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Decitabine and Sorafenib Therapy in FLT-3 ITD-Mutant Acute Myeloid Leukemia
SOHO Supplement 2015
Decitabine and Sorafenib Therapy in FLT-3 ITD-Mutant Acute Myeloid Leukemia Monica R. Muppidi,1 Scott Portwood,1 Elizabeth A. Griffiths,1 James E. Thompson,1 Laurie A. Ford,1 Craig W. Freyer,2 Meir Wetzler,1 Eunice S. Wang1 Abstract Patients with FLT-3 ITD mutant AML have poor outcomes following standard chemotherapy. We show preclinical data demonstrating the in vitro synergistic effects of the FLT-3 inhibitor, sorafenib, and the hypomethylating agent, decitabine, on FLT-3 mutant AML cells. Treatment of 6 FLT-3 ITD mutant patients with decitabine and sorafenib resulted in overall responses in 5 patients (83%) and prolonged median survival. Background: Acute myeloid leukemia (AML) characterized by Feline McDonough Sarcoma-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes. Treatment options are limited, because these mutations confer resistance to conventional chemotherapy. FLT-3 inhibitors such as sorafenib have been studied as a single agent and in combination with conventional chemotherapy or azacytidine with fair responses. Patients and Methods: Here we describe our preclinical and clinical experience with the combination of the DNA hypomethylating agent, decitabine and sorafenib for the treatment of FLT-3 ITD-mutant AML. Results: In vitro treatment of the human FLT-3 ITD-mutant AML cell line, MV4-11, with both drugs significantly improved growth inhibition over single-agent therapy and resulted in synergistic antitumor effects (combination index < 1). A case series of 6 patients treated with off protocol combination of decitabine and sorafenib demonstrated overall responses in 5 patients (83%) with a median survival of 155 days. Four of the 5 patients (80%) with relapsed/refractory AML achieved complete responses with incomplete count recovery. The combination was also well tolerated. Conclusion: Further investigation is warranted to confirm these responses. Clinical Lymphoma, Myeloma & Leukemia, Vol. 15, No. S1, S73-9 ª 2015 Elsevier Inc. All rights reserved. Keywords: Combination therapy, FLT-3 inhibitors, Hypomethylating agents, Targeted agents
Introduction Patients with acute myeloid leukemia (AML) characterized by Feline McDonough Sarcoma-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes, especially in the relapsed and refractory setting.1-4 Because these mutations appear to confer resistance to conventional chemotherapy, treatment options are limited. Because of their dismal prognosis, patients with FLT-3emutant AML are usually offered intensive induction chemotherapy followed by allogeneic stem cell transplantation. Many patients, however, particularly those of older age, are not candidates 1
Leukemia Service, Department of Medicine Department of Pharmacy Roswell Park Cancer Institute, Buffalo, NY 2
Submitted: Dec 11, 2014; Revised: Jan 5, 2015; Accepted: Feb 26, 2015; Epub: Mar 6, 2015 Address for correspondence: Monica R. Muppidi, MD, Department of Medicine, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263 Fax: 716-845-8741; e-mail contact: [email protected]
2152-2650/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clml.2015.02.033
for intensive chemotherapy or transplantation, especially in the relapsed setting.4 Numerous small molecule FLT-3 inhibitors are in active clinical evaluation for the treatment of FLT-3emutant AML. Targeted FLT-3 inhibitors have been shown to induce apoptosis of peripheral blasts and cause differentiation of immature bone marrow blasts.5 Sorafenib is a multikinase inhibitor with known activity against FLT-3 ITD-mutated AML cells in vitro and in vivo.6 This agent has also been tested in clinical trials as a single agent and in combination with cytarabine and/or anthracycline chemotherapy for AML patients with FLT-3 mutant and wild type disease. Although some patients have achieved clinical remissions, responses typically are short-lived because of the rapid development of resistance.7 The underlying mechanisms of sorafenib resistance include inadequate target inhibition, the development of FLT-3 tyrosine kinase domain mutations, and other mechanisms.8 For these reasons, the combination of sorafenib with other antileukemic agents might demonstrate improved efficacy.
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Decitabine and Sorafenib in FLT-3 ITD-Mutant AML Decitabine is a hypomethylating agent, which has increasingly been used for the treatment of older patients with AML, particularly those individuals considered unfit for standard induction chemotherapy. Previous studies have demonstrated that overall survival after decitabine induction is at least equivalent to that achieved with best supportive care or low-dose cytarabine for AML patients.9 Recent retrospective analyses have also suggested equivalent outcomes for decitabine compared with intensive chemotherapy, particularly for older AML patients with lower white blood cell
(WBC) count at presentation and poor performance status.10,11 Although decitabine has been administered in 3- and 5-day regimens for AML treatment, phase II results have demonstrated the highest response rates after a 10-day decitabine regimen.12
Patients and Methods We hypothesized that the combination of sorafenib with decitabine would improve clinical responses in patients with FLT-3 ITD mutant AML by inhibiting complementary biological pathways
Figure 1 Inhibition of MV4-11 Cell Growth by Decitabine (Dec) and Sorafenib (Sor). Representative Results of 3-(4, 5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium bromide Colorimetric Assays Plated in Triplicate With Human FMS-Like Tyrosine Kinase-3 Internal Tandem Duplication Mutant Acute Myeloid Leukemia Cells (MV4-11) and Treated With Decitabine (D), Sorafenib (S), and the Combination of the 2 Drugs (D D S) for 72 Hours Followed by Cell Viability Detection. Data Are Depicted as (A) Bar Graphs Showing Mean ± SD, (B) Dose Effect Response With Doses Ranging From 0 to 300 mM, and (C) Determination of Combination Index of the 2 Drugs Showing Synergy (Combination Index, < 1) for All Tested Combinations of the 2 Drugs (Compusyn Software, Paramus, NJ)
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Abbreviation: Fa ¼ fraction affected.
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Monica R. Muppidi et al Figure 1 Continued
promoting leukemia growth and limiting the development of resistance. To test this, we performed in vitro assays to assess the effects of decitabine, sorafenib, and combination therapy on a FLT-3 mutant human AML cell line. We also treated 6 adult patients with confirmed FLT-3 ITD mutant AML at our comprehensive cancer center with decitabine and sorafenib (DS) combination therapy.
