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

An Investigation in the Comparability of the Exposure and Recommended Dose of Selected Pfizer Drugs in East Asian Countries: Is Mutual Usage of Clinical Data Among East Asian Countries Feasible?

The current regulatory path for new drug registration in East Asian countries has led to significant delay of the new medicines in these countries. A unified regulatory path and allowance of mutual usage of clinical data in East Asian countries would lead to cost saving in drug development and expedite the new drug registration in these countries. The objectives of the present analysis are to compare the approval dates of a selection of products developed by Pfizer in the United States and East Asian countries (China, Japan, Korea) and compare the pharmacokinetics and recommended doses of these products in East Asian countries. Eighteen products (20 drugs, 2 products with 2 combination drugs) with exposure data available in at least 2 of the 3 East Asian countries across different therapeutic areas were included in the analyses. The results showed that most products had delayed approval in East Asian countries (up to 8 years) after US or EU approval. No distinct differences were observed in the drug exposure and recommended doses for the selected products in East Asian countries. These results together with literature data of genetic similarity of the East Asian populations support the mutual usage of the clinical data in the East Asian countries for expedited regulatory submission and approval.

Influence of two anti-tumor drugs, pazopanib, and axitinib, on the development and thyroid-axis of zebrafish (Danio rerio) embryos/larvae

Introduction

In recent years, the potential toxicities of different pharmaceuticals toward the thyroid system have received increasing attention. In this study, we aim to evaluate the toxic effects of pazopanib and axitinib, two anti-tumor drugs with widespread clinical use, on thyroid function in the zebrafish model.

Methods

We measured levels of thyroid-related hormones using the commercial Enzyme-Linked Immunosorbent Assay (ELISA) kit. Whole-mount in situ hybridization (WISH) analysis was employed to detect target gene expression changes. Morphology of the thyroid were evaluated by using transgenic Tg (tg: EGFP) fish line under a confocal microscope. The relative mRNA expression of key genes was verified through quantitative real-time polymerase chain reaction (RT‒qPCR). The size and number of the follicles was quantified whereby Hematoxylin-Eosin (H & E) staining under a light microscope.

Results

The results revealed that fertilized zebrafish embryos were incubated in pazopanib or axitinib for 96 hours, development and survival were significantly affected, which was accompanied by significant disturbances in thyroid endocrine system (e.g., increased thyroid-stimulating hormone (TSH) content and decreased triiodothyronine (T3) and thyroxine (T4) content, as well as transcription changes of genes associated with the hypothalamus-pituitary-thyroid (HPT) axis. Moreover, based on whole-mount in situ hybridization staining of tg and histopathological examination of zebrafish embryos treated with pazopanib and axitinib, we observed a significantly abnormal development of thyroid follicles in the Tg (tg: EGFP) zebrafish transgenic line.

Conclusion

Collectively, these findings indicate that pazopanib and axitinib may have toxic effects on thyroid development and function, at least partially, by influencing the regulation of the HPT axis. Thus, we believe that the potential thyroid toxicities of pazopanib and axitinib in their clinical applications should receive greater attention.

Autoimmune Myasthenia, Primary Adrenal Insufficiency, and Progressive Hypothyroidism Due to Pembrolizumab and Axitinib Combination Regimen

Immune checkpoint inhibitors (ICI) and tyrosine kinase inhibitors (TKI) have been among the increasingly used antineoplastic agents for advanced cancers including renal cell carcinoma (RCC). Although these antineoplastic agents have broad range of efficacy, rare adverse events - mild and fatal, acute and chronic, immune and non-immune mediated - have been reported. We report a case of a 73-year-old Caucasian male patient with stage IV right-sided clear cell RCC who was treated with a pembrolizumab-axitinib combination regimen and suffered life-threatening, acute onset immune-related myasthenia gravis (MG), subsequently progressive hypothyroidism, and primary adrenal insufficiency.

Fatigue and its management in cancer patients undergoing VEGFR-TKI therapy

INTRODUCTION

Fatigue is the most common side effect of cancer and cancer treatment and is often called cancer fatigue or cancer-related fatigue. For cancer patients, cancer-related fatigue has a negative impact on participation in work and social activities, mood, and daily activities, significantly impairing quality of life. Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) sometimes cause fatigue, and early detection and appropriate management of fatigue in cancer patients treated with a VEGFR-TKI prevent fatigue from becoming more severe, thus maximizing the benefits of the treatment.

AREAS COVERED

This paper focuses on fatigue and discusses its frequency, assessment, risk factors, and management methods.

