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Acute Leukemias

A phase Ib GOELAMS study of the mTOR inhibitor RAD001 in association with chemotherapy for AML patients in first relapse

Abstract

The mTORC1 signaling pathway is constitutively activated in almost all acute myelogenous leukemia (AML) patients. We conducted a phase Ib trial combining RAD001 (everolimus), an allosteric inhibitor of mTORC1, and conventional chemotherapy, in AML patients under 65 years of age at first relapse (clinical trial NCT 01074086). Increasing doses of RAD001 from 10–70 mg were administrated orally on days 1 and 7 (d1 and d7) of a 3+7 daunorubicin+cytarabine conventional induction chemotherapy regimen. Twenty-eight patients were enrolled in this trial. The treatment was well tolerated with <10% toxicity, mainly involving the gastrointestinal tract and lungs. In this phase Ib trial, the RAD001 maximum tolerated dose was not reached at 70 mg. Sixty-eight percent of patients achieved CR, of which 14 received a double induction. Eight subsequently were intensified with allogeneic-stem cell transplant. Strong plasma inhibition of P-p70S6K was observed after RAD001 administration, still detectable at d7 (d7)at the 70 mg dosage. CR rates in patients with RAD001 areas under or above the curve median were 53% versus 85%. A 70 mg dose of RAD001 at d1 and d7 of an induction chemotherapy regimen for AML has acceptable toxicity and may improve treatment.

Introduction

Although intensive chemotherapy is effective in achieving complete remission (CR) of acute myelogenous leukemia (AML) in a majority of treated cases, most of these patients subsequently relapse and ultimately die of this disease.1 More than 30 years of clinical trials for combination chemotherapies have marginally improved the survival outcomes for AML, thus prompting the efforts to develop better targeted therapeutics. We and others have concentrated on identifying signaling inhibitors that would target AML cells without additional toxicity to normal hematopoietic cells. The mTORC1 signaling pathway, which positively regulates cell growth, is constitutively activated in the blast cells of nearly 100% of AML samples at diagnosis and relapse, and thus represents an attractive therapeutic target.2, 3, 4, 5, 6 mTORC1 activity can be specifically suppressed by rapamycin and its derivatives (also referred to as rapalogs) such as CCI-779 (temsirolimus) or RAD001 (everolimus). The RAD001 compound (Novartis) is an orally available ester derivative currently approved in Europe as an immunosuppressive agent to prevent rejection in adult cardiac and renal transplant recipients. Everolimus and temsirolimus have been approved by FDA for renal cancer and mantle cell lymphoma, respectively.

The anti-leukemic activity of both rapamycin and rapalogs has been tested in vitro in AML.3 Although these compounds alone induce only a low pro-apoptotic effect, it has been shown that rapamycin strongly increases the cytotoxicity of etoposide against primary AML blast cells in vitro.6 Moreover, in NOD-SCID mice, rapamycin enhances the etoposide-induced decrease in AML cell engraftment.6, 7 Clinical trials with either rapamycin8 or CCI-7799 combined with chemotherapy have therefore been conducted with encouraging clinical results.

In the present study, the anti-leukemic effect of RAD001 was tested for the first time in relapsed AML patients. The GOELAMS (Groupe Ouest Est d’Etude des Leucémies aiguës et Autres Maladies du Sang) conducted a phase Ib escalating dose study to determine the safety, tolerability and activity of RAD001 administered weekly for two doses on day 1 (d1) and d7, in association with classical chemotherapy (3+7). All patients included were <65 years old and had an AML relapse occurring more than 1 year after the first CR. Peripheral levels of RAD001 and inhibitory activity of the patient’s plasma on mTOR signaling were tested at regular time points after RAD001 administration.

Materials and methods

Overview

The study was registered at clinicaltrial.gov (NCT01074086) as a multicenter phase Ib trial aimed at evaluating the safety and efficacy of combining RAD001 with chemotherapy in relapsing AML patients. The study protocol was approved by the ethical review board of our institution. All patients provided written informed consent.