Results In Vitro Assays The human AML cell line, MV4-11, which expresses FLT-3 ITD mutations with constitutively phosphorylated receptor protein, was cultured in the presence of decitabine (1, 10, and 100 mM), sorafenib (1, 10, and 100 mM) (LC Laboratories, Woburn, MA), or both drugs.13 Cell viability after 72 hours was assessed in triplicate wells using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay (Thiazolyl Blue Tetrazolium Blue, Sigma) according to manufacturer instructions. Absorbance (570/690 nm) was measured using a Biotek Synergy HT multitask plate reader using KC4 software (Version 3.4) (BioTek, Winooski, VT). Percent inhibition of growth was normalized to untreated control samples. Improved inhibition of MV4-11 growth was consistently observed after exposure to the combination versus to each single-agent treatment (Figure 1A). The effects of both drugs were analyzed using Compusyn software (Version 1.0) (ComboSyn Inc, Paramus, NJ). Dose response curves and determination of combination index (CI) are shown, with the latter demonstrating synergy (CI < 1) for all combination regimens tested (Figure 1).14
Patients From 2011 to the present, 6 patients with confirmed FLT-3 ITD-mutant AML received off protocol DS therapy at our institute. Although off protocol, all individuals provided written informed consent for treatment with these 2 agents. This
retrospective review of available clinical, pathological, and treatment information on these patients was approved by our institutional review board. The mean age of patients was 56 years (range, 33-70). Two-thirds (4/6) were women. Five of the 6 patients had relapsed or refractory AML, and 1 patient had newly diagnosed AML (patient 4). All patients had AML characterized by normal karyotype and FLT-3 ITD mutations, with 5 of the 6 cases also containing nucleophosmin (NPM-1) mutations. Half (50%) of the patients had received 2 or more previous therapies. Two patients had undergone previous allogeneic stem cell transplant. All patients received at least 1 cycle (28 days) of concurrent intravenous decitabine 20 mg/m2 daily and sorafenib 200 or 400 mg orally twice a day. Five of the 6 patients received decitabine induction for 10 days for the first 1 to 2 cycles. Two of these patients achieved a morphological response and received additional 5day cycles of decitabine as consolidation therapy. One patient (patient 4) with treatment-naive de novo FLT-3emutant AML received 5-day DS for consolidation therapy after induction with cytarabine and daunorubicin (“7þ3” regimen) (Table 1). All patients received standard neutropenic prophylaxis with antimicrobial agents. The overall response rate was 83%, including 1 complete remission (CR; 16%), and 4 (66%) achieved a CR with incomplete count recovery (CRi). Eighty percent (4/5) of patients with relapsed refractory AML attained CRi after 1 to 2 cycles. Three patients (patients 1, 2, and 5) had FLT-3 ITD allele ratios measured before and after DS therapy. The allele ratio decreased in 2 patients (patients 1 and 2) after DS therapy, correlating with achievement of CRi. Two patients (patients 1 and 5) underwent subsequent allogeneic stem cell transplantation. The median overall survival was 155 days (range, 59-440) from the initiation of DS to death from any cause or last known follow-up (Figure 2). The most common complications reported with DS therapy were neutropenic infections (2/6 patients), specifically typhlitis,
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N 59 CRi 2 Relapsed 58 6
F
2
1 2 F 33 5
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Abbreviations: Allo HSCT ¼ allogeneic hematopoietic stem cell transplant; AML ¼ acute myeloid leukemia; CHF ¼ congestive heart failure; CRi ¼ complete remission with incomplete count recovery; DS ¼ decitabine and sorafenib combination therapy; ECOG ¼ Eastern Cooperative Oncology Group performance status; F ¼ female; M ¼ male; N ¼ no; NR ¼ no response; Y ¼ yes.
Dead
Alive
Dose reduced because of diarrhea None Diarrhea, transaminitis CHF Y 440
None N 275 1 1 59 4
M
Treatment-naive de novo Relapsed
CR
Sepsis, mucormycosis N 127 CRi 64 3
M
3 1 Relapsed
NR
Alive
Alive
Dead Alive
None Held because of reduced ECOG Discontinued because of infection None Transaminitis Neutropenic fever Y N 142 168 CRi CRi 1 4 3 1 Relapsed Relapsed F F 54 70 1 2
Response DS Cycles, n Previous AML Diagnosis Therapies, n Sex Age, Years Patient
Table 1 Characteristics and Outcomes of FLT-3 ITD Mutant AML Patients Treated With DS
Overall Survival, Days
Follow-Up Allo HSCT
Side Effects
Dose Modifications
Current Status (Alive/Dead)
Decitabine and Sorafenib in FLT-3 ITD-Mutant AML pneumonia and cellulitis, and grade 1-2 transaminitis (2/6 patients). One patient had invasive mucormycosis (patient 3). Although 1 patient (patient 5) developed diarrhea, the cause was multifactorial including possible gastrointestinal graft versus host disease (GVHD). Generalized fatigue and decline in Eastern Cooperative Oncology Group (ECOG) performance status was observed in 2 individuals (patients 2 and 5) but might have also been from other causes such as deconditioning because of prolonged hospitalization and underlying relapsed disease. Heart failure was noted in 1 patient with extensive previous anthracycline exposure (patient 6). Reasons for discontinuation of DS therapy were diverse. Decitabine was stopped in 1 patient because of diagnosis of mucormycosis. Sorafenib was stopped at the beginning of cycle 3 in 1 patient (patient 2) because of decline in performance status and was dose reduced in another (patient 5) because of diarrhea (Table 1).
Patient 1 A 54-year-old Caucasian woman presented to an outside facility in February 2011 with a WBC count of 160,000/mL with 90% peripheral blasts. Bone marrow biopsy revealed normal karyotype AML (myelomonocytic leukemia) with 70% blasts, NPM-1, and FLT-3 ITD mutations. She underwent induction treatment with daunorubicin and cytarabine followed by 1 cycle of high-dose cytarabine consolidation (HiDAC) therapy. She was referred for peripheral blood stem cell transplant at that time. However, she had relapsed disease within 2 months. She received reinduction chemotherapy with etoposide and mitoxantrone without response. She was then referred to our institute and was enrolled in a clinical protocol with intermediate-dose cytarabine and lenalidomide. A follow-up bone marrow biopsy demonstrated refractory AML with 75% blasts, normal cytogenetics, and NPM-1 and FLT-3 ITD mutations with a FLT-3 ITD/FLT-3 wild type allele ratio of 6.56. Her ECOG performance status was 1. She initiated therapy with decitabine 20 mg/m2 intravenously (I.V.) daily for 10 days combined with sorafenib 400 mg orally twice daily for 28 days. She developed vitreous hemorrhage secondary to low platelet count and Grade 1 transaminitis, both of which resolved spontaneously. No dose modification was required. A day 30 bone marrow biopsy showed a CRi with an FLT-3 ITD allele ratio of 1.16. She subsequently underwent an 8/10 mismatched unrelated allogeneic peripheral blood stem cell transplant. Unfortunately, at day > 85, a bone marrow biopsy showed relapsed disease. The patient died from complications of GVHD.
