We previously demonstrated that the anti-CD33 antibody drug conjugate gemtuzumab ozogamicin (GO) binds CD33-expressing monocytic myeloid-derived suppressor cells (M-MDSCs), is internalized, and decreases those cells' viability. Treatment of MDSCs with GO restores T-cell proliferation in co-culture, overcomes M-MDSC suppression of CAR-T cell proliferation, and enhances target-cell killing. Gemtuzumab Ozogamicin Therapy in Hemophagocytic Lymphohistiocytosis or Macrophage Activation Syndrome (GOTHAM) is a phase 2 single-arm clinical trial for which patients were eligible if they had a diagnosis of solid cancer with radiological or clinical evidence of disease progression, or primary or secondary hemophagocytic lymphohistiocytosis, or macrophage activation syndrome disease relapsing or refractory to treatment at enrollment. An initial regimen of 3 mg/m2 GO on days 1, 8, and 15 was tested, adjusted to 21-d intervals: days 1, 22, and 43. The primary outcome was the impact of GO therapy on peripheral CD33+ myeloid cells. Using 2 schedules of GO, we could not convincingly demonstrate safe feasibility in patients with solid cancer, because of neutropenia. However, GO reproducibly and significantly reduced circulating MDSCs. Importantly, there is consistent preliminary evidence that, upon rebound, the monocyte population of CD33+ cells is replaced with nonsuppressive monocytes. These data support the phase 1b dose-escalation testing of GO up to 2 mg/m2 in combination with immune checkpoint blockade and other immunotherapies in patients with solid cancer to find a dose that depletes and repolarizes MDSCs without causing undue neutropenia, paving the way to use GO as an immune potentiator in this patient population. Trial registration: ISRCTN 89158144.

Background Allogeneic stem cell transplant (allo-SCT) remains an important curative therapeutic modality in adults with high risk ALL. Reduced intensity conditioning (RIC) has extended the curative potential of allo-SCT to increasing numbers of older fit adults. There have been, however, no prospective randomised trials to guide the choice of the optimal RIC regimen in older adults with ALL. The UKALL14 trial previously reported outcomes for 249 adults >40y with ALL in CR1 who received fludarabine, melphalan and alemtuzumab (FMA) RIC allo-SCT. Overall survival (OS) at 4y was 55% with transplant-related mortality (TRM) 19.6%. The major cause of treatment failure was relapse (33.6% of patients by 4y) (Marks et al. 2022). Recent registry data has indicated that use of TBI is associated with improved disease outcomes (Giebel et al. 2017) in adult ALL patients receiving allo-SCT. We therefore performed a prospective, randomised comparison of the UK FMA RIC regimen with a cyclophosphamide plus 8Gy TBI RIC protocol (Cy/8TBI), with the goal of improving OS in high-risk adult ALL. Methods The FMA RIC regimen (fludarabine 30mg/m2 IV for 5d; melphalan 140mg/m2 IV single dose; alemtuzumab 30mg IV D-1 for sibling donor/20mg IV D-2 & -1 for unrelated donor) was compared to cyclophosphamide 50mg/kg for 2d plus 8Gy TBI (4# over 2d) and alemtuzumab (dosed as per FMA). Intrathecal prophylaxis was given for 2y post-SCT. Donor lymphocyte infusions were permitted for persistent minimal residual disease (MRD) or mixed donor T-cell chimerism from 3mo post-SCT. Primary endpoint was disease-free survival (DFS), with secondary endpoints including cumulative incidence of relapse (CIR), NRM, OS, GvHD rates and toxicity. Results Total 102 patients from 20 centres were randomised, with 89 proceeding to allo-SCT on study (45 FMA; 44 Cy/8TBI); 94 (92%) were in CR1 and 8 (7.8%) in CR2. Thirty patients (29.4%) had high risk cytogenetics (KMT2A-r; low hypodiploidy; complex karyotype), plus 31 (30.4%) Philadelphia positive cases. Median age of the entire cohort was 52y (IQR 46-59) with treatment arms being well balanced for pre-SCT characteristics. Total 31 (30%) and 71 (70%) patients received sibling and unrelated donor allo-SCT, respectively. Engraftment occurred in 85/89 (96%), with equivalent time to neutrophil and platelet engraftment between arms. With a median follow up of 41 months, 3y DFS by intention to treat (ITT) was 50% and 48% for FMA and Cy/8TBI, respectively (HR 1.12 [95% CI 0.64-1.95]; p=0.7). Neither cytogenetic risk nor pre-SCT MRD significantly affected DFS. At 3y, neither CIR (FMA 31% vs Cy/8TBI 36%; HR 1.23 [95% CI 0.63-2.42]; p=0.6), nor NRM (FMA 19% vs Cy/8TBI 16%; HR 0.81 [95% CI 0.32-2.07]; p=0.7) differed significantly between arms. OS at 3y (ITT) was also similar (FMA 61% vs Cy/8TBI 58%; HR 1.1; [95% CI 0.59-2.05]; p=0.8). Grade 2-4 aGvHD was seen in 2 (4.0%) and 5 (9.6%) patients with FMA and Cy/8TBI, respectively (p=0.44). No grade 3+ aGvHD was seen. Maximum grade 1 aGvHD occurred in 5 (10%) and 8 (15%) after FMA and Cy/8TBI, respectively. cGvHD developed in 4 (8%) FMA and 10 Cy/8TBI (19%) patients, with extensive in 6 (5.9%) patients, and no difference between arms (p=0.15). Total 97 and 102 SAEs were reported (in 30 and 26 patients) in the FMA and Cy/8TBI arms, respectively. Infections were not higher with Cy/8TBI (FMA 26 (27%); Cy/8TBI: 23 (23%)); nor were cardiac and pulmonary SAEs (FMA: 12 (12%); Cy/8TBI: 11 (11%)). Median total days of hospitalisation in year 1 did not differ between arms (FMA: 26 [IQR 22-33]; Cy/8TBI 27 [IQR 22-37]). During the study period, the most frequent causes of death in both arms were disease relapse (FMA 6 (32%); Cy/8TBI 9 (43%)) and infection (FMA 4 (21%); Cy/8TBI 8 (38%)). Conclusions This is the first prospective, randomised trial comparing RIC allo-SCT conditioning regimens in adult ALL. Cy/8TBI did not demonstrate superiority over a non-TBI FMA RIC protocol, achieving similar DFS and OS at 3y post-SCT. However, incorporation of 8Gy TBI into a RIC protocol designed for older adults was well tolerated, with no increases in acute or chronic GvHD, and no additional infectious or extramedullary toxicity. These data highlight the importance of performing randomised trials of innovative conditioning regimens, if outcomes for older patients receiving allo-SCT for ALL are to be improved. Importantly the ALL-RIC trial showcases feasibility and patient appetite for randomised transplant trials.

