Alkaloid-based modulators of the PI3K/Akt/mTOR pathway for cancer therapy: Understandings from pharmacological point of view

This review aims to summarize the role of alkaloids as potential modulators of the PI3K/Akt/mTOR (PAMT) pathway in cancer therapy. The PAMT pathway plays a critical role in cell growth, survival, and metabolism, and its dysregulation contributes to cancer hallmarks. In healthy cells, this pathway is tightly controlled. However, this pathway is frequently dysregulated in cancers and becomes abnormally active. This can happen due to mutations in genes within the pathway itself or due to other factors. This chronic overactivity promotes cancer hallmarks such as uncontrolled cell division, resistance to cell death, and increased blood vessel formation to nourish the tumor. As a result, the PAMT pathway is a crucial therapeutic target for cancer. Researchers are developing drugs that specifically target different components of this pathway, aiming to turn it off and slow cancer progression. Alkaloids, a class of naturally occurring nitrogen-containing molecules found in plants, have emerged as potential therapeutic agents. These alkaloids can target different points within the PAMT pathway, inhibiting its activity and potentially resulting in cancer cell death or suppression of tumor growth. Research is ongoing to explore the role of various alkaloids in cancer treatment. Berberine reduces mTOR activity and increases apoptosis by targeting the PAMT pathway, inhibiting cancer cell proliferation. Lycorine inhibits Akt phosphorylation and mTOR activation, increasing pro-apoptotic protein production and decreasing cell viability. In glioblastoma models, harmine suppresses mTORC1. This review focuses on alkaloids such as evodiamine, hirsuteine, chaetocochin J, indole-3-carbinol, noscapine, berberine, piperlongumine, and so on, which have shown promise in targeting the PAMT pathway. Clinical studies evaluating alkaloids as part of cancer treatment are underway, and their potential impact on patient outcomes is being investigated. In summary, alkaloids represent a promising avenue for targeting the dysregulated PAMT pathway in cancer, and further research is warranted.

Research Progress of Indole Alkaloids: Targeting MAP Kinase Signaling Pathways in Cancer Treatment

Cancer is the leading cause of morbidity and mortality in people throughout the world. There are many signaling pathways associated with cancerous diseases, from which the Mitogen-activated protein kinase (MAPK) pathway performs a significant role in this regard. Apoptosis and proliferation are correlated with MAPK signaling pathways. Plenty of experimental investigations were carried out to assess the role of indole alkaloids in MAPK-mediated cancerous diseases. Previous reports established that indole alkaloids, such as vincristine and evodiamine are useful small molecules in cancer treatment via the MAPK signaling system. Indole alkaloids have the anticancer potential through different pathways. Vincristine and evodiamine are naturally occurring indole alkaloids that have strong anticancer properties. Additionally, much research is ongoing or completed with molecules belonging to this group. The current review aims to evaluate how indole alkaloids affect the MAPK signaling pathway in cancer treatment. Additionally, we focused on the advancement in the role of indole alkaloids, with the intention of modifying the MAPK signaling pathways to investigate potential new anticancer small molecules. Furthermore, clinical trials with indole alkaloids in cancer treatment are also highlighted.

Therapeutic potential of indole alkaloids in respiratory diseases: A comprehensive review

BACKGROUND

Indole alkaloids are very promising for potential therapeutic purposes and appear to be particularly effective against respiratory diseases. Several experimental studies have been performed, both in vivo and in vitro, to evaluate the effectiveness of indole alkaloids for the management of respiratory disorders, including asthma, emphysema, tuberculosis, cancer, and pulmonary fibrosis.

PURPOSE

The fundamental objective of this review was to summarize the in-depth therapeutic potential of indole alkaloids against various respiratory disorders.

STUDY DESIGN

In addition to describing the therapeutic potential, this review also evaluates the toxicity of these alkaloids, which have been utilized for therapeutic benefits but have demonstrated toxic consequences. Some indole alkaloids, including scholaricine, 19-epischolaricine, vallesamine, and picrinine, which are derived from the plant Alstonia scholaris, have shown toxic effects in non-rodent models.

METHODS

This review also discusses clinical studies exploring the therapeutic efficacy of indole alkaloids, which have confirmed the promising benefits observed in vivo and in vitro.

