Patterns of molecular response to and relapse after combination of sorafenib, idarubicin, and cytarabine in patients with FLT3 mutant acute myeloid leukemia

BackgroundFMS-like tyrosine kinase 3 (FLT3) is a class III receptor tyrosine kinase involved in hematopoietic progenitor cell development. Mutations of FLT3 have been reported in about a third of patients with acute myeloid leukemia (AML), and inhibitors of FLT3 are of clinical interest. Sorafenib is an orally active multikinase inhibitor with potent activity against FLT3 and the Raf/ERK/MEK kinase pathway.MethodsWe studied the patterns of molecular response and relapse in 18 patients with mutated FLT3 treated with the combination of sorafenib, idarubicin, and cytarabine.ResultsThe median follow-up was 9 months. Sixteen patients achieved complete remission (CR), and the other 2 patients achieved CR but lacked platelet recovery for an overall response rate of 100%. Ten patients had their FLT3-mutated clone eradicated, with 6 patients who showed some residual FLT3-mutated cells, and 2 patients who showed persistent FLT3-mutated cells. The elimination of FLT3-mutated population at the time of morphologic CR, however, was not predictive of relapse. After a median follow-up of 9 months (range, 1-16 months), 10 (55%) patients had relapsed, with a median CR duration of 8.8 months (range, 1-9.5 months). By DNA sequencing, there was no evidence of an acquired FLT3 point mutation at the time of relapse in 7 patients tested, which suggested the presence of other mechanisms of sorafenib resistance.ConclusionSorafenib, combined with chemotherapy, is effective in attaining CR, but relapses still occur.     

Clinical outcomes in patients with relapsed/refractory FLT3-mutated acute myeloid leukemia treated with gilteritinib who received prior midostaurin or sorafenib

The fms-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib is indicated for relapsed or refractory (R/R) FLT3-mutated acute myeloid leukemia (AML), based on its observed superior response and survival outcomes compared with salvage chemotherapy (SC). Frontline use of FLT3 tyrosine kinase inhibitors (TKIs) midostaurin and sorafenib may contribute to cross-resistance to single-agent gilteritinib in the R/R AML setting but has not been well characterized. To clarify the potential clinical impact of prior TKI use, we retrospectively compared clinical outcomes in patients with R/R FLT3-mutated AML in the CHRYSALIS and ADMIRAL trials who received prior midostaurin or sorafenib against those without prior FLT3 TKI exposure. Similarly high rates of composite complete remission (CRc) were observed in patients who received a FLT3 TKI before gilteritinib (CHRYSALIS, 42%; ADMIRAL, 52%) and those without prior FLT3 TKI therapy (CHRYSALIS, 43%; ADMIRAL, 55%). Among patients who received a prior FLT3 TKI in ADMIRAL, a higher CRc rate (52%) and trend toward longer median overall survival was observed in the gilteritinib arm versus the SC arm (CRc = 20%; overall survival, 5.1 months; HR = 0.602; 95% CI: 0.299, 1.210). Remission duration was shorter with prior FLT3 TKI exposure. These findings support gilteritinib for FLT3-mutated R/R AML after prior sorafenib or midostaurin.Subject terms: Diseases, Medical research     

Long-term survival of sorafenib-treated FLT3-ITD–positive acute myeloid leukaemia patients relapsing after allogeneic stem cell transplantation

BackgroundFms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD)–positive acute myeloid leukaemia (AML) relapsing after allogeneic stem cell transplantation (allo-SCT) has a dismal prognosis with limited therapeutic options. FLT3-ITD kinase inhibition is a reasonable but palliative experimental treatment alternative in this situation. Information on long-term outcome is not available.MethodsWe performed a long-term follow-up analysis of a previously reported cohort of 29 FLT3-ITD–positive AML patients, which were treated in relapse after allo-SCT with sorafenib monotherapy.FindingsWith a median follow-up of 7.5 years, 6 of 29 patients (21%) are still alive. Excluding one patient who received a second allo-SCT, five patients (17%) achieved sustained complete remissions with sorafenib. Four of these patients are in treatment-free remission for a median of 4.4 years.InterpretationSorafenib may enable cure of a proportion of very poor risk FLT3-ITD–positive AML relapsing after allo-SCT.     

