Axitinib is an active treatment for all histologic subtypes of advanced thyroid cancer: results from a phase II study

Pharmacophore modeling and virtual screening studies for new VEGFR-2 kinase inhibitors

Virtual screening was performed to determine potent vascular endothelial growth factor receptor (VEGFR)-2 kinase inhibitors. A database of approximately 820,000 commercial compounds was used for screening, and 100 compounds were chosen as candidate VEGFR-2 inhibitors through pharmacophore modeling and docking studies. These 100 compounds were purchased to test their biological activities: 10 compounds were found to inhibit the enzyme, with IC(50) values ranging from 10 to 1 μM. Compound 1, which has a triazinoindole ring, inhibited the enzymatic activity of VEGFR-2, with an IC(50) value of about 1.6 μM, making it the most potent inhibitor of this enzyme. The triazinoindole derivative may therefore serve as the starting point in the design of new VEGFR-2 kinase inhibitors.

Effect of ketoconazole on the pharmacokinetics of axitinib in healthy volunteers

OBJECTIVE

Axitinib (AG-013736), an oral, potent, and selective inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, is metabolized primarily by cytochrome P450 (CYP) 3A with minor contributions from CYP1A2, CYP2C19, and glucuronidation. Co-administration with CYP inhibitors may increase systemic exposure to axitinib and alter its safety profile. This study evaluated changes in axitinib plasma pharmacokinetic parameters and assessed safety and tolerability in healthy subjects, following axitinib co-administration with the potent CYP3A inhibitor ketoconazole.

METHODS

In this randomized, single-blind, two-way crossover study, 32 healthy volunteers received placebo, followed by a single 5-mg oral dose of axitinib, administered either alone or on the fourth day of dosing with oral ketoconazole (400 mg/day for 7 days).

RESULTS

Axitinib exposure was significantly increased in the presence of ketoconazole, with a geometric mean ratio for area under the plasma concentration-time curve from time zero to infinity of 2.06 (90% confidence interval [CI]: 1.84-2.30) and a geometric mean ratio for maximum plasma concentration (C(max)) of 1.50 (90% CI: 1.33-1.70). For axitinib alone or with ketoconazole, C(max) occurred 1.5 and 2.0 h after dosing, respectively. Adverse events were predominantly mild; the most commonly reported treatment-related adverse events were headache and nausea.

CONCLUSIONS

Axitinib plasma exposures and peak concentrations were increased following concurrent administration of axitinib and ketoconazole in healthy volunteers. Axitinib alone and in combination with ketoconazole was well tolerated. These findings provide an upper exposure for expected axitinib plasma concentrations in the presence of potent metabolic inhibition.

Molecular and other novel advances in treatment of metastatic epithelial and medullary thyroid cancers

An understanding of the mutations of the proto-oncogenes and tumor suppressor genes that occur in thyroid cancers should eventually explain the diverse clinical characteristics of these tumors and also direct therapy. Some insights have already emerged in the last decade; some abnormalities in tumor genes are consistently associated with specific clinical and pathologic findings. These genetic abnormalities usually represent somatic mutations in tumors of follicular epithelial origin, as opposed to inherited mutations in medullary thyroid cancers of parafollicular C cells origin because most thyroid tumors are sporadic and not familial. This is different from the multiple endocrine neoplasia syndromes in which the primary tumorigenic gene mutations are inherited. This improved understanding of the molecular basis of these diseases has led to the development of novel targeted therapeutic approaches which will be discussed in this paper.

Targeted molecular therapies in thyroid carcinoma

Thyroid cancer incidence has significantly increased in the last three decades and many patients seek medical attention for its treatment every year. Among follicular cell-derived tumors, the majority are differentiated thyroid carcinomas (DTC), whose prognosis is very good with only 15% of the cases presenting disease persistence or recurrence after initial treatment. Medullary thyroid carcinoma has a worse prognosis, especially in patients with diffused cancers at the time of initial surgery. Traditional treatment options for persistent or recurrent disease include additional surgery, radioiodine treatment and TSH-suppression in DTC patients; external beam radiotherapy, and cytotoxic chemotherapy, often have low efficacy and many patients with advanced disease ultimately die. In the last two decades many of the molecular events involved in cancer formation have been uncovered. This knowledge has prompted the development of novel therapeutic strategies mainly based on the inhibition of key molecular mediators of the tumorigenic process. In particular the class of small-molecule tyrosine kinase inhibitors was enriched by many compounds that have reached clinical trials and in some cases have had approval for clinical use in specific cancers. Many of these compounds entered clinical trials also for locally advanced or metastatic thyroid carcinomas showing very promising results.

Anaplastic thyroid carcinoma: pathogenesis and emerging therapies

Anaplastic thyroid carcinoma ranges from 1.3 to 9.8% of all thyroid cancers globally. Mutations, amplifications, activation of oncogenes and silencing of tumour suppressor genes contribute to its aggressive behaviour, and recent studies (e.g. microarrays, microRNAs) have provided further insights into its complex molecular dysregulation. Preclinical studies have identified numerous proteins over- or underexpressed that affect critical cellular processes, including transcription, signalling, mitosis, proliferation, cell cycle, apoptosis and adhesion, and a variety of agents that effectively inhibit these processes and tumour growth. In clinical studies of 1771 patients, 64% were women, the median survival was 5 months, and 1-year survival was 20%. The variables associated with survival in some series included age, tumour size, extent of surgery, higher dose radiotherapy, absence of distant metastases at presentation, co-existence of differentiated thyroid cancer and multimodality therapy. However, considerable bias exists in these non-randomised studies. Although more aggressive radiotherapy has reduced locoregional recurrences, the median overall survival has not improved in over 50 years. Newer systemic therapies are being tried, and more effective combinations are needed to improve patient outcomes.

Medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) accounts for 5-8% of all thyroid cancers. MTC is mainly sporadic in nature, but an hereditary pattern [multiple endocrine neoplasia type 2 (MEN 2)] is present in 20-30% of cases, transmitted as an autosomal-dominant trait due to germline mutations of the RET proto-oncogene. About 98% of patients with MEN 2 have germline mutations in exons 5, 8, 10, 11, 13, 14, 15 or 16 of the RET gene. The primary treatment of both hereditary and sporadic forms of MTC is total thyroidectomy and removal of all neoplastic tissue present in the neck. The therapeutic option for lymph node surgery should be dictated by the results of presurgical evaluation. After total thyroidectomy, measurements of serum calcitonin (CT) and carcinoembryonic antigen are of paramount importance in the postsurgical follow-up of patients with MTC as they reflect the presence of persistent or recurrent disease. Complete remission is demonstrated by undetectable and stimulated serum CT measurement. On the contrary, if serum CT is detectable under basal conditions or becomes detectable after stimulation, the patient is probably not cured, but imaging techniques will not demonstrate any disease until serum CT approaches levels >150 pg/ml. The tumour metastasises early to both paratracheal and lateral cervical lymph nodes. Metastases outside the neck may occur in the liver, lungs, bones and, less frequently, brain and skin. Surgery is the main treatment for local and distant metastases whenever feasible. Systemic chemotherapy with dacarbazine, 5-fluorouracil and doxorubicin (alone or in combination) has shown very limited efficacy, achieving only partial responses in the range of 10-20% and of short duration. Several kinase inhibitors are currently under evaluation and preliminary results are promising. Familial cases must be identified by searching for RET proto-oncogene mutations in the proband and in family members. Carriers of the RET gene are candidates for prophylactic thyroidectomy at different ages depending on the risk associated with the specific RET mutations.

