New nucleoside analogs in the treatment of solid tumors

Physiologic deoxynucleotides are required for an error-proof DNA replication, repair and synthesis. Any inaccuracy in this process results in a block in DNA synthesis until the error is corrected. If the cell enzymes are unable to correct the error, a signal for apoptosis is generated. This mechanism is the main target for anticancer nucleoside analogs. They also interact with the metabolism of physiological nucleosides, and consequently, have a large number of intracellular targets to induce cytotoxicity. In addition, it is now reported that some analogs may interfere directly with RNA synthesis. A great deal of synthesized nucleoside analogs provide the opportunity to understand the structure-based differences in their metabolism and mechanisms of action as well as to identify the specific intracellular targets and diseases, in which each of these newer nucleoside analogs acts most efficiently. This paper summarizes developments in the area of new nucleoside analogs undergoing clinical evaluation for the treatment of solid tumors, namely tezacitabine, troxacitabine, DMDC, CNDAC, ECyD, clofarabine, and decitabine.     

The place of somatostatin analogs in the diagnosis and treatment of the neuoroendocrine glands tumors

Somatostatin (SS) was originally discovered as a hypothalamic neurohormone which inhibits growth hormone secretion. The synthesis of the first two metabolically stabilized and more potent SS analogs, octreotide and lanreotide leads to the establishment of applications for them and to introduction into routine therapies. The effectiveness of octreotide or lanreotide in controlling symptoms and GH/IGF-I hypersecretion in acromegalic patients, both preoperatively and postoperatively is well proven. Similarly, these drugs are also very effective in the treatment of TSH-secreting adenomas. The introduction of these drugs into therapy of the functional neuroendocrine tumors of the gastrointestinal tract was a crucial step in the treatment. Octreotide and lanreotide are the drugs of choice in the treatment of patients with: VIPoma, glucagonoma and carcinoid syndrome. Somatostatin receptor scintigraphy with OctreoScan has been recommended as the best imaging technique in these tumors in the localization and staging procedure. SS analogs, coupled to radioisotope or cytotoxic drugs, create another class of SS molecules, very promising in the therapy of the endocrine glands tumors and in other tumors. Another class of SS analogs comprises hybrid molecules, which are chimera of sst2 agonist and D2 agonist, possessing more potent activity than these agonists, applied together.     

Monoclonal antibodies in the management of solid tumors

Thorough understanding of the complex interactions between components of immunological response has led to the arousal of the concept of immune-mediated anti-cancer therapy. Although, the use of monoclonal antibodies (MAbs) in hematological malignancies met with success, therapy of solid tumors has been impeded by many obstacles. Some MAbs have increased the efficacy of treatment of certain tumors with acceptable adverse events. Trastuzumab, cetuximab and bevacizumab have become FDA approved for the treatment of breast and colorectal cancer, respectively. The dosing strategies, timing and schedule of antibody administration, duration of treatment are yet to be determined under specific circumstances. Combinations with other biologic agents, such as small-molecule inhibitors of the same pathway would be really useful. Multimodality approaches are based on synergistic effects observed with the combination of antibodies with chemotherapeutic drugs and/or radiotherapy. Immune-mediated effects may be further exploited with the use of bivalent (bispecific) molecules, while radioimmunotherapy via radiolabelling of the antibody is feasible. Modified recombinant antibodies could be applied for toxin delivery to tumor cells, while molecules fused with drug-activating enzymes can mediate prodrug therapy. Increased penetrability into tumors can also be achieved with novel antibody fragments. In the future, better selection of patient subpopulations with tumors overexpressing disease-related clinical biomarkers could result in an increase in both efficacy and specificity of antibody-based treatment.     

Conformational modifications of cyclic hexapeptide somatostatin analogs

A model for the bioactive conformation of the highly active cyclic hexapeptide somatostatin analog cyclo-(Pro-Phe-d -Trp-Lys-Thr-Phe) has been proposed. As a test of this model, several compounds containing lactam and N-Me amino acid conformational modifications in the Thr-Phe-Pro-Phe beta turn were synthesized. The N-Me alanine and sarcosine substitutions for proline gave highly active analogs, while lactam dipeptides in place of Phe-Pro decreased potency. ¹H n.m.r. and CD spectra of these analogs illustrate the conformational effects in solution of these modifications. The results provide additional support for the proposed conformational model.     

