1. Patients with GCB subtype had a significantly higher incidence of BCL-2 (p1 extranodal site of disease, elevated LDH), sex, bulky disease, B symptoms and trial arm; patients classified as GCB or type III had superior OS versus ABC subtype (HR 0.53, 95% CI: 0.31-0.89; p=0.02) and (HR 0.56, 95% CI: 0.33-0.96; p=0.03) respectively. GCB subtype was also independently associated with superior PFS versus ABC subtype (HR=0.59, 95% CI: 0.37-0.96; p=0.03). The difference in PFS between type III and ABC subtypes did not reach statistical significance, but followed a similar trend (HR=0.65, 95% CI: 0.40-1.07; p=0.09). Results of univariate and multivariate analyses of individual factors and OS are shown in Table 2. Conclusion: Our results demonstrate that the ABC subtype of DLBCL as determined by GEP is independently associated with inferior PFS and OS. Our findings confirm those of Barrans et al (BJH 2012) and serve as a validation cohort for this methodology in the setting of a prospective trial where patients were exclusively R-CHOP-treated. Of note our patient cohort included a high proportion of type III/unclassifiable patients (38.5%) which are being further investigated currently and updated results will be presented at the meeting. Our analysis confirms that GEP-based COO is a significant prognostic biomarker for DLBCL in the rituximab era which can be accurately determined using routinely processed FFPE tissue samples. Table 1 Baseline characteristics Table 1. Baseline characteristics Figure 1. Overall survival by cell-of-origin determined by gene expression profiling group Figure 1. Overall survival by cell-of-origin determined by gene expression profiling group Table 2 Overall survival: univariate and multivariate analyses Table 2. Overall survival: univariate and multivariate analyses Disclosures Cunningham: Medimmune: Research Funding; Merrimack: Research Funding; Celgene: Research Funding; Bayer: Research Funding; Astra-Zeneca: Research Funding; Amgen: Research Funding. Hawkes:Merck Serono: Research Funding; Takeda: Other: travel expenses; BMS: Other: travel expenses, Research Funding. Pocock:Gilead Sciences: Other: Sponsorship to attend the EHA 2016 Meeting; Janssen: Speakers Bureau; Takeda: Honoraria. Ardeshna:Roche: Membership on an entity's Board of Directors or advisory committees, Other: Conference Expenses, Research Funding. Radford:Astra Zeneca: Equity Ownership; GlaxoSmithKline: Equity Ownership; Novartis: Honoraria; Seattle Genetics: Honoraria; Takeda: Honoraria, Research Funding.

Background: Epigenetic alterations are a hallmark of diffuse large B cell lymphoma (DLBCL). A high degree of methylation disruption and intra-tumor methylation heterogeneity have been linked to poor outcome in DLBCL. However, high-coverage methylation data within prospective trial cohorts are warranted to characterize clinically relevant methylation subgroups of DLBCL. Here, we investigate the methylome of DLBCL cases from a large multicentre Phase III trial and its interaction with clinical and molecular characteristics. Methods: DNA methylation was assessed with the Illumina Infinium 450k array in archived FFPE samples of 127 newly diagnosed DLBCL patients treated with R-CHOP chemotherapy on the UK NCRI R-CHOP14v21 trial. Status of BCL2-, BCL6-, and MYC-rearrangements and amplifications was available for 111 cases. Cell-of-origin classification was available for all cases, both according to the IHC Hans algorithm and the microarray-based classification tool using Illumina DASL technology (Barrans, Br J Haematol 2012). In addition, microarray data was used to extract mean expression values of the epigenetic modifiers EZH2, MLL2, CREBBP, EP300, DNMT3A, IDH1/2 and TET2 and patients in the lowest and highest expression quartiles were compared. Analyses were performed in R 3.2.3 using the RnBeads package. Differential methylation was analyzed on region level (tiling, genes, promoters, CpG islands). P values were adjusted for multiple testing using the false discovery rate method. Results: After normalization and quality control 425,623 probes were included in the analysis. Median methylation levels of probes showed a bimodal distribution (unmethylated/methylated) across samples, with CpG islands and shores being mainly unmethylated, and CpG shelves and open seas being predominantly