The evolving field of tyrosine kinase inhibitors in the treatment of endocrine tumors

Activation of tyrosine kinase receptors (TKRs) and their related pathways has been associated with development of endocrine tumors. Compounds that target and inactivate the kinase function of these receptors, tyrosine kinase inhibitors (TKIs), are now being applied to the treatment of endocrine tumors. Recent clinical trials of TKIs in patients with advanced thyroid cancer, islet cell carcinoma, and carcinoid have shown promising preliminary results. Significant reductions in tumor size have been described in medullary and papillary thyroid carcinoma, although no complete responses have been reported. Case reports have described significant tumor volume reductions of malignant pheochromocytomas and paragangliomas. In addition, these compounds showed an initial tumoricidal or apoptotic response followed by long-term static effects on tumor growth. Despite the promising preliminary results, this class of therapeutic agents has a broad spectrum of adverse effects, mediated by inhibition of kinase activities in normal tissues. These adverse effects will have to be balanced with their benefit in clinical use. New strategies will have to be applied in clinical research to achieve optimal benefits. In this review, we will address the genetic alterations of TKRs, the rationale for utilizing TKIs for endocrine tumors, and current information on tumor and patient responses to specific TKIs. We will also discuss the adverse effects related to TKI treatment and the mechanisms involved. Finally, we will summarize the challenges associated with use of this class of compounds and potential solutions.

Update on recent developments in the therapy of differentiated thyroid cancer

In the past decade, the management of differentiated thyroid carcinoma changed significantly and thus contributed to the improvement of the already favorable prognosis of this malignant disease. Surgical treatment techniques improved and the extent of initial surgery is more individualized. Radioiodine therapy is an essential part of therapeutic regimens in almost all cases, and the use of recombinant human thyroid-stimulating hormone has established for ablation of remnant tissue, treatment of iodine-positive cancer, and sensitive thyroglobulin measurement during follow-up. Risk stratification has become more important to plan treatment and follow-up individually, particularly to evaluate the need for thyroid-stimulating hormone suppression therapy. Especially for inoperable and radioiodine-negative thyroid carcinomas, novel treatment options such as tyrosine kinase inhibitor therapy have emerged. This article deals with the current options of optimal therapy regimens in differentiated thyroid carcinoma.

Axitinib: The evidence of its potential in the treatment of advanced thyroid cancer

Introduction:

Thyroid cancer is a rare disease with an incidence of around 37,000 cases per year. However, its incidence is rising faster than many other cancers and for men this disease ranks highest overall in the rate of increase (2.4% annual increase) in cancer deaths. As the number of radioactive iodine-resistant thyroid cancers increases, the need for newer treatments has become more important. Axitinib is one of many new small molecule inhibitors of growth factor receptors that have shown promise in the treatment of many cancers. It targets the vascular endothelial growth factor receptors 1, 2 and 3.

Aims:

The goal of this article is to review the published evidence for the use of axitinib in the treatment of thyroid cancer and define its therapeutic potential.

Evidence review:

The major evidence of axitinib activity has appeared in meeting report abstracts. One phase II study has been published. This included patients with any histological type of thyroid cancer that was not amenable to treatment with radioactive iodine.

Clinical potential:

To date, in phase II clinical studies axitinib has demonstrated antitumor activity in advanced refractory thyroid cancer. As a monotherapy it resulted in a 30% response rate with another 38% of patients having stable disease. Axitinib appears to have a good tolerability profile, with hypertension being the most common grade 3 or greater side effect.

Bevacizumab increases risk for severe proteinuria in cancer patients

Treatment with the chemotherapeutic agent bevacizumab, a humanized mAb that neutralizes vascular endothelial growth factor, can lead to proteinuria and renal damage. The risk factors and clinical outcomes of renal adverse events are not well understood. We performed a systematic review and meta-analysis of published randomized, controlled trials to assess the overall risk for severe proteinuria with bevacizumab. We analyzed data from 16 studies comprising 12,268 patients with a variety of tumors. The incidence of high-grade (grade 3 or 4) proteinuria with bevacizumab was 2.2% (95% confidence interval [CI] 1.2 to 4.3%). Compared with chemotherapy alone, bevacizumab combined with chemotherapy significantly increased the risk for high-grade proteinuria (relative risk 4.79; 95% CI 2.71 to 8.46) and nephrotic syndrome (relative risk 7.78; 95% CI 1.80 to 33.62); higher dosages of bevacizumab associated with increased risk for proteinuria. Regarding tumor type, renal cell carcinoma associated with the highest risk (cumulative incidence 10.2%). We did not detect a significant difference between platinum- and non-platinum-based concurrent chemotherapy with regard to risk for high-grade proteinuria (P = 0.39). In conclusion, the addition of bevacizumab to chemotherapy significantly increases the risk for high-grade proteinuria and nephrotic syndrome.

New targeted molecular therapies for dedifferentiated thyroid cancer

Dedifferentiated thyroid cancer (DeTC) derived from follicular epithelium is often incurable because it does not respond to radioiodine, radiotherapy, or chemotherapy. In cases, RET/PTC rearrangements are found in 30%–40%, RAS mutations in about 10%, and BRAF mutations in around 40%–50%, with no overlap between these mutations results in papillary thyroid cancer, while a higher prevalence of BRAF mutations (up to 70%) has been observed in DeTC. The identification of these activating mutations in DeTC makes this malignancy an excellent model to examine the effect of tyrosine kinase inhibitors (TKIs). Clinical trials with several TKIs targeting RET, and to a lesser extent BRAF, and other TKRs have shown positive results, with about one-third of DeTC showing a reduction in tumor size up to 50%, with the longest treatment duration of approximately three-four years. Angiogenesis inhibitors have also shown promising activity in DeTC. Progress is being made toward effective targeted DeTC therapy. The possibility of testing the sensitivity of primary DeTC cells from each subject to different TKIs could increase the effectiveness of the treatment.

Treatment with tyrosine kinase inhibitors for patients with differentiated thyroid cancer: the M. D. Anderson experience

OBJECTIVES

Until recently, treatment options for patients with progressive, radioactive iodine-resistant differentiated thyroid cancer (DTC) have been limited. In our clinical practice, we have begun to use sorafenib and sunitinib for patients with progressive DTC who are not able or willing to participate in clinical trials. In this paper, we describe the University of Texas M. D. Anderson Cancer Center's experience with the off-label use of these tyrosine kinase inhibitors for DTC.