Patient selection

AML patients were recruited from the GOELAMS centers from March 2008 to May 2012. Eligible subjects were aged from 18–65 years and had an AML relapse following prior chemotherapy or allotransplantation, without the possibility of donor lymphocyte infusion or autotransplantation, at least 1 year after their first CR. We wanted to include relatively good prognosis patients for this trial designed to test the association of a 3+7 classical chemotherapy with a novel drug as frontline therapy. Untreated secondary leukemia is defined as AML arising after an antecedent of hematological disorder or following chemotherapy or radiation therapy; patients with an accelerated or myeloid blast phase chronic myelogenous leukemia or either promyelocytic, erythroid and megakaryoblastic leukemias were excluded.

All subjects were required to have an Eastern Cooperative Oncology Group performance status of 0–1. Baseline organ function studies were required: an ejection fraction >30%, creatinine 2.0 mg/dl, total bilirubin 1.5 mg/dl, hepatic transaminases 3 × upper level of normal, no uncontrolled infections, especially pulmonary infection, and no unstable baseline comorbidities that would jeopardize toxicity assessments. Owing to significant drug–drug interactions between RAD001 and systemic imidazole or triazole antifungals, these medications were prohibited for 1 week prior to and 1 week after enrollment. The research was approved by the Institutional Review Boards of the Cochin University Hospital, and the study was monitored by the Clinical Trials Safety Review and Monitoring Committee of the GOELAMS. Written informed consent was obtained from all subjects according to the Declaration of Helsinki.

Treatment plan

The treatment regimen (Figure 1), consisted of an oral dose of RAD001 (Everolimus novartis) on d1 followed by a second dose 7 days later, associated with a 3+7 chemotherapy (daunorubicin 60 mg/m2 per day on days 1–3, and cytarabine 200 mg/m2 per day on days 1–7 by continuous infusion). In the absence of dose-limiting toxicity (DLT), the RAD001 dosage was escalated over seven dose levels (DL) from 10–70 mg. The maximal DL of 70 mg per week was decided in agreement with previous data from phase I trials in solid tumors.10, 11 Groups of three patients were included at each DL. Dose escalation was achieved no sooner than 28 days following the last patient’s inclusion at the previous level (or 40 days in the case of double induction for the last patient included), and proceeded as long as no more than one patient per level experienced a DLT during that period. If two patients experienced a DLT, this DL was then expanded to three additional patients to collect additional toxicity data. If more than two patients experienced DLT at a treatment level, the maximum tolerated dose was considered to have been exceeded and the dose of RAD001 was de-escalated by one level. If there was no more DLT, dose escalation proceeded as long as no more than one patient per level experienced a DLT. Intrapatient dose escalation of RAD001 was not permitted. At d15, bone marrow (BM) examination was systematically performed and a second course of daunorubicin at 35 mg/m2 per day on d17 and d18, and cytarabine 1000 mg/m2 twice daily on d17–d20, in a 3-h perfusion without RAD001, was administered if there were >5% blast cells regardless the BM cellularity (as in the GOELAMS LAM 2001 trial and the German AML cooperative group (AMLCG) trials ).12, 13, 14 We avoided RAD001 at d15 of induction for two reasons: (1) we did not want to have a cumulative toxicity with high dose cytarabine, and (2) as the frequency of fungal infections increases with the duration of aplasia, we could not prohibit azoles after d15 of induction.

Figure 1
figure1

Protocol chart. BM, bone marrow.

Treatment supportive care

Subjects were treated in intensive care hematological units and central venous catheters were used in all cases. A low bacteria diet was provided during periods of neutropenia. All subjects received intravenous hydration and antiemetic agents during chemotherapy, and were given prevention against tumor lysis syndrome. Dexamethasone eye drops were provided during cytarabine administration as a keratitis prophylaxis. Prophylactic antibiotics and antifungals were not routinely given. Neutropenic fevers were treated in accordance with institutional guidelines. Azole antifungals (for example, voriconazole) were permitted only after the completion of all RAD001 doses, for example, after d7. Red blood cells were transfused for symptomatic anemia or a hemoglobin level of <8 g/dl. Single donor platelets were transfused for bleeding, disseminated intravascular coagulation or asymptomatic platelet counts of <10 × 109/l. All blood products were leukofiltered and irradiated.

