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

Vandetanib in locally advanced or metastatic differentiated thyroid cancer: a randomised, double-blind, phase 2 trial

BACKGROUND

No effective standard treatment exists for patients with radioiodine-refractory, advanced differentiated thyroid carcinoma. We aimed to assess efficacy and safety of vandetanib, a tyrosine kinase inhibitor of RET, VEGFR and EGFR signalling, in this setting.

METHODS

In this randomised, double-blind, phase 2 trial, we enrolled adults (aged ≥18 years) with locally advanced or metastatic differentiated thyroid carcinoma (papillary, follicular, or poorly differentiated) at 16 European medical centres. Eligible patients were sequentially randomised in a 1:1 ratio with a standard computerised scheme to receive either vandetanib 300 mg per day (vandetanib group) or matched placebo (placebo group), balanced by centre. The primary endpoint was progression-free survival (PFS) in the intention-to-treat population based on investigator assessment. This study is registered with ClinicalTrials.gov, number NCT00537095.

FINDINGS

Between Sept 28, 2007, and Oct 16, 2008, we randomly allocated 72 patients to the vandetanib group and 73 patients to the placebo group. By data cutoff (Dec 2, 2009), 113 (78%) patients had progressed (52 [72%] patients in the vandetanib group and 61 [84%] in the placebo group) and 40 (28%) had died (19 [26%] patients in the vandetanib group and 21 [29%] in the placebo group). Patients who received vandetanib had longer PFS than did those who received placebo (hazard ratio [HR] 0·63, 60% CI 0·54-0·74; one-sided p=0·008): median PFS was 11·1 months (95% CI 7·7-14·0) for patients in the vandetanib group and 5·9 months (4·0-8·9) for patients in the placebo group. The most common grade 3 or worse adverse events were QTc prolongation (ten [14%] of 73 patients in the vandetanib group vs none in the placebo group), diarrhoea (seven [10%] vs none), asthenia (five [7%] vs three [4%]), and fatigue (four [5%] vs none). Two patients in the vandetanib group and one in the placebo group died from treatment-related serious adverse events (haemorrhage from skin metastases and pneumonia in the vandetanib group and pneumonia in the placebo group).

INTERPRETATION

Vandetanib is the first targeted drug to show evidence of efficacy in a randomised phase 2 trial in patients with locally advanced or metastatic differentiated thyroid carcinoma. Further investigation of tyrosine-kinase inhibitors in this setting is warranted.

FUNDING

AstraZeneca.

Emerging role of multikinase inhibitors for refractory thyroid cancer

Thyroid cancer incidence continues to increase, remaining the most common endocrine malignancy. The need for effective systemic therapies combined with high incidence of driver mutations and overexpression of molecular pathways make refractory thyroid cancer an ideal candidate for treatment with novel agents. Multikinase inhibitors have caused a paradigm shift in the treatment of patients with advanced iodine-refractory thyroid cancer. These agents have shown to be the most effective systemic therapy for this disease not only causing prolonged responses but also improving survival. The activity of these agents inhibiting several pathways simultaneously, such as rearranged during transfection protooncogene, mitogen-activated protein kinase, and angiogenesis, can probably explain the effectiveness in controlling the progression of this malignancy. Several of these agents are currently on clinical studies in patients with differentiated and medullary thyroid cancer and most of them are showing promising clinical activity. With the approval of vandetanib for the treatment of medullary thyroid cancer, a new era in the management of this disease has begun. The molecular rationale for the use of these drugs for thyroid cancer is discussed as well as their promising clinical results.

Axitinib and Vismodegib

The complexity of cancer chemotherapy requires pharmacists be familiar with the complicated regimens and highly toxic agents used. This column reviews various issues related to preparation, dispensing, and administration of antineoplastic therapy, and the agents, both commercially available and investigational, used to treat malignant diseases.

Axitinib targeted cancer stemlike cells to enhance efficacy of chemotherapeutic drugs via inhibiting the drug transport function of ABCG2

Stemlike cells have been isolated by their ability to efflux Hoechst 33342 dye and are called the side population (SP). We evaluated the effect of axitinib on targeting cancer stemlike cells and enhancing the efficacy of chemotherapeutical agents. We found that axitinib enhanced the cytotoxicity of topotecan and mitoxantrone in SP cells sorted from human lung cancer A549 cells and increased cell apoptosis induced by chemotherapeutical agents. Moreover, axitinib particularly inhibited the function of adenosine triphosphate (ATP)-binding cassette subfamily G member 2 (ABCG2) and reversed ABCG2-mediated multidrug resistance (MDR) in vitro. However, no significant reversal effect was observed in ABCB1-, ABCC1- or lung resistance-related protein (LRP)-mediated MDR. Furthermore, in both sensitive and MDR cancer cells axitinib neither altered the expression of ABCG2 at the mRNA or protein levels nor blocked the phosphorylation of AKT and extracellular signal-regulated kinase (ERK)1/2. In nude mice bearing ABCG2-overexpressing S1-M1-80 xenografts, axitinib significantly enhanced the antitumor activity of topotecan without causing additional toxicity. Taken together, these data suggest that axitinib particularly targets cancer stemlike cells and reverses ABCG2-mediated drug resistance by inhibiting the transporter activity of ABCG2.