METHODS

Adult patients were included if they had a diagnosis of radioactive iodine-refractory DTC, were treated with single agent sorafenib or sunitinib, and had both baseline and at least one follow-up scan for restaging purposes. All imaging data were collected, as well as the TSH-suppressed thyroglobulin (Tg) levels corresponding to each scan date. The primary endpoints were radiographic response and progression-free survival (PFS). Secondary objectives were tissue-specific radiographic responses and correlation of Tg with overall response.

RESULTS

We identified 33 patients from our clinical database. Fifteen patients (nine women, six men) met inclusion criteria, with a median age of 61 yr (range, 38-83 yr). Eight patients had papillary and seven had follicular thyroid carcinoma. Sorafenib was used in 13 and sunitinib in two, including one patient who failed prior sorafenib therapy. All patients had evidence of progressive disease (PD) before start of therapy, with a median PFS of only 4 months. Best response in target lesions was: partial response (PR) in three (20%), stable disease (SD) in nine (60%), and PD in three (20%). Clinical benefit (PR+SD) was 80%. The sunitinib patient previously refractory to sorafenib had a 38% reduction in tumor size. The most noticeable organ-specific response was observed in lung (median change, -22%) compared to lymph nodes (median change, 0%). Pleural disease and nonirradiated bone metastases demonstrated PD. All histological subtypes had similar responses. The median PFS was 19 months. The median overall survival has not yet been reached, but at 2 yr of follow-up, overall survival is 67%. Log Tg correlated with radiographic response (P = 0.0005).

CONCLUSIONS

Sorafenib and sunitinib appear to be effective in patients with widely metastatic, progressive DTC, with most patients achieving SD or PR, despite having PD at baseline. The most noticeable responses occurred in the lungs in contrast with minimal changes in nodal metastases and PD in pleural and nonirradiated bone metastases, suggesting a tissue-specific response to therapy. Log Tg significantly correlated with response to treatment and therefore may have value as a surrogate marker of response.

Vandetanib (100 mg) in patients with locally advanced or metastatic hereditary medullary thyroid cancer

PURPOSE

Vandetanib is a once-daily oral inhibitor of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinases that also inhibits rearranged during transfection kinase activity. Vandetanib (300 mg/d) has previously demonstrated antitumor activity in patients with advanced hereditary medullary thyroid cancer (MTC). This study investigated the efficacy and safety of 100 mg/d vandetanib in patients with advanced hereditary MTC.

PATIENTS AND METHODS

Eligible patients with unresectable, measurable, locally advanced, or metastatic hereditary MTC received 100 mg/d vandetanib. Upon disease progression, eligible patients could enter postprogression treatment with 300 mg/d vandetanib until a withdrawal criterion was met. The primary objective was to assess the objective response rate by response evaluation criteria in solid tumors.

RESULTS

The study comprised 19 patients (13 males, six females; mean age 45 yr). Confirmed objective partial responses were observed in three patients, yielding an objective response rate of 16% (95% confidence interval 3.4-39.6). Stable disease lasting 24 wk or longer was reported in a further 10 patients (53%); the disease control rate was therefore 68% (95% confidence interval 43.4-87.4). Serum levels of calcitonin and carcinoembryonic antigen showed a sustained 50% or greater decrease from baseline in 16% (three of 19) and 5% (one of 19) of patients, respectively. Adverse events were predominantly grade 1 or 2 and consistent with previous vandetanib monotherapy studies.

CONCLUSIONS

Vandetanib at a once-daily dose of 100 mg has clinically relevant antitumor activity in patients with locally advanced or metastatic hereditary MTC and an overall acceptable safety profile.

The PI3K-Akt-mTOR pathway in initiation and progression of thyroid tumors

The phosphoinositide-3 (OH) kinase (PI3K) signaling cascade is involved in regulating glucose uptake and metabolism, growth, motility, and other essential functions for cell survival. Unregulated activation of this pathway commonly occurs in cancer through a variety of mechanisms, including genetic mutations of kinases and regulatory proteins, epigenetic alterations that alter gene expression and translation, and posttranslational modifications. In thyroid cancer, constitutive activation of PI3K signaling has been shown to play a role in the genetic predisposition for thyroid neoplasia in Cowden's syndrome, and is recognized to be frequently overactivated in sporadic forms of thyroid cancer including those with aggressive clinical behaviors. In this review, the key signaling molecules in the PI3K signaling cascade, the abnormalities known to occur in thyroid cancer, and the potential for therapeutic targeting of PI3K pathway members will be discussed.

Targeted therapy of thyroid cancer

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes. Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single agent studies, but prolonged disease stabilization is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. Additional agents targeting tumor vasculature, nuclear receptors, epigenetic abnormalities, and the immune response to neoplasia have also been investigated. Randomized trials for several agents are underway that may lead to eventual drug approval for thyroid cancer. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Phase II clinical trial of sorafenib in metastatic medullary thyroid cancer

PURPOSE

Mutations in the RET proto-oncogene and vascular endothelial growth factor receptor (VEGFR) activity are critical in the pathogenesis of medullary thyroid cancer (MTC). Sorafenib, a multikinase inhibitor targeting Ret and VEGFR, showed antitumor activity in preclinical studies of MTC.

PATIENTS AND METHODS

In this phase II trial of sorafenib in patients with advanced MTC, the primary end point was objective response. Secondary end points included toxicity assessment and response correlation with tumor markers, functional imaging, and RET mutations. Using a two-stage design, 16 or 25 patients were to be enrolled onto arms A (hereditary) and B (sporadic). Patients received sorafenib 400 mg orally twice daily.

RESULTS

Of 16 patients treated in arm B, one achieved partial response (PR; 6.3%; 95% CI, 0.2% to 30.2%), 14 had stable disease (SD; 87.5%; 95% CI, 61.7% to 99.5%), and one was nonevaluable. In a post hoc analysis of 10 arm B patients with progressive disease (PD) before study, one patient had PR of 21+ months, four patients had SD >or= 15 months, four patients had SD

CONCLUSION

Sorafenib is reasonably well tolerated, with suggestion of clinical benefit for patients with sporadic MTC. Caution should be taken because of the rare but fatal toxicity potentially associated with sorafenib.

