Tamibarotene: AM 80, retinobenzoic acid, Tamibaro

Tamibarotene [AM 80, retinobenzoic acid, Amnoid, Tamibaro] is a novel synthetic retinoid that is in development with Nippon Shinyaku as a potential treatment for acute promyelocytic leukaemia (APL) and is pending approval in Japan. Tamibarotene was being developed by Shionogi in Japan but the company subsequently discontinued its involvement. Various nonindustrial sources, such as the University of Tokyo, Japan, have also played a role in the development of tamibarotene. Nippon Shinyaku has licensed the rights to tamibarotene from Toko Pharmaceutical Industries for the treatment of acute promyelocytic leukaemia, according to Nippon Shinyaku's June 2004 pipeline update. However it is unclear when Toko Pharmaceutical Industries acquired rights to the compound.     

Arsenic trioxide for management of acute promyelocytic leukemia: current evidence on its role in front-line therapy and recurrent disease

INTRODUCTION: Acute promyelocytic leukemia (APL), the most rapidly fatal leukemia only two decades ago, has been converted into the most frequently curable leukemia by the advent of all-trans retinoic acid (ATRA) and its combination with anthracycline-based chemotherapy. More recently, arsenic trioxide (ATO) has been shown to be the most effective single agent in this disease and has been approved for the treatment of relapsed patients both in the United States and Europe. Moreover, ATO has been included in the design of several front-line studies, with the aim to reduce therapy-related toxicity while maintaining the potential of cure. AREAS COVERED: First, this review briefly discusses the mechanisms of action and the toxicity profile of ATO. Furthermore, the reported experience on the use of ATO as single agent or in combinatorial schemes both in relapsed and in newly diagnosed patients with APL is critically reviewed. Finally, the use of this agent in special subsets of patients unfit to receive conventional chemotherapy is discussed, along with its potential role in maintenance therapy. EXPERT OPINION: While the role of ATO as single agent or in combination with ATRA is well established and recommended by the European LeukemiaNet guidelines as a first option for relapsed patients, the role of the drug in newly diagnosed patients is still uncertain and based only on evidence levels mostly originating from non-randomized trials. The results of ongoing randomized studies should better define the role of ATO in front-line therapy.     

急性早幼粒细胞白血病18例临床分析

目的　探讨急性早幼粒细胞白血病(APL)的临床特点、最佳治疗方案、维A酸综合征(RAS)的防治。方法　分析18例APL患者的临床资料。结果　18例APL患者中以出血起病16例。维A酸联合化疗治疗8例,疗程>6周期2例,分别于第2 6个月、第72个月复发死亡;2例早期死亡;4例<4周期者2例无病生存5年以上,2例于5年后复发,治疗后再次完全缓解。维A酸、砷剂联合化疗治疗10例无病生存2～37个月。结论　APL是一种特殊类型急性白血病,临床以出血为主要症状,RAS以预防为主。     

Granulomatous tubulointerstitial nephritis induced by all-trans retinoic acid

We report the first case of granulomatous tubulointerstitial nephritis induced by all-trans retinoic acid (ATRA) in a patient with acute promyelocytic leukemia (APL). Acute renal failure during treatment with ATRA has been previously reported as a part of an ATRA syndrome or a thrombotic complication of a hypercoagulable state. This case indicates an alternative mechanism of acute renal failure occurring during ATRA therapy.     

Pathogenesis and treatment of leukemia: an Asian perspective

INTRODUCTION: Leukemias occur worldwide, but there are important geographic differences in incidences. AREAS COVERED: Three leukemias with special Asian perspectives, acute promyelocytic leukemia (APL), T-cell large granular lymphocyte (T-LGL) leukemia and NK-cell leukemia. EXPERT OPINION: In APL, China has made contributions in discovering the efficacy of all-trans retinoic acid (ATRA) and arsenic trioxide. Some APL patients are potentially curable after treatment with ATRA or arsenic trioxide as a single agent. Combined treatment of APL with ATRA and arsenic trioxide induces remission with deeper molecular response. An oral formulation of arsenic trioxide is available, making outpatient treatment feasible. Future regimens for APL should examine how ATRA and arsenic trioxide can be optimally combined with other synergistic drugs. Asian patients with T-LGL leukemia present more frequently with pure red cell aplasia, but less frequently with neutropenia, recurrent infection, splenomegaly and rheumatoid arthritis as compared with Western patients. These differences have potential effects on treatment and disease pathogenesis. NK-cell leukemia is rapidly fatal and occurs almost exclusively in Asian and South American patients. Conventional anthracycline-based chemotherapy designed for B-cell lymphomas do not work in NK-cell leukemias. Novel therapeutic approaches targeting cellular signaling pathways or preferentially upregulated genes are needed to improve outcome.     