Differentiated thyroid cancers: a comprehensive review of novel targeted therapies

Differentiated thyroid carcinoma (DTC) accounts for more than 90% of new thyroid cancer diagnoses, and includes papillary, follicular and Hürthle cell carcinoma. The prognosis for the vast majority of individuals diagnosed with DTC is excellent, with current treatment that includes surgery, radioactive iodine ablation and postoperative thyroid-stimulating hormone suppression. Unfortunately, the small proportion of individuals who develop radioactive iodine-resistant recurrent disease have few treatment options, and the vast majority will eventually die from their disease. Recently, several novel targets for anticancer agents have been identified and offer new hope for thyroid cancer patients diagnosed with progressive disease. In addition to targeting genes commonly altered in thyroid cancer, which include mutations in BRAF, RAS and RET, proangiogenic growth factor receptors and the sodium-iodide symporter have also been targeted. Several clinical trials evaluating tyrosine kinase and angiogenesis inhibitors for treatment of individuals diagnosed with metastatic or treatment-refractory DTC are currently underway. The objective of this review is to evaluate recent clinical trials that have studied novel targeted drugs for treatment of DTC.

Thyroid cancer: molecular aspects and new therapeutic strategies

Despite that thyroid cancer accounts for over 90% of tumors that arise from the endocrine system, these tumors barely represent 2% of solid tumors in adults. Many entities are grouped under the general term of thyroid cancer, and they differ in histological features as well as molecular and clinical behavior. Thus, the prognosis for patients with thyroid cancer ranges from a survival rate of >97% at 5 years, in the case of differentiated thyroid tumors sensitive to radioactive iodine, to a 4-month median survival for anaplastic tumors. The high vascularity in these tumors and the important role that oncogenic mutations may have in the RAS/RAF/MEK pathway and oncogenicity (as suggested by activating mutations and rearrangements of the RET gene) have led to the development of multitarget inhibitors in different histological subgroups of patients. The correct molecular characterization of patients with thyroid cancer is thought to be a key aspect for the future clinical management of these patients.

SCF(β-TRCP) suppresses angiogenesis and thyroid cancer cell migration by promoting ubiquitination and destruction of VEGF receptor 2

The E3 ubiquitin ligase β-TRCP, acting in concert with casein kinase I, drives ubiquitination and degradation of VEGFR2, and renders human papillary thyroid cancer cells resistant to the VEGFR2 inhibitor sorafenib.

The incidence of human papillary thyroid cancer (PTC) is increasing and an aggressive subtype of this disease is resistant to treatment with vascular endothelial growth factor receptor 2 (VEGFR2) inhibitor. VEGFR2 promotes angiogenesis by triggering endothelial cell proliferation and migration. However, the molecular mechanisms governing VEGFR2 stability in vivo remain unknown. Additionally, whether VEGFR2 influences PTC cell migration is not clear. We show that the ubiquitin E3 ligase SCF^β-TRCP promotes ubiquitination and destruction of VEGFR2 in a casein kinase I (CKI)–dependent manner. β-TRCP knockdown or CKI inhibition causes accumulation of VEGFR2, resulting in increased activity of signaling pathways downstream of VEGFR2. β-TRCP–depleted endothelial cells exhibit enhanced migration and angiogenesis in vitro. Furthermore, β-TRCP knockdown increased angiogenesis and vessel branching in zebrafish. Importantly, we found an inverse correlation between β-TRCP protein levels and angiogenesis in PTC. We also show that β-TRCP inhibits cell migration and decreases sensitivity to the VEGFR2 inhibitor sorafenib in poorly differentiated PTC cells. These results provide a new biomarker that may aid a rational use of tyrosine kinase inhibitors to treat refractory PTC.

Celecoxib, a cyclooxygenase-2 inhibitor, potentiates the chemotherapic effect of vinorelbine in the medullary thyroid cancer TT cell line

We analyzed the in vitro effects of celecoxib, a COX-2 inhibitor, and determined if celecoxib can sensitize a human MTC-derived cell line (TT) to chemotherapeutics. We found that celecoxib induced apoptosis in TT cells and decreased drug efflux by reducing the expression of MDR-1 mRNA, which codes for the drug efflux pump P-gp. We also observed that TT cells were 10-fold more resistant to doxorubicin than to vinorelbine, mimicking what can be observed in clinical practice. In addition, we found that the combination of celecoxib and vinorelbine, but not doxorubicin, induced a significant reduction in cell viability and a significant increase in apoptosis. In conclusion, we showed that celecoxib was able to enhance the chemotherapeutic effect of vinorelbine. A clinical trial exploring the in vivo activities of celecoxib in MTC patients who cannot benefit from available treatments would be desirable, taking into account the possible risks of cardiovascular effects of this drug.

[Current status of therapeutic approaches with targeted therapies in malignant thyroid cancer. Highlights from the 2011 ASCO Congress]

Increasing interest in the treatment of locally advanced and already metastasized thyroid cancer is reflected in the high number of submitted and accepted conference papers at the annual meeting of the American Society of Clinical Oncology (ASCO Congress) 2011. Many patients suffering from differentiated, undifferentiated and medullary thyroid cancer do not respond to established therapeutic procedures, so that new strategies have to be developed. Targeted biological agents are a new and promising therapeutic method that selectively affects complex signaling cascades, especially angiogenesis, of the malignant cells. Clinicians and researchers should understand the potential of these therapeutic strategies and be aware of the typical side effects.

