Therapeutic value of clofarabine in younger and middle-aged (18-65 years) adults with newly diagnosed AML.

Clofarabine has demonstrated antileukemic activity in acute myeloid leukemia (AML) but has yet to be critically evaluated in younger adults in the frontline with standard chemotherapy. We compared 2 induction regimens in newly diagnosed patients ages 18 to 65 with acute myeloid leukemia (AML)/high-risk myelodysplastic syndromes, that is, idarubicine-cytarabine (cycle I) and amsacrine-cytarabine (cycle II) without or with clofarabine (10 mg/m2 on days 1-5 of each of both cycles). Consolidation involved chemotherapy with or without hematopoietic stem cell transplantation. Event-free survival (EFS, primary endpoint) and other clinical endpoints and toxicities were assessed. We randomized 402 and 393 evaluable patients to the control or clofarabine induction treatment arms. Complete remission rates (89%) did not differ but were attained faster with clofarabine (66% vs 75% after cycle I). Clofarabine added grades 3 to 4 toxicities and delayed hematological recovery. At a median follow-up of 36 months, the study reveals no differences in overall survival and EFS between the control (EFS, 35% ± 3 [standard error] at 4 years) and clofarabine treatments (38% ± 3) but a markedly reduced relapse rate (44% ± 3 vs 35% ± 3) in favor of clofarabine and an increased death probability in remission (15% ± 2 vs 22% ± 3). In the subgroup analyses, clofarabine improved overall survival and EFS for European Leukemia Net (ELN) 2010 intermediate I prognostic risk AML (EFS, 26% ± 4 vs 40% ± 5 at 4 years; Cox P = .002) and for the intermediate risk genotype NPM1 wild-type/FLT3 without internal-tandem duplications (EFS, 18% ± 5 vs 40% ± 7; Cox P < .001). Clofarabine improves survival in subsets of intermediate-risk AML only. HOVON-102 study is registered at Netherlands Trial Registry #NTR2187.

The value of allogeneic and autologous hematopoietic stem cell transplantation in prognostically favorable acute myeloid leukemia with double mutant CEBPA.

The clinical value of allogeneic hematopoietic stem cell transplantation (alloHSCT) and autologous hematopoietic stem cell transplantation (autoHSCT) in the subtype of acute myeloid leukemia (AML) with double mutant CEBPA (CEBPAdm) has remained unsettled. Among 2983 patients analyzed for CEBPA mutational status (age 18-60 years) treated on 4 published Dutch-Belgian-Swiss Hemato-Oncology Cooperative Group (HOVON/SAKK) and 3 German-Austrian AML Study Group (AMLSG) protocols (2 published, 1 registered, clinicaltrials.gov NCT00151255), 124 had AML with CEBPAdm and achieved first complete remission (CR1). Evaluation of the clinical impact of alloHSCT and autoHSCT vs chemotherapy was performed by addressing time dependency in the statistical analyses. Thirty-two patients proceeded to alloHSCT from a matched related (MRD, n = 29) or a matched unrelated donor (MUD, n = 3), 20 to autoHSCT in CR1 and 72 received chemotherapy. Relapse-free survival was significantly superior in patients receiving an alloHSCT or autoHSCT in CR1 as compared with chemotherapy (P < .001), whereas overall survival was not different (P < .12). Forty-five patients relapsed. Of 42 patients treated with reinduction therapy, 35 achieved a second CR (83%) and most patients (n = 33) received an alloHSCT MRD, n = 11; MUD, n = 19; haplo-identical donor, n = 3). Survival of relapsed patients measured from date of relapse was 46% after 3 years. Adult AML patients with CEBPAdm benefit from alloHSCT and autoHSCT; relapsed patients still have a favorable outcome after reinduction followed by alloHSCT.

Impact of postremission consolidation chemotherapy on outcome after reduced-intensity conditioning allogeneic stem cell transplantation for patients with acute myeloid leukemia in first complete remission: a report from the Acute Leukemia Working Party of the European Group for Blood and Marrow Transplantation.