RESULTS

The indole alkaloidal compounds have shown efficacy in subjects with respiratory diseases.

CONCLUSION

The available data established both preclinical and clinical studies confirm the potential of indole alkaloids to treat the respiratory disorders.

Anti-mitotic agents: Are they emerging molecules for cancer treatment?

Mutations in cancer cells frequently result in cell cycle alterations that lead to unrestricted growth compared to normal cells. Considering this phenomenon, many drugs have been developed to inhibit different cell-cycle phases. Mitotic phase targeting disturbs mitosis in tumor cells, triggers the spindle assembly checkpoint and frequently results in cell death. The first anti-mitotics to enter clinical trials aimed to target tubulin. Although these drugs improved the treatment of certain cancers, and many anti-microtubule compounds are already approved for clinical use, severe adverse events such as neuropathies were observed. Since then, efforts have been focused on the development of drugs that also target kinases, motor proteins and multi-protein complexes involved in mitosis. In this review, we summarize the major proteins involved in the mitotic phase that can also be targeted for cancer treatment. Finally, we address the activity of anti-mitotic drugs tested in clinical trials in recent years.

Computer-aided volumetric assessment of malignant pleural mesothelioma on CT using a random walk-based method

OBJECTIVE

The aim of this study is to assess the performance of a computer-aided semi-automated algorithm we have adapted for the purpose of segmenting malignant pleural mesothelioma (MPM) on CT.

METHODS

Forty-five CT scans were collected from 15 patients (M:F [Formula: see text] 10:5, mean age 62.8 years) in a multi-centre clinical drug trial. A computer-aided random walk-based algorithm was applied to segment the tumour; the results were then compared to radiologist-drawn contours and correlated with measurements made using the MPM-adapted Response Evaluation Criteria in Solid Tumour (modified RECIST).

RESULTS

A mean accuracy (Sørensen-Dice index) of 0.825 (95% CI [0.758, 0.892]) was achieved. Compared to a median measurement time of 68.1 min (range [40.2, 102.4]) for manual delineation, the median running time of our algorithm was 23.1 min (range [10.9, 37.0]). A linear correlation (Pearson's correlation coefficient: 0.6392, [Formula: see text]) was established between the changes in modified RECIST and computed tumour volume.

CONCLUSION

Volumetric tumour segmentation offers a potential solution to the challenges in quantifying MPM. Computer-assisted methods such as the one presented in this study facilitate this in an accurate and time-efficient manner and provide additional morphological information about the tumour's evolution over time.

Vinorelbine in pemetrexed-pretreated patients with malignant pleural mesothelioma

BACKGROUND

Pemetrexed-platinum chemotherapy is the standard first-line treatment of unresectable malignant pleural mesothelioma (MPM). At progression, patients are generally selected to experimental trials, when available, or, in every-day clinical practice, they are offered second-line chemotherapy. The optimal treatment has not yet been defined. The aim of this retrospective, single-center study was to evaluate the activity and toxicity of vinorelbine administered to a consecutive series of pemetrexed-pretreated MPM patients.

METHODS

Vinorelbine 25 mg/m(2) was administered intravenously as a single agent on days 1, 8 every three weeks, either as second-line (2L) or further-line (>2L) therapy. Treatment was repeated for a maximum of 6 cycles, until progression, or unacceptable toxicity.

RESULTS

Fifty-nine patients were included in this analysis. Vinorelbine was given to 34 patients as 2L, and to 25 as > 2L treatment. The median age was 69 years (range 45-80). Forty-two patients (71.2%) had a good EORTC prognostic score. Partial response was observed in 9 (15.2%) cases, stable disease in 20 (33.9%). The overall disease control rate (DCR) was 49.1%. Median progression-free survival (PFS) and overall survival (OS) were 2.3 and 6.2 months, respectively. ECOG performance status (PS) (HR(0 vs. 1-2) 0.50; 95%CI: 0.3-0.8; p = 0.014) and PFS ≥ 6 months following first-line (FL) chemotherapy (HR(FL-PFS>6 ms vs. <6 ms) 0.50; 95%CI: 0.3-0.9; p = 0.031) were significantly associated to OS in multivariate analysis. No difference was observed in terms of DCR, PFS, and OS in relation to age, histology, sex, line of vinorelbine therapy, or response to FL treatment. Hematological toxicity was acceptable, with grade 3/4 neutropenia occurring in 5 (8.4%) patients, and there were no cases of febrile neutropenia. The main non-hematological toxicities were grade 2 fatigue in 17 (28.8%) and constipation in 7 (11.8%) patients.

