急性髓系白血病患者FLT3表达及TKD点突变的研究

  目的 研究急性髓系白血病（AML）患者与正常人FMS样酷氨酸激酶3（FLT3）基因在骨髓中表达的差异以及FLT3基因酪氨酸激酶结构域（TKD）点突变与AML的关系。方法 将AML初治患者和正常人的骨髓分别用CD135抗体标记后，应用三色流式细胞术检测并分析；采用RT-PCR结合限制性内切酶酶切，检测30例AML初治患者FLT3基因的TKD点突变。结果 AML患者骨髓中CD135阳性率均＞20 ％，而正常人＜2 ％，二者差异有统计学意义（P＜0.05）；另外，30例AML患者中3例存在FLT3-TKD点突变，阳性率为10 ％，其中2例化疗后完全缓解（CR），缓解率66.7 ％，其他27例非点突变患者化疗后完全缓解率为84 ％，二者比较差异无统计学意义（P＞0.05）。结论 AML患者骨髓中FLT3基因表达显著高于正常人。AML患者FLT3-TKD点突变的阳性率为10 ％左右，FLT3-TKD点突变对患者化疗后CR率的影响有待进一步研究。     

Inhibition of mutant FLT3 receptors in leukemia cells by the small molecule tyrosine kinase inhibitor PKC412

Constitutively activating FLT3 receptor mutations have been found in 35% of patients with acute myeloblastic leukemia (AML). Here we report the identification of a small molecule FLT3 tyrosine kinase inhibitor PKC412, which selectively induced G1 arrest and apoptosis of Ba/F3 cell lines expressing mutant FLT3 (IC(50) < 10 nM) by directly inhibiting the tyrosine kinase. Ba/F3-FLT3 cell lines made resistant to PKC412 demonstrated overexpression of mutant FLT3, confirming that FLT3 is the target of this drug. Finally, progressive leukemia was prevented in PKC412-treated Balb/c mice transplanted with marrow transduced with a FLT3-ITD-expressing retrovirus. PKC412 is a potent inhibitor of mutant FLT3 and is a candidate for testing as an antileukemia agent in AML patients with mutant FLT3 receptors.     

In vivo activity of ABT-869, a multi-target kinase inhibitor, against acute myeloid leukemia with wild-type FLT3 receptor

Neoangiogenesis plays an important role in leukemogenesis. We investigated the in vivo anti-leukemic effect of ABT-869 against AML with wild-type FLT3 using RFP transfected HL60 cells with in vivo imaging technology on both the subcutaneous and systemic leukemia xenograft models. ABT-869 showed a five-fold inhibition of tumor growth in comparison with vehicle control. IHC analysis revealed that ABT-869 decreased p-VEGFR1, Ki-67 labeling index, VEGF and remarkably increased apoptotic cells in the xenograft models. ABT-869 also reduced the leukemia burden and prolonged survival. Our study supports the rationale for clinically testing an anti-angiogenesis agent in AML with wild-type FLT3.     

The kinase inhibitor LS104 induces apoptosis, enhances cytotoxic effects of chemotherapeutic drugs and is targeting the receptor tyrosine kinase FLT3 in acute myeloid leukemia

Activating mutations of FLT3 are found in approximately one-third of acute myeloid leukemia (AML)-cases and are considered to represent an attractive therapeutic target. In this study, we report that the hydroxystyryl-acrylonitrile compound LS104 inhibits proliferation and induces potent cytotoxic effects in FLT3 expressing leukemic cells in vitro. Immunoblot and phosphoprotein-FACS analysis demonstrated inhibiton of phosphorylation of FLT3-ITD and of its downstream targets. In pharmacokinetic studies, a rapid and dose dependent cellular uptake of LS104 lasting up to 11h could be demonstrated. Combination of LS104 with chemotherapeutic agents markedly enhanced cytotoxic effects. Recently, a phase I clinical trial investigating LS104 in refractory/relapsed hematologic malignancies has been initiated.     

Phase I dose-escalating study of SU11654, a small molecule receptor tyrosine kinase inhibitor, in dogs with spontaneous malignancies.

