Treatment of acute myeloid leukaemia

Acute myeloid leukaemia is a heterogeneous disease that occurs in all age groups but peaks in older age at around a median of 69-70 years where it has a frequency of 13-15/100,00/annum. With the changing demographics, the number of cases will increase in line with the older population. As the only treatment with curative intent is intensive chemotherapy, this presents an immediate therapeutic challenge for the majority of the disease.

Distinct poor prognostic subgroups of acute myeloid leukaemia, FLT3-ITD and P-glycoprotein-positive, have contrasting levels of FOXO1

Regulation of ABCB1 (P-glycoprotein/Pgp) in AML was investigated. In a historical cohort with Pgp and transcriptional regulator expression profiling data available (n=141), FOXO1 correlated with Pgp protein expression. This was confirmed in an independent cohort (n=204). Down-regulation (siRNA) or hyperactivation (nicotinamide) of FOXO1 led to corresponding changes in Pgp. Low FOXO1 expression correlated with FLT3-ITDs (p<0.001) and siRNA inhibition of FLT3-ITD up-regulated FOXO1. As FOXO1 is a key growth regulator, it may underpin biological differences between Pgp-positive clones (low WBC and primary resistant disease) and clones with a FLT3-ITD (associated with a high WBC and early relapse).

Prognostic relevance of treatment response measured by flow cytometric residual disease detection in older patients with acute myeloid leukemia

PURPOSE

Older patients with acute myeloid leukemia (AML) have a high relapse rate after standard chemotherapy. We investigated whether measuring chemotherapy sensitivity by multiparameter flow cytometric minimal residual disease (MFC-MRD) detection has prognostic value in patients older than age 60 years or is simply a surrogate for known age-related risk factors.

PATIENT AND METHODS

Eight hundred ninety-two unselected patients treated intensively in the United Kingdom National Cancer Research Institute AML16 Trial were assessed prospectively for MFC-MRD during treatment. Eight hundred thirty-three patients had leukemia-associated immunophenotypes (LAIPs) identified by pretreatment screening. Four hundred twenty-seven patients entered complete remission (CR) after one or two courses (designated C1 and C2, respectively) and were MFC-MRD assessable by LAIP detection in CR bone marrow for at least one of these time points. MRD positivity was defined as residual disease detectable by LAIP.

RESULTS

MFC-MRD negativity, which was achieved in 51% of patients after C1 (n = 286) and 64% of patients after C2 (n = 279), conferred significantly better 3-year survival from CR (C1: 42% v 26% in MRD-positive patients, P < .001; C2: 38% v 18%, respectively; P < .001) and reduced relapse (C1: 71% v 83% in MRD-positive patients, P < .001; C2: 79% v 91%, respectively; P < .001), with higher risk of early relapse in MRD-positive patients (median time to relapse, 8.5 v 17.1 months, respectively). In multivariable analysis, MRD status at the post-C1 time point independently predicted survival, identifying a subgroup of intermediate-risk patients with particularly poor outcome. However, survival benefit from gemtuzumab ozogamicin was not associated with MFC-MRD chemotherapy sensitivity.

CONCLUSION

Early assessment of treatment response using flow cytometry provides powerful independent prognostic information in older adults with AML, lending support to the incorporation of MRD detection to refine risk stratification and inform clinical trial design in this challenging group of patients.

Optimization of Chemotherapy for Younger Patients With Acute Myeloid Leukemia: Results of the Medical Research Council AML15 Trial

Purpose

Treatment outcomes in younger patients with acute myeloid leukemia (AML) have improved, but optimization and new combinations are needed. We assess three combinations in induction and consolidation.

Patients and Methods

Younger untreated patients with AML (median age, 49 years; range, 0 to 73 years) were randomly allocated to two induction courses of daunorubicin and cytarabine (DA) with or without etoposide (ADE; n = 1983) or ADE versus fludarabine, cytarabine, granulocyte colony-stimulating factor, and idarubicin (FLAG-Ida; n = 1268), and to amsacrine, cytarabine, etoposide, and then mitoxantrone/cytarabine (MACE-MidAC) or high-dose cytarabine (n = 1,445) 3 g/m2 or 1.5 g/m2 (n = 657) in consolidation, and finally to a fifth course (cytarabine) or not (n = 227).