CONCLUSIONS

Vinorelbine was moderately active in pemetrexed-pretreated MPM patients, with an acceptable toxicity profile, particularly in patients with ECOG-PS0 and FL-PFS ≥ 6 months.

Vinflunine: a new vision that may translate into antiangiogenic and antimetastatic activity

Microtubules and tubulin are major dynamic and structural cellular components that play a key role in several cell functions, including division, signalling and intracellular trafficking. Normal epithelial cells have a highly structured, rigid cytoskeletal network that is compatible with cell motility. Thus, tubulin and microtubules are compelling cellular targets for chemotherapy. In fact, among anticancer agents, those that target microtubules constitute one of the most effective classes of chemotherapeutics in cancer. The list of compounds that target either tubulin or microtubules is extensive and consists of chemically unique compounds that bind to the tubulin dimers and destabilize microtubules (Vinca alkaloids) and those that bind to the microtubule polymer and stabilize microtubules (taxanes). Tumour-induced angiogenesis, the formation of new capillaries from existing blood vessels, and epithelial-mesenchymal transition are two steps that are critical for both tumour growth and metastatic spread. Three possible mechanisms of action are described with vinflunine, the new-generation Vinca alkaloid to arrive in clinical practice are as follows: it acts against tubulin and microtubules, disrupts newly formed blood vessels and seems to be able to reduce the metastatic process as shown in preclinical studies. These findings support the hypothesis that vinflunine, by blocking microtubule functions that contribute to cell shape, polarization, migration and other processes, might be responsible not only for tumour-cytostatic but also for specific antiangiogenic or antiepithelial-mesenchymal transition effects.

Antimitotic inhibitors

Of the agents available in the treatment of both solid and hematologic cancers, microtubule-targeted agents are among the most widely used and exploiting other mechanisms involving the microtubule and its role in mitosis is an area of continued interest. This review will focus on novel microtubule-targeted agents, both recently approved (eg, ixabepilone and eribulin) and in later-stage clinical trials, and kinase inhibitors that aim to directly inhibit the mitotic spindle, such as the aurora kinase, pololike kinase, and kinsein-spindle protein inhibitors.

Investigational approaches for mesothelioma

Malignant pleural mesothelioma (MPM) is a rare, aggressive tumor with a poor prognosis. In view of the poor survival benefit from first-line chemotherapy and the lack of subsequent effective treatment options, there is a strong need for the development of more effective treatment approaches for patients with MPM. This review will provide a comprehensive state of the art of new investigational approaches for mesothelioma. In an introductory section, the etiology, epidemiology, natural history, and standard of care treatment for MPM will be discussed. This review provide an update of the major clinical trials that impact mesothelioma treatment, discuss the impact of novel therapeutics, and provide perspective on where the clinical research in mesothelioma is moving. The evidence was collected by a systematic analysis of the literature (2000-2011) using the databases Medline (National Library of Medicine, USA), Embase (Elsevier, Netherlands), Cochrane Library (Great Britain), National Guideline Clearinghouse (USA), HTA Database (International Network of Agencies for Health Technology Assessment - INAHTA), NIH database (USA), International Pleural Mesothelioma Program - WHOLIS (WHO Database), with the following keywords and filters: mesothelioma, guidelines, treatment, surgery, chemotherapy, radiotherapy, review, investigational, drugs. Currently different targeted therapies and biologicals are under investigation for MPM. It is important that the molecular biologic research should first focus on mesothelioma-specific pathways and biomarkers in order to have more effective treatment options for this disease. The use of array technology will be certainly an implicit gain in the identification of new potential prognostic or biomarkers or important pathways in the MPM pathogenesis. Probably a central mesothelioma virtual tissue bank may contribute to the ultimate goal to identify druggable targets and to develop personalized treatment for the MPM patients.