Belinostat: clinical applications in solid tumors and lymphoma

Introduction: Histone deacetylase (HDAC) inhibitors have recently emerged as a novel and active class of anticancer agents. Belinostat is one member of the class that has been tested as a single agent and in combination with other chemotherapies and biological agents in the treatment of solid tumors and lymphoma.

Areas covered: A literature search of pre-clinical and clinical studies of belinostat was performed. The data from these studies were analysed to summarise the progress of belinostat from Phase I to a current pivotal trial in peripheral T-cell lymphoma. The parallel development of appropriate biomarker analysis is also discussed.

Expert opinion: Belinostat has demonstrated significant clinical activity in T-cell lymphomas. Although its activity as a single agent in solid tumors has been less compelling, the emerging results from combination trials are promising. However, the basis for the activity of belinostat, like that of other HDAC inhibitors, remains to be truly defined and the identification of predictive and prognostic biomarkers of activity should be established to further progress the development of this compound.     

Belinostat: clinical applications in solid tumors and lymphoma

INTRODUCTION: Histone deacetylase (HDAC) inhibitors have recently emerged as a novel and active class of anticancer agents. Belinostat is one member of the class that has been tested as a single agent and in combination with other chemotherapies and biological agents in the treatment of solid tumors and lymphoma. AREAS COVERED: A literature search of pre-clinical and clinical studies of belinostat was performed. The data from these studies were analysed to summarise the progress of belinostat from Phase I to a current pivotal trial in peripheral T-cell lymphoma. The parallel development of appropriate biomarker analysis is also discussed. EXPERT OPINION: Belinostat has demonstrated significant clinical activity in T-cell lymphomas. Although its activity as a single agent in solid tumors has been less compelling, the emerging results from combination trials are promising. However, the basis for the activity of belinostat, like that of other HDAC inhibitors, remains to be truly defined and the identification of predictive and prognostic biomarkers of activity should be established to further progress the development of this compound.     

Adverse events associated with somatostatin analogs in acromegaly

Introduction: In patients with acromegaly, somatostatin analogs (SSA) represent the first choice medical treatment. The long-acting SSA have been found to be effective in controlling growth hormone and IGF-I levels in a high percentage of patients, resulting in an improvement in the quality of life; moreover, these peptide analogs have a proven safety record and are generally well tolerated.

Areas covered: The most commonly reported adverse events include injection-site discomfort and erythema, gastrointestinal (GI) disturbances such as diarrhea, abdominal pain, nausea and vomiting, biliary sludge or gallstones, and abnormal glucose metabolism. Most SSA-related adverse events are transient and of mild-to-moderate intensity, and the prevalence of such effects markedly and progressively decreases during treatment, so that treatment discontinuations due to adverse events are rare and commonly related to GI disturbances. Cholelithiasis represents the most serious complication of SSA, but is generally asymptomatic, and has been reported in 3 – 56% of patients. Whereas the effect of SSA on glucose metabolism is still controversial, several pieces of evidence have confirmed a modest and transient negative impact on glucose homeostasis. Also the novel SSA pasireotide has shown a safety profile as expected for a SSA, except for the degree of hyperglycemia.

Expert opinion: On the basis of these findings, a close and careful monitoring of gallbladder ultrasound and glucose levels is recommended in patients receiving SSA for medical treatment of acromegaly.     

Synthesis of somatostatin analogs resistant to the action of trypsin

The synthesis of a series of octapeptides based on the somatostatin analog cyclo(-Asn-Phe-Phe-d -Trp-Lys-Thr-Phe-Gaba-) containing the substitutions [Aap⁹], [d -Lys⁹], [l -Trp⁸, d -Lys⁹], [l -Orn⁹] and [d -aThr¹⁰] is reported. The analogs were designed and have been shown to inhibit proteolysis at the proposed (1) primary cleavage site between Lys⁹-Thr¹⁰ and thereby increase their stability to enzymic attack.     