EXPERT OPINION

The drugs currently available for treating cancer-related fatigue are not effective enough, and their mechanisms of action are not fully understood. Some agents have demonstrated efficacy as treatments for fatigue due to pharmacotherapy, and further elucidation of their mechanisms is expected, together with the development of new drugs. Since fatigue has a range of causes, its treatment requires not only medication, but also exercise, nutrition, and other therapeutic approaches. The successful treatment of fatigue will therefore need multidisciplinary therapy involving the establishment of systems of cooperation across various specialties.

Long-term disease control of metastatic type 2 papillary renal cell carcinoma using local treatment and molecular targeted therapy: A case report

A 46-year-old man underwent right partial nephrectomy for type 2 papillary renal cell carcinoma (PRCC) in 2011. Lung metastasis and lymph node (LN) metastases around the inferior vena cave appeared in 2012. A right radical nephrectomy and extensive LN dissection was performed and the resection of lung metastasis was performed one month after the nephrectomy. Mediastinal LN metastases occurred in 2013, and resection of the affected LNs was performed. Sunitinib and zoledronic acid was started in 2014 because mediastinal LN swelling and multiple bone metastases appeared. Sunitinib treatment was stopped soon after due to adverse events and axitinib treatment was started. Axitinib was effective and the patient had stable disease for 30 months. Adverse events were successfully controlled by dose reduction and periodic drug withdrawal schedules (for example, 5 days on, 2 days off). Axitinib was further continued for 19 months as the metastatic lesions had progressed slowly. Temsirolimus treatment was started in 2019, but it was stopped after three cycles due to interstitial pneumonia. The patient died 80 months after the initial recurrence. Using multidisciplinary treatment, durable disease control was achieved in a patient with metastatic type 2 PRCC.

Absorption of the orally active multikinase inhibitor axitinib as a therapeutic index to guide dose titration in metastatic renal cell carcinoma

Purpose Axitinib is an orally active multikinase inhibitor currently used to treat patients with metastatic renal cell carcinoma (RCC). This study examined the pharmacokinetics of axitinib and the relationship between peak drug concentration (C_max) and clinical outcomes in real-world practice. Methods Twenty patients with metastatic RCC treated with axitinib monotherapy were enrolled. Post-dose (1-4 h) blood samples were obtained, and axitinib C_max in plasma was measured by liquid chromatography-tandem mass spectrometry. Efficacy endpoints were best overall response (per RECIST 1.1) and progression-free survival (PFS). The safety endpoint was the cumulative incidence of dose-limiting toxicities (DLTs). Results Large inter- and intra-individual variability in dose-adjusted C_max was observed (0.02-11.2 ng/mL/mg). Axitinib absorption was significantly influenced by glucuronidation activity (P = 0.040). C_max at steady state was significantly higher in responders than in non-responders (P = 0.013). The optimal C_max cutoff to predict a clinical response was 12.4 ng/mL. The median PFS was significantly longer in patients who achieved an average steady state C_max above the threshold than in those who did not (799 vs. 336 days; P = 0.047). The cumulative incidence of DLTs was significantly higher in patients with C_max ≥ 40.2 ng/mL than in other patients (sub-hazard ratio, 4.13; 95% confidence interval, 1.27-13.5; P = 0.019). Conclusions The potential therapeutic window of axitinib C_max in metastatic RCC was estimated at 12.4-40.2 ng/mL. Pharmacokinetically guided dose titration using therapeutic drug monitoring may improve the efficacy and safety of axitinib, warranting further investigation in a larger patient population.

Optimizing treatment of renal cell carcinoma with VEGFR-TKIs: a comparison of clinical pharmacology and drug-drug interactions of anti-angiogenic drugs

Anti-angiogenic treatment is an important option that has changed the therapeutic landscape in various tumors, particularly in patients affected by renal cell carcinoma (RCC). Agents that block signaling pathways governing tumor angiogenesis have raised high expectations among clinicians. Vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs) comprise a heterogeneous class of drugs with distinct pharmacological profiles, including potency, selectivity, pharmacokinetics and drug-drug interactions. Among them, tivozanib is one of the last TKIs introduced in the clinical practice; this drug selectively targets VEGFRs, it is characterized by a favorable pharmacokinetics and safety profile and has been approved as first-line treatment for patients with metastatic RCC (mRCC). In this article, we describe the clinical pharmacology of selected VEGFR-TKIs used for the treatment of mRCC, highlighting the relevant differences; moreover we aim to define the main pharmacologic characteristics of these drug.