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Key Words Collapse

MESH Headings

• Administration, Oral
• Adult
• Aged
• Benzenesulfonates/administration & dosage
• Benzenesulfonates/adverse effects
• Benzenesulfonates/therapeutic use
• Biomarkers, Tumor/metabolism
• Carcinoma, Medullary/drug therapy
• Carcinoma, Medullary/enzymology
• Carcinoma, Medullary/genetics
• Carcinoma, Medullary/mortality
• Carcinoma, Medullary/secondary
• Disease-Free Survival
• Female
• Humans
• Kaplan-Meier Estimate
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Mutation
• Niacinamide/analogs & derivatives
• Phenylurea Compounds
• Positron-Emission Tomography
• Protein Kinase Inhibitors/administration & dosage
• Protein Kinase Inhibitors/adverse effects
• Protein Kinase Inhibitors/therapeutic use
• Proto-Oncogene Mas
• Proto-Oncogene Proteins c-ret/antagonists & inhibitors
• Proto-Oncogene Proteins c-ret/genetics
• Pyridines/administration & dosage
• Pyridines/adverse effects
• Pyridines/therapeutic use
• Receptors, Vascular Endothelial Growth Factor/antagonists & inhibitors
• Sorafenib
• Thyroid Neoplasms/drug therapy
• Thyroid Neoplasms/enzymology
• Thyroid Neoplasms/genetics
• Thyroid Neoplasms/mortality
• Thyroid Neoplasms/pathology
• Time Factors
• Tomography, X-Ray Computed
• Treatment Outcome
• United States
• Young Adult

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Grants

• N01 CM062207 NCI NIH HHS
• N01-CM-62207 NCI NIH HHS

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Affiliation(s)

Elaine T Lam Departments of Internal Medicine, Center for Biostatistics, The Ohio State University, Columbus, OH, USA.
Matthew D Ringel
Richard T Kloos
Thomas W Prior
Michael V Knopp
Jiachao Liang
Steffen Sammet
Nathan C Hall
Paul E Wakely
Vasyl V Vasko
Motoyasu Saji
Pamela J Snyder
Lai Wei
Daria Arbogast
Minden Collamore
John J Wright
Jeffrey F Moley
Miguel A Villalona-Calero
Manisha H Shah

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Collaborators Collapse

Pazopanib: Clinical development of a potent anti-angiogenic drug

Pazopanib is an oral, multi-targeted, tyrosine kinase inhibitor (TKI) that binds to the vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and several other key proteins responsible for angiogenesis, tumor growth and cell survival. Pazopanib exhibited in vivo and in vitro activity against tumor growth and, in early clinical trials, was well tolerated with the main side effects being hypertension, fatigue and gastrointestinal disorders. Pazopanib showed clinical activity in several tumors including renal cell cancer (RCC), breast cancer, soft tissue sarcoma, thyroid cancer, hepatocellular cancer and cervical cancer. A phase III clinical trial in metastatic RCC patients showed a significant improvement in progression-free survival, leading to its approval in the US. In metastatic breast cancer, the combination of pazopanib with lapatinib was more effective than lapatinib alone. At the time of the current publication, pazopanib is being evaluated in more than 35 phase II and III trials.

Old and new insights in the treatment of thyroid carcinoma

Thyroid cancer is the endocrine tumor that bears the highest incidence with 33 550 new cases per year. It bears an excellent prognosis with a mortality of 1530 patients per year (Jemal et al.; 2007). We have been treating patients with thyroid carcinoma during many years without many innovations. Recently, we have assisted to the development of new agents for the treatment of this disease with unexpected good results. Here we present a review with the old and new methods for the treatment of this disease.

Effect of axitinib (AG-013736) on fatigue, thyroid-stimulating hormone, and biomarkers: a phase I study in Japanese patients

Axitinib is an oral, potent, and selective inhibitor of vascular endothelial growth factor receptor (VEGFR) 1, 2, and 3. This phase I study evaluated the safety, pharmacokinetics, pharmacodynamics, antitumor activity, and recommended starting dose of axitinib in patients with advanced solid tumors. Twelve patients received single-dose axitinib 5 mg and were monitored for > or =48 h. Continuous 5 mg twice-daily dosing was then initiated. One patient had dose-limiting toxicity (grade 3 proteinuria and fatigue). Common treatment-related adverse events were anorexia, fatigue, and diarrhea. Grade 3 treatment-related adverse events were fatigue and hypertension. Maximum axitinib plasma concentration occurred 1-4 h after steady-state dosing. Eleven patients experienced thyroid-stimulating hormone elevation; time-course change and fatigue onset appeared to be related in some patients. Significant correlation was observed between thyroid-stimulating hormone change and area under the plasma concentration-time curve (AUC; r = 0.80, P = 0.005). Axitinib decreased plasma soluble vascular endothelial growth factor receptor 2 (s-VEGFR2), with significant correlation between change in s-VEGFR2 and AUC (r = -0.92, P < 0.0001). Fluorodeoxyglucose positron emission tomography revealed a substantial decrease in tumor metabolic activity associated with axitinib. Tumor size decreased in nine patients. The time-course of thyroid-stimulating hormone change appeared correlated with fatigue. There were significant correlations between thyroid-stimulating hormone or s-VEGFR2 and axitinib exposure. Axitinib 5 mg twice-daily is the recommended starting dose for Japanese patients. This trial is registered with ClinicalTrials.gov, identifier NCT00447005.

Angiogenesis-inhibitors for metastatic thyroid cancer

BACKGROUND

Systemic cytostatic therapies for advanced, metastatic thyroid carcinomas have been poorly effective. Tumor growth and metastasis depend on blood supply and blood vessel formation (angiogenesis). Therefore, inhibition of angiogenesis may represent a promising target for cancer therapy.

OBJECTIVES

To evaluate the benefits and risks of angiogenesis-inhibitors for metastatic thyroid cancer when given alone, or in combination with chemotherapy or radiotherapy.

SEARCH STRATEGY

We searched The Cochrane Library (2009, Issue 2), MEDLINE (January 2000 to May 2009) and EMBASE (January 2000 to May 2009) databases and abstracts published in annual proceedings for evidence. Attempts were made to identify studies from references in potentially relevant trials. We also searched for ongoing trials.

SELECTION CRITERIA

We planned to include randomized controlled trials that compared angiogenesis-inhibitors with other treatments, no treatment, or placebo in participants who had pathologically confirmed advanced thyroid cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated the search results against the selection criteria. Data extraction and risk of bias assessment were not performed because there were no studies that could be included.

MAIN RESULTS

We did not identify any studies which met our full inclusion criteria.

AUTHORS' CONCLUSIONS

There is currently no reliable evidence available from randomized controlled trials regarding the bene fi ts and harms of the use of angiogenesis-inhibitors for treating advanced thyroid cancer. Several trials are ongoing.