沙尔威辛治疗恶性肿瘤Ⅰ期临床耐受性试验

目的观察沙尔威辛治疗恶性肿瘤的安全性,毒副反应与剂量的关系,确定推荐Ⅱ期临床研究的剂量.方法共入选29例患者,沙尔威辛分为9个剂量组,由初始剂量15 mg·m-2·d-1开始逐渐增加至30,45,60,75,90,105 mg·m-2·d-1,加入生理氯化钠溶液500 mL静脉点滴2 h,连续3 d,其中第7剂量组为90 mg·m-2·d-1连续4 d,第8剂量组为90 mg·m-2·d-1连续5 d,第9剂量组为105 mg·m-2·d-1连续5 d,21 d为一周期,每剂量组3或4例.观察药物对人体各系统的影响及毒性反应.结果沙尔威辛的毒副反应比较轻微,除了血管刺激疼痛外主要还包括Ⅰ/Ⅱ度的骨髓抑制、消化道反应、发热及皮肤潮红等,所有的毒副反应均在停药2周内恢复.没有出现剂量限制性毒性.爬坡最高剂量为105 mg·m-2·d-1连续5 d.结论沙尔威辛对恶性肿瘤患者的耐受性良好,建议Ⅱ期临床研究推荐剂量为90 mg·m-2·d-1连续5 d,21 d为一周期.     

生长抑素临床应用研究进展

生长抑素是一种典型的脑肠肽,广泛分布于全身及胃肠道各组织器官中,具有抑制生长激素分泌,抑制胃酸、胃蛋白酶释放的功能,能减少内脏血流,并能减少胰腺的内、外分泌以及胃小肠和胆囊的分泌,对胰腺细胞具有保护作用的多肽类激素。本文就SS及其在临床应用的研究现状作一综述。     

Targeting the somatostatin receptor in pituitary and neuroendocrine tumors

Background: Toll-like receptors (TLRs) have been recently recognised as primary receptors in the innate immune system. Apart from initiating a prompt immune response against invading pathogens, TLRs are also considered to be an important link between innate immunity, inflammation and a variety of clinical disorders, including cardiovascular diseases. TLR signalling manipulation with novel drugs could offer important opportunities for cardiovascular disease modification. Objective: To present the latest knowledge supporting the involvement of TLRs in the pathogenesis and progress of cardiovascular diseases and explore the role of TLRs as potential targets for therapeutic intervention in cardiovascular territory. Methods: A review of the literature documenting implication of TLR signalling in cardiovascular disorders. Current progress in TLR-targeting drug development and the potential role of such a treatment strategy in cardiovascular disorders are discussed. Conclusions: A growing body of evidence supports a role for TLRs in cardiovascular disease initiation and progression. Altering TLR signalling with novel drugs could be a beneficial therapeutic strategy for patients with cardiovascular disorders.     

生长抑素类似物治疗神经内分泌肿瘤进展

神经内分泌肿瘤具有高度异质性,多数分化良好的神经内分泌瘤细胞表达生长抑素受体。生长抑素类似物与受体结合的特点不仅应用于神经内分泌瘤的诊断,也用于肿瘤的治疗,包括分泌症状控制和抑制肿瘤增殖。目前被批准用于神经内分泌瘤治疗的生长抑素类似物包括奥曲肽和兰瑞肽,尽管新一代生长抑素类似物帕瑞肽与生长抑素受体具有更强的亲和力,尚无证据显示其优于第一代生长抑素类似物。本文对生长抑素类似物的作用机制,临床应用及发展前景等进行综述。     

Synthesis and characterization of multiply-tyrosinated,multiply-iodinated somatostatin analogs

Radio-labeled somatostatin analogs have recently gained popularity as agents useful in intraoperative tumor localization, external scintigraphy and in situ radiotherapy. We have synthesized and characterized a series of novel N-terminally extended multiply-tyrosinated somatostatin analogs that possess high binding affinity for somatostatin receptors, exhibit biological activity comparable to the native peptide and retain these characteristics after iodination. These analogs can be radio-iodinated to high specific activities. Following radio-iodination, these analogs exhibit minimal radiolysis and may be clinically useful for tumor localization, scanning and therapy.     

Lonidamine: efficacy and safety in clinical trials for the treatment of solid tumors