Results

Overall remission rates were similar for DA versus ADE (84% v 86%; P = .14) and ADE versus FLAG-Ida (86% v 85%; P = .7), with more course 1 remissions after FLAG-Ida (77%) reducing relapse (38% v 55%; P < .001) and improving relapse-free survival (45% v 34%; P = .01), overall and in subgroups, but with increased myelosuppression, reducing participation in the consolidation randomization. Overall outcomes were similar between MACE/MidAc and high-dose cytarabine (1.5/3.0 g/m2), but cytarabine required less supportive care. MACE/MidAc was superior for high-risk patients. A fifth course provided no benefit. The outcome for recipients of only two FLAG-Ida courses were not different from that with DA/ADE with consolidation.

Conclusion

FLAG-Ida is an effective remission induction treatment, with a high complete remission rate after course 1 and reduced relapse. Consolidation with MACE/MidAc is similar overall to high-dose cytarabine, but superior in high-risk patients. Cytarabine at 1.5 g/m2 is equivalent to a 3 g/m2 dose. A fifth course is unnecessary. In patients receiving FLAG-Ida (two courses) and cytarabine (two courses), 8-year survival was 63% for patients with intermediate-risk and 95% for those with favorable-risk disease.

GATA2 mutations in sporadic and familial acute myeloid leukaemia patients with CEBPA mutations

GATA2 mutations have recently been reported in acute myeloid leukaemia (AML) patients with CEBPA-double mutations. To explore their impact on this favourable-risk disease, we determined GATA2 status in 153 sporadic AML patients and three members of a germ-line CEBPA-mutant family at AML presentation. Overall, 27% (15/55) CEBPA-double, 16% (7/43) CEBPA-single and 0% (0/55) normal karyotype/CEBPA-wild-type patients were GATA2-mutant. All familial AML patients acquired both a second CEBPA and a GATA2 mutation. CEBPA and GATA2 mutant levels indicated that both mutations were likely to be early events in leukaemogenesis. GATA2 status did not impact on the favourable outcome of CEBPA-double/FLT3-inernal tandem duplication-negative patients.

Response rate and bridging to hematopoietic stem cell transplantation (HSCT) with quizartinib (AC220) in patients with FLT3-ITD positive or negative relapsed/refractory AML after second-line chemotherapy or previous bone marrow transplant

7012

Background: FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) in acute myeloid leukemia (AML) is associated with early relapse after chemotherapy and poor survival. Relapse after HSCT or failure of salvage chemotherapy in FLT3-ITD AML is rarely associated with subsequent HSCT or durable survival. Quizartinib, an oral FLT3 inhibitor, shows promising activity; a Ph 2 study (n=333) of quizartinib monotherapy (Levis et al, ASH 2012) reported that quizartinib often bridged patients (pts) to HSCT. Methods: 136 FLT3-ITD(+) and 40 FLT3-ITD(-) pts, relapsed/refractory after HSCT or 1-second line regimen, were included. The response category of composite complete remission (CRc) comprised complete remission [CR] + complete remission with incomplete platelet recovery [CRp] + complete remission with incomplete hematologic recovery [CRi]. Results: Quizartinib was discontinued for HSCT in 47/136 FLT3-ITD(+) pts (35%), with 44/47 having at least a PR (2 CRp, 24 CRi, 18 PR). Median overall survival (OS) was 41.5 wks for pts with CRc prior to HSCT and 29 wks for pts with PR. The 1y survival rate was 39% for both response groups. Pts with a CRc (n=36) or PR (n=20) but no HSCT, respectively, had a median OS of 24.5 and 20.9 wks and 1y survival rates of 25% and 5%. Of 27 pts with OS >52 wks, 17 (63%) had HSCT. Quizartinib was discontinued for HSCT in 14/40 FLT3-ITD(-) pts (35%), with 13/14 having at least a PR (1 CR, 1 CRp, 7 CRi, 4 PR). Median OS was not yet reached for pts with CRc, and was 40.7 wks for pts with PR. The 1y survival rate was 78% for pts with CRc and 50% for pts with PR. 8 of these 14 pts had detectable ITD mutation but the level was below the prespecified 10% cutoff. Conclusions: Of clinical significance in these heavily pretreated pts who had failed salvage chemotherapy or HSCT, approximately 1/3 were successfully bridged to potentially curative HSCT, with encouraging 1y survival rates. To extend the potential benefits of FLT3 inhibitor therapy in combination with allogeneic HSCT, studies of maintenance quizartinib to prevent relapse post HSCT are ongoing. Clinical trial information: NCT00989261.