Response criteria

CR was defined at d28 if the patient had received one induction, and at d40 for patients receiving a double induction as a normo-cellular BM aspirate containing <5% blast cells, with peripheral blood absolute neutrophil count >1 × 109/l, untransfused platelet count >100 × 109/l and no evidence of circulating or extra-medullar leukemic blasts. CR without platelet recovery met all criteria for CR except the platelet count, which failed to exceed 100 × 109/l. A partial remission met all criteria for CR, except that the BM blast percentage was between 5 and 15%. Progressive disease was defined as an increase of at least 15% in the absolute number of leukemic cells in peripheral blood or BM aspirate, the development of extra-medullar disease or other evidence of increased tumor burden.

Toxicity assessment

Toxicity was assessed using the Common Toxicity Criteria for Adverse Events, version 3.0. Hematological DLT was defined as grade 4 neutropenia and/or thrombopenia lasting >6 weeks in the absence of residual leukemia in a hypoplastic BM, starting at the time of induction or reinduction. Any grade 3 or greater non-hematological toxicity considered possibly, probably, or definitely related to RAD001 was taken into account as a DLT, excepting grade 3 nausea and vomiting responsive to medications; grade 3 tumor lysis syndrome; grade 3 or 4 metabolic perturbations attributed to antifungal medications or tumor lysis syndrome that corrected with intravenous or oral supplementation; grade 3 stomatitis that resolved within 7 days of medication; grade 3 or 4 hyperbilirubinemia or elevated transaminases that resolved to below grade 2 within 14 days.

Serum RAD001 levels and pharmacodynamic assessment

BM and peripheral blood samples were obtained after informed consent on d0. Plasma RAD001 levels were measured before RAD001 administration (H0: hour 0), then at H4, d1 and also at d7 H0 of chemotherapy, and assessed by high-pressure liquid chromatography in the clinical laboratories of the University Hospital of Limoges (Limoges, France).15 Areas under the curve (AUC) were thereby calculated. For patients receiving 50–70 mg DL, d3 and d5 samples were also collected.

Plasma inhibitory activity assay

Plasma samples were frozen for each patient to assess their inhibitory activity (PIA) upon mTORC1 signaling in the MOLM-14 cell line using an in vitro methodology similar to that used to assess anti-FLT3 (Fms-like tyrosine kinase-3) activity.16 Briefly, frozen plasma samples were thawed and clarified by centrifugation at 16 000 × g for 2 min. For each time point, 4 × 106 MOLM-14 cells were incubated with 1 ml plasma at 37 °C for 2 h. Activation of mTORC1 signaling was tested by the phosphorylation of p70S6K on T389 using western blotting as previously described.17 The primary antibodies used included T389 P-p70S6K, S473 P-Akt, Y694 P-Stat5, T202/Y204 P-ERK1/2 (Cell Signaling Technology, Danvers, MA, USA) and p70S6K (Santa Cruz Inc, Santa Cruz, CA, USA). For PIA calculation, the signal intensity of T389 P-p70S6K was quantified using Multigauge software from Fujifilm (Tokyo, Japan).

Results

Patient characteristics

Twenty-eight patients were enrolled in this trial (Table 1). The median delay of relapse after the first remission was 20 months (range 12–104). At inclusion, all patients had >20% BM blasts, except for one patient who had only 5% myeloblasts associated with an increase of molecular core-binding factor minimal residual disease. Karyotyping performed at relapse, using the SWOG criteria18 revealed three inv(16) good prognostic cytogenetic indicators, 19 patients with intermediate risk, including 18 with a normal karyotype and six poor risk cytogenetic indicators (Table 2). The FLT3 and NPM (nucleophosmin) mutational status of all patients was performed, and identified a FLT3–internal tandem duplication (ITD) mutation in four patients and NPM mutation in four patients. No FLT3–TKD was detected. No c-kit mutation was detected in core-binding factor+AML patients.