Tyrosine kinase inhibitors and immune checkpoint inhibitors-induced thyroid disorders

Recently, tyrosine kinase inhibitors (TKI) and immune checkpoint inhibitors (ICPIs) have emerged as new classes of anticancer therapies. Although generally considered less toxic than cytotoxic chemotherapy, these new drugs can cause significant unanticipated side effects including thyroid dysfunction. This review provides a literature assessment of thyroid dysfunctions induced by TKI and ICPIs. We intend to define for these two classes the frequency of thyroid involvement, the potential mechanisms that result in this toxicity, the clinical-biological impact and the therapeutic management. Detection of thyroid dysfunction requires monitoring of TSH, in combination with free T4 if needed and, depending on the clinical impact and the kinetics of biological abnormalities, starting symptomatic treatment of hyperthyroidism and/or correcting hypothyroidism.

Axitinib in the treatment of renal cell carcinoma: design, development, and place in therapy

Since 2005, the approved first-line treatment of metastatic renal cell carcinoma consists in tyrosine kinase inhibitors (TKIs) targeting the vascular endothelial growth factor receptors (VEGFRs). Axitinib is an oral second-generation TKI and a potent VEGFR inhibitor with a half maximal inhibitory concentration for the VEGF family receptors 10-fold lower than other TKIs. Axitinib activity in renal cell carcinoma (RCC) patients has been studied in various settings and particularly as second-line treatment. In this setting, axitinib with clinically based dose escalation compared to sorafenib has demonstrated an improvement in progression-free survival in a randomized Phase III trial leading to US Food and Drug Administration approval. In the first-line setting, axitinib failed to demonstrate improved efficacy over sorafenib, but the field of RCC treatment is rapidly changing with novel TKIs as cabozantinib or the emergence of check point inhibitors as nivolumab and the place of axitinib in therapy is therefore challenged. In this review, we focus on axitinib pharmacological and clinical properties in RCC patients and discuss its place in the treatment of patients with RCC.

Key predictive factors for efficacy of axitinib in first-line metastatic renal cell carcinoma: subgroup analysis in Japanese patients from a randomized, double-blind phase II study

OBJECTIVES

To conduct Japanese subgroup analyses of a randomized, global Phase II study of axitinib with and without dose titration in first-line metastatic renal cell carcinoma and to explore predictive factors for axitinib efficacy in first-line metastatic renal cell carcinoma.

METHODS

The data included 44 Japanese and 169 non-Japanese treatment-naïve patients with metastatic renal cell carcinoma. Patients received twice-daily axitinib 5 mg during a 4-week lead-in period. Patients who met the pre-defined randomization criteria were stratified by Eastern Cooperative Oncology Group performance status and randomly assigned (1:1) to axitinib or placebo titration. The primary endpoint was objective response rate; secondary endpoints included progression-free survival and safety. Predictive factors were analyzed using data from all patients.

RESULTS

The objective response rate (95% confidence interval) was 66% (50-80%) vs. 44% (36-52%) in Japanese and non-Japanese patients, respectively. At the primary analysis, median progression-free survival could not be estimated for Japanese patients, and was 27.6 months (95% confidence interval: 16.6-33.2) in an updated analysis. Hypertension, diarrhea, hand-foot syndrome, dysphonia, hypothyroidism and proteinuria were common adverse events in Japanese patients. Due to a small number of randomized patients, effects of axitinib dose titration could not sufficiently be confirmed among Japanese patients. The multivariate analysis identified time from histopathological diagnosis to treatment and sum of the longest diameter for target lesion at baseline as independent predictive factors for progression-free survival.

CONCLUSIONS

Axitinib is effective and well tolerated as first-line metastatic renal cell carcinoma therapy in Japanese patients. Predictive factors for axitinib efficacy endpoints identified in this setting warrant further investigation.

Axitinib: a review in advanced renal cell carcinoma

Axitinib (Inlyta(®)) is a potent, selective inhibitor of vascular endothelial growth factor receptor-1, -2 and -3. This article reviews the clinical efficacy and tolerability of axitinib in patients with previously-treated advanced renal cell carcinoma (RCC), as well as summarizing its pharmacological properties. Axitinib was effective in the second-line treatment of advanced RCC, according to the results of the pivotal, phase III AXIS trial. Median progression-free survival (PFS) was significantly prolonged with axitinib versus sorafenib (primary endpoint; independent review committee assessment); this PFS benefit was seen in patients who had received prior treatment with cytokines or sunitinib. The objective response rate was also significantly higher with axitinib than with sorafenib, with no significant between-group difference in median overall survival. Axitinib had a manageable tolerability profile in the AXIS trial, with the most commonly reported treatment-related adverse events including diarrhoea, hypertension, fatigue, decreased appetite, nausea, dysphonia, hand-foot syndrome and hypothyroidism. In conclusion, axitinib is an important option in previously-treated patients with advanced RCC.