REFRACT is a randomised trial aimed at rapidly evaluating multiple novel therapies against standard treatment for relapsed or refractory follicular lymphoma (rrFL) using a minimal number of patients. To this end, we designed a prospective, adaptive, sequentially randomised clinical trial to allow multiple novel therapies to be assessed sequentially against a control arm of investigator choice standard therapy (ICT). REFRACT uses a Bayesian power priors approach enabling the sharing of control arm data from previous treatment rounds. The design allows for the randomisation ratio to be changed and fixed to 1:4 in later treatment rounds resulting in fewer patients being recruited to the control arm. Following extensive simulations, we arrived at the selected design of three sequential treatment rounds, each with a control group and a novel experimental arm assessed for the primary outcome of complete metabolic response (CMR) at 24 weeks. Patients in Round 1 are randomised using a 1:1 allocation, with Rounds 2 and 3 randomised using a 1:4 allocation, in favour of experimental treatment. Using Bayesian power priors, data from control patients in earlier rounds will be shared to improve the operating characteristics in the current round. Previous control arm patients will be weighted at 75

Introduction MRC AML 15 reported that high dose cytarabine (HD AraC) was not inferior to an anthracycline containing regimen as consolidation therapy in patients with non-high risk AML (Burnett, JCO 2013). Fludarabine and cytarabine (FLA) is a commonly used regimen particularly in relapsed AML. MyeChild01 aimed to test if FLA was superior to HD AraC as consolidation therapy in standard risk (SR) patients; both regimens anthracycline sparing and reducing the risk of cardiotoxicity. This paediatric trial for AML, high risk myelodysplastic syndrome (MDS > 10% blasts) or isolated myeloid sarcoma (IMS) delivered risk stratified treatment based on genetic subtype, remission status post course 1 and measurable residual disease (MRD). 360 patients were randomised to FLA or HD AraC as course 3 and 4 in consolidation from Jan-2017 to Oct-2022; 180 to each arm. Methods At diagnosis 97% patients were allocated mitoxantrone and cytarabine (MA) with 79% receiving 1 or 3 doses of GO in course 1 (Gibson, Blood; 144, Suppl 1, 2024). Subsequent treatment was stratified by genetic subtype, remission status post course 1 and MRD. SR patients had either good risk (GR) genetics and MRD negativity post course 2, or intermediate risk (IR) genetics and MRD negativity post course 1 and 2. SR patients received a second course of MA followed by two courses of either HD Ara C (3g/m2bd on days 1, 3, 5) or FLA (Fludarabine 30 mg/m2 and cytarabine 2g/m2on days 1-5) based on randomisation. Randomisation was stratified by age; diagnosis (AML, MDS, and IMS); disease type (de novo, secondary); number of gemtuzumab ozogamicin (GO) doses. Statistical analyses were Bayesian with primary outcome of relapse-free survival (RFS) defined as time from randomisation to relapse or death from any cause. Results Patient characteristics were: males 59%; median age 8yr; AML 96%, MDS 2%, IMS 2%; de novo 99.7%; genetic GR 54%, IR 44%. Induction therapy was MA 97%; with: no GO 14%; 1 dose GO 38%; 2 doses GO 7%; 3 doses GO 41%. Of the 360 patients 178 received HD AraC and 180 FLA; baseline characteristics were well balanced. Efficacy analysis included all patients;7 patients were excluded from safety summaries due to ineligibility/not receiving treatment. Median follow-up is 3.6 years. The 2yr RFS for HD AraC was 78% (72%, 85%) and for FLA 70% (64%, 77%) with a 2yr overall survival (OS) for HD AraC of 97% (94%, 99%) and for FLA 90% (86%, 95%). The Bayesian probability that FLA was superior to HD AraC was 7% for RFS and 8% for OS. No substantial differences in RFS were seen within subgroups of age, diagnosis, disease type, GO doses and genetic risk group. The 2yr cumulative incidence of relapse (CIR) for HD AraC was 22% (16%, 28%) and for FLA 29% (22%, 35%) indicating no difference (p=0.17). Only 2 deaths in remission were reported, both patients received FLA. Analysed by genetic risk group 97 GR and 78 IR patients received HD AraC while 96 GR and 80 IR received FLA; 9 patients without a risk group were excluded. In GR patients, 2yr RFS was 84% (78%, 92%) and 79% (71%, 88%), 2yr OS 98% (95%, 100%) and 98% (95%, 100%) and CIR 16% (9%, 23%) and 21% (14%, 30%) for HD AraC and FLA respectively. IR patients had a 2yr RFS of 69% (59%, 80%) and 62% (52%, 74%), 2yr OS of 95% (90%, 100%) and 81% (72%, 90%) and CIR of 31% (21%, 42%) and 35% (25%, 46%) for HD AraC and FLA respectively. IR patients consistently did worse than GR patients irrespective of treatment but had substantially worse OS rates with FLA. 67 patients with a KMT2A rearrangement were considered IR. At 2yr those who received HD AraC had RFS of 73% (60%, 89%), OS of 92% (84%, 100%) and CIR of 27% (14%, 42%) while those receiving FLA had RFS of 50% (35%, 72%), OS of 73% (58%, 91%) and CIR of 47% (28%, 63%). Incidence of grade ≥3 adverse reactions or any grade serious adverse events (SAE) for HD AraC was 56% and for FLA 53%. 54%of patients receiving HD AraC and 44% receiving FLA had at least one grade ≥3 SAE. There were two grade 5 SAEs both in the FLA arm; heart failure unrelated to FLA and CNS infection possibly related to FLA. The median time from the start of course 3 to course 4 was 38 days for HD AraC and 41 for FLA. Conclusion FLA is not superior to HD AraC as consolidation therapy in children with SR AML. Patients with IR genetics, particularly those with a non-high risk KMT2A rearrangement had a worse outcome with FLA. High Dose AraC should remain standard of care in consolidation for patients with SR AML.

