Heterogeneous genetic and non-genetic mechanisms contribute to response and resistance to azacitidine monotherapy.

Acute myeloid leukaemia is prevalent in older patients that are often ineligible for intensive chemotherapy and treatment options remain limited with azacitidine being at the forefront. Azacitidine has been used in the clinic for decades, however, we still lack a complete understanding of the mechanisms by which the drug exerts its anti-tumour effect. To gain insight into the mechanism of action, we defined the mutational profile of sequential samples of patients treated with azacitidine. We did not identify any mutations that could predict response and observed lack of a uniform pattern of clonal evolution. Focusing on responders, at remission, we observed three types of response: (1) an almost complete elimination of mutations (33%), (2) no change (17%), and (3) change with no discernible pattern (50%). Heterogeneous patterns were also observed at relapse, with no clonal evolution between remission and relapse in some patients. Lack of clonal evolution suggests that non-genetic mechanisms might be involved. Towards understanding such mechanisms, we investigated the immune microenvironment in a number of patients and we observed lack of a uniform response following therapy. We identified a higher frequency of cytotoxic T cells in responders and higher frequency of naïve helper T cells in non-responders.

We do still transplant CML, don't we?

The remarkable clinical activity of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) has transformed patient outcome. Consequently, allogeneic stem cell transplantation (allo-SCT) is no longer the only treatment modality with the ability to deliver long-term survival. In contrast to the central position it held in the treatment algorithm 20 years ago, allografting is now largely reserved for patients with either chronic-phase disease resistant to TKI therapy or advanced-phase disease. Over the same period, progress in transplant technology, principally the introduction of reduced intensity conditioning regimens coupled with increased donor availability, has extended transplant options in patients with CML whose outcome can be predicted to be poor if they are treated with TKIs alone. Consequently, transplantation is still a vitally important, potentially curative therapeutic modality in selected patients with either chronic- or advanced-phase CML. The major causes of transplant failure in patients allografted for CML are transplant toxicity and disease relapse. A greater understanding of the distinct contributions made by various factors such as patient fitness, patient-donor HLA disparity, conditioning regimen intensity, and transplant toxicity increasingly permits personalized transplant decision making. At the same time, advances in the design of conditioning regimens coupled with the use of adjunctive posttransplant cellular and pharmacologic therapies provide opportunities for reducing the risk of disease relapse. The role of SCT in the management of CML will grow in the future because of an increase in disease prevalence and because of continued improvements in transplant outcome.

Cord Blood Unit Dominance Analysis and Effect of the Winning Unit on Outcomes after Double-Unit Umbilical Cord Blood Transplantation in Adults with Acute Leukemia: A Retrospective Study on Behalf of Eurocord, the Cord Blood Committee of Cellular Therapy, Immunobiology Working Party, and the Acute Leukemia Working Party of the European Group for Blood and Marrow Transplantation.

Usually, after double umbilical cord blood transplantation (DUCBT), only 1 of the transplanted units persists in the long term. The characteristics of the winning cord blood unit (W-CBU) that determine unit dominance and how they influence the outcomes of DUCBT remain unclear. We retrospectively analyzed 347 patients with acute leukemia transplanted with a DUCBT (694 CBU) from 2005 to 2013 who had documented neutrophil engraftment and a W-CBU identified by chimerism analysis, to identify unit characteristics impacting on dominance. Median age at DUCBT was 40 years and median follow-up was 35 months. Among W-CBUs, 41% were ≥5/6 HLA matched to the recipient and 59% were ≤4/6. Multivariate analysis indicated that ≤4/6 HLA-matched W-CBUs led to lower leukemia-free survival (44% versus 56%; hazard ratio [HR], 1.5; P = .032) and overall survival (49% versus 62%; HR, 1.5; P = .028), increased nonrelapse mortality (26% versus 18%; HR, 1.9; P = .027), and acute graft-versus-host disease (46% versus 35%; HR, 1.7; P = .013). We were unable to predict unit dominance, but we demonstrated that outcomes were strongly influenced by the degree of HLA mismatch between W-CBU and recipient. Therefore, selection of both units with the lower number of HLA mismatches with the recipient is indicated.

Outcome of Azacitidine Therapy in Acute Myeloid Leukemia Is not Improved by Concurrent Vorinostat Therapy but Is Predicted by a Diagnostic Molecular Signature.