Axitinib for the treatment of metastatic renal cell carcinoma

Renal cell carcinoma is a cancer that results from a genetic inactivation of the VHL tumor suppressor gene leading to an upregulation of VEGF. Targeted therapies against VEGF receptors have piqued substantial interest among clinicians and researchers, and these drugs are now the standard of care in the treatment of advanced renal cell carcinoma. One of these VEGF receptor inhibitors, axitinib, has been shown to be a superior second-line therapy when compared with sorafenib. Although axitinib has clinical activity and a manageable safety profile in patients with treatment-naive metastatic renal cell carcinoma, utility in the front-line setting is area of ongoing investigation. Another area of ongoing research is dose titration of axitinib to achieve the maximum clinical benefit. Interestingly, the axitinib-related side effect of hypertension has shown to be associated with more favorable clinical outcomes. This article describes the development of axitinib and discusses the current indications for clinical use in the management of metastatic renal cell carcinoma.

Ongoing Screening and Treatment to Potentially Reduce Tyrosine Kinase Inhibitor-Related Fatigue in Renal Cell Carcinoma

CONTEXT

Renal cell carcinoma (RCC) represents 1% to 4% of adult malignancies, and approximately 33% of patients with RCC present with metastatic disease and have a poor prognosis. Better understanding of RCC tumor biology has led to the development of several molecularly targeted agents, such as tyrosine kinase inhibitors (TKIs), to manage advanced disease. Although evolving data suggest these drugs may be beneficial in RCC, they are associated with significant toxicities. Cancer-related fatigue (CRF) is one of the most common toxicities associated with the TKIs used in RCC.

OBJECTIVES

To review the incidence, pathophysiology, and management of CRF in patients with RCC who are undergoing targeted therapy with TKIs.

METHODS

A comprehensive database search was performed using PubMed, Ovid, Embase, and MEDLINE. References of all cited articles also were reviewed. Data from articles published between 1975 and June 2014 were considered. A narrative review regarding the incidence, pathophysiology, and management of CRF in patients with RCC undergoing targeted therapy with TKIs was performed.

RESULTS

CRF is one of the most common TKI toxicities in patients with metastatic RCC and often is the dose-limiting toxicity. Management of TKI-related CRF can be difficult and may necessitate various nonpharmacologic and pharmacologic interventions.

CONCLUSION

TKI-related CRF in patients with RCC is a highly distressing complication of cancer therapy. CRF can substantially influence drug compliance, the ability to maximally treat, and quality of life. It is important to recognize this common, yet frequently underdiagnosed complication and initiate appropriate management strategies, to increase the likelihood for optimal outcomes.

Axitinib versus sorafenib as a second-line therapy in Asian patients with metastatic renal cell carcinoma: results from a randomized registrational study

Background

This registrational trial evaluated the efficacy, safety, and patient-reported outcomes of axitinib versus sorafenib as a second-line treatment in Asian patients with clear-cell metastatic renal cell carcinoma (mRCC).

Methods

In this open-label, multicenter study, previously treated Asian patients with clear-cell mRCC were stratified by Eastern Cooperative Oncology Group performance status and prior therapy and randomized in a 2:1 ratio to receive axitinib (5 mg twice daily) or sorafenib (400 mg twice daily). The primary end point was progression-free survival (PFS) assessed by a masked independent review committee.

Results

A total of 204 Asian patients received axitinib (n=135) or sorafenib (n=69). Median PFS (95% confidence interval [CI]) was 6.5 (4.7–9.1) months with axitinib versus 4.8 (3.0–6.5) months with sorafenib (hazard ratio, 0.731; 95% CI, 0.506–1.058; one-sided P=0.0531). The objective response rate (95% CI) was 23.7% (16.8%–31.8%) with axitinib versus 10.1% (4.2%–19.8%) with sorafenib. Common, grade ≥3, all-causality adverse events were hypertension (19.3%), weight decrease (5.2%), and proteinuria (5.2%) with axitinib and hypertension (8.7%) and palmar-plantar erythrodysesthesia (7.2%) with sorafenib. In a time-to-deterioration composite end point of death, progression, and worsening of Functional Assessment of Cancer Therapy Kidney Symptom Index score, patients treated with axitinib demonstrated a 17%–24% risk reduction compared with sorafenib-treated patients.