Abstract Background Myelofibrosis (MF) is a clonal haematopoietic disease, with median overall survival for patients with primary MF only 6.5 years. The most frequent gene mutation found in patients is JAK2V617F, causing constitutive activation of the kinase and activation of downstream signalling. Fedratinib is an oral selective JAK2 inhibitor. It has shown activity in MF and is well-tolerated, but combination with other therapies is likely needed to achieve clonal remission. Combining a JAK2 inhibitor with an interferon may be synergistic, as haematopoietic cells are activated from quiescence (a typical kinase resistance mechanism) rendering them more sensitive to inhibition. Ropeginterferon alfa-2b is a next generation pegylated interferon-α-2b with high tolerability and clinical activity in patients with MF, however, evidence of tolerability and activity in combination with fedratinib is lacking in this setting. The aim of the FEDORA trial is to assess tolerability, safety, and activity of fedratinib with ropeginterferon alfa-2b in patients with MF who require treatment to justify further investigation in a phase III trial. Methods FEDORA is a single arm, multicentre, open-label, Bayesian phase II trial to assess tolerability, safety, and activity of fedratinib with ropeginterferon alfa-2b aiming to recruit 30 patients. Patients with JAK2V617F positive primary or secondary MF, who are aged ≥ 18 years, have intermediate-1 with palpable splenomegaly of > 5cm, intermediate-2, or high-risk disease according to the Dynamic International Prognostic Scoring System (DIPSS), and who require treatment are eligible. The primary outcome is tolerability, whereby the combination is deemed intolerable in a patient if drug-related toxicities in the first four months of treatment lead to: either drug being discontinued; delays in treatment exceeding 28 consecutive days; or death. FEDORA uses a within-patient dose escalation regimen to ensure each patient reaches a personalised dose combination that is acceptable. Discussion FEDORA is using a Bayesian trial design and aims to provide evidence of the tolerability, safety, and activity of combining fedratinib with ropeginterferon alfa-2b upon which the decision as to whether a phase III trial is warranted will be based. Trial registration EudraCT number: 2021–004056-42. ISRCTN: 88,102,629.