methylated. No significant association of clinical prognostic factors (age, LDH level, extranodal involvement, stage, WHO performance status) and methylation could be observed. We did not find significant differential methylation between patients who relapsed after R-CHOP therapy and those who did not. However, more detailed outcome analyses using Cox regression models for progression- and overall survival on single-site level will be provided at the meeting. There was no evidence for a difference in methylation with regards to rearrangements or amplifications of MYC or BCL6, nor with presence of double-hit abnormalities. Interestingly, cases with BCL2 rearrangement showed differential methylation of 39 promoter regions compared to cases without this abnormality (all adj. P Conclusions: The cell-of-origin as well as expression levels of DNMT3A are main drivers of methylation variability in DLBCL, whereas other molecular features like MYC seem to have little impact on methylation patterns. This comprehensive dataset of genome-wide methylation profiles from a prospective trial cohort provides important information for identifying biologically and clinically relevant epigenetic subgroups of DLBCL. Disclosures Cunningham: Amgen: Research Funding; Astra-Zeneca: Research Funding; Bayer: Research Funding; Celgene: Research Funding; Merrimack: Research Funding; Medimmune: Research Funding.

LMO2is a crucial regulator of normal hematopoiesis but is progressively silenced from the early T-cell progenitor stage of thymic development. Aberrant LMO2 expression leads to a block in differentiation, increased self-renewal and aggressive T-cell acute lymphoblastic leukemia (T-ALL). Although ≈50% of T-ALL patients overexpress LMO2, this can be attributed to a cytogenetic lesion in only ≈10% of patients, leaving a significant portion mechanistically unaccounted for. We recently discovered somatic mutations that create an oncogenic super-enhancer driving TAL1 expression (Mansour et al., 2014, Science). Therefore, we investigated whether comparable mutations may be causing dysregulated LMO2 expression. Aberrant H3K27ac marks indicative of active chromatin were identified prior to and encompassing the non-coding exon 2 of the LMO2 gene by ChIP-seq in DU.528 and PF-382 T-ALL cell lines, both of which exhibit upregulated LMO2 expression but lack chromosomal lesions at this locus. Sequencing across this peak revealed a heterozygous 20bp duplication in PF-382 cells and a heterozygous 1bp deletion in DU.528 cells, located close to a region recently described as an intermediate promoter. Both indels generated a de novo MYB consensus motif. MYB ChIP-seq showed that ≥96% of reads aligned to the mutant rather than the wild-type allele, suggesting that MYB was preferentially recruited to the mutant allele. Heterozygous mutations were also detected in diagnostic samples from 3% (5/159) of pediatric and 6% (10/164) of adult T-ALL patients. Absence of the mutations in 7 available patient-matched remission samples confirmed that they were somatic. The mutations were densely distributed around highly conserved native ETS1, MYB and GATA motifs; 5 patients had an additional MYB site, 3 both a MYB and an ETS1 site, 1 an ETS1 site alone, and 4 had new RUNX1 binding sites. This suggests that this region may have a regulatory role that is exploited by the mutations to constitutively activate LMO2. All 6 mutant-positive patients with available RNA showed LMO2 overexpression as determined by qRT-PCR, consistent with the hypothesis that these mutations activate gene expression. Furthermore, monoallelic LMO2 expression could be demonstrated in DU.528 cells and 3 of 4 informative T-ALL samples using a heterozygous germline SNP. Expression of the mutations in luciferase reporter assays also indicated that they all markedly activated luciferase activity to between 2x and 57x compared to the wild-type sequence. To assess causality between the mutations and LMO2 dysregulation, we used CRISPR/Cas9 genome-editing with a guide RNA designed to target the mutant MYB site in PF-382 cells. Reduction of LMO2 expression to ≤10% of PF-382 mutant activity was observed in a clone where the mutant allele had been reverted to wild-type and in another clone with a single T>C substitution disrupting the mutant MYB binding site. Interestingly, 