Arsenic trioxide for management of acute promyelocytic leukemia: current evidence on its role in front-line therapy and recurrent disease

Introduction: Acute promyelocytic leukemia (APL), the most rapidly fatal leukemia only two decades ago, has been converted into the most frequently curable leukemia by the advent of all-trans retinoic acid (ATRA) and its combination with anthracycline-based chemotherapy. More recently, arsenic trioxide (ATO) has been shown to be the most effective single agent in this disease and has been approved for the treatment of relapsed patients both in the United States and Europe. Moreover, ATO has been included in the design of several front-line studies, with the aim to reduce therapy-related toxicity while maintaining the potential of cure.

Areas covered: First, this review briefly discusses the mechanisms of action and the toxicity profile of ATO. Furthermore, the reported experience on the use of ATO as single agent or in combinatorial schemes both in relapsed and in newly diagnosed patients with APL is critically reviewed. Finally, the use of this agent in special subsets of patients unfit to receive conventional chemotherapy is discussed, along with its potential role in maintenance therapy.

Expert opinion: While the role of ATO as single agent or in combination with ATRA is well established and recommended by the European LeukemiaNet guidelines as a first option for relapsed patients, the role of the drug in newly diagnosed patients is still uncertain and based only on evidence levels mostly originating from non-randomized trials. The results of ongoing randomized studies should better define the role of ATO in front-line therapy.     

急性早幼粒细胞白血病46例临床分析

目的：总结46例急性早幼粒细胞白血病（APL）的治疗、预后及不良反应,以达到提高缓解率,延长生存期的目的。方法：对46例APL患者治疗期间应用全反式维甲酸、亚砷酸、DA/MA/HA及复方黄黛片进行联合治疗。结果：本组46例APL患者除2例早期死亡外,其余44例均达到完全缓解（CR）,CR率为95.7%。结论：应用全反式维甲酸、亚砷酸及复方黄黛片联合治疗APL是安全有效的,对初治或复发患者均具有疗效高、耐受性好的特点。     

Regulation of CYP26A1 expression by selective RAR and RXR agonists in human NB4 promyelocytic leukemia cells

All-trans retinoic acid (ATRA) can induce complete remission in acute promyelocytic leukemia (APL), but resistance to this treatment develops rapidly partly due to increased ATRA metabolism. Among the cytochrome P450s (CYPs) involved in ATRA metabolism, the ATRA-inducible cytochrome P450 26A1 (CYP26A1) is particularly active although the molecular mechanisms involved in its regulation are not well defined in the target leukemia cells. To study CYP26A1 expression and regulation in APL cells, we used the NB4 promyelocytic leukemia cell line. CYP26A1 constitutive expression was barely detectable in NB4 cells, but ATRA could induce high levels of CYP26A1 expression, which reached a maximum at 72h. To further define CYP26A1 induction mechanisms in the NB4 leukemia cells, we used RARs and RXR selective agonists. The RARalpha agonist BMS753 could elicit maturation, as expected, but not CYP26A1 expression. Treatment with the RARbeta agonist BMS641, or the RARbeta/gamma agonist BMS961, could not elicit maturation, as expected, nor induce CYP26A1 expression. Because CYP26A1 expression could not be induced by RAR ligands alone, NB4 cells were then co-treated with the RXR agonist BMS649. The RXR agonist alone could not induce CYP26A1 expression, nor in combination with either the RARbeta agonist or the RARbeta/gamma agonist. However, the combination of the RXR agonist and the RARalpha agonist could elicit a marked induction of CYP26A1 expression. In conclusion, we have shown that CYP26A1 induction is not essential for the granulocytic maturation of NB4 leukemia cells, and that CYP26A1 induction requires the activation of both RARalpha and RXR in these cells.     

全反式维甲酸与亚砷酸联合化疗对急性早幼粒细胞白血病高危患者的疗效

目的观察全反式维甲酸(ATRA)与亚砷酸(ATO)联合化疗对急性早幼粒细胞白血病(APL)患者的疗效。方法回顾性分析86例不同危险分级的初治APL患者的临床资料。根据治疗前白细胞和血小板数将APL患者分为低、中、高危三组。采用ATRA+ATO+蒽环类药诱导缓解,蒽环类药+阿糖胞苷巩固治疗,ATRA+ATO+甲氨蝶呤(MTX)[部分加用6-巯基嘌呤(6-MP)]维持治疗。结果治疗后,完全缓解(CR)率高达95.3%(82/86)。中位随访37个月,高危组和中低危组无事件生存率及中枢神经系统累积复发率差异均无统计学意义(P>0.05)。维持治疗单用MTX者或MTX+6-MP者CR率均为100%。结论 APL患者尤其是高危患者可以从ATO+ATRA+化疗中受益;该方案作为初治APL的一线治疗方案优势明显。     