Vinflunine: review of a new vinca alkaloid and its potential role in oncology

Objective: To review the pharmacology, pharmacokinetics, in vitro and in vivo efficacy, and safety profile of vinflunine in the treatment of various solid tumors.

Data sources: A literature search was conducted using keywords included vinflunine, vinca alkaloid, Javlor, and solid tumor in PubMed/MEDLINE (1950—January 2009) and International Pharmaceutical Abstracts (1950—January 2009). Study selection and data extraction: Published studies, posters, and meeting abstracts evaluating the in vitro and in vivo efficacy of vinflunine were reviewed.

Data synthesis: Vinflunine is the newest member of the vinca alkaloid family. It has the weakest affinity to tubulins, but is shown to have unique receptor-independent antiangiogenesis, and antimetastasis properties. After administration, it is distributed extensively into tissues, metabolized via the CYP3A4 system, and eventually excreted in urine and feces. Phase II/III trials reported activities of vinflunine in advanced stage nonsmall-cell lung cancer, metastatic breast cancer, metastatic renal cell carcinoma, transitional cell carcinomas of the urothelium, small-cell lung cancer, and malignant pleural mesothelioma as monotherapy and in combination with other chemotherapy agents. More ongoing trials are evaluating its use in other solid tumors and in combination regimens. The most common adverse events in these trials were hematological (anemia and neutropenia), constipation, fatigue, abdominal pain, and myalgia.

Conclusions: Vinflunine is a new vinca alkaloid for the treatment of advanced staged solid tumors. Available data showed promising activities in various malignancies. Further studies are needed to further define vinflunine’s role in oncology.

A phase I evaluation of the combination of vinflunine and erlotinib in patients with refractory solid tumors

PURPOSE

Epidermal growth factor receptor (EGFR) inhibition may overcome chemotherapy resistance by inhibiting important anti-apoptotic signals that are constitutively activated by an overstimulated EGFR pathway.

METHODS

This phase I dose escalation trial assessed the safety and efficacy of vinflunine, a novel vinca alkaloid microtubule inhibitor, with erlotinib, an EGFR tyrosine kinase inhibitor, in patients with refractory solid tumors.

RESULTS

Seventeen patients were treated, 10 with continuous erlotinib, and 7 with intermittent erlotinib. At dose level 1, vinflunine 280 mg/m(2) IV day 1 and erlotinib 75 mg PO days 2-21 ("continuous erlotinib") in 21 day cycles, two of four patients experienced DLTs. At dose level -1 (vinflunine 250 mg/m(2) every 21 days and erlotinib 75 mg/day), two of six patients experienced DLTs. The study was amended to enroll to "intermittent erlotinib" dosing: vinflunine day 1 and erlotinib days 2-15 of a 21 day cycle. Two of seven experienced DLTs and the study was terminated. One patient with breast cancer had a partial response; three had stable disease ≥ 6 cycles. All were treated in the continuous erlotinib group.

CONCLUSIONS

Given the marked toxicity in our patient population, the combination of vinflunine and erlotinib cannot be recommended for further study with these dosing schemas.

Phase I trial of vinflunine and pemetrexed in refractory solid tumors

BACKGROUND

Vinflunine is a novel vinca alkaloid with promising single agent clinical activity. Pemetrexed has at least additive activity with other vincas. A phase I trial was undertaken to assess the safety of vinflunine and pemetrexed in patients with refractory solid tumors.

METHODS

A standard 3-patient cohort dose escalation scheme was used to determine the dose-limiting toxicity (DLT) and maximum tolerated dose (MTD) of the vinflunine/pemetrexed combination. Pemetrexed 500 mg/m(2) was given with vinflunine 280 mg/m(2) (cohort 1), 300 mg/m(2) (cohort 2) or 320 mg/m(2) (cohort 3) on day 1 of a 21-day cycle.