Patient 2 A 70-year-old Caucasian woman presented in February 2014 with severe anemia and a WBC count of 92,000 with 80% blasts. Bone marrow biopsy revealed AML with monocytic differentiation and 61% blasts, normal cytogenetics, and NPM-1 and FLT-3 ITD mutations. She initiated induction treatment with cytarabine and daunorubicin. Her course was complicated by myocardial infarction, acute gastrointestinal bleeding, bilateral pneumonia, urinary tract infection, renal failure, and Clostridium difficile infection. She had a prolonged course in the intensive care unit leading to debilitation. On stabilization of her acute conditions, the patient opted for no further therapy and was discharged for comprehensive physical therapy and occupational therapy rehabilitation. Her
Monica R. Muppidi et al Figure 2 Overall Survival of FMS-Like Tyrosine Kinase-3 Internal Tandem Duplication Mutant Acute Myeloid Leukemia Patients From Initiation of Decitabine and Sorafenib (DS) Therapy
performance status was 1. He was initiated on off-protocol decitabine for 10 days along with sorafenib 200 mg once daily for 28 days. Sorafenib was initiated at a low dose because of concern for gastrointestinal toxicity. It was increased to 200 mg twice daily in cycle 2. A bone marrow biopsy after 2 cycles showed morphological CRi with continued presence of FLT-3 ITD mutation with an allele ratio of 0.03. Therapy was complicated by bilateral pneumonia after cycle 1 and neutropenic fever after cycle 2. During cycle 3, he developed mucormycosis of the hard palate despite antifungal azole prophylaxis and was treated with intravenous antifungal medications. The patient declined any aggressive surgical debridement and opted to proceed with conservative therapy. A decision was made to hold decitabine in view of mucormycosis. The patient continues to receive sorafenib 200 mg twice daily and has achieved complete count recovery with supportive care and antifungal treatment.
Patient 4
peripheral blood counts did not show any evidence of leukemia. In April 2014, she presented from the rehabilitation center with a WBC count of 40,000 with 53% blasts consistent with relapse. Molecular testing on the peripheral blood showed FLT-3 ITD mutation (allele ratio, 0.91) and NPM-1 mutations. Her ECOG performance status was 2. The patient was initiated on off-protocol decitabine 20 mg/m2 I.V. daily for 10 days in addition to sorafenib 400 mg orally twice a day for 28-day cycles. She tolerated cycle 1 of therapy well. Cycle 2 of therapy was complicated by recurrent Clostridium difficile infection, typhilitis, neutropenic sepsis with Stenotrophomonas pneumonia, and cellulitis of her upper extremity. Sorafenib was held for a brief period because of typhilitis and reinitiated at clinical improvement of symptoms. A bone marrow biopsy at the end of cycle 2 showed morphological CRi, normal cytogenetics, and FLT-3 ITD mutation with an allele ratio of 0.36. Because of extensive hospitalization and complications, the patient’s performance status declined. Cycle 3 was delayed by 5 weeks. She then received consolidation therapy with decitabine 20 mg/m2 for 5 days in the setting of remission. Sorafenib was held because of a decline in performance status. The patient was admitted for neutropenic fever with cellulitis. Despite receiving a fourth cycle of 5-day decitabine consolidation, she was found to have relapsed disease with 86% peripheral blood blasts. She was subsequently enrolled in a phase 1 trial of a novel FLT-3 inhibitor and continues to receive treatment.
Patient 3 A 64-year-old Caucasian man presented in June 2013 with a WBC count of 69,000/mL and 70% peripheral blasts. Bone marrow showed AML with normal cytogenetics, NPM-1 and FLT3 ITD mutations with a FLT-3 allele ratio of 0.28. The patient received cytarabine and daunorubicin induction followed by 2 courses of HiDAC consolidation. Further chemotherapy was held because of development of sepsis. In May 2014, the patient presented with relapsed normal karyotype AML with 68% blasts and FLT-3 ITD mutation (allele ratio of 4.19). The patient’s ECOG
A 59-year-old Caucasian man presented in October 2013 with severe anemia, thrombocytopenia, and 82% peripheral blasts. A bone marrow biopsy showed AML with normal cytogenetics characterized by FLT-3 ITD without NPM-1 mutations. The patient was initiated with protocol therapy with decitabine for 5 days followed by cytarabine and daunorubicin induction therapy. His course was complicated by severe bilateral multifocal pneumonia leading to prolonged intensive care support. Bone marrow biopsy on day 44 showed CRi. HiDAC consolidation therapy was deferred because of a poor ECOG performance status of 3 and he was initiated on therapy with decitabine 20 mg/m2 for 5 days along with sorafenib 400 mg orally twice daily. A bone marrow biopsy after cycle 1 of DS therapy confirmed continued CRi. Although he tolerated the therapy well without any side effects, he was subsequently transferred to a long-term rehabilitation facility. Because of transportation difficulties, no further treatment with decitabine was given. He remains in CR with complete count recovery with sorafenib 400 mg twice daily treatment.
Patient 5 A 33-year-old Caucasian woman was diagnosed in October 2011 with normal karyotype AML characterized by FLT-3 ITD and NPM-1 mutations. She received induction chemotherapy with cytarabine and idarubicin followed by 2 cycles of HiDAC consolidation therapy. She then underwent unrelated donor allogeneic peripheral blood stem cell transplant in February 2012. In July 2013, she presented with overt relapsed disease with a WBC count of 144,000/mL, acute renal failure, malignant pleural effusions, and central nervous system involvement. She received intrathecal methotrexate and reinduction therapy with cytarabine and daunorubicin followed by single-agent sorafenib. Unfortunately her disease was refractory with evidence of increasing peripheral blasts and a FLT-3 allele ratio of 2.54. Her ECOG performance status was 2. She initiated decitabine 20 mg/m2 for 10 days along with sorafenib 400 mg orally twice daily. Sorafenib was held for 10 days because of Grade 2 transaminitis and diarrhea. Sorafenib was then reinitiated at a lower dose of 200 mg orally once daily. Repeat bone marrow biopsy after 1 cycle of DS showed 41% AML blasts with NPM-1 and FLT-3 ITD mutations (allele ratio of 9.54). She received
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Decitabine and Sorafenib in FLT-3 ITD-Mutant AML high-dose cytarabine and mitoxantrone reinduction therapy followed by a second allogeneic peripheral stem cell transplant and remains in continued remission.