BRAF mutation in papillary thyroid carcinoma: pathogenic role and clinical implications

Papillary thyroid cancer (PTC) is the most common endocrine malignancy, accounting for 85-90% of all thyroid cancers. Genetic alternations involving the mitogen-activated protein kinase (MAPK) pathway are frequently demonstrated in PTC, such as RET/PTC, RAS, and B-type Raf kinase (BRAF) mutations. Over 90% of BRAF mutations are T1799A, resulting in a BRAF(V600E) mutation. BRAF(V600E) is present in approximately 50% of PTC and also found in aggressive histologic variants and PTC-derived anaplastic thyroid cancer, but is rare in follicular variants, and not found in follicular thyroid cancer. The tumorigenic role of BRAF(V600E) in the development of PTC was documented in thyroid-targeted BRAF(V600E) transgenic mice, and rat thyroid cells overexpressed with BRAF(V600E) suggested that BRAF(V600E) is an initiator of tumorigenesis and is required for tumor progression in PTC. Most clinical studies have demonstrated an association of BRAF(V600E) mutation with aggressive clinicopathologic characteristics and high tumor recurrence, although the results are controversial. The association is also observed in patients with papillary thyroid microcarcinomas and low-risk PTC. As a highly specific and unique mutation in PTC, testing for BRAF(V600E) in fine-needle aspiration specimens has been shown to refine the diagnostic accuracy of PTC in indeterminate cytology. Preoperative BRAF(V600E) analysis in low-risk patients may provide important value for prognostication, and these patients might benefit from receiving more intensive management and frequent follow-up. BRAF-targeted therapies have been developed to treat various human cancers including advanced thyroid cancers. Preclinical results are encouraging, but the anticancer effects of clinical trials are disappointing. Studies of multi-kinase inhibitors and/or combination with other regimens are underway in the treatment of advanced thyroid cancers. In this article, we review the pathogenesis of PTC, and the clinical implications of BRAF(V600E) mutation in the diagnosis, prognosis and potential targeted therapeutic strategies for thyroid cancers.

Novel VEGF signalling inhibitors: how helpful are biomarkers in their early development?

BACKGROUND

The development of vascular endothelial growth factor (VEGF) inhibitors of tumour angiogenesis can only be described as prolific. It is therefore interesting to speculate which will reach the clinic. Of course, the most effective agents will succeed, but how is effectiveness measured? When presented with a summary of competitive compounds, it can be difficult to discriminate between their potency on target, toxicity and response rates.

OBJECTIVES

A comparison was undertaken between new small-molecule tyrosine kinase inhibitors with vascular endothelial growth factor receptor as one of their targets. Factors considered included mode of action (targets), toxicity and usefulness of biomarker data.

METHODOLOGY

We carried out a systematic review using PubMed, MEDLINE and American Society of Clinical Oncologist (ASCO) databases for articles (including abstracts) presented in 2007 - 2009. Search terms included 'angiogenesis inhibitors', 'tyrosine kinase inhibitors', 'VEGF' and 'biomarkers'. Nine compounds were selected for detailed comparison.

RESULTS AND CONCLUSIONS

The toxicity profiles of the compounds were similar. Many exposure biomarkers have been identified that have informed the dose and scheduling of these compounds in clinical trials. Progress has also been made in identifying potential efficacy and predictive biomarkers for these new agents; however, these are yet to be validated.

Standard and emerging therapies for metastatic differentiated thyroid cancer

Differentiated thyroid cancer accounts for >90% of cases of thyroid cancer, with most patients having an excellent prognosis. Distant metastases occur in 10%-15% of patients, decreasing the overall 10-year survival rate in this group to 40%. Radioactive iodine has been the mainstay of treatment for distant metastases, with good results when lesions retain the ability to take up iodine. For patients with metastatic disease resistant to radioactive iodine, treatment options are few and survival is poor. Chemotherapy and external beam radiotherapy have been used in these patients, but with disappointing results. In recent years, our understanding of the molecular pathways involved in thyroid cancer has increased and a number of molecular targets have been identified. These targets include the proto-oncogenes BRAF and RET, known to be common mutations in thyroid cancer; vascular endothelial growth factor receptor and platelet-derived growth factor receptor, associated with angiogenesis; and the sodium-iodide symporter, with the aim of restoring its expression and hence radioactive iodine uptake. There are now multiple trials of tyrosine kinase inhibitors, angiogenesis inhibitors, and other novel agents available to patients with metastatic thyroid cancer. This review discusses both traditional and novel treatments for metastatic differentiated thyroid cancer with a particular focus on emerging treatments for patients with radioactive iodine-refractory disease.

Current concepts and future directions in differentiated thyroid cancer

This paper provides an overview on the biology, monitoring and management of differentiated thyroid cancer (DTC), with particular attention to issues of relevance to clinical chemistry. The incidence of DTC appears to be increasing and management strategies are evolving as we learn more about its natural history and response to therapy. Clinical chemistry techniques play a central role in these protocols. Technical limitations inherent in current monitoring tools can hamper follow-up, although progress is being made. The molecular basis of DTC is being delineated with the potential to develop new strategies for diagnosis, monitoring and management of this condition.

Effect of rifampin on the pharmacokinetics of Axitinib (AG-013736) in Japanese and Caucasian healthy volunteers

PURPOSE

Axitinib, a potent and selective inhibitor of vascular endothelial growth factor receptors 1, 2, 3, is metabolized by cytochrome P450 3A4 and glucuronidation. This study evaluated the effect of rifampin, a potent inducer of drug-metabolizing enzymes, on axitinib plasma pharmacokinetics. Equal numbers of Japanese and Caucasian subjects were enrolled to assess the potential differences in axitinib pharmacokinetics between the two ethnicities.

METHODS

Forty healthy volunteers were randomized to receive 5 mg axitinib alone and with 600 mg rifampin.

RESULTS

Rifampin expectedly decreased AUCinf and Cmax of axitinib (geometric mean reduced by 79 and 71%, respectively). However, differences in axitinib pharmacokinetics were not observed between Japanese and Caucasian subjects (geometric mean ratios for axitinib treatment alone for AUCinf and Cmax were 103 and 96%).

CONCLUSIONS

The results support a common axitinib starting dose in both populations. Potent inducers of drug-metabolizing enzymes reduce axitinib exposure and dose adjustments may be needed for optimal efficacy.

Molecularly targeted therapies for thyroid cancers

OBJECTIVE

To review the emerging evidence that therapies targeting key oncogenic and signaling kinases can be effective in treatment of advanced thyroid carcinomas.

METHODS

With use of PubMed and Google Scholar, a systematic review was performed of publications and scientific presentations summarizing pertinent clinical trials.

RESULTS

Studies of numerous inhibitors of BRAF, vascular endothelial growth factor receptor, and RET kinases indicate that patients with progressive or metastatic thyroid carcinoma can benefit from therapy with these novel agents. Severe toxic effects, however, are associated with these treatments, and caution is recommended in their use.

CONCLUSION

Further trials and identification of improved therapeutic targeting should lead to development of more effective treatments of thyroid carcinomas.