RESULTS

19 patients were enrolled, median age 58 years (range 32 to 77) and had a median of 3 (range 1-6) prior therapies. DLT occurred 1 of 6 pts in cohort 1 (thrombocytopenia, hyponatremia), 2 of 10 pts in cohort 2 (febrile neutropenia, hyponatremia, hyperbilirubinema; febrile neutropenia), and 2 of 3 pts in cohort 3 (febrile neutropenia, hypokalemia; febrile neutropenia). 1 pt in cohort 2 died prior to completion of cycle 1 likely from disease progression. Most common grade 3/4 adverse events were neutropenia (7), leukopenia (5). Febrile neutropenia occurred in 4 patients (21%). No objective responses were seen. Two patients (breast and lung) had prolonged stable disease for 25 and 20 cycles respectively.

CONCLUSIONS

Based on this experience we recommend vinflunine 300 mg/m(2) and pemetrexed 500 mg/m(2) in combination every 3 weeks for future study. At these doses, the combination of vinflunine and pemetrexed was tolerable in this heavily pretreated population. Hematologic toxicity, including febrile neutropenia, was prominent.

Improving the outcome in malignant pleural mesothelioma: nonaggressive or aggressive approach?

PURPOSE OF REVIEW

The treatment of malignant pleural mesothelioma continues to be a clinical challenge. The question, however, is no longer whether to provide active treatment or not, but how aggressive the treatment should be in view of the limited life expectancy of patients with this disease.

RECENT FINDINGS

With platin and pemetrexed-based combination chemotherapy having become the preferred systemic therapy, the major questions now evolve around the identification of a suitable second line therapy and the quest for innovative new approaches. Surgical interventions from pleurectomy and decortication to extrapleural pneumonectomy have increasingly come of use in specialized centres. With neoadjuvant chemotherapy and extrapleural pneumonectomy median survival times of almost 2 years have been reported. Studies on high-dose hemithoracic radiotherapy after extrapleural pneumonectomy suggested a beneficial effect on local recurrence. However, both extrapleural pneumonectomy and high-dose hemithoracic radiotherapy are associated with potential treatment-related mortality and morbidity and cannot yet be recommended outside specialized centres.

SUMMARY

More than ever, the diagnosis and treatment of patients with malignant pleural mesothelioma mandate a multidisciplinary approach.

Microtubule inhibitors: Differentiating tubulin-inhibiting agents based on mechanisms of action, clinical activity, and resistance

Microtubules are important cellular targets for anticancer therapy because of their key role in mitosis. Microtubule inhibitors (MTI) such as taxanes, vinca alkaloids, and epothilones stabilize or destabilize microtubules, thereby suppressing microtubule dynamics required for proper mitotic function, effectively blocking cell cycle progression and resulting in apoptosis. In spite of their antitumor activity, innate or acquired drug resistance to MTIs such as the taxanes is common, limiting their overall clinical efficacy. Further insight into the mechanisms of action of microtubule-targeting drugs has lead to the discovery of novel agents that may provide higher efficacy with limited toxicity and help overcome resistance to conventional MTIs. This review will focus on the different mechanisms of action of MTIs, potential factors related to resistance and tolerability, and will discuss the recent approval as well as the development of new antineoplastic agents.

Malignant pleural mesothelioma

Malignant pleural mesothelioma continues to be a challenge. The diagnosis and treatment of patients with malignant pleural mesothelioma requires a multidisciplinary approach. The diagnosis is best made by thoracoscopic biopsy and the aid of immunohistochemistry. Molecular studies identified inactivation of the neurofibromatosis-2 gene and INK4alpha/ARF to be key events in tumorigenesis. Based on the results of a Phase III trial, the combination of cisplatin with pemetrexed has become the preferred choice for chemotherapy, although there is suggestive evidence for the activity of other platin combinations based on Phase II studies. The optimal second-line chemotherapy remains to be defined. Surgical interventions ranging from pleurectomy/decortication to extrapleural pneumonectomy are increasingly offered in specialized centers, and the results of multimodality approaches with neoadjuvant or adjuvant chemotherapy and extrapleural pneumonectomy are encouraging. Ongoing investigations are defining the role of postoperative radiotherapy and the clinical activity of tyrosine kinase inhibitors targeting VEGFR2, histone deacetylase inhibitors and proteosome inhibitors.