Effect of quizartinib (AC220) on response rates and long-term survival in elderly patients with FLT3-ITD positive or negative relapsed/refractory acute myeloid leukemia

7021

Background: Advanced age and FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) in acute myeloid leukemia (AML) are associated with early relapse after standard chemotherapy and poor survival. Quizartinib (AC220), an oral FLT3 inhibitor active against ITD mutant and wild type FLT3, has shown promising activity in Ph 1 and 2 studies. Methods: Patients (pts) in a Ph 2 open label study (N = 333) of quizartinib monotherapy included 154 aged ≥60 y with known FLT3-ITD status and AML relapsed in <1 y or refractory to 1st line chemotherapy. Median duration of treatment was 14.2 wks (range 0.1–70.6 wks) for FLT3-ITD(+) pts and 9.5 wks (range 1.1–77.0 wks) for FLT3-ITD(-) pts. The composite complete remission (CRc) rate included complete remission (CR), complete remission with incomplete platelet recovery (CRp), and complete remission with incomplete hematologic recovery (CRi). Results: Of 110 FLT3-ITD(+) pts, 63 (57%) had a CRc (3 CR, 4 CRp, 56 CRi). Of 44 FLT3-ITD(-) pts, 16 (36%) had a CRc (2 CR, 1 CRp, 13 CRi). Median overall survival (OS) in FLT3-ITD(+) pts was 25.3 wks and 16/110 (15%) survived >52 wks. The median age of these pts surviving >52 wks was 69.5 y (range 66–80 y) and median OS was 76.3 wks (range 56.9–96.0 wks). All of these pts responded to quizartinib (2 CR, 2 CRp, 8 CRi, 4 partial remission [PR]). 2 pts were still alive >1 ½ y (OS 93.0 and 96.0 wks). Median OS in FLT3-ITD(-) pts was 19.1 wks and 6/44 FLT3-ITD(-) pts (14%) survived >52 wks. The median age of these pts was 70.0 y (range 65–77 y) and their median survival was 76.6 wks (range 54.9–98.4 wks). 5 of these pts responded to quizartinib (1 CR, 3 CRi, 1 PR). Conclusions: These data for an FLT3-targeted agent show encouraging survival in a subset of elderly pts with relapsed/refractory FLT3-ITD(+) AML. Clinical trial information: NCT00989261. [Table: see text]

Curability of patients with acute myeloid leukemia who did not undergo transplantation in first remission

PURPOSE

The aims of this study were to quantify the prospects of salvage treatment of patients who did not undergo transplantation in first complete remission (CR1) and to assess the contribution of allograft in second complete remission (CR2) with respect to major risk groups. This evaluation can inform the decision whether to offer a transplant in CR1.

PATIENTS AND METHODS

Of 8,909 patients who entered the Medical Research Council AML10, AML12, and AML15 trials, 1,271 of 3,919 patients age 16 to 49 years who did not receive a transplant in CR1 relapsed. Of these patients, 19% are alive beyond 5 years compared with 7% of patients who relapsed after an allograft in CR1. Overall survival and the contribution of a transplant in CR2 were assessed overall and by cytogenetic risk group by using Mantel-Byar analysis.

RESULTS

Fifty-five percent of patients who relapsed entered CR2. This percentage varied by risk group as follows: favorable (82%), intermediate (54%), adverse (27%), and unknown (53%), which resulted in 5-year survivals of 32%, 17%, 7%, and 23%, respectively. Sixty-seven percent of remitters received an allotransplant that delivered superior survival compared with patients who did not receive a stem-cell transplant (42% v 16%). A more-stringent assessment of a transplant by using delayed-entry (Mantel-Byar) analysis confirmed the benefit of transplant overall and within intermediate and adverse risk groups but not the favorable subgroup.

CONCLUSION

Successful salvage treatment of patients who do not undergo transplantation in CR1 and relapse can be achieved in 19% of patients, which is improved by a transplant except in favorable risk disease. This result suggests that, for intermediate-risk patients in particular, equivalent overall survival can be achieved by delaying transplantation until after relapse, which would require many fewer transplants.