Targeting vascular endothelial growth factor receptor in thyroid cancer: the intracellular and extracellular implications

Our understanding of the molecular pathophysiology of differentiated thyroid cancer (DTC) has developed considerably over the last 10 years. Aberrant signaling through B-Raf and Akt has been implicated in the tumorigenesis of DTC. Moreover, these highly vascular tumors have proven to be sensitive to the inhibition of vascular endothelial growth factor receptor (VEGFR-2). It is likely that the multikinase inhibitors, sorafenib, sunitinib, axitinib, and motesanib, whose targets include VEGFR-2, exert their effects primarily through inhibition of endothelial cells. However, as VEGFR-2 is expressed on DTC cells, these compounds may have direct antitumor action. This review will discuss the key signaling pathways involved in thyroid cancer and their implications for targeted therapy.

Axitinib (AG-013736)

The vascular endothelial growth factor (VEGF)/VEGF receptor tyrosine kinase (RTK) signaling pathway plays a pivotal role in tumor angiogenesis. Neovascularization promotes increased tumor cell proliferation, survival and metasasis. Many antiangiogenic agents including multi-RTK inhibitors are either approved or are undergoing testing in clinical trials. Axitinib is a potent and selective inhibitor of VEGF RTK 1, 2, and 3. This chapter discusses the stucture of axitinib as well as its toxicities and drug interactions. Important preclinical and clinical data for axitinib are presented including findings from phase II studies in many tumor types including malignant melanoma and renal, pancreatic, thyroid, breast, lung and colorectal carcinomas. Ongoing phase III studies in pancreatic and metastatic renal cell carcinoma will ultimately define the therapeutic role of this targeted agent.

Medullary thyroid carcinoma: targeted therapies and future directions

Medullary thyroid cancer (MTC) is a rare neuroendocrine neoplasm that accounts for approximately 5% of all thyroid malignancies. The natural history of MTC is characterized by early lymph node and distant metastases, making complete surgical cure often impossible. Conventional chemotherapy and external beam radiation have been largely ineffective in altering the natural history of MTC. Therefore, there is a great need to develop novel therapeutic strategies to affect symptom control and reduce tumor burden in patients with widely disseminated disease. Here, we review several pathways which have been shown to be vital in MTC tumorigenesis and focus on the pathways of interest for which targeted drug therapies are currently being developed.

VEGF signalling inhibition-induced proteinuria: Mechanisms, significance and management

Proteinuria is a dose-related side-effect occurring after inhibition of vascular endothelial growth factor (VEGF) signalling and may reflect severe glomerular damage. The inhibition of the VEGF signalling axis induces downexpression or suppression of nephrin, an important protein for the maintenance of the glomerular slit diaphragm, sometimes leading to nephritic syndrome and/or glomerular thrombotic microangiopathy, the main-associated kidney disease. A MEDLINE search was carried out using the following criteria: (1) all MEDLINE listings as of 01-01-2000 with abstracts; (2) English language; and (3) Humans. The following phrases were used to query the database: (proteinuria) AND (anti-VEGF OR VEGF inhibition OR bevacizumab OR sunitinib OR sorafenib OR VEGF Trap OR axitinib OR pazopanib OR AZ 2171). The references of each article identified were carefully reviewed for additional reference. The incidence of mild and asymptomatic proteinuria ranges from 21% up to 63%, but heavy proteinuria has been reported in up to 6.5% of renal cell carcinoma patients. Although discontinuation of anti-VEGF agent induced significant reduction, persistence of proteinuria is common. Although angiotensinconverting-enzyme inhibitors and/or angiotensin receptor blockers seem to be preferred, no specific recommendation for an antiproteinuric agent can be made in this context because there are no controlled studies addressing the subject. Periodic monitoring of urinary protein should be carried out in anti-VEGF-treated patients and patients showing proteinuria need special referral to nephrologists.

Clinical trials for progressive differentiated thyroid cancer: patient selection, study design, and recent advances

Treatment of metastatic differentiated thyroid cancer is first based on the use of radioiodine and thyrotropin-suppressive thyroid hormone treatment. The recent availability of molecular-targeted therapies has lead to reconsideration of the treatment strategy in differentiated thyroid cancer patients with distant metastases who are resistant to radioiodine therapy. In those with progressive disease, treatment with kinase inhibitors should be offered preferably in the context of a prospective trial.

Tyrosine kinase inhibitors and the thyroid

Protein tyrosine kinase inhibitors (TKIs) have emerged as significant targets for novel cancer therapies. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, multiple novel therapies primarily targeting angiogenesis have entered clinical trials. Partial response rates up to 30% have been reported in single-agent studies, but prolonged disease stabilisation is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors. Sorafenib and sunitinib have had promising preliminary results reported and are being used selectively for patients who do not qualify for clinical trials. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasises clinical trial opportunities for novel agents with considerable promise. Adverse effects on thyroid function and thyroid hormone metabolism have also been seen with several TKIs, necessitating prospective thyroid function testing for all patients starting therapy.

Lessons from mouse models of thyroid cancer

BACKGROUND

Thyroid cancer is the most common endocrine tumor and is increasing in incidence. The aim of this study was to review mouse models of differentiated thyroid cancer and how they elucidate human thyroid cancer biology.

SUMMARY

Differentiated thyroid cancer, primarily papillary and follicular, comprises the majority of thyroid cancers. There has been tremendous growth in the cross-talk between basic science and clinical practice for thyroid cancer management. Insight into the framework of genes responsible for differentiated thyroid cancer has been gained through the use of mouse models. Common genetic alterations found in human papillary thyroid cancer such as RET/PTC rearrangements or the BRAF(V600E) mutation have genetically modified mouse counterparts. These and other preclinical mouse models have validated the importance of the cyclic adenosine monophosphate (cAMP)/protein kinase A and mitogen-activated protein kinase (MAPK) signaling pathways in papillary thyroid cancer (PTC). RAS mutations have a role in both papillary and follicular thyroid cancer development. Mice with overactivation of the phosphatidylinol-3-kinase (PI3K)-AKT and/or thyrotropin-regulated signaling pathways have been found to develop follicular thyroid cancer. Additional mouse models of thyroid cancer that utilize inducible expression systems are in development or are being characterized and will better reflect the majority of human thyroid cancers which are non-hereditary. Advances in in vivo imaging of mice allow for earlier detection of metastasis and the ability to follow tumor growth or regression which may be used in evaluation of pharmaceutical agents.

CONCLUSIONS

Mouse models have expanded our understanding of the altered signaling pathways that contribute to thyroid cancer tumorigenesis and provide a powerful tool to develop novel diagnostic approaches and therapies.