2 clones that increased the distance between the native and the mutant MYB sites also resulted in a reduction in LMO2 expression to 19% and 25% of PF-382 activity, suggesting that there are functionally limiting spatial constraints on the mutant MYB site in relation to other neighboring transcription factor binding sites. This was further validated by the lack of reduction in LMO2 expression in a clone where the sequence between the two MYB sites was altered but the spacing distance was unchanged. In conclusion, we have identified and functionally validated a novel recurrent mutation hotspot occurring in a non-coding site whereby introduction of additional binding sites for a number of different transcription factors drives monoallelic LMO2 overexpression from a neomorphic promoter in a substantial proportion of both adult and pediatric T-ALL patients. This mechanism of oncogene activation may be relevant to a wide variety of human cancers. Disclosures Fielding: Baxalta: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

T-cell lymphomas and leukemias are aggressive, treatment-resistant cancers with poor prognosis. Immunotherapeutic approaches have been limited by a lack of target antigens discriminating malignant from healthy T-cells. While treatment of B-cell cancers has been enhanced by targeting pan B-cell antigens, an equivalent approach is not possible for T-cell malignancies since profound T-cell depletion, unlike B-cell depletion, would be prohibitively toxic. We propose an immunotherapeutic strategy for targeting a pan T-cell antigen without causing severe depletion of normal T-cells. The α/β T-cell receptor (TCR) is a pan T-cell antigen, expressed on >90% of T-cell lymphomas and all normal T-cells. An overlooked feature of the TCR is that the β-constant region comprises 2 functionally identical genes: TRBC1 and TRBC2. Each T-cell expresses only one of these. Hence, normal T-cells will be a mixture of individual cells expressing either TRBC1 or 2, while a clonal T-cell cancer will express TRBC1 or 2 in its entirety. Despite almost identical amino acid sequences, we identified an antibody with unique TRBC1 specificity. Flow cytometry (FACS) of T-cells in normal donors (n = 27) and patients with T-cell cancers (n = 18) revealed all subjects had TRBC1 and 2 cells in both CD4 and CD8 compartments, with median TRBC1 expression of 35% (range 25-47%). In addition, we examined viral-specific T-cells in healthy volunteers, by generation of Epstein Barr virus-specific primary cytotoxic T-cell lines (3 donors) or by identification of cytomegalovirus-specific (3 donors) or adenovirus-specific (5 donors) T-cells by peptide stimulation. We demonstrated similar TRBC1: 2 ratios in viral-specific cells, suggesting that depletion of either subset would not remove viral immunity. Next, using FACS and immunohistochemistry, we showed that TCR+ cell lines (n = 8) and primary T-cell lymphomas and leukemias (n = 55) across a wide range of histological subtypes were entirely restricted to one compartment (34% TRBC1). As proof of concept for TRBC-selective therapy, we developed anti-TRBC1 chimeric antigen receptor (CAR) T-cells. After retroviral transduction of healthy donor T-cells, comprising mixed TRBC1/2 populations, 90% of T-cells expressed CAR on the cell surface. No detectable TRBC1 T-cells remained in the culture, suggesting selective depletion of this population. Anti-TRBC1 CAR T-cells secreted interferon-γ in response to TRBC1-expressing target cell lines (p In summary, we have demonstrated a novel approach to investigation and targeting of T-cell malignancies by distinguishing between two possible TCR β-chain constant regions. Using CART-cells targeting TRBC1 we have demonstrated proof of concept for anti-TRBC immunotherapy. Unlike non-selective approaches targeting the entire T-cell population, TRBC targeting could eradicate a T-cell tumour while preserving sufficient normal T-cells to maintain cellular immunity. Disclosures Maciocia: Autolus: Equity Ownership, Patents & Royalties: TRBC1 and 2 Targeting for the Diagnosis and Treatment of T-cell Malignancies. Philip:Autolus: Equity Ownership. Onuoha:Autolus: Employment, Equity Ownership. Pule:Amgen: Honoraria; Roche: Honoraria; UCL Business: Patents & Royalties; Autolus Ltd: Employment, Equity Ownership, Research Funding.