The HSP90 inhibitor NVP-AUY922-AG inhibits the PI3K and IKK signalling pathways and synergizes with cytarabine in acute myeloid leukaemia cells

Heat shock protein 90 (HSP90; HSP90AA1) is a molecular chaperone involved in signalling pathways for cell proliferation, survival, and cellular adaptation. Inhibitors of HSP90 are being examined as anti-cancer agents, but the critical molecular mechanism(s) of their activity remains unresolved. HSP90 inhibition potentially facilitates the simultaneous targeting of multiple molecules within tumour cells and represents an attractive therapeutic proposition. Here, we investigated HSP90 as a molecular target for acute myeloid leukaemia (AML) using the novel HSP90 inhibitor NVP-AUY922-AG. NVP-AUY922-AG induced dose-dependent killing in myeloid cell lines and primary AML blasts. In primary blasts, cell death in response to NVP-AUY922-AG was seen at concentrations almost 2 logs lower than cytarabine (Ara-C) (50% lethal dose = 0·12 μ mol/l ± 0·28). NVP-AUY922-AG was significantly less toxic to normal bone marrow (P = 0·02). In vitro response to NVP-AUY922-AG did not correlate with response to Ara-C (r(2) = 0·0006). NVP-AUY922-AG was highly synergistic with Ara-C in cell lines and in 20/25 of the primary samples tested. NVP-AUY922-AG induced increases in HSP70 expression and depletion of total AKT, IKKα and IKKβ in cell lines and primary blasts. This study shows that the novel HSP90 inhibitor NVP-AUY922-AG has significant single agent activity in AML cells and is synergistic with Ara-C.

Prognostic and therapeutic relevance of c-FLIP in acute myeloid leukaemia

Chemoresistance is a major contributor to the aggressiveness of AML and is often due to insufficient apoptosis. The CFLAR gene is expressed as long and short splice forms encoding the anti-apoptotic proteins c-FLIP(L) and c-FLIP(S) (CFLAR(L) and CFLAR(S) , respectively) that play important roles in drug resistance. In univariate analyses of CFLAR mRNA expression in adult AML patients, those individuals with higher than median mRNA expression of the long splice form CFLAR(L) (but not the short splice form) had significantly lower 3 year overall survival (P = 0·04) compared to those with low expression. In cell line studies, simultaneous down-regulation of c-FLIP(L) and c-FLIP(S) proteins using siRNA induced apoptosis in U937 and NB-4 AML cells, but not K562 or OCI-AML3 cells. However, dual c-FLIP(L/S) downregulation sensitized all four cell lines to apoptosis induced by recombinant tumour necrosis factor-related apoptosis-inducing ligand (rTRAIL). Moreover, specific downregulation of c-FLIP(L) was found to recapitulate the phenotypic effects of dual c-FLIP(L/S) downregulation. The histone deacetylase (HDAC)1/2/3/6 inhibitor Vorinostat was found to potently down-regulate c-FLIP(L) expression by transcriptional and post-transcriptional mechanisms and to sensitize AML cells to rTRAIL. Further analyses using more selective HDAC inhibitors revealed that HDAC6 inhibition was not required for c-FLIP(L) down-regulation. These results suggest that c-FLIP(L) may have clinical relevance both as a prognostic biomarker and potential therapeutic target for HDAC inhibitors in AML although this requires further study.

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.

Inhibition of BET recruitment to chromatin as an effective treatment for MLL-fusion leukaemia

Recurrent chromosomal translocations involving the mixed lineage leukaemia (MLL) gene initiate aggressive forms of leukaemia, which are often refractory to conventional therapies. Many MLL-fusion partners are members of the super elongation complex (SEC), a critical regulator of transcriptional elongation, suggesting that aberrant control of this process has an important role in leukaemia induction. Here we use a global proteomic strategy to demonstrate that MLL fusions, as part of SEC and the polymerase-associated factor complex (PAFc), are associated with the BET family of acetyl-lysine recognizing, chromatin 'adaptor' proteins. These data provided the basis for therapeutic intervention in MLL-fusion leukaemia, via the displacement of the BET family of proteins from chromatin. We show that a novel small molecule inhibitor of the BET family, GSK1210151A (I-BET151), has profound efficacy against human and murine MLL-fusion leukaemic cell lines, through the induction of early cell cycle arrest and apoptosis. I-BET151 treatment in two human leukaemia cell lines with different MLL fusions alters the expression of a common set of genes whose function may account for these phenotypic changes. The mode of action of I-BET151 is, at least in part, due to the inhibition of transcription at key genes (BCL2, C-MYC and CDK6) through the displacement of BRD3/4, PAFc and SEC components from chromatin. In vivo studies indicate that I-BET151 has significant therapeutic value, providing survival benefit in two distinct mouse models of murine MLL-AF9 and human MLL-AF4 leukaemia. Finally, the efficacy of I-BET151 against human leukaemia stem cells is demonstrated, providing further evidence of its potent therapeutic potential. These findings establish the displacement of BET proteins from chromatin as a promising epigenetic therapy for these aggressive leukaemias.