Patient 6 A 58-year-old Caucasian woman was diagnosed in October 2011 with AML characterized by normal cytogenetics, NPM-1 and FLT-3 ITD mutations. She underwent induction therapy with cytarabine and daunorubicin followed by 3 cycles of HiDAC consolidation therapy. Unfortunately she presented with relapsed AML in April 2012. She received reinduction therapy with cytarabine, idarubicin, and pravastatin on protocol followed by matched unrelated allogeneic peripheral stem cell transplant. In October 2012 she was again found to have relapsed FLT-3 ITD mutant disease and was initiated on decitabine for 10 days and sorafenib 400 mg orally twice daily. The patient completed 2 cycles of DS complicated by bacteremia, GVHD (liver, lung), and congestive heart failure. A limited cardiac workup demonstrated nonischemic cardiomyopathy thought to be likely multifactorial due to previous extensive anthracycline therapy and sorafenib. The patient died after a prolonged hospitalization. Bone marrow biopsy at time of autopsy demonstrated no morphological evidence of AML consistent with CRi.
Discussion
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Internal tandem duplication mutations of the FLT-3 gene are seen in approximately 23% of all AML patients.15 These mutations confer a poor prognosis in terms of disease outcomes in all age groups, including older patients, with a median overall survival of < 1 year and high relapse rates.1-4 Sorafenib is a small molecule inhibitor of multiple tyrosine kinases, including vascular endothelial growth factor, platelet derived growth factor, and FLT-3 receptors. Preclinical studies have demonstrated that sorafenib effectively induces cell cycle arrest and apoptosis in blasts containing FLT-3 ITD mutations.6 In an open-label single-arm study, a large number of patients obtained complete or near complete elimination of bone marrow blasts after sorafenib therapy along with myeloid differentiation; however, these responses were not sustained with most of the patients with disease relapse after 72 days.16 The reasons for early relapses in FLT-3 mutant AML patients are under active investigation. Although specific tyrosine kinase domain mutations in the FLT-3 receptor are known to confer sorafenib resistance, increased levels of the FLT-3 ligand (FL), a hematopoietic growth factor predominately synthesized by bone marrow microvascular endothelial cells, T cells, and leukemia cells, might also be responsible.17-19 High FL levels induced under stem cell-depleted conditions (ie, after induction and consolidation chemotherapy) or at the time of disease relapse can bind to FLT-3emutated receptors on AML cells to fuel AML proliferation and impede the potency of FLT-3 inhibitors.20,21 Multiple clinical studies to evaluate sorafenib in combination with conventional chemotherapy for the treatment of FLT-3emutant AML have had variable results. A randomized placebo-controlled study examining the addition of sorafenib to intensive chemotherapy in elderly patients found no survival benefit and increased toxicity with the combined drugs.22 Treatment with low-dose cytarabine and sorafenib therapy in other older patients was also largely ineffective.23
Clinical Lymphoma, Myeloma & Leukemia June 2015
Although sorafenib combined with cytarabine and idarubicin induction resulted in high response rates, after a median follow up of 9 months, more than half of the patients had disease relapse.24 These findings support the need for novel regimens of a combination of sorafenib with other antileukemic therapies to optimize outcomes. Decitabine represents an attractive agent for combination studies with sorafenib (and/or other FLT-3 inhibitors) because of its relative tolerability and overall clinical response rates, particularly in older AML patients. Hypomethylating agents have not been associated with the high FL levels seen after cytotoxic chemotherapy and therefore might be associated with fewer cases of resistance to FLT-3 inhibition.25 In addition, epigenetic agents and FLT-3 inhibitors have been shown to induce differentiation effects in immature myeloid blasts, which could be enhanced by dual therapy.
Conclusion Herein, we show that the concomitant administration of DS was well tolerated and resulted in a high overall response rate and prolonged disease-free survival in relapsed/refractory FLT-3 ITD mutant AML patients. One patient who achieved CRi underwent subsequent allogeneic stem cell transplantation. These results suggest that DS might be a reasonable salvage option for these patients and a potential bridge to transplant. One patient in our cohort received DS as consolidation therapy because of the presence of other comorbidities that precluded HiDAC therapy. He remains disease-free with sorafenib maintenance therapy. The presence of lower FL levels at the time of AML diagnosis and initial remission, compared with relapse, suggests that DS might also have a role in upfront or consolidation treatment settings.26 We used a 10-day (as opposed to a 3- or 5-day) induction regimen of decitabine for combination therapy based on the high CR and response rates associated with prolonged administration.12 Although the outcomes of DS therapy compare favorably with those previously achieved with azacitidine and sorafenib therapy in FLT-3 mutant AML, the small number of patients treated in our study and the retrospective nature of our analysis might have influenced the results.25 For now, the best hypomethylating regimen to use in combination with FLT-3 inhibitor therapy remains uncertain. Further prospective clinical studies to confirm these results and establish the optimal dosing schedule and clinical setting for DS therapy are warranted. Our results also suggest that future clinical trials that combine decitabine with other FLT-3 inhibitors potentially more potent than sorafenib would be of interest.27
Clinical Practice Points Acute myeloid leukemia (AML) characterized by FMS-like
tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations is associated with poor outcome. Treatment options are limited, as these mutations confer resistance to conventional chemotherapy. FLT-3 receptor kinase inhibitors, such as sorafenib, have been studied as single agents as well as in combination with chemotherapy for the treatment of FLT-3 mutant AML. Here we describe our experience with the combination of the DNA hypomethylating agent, decitabine, and sorafenib in six
Monica R. Muppidi et al FLT-3 ITD mutant AML patients. Six patients with FLT-3 ITD mutant AML were treated off protocol with the combination of 10-day decitabine and sorafenib. Five of six patients (83%) achieved a response (1 CR, 4 CRi). Median overall survival was 155 days. Two patients proceeded onto subsequent allogeneic stem cell transplant. The combination of hypomethylating therapy and targeted FLT-3 inhibition was overall well tolerated and resulted in clinical responses, specifically in relapsed/refractory FLT-3 ITD mutant patients failing prior chemotherapy. Future prospective trials of this combination for the treatment of FLT-3 mutant AML patients are warranted. This approach may be of particular utility for the treatment of relapsed/refractory patients as a bridge to allogeneic stem cell transplantation or as upfront therapy for older, unfit individuals not considered candidates for intensive chemotherapy.
Acknowledgments This study was supported in whole or in part by funding from the Cancer Clinical Investigator Team Leadership Award awarded by the National Cancer Institute (NCI) through a supplement to P30CA016056 (E.S.W.). Other research support was provided by the Jacquie Hirsch Leukemia Research Fund (E.S.W.), the Szefel Foundation, the Leonard S. LuVullo Endowment for Leukemia Research, the Nancy C. Cully Endowment for Leukemia Research, the Babcock Family Endowment and the Heidi Leukemia Research Fund, Roswell Park Cancer Institute, Buffalo, NY (M.W.). Core resource support was provided by the NCI Cancer Center Support Grant for RPCI [CA016156].