BACKGROUND: The objective of the current study was to investigate the role of postremission consolidation chemotherapy before reduced-intensity conditioning (RIC) allogeneic stem cell transplantation (alloSCT) for patients with acute myeloid leukemia (AML) in first complete remission (CR1). METHODS: Of the 789 consecutive patients with AML in CR1 who underwent RIC alloSCT from a human leukocyte antigen-matched sibling or matched unrelated donor peripheral stem cell grafts between 2001 and 2010, 591 patients received at least 1 cycle of consolidation chemotherapy and 198 patients did not receive any consolidation chemotherapy before alloSCT. To minimize inherent survival bias in favor of patients who underwent transplant long after achieving CR1, the study focused on 373 patients who underwent transplant within the median time frame between achievement of CR1 and alloSCT (3 months for patients who underwent alloSCT from matched siblings and 4 months for patients who underwent alloSCT from matched unrelated donors). In this subgroup, 151 patients did not receive any consolidation chemotherapy and 222 patients received ≥ 1 consolidation chemotherapy cycle. RESULTS: With a median follow-up of 36 months (range, 2 months-135 months), the 3-year cumulative recurrence incidence (RI) was not significantly different between the groups (36% ± 4% for the group treated without consolidation chemotherapy vs 38% ± 3% for patients who received consolidation chemotherapy; P = .89). In addition, leukemia-free survival was similar between the groups (45% ± 4% and 47% ± 3%, respectively; P = .41). Dose intensity of cytarabine given during consolidation chemotherapy appeared to have no influence on RI. On multivariate analysis, pretransplant consolidation (≥ 1 cycle vs 0 cycles) was found to have no significant impact on RI (hazards ratio, 1.29; 95% confidence interval, 0.84-1.97 [P = .24]) or leukemia-free survival (hazards ratio, 1.00; 95% confidence interval, 0.71-1.42 [P = .99]). CONCLUSIONS: The data from the current study suggest no apparent advantage for postremission consolidation chemotherapy before RIC alloSCT, provided a donor is readily available.

Addition of lenalidomide to intensive treatment in younger and middle-aged adults with newly diagnosed AML: the HOVON-SAKK-132 trial.

Lenalidomide, an antineoplastic and immunomodulatory drug, has therapeutic activity in acute myeloid leukemia (AML), but definitive studies about its therapeutic utility have been lacking. In a phase 3 study, we compared 2 induction regimens in newly diagnosed patients age 18 to 65 years with AML: idarubicine-cytarabine (cycle 1) and daunorubicin and intermediate-dose cytarabine (cycle 2) without or with lenalidomide (15 mg orally on days 1-21). One final consolidation cycle of chemotherapy or autologous stem cell transplantation (auto-SCT) or allogeneic SCT (allo-SCT) was provided according to a prognostic risk and minimal residual disease (MRD)-adapted approach. Event-free survival (EFS; primary end point) and other clinical end points were assessed. A second random assignment in patients in complete response or in complete response with incomplete hematologic recovery after cycle 3 or auto-SCT involved 6 cycles of maintenance with lenalidomide (10 mg on days 1-21) or observation. In all, 392 patients were randomly assigned to the control group, and 388 patients were randomly assigned to lenalidomide induction. At a median follow-up of 41 months, the study revealed no differences in outcome between the treatments (EFS, 44% ± 2% standard error and overall survival, 54% ± 2% at 4 years for both arms) although in an exploratory post hoc analysis, a lenalidomide benefit was suggested in SRSF2-mutant AML. In relation to the previous Dutch-Belgian Hemato-Oncology Cooperative Group and Swiss Group for Clinical Cancer Research (HOVON-SAKK) studies that used a similar 3-cycle regimen but did not pursue an MRD-guided approach, these survival estimates compare markedly more favorably. MRD status after cycle 2 lost prognostic value in intermediate-risk AML in the risk-adjusted treatment context. Maintenance with lenalidomide showed no apparent effect on relapse probability in 88 patients randomly assigned for this part of the study.

Graft-Versus-Leukemia Effect of Allogeneic Stem-Cell Transplantation and Minimal Residual Disease in Patients With Acute Myeloid Leukemia in First Complete Remission.

PURPOSE: The detection of minimal residual disease (MRD) in patients with acute myeloid leukemia (AML) may improve future risk-adapted treatment strategies. We assessed whether MRD-positive and MRD-negative patients with AML benefit differently from the graft-versus-leukemia effect of allogeneic hematopoietic stem-cell transplantation (alloHSCT). METHODS: A total of 1,511 patients were treated in subsequent Dutch-Belgian Hemato-Oncology Cooperative Group and the Swiss Group for Clinical Cancer Research AML trials, of whom 547 obtained a first complete remission, received postremission treatment (PRT), and had available flow cytometric MRD before PRT. MRD positivity was defined as more than 0.1% cells with a leukemia-associated immunophenotype within the WBC compartment. PRT consisted of alloHSCT (n = 282), conventional PRT by a third cycle of chemotherapy (n = 160), or autologous hematopoietic stem-cell transplantation (n = 105). RESULTS: MRD was positive in 129 patients (24%) after induction chemotherapy before proceeding to PRT. Overall survival and relapse-free survival were significantly better in patients without MRD before PRT compared with MRD-positive patients (65% ± 2% v 50% ± 5% at 4 years; P = .002; and 58% ± 3% v 38% ± 4%; P < .001, respectively), which was mainly because of a lower cumulative incidence of relapse (32% ± 2% compared with 54% ± 4%; P < .001, respectively). Multivariable analysis with adjustment for covariables showed that the incidence of relapse was significantly reduced after alloHSCT compared with chemotherapy or autologous hematopoietic stem cell transplantation (hazard ratio [HR], 0.36; P < .001), which was similarly exerted in both MRD-negative and MRD-positive patients (HR, 0.38; P < .001; and HR, 0.35; P < .001, respectively). CONCLUSION: The graft-versus-leukemia effect of alloHSCT is equally present in MRD-positive and MRD-negative patients, which advocates a personalized application of alloHSCT, taking into account the risk of relapse determined by AML risk group and MRD status, as well as the counterbalancing risk of nonrelapse mortality.