Prognostic implication of gene mutations on overall survival in the adult acute myeloid leukemia patients receiving or not receiving allogeneic hematopoietic stem cell transplantations

Several gene mutations have been shown to provide clinical implications in patients with acute myeloid leukemia (AML). However, the prognostic impact of gene mutations in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains unclear. We retrospectively evaluated the clinical implications of 8 gene mutations in 325 adult AML patients; 100 of them received allo-HSCT and 225 did not. The genetic alterations analyzed included NPM1, FLT3-ITD, FLT3-TKD, CEBPA, RUNX1, RAS, MLL-PTD, and WT1. In patients who did not receive allo-HSCT, older age, higher WBC count, higher lactate dehydrogenase level, unfavorable karyotype, and RUNX1 mutation were significantly associated with poor overall survival (OS), while CEBPA double mutation (CEBPA^double-mut) and NPM1^mut/FLT3-ITD^neg were associated with good outcome. However, in patients who received allo-HSCT, only refractory disease status at the time of HSCT and unfavorable karyotype were independent poor prognostic factors. Surprisingly, RUNX1 mutation was an independent good prognostic factor for OS in multivariate analysis. The prognostic impact of FLT3-ITD or NPM1^mut/FLT3-ITD^neg was lost in this group of patients receiving allo-HSCT, while CEBPA^double-mut showed a trend to be a good prognostic factor. In conclusion, allo-HSCT can ameliorate the unfavorable influence of some poor-risk gene mutations in AML patients. Unexpectedly, the RUNX1 mutation showed a favorable prognostic impact in the context of allo-HSCT. These results need to be confirmed by further studies with more AML patients.     

Hyperactivation of the RAS signaling pathway in myelodysplastic syndrome with AML1/RUNX1 point mutations.

AML1/RUNX1 mutations have been reported frequently in myelodysplastic syndrome (MDS) patients, especially those diagnosed with refractory anemia with excess blast (RAEB), RAEB in transformation (RAEBt), or AML following MDS (these categories are defined as MDS/AML). Although AML1 mutations are suspected to play a pivotal role in the development of MDS/AML, acquisition of additional genetic alterations is also necessary. We analyzed gene alterations in MDS/AML patients with AML1 mutations, comparing them to alterations in those without an AML1 mutation. AML1 mutations were significantly associated with -7/7q-, whereas MDS/AML patients without AML1 mutations showed a high frequency of -5/5q- and a complex karyotype. Patients with AML1 mutations showed more mutations of their FLT3, N-RAS, PTPN11, and NF1 genes, resulting in a significantly higher mutation frequency for receptor tyrosine kinase (RTK)-RAS signaling pathways in AML1-mutated MDS/AML patients compared to AML1-wild-type MDS/AML patients (38% versus 6.3%, P < 0.0001). Conversely, p53 mutations were detected only in patients without AML1 mutations. Furthermore, blast cells of the AML1-mutated patients expressing surface c-KIT, and SHP-2 mutants contributed to prolonged and enhanced extracellular signal-regulated kinase activation following stem cell factor stimulation. Our results suggest that MDS/AML arising from AML1/RUNX1 mutations has a significant association with -7/7q- alteration, and frequently involves RTK-RAS signaling pathway activation.     

The Future of Targeting FLT3 Activation in AML

Internal tandem duplications (ITD) and tyrosine-kinase domain (TKD) mutations of the FMS-like tyrosine-kinase 3 (FLT3) can be found in up to one third of patients with acute myeloid leukemia (AML) and confer a poor prognosis. First discovered 20 years ago, these mutations were identified as viable therapeutic targets, and FLT3 tyrosine-kinase inhibitors (TKIs) have been in development for the last decade with steadily increasing potency. However, FLT3-mutated AML often acquires resistance to the growing armamentarium of FLT3 inhibitors through a variety of mechanisms. In this review, we discuss the distinct clinical phenotype of FLT3-mutated AML, historically and currently available therapeutics, mechanisms of resistance, ongoing trials, and future outlook at treatment strategies.     