Malignant pleural mesothelioma: medical treatment update

Malignant pleural mesothelioma (MPM) is a disease usually unaffected by current therapeutic strategies, but for the majority of patients, the use of systemic chemotherapeutic drugs remains the only therapeutic option available. During the past 15-20 years, many phase II and a few phase III clinical trials have studied a large variety of drugs such as anthracyclines, alkylating agents, platinum compounds, taxanes, vinka alkaloids, and antifolates as single agents and in combination, with the aim to increase responses and survival. The combination of pemetrexed and cisplatin tested in the largest phase III randomized trial of malignant pleural mesothelioma ever conducted has become the current standard of care. New targeted therapeutic approaches with a variety of anti-growth factor drugs are currently undergoing investigation worldwide.

Malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a deadly disease that occurs in 2,000 to 3,000 people each year in the United States. Although MPM is an extremely difficult disease to treat, with the median overall survival ranging between 9 and 17 months regardless of stage, there has been significant progress over the last few years that has reshaped the clinical landscape. This article will provide a comprehensive discussion of the latest developments in the treatment of MPM. We will provide an update of the major clinical trials that impact mesothelioma treatment in the resectable and unresectable settings, discuss the impact of novel therapeutics, and provide perspective on where the clinical research in mesothelioma is moving. In addition, there are controversial issues, such as the role of extrapleural pneumonectomy, adjuvant radiotherapy, and use of intensity-modulated radiotherapy versus hemithoracic therapy that will also be addressed in this manuscript.

Systemic treatments for mesothelioma: standard and novel

Systemic therapy is the only treatment option for the majority of mesothelioma patients, for whom age, co-morbid medical illnesses, non-epithelial histology, and locally advanced disease often preclude surgery. For many years, chemotherapy had a minimal impact on the natural history of this cancer, engendering considerable nihilism. Countless drugs were evaluated, most of which achieved response rates below 20% and median survival of <1 year. Several factors have hampered the evaluation of systemic regimens in patients with mesothelioma. The disease is uncommon, affecting only about 2500 Americans annually. Thus, most clinical trials are small, and randomized studies are challenging to accrue. There is significant heterogeneity within the patient populations of these small trials, for several reasons. Since all of the staging systems for mesothelioma are surgically based, it is almost impossible to accurately determine the stage of a patient who has not been resected. Patients with very early stage disease may be lumped together with far more advanced patients in the same study. The disease itself is heterogenous, with many different prognostic factors, most notably three pathologic subtypes—epithelial, sarcomatoid, and biphasic—that have different natural histories, and varying responses to treatment. Finally, response assessment is problematic, since pleural-based lesions are difficult to measure accurately and reproducibly. Assessment criteria often vary between trials, making some cross-trial comparisons difficult to interpret. Despite these limitations, in recent years, there has been a surge of optimism regarding systemic treatment of this disease. Several cytotoxic agents have been shown to generate reproducible responses, improve quality of life, or prolong survival in mesothelioma. Drugs with single-agent activity include pemetrexed, raltitrexed, vinorelbine, and vinflunine. The addition of pemetrexed or raltitrexed to cisplatin prolongs survival. The addition of cisplatin to pemetrexed, raltitrexed, gemcitabine, irinotecan, or vinorelbine improves response rate. The combination of pemetrexed plus cisplatin is considered the benchmark front-line regimen for this disease, based on a phase III trial in 456 patients that yielded a response rate of 41% and a median survival of 12.1 months. Vitamin supplementation with folic acid is essential to decrease toxicity, though recent data suggests that there may be an optimum dose of folic acid that should be administered; higher doses may diminish the effectiveness of pemetrexed. There are also several unresolved questions about the duration and timing of treatment with pemetrexed that are the subject of planned clinical trials. It is essential to recognize that the improvements observed with the pemetrexed/cisplatin combination, though real, are still modest. Other active drugs or drug combinations may be more appropriate for specific individuals, and further research is still needed to improve upon these results. Since the majority of mesotheliomas in the United States occur in the elderly, non-cisplatin-containing pemetrexed combinations may be more appropriate for some patients. Now that effective agents have been developed for initial treatment, several classical cytotoxic drugs and many novel agents are being evaluated in the second-line setting. These include drugs targeted against the epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor, src kinase, histone deacetylase, the proteasome, and mesothelin. Given the progress made in recent years, there is reason to believe that more effective treatments will continue to be developed.