Disclosure The authors have stated that they have no conflicts of interest.
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Decitabine and Sorafenib Therapy in FLT-3 ITD-Mutant Acute Myeloid Leukemia Monica R. Muppidi,1 Scott Portwood,1 Elizabeth A. Griffiths,1 James E. Thompson,1 Laurie A. Ford,1 Craig W. Freyer,2 Meir Wetzler,1 Eunice S. Wang1 Abstract Patients with FLT-3 ITD mutant AML have poor outcomes following standard chemotherapy. We show preclinical data demonstrating the in vitro synergistic effects of the FLT-3 inhibitor, sorafenib, and the hypomethylating agent, decitabine, on FLT-3 mutant AML cells. Treatment of 6 FLT-3 ITD mutant patients with decitabine and sorafenib resulted in overall responses in 5 patients (83%) and prolonged median survival. Background: Acute myeloid leukemia (AML) characterized by Feline McDonough Sarcoma-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes. Treatment options are limited, because these mutations confer resistance to conventional chemotherapy. FLT-3 inhibitors such as sorafenib have been studied as a single agent and in combination with conventional chemotherapy or azacytidine with fair responses. Patients and Methods: Here we describe our preclinical and clinical experience with the combination of the DNA hypomethylating agent, decitabine and sorafenib for the treatment of FLT-3 ITD-mutant AML. Results: In vitro treatment of the human FLT-3 ITD-mutant AML cell line, MV4-11, with both drugs significantly improved growth inhibition over single-agent therapy and resulted in synergistic antitumor effects (combination index < 1). A case series of 6 patients treated with off protocol combination of decitabine and sorafenib demonstrated overall responses in 5 patients (83%) with a median survival of 155 days. Four of the 5 patients (80%) with relapsed/refractory AML achieved complete responses with incomplete count recovery. The combination was also well tolerated. Conclusion: Further investigation is warranted to confirm these responses. Clinical Lymphoma, Myeloma & Leukemia, Vol. 15, No. S1, S73-9 ª 2015 Elsevier Inc. All rights reserved. Keywords: Combination therapy, FLT-3 inhibitors, Hypomethylating agents, Targeted agents
Introduction Patients with acute myeloid leukemia (AML) characterized by Feline McDonough Sarcoma-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes, especially in the relapsed and refractory setting.1-4 Because these mutations appear to confer resistance to conventional chemotherapy, treatment options are limited. Because of their dismal prognosis, patients with FLT-3emutant AML are usually offered intensive induction chemotherapy followed by allogeneic stem cell transplantation. Many patients, however, particularly those of older age, are not candidates 1
Leukemia Service, Department of Medicine Department of Pharmacy Roswell Park Cancer Institute, Buffalo, NY 2
Submitted: Dec 11, 2014; Revised: Jan 5, 2015; Accepted: Feb 26, 2015; Epub: Mar 6, 2015 Address for correspondence: Monica R. Muppidi, MD, Department of Medicine, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263 Fax: 716-845-8741; e-mail contact: [email protected]
2152-2650/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clml.2015.02.033
for intensive chemotherapy or transplantation, especially in the relapsed setting.4 Numerous small molecule FLT-3 inhibitors are in active clinical evaluation for the treatment of FLT-3emutant AML. Targeted FLT-3 inhibitors have been shown to induce apoptosis of peripheral blasts and cause differentiation of immature bone marrow blasts.5 Sorafenib is a multikinase inhibitor with known activity against FLT-3 ITD-mutated AML cells in vitro and in vivo.6 This agent has also been tested in clinical trials as a single agent and in combination with cytarabine and/or anthracycline chemotherapy for AML patients with FLT-3 mutant and wild type disease. Although some patients have achieved clinical remissions, responses typically are short-lived because of the rapid development of resistance.7 The underlying mechanisms of sorafenib resistance include inadequate target inhibition, the development of FLT-3 tyrosine kinase domain mutations, and other mechanisms.8 For these reasons, the combination of sorafenib with other antileukemic agents might demonstrate improved efficacy.
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Decitabine and Sorafenib in FLT-3 ITD-Mutant AML Decitabine is a hypomethylating agent, which has increasingly been used for the treatment of older patients with AML, particularly those individuals considered unfit for standard induction chemotherapy. Previous studies have demonstrated that overall survival after decitabine induction is at least equivalent to that achieved with best supportive care or low-dose cytarabine for AML patients.9 Recent retrospective analyses have also suggested equivalent outcomes for decitabine compared with intensive chemotherapy, particularly for older AML patients with lower white blood cell
(WBC) count at presentation and poor performance status.10,11 Although decitabine has been administered in 3- and 5-day regimens for AML treatment, phase II results have demonstrated the highest response rates after a 10-day decitabine regimen.12
Patients and Methods We hypothesized that the combination of sorafenib with decitabine would improve clinical responses in patients with FLT-3 ITD mutant AML by inhibiting complementary biological pathways
Figure 1 Inhibition of MV4-11 Cell Growth by Decitabine (Dec) and Sorafenib (Sor). Representative Results of 3-(4, 5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium bromide Colorimetric Assays Plated in Triplicate With Human FMS-Like Tyrosine Kinase-3 Internal Tandem Duplication Mutant Acute Myeloid Leukemia Cells (MV4-11) and Treated With Decitabine (D), Sorafenib (S), and the Combination of the 2 Drugs (D D S) for 72 Hours Followed by Cell Viability Detection. Data Are Depicted as (A) Bar Graphs Showing Mean ± SD, (B) Dose Effect Response With Doses Ranging From 0 to 300 mM, and (C) Determination of Combination Index of the 2 Drugs Showing Synergy (Combination Index, < 1) for All Tested Combinations of the 2 Drugs (Compusyn Software, Paramus, NJ)
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Abbreviation: Fa ¼ fraction affected.
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Monica R. Muppidi et al Figure 1 Continued
promoting leukemia growth and limiting the development of resistance. To test this, we performed in vitro assays to assess the effects of decitabine, sorafenib, and combination therapy on a FLT-3 mutant human AML cell line. We also treated 6 adult patients with confirmed FLT-3 ITD mutant AML at our comprehensive cancer center with decitabine and sorafenib (DS) combination therapy.