Activation of the Sonic Hedgehog pathway in thyroid neoplasms and its potential role in tumor cell proliferation

The sonic hedgehog (SHH) pathway is activated in several types of malignancy and plays an important role in tumor cell proliferation and tumorigenesis. SHH binding to a 12-pass transmembrane receptor, Patched (PTCH), leads to freeing of Smoothened (SMO) and subsequent activation of GLI transcription factors. In the present study, we analyzed the expression of SHH, PTCH, SMO, and GLI1 in 31 follicular thyroid adenomas (FTA), 8 anaplastic thyroid carcinomas (ATC), and 51 papillary thyroid carcinomas (PTC) by immunohistochemical staining. More than 65% of FTA, PTC, and ATC specimens stained positive for SHH, PTCH, SMO, and GLI. However, the expression of the genes encoding these four molecules did not correlate with any clinicopathologic parameters, including the age, gender, the status of BRAF gene mutation, tumor stage, local invasion, and metastasis. Three thyroid tumor cell lines (KAT-18, WRO82, and SW1736) all expressed the genes encoding these four molecules. 5-Bromo-2-deoxyuridine labeling and MTT cell proliferation assays revealed that cyclopamine (CP), an inhibitor of the SHH pathway, was able to inhibit the proliferation of KAT-18 and WRO82 cells more effectively than SW1736 cells. CP led to the arrest of cell cycle or apoptosis. Knockdown of SHH and GLI expression by miRNA constructs that target SHH or GLI mRNA in KAT-18 and SW1736 cells led to the inhibition of cell proliferation. Our results suggest that the SHH pathway is widely activated in thyroid neoplasms and may have potential as an early marker of thyroid cancer or as a potential therapeutic target for thyroid cancer treatment.

Sorafenib in metastatic thyroid cancer

Although thyroid cancer usually has an excellent prognosis, few therapeutic options are available in the refractory setting. Based on the recent results of phase II studies with tyrosine kinase inhibitors, we designed a retrospective analysis of patients with metastatic thyroid cancer treated with sorafenib in seven Spanish referral centers. Consecutive patients with progressive metastatic thyroid cancer (papillary, follicular, medullary, and anaplastic) not suitable for curative surgery, radioactive-iodine therapy, or radiotherapy were treated with sorafenib 400 mg twice a day. The primary end point was objective response rate (RR). Secondary end points included toxicity, median progression-free survival (mPFS), median overall survival (mOS), and correlation between tumor marker levels (thyroglobulin, calcitonin, and carcinoembryonic antigen) and efficacy. Between June 2006 and January 2010, 34 patients were included in the study. Sixteen patients presented differentiated thyroid carcinomas (DTC) of which seven (21%) were papillary, nine (26%) follicular, 15 (44%) medullary (MTC), and three (9%) were anaplastic (ATC). Eleven (32%) patients achieved partial response and 14 (41%) had stable disease beyond 6 months. Regarding histological subtype, RRs were 47% (seven of 15) for MTC, 19% (three of 16) for DTC, and 33% (one of three) for ATC. With a median follow-up of 11.5 months, mPFS were 13.5, 10.5, and 4.4 months for DTC, MTC, and ATC respectively. Tumor markers were evaluated in 22 patients, and a statistically significant association was observed between RR and decrease in tumor marker levels >50% (P=0.033). In this retrospective trial, sorafenib showed antitumor efficacy in all histological subtypes of thyroid cancer, warranting further development in this setting.

Phase II efficacy and pharmacogenomic study of Selumetinib (AZD6244; ARRY-142886) in iodine-131 refractory papillary thyroid carcinoma with or without follicular elements

PURPOSE

A multicenter, open-label, phase II trial was conducted to evaluate the efficacy, safety, and tolerability of selumetinib in iodine-refractory papillary thyroid cancer (IRPTC).

EXPERIMENTAL DESIGN

Patients with advanced IRPTC with or without follicular elements and documented disease progression within the preceding 12 months were eligible to receive selumetinib at a dose of 100 mg twice daily. The primary endpoint was objective response rate using Response Evaluation Criteria in Solid Tumors. Secondary endpoints were safety, overall survival, and progression-free survival (PFS). Tumor genotype including mutations in BRAF, NRAS, and HRAS was assessed.

RESULTS

Best responses in 32 evaluable patients out of 39 enrolled were 1 partial response (3%), 21 stable disease (54%), and 11 progressive disease (28%). Disease stability maintenance occurred for 16 weeks in 49%, 24 weeks in 36%. Median PFS was 32 weeks. BRAF V600E mutants (12 of 26 evaluated, 46%) had a longer median PFS compared with patients with BRAF wild-type (WT) tumors (33 versus 11 weeks, respectively, HR = 0.6, not significant, P = 0.3). The most common adverse events and grades 3 to 4 toxicities included rash, fatigue, diarrhea, and peripheral edema. Two pulmonary deaths occurred in the study and were judged unlikely to be related to the study drug.

CONCLUSIONS

Selumetinib was well tolerated but the study was negative with regard to the primary outcome. Secondary analyses suggest that future studies of selumetinib and other mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK; MEK) inhibitors in IRPTC should consider BRAF V600E mutation status in the trial design based on differential trends in outcome.

2012 European thyroid association guidelines for metastatic medullary thyroid cancer

Distant metastases are the main cause of death in patients with medullary thyroid cancer (MTC). These 21 recommendations focus on MTC patients with distant metastases and a detailed follow-up protocol of patients with biochemical or imaging evidence of disease, selection criteria for treatment, and treatment modalities, including local and systemic treatments based on the results of recent trials. Asymptomatic patients with low tumor burden and stable disease may benefit from local treatment modalities and can be followed up at regular intervals of time. Imaging is usually performed every 6-12 months, or at longer intervals of time depending on the doubling times of serum calcitonin and carcinoembryonic antigen levels. Patients with symptoms, large tumor burden and progression on imaging should receive systemic treatment. Indeed, major progress has recently been achieved with novel targeted therapies using kinase inhibitors directed against RET and VEGFR, but further research is needed to improve the outcome of these patients.

In search of a real "targeted" therapy for thyroid cancer

Over the past 5 years, patients with progressive radioactive iodine-refractory thyroid cancer have responded to "targeted" multikinase inhibitors, which inhibit angiogenesis and not the tumor cell. Here, selumetinib targets the mitogen-activated protein kinase pathway in papillary thyroid carcinoma and shows limited single-agent activity in the patients with tumors that harbor the (V600E)BRAF mutation.