Conclusion

Axitinib is clinically active and well tolerated in previously treated Asian patients with mRCC, consistent with the results from the global Phase III trial. These results establish axitinib as a second-line treatment option for Asian patients with mRCC.

Evaluating the safety and efficacy of axitinib in the treatment of advanced renal cell carcinoma

Axitinib is a tyrosine kinase inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor-α, and c-kit. Phase I studies demonstrated 5 mg twice daily as the recommended starting dose with notable effects seen in renal cell carcinoma, an observation confirmed in Phase II trials. The trial of comparative effectivess of axitinib versus sorafenib in advanced renal cell carcinoma (AXIS) was an international randomized Phase III study designed for registration purposes, compared axitinib to sunitinib. This trial randomized 723 patients with metastatic kidney cancer to axitinib or sunitinib in the second-line setting and demonstrated a median progression-free survival of 6.7 months for axitinib versus 4.7 months for sorafenib (P<0.0001). Clinical benefit was detected regardless of prior therapy, but no overall survival benefit has been observed. Axitinib is well tolerated without a significant effect on quality of life. The most common grade 3 toxicities are hypertension (16%), diarrhea (11%), and fatigue (11%), with other notable side effects being anorexia, nausea, hand–foot syndrome, and rash. Patients who developed diastolic blood pressure >90 mmHg were noted to have significantly longer median overall survival and overall response rates when compared to normotensive patients. Therefore, the manufacturer recommends escalating the twice-daily dose to 7 mg and 10 mg, as tolerated, if there is no significant increase in blood pressure on treatment. Currently, axitinib is approved for use in the second-line setting for patients with metastatic renal cell carcinoma. Research is ongoing in other disease settings.

Axitinib plasma pharmacokinetics and ethnic differences

Axitinib, a potent and selective tyrosine kinase inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, showed improved progression-free survival over sorafenib in patients previously treated for advanced renal cell carcinoma in the AXIS trial. Although a few studies had established the efficacy and safety of axitinib in Asian patients, additional evaluation was necessary to obtain regulatory approval in several Asian countries, especially in light of ethnic differences that are known to exist in genetic polymorphisms for metabolizing enzymes such as cytochrome P450 (CYP) 3A5, CYP2C19 and uridine diphosphate glucuronosyltransferase (UGT) 1A1, which are involved in axitinib metabolism. Axitinib plasma pharmacokinetics following single or multiple administration of oral axitinib in Asian (Japanese or Chinese) healthy subjects as well as Asian patients with advanced solid tumors was compared with that obtained in Caucasians. Upon review, the data demonstrated that axitinib can be characterized as not sensitive to ethnic factors based on its pharmacokinetic and pharmacodynamic properties. Axitinib exhibited similar pharmacokinetics in Asian and non-Asian subjects. A pooled population pharmacokinetic analysis indicated lack of a clinically meaningful effect of ethnicity on axitinib disposition. Therefore, dose adjustment for axitinib on the basis of ethnicity is not currently warranted.

Overall survival and final efficacy and safety results from a Japanese phase II study of axitinib in cytokine-refractory metastatic renal cell carcinoma

In an open-label, multicenter phase II study of Japanese patients with cytokine-refractory metastatic renal cell carcinoma, axitinib showed substantial antitumor activity with an acceptable safety profile. Here, we report overall survival and updated efficacy and safety results. Sixty-four Japanese patients with metastatic renal cell carcinoma following prior therapy with cytokines were treated with axitinib at a starting dose of 5 mg b.i.d. Following median treatment duration of 14.2 months, median overall survival was 37.3 months (95% CI, 28.6-49.9). The objective response rate, the primary endpoint of the study, was 51.6% (95% CI, 38.7-64.2); the median duration of response, 11.1 months (95% CI, 8.2-13.7); and the median progression-free survival was 11.0 months (95% CI, 9.2-12.0), assessed by the independent review committee. Common treatment-related all-grade adverse events were hypertension (88%), hand-foot syndrome (75%), diarrhea (66%), proteinuria (63%), fatigue (55%) and dysphonia (53%). In an exploratory analysis, median overall survival was found to be significantly longer in patients who had greater decreases in plasma levels of soluble vascular endothelial growth factor receptor-2 during the first cycle of treatment. In conclusion, the present study showed axitinib to be effective, and toxicities with long-term treatment were generally controllable with axitinib dose modification and/or standard medications in these Japanese patients. Some frequently reported adverse events warrant close monitoring and management. Changes in the plasma levels of soluble vascular endothelial growth factor receptor-2 may be used as a prognostic factor for overall survival in metastatic renal cell carcinoma following axitinib treatment. This study is registered at ClinicalTrial.gov (identifier NCT00569946).