The HL-60 model of myeloid maturation was used to test whether changes in signaling from the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor accompany maturation-related changes in cellular responses to GM-CSF. Receptor expression, tyrosine phosphorylation, functional activity, and c-fos gene expression were measured. Functional GM-CSF receptors were present throughout differentiation as both uninduced and dimethyl sulfoxide (DMSO)-induced HL-60 cells responded to GM-CSF, albeit in different ways. Uninduced promyelocytes proliferated in response to GM-CSF, whereas DMSO-induced cells lost the capacity to proliferate but did respond with increased expression of beta 2-integrins, enhanced respiratory burst activity, and metabolism of arachidonic acid. GM-CSF-stimulated upregulation of c-fos mRNA expression was not detected in immature cells but developed after 2 to 4 days with DMSO in line with a marked increase in responsiveness to stimulation with phorbol ester, showing that increased expression of c- fos is predominantly a feature of mature phagocytes. GM-CSF stimulated the tyrosine phosphorylation of a broadly similar range of proteins in both uninduced and DMSO-treated HL-60 cells, but protein bands were more heavily phosphorylated in DMSO-induced cells. Phosphorylation was rapid in onset and very transient in immature cells. Phosphorylation of several proteins, in particular a 130-kD band, was more sustained in DMSO-induced cells. These differences in signaling were not because of numerical differences in receptors, because reduction of GM-CSF concentration to trigger equivalent numbers of high-affinity receptors delayed the onset of phosphorylation in DMSO-induced cells. We conclude that there are maturation-related changes in signaling downstream from the GM-CSF receptor.

The analysis of X-chromosome inactivation patterns has been used in a number of clinical situations such as the identification of carrier status in X-linked genetic disorders and the establishment of the monoclonal origin of tumors. Interpretation of the result obtained requires comparison with the constitutive pattern for the individual, and for hematopoietic malignancies, skin biopsies or cultured fibroblasts have often been used as the control tissue because normal cells of the same lineage as the malignancy are not generally available. However, this assumes that patterns in the different tissues are constitutionally the same. We have therefore compared X-chromosome inactivation patterns from peripheral blood (granulocytes, E- cells, and T cells), skin, and muscle from 20 hematologically normal females, and colonic mucosa from 9 individuals. In 11 patients (55%), the results obtained were similar for all tissues of an individual, but in 9 patients, significant differences were observed between tissues. The most consistent feature was a skewing in peripheral blood (> 75% expression of one allele) but not skin and/or muscle. These studies suggest that skin cannot be used as a control tissue for the interpretation of X-chromosome inactivation patterns in hematopoietic cells.

Heterozygous mutations in neutrophil elastase have been detected in many sporadic cases of congenital neutropenia. However, a convincing pathogenetic mechanism has not been established, and it is unclear whether the effects of the mutant enzyme occur within the cell of production or are paracrine in nature. The healthy father of a patient was demonstrated to be mosaic for his daughter's Cys42Arg elastase mutation. Using semiquantitative polymerase chain reaction, approximately half of his T cells were shown to carry the mutation in contrast to less than 10% of neutrophils. Individual hematopoietic colonies grown from peripheral blood were heterozygous for the mutation or were homozygous wild type. These results demonstrate that precursors containing the mutation are selectively lost during myelopoiesis or fail to develop into neutrophils. This is the first in vivo confirmation of the pathogenic nature of elastase mutations in humans. The normal neutrophil count in the father suggests that the mutant elastase does not have paracrine effects.