Results In Vitro Assays The human AML cell line, MV4-11, which expresses FLT-3 ITD mutations with constitutively phosphorylated receptor protein, was cultured in the presence of decitabine (1, 10, and 100 mM), sorafenib (1, 10, and 100 mM) (LC Laboratories, Woburn, MA), or both drugs.13 Cell viability after 72 hours was assessed in triplicate wells using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay (Thiazolyl Blue Tetrazolium Blue, Sigma) according to manufacturer instructions. Absorbance (570/690 nm) was measured using a Biotek Synergy HT multitask plate reader using KC4 software (Version 3.4) (BioTek, Winooski, VT). Percent inhibition of growth was normalized to untreated control samples. Improved inhibition of MV4-11 growth was consistently observed after exposure to the combination versus to each single-agent treatment (Figure 1A). The effects of both drugs were analyzed using Compusyn software (Version 1.0) (ComboSyn Inc, Paramus, NJ). Dose response curves and determination of combination index (CI) are shown, with the latter demonstrating synergy (CI < 1) for all combination regimens tested (Figure 1).14
Patients From 2011 to the present, 6 patients with confirmed FLT-3 ITD-mutant AML received off protocol DS therapy at our institute. Although off protocol, all individuals provided written informed consent for treatment with these 2 agents. This
retrospective review of available clinical, pathological, and treatment information on these patients was approved by our institutional review board. The mean age of patients was 56 years (range, 33-70). Two-thirds (4/6) were women. Five of the 6 patients had relapsed or refractory AML, and 1 patient had newly diagnosed AML (patient 4). All patients had AML characterized by normal karyotype and FLT-3 ITD mutations, with 5 of the 6 cases also containing nucleophosmin (NPM-1) mutations. Half (50%) of the patients had received 2 or more previous therapies. Two patients had undergone previous allogeneic stem cell transplant. All patients received at least 1 cycle (28 days) of concurrent intravenous decitabine 20 mg/m2 daily and sorafenib 200 or 400 mg orally twice a day. Five of the 6 patients received decitabine induction for 10 days for the first 1 to 2 cycles. Two of these patients achieved a morphological response and received additional 5day cycles of decitabine as consolidation therapy. One patient (patient 4) with treatment-naive de novo FLT-3emutant AML received 5-day DS for consolidation therapy after induction with cytarabine and daunorubicin (“7þ3” regimen) (Table 1). All patients received standard neutropenic prophylaxis with antimicrobial agents. The overall response rate was 83%, including 1 complete remission (CR; 16%), and 4 (66%) achieved a CR with incomplete count recovery (CRi). Eighty percent (4/5) of patients with relapsed refractory AML attained CRi after 1 to 2 cycles. Three patients (patients 1, 2, and 5) had FLT-3 ITD allele ratios measured before and after DS therapy. The allele ratio decreased in 2 patients (patients 1 and 2) after DS therapy, correlating with achievement of CRi. Two patients (patients 1 and 5) underwent subsequent allogeneic stem cell transplantation. The median overall survival was 155 days (range, 59-440) from the initiation of DS to death from any cause or last known follow-up (Figure 2). The most common complications reported with DS therapy were neutropenic infections (2/6 patients), specifically typhlitis,
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N 59 CRi 2 Relapsed 58 6
F
2
1 2 F 33 5
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Abbreviations: Allo HSCT ¼ allogeneic hematopoietic stem cell transplant; AML ¼ acute myeloid leukemia; CHF ¼ congestive heart failure; CRi ¼ complete remission with incomplete count recovery; DS ¼ decitabine and sorafenib combination therapy; ECOG ¼ Eastern Cooperative Oncology Group performance status; F ¼ female; M ¼ male; N ¼ no; NR ¼ no response; Y ¼ yes.
Dead
Alive
Dose reduced because of diarrhea None Diarrhea, transaminitis CHF Y 440
None N 275 1 1 59 4
M
Treatment-naive de novo Relapsed
CR
Sepsis, mucormycosis N 127 CRi 64 3
M
3 1 Relapsed
NR
Alive
Alive
Dead Alive
None Held because of reduced ECOG Discontinued because of infection None Transaminitis Neutropenic fever Y N 142 168 CRi CRi 1 4 3 1 Relapsed Relapsed F F 54 70 1 2
Response DS Cycles, n Previous AML Diagnosis Therapies, n Sex Age, Years Patient
Table 1 Characteristics and Outcomes of FLT-3 ITD Mutant AML Patients Treated With DS
Overall Survival, Days
Follow-Up Allo HSCT
Side Effects
Dose Modifications
Current Status (Alive/Dead)
Decitabine and Sorafenib in FLT-3 ITD-Mutant AML pneumonia and cellulitis, and grade 1-2 transaminitis (2/6 patients). One patient had invasive mucormycosis (patient 3). Although 1 patient (patient 5) developed diarrhea, the cause was multifactorial including possible gastrointestinal graft versus host disease (GVHD). Generalized fatigue and decline in Eastern Cooperative Oncology Group (ECOG) performance status was observed in 2 individuals (patients 2 and 5) but might have also been from other causes such as deconditioning because of prolonged hospitalization and underlying relapsed disease. Heart failure was noted in 1 patient with extensive previous anthracycline exposure (patient 6). Reasons for discontinuation of DS therapy were diverse. Decitabine was stopped in 1 patient because of diagnosis of mucormycosis. Sorafenib was stopped at the beginning of cycle 3 in 1 patient (patient 2) because of decline in performance status and was dose reduced in another (patient 5) because of diarrhea (Table 1).
Patient 1 A 54-year-old Caucasian woman presented to an outside facility in February 2011 with a WBC count of 160,000/mL with 90% peripheral blasts. Bone marrow biopsy revealed normal karyotype AML (myelomonocytic leukemia) with 70% blasts, NPM-1, and FLT-3 ITD mutations. She underwent induction treatment with daunorubicin and cytarabine followed by 1 cycle of high-dose cytarabine consolidation (HiDAC) therapy. She was referred for peripheral blood stem cell transplant at that time. However, she had relapsed disease within 2 months. She received reinduction chemotherapy with etoposide and mitoxantrone without response. She was then referred to our institute and was enrolled in a clinical protocol with intermediate-dose cytarabine and lenalidomide. A follow-up bone marrow biopsy demonstrated refractory AML with 75% blasts, normal cytogenetics, and NPM-1 and FLT-3 ITD mutations with a FLT-3 ITD/FLT-3 wild type allele ratio of 6.56. Her ECOG performance status was 1. She initiated therapy with decitabine 20 mg/m2 intravenously (I.V.) daily for 10 days combined with sorafenib 400 mg orally twice daily for 28 days. She developed vitreous hemorrhage secondary to low platelet count and Grade 1 transaminitis, both of which resolved spontaneously. No dose modification was required. A day 30 bone marrow biopsy showed a CRi with an FLT-3 ITD allele ratio of 1.16. She subsequently underwent an 8/10 mismatched unrelated allogeneic peripheral blood stem cell transplant. Unfortunately, at day > 85, a bone marrow biopsy showed relapsed disease. The patient died from complications of GVHD.