Approach to and treatment of differentiated thyroid carcinoma

Thyroid cancer is the most common endocrine malignancy, although representing fewer than 1% of all human tumors. Differentiated thyroid carcinoma (DTC) includes the papillary and follicular histotypes and their variants, accounting for more than 90% of all thyroid cancers. Given the changing presentation of DTC in the last years, the aim of DTC management is to ensure the most effective but least invasive treatment, and adequate follow-up for a disease that nowadays is mostly cured just with surgery and is rarely fatal. This review addresses the multiple steps of current management, based on previous assumptions.

Differentiated thyroid cancer: management of patients with radioiodine nonresponsive disease

Differentiated thyroid carcinoma (papillary and follicular) has a favorable prognosis with an 85% 10-year survival. The patients that recur often require surgery and further radioactive iodine to render them disease-free. Five percent of thyroid cancer patients, however, will eventually succumb to their disease. Metastatic thyroid cancer is treated with radioactive iodine if the metastases are radioiodine avid. Cytotoxic chemotherapies for advanced or metastatic noniodine avid thyroid cancers show no prolonged responses and in general have fallen out of favor. Novel targeted therapies have recently been discovered that have given rise to clinical trials for thyroid cancer. Newer aberrations in molecular pathways and oncogenic mutations in thyroid cancer together with the role of angiogenesis in tumor growth have been central to these discoveries. This paper will focus on the management and treatment of metastatic differentiated thyroid cancers that do not take up radioactive iodine.

Antiangiogenic therapy for advanced renal cell carcinoma: management of treatment-related toxicities

Treatment of metastatic renal cell carcinoma (mRCC) has evolved rapidly over the last two decades as major pathways involved in pathogenesis have been elucidated. These include the vascular endothelial growth factor (VEGF) axis and mammalian target of rapamycin (mTOR). Therapies targeting the VEGF pathway include bevacizumab, sorafenib, sunitinib, pazopanib, and axitinib, whereas temsirolimus and everolimus inhibit the mTOR pathway. All of these novel therapies—VEGF and mTOR inhibitors—are associated with a variety of unique toxicities, some of which may necessitate expert medical management, treatment interruption, or dose reduction. Common adverse events with newer drugs include hypertension, skin reactions, gastrointestinal disturbances, thyroid dysfunction, and fatigue. Skilled management of these toxicities is vital to ensure optimal therapeutic dosing and maximize patient outcomes, including improved survival and quality of life. This review describes and compares the toxicity profiles of novel molecularly targeted agents used in the treatment of mRCC and presents guidance on how best to prevent and manage treatment-related toxicities. Particular attention is given to axitinib, the newest agent to enter the armamentarium. Axitinib is a second-generation receptor tyrosine kinase inhibitor with potent VEGF receptor inhibition that provides durable responses and superior progression-free survival in advanced RCC compared with sorafenib.

Anti-tumor activity of motesanib in a medullary thyroid cancer model

BACKGROUND

Medullary thyroid cancer (MTC) is frequently associated with mutations in the tyrosine kinase Ret and with increased expression of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2). Motesanib is an investigational, orally administered small molecule antagonist of VEGFR1, 2, and 3; platelet-derived growth factor receptor (PDGFR); Kit; and possibly Ret.

AIM

The aim of this study was to investigate the effects of motesanib on wildtype and mutant Ret activity in vitro and on tumor xenograft growth in a mouse model of MTC.

METHODS/RESULTS

In cellular phosphorylation assays, motesanib inhibited the activity of wild-type Ret (IC(50)=66 nM), while it had limited activity against mutant Ret C634W (IC(50)=1100 nM) or Ret M918T (IC(50)>2500 nM). In vivo, motesanib significantly inhibited the growth of TT tumor cell xenografts (expressing Ret C634W) and significantly reduced tumor blood vessel area and tumor cell proliferation, compared with control. Treatment with motesanib resulted in substantial inhibition of Ret tyrosine phosphorylation in TT xenografts and, at comparable doses, in equivalent inhibition of VEGFR2 phosphorylation in both TT xenografts and in mouse lung tissue.

CONCLUSIONS

The results of this study demonstrate that motesanib inhibited thyroid tumor xenograft growth predominantly through inhibition of angiogenesis and possibly via a direct inhibition of VEGFR2 and Ret expressed on tumor cells. These data suggest that targeting angiogenesis pathways and specifically the VEGF pathway may represent a novel therapeutic approach in the treatment of MTC.

The Akt inhibitor MK2206 synergizes, but perifosine antagonizes, the BRAF(V600E) inhibitor PLX4032 and the MEK1/2 inhibitor AZD6244 in the inhibition of thyroid cancer cells

PURPOSE

The purpose of the study was to explore optimal combinations of currently actively developed drugs for dually targeting the Ras → Raf → MAPK kinase (MEK) → MAPK/ERK (MAPK) and the phosphatidylinositol 3-kinase/Akt pathways as effective treatments for thyroid cancer.

EXPERIMENTAL DESIGN

We tested the combinations of the Akt inhibitors MK2206 or perifosine with the BRAF(V600E) inhibitor PLX4032 or the MEK1/2 inhibitor AZD6244 in thyroid cancer cells harboring both the BRAF(V600E) and PIK3CA mutations.

RESULTS

We found that MK2206 could potently, when used alone, and synergistically, when combined with either PLX4032 or AZD6244, inhibit thyroid cancer cell growth with all the combination index values lower than 1. Perifosine could potently inhibit thyroid cancer cell growth when used alone, but a strong antagonism occurred between this drug and PLX4032 or AZD6244 in the inhibition of thyroid cancer cell growth with all combination index values higher than 1. Combinations of MK2206 with PLX4032 or AZD6244 dramatically enhanced G1 cell cycle arrest induced by each drug alone. However, G2 cell cycle arrest uniquely induced by perifosine alone and G1 cell cycle arrest induced by PLX4032 or AZD6244 were both reversed by combination treatments, providing a mechanism for their antagonism. All these drugs could correspondingly inhibit the MAPK and phosphatidylinositol 3-kinase/Akt signalings, confirming their expected target effects.