Table 1 Patient characteristics
Table 2 Karyotype details and outcome

Evaluation of RAD001 toxicity

All observed grade 1–4 adverse events are summarized in Table 3. Severe myelosuppression and neutropenic fevers typical of conventional chemotherapy induction regimens occurred in all patients. Documented infections occurred in 16 (57%) subjects. Four deaths occurred in the study after d40 of induction (19%). One of this death could be related to RAD001 administration (Fournier gangrene, infectious complication) and the other three patients died of AML progression. One death (fatal cerebral hemorrhage) occurred at d25, indirectly related to RAD001. No grade 3 or 4 toxicities were considered to be directly related to RAD001 therapy: one patient who developed renal failure at 20 mg DL had a previous history of immune-allergic renal insufficiency to teicoplanin and received a vancomycin over dosage concomitantly with RAD001. The cause of the episode of grade 3 whole-body erythema observed at a 20 mg DL could have been due to cytarabine. There were no hematological DLTs. Among the three patients having grade 3 mucositis, two had double induction therapy. Grade 3 mucositis appeared at d16 for the first patient and d20 for the second, one which resolved at the end of aplasia. As shown by the PIA assay and the previously published PK assays for RAD001, the half-life of RAD001 is about 30 h and the last dose of RAD001 was administered on d7 for each patient. Moreover, grade 3 mucositis are frequent with double induction chemotherapies and we set the rules that grade 3 mucositis, which resolved within 7 days of medication should not be considered as a toxicity related to RAD001 administration. Therefore, the central committee considered that these two grade 3 mucositis were not related to RAD001.

Table 3 All grade event toxicities (grade 3 and 4 toxicities are in brackets)

Serious adverse events were declared in nine patients in whom the infections were quite severe (Table 4; liver and lung mucormycosis along with an appendicitis mass; one interstitial pneumopathy with intra-alveolar hemorrhage and concomitant Stenotrophomonas maltophilia infection that resolved after broad spectrum antibiotics; one case of aspergillosis with transient ataxia, which was related to imipenem and which resolved within 15 days). At a 50 mg DL, one patient developed Fournier’s gangrene at d40 after double induction, leading to death, and this was considered as a DLT by the evaluation committee. Three more patients were included at a 50 mg DL with no more serious adverse event declared. The maximum tolerated dose was considered not to be attained even with the highest dose of RAD001 administered (70 mg) (Table 4), as there was only one DLT (fatal cerebral hemorrhage with platelets at 1 × 109/l; d25 of induction) out of seven patients considered to be potentially related to RAD001 by the evaluation committee, due to the intensity of thrombopenia that was refractory to platelet transfusions. At 70 mg RAD001, among the four patients who experienced pneumonias, one patient received a double induction. They all developed aspergillosis, which resolved under azoles, and one patient had a bronchoscopy that documented a concomitant aspergillosis and Pseudomonas maltophilia infection. Therefore, these pneumonias were considered as infectious and not related to RAD001. Based on the results of previous trials with RAD001 in solid tumors,10, 11 the maximal RAD001 dose tested in this trial had been set at 70 mg per week.

Table 4 Declared SAE (severe adverse events)

RAD001 drug levels and evidence of mTORC1 signal disruption

Paired baseline, H4, d1 and d7 pharmacokinetics of RAD001, and assessments of the PIA of RAD001 towards mTORC1 signaling in the MOLM-14 cell line could be evaluated in 26 of the 28 patients included in this study. The mean peak level at H4 was 52 nM (range 37.3–83 nM) for 10–40 mg RAD001 levels, and 101 nM (range 77–142 nM) for 50–70 mg RAD001 DL. At d3, the average steady state level was 24 nM (range 20–28 nM). At d5, it remained an average of 9 nM (range 7–11 nM). As expected, AUC data strongly correlated with the RAD001 administration DL (Figure 2), with a median AUC at 1.95 mg h/l obtained at around the 50 mg DL.

Figure 2
figure2

AUC measurements according to the RAD001 DL.