Population pharmacokinetic analysis of axitinib in healthy volunteers

AIMS

Axitinib is a potent and selective second generation inhibitor of vascular endothelial growth factor receptors 1, 2 and 3 approved for second line treatment of advanced renal cell carcinoma. The objectives of this analysis were to assess plasma pharmacokinetics and identify covariates that may explain variability in axitinib disposition following single dose administration in healthy volunteers.

METHODS

Plasma concentration-time data from 337 healthy volunteers in 10 phase I studies were analyzed, using non-linear mixed effects modelling (nonmem) to estimate population pharmacokinetic parameters and evaluate relationships between parameters and food, formulation, demographic factors, measures of renal and hepatic function and metabolic genotypes (UGT1A1*28 and CYP2C19).

RESULTS

A two compartment structural model with first order absorption and lag time best described axitinib pharmacokinetics. Population estimates for systemic clearance (CL), central volume of distribution (Vc ), absorption rate constant (ka ) and absolute bioavailability (F) were 17.0 l h(-1) , 45.3 l, 0.523 h(-1) and 46.5%, respectively. With axitinib Form IV, ka and F increased in the fasted state by 207% and 33.8%, respectively. For Form XLI (marketed formulation), F was 15% lower compared with Form IV. CL was not significantly influenced by any of the covariates studied. Body weight significantly affected Vc , but the effect was within the estimated interindividual variability for Vc .

CONCLUSIONS

The analysis established a model that adequately characterizes axitinib pharmacokinetics in healthy volunteers. Vc was found to increase with body weight. However, no change in plasma exposures is expected with change in body weight; hence no dose adjustment is warranted.

Cabozantinib-induced thyroid dysfunction: a review of two ongoing trials for metastatic bladder cancer and sarcoma

BACKGROUND

Thyroid dysfunction is a common adverse event associated with tyrosine kinase inhibitors (TKI), but its underlying pathophysiology is unclear. Cabozantinib is a novel TKI currently Food and Drug Administration approved for advanced medullary thyroid cancer and tested in clinical trials on solid tumors including prostate, liver, bladder, breast, and ovarian cancer.

METHODS

We analyzed the thyroid function of patients enrolled in two phase 2 clinical trials using cabozantinib at the National Institutes of Health Clinical Center. Two cases of thyroiditis associated with cabozantinib therapy are presented in detail, and a systematic review of the literature on TKI-associated thyroid dysfunction is also discussed.

RESULTS

Between September 2012 and September 2013, 33 patients were treated with cabozantinib, and follow-up thyroid function tests were available for 31 (20 males, 11 females; age 59±1 years). Thyroid dysfunction was recorded in the majority of patients (93.1%), with a predominance of subclinical hypothyroidism. Two cases showed a biphasic pattern of thyroid dysfunction characterized by a transient thyrotoxicosis followed by hypothyroidism. Color Doppler demonstrated an increase in vascularization during the thyrotoxic phase, but no uptake was visualized on nuclear medicine imaging. A systematic review of the literature resulted in the identification of 40 original manuscripts, of which 13 were case series and 6 were case reports describing TKI-associated thyroid dysfunction.

CONCLUSION

TKI therapy often results in clinically significant thyroid dysfunction. Cabozantinib treatment commonly results in thyroid dysfunction varying from subclinical hypothyroidism to symptomatic thyrotoxicosis. Early detection and characterization of cabozantinib-associated thyroid dysfunction and close follow-up are essential to provide adequate management of this common adverse event.

Clinical pharmacokinetics of tyrosine kinase inhibitors: implications for therapeutic drug monitoring

The treatment of many malignancies has been improved in recent years by the introduction of molecular targeted therapies. These drugs interact preferentially with specific targets that are mutated and/or overexpressed in malignant cells. A group of such targets are the tyrosine kinases, against which a number of inhibitors (tyrosine kinase inhibitors, TKIs) have been developed. Imatinib, a TKI with targets that include the breakpoint cluster region-Abelson (bcr-abl) fusion protein kinase and mast/stem cell growth factor receptor kinase (c-Kit), was the first clinically successful drug of this type and revolutionized the treatment and prognosis of chronic myeloid leukemia and gastrointestinal stromal tumors. This success paved the way for the development of other TKIs for the treatment of a range of hematological malignancies and solid tumors. To date, 14 TKIs have been approved for clinical use and many more are under investigation. All these agents are given orally and are substrates of a range of drug transporters and metabolizing enzymes. In addition, some TKIs are capable of inhibiting their own transporters and metabolizing enzymes, making their disposition and metabolism at steady-state unpredictable. A given dose can therefore give rise to markedly different plasma concentrations in different patients, favoring the selection of resistant clones in the case of subtherapeutic exposure, and increasing the risk of toxicity if dosage is excessive. The aim of this review was to summarize current knowledge of the clinical pharmacokinetics and known adverse effects of the TKIs that are available for clinical use and to provide practical guidance on the implications of these data in patient management, in particular with respect to therapeutic drug monitoring.