CONCLUSIONS

We demonstrated, unexpectedly, opposite outcomes of MK2206 and perifosine in their combinational treatments with BRAF(V600E)/MEK inhibitors in thyroid cancer cells. The data may help appropriate selection of these prominent drugs for clinical trials of combination therapies for thyroid cancer.

Late intervention with anti-BRAF(V600E) therapy induces tumor regression in an orthotopic mouse model of human anaplastic thyroid cancer

Human anaplastic thyroid cancer (ATC) is a lethal disease with an advanced clinical presentation and median survival of 3 months. The BRAF(V600E) oncoprotein is a potent transforming factor that causes human thyroid cancer cell progression in vitro and in vivo; therefore, we sought to target this oncoprotein in a late intervention model of ATC in vivo. We used the human ATC cell line 8505c, which harbors the BRAF(V600E) and TP53(R248G) mutations. Immunocompromised mice were randomized to receive the selective anti-BRAF(V600E) inhibitor, PLX4720, or vehicle by oral gavage 28 d after tumor implantation, 1 wk before all animals typically die due to widespread metastatic lung disease and neck compressive symptoms in this model. Mice were euthanized weekly to evaluate tumor volume and metastases. Control mice showed progressive tumor growth and lung metastases by 35 d after tumor implantation. At that time, all control mice had large tumors, were cachectic, and were euthanized due to their tumor-related weight loss. PLX4720-treated mice, however, showed a significant decrease in tumor volume and lung metastases in addition to a reversal of tumor-related weight loss. Mouse survival was extended to 49 d in PLX4720-treated animals. PLX4720 treatment inhibited cell cycle progression from 28 d to 49 d in vivo. PLX4720 induces striking tumor regression and reversal of cachexia in an in vivo model of advanced thyroid cancer that harbors the BRAF(V600E) mutation.

Effect of dasatinib against thyroid cancer cell lines in vitro and a xenograft model in vivo

Tyrosine kinase inhibitors (TKIs) have emerged as a promising class of agents against thyroid cancer. The aim of the present study was to investigate the in vitro and in vivo activity of dasatinib against a panel of thyroid cancer cell lines and explore possible mechanisms of action, using various assays and western blotting. Our results showed that dasatinib exhibits prominent cytostatic activity both in vitro and in vivo against thyroid cancer cell lines with RET/PTC rearrangement (BHP2-7) and KRAS mutation (Cal62). Although dasatinib has primarily been described as an ABL/SRCfamily kinase inhibitor, the cytostatic activity observed in the present study is mediated by several off-target effects of dasatinib, some of which have not previously been reported. These effects include a reduction in phospho-FAK, FAK, RAS, Caveolin and SYK protein levels and an increase in β-catenin protein expression, which leads to the induction of senescence, an increase in the adhesiveness of the cells, a decrease in reactive oxygen species level, and changes in the expression profile of molecules involved in cellular adhesion such as integrins. Therefore, we propose that dasatinib is an effective therapeutic agent for certain patients with thyroid cancer, and these candidate patients may be identifiable on the basis of standard genotypic analyses.

New treatment modalities in advanced thyroid cancer

BACKGROUND

Thyroid cancer is a heterogeneous disease that is classified into differentiated thyroid carcinoma (DTC), undifferentiated/anaplastic thyroid carcinoma (ATC) and medullary thyroid carcinoma. Results of conventional treatment modalities in advanced thyroid cancer have been disappointing and therefore, new therapies are needed.

METHODS

We searched PubMed, The Cochrane Library, Medline and EMBASE databases and abstracts published in annual proceedings for new treatment modalities in advanced thyroid cancer. We also searched for ongoing trials in www.clinicaltrials.gov.

RESULTS

Six phase I, 17 phase II and 1 phase III trials with tyrosine kinase inhibitors were carried out. We found 2 pilot studies and 11 phase II trials with redifferentiation therapies, mainly in DTC. For antiproliferative approaches, three phase I and four phase II trials were found. Immunomodulatory gene therapy was tested in a pilot study in ATC patients. Two phase II trials were carried out with immunotherapy. One phase I and nine phase II trials were found with radionucleotide therapy in patients with DTC.

CONCLUSION

The developments in the treatment of advanced thyroid cancer are intriguing. Future trials should aim at combinations of targeted agents with or without other treatment modalities, and will hopefully contribute to further improvement of outcomes.

Kinase inhibitors for advanced medullary thyroid carcinoma

The recent availability of molecular targeted therapies leads to a reconsideration of the treatment strategy for patients with distant metastases from medullary thyroid carcinoma. In patients with progressive disease, treatment with kinase inhibitors should be offered.

Approach to the patient with advanced differentiated thyroid cancer

Patients with advanced thyroid cancer may benefit from l-thyroxine treatment at doses that suppress serum TSH level, local treatment interventions, and radioiodine therapy. In those patients who are refractory to radioiodine therapy and in whom progressive disease has been documented, the efficacy of cytotoxic chemotherapy is poor. Encouraging results have been obtained with the use of kinase inhibitors that should be offered as first-line treatment, preferably in the context of a prospective trial.