Purpose: Azacitidine (AZA) is a novel therapeutic option in older patients with acute myeloid leukemia (AML), but its rational utilization is compromised by the fact that neither the determinants of clinical response nor its mechanism of action are defined. Co-administration of histone deacetylase inhibitors, such as vorinostat (VOR), is reported to improve the clinical activity of AZA, but this has not been prospectively studied in patients with AML.Experimental Design: We compared outcomes in 259 adults with AML (n = 217) and MDS (n = 42) randomized to receive either AZA monotherapy (75 mg/m2 × 7 days every 28 days) or AZA combined with VOR 300 mg twice a day on days 3 to 9 orally. Next-generation sequencing was performed in 250 patients on 41 genes commonly mutated in AML. Serial immunophenotyping of progenitor cells was performed in 47 patients.Results: Co-administration of VOR did not increase the overall response rate (P = 0.84) or overall survival (OS; P = 0.32). Specifically, no benefit was identified in either de novo or relapsed AML. Mutations in the genes CDKN2A (P = 0.0001), IDH1 (P = 0.004), and TP53 (P = 0.003) were associated with reduced OS. Lymphoid multipotential progenitor populations were greatly expanded at diagnosis and although reduced in size in responding patients remained detectable throughout treatment.Conclusions: This study demonstrates no benefit of concurrent administration of VOR with AZA but identifies a mutational signature predictive of outcome after AZA-based therapy. The correlation between heterozygous loss of function CDKN2A mutations and decreased OS implicates induction of cell-cycle arrest as a mechanism by which AZA exerts its clinical activity. Clin Cancer Res; 23(21); 6430-40. ©2017 AACR.

Memory B-cell reconstitution following allogeneic hematopoietic stem cell transplantation is an EBV-associated transformation event.

Allogeneic stem cell transplantation (allo-HSCT) provides a unique opportunity to track Epstein-Barr virus (EBV) infection in the context of the reconstituting B-cell system. Although many allo-HSCT recipients maintain low or undetectable levels of EBV DNA posttransplant, a significant proportion exhibit elevated and rapidly increasing EBV loads which, if left untreated, may lead to potentially fatal EBV-associated posttransplant lymphoproliferative disease. Intriguingly, this high-level EBV reactivation typically arises in the first 3 months posttransplant, at a time when the peripheral blood contains low numbers of CD27+ memory cells which are the site of EBV persistence in healthy immunocompetent donors. To investigate this apparent paradox, we prospectively monitored EBV levels and B-cell reconstitution in a cohort of allo-HSCT patients for up to 12 months posttransplant. In patients with low or undetectable levels of EBV, the circulating B-cell pool consisted predominantly of transitional and naive cells, with a marked deficiency of CD27+ memory cells which lasted >12 months. However, among patients with high EBV loads, there was a significant increase in both the proportion and number of CD27+ memory B cells. Analysis of sorted CD27+ memory B cells from these patients revealed that this population was preferentially infected with EBV, expressed EBV latent transcripts associated with B-cell growth transformation, had a plasmablastic phenotype, and frequently expressed the proliferation marker Ki-67. These findings suggest that high-level EBV reactivation following allo-HSCT may drive the expansion of latently infected CD27+ B lymphoblasts in the peripheral blood.

Tyrosine kinase inhibitors improve long-term outcome of allogeneic hematopoietic stem cell transplantation for adult patients with Philadelphia chromosome positive acute lymphoblastic leukemia.