PURPOSE: The purpose of the following study was to investigate the safety and efficacy of the novel multitargeted indolinone receptor tyrosine kinase (RTK) inhibitor, SU11654, using a canine model of spontaneous tumors. This p.o. bioavailable compound exhibits potent inhibitory activity against members of the split kinase family of RTKs, including vascular endothelial growth factor receptor, platelet-derived growth factor receptor, Kit, and Flt-3, resulting in both direct antitumor and antiangiogenic activity. EXPERIMENTAL DESIGN: This was a Phase I trial in which successive cohorts of dogs with spontaneous tumors that had failed standard treatment regimens received escalating doses of SU11654 as oral therapy. Pharmacokinetics, toxicity, and tumor response were assessed. RESULTS: Fifty-seven dogs with a variety of cancers were enrolled; of these, 10 experienced progressive disease within the first 3 weeks. Measurable objective responses were observed in 16 dogs (including 6 complete responses), primarily in mast cell tumors (n = 11), mixed mammary carcinomas (n = 2), soft tissue sarcomas (n = 2), and multiple myeloma (n = 1), for an overall response rate of 28% (16 of 57). Stable disease of sufficient duration to be considered clinically meaningful (>10 weeks) was seen in an additional 15 dogs, for a resultant overall biological activity of 54% (31 of 57). CONCLUSIONS: This study provides the first evidence that p.o. administered kinase inhibitors can exhibit activity against a variety of spontaneous malignancies. Given the similarities of canine and human cancers with regard to tumor biology and the presence of analogous RTK dysregulation, it is likely that such agents will demonstrate comparable antineoplastic activity in people.     

Soluble phosphorylated fms-like tyrosine kinase III. FLT3 protein in patients with acute myeloid leukemia (AML)

FLT3 ligand (FL) has a significant role in the proliferation and differentiation of hematopoietic cells. Mutations in the FLT3 receptor gene have been reported in 30% of patients with AML. We investigated whether abnormal phosphorylation of FLT3 may be more common in AML. We evaluated FLT3 protein and its phosphorylation in the plasma from 85 patients with AML, 16 patients with myelodysplastic syndrome (MDS) and 5 patients with acute lymphoblastic leukemia (ALL). There were no significant differences in the level of plasma FLT3 protein level in the different diseases (p=0.57). AML patients had a significantly higher level of phospho-FLT3:FLT3 ratio (p=0.02). FLT3-ITD and FLT3 point mutations were present in 27 (32%) of the AML patients. Phosphorylated FLT3 was significantly higher in the plasma from patients with FLT3 mutation (p=0.002). Overall, there was no correlation between survival and the plasma level of FLT3 protein or its phosphorylated form. However, amongst the patients without FLT3 mutations, those with a higher level of phosphorylated FLT3 had a significantly shorter duration of remission (p=0.04). Other mechanisms may be responsible for abnormal phosphorylation of FLT3 and inhibitors of FLT3 should also be investigated in patients without mutations.     

Downregulation of VEGF-A, STAT5 and AKT in acute myeloid leukemia blasts of patients treated with SU5416

In acute myeloid leukemia (AML), autocrine or paracrine activation of receptor tyrosine kinases such as c-kit and FLT3 contributes to proliferation and apoptosis resistance of leukemic blasts. This provided the rationale for a multicenter clinical trial in patients with refractory AML with SU5416, a small molecule kinase inhibitor which blocks phosphorylation of c-kit, FLT3, VEGFR-1, VEGFR-2 (KDR) and VEGFR-3. The levels of VEGF mRNA expression were investigated in peripheral blood leukemic blasts taken from AML patients before and during treatment with SU5416. Rapid down regulation of VEGF was observed in AML blasts from 72% (13 of 18) of patients analysed. Patients initially expressing high VEGF-levels had a stronger downregulation and a higher clinical response rate (mean 865-fold, n = 10, P = 0,01) than patients initially expressing low VEGF-levels (mean four-fold, n = 8). These results suggest that abnormal high VEGF expression is downregulated by SU5416 treatment, and furthermore that decreases in VEGF mRNA levels may provide an early marker of therapeutic response with anti-angiogenic therapy. Additionally, protein expression of STAT5 and AKT was assessed by western blotting in these patient samples, as well as in the leukemia cell line, M-07e, treated in vitro with SU5416 as a model system. In the AML patient samples, parallel downregulation of both STAT5 and AKT was observed in several cases (STAT5 in four of 15; AKT in three of six examined patients). These effects were confirmed with the cell line M-07e after incubation with SU5416 in vitro using concentrations that are achievable in patients. In summary, our data show suppression of the expression of VEGF and key signal transduction intermediates in AML blasts during treatment with SU5416.     