全反式维甲酸和三氧化二砷治疗初治急性早幼粒细胞白血病的疗效观察

目的观察全反式维甲酸(ATRA)联合三氧化二砷(As2O3)治疗初治急性早幼粒细胞白血病(APL)的疗效。方法对应用ATRA和As2O3联合诱导治疗的20例APL患者的完全缓解(CR)率、达CR所需时间和不良反应进行观察,并与单独应用ATRA组30例进行比较。联合用药组治疗方法为ATRA 25mg/(m2.d),0.1%As2O310ml/d直至CR。结果联合用药组与单独应用ATRA组相比,CR率差异无统计学意义(分别为95%、86.7%,均P>0.05);联合用药组获得CR所需的时间短于单独用药组(平均时间分别为24d、45d,均P<0.05),早期死亡率较单独用药组差异无统计学意义(分别为5%、13.3%,均P>0.05);与单独用药组相比,联合用药组的不良反应并未增加。结论联合用药诱导初发APL缓解的疗效优于单用药组,不良反应少,是一种值得推广应用的方案。     

Arsenic trioxide in hematological malignancies: the new discovery of an ancient drug

Currently, Arsenic Trioxide (ATO) is considered the treatment of choice for patients with relapsed acute promyelocytic leukemia (APL). Recently, a durable remission with minimal toxicity by single agent ATO or ATO + ATRA in newly diagnosed APL was reported by different groups. These regimens have minimal toxicity and can be administered on an outpatient basis after remission induction, thus they could become a real, less toxic and more economic option to ATRA + anthracyclines in particular in low risk APL, or in patients that cannot undergo chemotherapy because of age or comorbid conditions and in patients that refuse chemotherapy. Significantly, these therapies are a successful attempt to cure a tumoral disease without chemotherapy. The results of clinical trials of ATO administration as single agent in multiple myeloma (MM) and myelodisplastic syndromes (MDS) were encouraging and showed clinical effects but they were not close to APL success. On the contrary, results of clinical trials to treat non-APL acute myeloid leukemia (AML) were disappointing. We suggest that a combination therapy with drugs targeting specific pro-survival molecules or capable to enhance pro-apoptotic pathways may lead to an improvement of ATO efficacy against hematological malignancies, in particular AML. Our pre-clinical studies showed that ATO is capable to induce cell death in acute leukemia cells but the apoptotic function is limited since it can induce also a mechanism of cell defense by activating pro-survival molecules such as MEK-ERK, Bcl-xL, Bcl-2. By combining ATO with specific MEK inhibitors, we demonstrated that the block of MEK-ERK phosphorylation, the induction of Bad de-phosphorylation, and activation of p53AIP1 apoptotic pathway interrupt the pro-survival mechanisms of ATO and kill the leukemic cells by apoptotic synergism. Our results provide an experimental basis for combined or sequential treatment with MEK inhibitors and ATO in AML. The renaissance of ATO as a drug in moderne medicine may be considered, together with ATRA success, a victory of empirical analysis, that had (and has) great impact on Chinese culture.     

三氧化二砷联合全反式维甲酸治疗初发急性早幼粒细胞白血病临床分析

目的三氧化二砷联合全反式维甲酸治疗初发急性早幼粒细胞白血病的临床疗效(即完全缓解率和融合基因PML-RARα转阴情况)及不良反应。方法 46例初发APL患者随机分成研究组予As2O3联合ATRA治疗24例,对照组仅予ATRA治疗22例,均治疗直至CR。根据外周血白细胞计数、维甲酸综合征以及肝功能变化调整两药物的剂量。观察CR率、获得CR和不良反应。结果 46例初发APL患者,ATRA联合As2O3组24例患者中,CR23例,1例未缓解,缓解率95.8%,ATRA单药组22例患者中,CR17例,5例未缓解,缓解率77.3%。两组间CR率差异有统计学意义。65.0%患者在治疗开始后出现白细胞升高,63.8%出现肝功能异常,多在减量或停用后1周内恢复。所有患者融合基因PML-RARα初发时均为阳性,CR时9.8%转阴。结论 As2O3联合ATRA治疗初发APL疗效好,不良反应少。长期完全缓解时间需要进一步观察。     