Patient 2 A 70-year-old Caucasian woman presented in February 2014 with severe anemia and a WBC count of 92,000 with 80% blasts. Bone marrow biopsy revealed AML with monocytic differentiation and 61% blasts, normal cytogenetics, and NPM-1 and FLT-3 ITD mutations. She initiated induction treatment with cytarabine and daunorubicin. Her course was complicated by myocardial infarction, acute gastrointestinal bleeding, bilateral pneumonia, urinary tract infection, renal failure, and Clostridium difficile infection. She had a prolonged course in the intensive care unit leading to debilitation. On stabilization of her acute conditions, the patient opted for no further therapy and was discharged for comprehensive physical therapy and occupational therapy rehabilitation. Her
Monica R. Muppidi et al Figure 2 Overall Survival of FMS-Like Tyrosine Kinase-3 Internal Tandem Duplication Mutant Acute Myeloid Leukemia Patients From Initiation of Decitabine and Sorafenib (DS) Therapy
performance status was 1. He was initiated on off-protocol decitabine for 10 days along with sorafenib 200 mg once daily for 28 days. Sorafenib was initiated at a low dose because of concern for gastrointestinal toxicity. It was increased to 200 mg twice daily in cycle 2. A bone marrow biopsy after 2 cycles showed morphological CRi with continued presence of FLT-3 ITD mutation with an allele ratio of 0.03. Therapy was complicated by bilateral pneumonia after cycle 1 and neutropenic fever after cycle 2. During cycle 3, he developed mucormycosis of the hard palate despite antifungal azole prophylaxis and was treated with intravenous antifungal medications. The patient declined any aggressive surgical debridement and opted to proceed with conservative therapy. A decision was made to hold decitabine in view of mucormycosis. The patient continues to receive sorafenib 200 mg twice daily and has achieved complete count recovery with supportive care and antifungal treatment.
Patient 4
peripheral blood counts did not show any evidence of leukemia. In April 2014, she presented from the rehabilitation center with a WBC count of 40,000 with 53% blasts consistent with relapse. Molecular testing on the peripheral blood showed FLT-3 ITD mutation (allele ratio, 0.91) and NPM-1 mutations. Her ECOG performance status was 2. The patient was initiated on off-protocol decitabine 20 mg/m2 I.V. daily for 10 days in addition to sorafenib 400 mg orally twice a day for 28-day cycles. She tolerated cycle 1 of therapy well. Cycle 2 of therapy was complicated by recurrent Clostridium difficile infection, typhilitis, neutropenic sepsis with Stenotrophomonas pneumonia, and cellulitis of her upper extremity. Sorafenib was held for a brief period because of typhilitis and reinitiated at clinical improvement of symptoms. A bone marrow biopsy at the end of cycle 2 showed morphological CRi, normal cytogenetics, and FLT-3 ITD mutation with an allele ratio of 0.36. Because of extensive hospitalization and complications, the patient’s performance status declined. Cycle 3 was delayed by 5 weeks. She then received consolidation therapy with decitabine 20 mg/m2 for 5 days in the setting of remission. Sorafenib was held because of a decline in performance status. The patient was admitted for neutropenic fever with cellulitis. Despite receiving a fourth cycle of 5-day decitabine consolidation, she was found to have relapsed disease with 86% peripheral blood blasts. She was subsequently enrolled in a phase 1 trial of a novel FLT-3 inhibitor and continues to receive treatment.
Patient 3 A 64-year-old Caucasian man presented in June 2013 with a WBC count of 69,000/mL and 70% peripheral blasts. Bone marrow showed AML with normal cytogenetics, NPM-1 and FLT3 ITD mutations with a FLT-3 allele ratio of 0.28. The patient received cytarabine and daunorubicin induction followed by 2 courses of HiDAC consolidation. Further chemotherapy was held because of development of sepsis. In May 2014, the patient presented with relapsed normal karyotype AML with 68% blasts and FLT-3 ITD mutation (allele ratio of 4.19). The patient’s ECOG
A 59-year-old Caucasian man presented in October 2013 with severe anemia, thrombocytopenia, and 82% peripheral blasts. A bone marrow biopsy showed AML with normal cytogenetics characterized by FLT-3 ITD without NPM-1 mutations. The patient was initiated with protocol therapy with decitabine for 5 days followed by cytarabine and daunorubicin induction therapy. His course was complicated by severe bilateral multifocal pneumonia leading to prolonged intensive care support. Bone marrow biopsy on day 44 showed CRi. HiDAC consolidation therapy was deferred because of a poor ECOG performance status of 3 and he was initiated on therapy with decitabine 20 mg/m2 for 5 days along with sorafenib 400 mg orally twice daily. A bone marrow biopsy after cycle 1 of DS therapy confirmed continued CRi. Although he tolerated the therapy well without any side effects, he was subsequently transferred to a long-term rehabilitation facility. Because of transportation difficulties, no further treatment with decitabine was given. He remains in CR with complete count recovery with sorafenib 400 mg twice daily treatment.
Patient 5 A 33-year-old Caucasian woman was diagnosed in October 2011 with normal karyotype AML characterized by FLT-3 ITD and NPM-1 mutations. She received induction chemotherapy with cytarabine and idarubicin followed by 2 cycles of HiDAC consolidation therapy. She then underwent unrelated donor allogeneic peripheral blood stem cell transplant in February 2012. In July 2013, she presented with overt relapsed disease with a WBC count of 144,000/mL, acute renal failure, malignant pleural effusions, and central nervous system involvement. She received intrathecal methotrexate and reinduction therapy with cytarabine and daunorubicin followed by single-agent sorafenib. Unfortunately her disease was refractory with evidence of increasing peripheral blasts and a FLT-3 allele ratio of 2.54. Her ECOG performance status was 2. She initiated decitabine 20 mg/m2 for 10 days along with sorafenib 400 mg orally twice daily. Sorafenib was held for 10 days because of Grade 2 transaminitis and diarrhea. Sorafenib was then reinitiated at a lower dose of 200 mg orally once daily. Repeat bone marrow biopsy after 1 cycle of DS showed 41% AML blasts with NPM-1 and FLT-3 ITD mutations (allele ratio of 9.54). She received
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Decitabine and Sorafenib in FLT-3 ITD-Mutant AML high-dose cytarabine and mitoxantrone reinduction therapy followed by a second allogeneic peripheral stem cell transplant and remains in continued remission.