In vitro methods for generating CD8+ T-cell clones for immunotherapy from the naïve repertoire.

Innovations in gene discovery and the analysis of gene expression are facilitating the identification of a growing number of antigens that could potentially be targeted for immunotherapy of tumors. Methods to reliably generate antigen-specific T-cell responses in vitro would be useful not only to screen candidate antigens for immunogenicity prior to embarking on in vivo vaccination trials, but also to generate T-cell lines or clones that could be used directly for adoptive immunotherapy approaches. Although many techniques have proven successful for expanding ex vivo effector cells from antigen-specific memory CD8(+) cells that have been primed in vivo, methods to reliably generate high-avidity CTL clones from the naïve repertoire have not been well described. Various methods for the induction and expansion of antigen-specific CD8(+) CTL clones from healthy A2(+) donors were compared, using WT1 as a model tumor-associated antigen for which there is a low frequency of precursor T cells in naïve individuals. In contrast to the well-studied Melan-A/MART-1 (Melan-A) A2-restricted response, for which the CD8(+) T-cell precursor frequency in the naïve repertoire is unusually high, successful expansion of WT1-specific CD8(+) T cells appeared to be more dependent upon cell culture conditions. In particular, primary stimulation with autologous peptide-loaded monocyte-derived DC generated in 48 h (DC2d) was more effective in expanding WT1-reactive populations of CTL than stimulation with DC generated using the more standard week-long protocol (DC7d). Adding supplemental IL-7 2 to 3 days after initiation of a stimulation cycle expanded antigen-specific cells within CTL lines more efficiently than including the cytokine from the beginning of the cycle. Following primary stimulation with peptide-loaded mature DC, subsequent restimulation with peptide-loaded PBMC as the stimulators was more effective at expanding antigen-specific cells than repeated stimulation with mature DC. Using these techniques, high-avidity CTL clones specific for an A()0201-restricted epitope of WT1 have been generated from nearly all normal A2(+) donors tested. Such clones have been demonstrated to be capable of recognizing and lysing leukemic cells, and will soon be tested for therapeutic activity in clinical trials of adoptive immunotherapy in patients with relapsed leukemia after transplantation.

Blockade of PD-L1 (B7-H1) augments human tumor-specific T cell responses in vitro.

Human tumors frequently escape immune destruction, despite the presence of cytotoxic T cells (CTL) recognizing tumor-associated antigens (TAA). We have previously shown that programmed death ligand-1 (PD-L1), a recently identified ligand of the B7 superfamily, is expressed on murine tumors and can inhibit antitumor immune responses. To evaluate the clinical relevance of our animal model findings, we examined human tumors and tumor-specific T cells. We found PD-L1 to be constitutively expressed on human renal cell carcinoma (RCC) cell lines and upregulated on human melanoma cell lines upon exposure to interferon-gamma. Similarly, we found binding of anti-PD-L1 monoclonal antibody (mAb) on frozen sections from RCC and melanomas, but not on normal tissues. The corresponding inhibitory receptor of PD-L1, PD-1, revealed a higher expression on tumor-infiltrating lymphocytes than on peripheral blood lymphocytes (PBL) from melanoma patients upon specific antigen stimulation. Stimulation of PBL from healthy donors with peptide-loaded dendritic cells in the presence of anti-PD-L1 mAb altered neither the total T cell numbers after expansion, nor the percentage of peptide-specific CTL, when providing a T cell help by addition of cytokines. However, when stimulating TAA-specific CTL and T helper cells with Ag-pulsed dendritic cells in the absence of exogenous cytokines, PD-L1 blockade increased the cytokine production. Similar to the data achieved in the murine system, the blockade of PD-L1 on human tumors resulted in enhanced cytolytic activity of TAA-specific CTLs and cytokine production of TAA-specific T helper cells when interacting directly with the tumor. In summary, our data suggest that PD-L1/PD-1 interactions negatively regulate T cell effector functions predominantly in the absence of exogenous cytokine support, indicating an important role for this pathway in tumor evasion.