Representative western blotting analysis corresponding to the PIA assay of a patient receiving the 70 mg RAD001 dose (Figure 3a) clearly showed that P-p70S6K T389 is strongly inhibited when MOLM-14 cells are incubated with plasma obtained at H4, d1 and d3 after RAD001 administration, but reappeared from d5 onwards. The effect of RAD001 is specific to mTORC1 signaling as no inhibition of other activated signaling pathways such as ERK/MAPK, PI3K/Akt and Stat5 was observed even at high doses of RAD001 (Figure 3a). Western blotting quantification of the P-p70S6K signal from the MOLM-14 cells allowed us to calculate a mean PIA for each DL of RAD001 at different time after treatment initiation (Figure 3b). A near complete inhibition of the P-p70S6K T389 was thus observed in almost all samples obtained 4 h after RAD001 administration, regardless of the DL (mean PIA of 94±8%; Figure 3b), whereas the inhibition of p4E-BP1 on Ser65 was incomplete at H4 (Supplementary Figure 1). This strong inhibition was maintained at d1 and d3 at 50, 60 and 70 mg RAD001 DL, whereas it was reduced with lower doses of RAD001. Even at the highest dose of RAD001, T389 P-p70S6K was only modestly affected by the serum obtained on d5 and d7 (PIAs of 34±14% at d7 at the 70 mg dose of RAD001).

Figure 3
figure3

(a) Western blot analysis of a representative patient. One mililiter of plasma was sampled at different time points after RAD001 intake (CT before RAD001 d0, H4, d1, d3, d5 and d7 after first RAD001 intake), and incubated for 2 h at 37 °C with 4 × 106 MOLM-14 cells. Activation of mTORC1 signaling was then assessed by testing phosphorylation of p70S6K on T389 by western blot as previously described.17 Phosphorylation of Akt, Stat5 and ERK was also assessed using S473 P-Akt, Y694 P-Stat5 and T202/Y204 P-ERK1/2 antibodies. (b) Mean (topped by s.e.m.) T389 P-p70S6K inhibition (PIA) at various time points, and at each of the RAD001 DL administered. The PIA for a given plasma sample was calculated by expressing the density of its corresponding band as a percentage decrease from the density of the baseline band that was arbitrarily set at 100%. For example, if the densitometric analysis of a sample band revealed it to be 10% of the pretreatment/baseline sample, the mTORC1 PIA for that sample was 90%.

Clinical outcomes

Overall, 19 of the 28 patient subjects achieved CR (68%), among whom 14 patients required a second induction course at d15. The induction death rate was 3.5% (n=1). Beyond d40, excepting two patients who died from infectious complications (mucormycosis and Fournier gangrene), the other patients died of progression or relapse of AML. Eight patients underwent an allogeneic transplantation in second CR. Clinical responses occurred across all RAD001 DLs but interestingly, the AUC and RAD001 DL seemed to be correlated with the CR rates. Two groups of patients were established according to the median AUC (1.95 mg h/l, Table 5): 13 patients (group 1) with an AUC below the median (that is, treated with 10–40 mg of RAD001) and 15 patients (group 2) with an AUC above the median (that is, treated with 50–70 mg of RAD001). As shown in Table 5, group 2 patients had a better prognosis karyotype (P=0.03). The CR rate also tended to be higher in group 2 cases compared to group 1 patients (85 versus 53%, respectively, (P=0.07). It is noteworthy also that three out of four FLT3–ITD patients in group 2 achieved CR with RAD001 (one with a double induction). In multivariate analysis (including age, karyotype, AUC, delay of relapse, number of inductions and FLT3 mutation status), no variable was statistically significant for CR rate. The overall median survival was measured at 19.5 months (range 1.0–50.6, Supplementary Figure 2a) with a median follow-up of 12.8 months. Median progression free-survival was 24.8 months (range 1.3–41.6, Supplementary Figure 2b). There was no difference of overall survival between patients according to CR (Supplementary Figure 2c) and according to allotransplantation (Supplementary Figure 2d).