Targeting the RET pathway in thyroid cancer

The RET (rearranged during transfection) protooncogene encodes a single pass transmembrane receptor that is expressed in cells derived from the neural crest and the urogenital tract. As part of a cell-surface complex, RET binds glial derived neurotrophic factor (GDNF) ligands in conjunction with GDNF-family alpha co-receptors (GFRalpha). Ligand-induced activation induces dimerization and tyrosine phosphorylation of the RET receptor with downstream activation of several signal transduction pathways. Activating germline RET mutations play a central role in the development of the multiple endocrine neoplasia (MEN) syndromes MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC) and also in the development of the congenital abnormality Hirschsprung's disease. Approximately 50% of patients with sporadic MTC have somatic RET mutations, and a significant portion of papillary thyroid carcinomas result from chromosomal inversions or translocations, which activate RET (RET/PTC oncogenes). The RET protooncogene has a significant place in cancer prevention and treatment. Timely thyroidectomy in kindred members who have inherited a mutated RET allele, characteristic of MEN2A, MEN2B, or FMTC, can prevent MTC, the most common cause of death in these syndromes. Also, recently developed molecular therapeutics that target the RET pathway have shown activity in clinical trials of patients with advanced MTC, a disease for which there has been no effective therapy.

A phase I study of axitinib (AG-013736) in combination with bevacizumab plus chemotherapy or chemotherapy alone in patients with metastatic colorectal cancer and other solid tumors

BACKGROUND

Axitinib and bevacizumab are targeted therapies against the vascular endothelial growth factor pathway.

METHODS

Patients with previously treated solid tumors received axitinib (starting dose 5 mg twice daily) combined with FOLFOX plus bevacizumab (1, 2, or 5 mg/kg, cohorts 1-3, respectively), FOLFIRI (cohort 4), or FOLFOX (cohort 5). Safety and pharmacokinetics were assessed.

RESULTS

Thirty patients were enrolled (n = 16, 8, and 6 for cohorts 1-3, 4, and 5, respectively). Plasma concentrations and pharmacokinetic (PK) parameters were similar when drugs were administered alone and in various combinations. Most treatment-emergent adverse events (AEs) were mild to moderate and clinically manageable (most common: nausea, fatigue, diarrhea, anorexia, hypertension). Two of the four patients receiving axitinib with FOLFOX plus 5 mg/kg bevacizumab experienced dose-limiting toxicity (DLT) of inability to resume treatment for 14 days following treatment interruption (associated AE: hypertension); the maximum tolerated dose of bevacizumab in this combination was 2 mg/kg. No DLTs occurred with axitinib plus FOLFIRI or FOLFOX. Ten patients had RECIST-confirmed partial tumor responses (objective response rate: 33.3%).

CONCLUSION

Axitinib is well tolerated in combination with FOLFOX, FOLFIRI, or FOLFOX plus 2 mg/kg bevacizumab. PK interactions appear to be absent.

Targeted therapies in thyroid cancer

Differentiated thyroid carcinoma is the most frequent neoplasm of the endocrine system. Although thyroid cancer usually has an excellent prognosis, no therapeutic options are available for patients that develop metastases and are or became resistant to radioiodine therapy. The deeper knowledge of molecular aberrations that characterize tumor growth has provided novel targets in cancer therapy. Several proteins have been implicated as having a crucial role in the carcinogenesis of differentiated thyroid cancer, such as those involved in RET/PTC-RAS-RAF-MAPK pathway. Moreover, vascular aberrations and angiogenesis equilibrium have also been related to tumor growth. The development of new, targeted therapies and their encouraging initial results have opened a hopeful opportunity of treatment for these orphan therapy tumor patients.

Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer

BACKGROUND

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the publication of the American Thyroid Association's guidelines for the management of these disorders was published in 2006, a large amount of new information has become available, prompting a revision of the guidelines.

METHODS

Relevant articles through December 2008 were reviewed by the task force and categorized by topic and level of evidence according to a modified schema used by the United States Preventative Services Task Force.

RESULTS

The revised guidelines for the management of thyroid nodules include recommendations regarding initial evaluation, clinical and ultrasound criteria for fine-needle aspiration biopsy, interpretation of fine-needle aspiration biopsy results, and management of benign thyroid nodules. Recommendations regarding the initial management of thyroid cancer include those relating to optimal surgical management, radioiodine remnant ablation, and suppression therapy using levothyroxine. Recommendations related to long-term management of differentiated thyroid cancer include those related to surveillance for recurrent disease using ultrasound and serum thyroglobulin as well as those related to management of recurrent and metastatic disease.

CONCLUSIONS

We created evidence-based recommendations in response to our appointment as an independent task force by the American Thyroid Association to assist in the clinical management of patients with thyroid nodules and differentiated thyroid cancer. They represent, in our opinion, contemporary optimal care for patients with these disorders.

Phase I clinical trials in 56 patients with thyroid cancer: the M. D. Anderson Cancer Center experience

INTRODUCTION

Thyroid cancer is the most common endocrine malignancy. The outcomes of patients with relapsed thyroid cancer treated on early-phase clinical trials have not been systematically analyzed.

PATIENTS AND METHODS

We reviewed the records of consecutive patients with metastatic thyroid cancer referred to the Phase I Clinical Trials Program from March 2006 to April 2008. Best response was assessed by Response Evaluation Criteria in Solid Tumors.

RESULTS

Fifty-six patients were identified. The median age was 55 yr (range 35-79 yr). Of 49 patients evaluable for response, nine (18.4%) had a partial response, and 16 (32.7%) had stable disease for 6 months or longer. The median progression-free survival was 1.12 yr. With a median follow-up of 15.6 months, the 1-yr survival rate was 81%. In univariate analysis, factors predicting shorter survival were anaplastic histology (P = 0.0002) and albumin levels less than 3.5 g/dl (P = 0.05). Among 26 patients with tumor decreases, none died (median follow-up 1.3 yr), whereas 52% of patients with any tumor increase died by 1 yr (P = 0.0001). The median time to failure in our phase I clinical trials was 11.5 months vs. 4.1 months for the previous treatment (P = 0.04).

CONCLUSION

Patients with advanced thyroid cancer treated on phase I clinical trials had high rates of partial response and prolonged stable disease. Time to failure was significantly longer on the first phase I trial compared with the prior conventional treatment. Patients with any tumor decrease had significantly longer survival than those with any tumor increase.

Liquid chromatography-tandem mass spectrometric assay for the light sensitive tyrosine kinase inhibitor axitinib in human plasma

A bioanalytical assay for the new tyrosine kinase inhibitor axitinib was developed and validated. In addition, the light mediated trans to cis isomerization of this drug was investigated. For the quantitative assay, human plasma samples were pre-treated under light protection using protein precipitation with acetonitrile containing erlotinib as the internal standard. The extract was diluted with water and injected into the chromatographic system. The system consisted of a trifunctional bonded octadecyl silica column with isocratic elution using formic acid in a water-methanol mixture. The eluate was transferred into an electrospray interface with positive ionization and the analyte was detected and quantified using the selected reaction monitoring mode of a triple quadrupole mass spectrometer. The assay was validated in a 0.2-200ng/ml concentration range, the lowest level of this range being the lower limit of quantification. Within day precisions were 2.5-6%, between day precisions 4-9% and accuracies were between 91 and 106% for the whole calibration range. Light protected axitinib showed no isomerization and was shown to be chemically stable under all relevant conditions. Finally, the assay was successfully applied for a mouse tissue distribution study using mouse samples diluted with human plasma.