FLT3 kinase inhibitors in the management of acute myeloid leukemia

FMS-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase (TK) expressed by immature hematopoietic cells and is important for the normal development of stem cells and the immune system. Mutations of the juxtamembranous and TK domain of the gene are described in 30%-35% of patients with acute myeloid leukemia (AML). These mutations alter the biologic properties of AML and are associated with prognosis. In recent years, there has been an enormous development of potential inhibitors of FLT3 mutations. These substances are now being studied in clinical protocols. The initial trials reveal that, unlike in patients with chronic myeloid leukemia, TK inhibitor (TKI) therapy in AML is more complex. To date, most FLT3 TKIs investigated in clinical studies show a favorable toxicity profile with considerable biologic activity. However, refractory disease and/or the rapid development of resistance toward these new drugs remain major challenges. Strategies to circumvent this unsatisfactory clinical potential of FLT3 TKIs are mainly based on the combination with cytotoxic chemotherapy. Herein, we summarize results from studies using FLT3 TKIs as single agents and report on the first clinical trials investigating FLT3 TKIs in combination with chemotherapy.     

Pregnancies in patients with chronic myeloid leukemia treated with tyrosine kinase inhibitor

We presented our experience in chronic myeloid leukemia (CML) patients who conceived children and/or became pregnant while receiving tyrosine kinase inhibitor (TKI). Among 7 male patients, 7 pregnancies resulted in the birth of 7 healthy babies. Among 18 female patients, 8 ended in elective abortion; 3 had spontaneous abortion, and 7 carried to term, resulting in the birth of 8 healthy babies. All children have normal growth and development. All patients remain in TKI therapy and in good response. It is suggested that female patients are advised to practice adequate contraception. No special precautions apply for male patients receiving TKI.     

Phase 1 study of PTK787/ZK 222584, a small molecule tyrosine kinase receptor inhibitor, for the treatment of acute myeloid leukemia and myelodysplastic syndrome.

PTK787/ZK 222584 (PTK/ZK) is an oral angiogenesis inhibitor targeting vascular endothelial growth factor (VEGF) receptor tyrosine kinases, including VEGFR-1/Flt-1, VEGFR-2/KDR, VEGFR-3/Flt-4, the platelet-derived growth factor receptor tyrosine kinase and the c-kit protein tyrosine kinase. The objective of this Phase I study was to evaluate the safety, tolerability, biologic activity and pharmacologic profile of PTK/ZK administered orally, twice daily, on a continuous dosing schedule in patients with primary refractory or relapsed acute myeloid leukemia (AML), secondary AML, poor-prognosis de novo AML or advanced myelodysplastic syndrome (MDS). Acute myeloid leukemia patients for whom PTK/ZK monotherapy was ineffective could receive PTK/ZK combined with standard induction chemotherapy. Sixty-three patients received PTK/ZK at doses of 500-1000 mg orally b.i.d. Safety and pharmacokinetic data were collected. Responses were evaluated according to standard bone marrow and peripheral blood criteria. At 1000 mg b.i.d., dose-limiting toxicities of lethargy, hypertension, nausea, emesis and anorexia were observed. Other adverse events related to PTK/ZK were dizziness, weakness, fatigue, diarrhea and pruritus; these were generally mild and reversible. Pharmacokinetic data showed that steady state was reached by day 14, there was no accumulation with repeat dosing and there was no significant increase in exposure at steady state beyond the maximum tolerated dose (MTD). Complete remission was observed in five of 17 AML patients treated with PTK/ZK combined with chemotherapy.In conclusion, the MTD of PTK/ZK is 750 mg orally b.i.d. The drug is generally well tolerated and can be given in combination with chemotherapy for patients with MDS and AML.     

Gilteritinib versus chemotherapy in Japanese patients with FLT3-mutated relapsed/refractory acute myeloid leukemia

Background

Until recently, no effective targeted therapies for FLT3-mutated (FLT3^mut+) relapsed/refractory (R/R) acute myeloid leukemia (AML) were available in Japan. The FLT3 inhibitor, gilteritinib, was approved in Japan for patients with FLT3^mut+ R/R AML based on the phase 3 ADMIRAL trial, which demonstrated the superiority of gilteritinib over salvage chemotherapy (SC) with respect to overall survival (OS; median OS, 9.3 vs 5.6 months, respectively; hazard ratio, 0.64 [95% confidence interval 0.49, 0.83]; P?<?0.001).