Effect of NPM1 and FLT3 Mutations on the Outcomes of Elderly Patients With Acute Myeloid Leukemia Receiving Standard Chemotherapy

BackgroundThe effect of prognostically important gene mutations (MUTs), nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) and fms-related tyrosine kinase 3 (FLT3), in elderly patients with acute myeloid leukemia (AML) is not well defined.Patients and MethodsWe analyzed 557 patients, 65 years of age or older with newly diagnosed AML, treated at our institution between 2000 and 2010 with cytotoxic chemotherapy. NPM1 and FLT3 analysis were available in 146 patients (26%) and 388 patients (70%), respectively.ResultsNPM1 and FLT3 MUTs occurred in 16% and 12% of patients, respectively. No difference in median overall survival was observed between FLT3-MUT and NPM1-MUT patients who received cytotoxic chemotherapy. Outcome was significantly better among patients with NPM1-MUT/FLT3-wild type (WT) genotype (n = 14) compared with patients carrying FLT3/NPM1 genotypes other than NPM1-MUT/FLT3-WT (n = 125). The complete remission rates were 71% and 49%, respectively (P = .11). The median survival was 21.5 months vs. 9.0 months and estimated 2-year survival rates were 51% vs. 38%, respectively (P = .003). NPM1 and FLT3 MUTs appear to occur less frequently in elderly AML patients. The prognostic effect of isolated NPM1- or isolated FLT3-MUT is minimal.ConclusionElderly AML patients with NPM1-MUT/FLT3-WT genotype have significantly improved outcomes compared with patients with other NPM1/FLT3 genotypes when treated with cytotoxic chemotherapy.     

Invasive Mold Infections in FLT3-Mutated Acute Myeloid Leukemia

BackgroundThe incidence and risk factors for invasive mold infections (IMI) in acute myeloid leukemia (AML) patients carrying FLT3 mutations have not been addressed.Patients and MethodsThis retrospective cohort included FLT3-mutated AML patients (2008-2018). Primary outcome was IMI incidence within 6 months after first induction or salvage therapy.ResultsWe included 108 patients receiving fluconazole or micafungin prophylaxis. IMI incidence after induction and salvage therapy was 4.8% and 14.8%, respectively, and did not differ between patients receiving 3+7 regimen or 3+7 plus midostaurin (4.3% vs 4.5%). In a bivariate analysis, age (odds ratio, 1.11; P = .027) and FLT3 ITD mutation (odds ratio, 0.05; P = .023) were independently associated with IMI after induction chemotherapy. Gilteritinib was more frequently prescribed in patients with relapsed/refractory disease who developed IMI (50% vs 27.3%, P = .563).ConclusionFLT3 ITD mutation may be a preventive factor for IMI. Neither midostaurin nor salvage gilteritinib significantly increased the risk of IMI in this population.     

FLT3 Inhibition in Acute Myeloid Leukemia

Mutations in the FLT3 receptor tyrosine kinase are the most frequently found mutations in acute myeloid leukemia (AML). Patients with FLT3 internal tandem duplication (ITD) mutations have poor prognoses. The approved FLT3 tyrosine kinase inhibitors (TKIs) midostaurin and gilteritinib improve survival in AML with FLT3 mutations. Multiple other FLT3 inhibitors are in clinical development. Patients frequently relapse after response to FLT3 inhibitors and the optimal use of FLT3 inhibitors in the upfront, relapse, and maintenance settings remain to be established. We will discuss the biology of FLT3, approved and investigational FLT3 inhibitors, resistance mechanisms, and emerging FLT3 TKI combination clinical trials.     