Recommendations of the Latin American Thyroid Society on diagnosis and management of differentiated thyroid cancer

The aims of these recommendations were to develop clinical guidelines for evaluation and management of patients with differentiated thyroid cancer applicable to Latin American countries. The panel was composed by 13 members of the Latin American Thyroid Society (LATS) involved with research and management of thyroid cancer from different medical centers in Latin America. The recommendations were produced on the basis of the expert opinion of the panel with use of principles of Evidence-Based Medicine. Following a group meeting, a first draft based on evidences and the expert opinions of the panel was elaborated and, later, circulated among panel members, for further revision. After, this document was submitted to the LATS members, for commentaries and considerations, and, finally, revised and refined by the authors. The final recommendations presented in this paper represent the state of the art on management of differentiated thyroid cancer applied to all Latin American countries.

Novel treatment of medullary thyroid cancer

PURPOSE OF REVIEW

Metastatic medullary thyroid cancer (MTC) is an incurable disease once metastasis becomes unresectable. Many therapeutic drugs and methods have been tried to circumvent this difficulty. We review currently published treatments and hope for future developments of more effective treatment methods.

RECENT FINDINGS

Motesanib, vandetanib, axitinib (tyrosine kinase inhibitors), and XL184 (multikinase inhibitor) have been shown to achieve partial response or stable disease state of metastatic MTC. Sunitinib and sorafenib, currently available tyrosine kinase inhibitors, can also be tried for patients with MTC. However, these medications are not curative and do not improve survival rate. Only carcinoembryonic antigen-I-iodine-based radioimmunotherapy improved survival of a subset of patients with a very aggressive type of MTC. Drugs currently available for possible use of MTC treatment include bortezomib (proteasome inhibitor), valproic acid (histone deacetylase inhibitor), capecitabine (5-fluorouracil prodrug), and indomethacin (NSAID), although clinical studies have yet to be done. Cardiac natriuretic hormones and an extract of the plant Cautleya gracilis are new agents to be studied for MTC.

SUMMARY

Kinase inhibitors are the first drugs showing some efficacy in MTC. To improve survival, unconventional drugs or other therapies with or without kinase inhibitors need to be considered.

Genetic alterations in the phosphoinositide 3-kinase/Akt signaling pathway confer sensitivity of thyroid cancer cells to therapeutic targeting of Akt and mammalian target of rapamycin

We investigated the genotype-dependent therapeutic potential of targeting the phosphoinositide 3-kinase (PI3K)/Akt pathway for thyroid cancer. Proliferation of TPC1, Hth7, FTC133, OCUT1, K1, and BCPAP cells that harbored PI3K/Akt-activating genetic alterations was potently inhibited by the Akt inhibitor perifosine, whereas SW1736, Hth74, WRO, KAT18, and TAD2 cells that harbored no genetic alterations had no or only modest responses. Inhibition of Akt phosphorylation by perifosine was seen in these cells. Genetic-dependent apoptosis was induced by perifosine in cells selectively tested. Similarly, potent inhibition of cell proliferation by the mammalian target of rapamycin (mTOR) inhibitor temsirolimus occurred in virtually all the cells harboring genetic alterations, whereas modest inhibition was seen in some of the cells not harboring genetic alterations. Temsirolimus inhibited the phosphorylation of p70S6K, a substrate of mTOR. Knockdown of Akt1/2 or mTOR by shRNA approach inhibited the proliferation and colony formation of FTC133 and OCUT1 cells that harbored genetic alterations in the PI3K/Akt pathway but had no effect on SW1736 and KAT18 cells that did not. Transfection with PIK3CA mutants greatly sensitized SW1736 cells to perifosine and temsirolimus. Growth of xenograft tumors derived from FTC133 cells but not SW1736 cells in nude mice was dramatically inhibited by perifosine. Thus, this work for the first time shows that genetic alterations in the PI3K/Akt pathway confer thyroid cancer cells addiction to this pathway and their sensitivity to inhibition by targeting Akt and mTOR. This genotype-based targeting of the PI3K/Akt pathway using Akt and mTOR inhibitors may offer an effective therapeutic strategy for thyroid cancer and warrants further studies.

Phase II study of safety and efficacy of motesanib in patients with progressive or symptomatic, advanced or metastatic medullary thyroid cancer

PURPOSE

This phase II study investigated the efficacy and tolerability of motesanib, an investigational, highly selective inhibitor of vascular endothelial growth factor receptors 1, 2, and 3; platelet-derived growth factor receptor; and Kit in advanced medullary thyroid cancer (MTC).

PATIENTS AND METHODS

Patients with locally advanced or metastatic, progressive or symptomatic MTC received motesanib 125 mg/d orally for up to 48 weeks or until unacceptable toxicity or disease progression. The primary end point was objective response by independent review. Other end points included duration of response, progression-free survival, safety, pharmacokinetics, and changes in tumor markers.

RESULTS

Of 91 enrolled patients who received motesanib, two (2%) achieved objective response (95% CI, 0.3% to 7.7%); their duration of response was 32 weeks (censored) and 21 weeks (disease progressed). Eighty-one percent of patients had stable disease (48% had durable stable disease > or = 24 weeks), 8% had disease progression as best response, and 9% were not evaluated; 76% experienced a decrease from baseline in target lesion measurement. Median progression-free survival was 48 weeks (95% CI, 43 to 56 weeks). Among patients with tumor marker analysis, 69 (83%) of 83 and 63 (75%) of 84 had decreased serum calcitonin and carcinoembryonic antigen during treatment, respectively, compared with baseline. The most common treatment-related adverse events were diarrhea (41%), fatigue (41%), hypothyroidism (29%), hypertension (27%), and anorexia (27%). In pharmacokinetic analyses, motesanib trough concentrations were lower compared with differentiated thyroid cancer patients from the same study.

CONCLUSION

Although the objective response rate was low, a significant proportion of MTC patients (81%) achieved stable disease while receiving motesanib.

Changing the clinical picture of challenging tumors: tales becoming reality?

The treatment of neoplastic diseases has become increasingly dependent on tumor biology and is focused on targeted therapy. Understanding complex networks of intracellular signaling pathways, blockades of specific targets and a myriad of other approaches has brought new fuel to the battle against many types of cancer. Unfortunately, the degree of benefit achieved in this new era of cancer treatment has not been distributed homogeneously among the different disease types. Neoplasms with lower incidence rates, but that are also highly challenging, are not consistently given due attention by research leaders. This article aims to evaluate new insights and potential gains obtained with new therapies in a particular group of tumors: those rarely debated in clinical practice, but which still pose a considerable challenge to clinical oncology.