Methods

We evaluated the Japanese subgroup (n?=?48) of the ADMIRAL trial, which included 33 patients randomized to 120-mg/day gilteritinib and 15 randomized to SC.

Results

Median OS was 14.3 months in the gilteritinib arm and 9.6 months in the SC arm. The complete remission/complete remission with partial hematologic recovery rate was higher in the gilteritinib arm (48.5%) than in the SC arm (13.3%). After adjustment for drug exposure, fewer adverse events (AEs) occurred in the gilteritinib arm than in the SC arm. Common grade?≥?3 AEs related to gilteritinib were febrile neutropenia (36%), decreased platelet count (27%), and anemia (24%).

Conclusion

Findings in Japanese patients are consistent with those of the overall ADMIRAL study population.

     

Finding the next Gleevec: FLT3 targeted kinase inhibitor therapy for acute myeloid leukemia

Activating mutations in the FLT3 receptor tyrosine kinase occur in 30% of patients with acute myeloid leukemia. Small molecule FLT3 kinase inhibitors show selective antitumor activity in preclinical models. Clinical studies are underway.     

急性髓系白血病患者外周血细胞中FLT3基因表达与FLT3／ITD突变的关系及其意义

背景与目的：研究表明FLT3／ITD突变的急性髓性白血病（acutemyeloid leukemia,AML）患者预后差,但关于AML患者FLT3基因的表达水平在预后中的作用及其与FLT3／ITD突变关系的研究尚不充分。本研究探讨初治AML患者FLT3基因的表达水平与FLT3／ITD突变的关系及其临床意义。方法：建立实时荧光定量PCR检测FLT3基因表达水平及PCR检测FLT3／ITD突变的方法。分析79例初治AML患者FLT3基因水平、FLT3／ITD突变及与预后的关系。结果：22．7％（18／79）的AML患者存在FLT3／ITD突变。92．4％（73／79）的患者标本中可检测到FLT3基因表达,FLT3基因表达水平为0-7320,中位数为312,正常对照组未检测到FLT3基因的表达。FLT3基因高表达及FLT3／ITD突变AML组的白细胞计数及骨髓白血病细胞均显著高于低表达和无突变AML组（P〈0．05）。FLT3基因高表达的AML组FLT3／ITD突变率（25．6％）同低表达的AML组（20．0％）相比,差异无统计学意义（P〉0．05）,FLT3／ITD突变AML患者FLT3基因表达中位数与无突变组比较差异也无统计学意义。FLT3／ITD突变组的完全缓解率（58．8％）显著低于无FLT3／ITD突变组（82．1％）（P〈0．05）;FLT3基因高表达AML组FLT3／ITD的完全缓解率（68．6％）同低表达AML组（84．2％）相比差异无统计学意义（P〉0．05）,但无FLT3／ITD突变组中,FLT3基因高表达组完全缓解率（69．2％）显著低于低表达组（93-3％）（P〈0．05）。结论：FLT3高表达与FLT3／ITD突变之间无明显相关性,FLT3高表达对于无FLT3／ITD突变AML患者可能是一个预后不良的指标。     

Clinical relevance of FLT3 receptor protein expression in Indian patients with acute leukemia

Aim: FLT3 is a receptor tyrosine kinase that plays an important role in the pathogenesis of leukemia. The present study aimed to evaluate the role of FLT3 protein in patients with acute leukemia. Method: FLT3 protein was quantified by flow cytometry on leukemic blasts using CD135 antibody in 160 patients with acute leukemia. Results: We demonstrated FLT3 protein expression (>20%) in 82% of acute myeloid leukemia (AML), 60% of B‐lineage acute lymphoblastic leukemia (B‐ALL), 23% of T‐lineage acute lymphoblastic leukemia (T‐ALL) and 80% of biphenotypic leukemia. Further, FLT3 expression was seen to be significantly higher in AMLM2, M4, and M5 than in AMLM3. In B‐ALL, FLT3 was found to be higher in pro‐B‐ALL and lower in early B‐ALL. A CD34 expression >20% was associated with FLT3 positive B‐ALL. When correlated with disease status, all patients in the relapsed AML group had FLT3 > 20% at diagnosis. Unlike AML, the relapsed group of B‐ALL showed a lower incidence of FLT3 than the remission group. Conclusion: In summary, our data imply that there is frequent overexpression of the FLT3 protein in AML and B‐ALL patients of Indian origin. In future, the FLT3 protein level may be used to select patients for whom FLT3 inhibitor therapy may be indicated.