Meta-analysis of contribution of genetic polymorphisms in drug-metabolizing enzymes or transporters to axitinib pharmacokinetics

PURPOSE

Axitinib, an orally administered inhibitor of vascular endothelial growth factor 1, 2 and 3, is primarily metabolized by cytochrome P450 (CYP) 3A4/5 but is also a substrate for CYP1A2, CYP2C19, UDP-glucuronosyltransferase (UGT)1A1 and the drug transporters P-glycoprotein (encoded by the ABCB1 gene) and OATP1B1 (encoded by SLC01B1). The potential contribution of polymorphisms in genes encoding these enzymes and transporters to axitinib pharmacokinetic variability was assessed.

METHODS

A fixed effects meta-analysis was performed using data pooled from 11 healthy volunteer clinical pharmacology trials to investigate the potential association between axitinib exposure and major polymorphisms in these genes following a 5-mg dose of axitinib.

RESULTS

Up to 15 variant alleles were evaluated and up to 315 healthy volunteers per polymorphism were assayed. None of the polymorphisms analysed was a statistically significant predictor of axitinib pharmacokinetic variability. Amongst genotypes and inferred phenotypes, CYP2C19 genotype and the ABCB1 (G2677T/A) polymorphism were the closest to statistical significance in influencing axitinib pharmacokinetic variability after multiple-testing adjustment. However, no enzyme or transporter genotype/inferred phenotype contributed >5% to the overall pharmacokinetic variability of axitinib.

CONCLUSIONS

No statistically significant associations between the specific polymorphisms analysed and axitinib plasma exposure were observed, suggesting that genotype- or inferred phenotype-based adjustment of axitinib dose in individual subjects is not warranted.

Clinical utility of vandetanib in the treatment of patients with advanced medullary thyroid cancer

Vandetanib (ZD6474) became the first systemic agent to be approved for the treatment of metastatic or locally advanced medullary thyroid cancer. It was a proof of principle, because it is an orally bioavailable medication that targets the growth factors felt to be important in the pathogenesis of this disease, ie, the rearranged during transfection proto-oncogene and vascular endothelial growth factor receptor. It was tested initially in two Phase II studies at doses of 100 mg and 300 mg daily. Although activity was seen at both doses, the higher dose was chosen for a randomized, placebo-controlled Phase II study. This trial, which accrued more than 300 patients, showed a statistically significant benefit for the group taking vandetanib compared with those taking placebo medication. Progression-free survival for the vandetanib arm has not been reached, compared with 19 months for the placebo arm. The main toxicity appears to be diarrhea, although some patients experienced significant side effects, including torsades de pointes and sudden cardiac death. Therefore, it is now necessary for practitioners to enroll in a Risk Evaluation Mitigation Strategy before being allowed to prescribe this medication, to reduce the risk of serious side effects occurring.

Influence of mild and moderate hepatic impairment on axitinib pharmacokinetics

OBJECTIVE

To evaluate the effects of hepatic impairment on the pharmacokinetics and safety of a single, oral axitinib dose in subjects with mild or moderate hepatic impairment.

METHODS

In this phase I, open-label, parallel-group study, a total of 24 subjects with either normal hepatic function (n = 8) or with mild (n = 8) or moderate (n = 8) hepatic impairment were administered a single, oral dose of axitinib (5 mg). Blood samples were collected at intervals up to 144 h following dosing, and plasma pharmacokinetics and safety were assessed. Changes in axitinib plasma exposures in subjects with mild or moderate hepatic impairment were predicted using computer simulations and used to guide initial dosing in the clinical study.

RESULTS

Axitinib exposure was similar in subjects with normal hepatic function and those with mild hepatic impairment, but approximately twofold higher in subjects with moderate hepatic impairment. Axitinib exposure weakly correlated with measures of hepatic function but was not affected by smoking status. Axitinib protein binding was similar in the three treatment groups. No significant treatment-related adverse events were reported.

CONCLUSIONS

Compared with subjects with normal hepatic function, moderate hepatic impairment increased axitinib exposure, suggesting that the oral clearance of axitinib is altered in these subjects. In addition, these data indicate a possible need for a dose reduction in subjects who develop moderate or worse hepatic impairment during axitinib treatment. A single 5-mg dose of axitinib was well tolerated in subjects with mild or moderate hepatic impairment.

[Refractory thyroid cancers]

Refractory thyroid cancers include medullary and differentiated cancers with locally advanced disease that is not amenable to surgery or with distant metastases, differentiated thyroid carcinomas being refractory to radio-iodine treatment and all anaplastic carcinomas. These carcinomas are rare, with an estimated incidence in France of 350 new cases per year. Their management may benefit from the TUTHYREF network. Kinase inhibitors inhibit kinases of the VEGF receptors, and this inhibits angiogenesis, and some of these agents also inhibit other kinases of the MAPkinase pathway. These inhibitors are effective in differentiated and medullary thyroid cancers, and induce a partial response or a long-term stabilisation in more than half of patients. Their toxicity is significant and these treatments should be given only to selected patients with locally advanced or metastatic disease, with progression or with clinical symptoms.

Thyroid cancer: emerging role for targeted therapies

The histology and clinical behavior of thyroid cancer are highly diverse. Although most are indolent tumors with a very favorable outcome with the current standard of care therapy, a small subset of tumors may be among the most lethal malignancies known to man. While surgery and radioactive iodine are the standard of care for differentiated thyroid cancers (DTC) and are effective in curing a majority of such patients, those with iodine-resistant cancers pose a great challenge for clinicians, as these patients have limited treatment options and poor prognoses. Medullary thyroid carcinoma (MTC) has no effective systemic therapy despite the genetic and signaling defects that have been well characterized for the last two decades. Anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors that remains fatal despite conventional multimodality therapy. Increased understanding of the pathogenesis of papillary thyroid carcinoma, the most common type of DTC, as well as ATC, has led to the development of targeted therapies aimed at signaling pathways and angiogenesis that are critical to the development and/or progression of such tumors. Development of tyrosine kinase inhibitors targeting known pathogenetic defects in MTC has led to testing of such agents in the clinic. Numerous clinical trials have been conducted over the last 5 years to examine the effects of these targeted molecular therapies on the outcomes of patients with iodine-refractory DTC, MTC and ATC. Conduction of such trials in the last few years represents a major breakthrough in the field of thyroid cancer. Several trials testing targeted therapies offer promise for setting new standards for the future of patients with progressive thyroid cancer. The purpose of this paper is to outline the recent advances in understanding of the pathogenesis of thyroid cancer and to summarize the results of the clinical trials with these targeted therapies.