We read with interest the recent paper by Bolan et al documenting delayed donor red cell chimerism following major ABO-incompatible nonmyeloablative compared to myeloablative hematopoietic stem cell transplantation and an associated increased incidence of pure red cell aplasia (PRCA).[1][1] The

Although high-dose chemotherapy and autologous bone marrow transplantation (ABMT) are increasingly being used for the treatment of relapsed and resistant Hodgkin's disease, there have been few large, single-center studies reported with adequate follow-up to allow full evaluation of this therapeutic modality. We present 155 poor-risk Hodgkin's disease patients who received high-dose BEAM (BCNU, etoposide, cytosine arabinoside, and melphalan) chemotherapy and ABMT who have been studied over a period of 8 years. All patients had either not attained a remission on mechlorethamine, vincristine, procarbazine, prednisone-type therapy and had poor prognostic features at presentation, not attained a complete remission or relapsed within 1 year of an initial alternating regimen, or not attained remission with two or more lines of treatment. At the time of ABMT the relapse status of the patients was as follows: 46 patients were primarily refractory to induction therapy, 7 were good partial responders, 52 were in first relapse, 37 in second relapse, and 13 in third relapse. Seventy-eight patients had chemoresistant disease, 33 had chemosensitive disease at the time of ABMT, and 44 were untested for chemosensitivity at latest relapse. The procedure related mortality in the first 90 days post-ABMT of 10% overall. At 3 months 43 patients (28%) were assessed as complete responders, 72 patients had a partial response (46%), and 24 patients (16%) had no response or progression of disease. However, by 6 months, 53 (24%) patients were assessed as complete responders and 51 (33%) patients had nonprogressive disease. Forty-five patients had received radiotherapy post-ABMT to residual masses (41 patients) or to previous sites of bulk disease (4 patients). The actuarialoverall and progression-free survival at 5 years was 55% and 50%, respectively. On multivariate analysis patients with bulk (masses >10 cm), heavily pretreated patients (those receiving three or more lines of treatment) and females had a significantly poorer prognosis. Relapse status was also significant for progression-free survival in that patients in second (60%) and third relapse (70%) had a better prognosis than those in first relapse (44%) or with primary refractory disease (33%). Response to prior chemotherapy did not predict for progression-free survival. These results enable comparisons to be made between high-dose chemotherapy with ABMT and conventional dose salvage therapy. Furthermore, although the results as a whole are highly encouraging, certain groups carry an unfavorable prognosis.

Allogeneic stem cell transplantation (SCT) is an established therapy for patients with relapsed lymphoma, but the role of positron emission tomography (PET) scanning preallogeneic and postallogeneic SCT is uncertain. We investigated whether pretransplantation PET status predicted outcome after allogeneic SCT and whether PET surveillance after transplantation provided additional information compared with computed tomography (CT) scanning. Eighty consecutive patients with lymphoma who received a reduced-intensity allogeneic SCT were entered onto a prospective trial. PET and CT scans were performed before transplantation and up to 36 months after transplantation. Forty-two patients were PET-positive before transplantation. Pretransplantation PET status had no significant impact on either relapse rate or overall survival. Thirty-four relapses were observed, of which 17 were PET-positive with a normal CT scan at relapse. Donor lymphocyte infusion (DLI) was administered in 26 episodes of relapse and was guided by PET alone in 14 patients. These findings suggest that, in contrast to autologous SCT, pretransplantation PET status is not predictive of relapse and survival after allogeneic SCT for lymphoma. Posttransplantation surveillance by PET detected relapse before CT in half of episodes, often allowing earlier administration of DLI in patients with recurrent lymphoma, and permitted withholding of potentially harmful DLI in those with PET-negative masses on CT scans.