This study aimed to determine the impact of tyrosine kinase inhibitors given pre- and post-allogeneic stem cell transplantation on long-term outcome of patients allografted for Philadelphia chromosome-positive acute lymphoblastic leukemia. This retrospective analysis from the EBMT Acute Leukemia Working Party included 473 de novo Philadelphia chromosome-positive acute lymphoblastic leukemia patients in first complete remission who underwent an allogeneic stem cell transplantation using a human leukocyte antigen-identical sibling or human leukocyte antigen-matched unrelated donor between 2000 and 2010. Three hundred and ninety patients received tyrosine kinase inhibitors before transplant, 329 at induction and 274 at consolidation. Kaplan-Meier estimates of leukemia-free survival, overall survival, cumulative incidences of relapse incidence, and non-relapse mortality at five years were 38%, 46%, 36% and 26%, respectively. In multivariate analysis, tyrosine-kinase inhibitors given before allogeneic stem cell transplantation was associated with a better overall survival (HR=0.68; P=0.04) and was associated with lower relapse incidence (HR=0.5; P=0.01). In the post-transplant period, multivariate analysis identified prophylactic tyrosine-kinase inhibitor administration to be a significant factor for improved leukemia-free survival (HR=0.44; P=0.002) and overall survival (HR=0.42; P=0.004), and a lower relapse incidence (HR=0.40; P=0.01). Over the past decade, administration of tyrosine kinase inhibitors before allogeneic stem cell transplantation has significantly improved the long-term allogeneic stem cell transplantation outcome of adult Philadelphia chromosome-positive acute lymphoblastic leukemia. Prospective studies will be of great interest to further confirm the potential benefit of the prophylactic use of tyrosine kinase inhibitors in the post-transplant setting.

Subsequent donation requests among 2472 unrelated hematopoietic progenitor cell donors are associated with bone marrow harvest.

Approximately 1 in 20 unrelated donors are asked to make a second donation of hematopoietic progenitor cells, the majority for the same patient. Anthony Nolan undertook a study of subsequent hematopoietic progenitor cell donations made by its donors from 2005 to 2011, with the aims of predicting those donors more likely to be called for a second donation, assessing rates of serious adverse reactions and examining harvest yields. This was not a study of factors predictive of second allografts. During the study period 2591 donations were made, of which 120 (4.6%) were subsequent donations. The median time between donations was 179 days (range, 21-4016). Indications for a second allogeneic transplant included primary graft failure (11.7%), secondary graft failure (53.2%), relapse (30.6%) and others (1.8%). On multivariate analysis, bone marrow harvest at first donation was associated with subsequent donation requests (odds ratio 2.00, P=0.001). The rate of serious adverse reactions in donors making a subsequent donation appeared greater than the rate in those making a first donation (relative risk=3.29, P=0.005). Harvest yields per kilogram recipient body weight were equivalent between donations, although females appeared to have a lower yield at the subsequent donation. Knowledge of these factors will help unrelated donor registries to counsel their donors.

Addition of gemtuzumab ozogamicin to induction chemotherapy improves survival in older patients with acute myeloid leukemia.

PURPOSE: There has been little survival improvement in older patients with acute myeloid leukemia (AML) in the last two decades. Improving induction treatment may improve the rate and quality of remission and consequently survival. In our previous trial, in younger patients, we showed improved survival for the majority of patients when adding gemtuzumab ozogamicin (GO) to induction chemotherapy. PATIENTS AND METHODS: Untreated patients with AML or high-risk myelodysplastic syndrome (median age, 67 years; range, 51 to 84 years) were randomly assigned to receive induction chemotherapy with either daunorubicin/ara-C or daunorubicin/clofarabine, with (n = 559) or without (n = 556) GO 3 mg/m(2) on day 1 of course one of therapy. The primary end point was overall survival (OS). RESULTS: The overall response rate was 69% (complete remission [CR], 60%; CR with incomplete recovery [CRi], 9%), with no difference between GO (70%) and no GO (68%) arms. There was no difference in 30- or 60-day mortality and no major increase in toxicity with GO. With median follow-up of 30 months (range, 5.5 to 54.6 months), 3-year cumulative incidence of relapse was significantly lower with GO (68% v 76%; hazard ratio [HR], 0.78; 95% CI, 0.66 to 0.93; P = .007), and 3-year survival was significantly better (25% v 20%; HR, 0.87; 95% CI, 0.76 to 1.00; P = .05). The benefit was apparent across subgroups. There was no interaction with other treatment interventions. A meta-analysis of 2,228 patients in two United Kingdom National Cancer Research Institute trials showed significant improvements in relapse (HR, 0.82; 95% CI, 0.72 to 0.93; P = .002) and OS (HR, 0.88; 95% CI, 0.79 to 0.98; P = .02). CONCLUSION: Adding GO (3 mg/m(2)) to induction chemotherapy reduces relapse risk and improves survival with little increase in toxicity.

Azacitidine augments expansion of regulatory T cells after allogeneic stem cell transplantation in patients with acute myeloid leukemia (AML).