Clinical pharmacology of axitinib

Axitinib is a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors 1, 2, and 3 that is approved in the US and several other countries for treatment of patients with advanced renal cell carcinoma after failure of one prior systemic therapy. The recommended clinical starting dose of axitinib is 5 mg twice daily, taken with or without food. Dose increase (up to a maximum of 10 mg twice daily) or reduction is permitted based on individual tolerability. Axitinib pharmacokinetics are dose-proportional within 1-20 mg twice daily, which includes the clinical dose range. Axitinib has a short effective plasma half-life (range 2.5-6.1 h), and the plasma accumulation of axitinib is in agreement with what is expected based on the plasma half-life of the drug. Axitinib is absorbed relatively rapidly, reaching maximum observed plasma concentrations (C max) within 4 h of oral administration. The mean absolute bioavailability of axitinib is 58 %. Axitinib is highly (>99 %) bound to human plasma proteins with preferential binding to albumin and moderate binding to α1-acid glycoprotein. In patients with advanced renal cell carcinoma, at the 5-mg twice-daily dose in the fed state, the geometric mean (% coefficient of variation) C max and area under the plasma concentration-time curve (AUC) from time 0-24 h (AUC24) were 27.8 ng/mL (79 %) and 265 ng·h/mL (77 %), respectively. Axitinib is metabolized primarily in the liver by cytochrome P450 (CYP) 3A4/5 and, to a lesser extent (<10 % each), by CYP1A2, CYP2C19, and uridine diphosphate glucuronosyltransferase (UGT) 1A1. The two major human plasma metabolites, M12 (sulfoxide product) and M7 (glucuronide product), are considered pharmacologically inactive. Axitinib is eliminated via hepatobiliary excretion with negligible urinary excretion. Although mild hepatic impairment does not affect axitinib plasma exposures compared with subjects with normal hepatic function, there was a 2-fold increase in AUC from time zero to infinity (AUC∞) following a single 5-mg dose in subjects with moderate hepatic impairment. In the presence of ketoconazole, a strong CYP3A4/5 inhibitor, axitinib C max and AUC∞ increased by 1.5- and 2-fold, respectively, whereas co-administration of rifampin, a strong CYP3A4/5 inducer, resulted in a 71 and 79 % decrease in the C max and AUC∞, respectively. Axitinib does not inhibit CYP3A4/5, CYP1A2, CYP2C8, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, or UGT1A1 at concentrations obtained with the clinical doses and is not expected to have major interactions with drugs that are metabolized by these enzymes. Axitinib is an inhibitor of the efflux transporter P-glycoprotein (P-gp) in vitro, but is not expected to inhibit P-gp at therapeutic plasma concentrations. A two-compartment population pharmacokinetic model with first-order absorption and lag time was used to describe axitinib pharmacokinetics. No clinically relevant effects of age, sex, body weight, race, renal function, UGT1A1 genotype, or CYP2C19 inferred phenotype on the clearance of axitinib were identified.

Dysphonia induced by anti-angiogenic compounds

The number of studies reporting the benefit of angiogenesis inhibition is steadily increasing. Anti-angiogenic drugs, used as monotherapy or in association with chemotherapy, have been shown to benefit patients with several different malignancies. Despite the benefits of these therapies, however, each drug has different side effects. This review is specifically focused on analyzing the frequency of one of the complications the most frequently overlooked by physicians, dysphonia. Perhaps this side effect is overlooked because it is not life-threatening, but dysphonia may nevertheless affect quality of life considerably. We reviewed 88 studies concerning treatment with anti-angiogenics (bevacizumab, aflibercept, sunitinib, sorafenib, pazopanib, axitinib and regorafenib) presently approved for clinical use, to review the incidence of dysphonia or voice changes in phase I, II and III closed clinical studies reported in ClinicalTrials.gov until March 2013. We found that almost all studies reported certain degree of dysphonia in the trial arms associated with anti-angiogenic treatment. We discuss these findings in light of the fact that it is not an uncommon side effect in patients exposed to these kinds of drugs. Particularly for treatments with axitinib, aflibercept and regorafenib, the angiogenesis inhibition possibly plays a role by altering the larynx in some way and modifying vocal fold vibrations, leading to dysphonia.