Prevalence and Clinical Outcome of FMS-Like Tyrosine Kinase Mutations Among Patients With Core Binding Factor—Acute Myeloid Leukemia: Systematic Review and Meta-Analysis

BackgroundCore binding factor acute myeloid leukemia (CBF-AML) belongs to favorable risk group in AML. However, approximately 50% of patients with CBF-AML remain incurable and their outcomes are also determined by the various co-occurring mutations. Though, FMS-like tyrosine kinase-3(FLT3) mutation in AML is associated with poor survival, the prevalence and prognostic significance of FLT3 mutations among CBF-AML is unknown.Patients and MethodsWe performed a systematic review and meta-analysis to assess the prevalence of FLT3 mutations (ITD and TKD) among patients with CBF-AML. The pooled prevalence of FLT3 mutations was estimated for patients with CBF-AML, t(8;21) and Inv(16). Pooled odds ratio was calculated to compare the prevalence of various FLT3 mutations within the 2 subsets of CBF-AML. A random effects model was adopted for analysis when heterogenicity existed (P_{heterogenicity}< 0.05 or I² > 50%). Otherwise, a fixed effects model was used.ResultsThe pooled prevalence of any FLT3 mutations among patients with CBF-AML was available from 18 studies and was 13% (95% CI: 10%-16%; I² = 79%). Comparison of prevalence of FLT3 mutations between the 2 subgroups of CBF-AML showed that patients with t(8;21) had a higher prevalence of FLT3-ITD [pooled odds ratio(OR): 2.23 (95% CI:1.41-3.53, P < .01)] and lower prevalence of FLT3-TKD [pooled OR: 0.29 (95% CI:0.19-0.44; P < .01)] compared to patients with Inv(16). Additionally, we have discussed the prognostic significance of FLT3 mutations in CBF-AML patients.ConclusionThe prevalence of FLT3-TKD mutation was commoner among Inv(16) AML while FLT3-ITD mutation was commoner among t(8;21) AML. Uniform reporting of outcomes is essential to understand the prognostic significance of FLT3 mutations among CBF-AML.     

Prognostic Impact of Concurrent DNMT3A,FLT3 and NPM1 Gene Mutations in Acute Myeloid Leukemia Patients

BackgroundAcute myeloid leukemia (AML) is one of the rapidly progressing malignancies which is characterized by unregulated proliferation of hematopoietic precursors. Technological improvements enhanced the availability of genetic AML biomarkers. The clinical relevance of these molecular markers for AML diagnosis, planning of therapy and risk stratification are increasing evidently.MethodsIn current study, one hundred newly diagnosed AML patients before receiving induction chemotherapy were included, they were subjected to clinical examination, cytochemical and morphological analysis of blood cells, flow cytometric, cytogenetic and molecular genetic analysis for detection of NPM1, FLT3-ITD and DNMT3A mutations. Direct sequencing analysis for detection of NPM1 and DNMT3A genes mutations were done. FLT3 /ITD gene mutation was detected by gel electrophoresis after PCR amplification.ResultsAccording to genetic markers, our AML patients are classified in to further 8groups. AML patients with three DNMT3A/FLT3/NPM1 gene mutations (AML ^{DNMT3A /FLT3/NPM1}) this group of patients presented with a heavy disease burden, had an elevated WBC in comparison to other groups (70 vs. 41 × 10³/μL; P = .019), and BM blast counts (71% vs. 55.6%, P < .02). When comparing eight groups for death event there were significant difference among groups; P = .005, group 1 (AML ^{DNMT3A /FLT3/NPM1}) showed rapid decline of the cumulative overall survival. There was a significant difference among 8 groups as regards response to treatment after 14 days (P = .02), group 7 AML with (DNMT3A +NMP1) gene mutations showed better response to treatment (100%), groups 1 and 3 AML with (NPM1+DNMT3A +NMP1) gene mutations and AML with isolated FLT3-ITD showed no response to treatment after 14 days. And as regards response to treatment after 28 days, the eight groups showed no significant difference (P = .14).ConclusionOur study supports adverse prognostic effect of presence of DNMT3A gene mutation either alone or in the presence of FLT3 and/or NPM1 gene mutations.     