Purpose:Disease relapse remains the major cause of treatment failure in patients allografted for acute myeloid leukaemia (AML) and myelodysplasia (MDS). Accumulating data confirms an important contribution of the conditioning regimen to both disease control and transplant toxicity. Thiotepa (Thio) is an alkylating agent whose addition to a busulphan (Bu)/fludarabine (Flu) conditioning regimen has been shown in retrospective studies to improve survival in patients transplanted for AML using both matched unrelated and haploidentical donors, consequent upon a reduction in post-transplant relapse. As a result, Flu/Bu/Thio conditioning regimens are increasingly used in patients allografted for high risk AML despite the absence of prospective randomised trials supporting this practice. COSI is the first prospective randomised trial to examine the benefit of adding Thio to a Flu/Bu based myeloablative (MAC) or reduced intensity (RIC) conditioning regimen in patients allografted for AML in CR1 or CR2 or IPSS high risk MDS. Patients and methods:Three hundred and seventeen patients with high risk AML (n= 242: CR1 n=205, CR2 n=37), or MDS (n= 75) were randomly assigned to undergo transplantation from a matched related sibling (n=52) or matched unrelated donor (n=265) using either a Flu/Bu or Flu/Bu/Thio conditioning regimen. Ninety nine patients were transplanted using a MAC regimen (Flu 40 mg/m2 x 4 days, Bu 3.2 mg/kg x 4 days or Flu 50 mg/m2x 3 days, Bu 3.2 mg/kg x 3 days, Thio 5 mg/kg x 2 days) and 218 patients using a RIC regimen (Flu 30 mg/m2 x 5 days, Bu 3.2 mg/kg x 2 days, or Flu 50 mg/m2 x 3 days, Bu 3.2 mg/kg x 2 days, Thio 5 mg/kg x 1 day). All patients received ciclosporin/ATG-based GVHD prophylaxis. The primary endpoint was overall survival (OS). Results will be presented separately for the MAC (Randomisation 2) and RIC (Randomisation 3) arms of COSI, analysed on intent-to-treat basis analyses, adjusted for stratification factors where possible. The median age of the patients randomised to the MAC arm was 44 years (range 20-54 years) for the RIC arm was 64 (range 31-75 years). Pre-transplant measurable residual disease (MRD) was measured 28 days prior to transplant by flow cytometry (MFC-MRD) and correlated with outcome in both the MAC and RIC arms, using an MRD threshold of 0.1%. Results:In the 99 patients randomised to the MAC arm, addition of Thio to a Flu/Bu4 conditioning regimen did not increase 2 year OS: 75% using Flu/Bu4 versus 72% using Flu/Bu3/Thio (p=0.73). In patients who were MRD negative pre-transplant 2 year OS in patients transplanted using Flu/Bu4 was 81% versus 70% in patients transplanted using Flu/Bu3/Thio (p=0.91). In patients who were MRD positive pre-transplant 2 year OS using Flu/Bu4was 67% versus 63% for patients transplanted using Flu/Bu3/Thio (p=0.55). The 2 year cumulative incidence of relapse (CIR) was lower in patients transplanted using a Flu/Bu4/Thio conditioning regimen: 11% using Flu/Bu4/Thio versus 31% using Flu/Bu4 (p=<0.001). However, in contrast the 2-year transplant-related mortality (TRM) in patients transplanted using a Flu/Bu4/Thio regimen was increased: 22% using Flu/Bu4/Thio versus 4% using Flu/Bu4 (p=<0.001). In the 218 patients randomised to the RIC arm the addition of Thio did not increase 2 year OS: 71% using Flu/Bu2versus 69% using Flu/Bu2/Thio (p=0.87). In patients who were MRD negative pre-transplant 2 year OS was 84% using Flu/Bu2versus 75% for patients transplanted using Flu/Bu2/Thio (p=0.45). In patients who were MRD positive pre-transplant 2 year OS was 56% using Flu/Bu2/Thio versus 41% in patients transplanted using Flu/Bu2 (p=0.15). The 2 year TRM in patients transplanted using a Flu/Bu2/Thio regimen was increased: 17% using Flu/Bu2/Thio versus 8% using Flu/Bu2 (p=0.01). The 2 year CIR in patients transplanted using a Flu/Bu2/Thio regimen was 20% versus 30% in patients transplanted using a Flu/Bu2 regimen (p=0.12). Conclusion:This prospective randomised trial demonstrates that the addition of Thio to either a Flu/Bu based MAC or RIC regimen does not improve survival in patients allografted for AML or MDS and was associated with an increased TRM in both settings. Further prospective studies examining the ability of Thio to reduce the risk of disease relapse in high risk patients whilst at the same time limiting transplant toxicity are merited.

Myeloid-derived suppressor cells (MDSCs) are a paradigmatic, immunosuppressive cell population found in the blood and tumors of people with cancer. Alternatively-activated tumor-associated macrophages (TAMs) are immunosuppressive cells present in high numbers in the tumour microenvironment (TME) derived from circulating monocytes which in people with cancer are monocytic (M)-MDSC which migrate into the TME and polarise towards a macrophage phenotype. MDSCs express the common myeloid marker CD33. We previously reported that the anti-CD33 antibody drug conjugate, gemtuzumab ozogamicin (GO) binds predominantly to M-MDSCs, is rapidly internalised and induces dose-dependent decrease in viability. Treatment of circulating or tumor-polarised MDSCs with GO restores T cell proliferation in co-culture. We report here clinical proof of principle that the anti-CD33 antibody drug conjugate, gemtuzumab ozogamicin (GO) significantly reduces and subsequently repolarizes circulating M-MDSCs in cancer patients. 7 patients with relapsed/refractory cancer were treated with GO at a dose of 3mg/m2, 6 of whom had pMMR colorectal cancer (CRC) with liver metastases (LM). 0/4 patients treated on a day 1,8,15 schedule received all 3 doses and this schedule was deemed unfeasible. However, GO delivered 3-weekly was feasible and tolerable. GO administration using both dosing schedules caused a highly reproducible, and profound short-lived fall in the absolute number of circulating CD33+ cells at one week following administration which rebounds to values > baseline 2-3 weeks following each infusion. Importantly, using the 3-weekly schedule, at the time of rebound of the CD33+ CD14+ cells, there is a marked increase in the number of cells expressing HLA-DR, which suggested potential re-programming towards a less immunosuppressive phenotype following GO therapy. In line with the phenotypic shift in CD33+ cells at rebound, there is a sustained loss of monocyte suppression of activated CD4+ T cell proliferation. Thus, GO significantly reduces immunosuppressive CD33+ monocytoid cell numbers in pMMR CRC patients with LM and on CD33+ cell rebound these cells are both phenotypically and functionally no longer immune-suppressive. This loss of immune-suppressivity is maintained throughout the entire duration of treatment. Alternatively-polarised macrophages also express CD33 and are sensitive to GO. These results support the combination of 3 cycles of three-weekly GO alongside the initial 3 cycles of immune checkpoint blockade (ICB), during which time the initial proliferative burst is crucial, so as to improve ICB outcomes in those with liver metastatic disease, a metastatic site resistant to ICB. Gary Middleton, Aimee Jackson, Saly Al-Taei, Vicki Kunene, Su Lee, Anna Jackson, Joe Rogers, Francis Mussai, Carmen de Santo. The anti-CD33 antibody drug conjugate gemtuzumab ozogamicin depletes and re-programmes CD33+ myeloid-derived suppressor cells in patients with metastatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr CT220.