Vandetanib in patients with locally advanced or metastatic medullary thyroid cancer: a randomized, double-blind phase III trial

PURPOSE

There is no effective therapy for patients with advanced medullary thyroid carcinoma (MTC). Vandetanib, a once-daily oral inhibitor of RET kinase, vascular endothelial growth factor receptor, and epidermal growth factor receptor signaling, has previously shown antitumor activity in a phase II study of patients with advanced hereditary MTC.

PATIENTS AND METHODS

Patients with advanced MTC were randomly assigned in a 2:1 ratio to receive vandetanib 300 mg/d or placebo. On objective disease progression, patients could elect to receive open-label vandetanib. The primary end point was progression-free survival (PFS), determined by independent central Response Evaluation Criteria in Solid Tumors (RECIST) assessments.

RESULTS

Between December 2006 and November 2007, 331 patients (mean age, 52 years; 90% sporadic; 95% metastatic) were randomly assigned to receive vandetanib (231) or placebo (100). At data cutoff (July 2009; median follow-up, 24 months), 37% of patients had progressed and 15% had died. The study met its primary objective of PFS prolongation with vandetanib versus placebo (hazard ratio [HR], 0.46; 95% CI, 0.31 to 0.69; P < .001). Statistically significant advantages for vandetanib were also seen for objective response rate (P < .001), disease control rate (P = .001), and biochemical response (P < .001). Overall survival data were immature at data cutoff (HR, 0.89; 95% CI, 0.48 to 1.65). A final survival analysis will take place when 50% of the patients have died. Common adverse events (any grade) occurred more frequently with vandetanib compared with placebo, including diarrhea (56% v 26%), rash (45% v 11%), nausea (33% v 16%), hypertension (32% v 5%), and headache (26% v 9%).

CONCLUSION

Vandetanib demonstrated therapeutic efficacy in a phase III trial of patients with advanced MTC (ClinicalTrials.gov NCT00410761).

Multicenter, phase II study of axitinib, a selective second-generation inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, in patients with metastatic melanoma

PURPOSE

This multicenter, open-label, phase II study evaluated the safety and clinical activity of axitinib, a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors (VEGFR)-1, 2, and 3, in patients with metastatic melanoma.

EXPERIMENTAL DESIGN

Thirty-two patients with a maximum of one prior systemic therapy received axitinib at a starting dose of 5 mg twice daily. The primary endpoint was objective response rate.

RESULTS

Objective response rate was 18.8% [95% confidence interval (CI), 7.2-36.4], comprising one complete and five partial responses with a median response duration of 5.9 months (95% CI, 5.0-17.0). Stable disease at 16 weeks was noted in six patients (18.8%), with an overall clinical benefit rate of 37.5%. Six-month progression-free survival rate was 33.9%, 1-year overall survival rate was 28.1%, and median overall survival was 6.6 months (95% CI, 5.2-9.0). The most frequently (>15%) reported nonhematologic, treatment-related adverse events were fatigue, hypertension, hoarseness, and diarrhea. Treatment-related fatal bowel perforation, a known class effect, occurred in one patient. Axitinib selectively decreased plasma concentrations of soluble VEGFR (sVEGFR)-2 and sVEGFR-3 compared with soluble stem cell factor receptor (sKIT). No significant association was noted between plasma levels of axitinib and response. However, post hoc analyses indicated potential relationships between efficacy endpoints and diastolic blood pressure of 90 mm Hg or higher as well as baseline serum lactate dehydrogenase levels.

CONCLUSIONS

Axitinib was well tolerated, showed a selective VEGFR-inhibitory profile, and showed single-agent activity in metastatic melanoma. Further evaluations of axitinib, alone and combined with chemotherapy, are ongoing.

Thyroid cancer: pathogenesis and targeted therapy

Therapeutic options for advanced, unresectable radioiodine-resistant thyroid cancers have historically been limited. Recent progress in understanding the pathogenesis of the various subtypes of thyroid cancer has led to increased interest in the development of targeted therapies, with potential strategies including angiogenesis inhibition, inhibition of aberrant intracellular signaling in the MAPK and PI3K/AKT/mTOR pathways, radioimmunotherapy, and redifferentiation agents. On the basis of a recent positive phase III clinical trial, the RET, vascular endothelial growth factor receptor (VEGFR), and epidermal growth factor receptor (EGFR) inhibitor vandetanib has received FDA approval as of April 2011 for use in the treatment of advanced medullary thyroid cancer. Several other recent phase II clinical trials in advanced thyroid cancer have demonstrated significant activity, and multiple other promising therapeutic strategies are in earlier phases of clinical development. The recent progress in targeted therapy is already revolutionizing management paradigms for advanced thyroid cancer, and will likely continue to dramatically expand treatment options in the coming years.

Emerging therapeutics for advanced thyroid malignancies: rationale and targeted approaches

INTRODUCTION

Thyroid cancer is an emerging public health concern. In the USA, its incidence has doubled in the past decade, making it the eighth most commonly diagnosed neoplasm in 2010. Despite this alarming increase, most thyroid cancer patients benefit from conventional approaches (surgery, radioiodine, radiotherapy, TSH suppression with levothyroxine) and are often cured. Nevertheless, a minority have aggressive tumors resistant to cytotoxic and other historical therapies; these patients sorely need new treatment options.