Patient 6 A 58-year-old Caucasian woman was diagnosed in October 2011 with AML characterized by normal cytogenetics, NPM-1 and FLT-3 ITD mutations. She underwent induction therapy with cytarabine and daunorubicin followed by 3 cycles of HiDAC consolidation therapy. Unfortunately she presented with relapsed AML in April 2012. She received reinduction therapy with cytarabine, idarubicin, and pravastatin on protocol followed by matched unrelated allogeneic peripheral stem cell transplant. In October 2012 she was again found to have relapsed FLT-3 ITD mutant disease and was initiated on decitabine for 10 days and sorafenib 400 mg orally twice daily. The patient completed 2 cycles of DS complicated by bacteremia, GVHD (liver, lung), and congestive heart failure. A limited cardiac workup demonstrated nonischemic cardiomyopathy thought to be likely multifactorial due to previous extensive anthracycline therapy and sorafenib. The patient died after a prolonged hospitalization. Bone marrow biopsy at time of autopsy demonstrated no morphological evidence of AML consistent with CRi.
Discussion
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Internal tandem duplication mutations of the FLT-3 gene are seen in approximately 23% of all AML patients.15 These mutations confer a poor prognosis in terms of disease outcomes in all age groups, including older patients, with a median overall survival of < 1 year and high relapse rates.1-4 Sorafenib is a small molecule inhibitor of multiple tyrosine kinases, including vascular endothelial growth factor, platelet derived growth factor, and FLT-3 receptors. Preclinical studies have demonstrated that sorafenib effectively induces cell cycle arrest and apoptosis in blasts containing FLT-3 ITD mutations.6 In an open-label single-arm study, a large number of patients obtained complete or near complete elimination of bone marrow blasts after sorafenib therapy along with myeloid differentiation; however, these responses were not sustained with most of the patients with disease relapse after 72 days.16 The reasons for early relapses in FLT-3 mutant AML patients are under active investigation. Although specific tyrosine kinase domain mutations in the FLT-3 receptor are known to confer sorafenib resistance, increased levels of the FLT-3 ligand (FL), a hematopoietic growth factor predominately synthesized by bone marrow microvascular endothelial cells, T cells, and leukemia cells, might also be responsible.17-19 High FL levels induced under stem cell-depleted conditions (ie, after induction and consolidation chemotherapy) or at the time of disease relapse can bind to FLT-3emutated receptors on AML cells to fuel AML proliferation and impede the potency of FLT-3 inhibitors.20,21 Multiple clinical studies to evaluate sorafenib in combination with conventional chemotherapy for the treatment of FLT-3emutant AML have had variable results. A randomized placebo-controlled study examining the addition of sorafenib to intensive chemotherapy in elderly patients found no survival benefit and increased toxicity with the combined drugs.22 Treatment with low-dose cytarabine and sorafenib therapy in other older patients was also largely ineffective.23
Clinical Lymphoma, Myeloma & Leukemia June 2015
Although sorafenib combined with cytarabine and idarubicin induction resulted in high response rates, after a median follow up of 9 months, more than half of the patients had disease relapse.24 These findings support the need for novel regimens of a combination of sorafenib with other antileukemic therapies to optimize outcomes. Decitabine represents an attractive agent for combination studies with sorafenib (and/or other FLT-3 inhibitors) because of its relative tolerability and overall clinical response rates, particularly in older AML patients. Hypomethylating agents have not been associated with the high FL levels seen after cytotoxic chemotherapy and therefore might be associated with fewer cases of resistance to FLT-3 inhibition.25 In addition, epigenetic agents and FLT-3 inhibitors have been shown to induce differentiation effects in immature myeloid blasts, which could be enhanced by dual therapy.
Conclusion Herein, we show that the concomitant administration of DS was well tolerated and resulted in a high overall response rate and prolonged disease-free survival in relapsed/refractory FLT-3 ITD mutant AML patients. One patient who achieved CRi underwent subsequent allogeneic stem cell transplantation. These results suggest that DS might be a reasonable salvage option for these patients and a potential bridge to transplant. One patient in our cohort received DS as consolidation therapy because of the presence of other comorbidities that precluded HiDAC therapy. He remains disease-free with sorafenib maintenance therapy. The presence of lower FL levels at the time of AML diagnosis and initial remission, compared with relapse, suggests that DS might also have a role in upfront or consolidation treatment settings.26 We used a 10-day (as opposed to a 3- or 5-day) induction regimen of decitabine for combination therapy based on the high CR and response rates associated with prolonged administration.12 Although the outcomes of DS therapy compare favorably with those previously achieved with azacitidine and sorafenib therapy in FLT-3 mutant AML, the small number of patients treated in our study and the retrospective nature of our analysis might have influenced the results.25 For now, the best hypomethylating regimen to use in combination with FLT-3 inhibitor therapy remains uncertain. Further prospective clinical studies to confirm these results and establish the optimal dosing schedule and clinical setting for DS therapy are warranted. Our results also suggest that future clinical trials that combine decitabine with other FLT-3 inhibitors potentially more potent than sorafenib would be of interest.27
Clinical Practice Points Acute myeloid leukemia (AML) characterized by FMS-like
tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations is associated with poor outcome. Treatment options are limited, as these mutations confer resistance to conventional chemotherapy. FLT-3 receptor kinase inhibitors, such as sorafenib, have been studied as single agents as well as in combination with chemotherapy for the treatment of FLT-3 mutant AML. Here we describe our experience with the combination of the DNA hypomethylating agent, decitabine, and sorafenib in six
Monica R. Muppidi et al FLT-3 ITD mutant AML patients. Six patients with FLT-3 ITD mutant AML were treated off protocol with the combination of 10-day decitabine and sorafenib. Five of six patients (83%) achieved a response (1 CR, 4 CRi). Median overall survival was 155 days. Two patients proceeded onto subsequent allogeneic stem cell transplant. The combination of hypomethylating therapy and targeted FLT-3 inhibition was overall well tolerated and resulted in clinical responses, specifically in relapsed/refractory FLT-3 ITD mutant patients failing prior chemotherapy. Future prospective trials of this combination for the treatment of FLT-3 mutant AML patients are warranted. This approach may be of particular utility for the treatment of relapsed/refractory patients as a bridge to allogeneic stem cell transplantation or as upfront therapy for older, unfit individuals not considered candidates for intensive chemotherapy.
Acknowledgments This study was supported in whole or in part by funding from the Cancer Clinical Investigator Team Leadership Award awarded by the National Cancer Institute (NCI) through a supplement to P30CA016056 (E.S.W.). Other research support was provided by the Jacquie Hirsch Leukemia Research Fund (E.S.W.), the Szefel Foundation, the Leonard S. LuVullo Endowment for Leukemia Research, the Nancy C. Cully Endowment for Leukemia Research, the Babcock Family Endowment and the Heidi Leukemia Research Fund, Roswell Park Cancer Institute, Buffalo, NY (M.W.). Core resource support was provided by the NCI Cancer Center Support Grant for RPCI [CA016156].
Disclosure The authors have stated that they have no conflicts of interest.
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