Background Relapsed or refractory follicular lymphoma (rrFL) is an incurable disease associated with shorter remissions and survival after each line of standard therapy. Many promising novel, chemotherapy-free therapies are in development, but few are licensed as their role in current treatment pathways is poorly defined. Methods The REFRACT trial is an investigator-initiated, UK National Cancer Research Institute, open-label, multi-centre, randomised phase II platform trial aimed at accelerating clinical development of novel therapies by addressing evidence gaps. The first of the three sequential novel therapy arms is epcoritamab plus lenalidomide, to be compared with investigator choice standard therapy (ICT). Patients aged 18 years or older with biopsy proven relapsed or refractory CD20 positive, grade 1-3a follicular lymphoma and assessable disease by PET-CT are eligible. The primary outcome is complete metabolic response by PET-CT at 24 weeks using the Deauville 5-point scale and Lugano 2014 criteria. Secondary outcomes include overall metabolic response, progression-free survival, overall survival, duration of response, and quality of life assessed by EQ-5D-5 L and FACT-Lym. The trial employs an innovative Bayesian design with a target sample size of 284 patients: 95 in the ICT arm and 189 in the novel therapy arms. Discussion Whilst there are many promising novel drugs in early clinical development for rrFL, understanding the relative efficacy and safety of these agents, and their place in modern treatment pathways, is limited by a lack of randomised trials and dearth of published outcomes for standard regimens to act as historic controls. Therefore, the aim of REFRACT is to provide an efficient platform to evaluate novel agents against standard therapies for rrFL. The adaptive Bayesian power prior methodology design will minimise patient numbers and accelerate trial delivery. Trial registration ClinicalTrials.gov: NCT05848765; 08-May-2023. EudraCT 2022-000677-75; 10-Feb-2022.

Introduction Adding one dose of 3mg/m2 of Gemtuzumab ozogamicin (GO), an anti CD33 antibody drug conjugate, showed an event-free survival (EFS) benefit in children with acute myeloid leukaemia (AML) in the AAML0531 trial (Gamis et al, JCO, 2014) whilst the adult ALFA-0701 trial reported a survival benefit of 3 fractionated doses with standard induction (Castaigne et al, Lancet, 2012). MyeChild 01, an international trial (UK, France, Australia, New Zealand, Ireland, Switzerland) for paediatric AML, high risk myelodysplastic syndrome (MDS > 10% blasts) or isolated myeloid sarcoma (IMS), embedded a GO dose finding study which established the safety of combining up to 3 doses of 3mg/m2 with intensive induction chemotherapy. 515 patients were randomised to 1 vs 3 doses of GO during course 1 (given on day 4 or days 4, 7, and 10 respectively), from Jan-2019 to Jun-2022. Due to regulatory commitments comparative results by randomisation are not available at the time of writing, but these data will be presented at the ASH annual meeting. Overall results are presented here. Methods Randomisation of GO doses was stratified by age; diagnosis (AML, MDS, IMS); disease type (de novo, secondary); white cell count (WCC) (<100, ≥100x109/L). Statistical analyses are by intention to treat with a primary outcome of EFS. All patients were allocated mitoxantrone and cytarabine (MA) with GO in course 1 and thereafter stratified by cyto/molecular genetics, remission status after course 1 and measurable residual disease (MRD). Patients with resistant disease post course 1 or poor risk (PR) cyto/molecular genetics were stratified high risk (HR) and received fludarabine, cytarabine and idarubicin (FLA-Ida) for course 2; all other patients received a second course of MA. Data is available on 472 patients; 142 received FLA-Ida and 330 MA. HR patients proceeded to allogeneic stem cell transplantation (HSCT). Non-HR patients were subsequently allocated treatment based on their cyto/molecular genetics and MRD response. Results Patient characteristics were: males 55%; median age 10yr; median WCC 14 x109/L; AML 96%, MDS 2.5%, isolated MS 1.9%; de novo 98%; CNS2 16%, CNS3 9%; non CNS extramedullary disease 16%. Of 515 patients randomised to 1 vs 3 doses, all but 16 received GO (6 ineligible, 5 prior toxicity, 5 other). 179 patients (35%) had a confirmed HSCT. Median follow-up is 3 years. The overall 2 yr EFS is 70% (95% CI: 66-74%) and overall survival (OS) 88% (85-91%). 94% achieved complete remission (CR) or CR with incomplete count recovery (CRi) post course 1 or 2; 6% failed to achieve CR/CRi (resistant disease 2.5%, non-evaluable 1%, unknown response 2.3%). 127 of 485 patients who achieved CR/CRi have relapsed giving a 2 yr cumulative incidence of relapse (CIR) of 25% (21-29%). Overall, there were 79 deaths but only 11 (2%) in first remission. 63 deaths were disease-related, 12 transplant-related, 3 off-trial treatment related and 1 other non-cancer. A cyto/molecular risk group was available for 485 patients: 192 GR (40%), 162 IR (33%) and 131 PR (27%). GR patients had a CR/CRi of 100%, 2 yr EFS 81% (76-87%), CIR 18% (13-24%) and OS 96% (93-99%); IR patients had a CR/CRi of 97.5%, 2 yr EFS 64% (57-72%), CIR 33% (26-41%) and OS 87% (82-93%); PR patients had a CR/CRi of 93.9%, 2 yr EFS 68%(61-77%), CIR 24%(16-32%) and OS 78% (71- 85%). Time to count recovery was defined as time from day 1 of a course to date of neutrophils >0.75 x109/L and platelets >75 x 109/L. Median count recovery was 41days post course 1, 44 days post course 2 MA and 45 days post course 2 FLA-Ida. 59%of patients had at least one grade ≥3 adverse event or any grade serious adverse event, evaluated from the start of treatment until 30 days after end of induction. Most events were consistent with AML chemotherapy. Only 9 patients (1.7%) had grade ≥3 hyperbilirubinemia and 2 patients confirmed veno-occlusive disease (VOD) in induction. Conclusion At least one dose of GO in combination with mitoxantrone and cytarabine in induction followed by risk-adapted therapy has produced excellent results. Despite intensive treatment the death in first remission rate is remarkably low at 2% and VOD was rare. Although this abstract reports only pooled data, outcomes for the 1 vs 3 dose GO randomisation will be presented at the ASH annual meeting.