Sorafenib (Nexavar) induces molecular remission and regression of extramedullary disease in a patient with FLT3-ITD+ acute myeloid leukemia

The fms-related tyrosine kinase 3 internal tandem duplication (FLT3-ITD) can be found in about one quarter of patients with acute myeloid leukemia (AML) [Small D. FLT3 mutations: biology and treatment. Hematology Am Soc Hematology. Educ. Program 2006;178-84 [Review]]. Patients who carry this mutation have a high risk of relapse even after allogeneic stem cell transplantation [Sheikhha MH, Awan A, Tobal K, Liu Yin JA. Prognostic significance of FLT3 ITD and D835 mutations in AML patients. Hematol J 2003;4:41-6; Meshinchi S, Arceci RJ, Sanders JE, Smith FO, Woods WB, Radich JP, et al. Role of allogeneic stem cell transplantation in FLT3/ITD-positive AML. Blood 2006;108(1):400-1]. Recent reports show that Sorafenib, a multikinase inhibitor has significant activity against FLT3-ITD(+) blasts in vitro [Auclair D, Miller D, Yatsula V, Pickett W, Carter C, Chang Y, et al. Antitumor activity of sorafenib in FLT3-driven leukemic cells. Leukemia 2007;21(3):439-45]. We here report the first clinical case of molecular remission induced by Sorafenib in a patient with FLT3-ITD(+) AML and extramedullary disease after allogenic stem cell transplantation.     

Prognostic value of FLT3 mutations among different cytogenetic subgroups in acute myeloid leukemia

BACKGROUND:

The impact of FMS‐like tyrosine kinase 3 (FLT3) mutations and mutation burden among cytogenetic subgroups of patients with acute myeloid leukemia (AML) other than normal karyotype (NK) AML is unclear.

METHODS:

Patients with newly diagnosed AML were divided among 3 cytogenetic subgroups: core binding factor (CBF) AML, NK‐AML, and poor‐risk AML.

RESULTS:

In total, 481 patients were included: 13% had, CBF‐AML, 57% had NK‐AML, and 30% had poor risk AML, and the frequency of any FLT3 mutations was 20%, 32%, and 7.6% in the respective cytogenetic subgroups. FLT3 mutation did not have an impact on event‐free survival (EFS) in patients with CBF‐AML (P = .84) and poor‐risk AML (P = .37). In patients with NK‐AML, EFS was worse in the FLT3‐internal tandem duplication (ITD) group (20 weeks vs 41 weeks; P < .00,001) but not in the FLT3‐tyrosine kinase domain (TKD) point mutation group (61 weeks vs 41 weeks; P = .15). Worse EFS and overall survival (OS) were observed among patients with NK‐AML and higher FLT3‐ITD burden but not among patients with FLT3‐TKD mutation. In multivariate analysis, FLT3‐ITD mutation was prognostic of EFS in patients with NK‐AML (hazard ratio, 3.1; P = .03).

CONCLUSIONS:

FLT3 mutations did not have a prognostic impact in patients with AML who had good‐risk and poor‐risk karyotypes. In patients with NK‐AML, FLT3‐ITD mutations led to worse survival, which was even worse among patients who had high mutation burden. Cancer 2011. © 2010 American Cancer Society.     

A Phase II Study of Midostaurin and 5-Azacitidine for Untreated Elderly and Unfit Patients With FLT3 Wild-type Acute Myelogenous Leukemia

BackgroundMidostaurin, a multikinase inhibitor, is approved for treatment of FLT3-mutant acute myeloid leukemia (AML). A phase I study established that midostaurin 75 mg orally twice daily for 14 days with standard dose azacitidine was safe and tolerable in elderly patients with AML. Herein, we report the phase II expansion cohort of previously untreated elderly or unfit patients with AML.Patients and MethodsPrimary objectives were to further describe the toxicity profile and determine the response rate in untreated patients with AML. Patients received midostaurin 75 mg orally twice daily on days 8 to 21 in combination with intravenous azacitidine at 75 mg/m² on days 1 to 7. Plasma inhibitory activity assay for FLT3 was performed pretreatment and on day 8 and day 15 of each cycle.ResultsTwenty-six patients (median age, 74 years; range, 59-85 years) with FLT3 wild-type AML were accrued. Patients received a median of 2 cycles of therapy (range, 1-10 cycles). Seven (29%) of 24 evaluable patients achieved a clinical response (4 complete response; 1 complete response with incomplete count recovery; and 2 partial response). The median overall survival was 244 days (95% confidence interval, 203-467 days). Hematologic, infectious, and gastrointestinal toxicities were comparable to similar studies. Peripheral blood FLT3 wild-type phosphorylation declined to 8% to 55% of pretreatment by day 15 of cycle 1 (7 patients) and declined with subsequent cycles (< 10% baseline) in 2 patients who were analyzed after cycle 3.ConclusionMultiple cycles of azacitidine and midostaurin were not well-tolerated, but persistent inhibition of FLT3 wild-type phosphorylation suggest intermittent dosing of midostaurin should be considered in future low-intensity regimens for FLT3-mutant AML.     