Biodistribution characteristics of all-trans retinoic acid incorporated in liposomes and polymeric micelles following intravenous administration

The aim of this study was to investigate the biodistribution characteristics of all-trans retinoic acid (ATRA) incorporated in liposomes and polymeric micelles following intravenous administration. [3H] ATRA were incorporated in distearoylphosphatidylcholine (DSPC)/cholesterol (6:4) liposomes. Two types of block copolymers, poly (ethylene glycol)-b-poly-(aspartic acid) derivatives with benzyl (Bz-75) groups, were synthesized to prepare the polymeric micelles for [(3)H]ATRA incorporation. ATRA were dissolved in mouse serum to analyze their inherent distribution. After intravenous administration, the blood concentration of [3H] ATRA in liposomes and polymeric micelles (Bz-75) was higher than that of inherent [3H]ATRA, suggesting that liposomes and polymeric micelles (Bz-75) control the distribution of ATRA. Pharmacokinetic analysis demonstrated that [3H]ATRA incorporated in polymeric micelles (Bz-75) exhibit the largest AUC(blood) and lowest hepatic clearance of ATRA, suggesting that polymeric micelles (Bz-75) are an effective ATRA carrier system for acute promyelocytic leukemia (APL) therapy. These results have potential implications for the design of ATRA carriers for APL patients.     

全反式维甲酸-正丁酸（丙戊酸）前体药物的设计、合成及抗肿瘤活性研究

目的合成全反式维甲酸（ATRA）的前体药物，增强ATRA对急性早幼粒白血病（APL）细胞的分化诱导作用。方法以乙二醇、对苯二酚、乙醇胺及乙二胺等为连接物，通过酯键和酰胺键将分化诱导剂ATRA与组蛋白去乙酰酶（mAC）抑制剂正丁酸、丙戊酸连接起来，形成前体药物。结果合成了13个ATRA与正丁酸或丙戊酸相连接的前体药物，化合物的结构经^1H-NMR、MS和IR确证。结论考察部分化合物对急性早幼粒细胞白血病细胞株NB4的生长抑制作用和对急性早幼粒白血病（APL）细胞分化诱导作用，初步的药理实验结果表明，ATRA与丙戊酸通过酰胺键连接时，对NB4细胞分化诱导能力显著增加。     

Kinetic study of a 2-hydroxypropyl-beta-cyclodextrin-based formulation of all-trans-retinoic acid in Sprague-Dawley rats after oral or intravenous administration

all-trans-Retinoic acid (ATRA, vitamin A acid, or tretinoin) is a potent chemotherapeutic agent for the treatment of acute promyelocytic leukemia (APL). Its poor aqueous solubility not only affects its oral absorption but also prevents it from forming an aqueous parenteral formulation. Recently, we developed a water-soluble formulation of ATRA with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD). In present study, this formulation was tested in Sprague-Dawley rats. Kinetic study of ATRA was carried out after oral or intravenous administration. Though there were no statistical differences in any of the estimated pharmacokinetic parameters between ATRA sodium salt and HPbetaCD-based ATRA after intravenous administration, inclusion of ATRA into HPbetaCD was found to greatly improve the oral absorption of ATRA.     

Differential expression of dendritic cell markers by all-trans retinoic acid on human acute promyelocytic leukemic cell line

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) for naive T cells and play an important role in cancer immunology. All-trans retinoic acid (ATRA) is known to be a differentiating agent in the treatment of acute promyelocytic leukemia (APL). In this study, we investigated whether ATRA can differentiate the retinoic acid (RA)-sensitive promyelocytic leukemic cell line, NB4, to DC-like cells and whether these differentiated cells can activate T cells. NB4 cells were differentiated to myeloid cells by 4, 6, and 8 days of ATRA treatment. NB4 cells up-regulated markers found in DCs, including HLA-DR, costimulatory molecules (CD80 and CD86), adhesion molecules (CD40), and chemokine receptors (CCR6) when cultured for 8 days in the presence of 1 microM ATRA. Upregulation of CD83 was also detected on the surface of ATRA-treated NB4 cells versus untreated cells. The addition of cytokines alone, such as GM-CSF or CD40 ligand, did not affect the expression of CD83 in untreated NB4 cells but they up-regulated CD83 in ATRA-treated cells. CD11b was coexpressed with CD80, CD83, and CD86 in ATRA-treated NB4 cells. In a functional assay, ATRA-treated NB4 cells stimulated T cell proliferation when challenged with Staphylococcus enterotoxin B. These results suggest that the differentiation of NB4 cells by ATRA causes the cells to express DC markers, and that ATRA-differentiated NB4 cells are able to present antigens to T cells.