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Disease relapse is the major causes of treatment failure after allogeneic stem cell transplantation (SCT) in patients with acute myeloid leukemia (AML). As well as demonstrating significant clinical activity in AML, azacitidine (AZA) upregulates putative tumor antigens, inducing a CD8+ T cell response with the potential to augment a graft-versus-leukemia effect. We, therefore, studied the feasibility and clinical sequelae of the administration of AZA during the first year after transplantation in 51 patients with AML undergoing allogeneic SCT. Fourteen patients did not commence AZA either because of transplantation complications or withdrawal of consent. Thirty-seven patients commenced AZA at a median of 54 days (range, 40 to 194 days) after transplantation, which was well tolerated in the majority of patients. Thirty-one patients completed 3 or more cycles of AZA. Sixteen patients relapsed at a median time of 8 months after transplantation. No patient developed extensive chronic graft-versus-host disease. The induction of a post-transplantation CD8+ T cell response to 1 or more tumor-specific peptides was studied in 28 patients. Induction of a CD8+ T cell response was associated with a reduced risk of disease relapse (hazard ratio [HR], .30; 95% confidence interval [CI], .10 to .85; P = .02) and improved relapse-free survival (HR, .29; 95% CI, .10 to .83; P = .02) taking into account death as a competing risk. In conclusion, AZA is well tolerated after transplantation and appears to have the capacity to reduce the relapse risk in patients who demonstrate a CD8+ T cell response to tumor antigens. These observations require confirmation in a prospective clinical trial.

Epigenetic therapies demonstrate significant clinical activity in acute myeloid leukemia (AML) and myelodysplasia (MDS) and constitute an important new class of therapeutic agents. However hematological responses are not durable and disease relapse appears inevitable. Experimentally, leukemic stem/progenitor cells (LSC) propagate disease in animal models of AML and it has been postulated that their relative chemo-resistance contributes to disease relapse. We serially measured LSC numbers in patients with high-risk AML and MDS treated with 5'-azacitidine and sodium valproate (VAL-AZA). Fifteen out of seventy-nine patients achieved a complete remission (CR) or complete remission with incomplete blood count recovery (CRi) with VAL-AZA therapy. There was no significant reduction in the size of the LSC-containing population in non-responders. While the LSC-containing population was substantially reduced in all patients achieving a CR/CRi it was never eradicated and expansion of this population antedated morphological relapse. Similar studies were performed in seven patients with newly diagnosed AML treated with induction chemotherapy. Eradication of the LSC-containing population was observed in three patients all of whom achieved a durable CR in contrast to patients with resistant disease where LSC persistence was observed. LSC quantitation provides a novel biomarker of disease response and relapse in patients with AML treated with epigenetic therapies. New drugs that target this cellular population in vivo are required.

PURPOSE Reduced-intensity conditioning (RIC) regimens have extended the curative potential of allogeneic stem-cell transplantation to older adults with high-risk acute myeloid leukemia (AML) and myelodysplasia (MDS) but are associated with a high risk of disease relapse. Strategies to reduce recurrence are urgently required. Registry data have demonstrated improved outcomes using a sequential transplant regimen, fludarabine/amsacrine/cytarabine-busulphan (FLAMSA-Bu), but the impact of this intensified conditioning regimen has not been studied in randomized trials. PATIENTS AND METHODS Two hundred forty-four patients (median age, 59 years) with high-risk AML (n = 164) or MDS (n = 80) were randomly assigned 1:1 to a fludarabine-based RIC regimen or FLAMSA-Bu. Pretransplant measurable residual disease (MRD) was monitored by flow cytometry (MFC-MRD) and correlated with outcome. RESULTS There was no difference in 2-year overall survival (hazard ratio 1.05 [85% CI, 0.80 to 1.38] P = .81) or cumulative incidence of relapse (CIR) (hazard ratio 0.94 [95%CI, 0.60 to 1.46] P = .81) between the control and FLAMSA-Bu arms. Detectable pretransplant MFC-MRD was associated with an increased CIR (2-year CIR 41.0% v 20.0%, P = .01) in the overall trial cohort with a comparable prognostic impact when measured by an unsupervised analysis approach. There was no evidence of interaction between MRD status and conditioning regimen intensity for relapse or survival. Acquisition of full donor T-cell chimerism at 3 months abrogated the adverse impact of pretransplant MRD on CIR and overall survival. CONCLUSION The intensified RIC conditioning regimen, FLAMSA-Bu, did not improve outcomes in adults transplanted for high-risk AML or MDS regardless of pretransplant MRD status. Our data instead support the exploration of interventions with the ability to accelerate acquisition of full donor T-cell chimerism as a tractable strategy to improve outcomes in patients allografted for AML.

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.

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 ¼ 217) and MDS (n ¼ 42) randomized to receive either AZA monotherapy (75 mg/m 2 Â 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 ¼ 0.84) or overall survival (OS; P ¼ 0.32). Specifically, no benefit was identified in either de novo or relapsed AML. Mutations in the genes CDKN2A (P ¼ 0.0001), IDH1 (P ¼ 0.004), and TP53 (P ¼ 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.

PURPOSE Salvage options for patients who relapse after allogeneic stem-cell transplantation (allo-SCT) for acute myeloid leukemia (AML) and myelodysplasia (MDS) remain limited, and novel treatment strategies are required. Both lenalidomide (LEN) and azacitidine (AZA) possess significant antitumor activity effect in AML. Administration of LEN post-transplantation is associated with excessive rates of graft-versus-host disease (GVHD), but AZA has been shown to ameliorate GVHD in murine transplantation models. We therefore examined the tolerability and activity of combined LEN/AZA administration in post-transplantation relapse. PATIENTS AND METHODS Twenty-nine patients who had relapsed after allo-SCT for AML (n = 24) or MDS (n = 5) were treated with sequential AZA (75 mg/m2 for 7 days) followed by escalating doses of LEN on days 10 to 30. Dose allocation and maximum tolerated dose (MTD) estimation were guided by a modified Bayesian continuous reassessment method (CRM). RESULTS Sequential AZA and LEN therapy was well tolerated. The MTD of post-transplantation LEN, in combination with AZA, was determined as 25 mg daily. Three patients developed grade 2 to 4 GVHD. There was no GVHD-related mortality. Seven of 15 (47%) patients achieved a major clinical response after LEN/AZA therapy. CD8+ T cells demonstrated impaired interferon-γ/tumor necrosis factor–α production at relapse, which was not reversed during LEN/AZA administration. CONCLUSION We conclude LEN can be administered safely post-allograft in conjunction with AZA, and this combination demonstrates clinical activity in relapsed AML/MDS without reversing biologic features of T-cell exhaustion. The use of a CRM model delivered improved efficiency in MTD assessment and provided additional flexibility. Combined LEN/AZA therapy represents a novel and active salvage therapy in patients who had relapsed post-allograft.