FLT3-TKD Mutations Associated With NPM1 Mutations Define a Favorable-risk Group in Patients With Acute Myeloid Leukemia

Background

Outcome of patients with mutation of the FLT3 tyrosine kinase domain (FLT3-TKD) in acute myeloid leukemia (AML) remains controversial.

Mutational analysis of DNMT3A improves the prognostic stratification of patients with acute myeloid leukemia

Nucleophosmin1 (NPM1) mutations are the most frequently detected gene mutations in acute myeloid leukemia (AML) and are considered a favorable prognostic factor. We retrospectively analyzed the prognosis of 605 Japanese patients with de novo AML, including 174 patients with NPM1-mutated AML. Although patients with NPM1-mutated AML showed a high remission rate, this was not a favorable prognostic factor for overall survival (OS); this is contrary to generally accepted guidelines. Comprehensive gene mutation analysis showed that mutations in codon R882 of DNA methyltransferase 3A (DNMT3A^R882 mutations) were a strong predicative factor indicating poor prognosis in all AML (p < 0.0001) and NPM1-mutated AML cases (p = 0.0020). Furthermore, multivariate analysis of all AML cases showed that DNMT3A^R882 mutations and the co-occurrence of internal tandem duplication in FMS-like tyrosine kinase 3 (FLT3-ITD), NPM1 mutations, and DNMT3A^R882 mutations (triple mutations) were independent factors predicting a poor prognosis related to OS, with NPM1 mutations being an independent factor for a favorable prognosis (hazard ratios: DNMT3A^R882 mutations, 1.946; triple mutations, 1.992, NPM1 mutations, 0.548). Considering the effects of DNMT3A^R882 mutations and triple mutations on prognosis and according to the classification of NPM1-mutated AML into three risk groups based on DNMT3A^R882/FLT3-ITD genotypes, we achieved the improved stratification of prognosis (p < 0.0001). We showed that DNMT3A^R882 mutations are an independent factor for poor prognosis; moreover, when confounding factors that include DNMT3A^R882 mutations were excluded, NPM1 mutations were a favorable prognostic factor. This revealed that ethnological prognostic discrepancies in NPM1 mutations might be corrected through prognostic stratification based on the DNMT3A status.     

Stromal niche cells protect early leukemic FLT3-ITD+ progenitor cells against first-generation FLT3 tyrosine kinase inhibitors

Targeting constitutively activated FMS-like tyrosine kinase 3 [(FLT3); FLT3-ITD] with tyrosine kinase inhibitor (TKI) in acute myeloid leukemia (AML) leads to clearance of blasts in the periphery but not in the bone marrow, suggesting a protective effect of the marrow niche on leukemic stem cells. In this study, we examined the effect of stromal niche cells on CD34(+) progenitors from patients with FLT3-ITD(+) or wild-type FLT3 (FLT3-WT) AML treated with the TKIs SU5614 or sorafenib. TKIs effectively and specifically inhibited FLT3 and increased the fraction of undivided progenitors in both FLT3-ITD(+) and FLT3-WT samples. Treatment with SU5614 and sorafenib also reduced the number of mature leukemic progenitors, whereas contact with stroma protected against this cell loss. In contrast, primitive long-term progenitors from both FLT3-ITD(+) and FLT3-WT AML were resistant to TKIs. Additional contact with niche cells significantly expanded long-term FLT3-ITD(+) but not FLT3-WT progenitors in the presence of SU5614 but not that of sorafenib. Thus, TKIs with first-generation inhibitors fail to eradicate early leukemic stem/progenitor cells in FLT3-ITD(+) AML. Further, we defined a specific interaction between FLT3-ITD(+) progenitors and niche cells that enables the maintenance of leukemic progenitors in the presence of TKI. Collectively, our findings suggest that molecular therapy may have unpredicted effects on leukemic progenitors, underscoring the necessity of developing strategies to selectively eliminate the malignant stem cell clone.     