New tubulin targeting agents currently in clinical development

BACKGROUND

The first tubulin targeting agents were approved as cancer chemotherapeutics over 40 years ago and tubulin as an antitumor target continues to attract significant drug discovery and development attention. Mechanism of action as defined by tubulin binding sites and effect on microtubules distinguishes these agents, but the end result is equivalent in that microtubule disruption leads to cell cycle arrest at G2/M phase of the cell cycle and subsequent apoptotic cell death.

OBJECTIVES

The goal of this review is to describe the state of clinical development of tubulin targeting agents as of early 2008, with descriptions of clinical experience slanted toward the most advanced trials for each agent.

METHOD

Objective information in this review was obtained exclusively from public sources that included journals, scientific meeting abstracts, posters and oral presentations, websites and public presentations from companies. Opinions expressed in this review are exclusively from the author.

RESULTS/CONCLUSIONS

A large number of tubulin targeting agents are currently in clinical development, including microtubule stabilizing and destabilizing compounds acting through all three of the characterized tubulin binding sites. With the approval of ixabepilone for refractory breast cancer, the epothilones appear best positioned to make an impact among the new microtubule stabilizing compounds. There are 17 microtubule destabilizing agents under clinical assessment, with many only in Phase I and results to date include at best modest efficacy signals with no obvious indication trend.

Vinflunine: a new microtubule inhibitor agent

Vinflunine (Javlor) is the first fluorinated microtubule inhibitor belonging to the Vinca alkaloids family. Vinflunine is obtained by semisynthesis using superacidic chemistry to selectively introduce two fluorine atoms at the 20' position of the catharanthine moiety. This compound has been selected for clinical development on the basis of encouraging preclinical activity that warrants study in patients with a wide spectrum of solid tumors. Clinically significant activity has been seen in phase II studies, mainly in the treatment of transitional cell carcinoma of the urothelial tract, non-small cell lung cancer, and carcinoma of the breast. Vinflunine is currently in phase III trial assessment in patients with (second line) transitional cell carcinoma of the urothelium and first-line advanced breast cancer. The efficacy of vinflunine in patients with advanced non-small cell lung cancer previously treated with a platinum-containing regimen was confirmed by a large phase III trial.

The efficacy and safety of weekly vinorelbine in relapsed malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rapidly progressive invariably lethal tumor. Treatment options remain limited and the outcome in relapsed disease is poor warranting new therapeutic options. Following our previous experience in the first-line setting, we conducted a phase 2 open-label non-comparative study to assess the safety and efficacy of weekly vinorelbine chemotherapy, each cycle consisting of 30 mg/m(2) for 6 weeks, in patients with previous exposure to chemotherapy. In 63 individuals with relapsed MPM who had not received previous vinorelbine, we observed an objective response rate of 16% and an overall survival of 9.6 months (95% confidence interval 7.3-11.8 months). The main grade III/IV toxicity observed was neutropenia and toxicity was similar to weekly vinorelbine when used in the first-line setting. Weekly vinorelbine appeared to have a reasonable response rate with an acceptable toxicity profile in the second-line treatment of MPM. Its use should be prospectively evaluated in a randomised trial in the first or second-line therapy of MPM.

[Malignant pleural mesothelioma: interrogations and hopes concerning the expected epidemic]

Malignant pleural mesothelioma (MPM) is a rare incurable tumor. Interest in MPM has increased in recent years due to a steadily increasing incidence subsequent to the intensive use of asbestosis, the main causal agent, but also due to better awareness in the political and scientific communities faced with a serious public health issue. Our knowledge of MPM has improved regularly in terms of pathologic diagnosis and the mechanisms underlying the mesothelial carcinogenesis. MPM is also the subject of many technological innovations as illustrated by the recent identification of new biological markers, access to metabolic imaging, and clinical research on targeted treatments. Proper management implies the participation of the general population since the implementation of administrative procedures for social indemnities. In 2007, a more aggressive therapeutic approach is becoming common practice with the use of radiotherapy and the emergence of the concept of multimodal care centered on wide pleuropneumonectomy. These advances create real hope for improvement, but also many interrogations since no standard treatment protocol has been clearly identified.