Strategies that augment a GVL effect without increasing the risk of GVHD are required to improve the outcome after allogeneic stem cell transplantation (SCT). Azacitidine (AZA) up-regulates the expression of tumor Ags on leukemic blasts in vitro and expands the numbers of immunomodulatory T regulatory cells (Tregs) in animal models. Reasoning that AZA might selectively augment a GVL effect, we studied the immunologic sequelae of AZA administration after allogeneic SCT. Twenty-seven patients who had undergone a reduced intensity allogeneic transplantation for acute myeloid leukemia were treated with monthly courses of AZA, and CD8(+) T-cell responses to candidate tumor Ags and circulating Tregs were measured. AZA after transplantation was well tolerated, and its administration was associated with a low incidence of GVHD. Administration of AZA increased the number of Tregs within the first 3 months after transplantation compared with a control population (P = .0127). AZA administration also induced a cytotoxic CD8(+) T-cell response to several tumor Ags, including melanoma-associated Ag 1, B melanoma antigen 1, and Wilm tumor Ag 1. These data support the further examination of AZA after transplantation as a mechanism of augmenting a GVL effect without a concomitant increase in GVHD.

Posttransplantation imatinib as a strategy to postpone the requirement for immunotherapy in patients undergoing reduced-intensity allografts for chronic myeloid leukemia.

Disease relapse is a major cause of treatment failure after reduced-intensity allografts and while donor lymphocyte infusions (DLIs) can be effective salvage therapy they are associated with severe graft-versus-host disease (GVHD) when administered early after transplantation. We have therefore examined whether imatinib mesylate can delay relapse and postpone the requirement for DLI in 22 patients with chronic myeloid leukemia (CML) allografted using a reduced-intensity regimen. Imatinib was commenced on day + 35 and continued until 1 year after transplantation. Posttransplantation imatinib was well tolerated and abolished the risk of relapse during this period. Twenty-one patients completed 11 months of imatinib therapy, 15 of whom subsequently relapsed and received DLI. Ten patients to date have achieved molecular remission after DLI. Adjunctive targeted therapy allows the kinetics of disease relapse after a reduced-intensity allograft to be manipulated and represents a novel strategy by which outcome may be improved in patients who undergo transplantation for CML and other leukemias.

The impact of donor KIR and patient HLA-C genotypes on outcome following HLA-identical sibling hematopoietic stem cell transplantation for myeloid leukemia.

Killer immunoglobulin-like receptors (KIRs) regulate cell activity of natural killer (NK) cells and some T cells. The predominant ligand for inhibitory KIRs is HLA-C, which subdivides into 2 groups based on the specificity of inhibitory KIRs. The ligands for activatory KIRs are unknown. Following hematopoietic stem cell transplantation (HSCT), recipient tissues may not express a ligand for KIRs present within the graft, and the combination of donor KIR and recipient HLA-C types could influence outcome. HLA and KIR genotypes were determined in 220 donor-recipient pairs from HLA-matched sibling HSCTs performed for myeloid (n = 112) and lymphoid (n = 108) diseases. In HSCTs performed for myeloid disease, overall survival was worse in patients homozygous for group 2 HLA-C (C2) than in patients who carried a group 1 HLA-C (C1) allele (P <.005). Moreover, this effect is seen only when the donor additionally carries the activating KIR gene KIR2DS2 (P =.045). No effect was seen in patients with lymphoid disease. Thus, in HLA-matched sibling HSCT for myeloid leukemia, patients homozygous for C2 alleles receiving a graft from a donor carrying the KIR gene KIR2DS2 have a significantly reduced chance of survival.

The T-lineage-affiliated CD2 gene lies within an open chromatin environment in acute promyelocytic leukemia cells.

The nature of hemopoietic progenitors subject to leukemic transformation in acute myeloid leukemia (AML) has not been clearly defined. To address this issue, we have used DNase I hypersensitivity assays to study the chromatin structure surrounding the T-lineage-affiliated CD2 gene in the acute promyelocytic subtype of AML (APL). Upstream and downstream flanking regions of CD2 were found to be hypersensitive to DNase I in primary APL blasts, with an identical pattern of hypersensitive sites to those detected in cells of T-lineage. All of the sites were confirmed to be inaccessible to DNase I in B-lineage leukemia cells. The demonstration of T-cell-associated chromatin features in primary APL blasts has implications for the origin of APL that may arise in more primitive progenitors than previously considered to be the case.