Plasma macrophage colony-stimulating factor (M-CSF) levels were measured by enzyme immunosorbent assay (ELISA) using horse and rabbit polyvalent antibodies raised against human M-CSF purified from urine (hM-CSF). Plasma M-CSF levels in nonpregnant female controls were 364 +/- 69 U/mL (mean +/- SD, n = 20). Pregnancy results in significant elevation of circulating M-CSF levels (541 +/- 164 U/mL, n = 46, P < .0005). M-CSF levels were increased by 28 weeks' gestation and did not increase further in later pregnancy. M-CSF levels were also measured in 20 female controls before and after commencing on the oral contraceptive pill. There was no effect of the contraceptive pill on plasma M-CSF levels (364 +/- 69 U/mL before v 373 +/- 66 U/mL after commencing on the pill). In 28 nonpregnant patients with untreated immune thrombocytopenic purpura, (ITP), plasma M-CSF levels were significantly increased (797 +/- 402 U/mL, n = 28, v 364 +/- 69 U/mL in controls, N = 20, P < .0005). Pregnant ITP patients had higher levels of plasma M-CSF (929 +/- 327 U/mL, n = 25) than nonpregnant patients, but this difference was not significant. Elevated levels of M-CSF in ITP may reflect activation of the reticuloendothelial system (RES), which could result in positive feedback to increase the destruction of platelets. The increase in M-CSF associated with pregnancy could contribute to the exacerbation of latent ITP in pregnancy.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) causes upregulation of neutrophil surface CD11b/CD18 expression, and enhances the adhesion of neutrophils to cultured human endothelial cells in vitro. Systemic administration of GM-CSF results in a rapid, transient decrease in circulating phagocyte numbers. Using a nonhuman primate model (Cynomolgus), we provide histologic evidence that this transient leukopenia is associated with the margination of neutrophils in the pulmonary microcirculation. In four animals receiving 2 to 15 micrograms/kg recombinant human GM-CSF (rhGM-CSF), light microscopic sections of lung contained 36 +/- 8, 17 +/- 7, 21 +/- 6, and 15 +/- 8 (mean +/- SD, n = 20) neutrophils within a graticule grid, as compared with two control animals receiving saline injections whose lung sections contained 2.1 +/- 1.6 and 3.1 +/- 2.1 (mean +/- SD, n = 20) neutrophils within the same grid. Scanning electron microscopy shows activated leukocytes adherent to pulmonary vascular endothelium, but no morphologic evidence of endothelial damage, and no migration of cells into the extravascular space. Margination is associated with an increase in surface expression of CD11b/CD18 on circulating phagocytes, which could contribute to the adhesion to capillary endothelial cells, but CD11b/CD18 levels remain elevated even when demargination is complete. In vitro, monoclonal antibodies (MoAbs) to CD18 and CD11b were able to inhibit neutrophil aggregation and adhesion to endothelium. FMLP-induced neutrophil aggregation was inhibited by 39.8% +/- 11.5% and 44.8% +/- 12.3%, respectively, by MoAbs to CD18 and CD11b (P less than .0005, n = 4 for both); a similar effect was demonstrated on TPA-induced aggregation. MoAb CD18 reduced the adhesion of unstimulated neutrophils to endothelium by 44% (P less than .01, n = 7), and inhibited the amount of GM-CSF-stimulated adhesion by 74% (P less than .001, n = 7), while MoAb to CD11b produced a reduction of unstimulated neutrophil adhesion by 30%, and of GM-CSF-stimulated adhesion by 40% (P less than .01, n = 5, for both). However, when administered in vivo, MoAb CD18 produced only a small, albeit significant, amelioration of GM-CSF-induced margination in vivo, while MoAb CD11b was without effect. These results show that GM-CSF-induced transient leukopenia is associated with enhanced neutrophil adherence to pulmonary vascular endothelium, but suggest that the beta 2 leukocyte integrins CD11/CD18 play only a minor role in this process.