Post-transplant lymphoproliferative disorder (PTLD) is a rare complication of solid organ transplantation, and cytotoxic chemotherapy is associated with treatment-related morbidity and mortality. Current treatment takes a sequential, risk-stratified approach, patients with low-risk disease following initial immunotherapy can avoid escalation to immunochemotherapy. TIDaL is a prospective, single-arm phase 2 trial investigating the activity and tolerability of ibrutinib combined with risk-stratified therapy for first-line treatment of PTLD. Eligible patients were adults with newly-diagnosed CD20-positive B-cell PTLD after solid organ transplant and performance status 0 to 2. Initial treatment comprised 49 days of ibrutinib 560mg once daily, with 4 doses of weekly rituximab. Treatment response on interim scan and baseline international prognostic index were used to allocate patients to either a low-risk arm (who continued ibrutinib, alongside 4 further doses of 3-weekly rituximab) or high-risk (escalation to R-CHOP immunochemotherapy, ibrutinib continuing in patients aged <65 years). The primary outcome was complete response on interim scan, achieved by 11/38 patients (29%, 95% confidence interval (CI) 15% - 46%). This did not reach the pre-specified threshold for clinically significant activity. Secondary outcomes included allocation to the low-risk arm (41% of patients), 2-year progression-free survival (58%, 95% CI 44% - 76%), and 2-year overall survival (76%, 95% CI 63% - 91%). Adverse events were mostly haematological, gastrointestinal and infective. Whilst TIDaL does not support adding ibrutinib into first-line treatment of PTLD, increasing the proportion of patients who can be treated without cytotoxic chemotherapy remains an important aim of future research. This trial was registered as ISRCTN32667607

Background The prognosis associated with a diagnosis of accelerated-phase (AP, 10-19% blasts) or blast-phase myeloproliferative neoplasms (BP-MPN, ≥20% blasts) remains dismal, with an unmet need for new therapy options. The phase Ib single-arm PHAZAR trial was designed to determine maximum tolerated dose (MTD), safety and efficacy of the JAK1/2 inhibitor ruxolitinib (RUX) in combination with azacitidine (AZA) in patients (pts) with AP/BP-MPN. This academic trial included serial banking of patient samples before and after treatment, providing a unique opportunity to interrogate the cellular and molecular basis of treatment response in AP/MP-MPN. Here we present the final analysis, including serial genetic and single cell transcriptomic profiling of paired samples from responders and non-responders. Method Cohorts of 3-5 patients were enrolled at a fixed AZA dose of 75 mg/m2 s/c for 7 days of a 28-day cycle with continuous oral RUX dosed at 10, 15, 20 or 25 mg BD using a Continuous Reassessment Method design. RUX/AZA-ineligible pts were recruited to an observational (obs) cohort. Baseline (BL) and serial (every 3 cycles) bone marrow (BM) samples were analysed by flow cytometry for hematopoietic stem and progenitor cell (HSPC) and myeloid blast epitopes, a myeloid gene panel, and single-cell CITE (Cellular indexing of transcriptomes and epitopes)-seq to define cell states in response to treatment. Results 58 AP/BP-MPN pts were recruited (n=34 RUX-AZA, n=24 obs). For the RUX-AZA cohort, median age was 72 yrs (range 55-85), 20/34 (59%) were male, and 15/34 (44%) in BP-MPN. Median number of RUX /AZA cycles were 4 (range 1 - 47). MTD was established as 25mg RUX BD as previously reported. 31 pts completed cycle 1 & were response evaluable. 5/31 (16%) pts achieved a complete response (CR) and 5/31 (16%) achieved a partial response (PR) after cycles 3 or 6, with an overall best response rate (CR or PR) of 10/31 (32%). Median response duration across all treatment cycles was 7.2 months (95% CI 2.8 - not reached). Median overall survival was 9.3 months (95% CI 5.7-26.3). For AP-(n=18) and BP-MPN (n=13) pts, 42% (95% CI 18-65%) and 26% (95% CI 6-51%) were alive and leukemia-free at 12 months. BL immunophenotyping confirmed aberrant HSPC profiles with an expanded CD34+Lin- population. AP/BP-MPN blasts were universally CD34+, CD117+ & expressed HLA-DR (90%) & monocytic markers CD13 (80%) and CD33 (50%), while negative for CD235ab. Documented clinical responses were confirmed by reduction in blast % by flow cytometry. Serial genotyping established that in non-responders and 80% of responders (including those with normal counts for > 12 months), there was no change in clone distribution nor emergence of new mutations on treatment. We reasoned that clinical response is therefore driven by altered cellular/molecular properties of cells within the mutant clone. In order to explore this further, serial samples at BL, response & relapse from responders with long-term survival (n=6: 5 CR, 1 PR), non-responders (n=6) and healthy controls (HC, n=5) were selected for CITE-seq (n=32 samples, n=123019 cells post QC) to investigate the impact of RUX-AZA on cell type composition and molecular state. Leukemic blasts were highly heterogeneous, arrested at different differentiation stages (monocytic 4/11, myeloid progenitor (prog) in 4/11, megakaryocyte/erythroid prog in 3/11 at BL). All BL samples showed a proportionate reduction in erythroid prog, while the eosinophil, basophil, mast prog population was expanded. Strikingly, despite no change in clonal burden, responders showed RUX-AZA induced release of the mutant HSPC-associated differentiation block with a notable increase in numbers of T-cells. HSC/MPP populations at the response timepoint were strongly enriched for inflammatory pathways with upregulation of IFN-a, IFN-g, TNFa and TGFb signatures. Blast populations in non-responders at treatment failure and also in responders at relapse showed upregulation of MYC and oxidative phosphorylation pathways, in keeping with increased proliferation and therapy resistance. Discussion Response to RUX-AZA in AP/BP-MPN is mediated by increased ability of mutant HSPC to differentiate to mature cell types and not by molecular (clonal) response. Response correlates with altered inflammation-associated gene expression and increased numbers of BM T-cells, providing insights into the possible mechanism of response to RUX-AZA.