AREAS COVERED

Herein the biology and molecular characteristics of the common histological types of thyroid cancer are reviewed to provide context for subsequent discussion of recent developments and emerging therapeutics for advanced thyroid cancers.

EXPERT OPINION

Several kinase inhibitors, especially those targeting VEGFR and/or RET, have already demonstrated promising activity in differentiated and medullary thyroid cancers (DTC, MTC). Although of minimal benefit in DTC and MTC, cytotoxic chemotherapy with anti-microtubule agents and/or anthracyclines in combination with intensity-modulated radiation therapy appears to extend survival for patients with locoregionally confined anaplastic thyroid cancer (ATC), but to have only modest benefit in metastatic ATC. Further discovery and development of novel agents and combinations of agents will be critical to further progress in treating advanced thyroid cancers of all histotypes.

Alternative medical treatment for radioiodine-refractory thyroid cancers

Thyroid cancer is one of the most rapidly increasing cancers in many countries. Although most thyroid cancers are differentiated cancers and easily treated with radioiodine (RI), a portion of differentiated and undifferentiated cancers is refractory not only to RI therapy, but also to radiotherapy and chemotherapy. Thus, various alternative therapies have been tested in RI-refractory thyroid cancers. These alternative therapies include two major categories: redifferentiation therapy and recent molecular target therapy. Several clinical trials have investigated these therapies. They demonstrated potential effects of the therapies, although the results have been somewhat limited so far. Thus, the future strategy for undifferentiated thyroid cancers will involve individualized, lesion-specific, and combined therapy. In this review, the basic mechanism of each redifferentiation and molecular target therapy is discussed, and results of recent clinical trials using these therapeutic agents are summarized.

Key predictive factors of axitinib (AG-013736)-induced proteinuria and efficacy: a phase II study in Japanese patients with cytokine-refractory metastatic renal cell Carcinoma

BACKGROUND

Axitinib (AG-013736) is an oral, selective and potent inhibitor of vascular endothelial growth factor receptors (VEGFR)-1, 2 and 3. This phase II study investigated axitinib efficacy, safety and biomarkers in Japanese patients with cytokine-refractory metastatic renal cell carcinoma (mRCC).

PATIENTS AND METHODS

In an open-label, multicentre study, 64 patients received an axitinib starting dose of 5mg twice daily.

RESULTS

Objective response rate (ORR) was 50.0% and median progression-free survival (PFS) was 11.0 months per independent review committee. Common treatment-related adverse events were hypertension (84%; 70% grade ≥3), hand-foot syndrome (75%; 22% grade ≥3) and diarrhoea (64%; 5% grade ≥3). Eighteen patients (28%) developed proteinuria ≥2g/24h and required dose reduction or treatment interruption/discontinuation. Proteinuria was a major cause for treatment discontinuation. Baseline urine protein levels were associated with development of proteinuria ≥2g/24h (hazard ratio [HR]=5.457, P=0.0035 in patients with baseline proteinuria ≥1+ versus <1+). Baseline urine protein levels correlated more strongly with axitinib-related proteinuria than other baseline renal function test values or blood pressure. Patients with greater decreases in soluble VEGFR-2 concentrations had significantly higher ORR and longer PFS than those with smaller decreases (ORR: 64.5% versus 37.5%, P=0.045; median PFS: 12.9 months versus 9.2 months, HR=0.42, P=0.01).

CONCLUSIONS

Axitinib showed significant antitumour activity and was well tolerated in Japanese mRCC patients. Baseline proteinuria and soluble VEGFR-2 levels may be key indicators of axitinib-induced proteinuria and efficacy, respectively.

Multikinase inhibitors: a new option for the treatment of thyroid cancer

Thyroid cancer typically has a good outcome following standard treatments, which include surgery, radioactive iodine ablation and treatment with TSH-suppressive levothyroxine. Thyroid cancers that persist or recur following these therapies have a poorer prognosis. Activation of mitogenic and angiogenic signaling pathways occurs in these cancers, and preclinical models have shown that inhibition of key kinase steps in these pathways can have antitumoral effects. Several of these kinase inhibitors have now been tested in phase II and phase III trials, with modestly encouraging results. Some promising data exist for the use of vandetanib (also known as ZD6474), motesanib, axitinib, cabozantinib (also known as XL184), sorafenib, sunitinib, pazopanib and lenvatinib (also known as E7080) in progressive thyroid cancer of medullary, papillary and follicular subtypes. These drugs are generally well-tolerated, although dose-limiting toxicities are common, and a few (probable) treatment-related deaths have been reported. Additional phase III trials will be needed to conclusively show that treatment benefit exceeds risk. Drug resistance can occur via activation of alternate mitogenic signals (pathway switching), as has been reported for the use of kinase inhibitors in other malignancies, such as melanoma. The hypothesis that combinations of kinase inhibitors targeting different pathways might produce better results is currently being tested in several clinical trials.

Targeted treatment of differentiated and medullary thyroid cancer

The incidence of thyroid cancer is increasing, with a concomitant increase in the number of patients with advanced and metastatic disease. Discoveries regarding the pathogenesis of thyroid cancer have led to the recent development of new therapeutic agents that are beginning to appear on the market. Many of these new agents are targeted kinase inhibitors primarily affecting oncogenic kinases (BRAF V600E, RET/PTC) or signaling kinases (VEGFR, PDGFR). Some of these agents report significant partial response rates, while others attain stabilization of disease as their best response. Their impact on survival is unclear. While these agents target similar pathways, a wide variety of differences exist regarding efficacy and side effect profile. Current expert opinion advises that these agents be used only in a specific subset of patients.