急性髓系白血病患者骨髓涂片FMS样酪氨酸激酶3、NPM1和c-kit基因检测及临床研究

目的：探讨提取贮存骨髓涂片DNA的方法,通过对急性髓系白血病（AML）患者FMS样酪氨酸激酶3（FLT3）、NPM1及c-kit基因突变进行检测,分析三种基因突变与AML临床特征之间的关系。方法收集55例AML患者骨髓涂片,采用聚合酶链反应（PCR）、DNA测序和分子克隆方法对FLT3-内部串联重复（ITD）、NPM1和c-kit基因突变进行检测及分析,记录患者疾病缓解、进展及生存时间。结果实验证实对于低温冻存、未经瑞特染色、未用化学方法固定的骨髓涂片标本及室温贮存、经瑞特染色脱色后的标本均能用苯酚∶氯仿∶异戊醇法成功提取DNA。从骨髓涂片中提取的DNA可用于PCR、直接测序和分子克隆测序分析。在55例AML患者中,FLT3-ITD阳性10例（18.2%）,其中9例为杂合型突变,1例为纯合型突变。FLT3-ITD阳性组较阴性组完全缓解（CR）率低,无事件生存（EFS）和总生存（OS）时间短（P＜0.05）。NPM1基因杂合型突变9例（16.4%）,全部为A型突变。10个月以内NPM1突变组患者EFS率比野生组高（P＜0.05）,19个月以内NPM1突变组OS率比野生组高（P＜0.05）。9例NPM1突变患者中FLT3-ITD阳性3例,CR率由高到低依次为NPM1+ FLT3-ITD-、NPM1- FLT3-ITD-、NPM1- FLT3-ITD+、NPM1+ FLT3-ITD+（P＜0.05）,且NPM1- FLT3-ITD+是影响OS的危险因素（RR＝1.250,P＝0.005）。55例患者中,c-kit基因突变2例（3.6%）,分别为D816H突变型和D816V突变型;c-kit基因突变患者与FLT3-ITD阳性及NPM1突变患者无重叠。结论 FLT3-ITD突变为AML患者预后不良的分子标志,NPM1基因突变可能提示预后较好,NPM1- FLT3-ITD+是影响OS的危险因素。AML中c-kit基因突变率低,未见其与FLT3、NPM1基因突变重叠。     

FMS-Like Tyrosine Kinase 3 Inhibitors for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common acute leukemia of adults, with a five-year survival that remains poor (approximately 25%). Knowledge and understanding of AML genomics have expanded tremendously over the past decade and are now included in AML prognostication and treatment decisions. FMS-like tyrosine kinase 3 (FLT3) is a Class III receptor tyrosine kinase (RTK) expressed primarily in the cell membranes of early hematopoietic progenitor cells, found in 28% of all patients with AML. FLT3 is the second most frequent mutation in adult AML following Nuclear-cytoplasmic shuttling phosphoprotein (NPM1), which is found in 50% of cases.¹ FLT3 inhibitors are promising new molecular therapeutics increasingly becoming standard of care for both newly diagnosed and relapsed/refractory FLT3 positive AML. This review will focus on the clinical trials/evidence, similarities, differences, clinical toxicities, and drug interactions relevant to treating clinicians as pertains to 5 FLT3-inhibitors: midostaurin, sorafenib, gilteritinib, crenolanib, and quizartinib.