Current therapies for myeloproliferative neoplasms (MPNs) improve symptoms but have limited effect on tumor size. In preclinical studies, tamoxifen restored normal apoptosis in mutated hematopoietic stem/progenitor cells (HSPCs). TAMARIN Phase-II, multicenter, single-arm clinical trial assessed tamoxifen’s safety and activity in patients with stable MPNs, no prior thrombotic events and mutated JAK2 V617F , CALR ins5 or CALR del52 peripheral blood allele burden ≥20% (EudraCT 2015-005497-38). 38 patients were recruited over 112w and 32 completed 24w-treatment. The study’s A’herns success criteria were met as the primary outcome ( ≥ 50% reduction in mutant allele burden at 24w) was observed in 3/38 patients. Secondary outcomes included ≥25% reduction at 24w (5/38), ≥50% reduction at 12w (0/38), thrombotic events (2/38), toxicities, hematological response, proportion of patients in each IWG-MRT response category and ELN response criteria. As exploratory outcomes, baseline analysis of HSPC transcriptome segregates responders and non-responders, suggesting a predictive signature. In responder HSPCs, longitudinal analysis shows high baseline expression of JAK-STAT signaling and oxidative phosphorylation genes, which are downregulated by tamoxifen. We further demonstrate in preclinical studies that in JAK2V617F+ cells, 4-hydroxytamoxifen inhibits mitochondrial complex-I, activates integrated stress response and decreases pathogenic JAK2-signaling. These results warrant further investigation of tamoxifen in MPN, with careful consideration of thrombotic risk.

Background: Outcomes for pediatric acute myeloid leukemia (AML) remain disappointing, particularly for patients with poor risk cytogenetic/molecular genetic abnormalities and those who fail to achieve complete remission following course 1 of induction chemotherapy. Despite upfront allogeneic hematopoietic stem cell transplantation (HSCT) for these patients, high rates of relapse persist. The optimal approach to chemotherapy intensification and timing of HSCT for high risk (HR) patients remains unknown, with variable approaches employed by cooperative trial groups. Methods: The MyeChild 01 international phase III trial (NCT02724163) in children with de novo AML allocated patients up to 3 doses of gemtuzumab ozogamicin (GO 3mg/m 2/dose) during the first course of induction chemotherapy (mitoxantrone 12 mg/m2/dose x4; cytarabine 100 mg/m2/dose x20). Patients classified as HR after course 1 received FLA-Ida for course 2 followed by allogeneic HSCT. If required, a third course of bridging therapy (FLA) was given prior to HSCT. HR patients in MyeChild 01 included those with NUP98 fusions, selected KMT2A fusions ( KMT2A::MLLT10, KMT2A::MLLT4, KMT2A::AFF1, KMT2A::ABI1), CBFA2T3::GLIS2, DEK::NUP214, MECOM ( EVI1) rearrangements and all 12p abnormalities including MNX1::ETV6, in addition to the traditional HR abnormalities -7, -5/del(5q) and FLT3-ITD (without concurrent good risk abnormalities, including NPM1 mutations). Patients with induction failure after course 1 (≥ 5% blasts confirmed by flow) and those with non-HR cytogenetics/molecular genetics who remained MRD positive after course 2 (intermediate risk cytogenetics) or 3 (good risk cytogenetics) were also classified as HR. Here, we report the estimated 2-year outcomes for patients assigned HR post course 1 who received mitoxantrone and cytarabine and at least 1 dose of GO during course 1 (MA-GO). Outcomes of trial randomisations (1 vs 2 or 3 GO doses; consolidation for standard risk patients; HSCT conditioning) will be reported separately. Results: Of 749 patients enrolled at initial diagnosis, 183 received MA-GO during course 1 and were assigned HR post course 1. Of these, 172 (94%) patients had poor risk cytogenetic/molecular genetics, of which 32 also failed to achieve CR. Additionally, 11 (6%) patients did not have poor risk cytogenetic/molecular genetics but failed to achieve CR with MA-GO and thus were assigned to the HR group. Post course 1, 140 (77%) of these HR patients achieved CR/CRi, with 102/155 (66%) patients with evaluable samples achieving MRD negativity post course 1. Following course 1, 174 (95%) remained on trial and received FLA-Ida as course 2 and 163 patients (89%) proceeded to HSCT, 55 on trial and 108 following discontinuation from the trial. Estimated event-free survival (EFS) and overall survival (OS) at 2 years was 62% (95% CI: 56-70%) and 71% (64-78%) respectively (Figure 1 & 2). Estimated cumulative incidence of relapse (CIR) and death in remission at 2 years was 26% (19-33%) and 7% (3-11%) respectively. For HR patients who received MA-GO in course 1, on trial FLA-Ida as course 2 and on or off trial HSCT (n = 156), 2 year estimated outcomes were EFS 69% (62-77%), OS 77% (70-85%) and CIR 24% (17-32%). The most common cytogenetic/molecular genetic abnormalities were rearrangements of KMT2A (50/183, 27%), with KMT2A::MLLT10 predominating (70%). FLT3-ITD (19%), NUP98 fusions (14%), -7 (13%), abn(12p) (11%), del(5q) (8%) and CBFA2T3::GLIS2 (6%) accounted for the majority of other abnormalities with outcomes varying by subtype. Collectively, KMT2A-rearranged patients had EFS and OS of 68% (55-83%) and 71% (59-86%) respectively and CIR of 26% (12-40%). For FLT3-ITD, the EFS and OS was 75% (62-92%) and 83% (69-99%) respectively with a CIR of 14% (1-26%). Of the 25 patients with a NUP98 fusion, 17 (68%) were NUP98::NSD1. The EFS and OS for patients with NUP98 fusions was 71% (55-92%) and 96% (88-100%) respectively with CIR 25% (1-48%). Conclusions: Two intensive courses of induction chemotherapy, including GO and mitoxantrone in course 1 and FLA-Ida in course 2, consolidated with allogeneic HSCT, appears to be an effective approach for most HR patients. 2 year estimated outcomes for HR patients compare favourably to recent trials of GO in pediatric AML, with particularly encouraging data for patients with KMT2A-r and FLT3-ITD.