Lonidamine, a derivate of indazole-3-carboxylic acid, is an antineoplastic drug with a typical mechanism of action. Lonidamine has no function on cellular nucleic acids or protein synthesis, whereas it exerts a powerful inhibitory effect on oxygen consumption, aerobic glycolysis and lactate transport and accumulation of neoplastic cells. Nevertheless, its proven ability to modify the permeability of membranes is consistent with the possible increase of drug uptake, reverse of drug resistance and triggering of apoptotic pathway. Lonidamine has been experimentally shown to potentiate the cytotoxic effects of anthracyclines in human breast cancer cell lines and cisplatin activity in both platinum-sensitive and platinum-resistant human ovarian carcinoma cell lines. Since the specific mechanism of action and side effects are not overlapping with those of standard antineoplastic agents, combination of lonidamine with standard chemotherapy has been widely investigated for the treatment of solid tumors. Additionally, the enhancement of radiotherapy activity by lonidamine has been considered for palliative therapy of lesions from metastatic cancers. The encouraging results of phase II-III trials for the treatment of advanced breast, ovarian and lung cancer must be confirmed by larger studies. Specifically designed studies to address the role of lonidamine in the adjuvant setting are warranted. Lonidamine, a dechlorinate derivative of indazole-3-carboxylic acid, has proved to exert a powerful antiproliferative effect and to impair the energy metabolism of neoplastic cells. Herein we review the current experience on combining lonidamine and chemotherapy and/or radiation therapy in the treatment of solid tumors. Several studies have been published on this topic. The total number of trials reported in literature and length of follow-up are still insufficient to draw a firm conclusion. However, the available data demonstrate a significant role of lonidamine in modulating anthracycline and platinum compound activity.     

盐酸洛拉曲克治疗恶性肿瘤的Ⅰ期临床试验

目的:观察盐酸洛拉曲克治疗恶性肿瘤的安全性,不良反应与剂量的关系,确定推荐Ⅱ期临床研究的剂量.方法:共入选18例患者,盐酸洛拉曲克剂量分为6级,由初始剂量100mg·m-2·d-1开始逐级增加至200,340,570,740,920mg·m-2·d-1,加入5d输液泵持续静脉点滴,21d为一周期,每剂量水平3例.观察药物对机体各系统的影响和毒性反应.结果:盐酸洛拉曲克主要毒性反应为骨髓抑制(白细胞、中性粒细胞和血小板降低)、消化道反应(恶心、呕吐、腹泻)和口腔黏膜炎,毒性反应恢复较快,无药物相关性死亡病例.毒性反应与剂量相关,740mg·m-2·d-1以下的剂量组主要是Ⅰ/Ⅱ度毒性反应,920mg·m-2·d-1剂量组均出现Ⅲ或Ⅳ度毒性反应.洛拉曲克的剂量限制性毒性(DLT)为骨髓抑制(白细胞、中性粒细胞和血小板降低)、腹泻、口腔黏膜炎.最大耐受剂量(MTD)为920mg·m-2·d-1.结论:盐酸洛拉曲克对消化道恶性肿瘤患者的耐受性良好,建议Ⅱ期临床研究推荐剂量为740mug·m-2·d-1×5d,21d为一周期.     

Docetaxel: a tubulin-stabilizing agent approved for the management of several solid tumors

Docetaxel is a semisynthetic taxane that acts by binding to the beta-tubulin subunit of the microtubules, resulting in cell-cycle arrest and apoptosis. It is approved for the management of early and advanced breast cancer, locally advanced and metastatic lung cancer and hormone refractory prostate cancer. Docetaxel has also shown significant antitumor activity in ovarian and gastric tumors and has very recently been approved for the treatment of advanced gastric cancer. Severe neutropenia is the major dose-limiting toxicity with the approved three-weekly regimens, although alternate weekly schedules with less myelotoxicity have been developed for patients with poor bone marrow reserve. This article will review the pharmacology and trials leading to the clinical approval of this agent.     

Dasatinib in solid tumors

Importance of the field: Dasatinib is an oral, potent adenosine triphosphate-competitive inhibitor of multiple tyrosine kinases including BCR-ABL, c-KIT, platelet-derived growth factor receptor, and Src family kinases (SFKs). It has gained much attention for its use in chronic myeloid leukemia and for the treatment of adults with Philadelphia chromosome-positive acute lymphoblastic leukemia. However, dasatinib is also being explored in solid tumors in ongoing Phase I and II clinical trials.

Areas covered in this review: The clinical efficacy of dasatinib in a wide variety of solid tumors and important Phase I/II studies utilizing dasatinib and the optimal dosage used in solid tumors. A literature search was conducted using PubMed/MEDLINE, www.clinicaltrials.gov, and the American Society of Clinical Oncology websites to find relevant Phase I/II clinical trials during 1987 – 2009.

What the reader will gain: The understanding that the biology and mechanism of Src activation in tumors are not well understood and finding the optimal use of SFK inhibitors in the clinical setting requires further investigation.

Take home message: In reviewing the clinical safety data of dasatinib in its current use as a Src inhibitor in a wide variety of solid malignancies, dasatinib appears to be safe and is a promising agent for the treatment of metastatic solid tumors refractory to standard therapies.