Table 5 Patient characteristics according to the AUC values

Discussion

The phase Ib study described here was designed to evaluate the tolerance and efficacy of the association of RAD001, an allosteric mTORC1 inhibitor, with a classical 3+7 chemotherapy induction regimen in younger AML patients (<65 years old) at relapse. The study design excluded poor prognosis cases (AML6, AML7, secondary AML after CML and MDS) and patients with refractory AML, and cases which had relapsed <1 year after CR. This was done to better appreciate the association of a 3+7 classical chemotherapy with a novel drug as a frontline therapy by choosing AML patients with a relatively good prognosis. This study results demonstrate the feasibility of combining RAD001, which specifically inhibits mTORC1 activity in leukemic cells, with highly myelosuppressive cytotoxic chemotherapy in AML patients. The association of doxorubicin and RAD001 is known to be at least additive, if not synergistic, and produce a higher level of antitumor activity than monotherapy in solid tumor xenografts, including colon, lung and cervical lesions.19 The weekly scheme for RAD001 administration was determined in late 2006 during phase I/II trials of this drug in solid tumors, taking into account that the half-life of RAD001 is quite long (about 30 h). Thereafter, a daily administration of RAD001 at lower doses of around 5–10 mg was used for solid tumors and showed a more sustained inhibition of T389 P-p70S6K. However, the administration of RAD001 was maintained on a weekly basis also in order to avoid cumulative toxicity with induction chemotherapy by a daily administration of the tested compound, especially pneumonitis that occurred at higher than the expected rates in the daily schedule compared to the weekly schedule.20

Among the toxicities observed, grade 3 infections were prominent and could be resolved with broad spectral antibiotherapy and antifungal therapy for two-thirds of the patients. However, as these AML patients are already immunosuppressed by cytotoxic chemotherapy, it is difficult to directly attribute these infectious side effects to RAD001. In previous studies, the infection rate ranged from 20–90% as a result of anthracycline+cytarabine or clofarabine induction.21, 22, 23, 24, 25, 26, 27, 28, 29 The addition of RAD001 to the 3+7 chemotherapy regimen did not obviously increase the non-hematological toxicity above levels historically observed with chemotherapy alone.26 Two patients had grade 3 mucositis, occurring at d16 for the first patient and d20 for the second one, which resolved at the end of aplasia. We set the rules that grade 3 mucositis that resolved within 7 days of medication should not be considered as a dose-limiting toxicity. Therefore, the central committee considered that these two grade 3 mucositis were not related to RAD001, which could have only increased the mucosal toxicity of chemotherapy. Neither hemorrhagic diarrhea nor interstitial non-infectious pneumopathy was observed in our patients, even though these are two classically reported complications of rapalogs. The induction death rate in our series was 3.5% (one patient who died of cerebral hemorrhage due to refractory thrombopenia), corresponding to the average usual range of induction death rates (5–10% in GOELAMS trials in de novo AML).12

Overall, the present trial shows that the maximum tolerated dose of RAD001 was not reached at a 70 mg of weekly dose.

The adequate and sustained inhibition of molecular targets in leukemic cells is a major objective for targeted therapies such as RAD001. Concerning FLT3–ITD inhibitors, Levis M et al.16 have observed that FLT3 inhibition by lestaurtinib correlates strongly with the CR rate. In the present study, the pharmacokinetics of RAD001 suggests that the weekly schedule we used was efficient in inhibiting mTORC1 assessed by the phosphorylation status of p70S6K until d3 at the 70 mg DL. The PIA assay results point to a daily administration of RAD001. However, at the time of the conception of the protocol, we decided a weekly dosage to avoid cumulative toxicity with chemotherapy. It is clear that our results strongly suggest that RAD001 should be administered daily or at least every 2 days in future trials.

In the literature and in our previous studies, it has been shown that almost all AML patients have a constitutive activation of the mTORC1 pathway, as assessed by phosphorylation of P70S6K and 4E-BP1 downstream of mTORC1.3, 4, 7, 17 The phosphorylation of pS6 downstream of P70S6K measured by flow cytometry on circulating blasts has been well described by Perl et al.30 However, pS6 is not a good surrogate marker of the activation of mTORC1 pathway, as ERK and PDK1 can also phosphorylate pS6. There is also a recent paper suggesting that the eIF4E/4EBP ratio may predict the efficacy of mTOR-targeted therapies better than their individual protein levels or solely their phosphorylation status.31