PURPOSE:Polycythemia vera (PV) is characterized by JAK/STAT activation, thrombotic/hemorrhagic events, systemic symptoms, and disease transformation. In high-risk PV, ruxolitinib controls blood counts and improves symptoms. PATIENTS AND METHODS:MAJIC-PV is a randomized phase II trial of ruxolitinib versus best available therapy (BAT) in patients resistant/intolerant to hydroxycarbamide (HC-INT/RES). Primary outcome was complete response (CR) within 1 year. Secondary outcomes included duration of response, event-free survival (EFS), symptom, and molecular response. RESULTS:One hundred eighty patients were randomly assigned. CR was achieved in 40 (43%) patients on ruxolitinib versus 23 (26%) on BAT (odds ratio, 2.12; 90% CI, 1.25 to 3.60; P = .02). Duration of CR was superior for ruxolitinib (hazard ratio [HR], 0.38; 95% CI, 0.24 to 0.61; P < .001). Symptom responses were better with ruxolitinib and durable. EFS (major thrombosis, hemorrhage, transformation, and death) was superior for patients attaining CR within 1 year (HR, 0.41; 95% CI, 0.21 to 0.78; P = .01); and those on ruxolitinib (HR, 0.58; 95% CI, 0.35 to 0.94; P = .03). Serial analysis of JAK2V617F variant allele fraction revealed molecular response was more frequent with ruxolitinib and was associated with improved outcomes (progression-free survival [PFS] P = .001, EFS P = .001, overall survival P = .01) and clearance of JAK2V617F stem/progenitor cells. ASXL1 mutations predicted for adverse EFS (HR, 3.02; 95% CI, 1.47 to 6.17; P = .003). The safety profile of ruxolitinib was as previously reported. CONCLUSION:The MAJIC-PV study demonstrates ruxolitinib treatment benefits HC-INT/RES PV patients with superior CR, and EFS as well as molecular response; importantly also demonstrating for the first time, to our knowledge, that molecular response is linked to EFS, PFS, and OS.

COVID-19 causes significant thrombosis and coagulopathy, with elevated D-dimer a predictor of adverse outcome. The precise mechanism of this coagulopathy remains unclear; one hypothesis is that loss of angiotensin-converting enzyme 2 activity during viral endocytosis leads to pro-inflammatory angiotensin-II accumulation, loss of angiotensin-1-7 and subsequent vascular endothelial activation. We undertook a double-blind randomized, placebo-controlled experimental medicine study to assess the effect of TRV027, a synthetic angiotensin-1-7 analogue on D-dimer in 30 patients admitted to hospital with COVID-19. The study showed a similar rate of adverse events in TRV027 and control groups. There was a numerical decrease in D-dimer in the TRV027 group and increase in D-dimer in the placebo group; however, this did not reach statistical significance (P = .15). A Bayesian analysis demonstrated that there was a 92% probability that this change represented a true drug effect.

Introduction The usage of a T-cell depleted, reduced intensity conditioning (RIC) approach to haematopoietic cell transplantation (HCT) in adult patients with acute lymphoblastic leukaemia (ALL) over 40 years of age and in first complete remission (CR) has resulted in encouraging rates of event-free and overall survival in a population of adults with high risk disease. However, relapse rates remain high—with disease progression being the major cause of treatment failure. Using different, more powerful conditioning approaches is the logical next step in examining the role of RIC allogeneic HCT in adult ALL. Methods and analysis The ALL-RIC trial is a two-arm, phase II, multicentre, randomised clinical trial in adult patients with ALL in first or second CR, who are undergoing allogeneic HCT. Comparison of a novel RIC transplant conditioning regimen using reduced-dose total body irradiation (TBI), cyclophosphamide and alemtuzumab, is made against a standardised RIC approach using fludarabine, melphalan and alemtuzumab. The primary outcome of the study is disease-free survival at 3 years, defined as time from randomisation to the first of either relapse or death from any cause. Patients who are still alive and progression-free at the end of the trial will be censored at their last date known to be alive. Secondary outcomes include overall survival and non-relapse mortality. Ethics and dissemination The protocol was approved by the East Midlands—Leicester Central Research Ethics committee (18/EM/0112). Initial approval was received on 12 June 2018. Current protocol version (V.6.0) approval obtained on 18 November 2019. The Medicines and Healthcare products Regulatory Agency (MHRA) also approved all protocol versions. The results of this trial will be disseminated through national and international presentations and peer-reviewed publications. Trial registration number EudraCT Number: 2017-004800-23. ISRCTN99927695 .