The CR rate obtained with chemotherapy+RAD001 in this study seems promising for a population of AML patients who have relapsed beyond 1 year after the first CR. Historically, classical chemotherapies allow remission rates of around 50% (late relapse: CR range, 4–83%; early relapse, range 18–41%).32, 33, 34, 35 The CR rate of 68% obtained in our cohort allowed eight patients to proceed to allotransplantation, and hopefully benefit from a longer overall survival. Furthermore, the CR rate reached 85% in patients who received a 50 mg or higher dose of RAD001, independently of the FLT3 mutation status, karyotype and delay of relapse. These results are particularly promising but further randomized trials testing chemotherapy alone versus chemotherapy+RAD001 at a 70 mg dose twice weekly will be necessary to validate these encouraging results. Interestingly, it is noteworthy that three out of four FLT3–ITD patients obtained CR. Even though the population sizes are very limited, these results are promising when compared to other studies of FLT3-targeted therapy in association with chemotherapy, where the CR rate was around 50% in relapsing FLT3-mutated AML patients.36 These results therefore collectively suggest that FLT3–ITD patients may be more sensitive to mTORC1 inhibition, perhaps because of the role of FLT3–ITD in mTORC1 overactivation as previously suggested.37

Another point of discussion in the future will concern the role of the second generation of mTOR kinase inhibitors, the TORKinhibs, which directly target the kinase activity of mTOR and have the potential to inhibit the activity of both mTORC1 and mTORC2. TORKinhibs or new dual PI3K/mTOR inhibitors have demonstrated increased antileukemic activity in AML compared with rapalogs in vitro with a more complete inhibition of phosphorylation of 4EBP1 on Ser65,17, 38, 39 without affecting normal CD34+hematopoietic cells. Only well-conducted clinical trials will help to definitely evaluate the suggested superiority of TORKinhibs over rapalogs in association with chemotherapy for AML.

Overall, the results of the present trial show that a weekly dose of RAD001 at 70 mg in association with high-dose chemotherapy is safe in late-relapsing young AML patients. It also provides a proof-of-concept that targeting the mTORC1 pathway in AML is possible and may be clinically relevant. The CR rate we observed with the association of RAD001 to chemotherapy was quite high and may be correlated with RAD001 DL higher than 50 mg per week. Confirmation of these first results will require an extended phase II study and then a formal randomized prospective phase III trial.

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Acknowledgements

We thank all the GOELAMS investigators, the molecular biologists, Laurence Lode, Olivier Kosmider, Odile Blanchet, Marie–Pierre Gaub and clinical trial office staff in Tours and Novartis.

Author contributions

Conception and design: Sophie Park, Didier Bouscary, Christian Recher, Annabelle Merlat. Administrative support: Roselyne Delepine, François Dreyfus, Catherine Lacombe and Patrick Mayeux. Provision of study materials or patients: Sophie Park, Christian Recher, Norbert Vey, Thomas Prebet, Patrice Chevallier, Jean-Yves Cahn, Thibault Leguay, Pierre Boris, Francis Witz, Thierry Lamy, Jérôme Tamburini, Annabelle Merlat, Marie-Christine Béné, Norbert Ifrah and Didier Bouscary. Collection and assembly of data: Roselyne Delepine. Data analysis and interpretation: Sophie Park, Nicolas Chapuis, Franck Saint Marcoux, Christian Recher, Norbert Vey, Thomas Prebet, Patrice Chevallier,Jean-Yves Cahn, Thibault Leguay, Pierre Boris, Francis Witz, Thierry Lamy, Annabelle Merlat, Roselyne Delepine, Francois Dreyfus, Marie-Christine Béné, Norbert Ifrah and Didier Bouscary.

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Correspondence to S Park.

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Competing interests

AM is employed at BU oncologie Novartis Pharma SAS, Novartis, Rueil-Malmaison, France. The rest of the authors declare no conflict of interest.

Additional information

Oral communication at the 53th Annual Meeting of the American Society of Hematology, San Diego, 2011, Blood, 118: Abstract 945. Oral communication at the Annual Meeting of the Société Française d’Hématologie, Paris, 2012. Oral communication at the Annual Meeting of the European Society of Hematology, Amsterdam, 2012, Haematologica, 2012, 97 s1: 469, Abstract 1136.

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Park, S., Chapuis, N., Saint Marcoux, F. et al. A phase Ib GOELAMS study of the mTOR inhibitor RAD001 in association with chemotherapy for AML patients in first relapse. Leukemia 27, 1479–1486 (2013). https://doi.org/10.1038/leu.2013.17

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Keywords

  • AML
  • relapse
  • RAD001
  • mTORC1

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