Axitinib for the treatment of advanced renal cell carcinoma

INTRODUCTION

Advanced understanding of the pathogenesis of renal cell carcinoma (RCC) has led to development and approval of several molecularly targeted therapies since 2005. Axitinib is a potent and selective inhibitor of vascular endothelial growth factor receptors 1, 2 and 3. In the randomized Phase III AXIS trial, axitinib significantly prolonged progression-free survival compared with sorafenib, respectively (6.7 vs 4.7 months; p < 0.0001), and improved objective response rate (19 vs 9%; p = 0.0001), resulting in its approval for advanced or metastatic RCC after failure of one systemic therapy. However, overall survival was similar with axitinib and sorafenib. Common adverse events associated with axitinib include diarrhea, hypertension and fatigue.

AREAS COVERED

The properties, clinical efficacy, adverse events, pharmacokinetics and pharmacodynamics of axitinib are summarized and its position in the overall therapeutic landscape for metastatic RCC among several targeted therapies is described.

EXPERT OPINION

Axitinib is generally well-tolerated and provides definitive clinical benefits in patients with advanced or metastatic RCC as second-line therapy. However, as with other tyrosine kinase inhibitors of the same class, axitinib does not prolong overall survival; therefore, selection of second-line tyrosine kinase inhibitor therapy, including axitinib, must be carefully considered to maximize outcomes for each patient.

Thyroid dysfunction as an unintended side effect of anticancer drugs

BACKGROUND

Several of the currently used anticancer drugs may variably affect thyroid function, with impairment ranging from modified total but not free concentration of thyroid hormones to overt thyroid disease.

SUMMARY

Cytotoxic agents seem to alter thyroid function in a relatively small proportion of adult patients. Anticancer hormone drugs may mainly alter serum levels of thyroid hormone-binding proteins without clinically relevant thyroid dysfunction. Old immunomodulating drugs, such as interferon-α and interleukin-2, are known to induce variably high incidence of autoimmune thyroid dysfunction. Newer immune checkpoint inhibitors, such as anti-CTLA4 monoclonal antibodies, are responsible for a relatively low incidence of thyroiditis and may induce secondary hypothyroidism resulting from hypophysitis. Central hypothyroidism is a well-recognized side effect of bexarotene. Despite their inherent selectivity, tyrosine kinase inhibitors may cause high rates of thyroid dysfunction. Notably, thyroid toxicity seems to be restricted to tyrosine kinase inhibitors targeting key kinase-receptors in angiogenic pathways, but not other kinase-receptors (e.g., epidermal growth factor receptors family or c-KIT). In addition, a number of these agents may also increase the levothyroxine requirement in thyroidectomized patients.

CONCLUSIONS

The pathophysiology of thyroid toxicity induced by many anticancer agents is not fully clarified and for others it remains speculative. Thyroid dysfunction induced by anticancer agents is generally manageable and dose reduction or discontinuation of these agents is not required. The prognostic relevance of thyroid autoimmunity, overt and subclinical hypothyroidism induced by anticancer drugs, the value of thyroid hormone replacement in individuals with abnormal thyrotropin following anticancer systemic therapy, and the correct timing of replacement therapy in cancer patients need to be defined more accurately in well-powered prospective clinical trials.

Tyrosine kinase inhibitors induced thyroid dysfunction: a review of its incidence, pathophysiology, clinical relevance, and treatment

Tyrosine kinase inhibitors (TKI) belong to a new class of molecular multitargeted anticancer therapy which targets different growth factor receptors and hence attenuates cancer cell survival and growth. Since their introduction as adjunct treatment for renal cell carcinoma and gastrointestinal stromal tumors (GIST), a number of reports have demonstrated that TKI can induce thyroid dysfunction which was especially more common with sunitinib maleate. Many mechanisms with respect to this adverse effect of tyrosine kinase inhibitors have been proposed including their induction of thyroiditis, capillary regression in the thyroid gland, antithyroid peroxidase antibody production, and their ability to decrease iodine uptake by the thyroid gland. Of interest is the observation that TKI-induced thyroid dysfunction may actually be protective as it was shown to improve overall survival, and it was suggested that it may have a prognostic value. Followup on thyroid function tests while patients are maintained on tyrosine kinase inhibitor is strongly recommended. When thyroid dysfunction occurs, appropriate treatment should be individualized depending on patients symptoms and thyroid stimulating hormone level.

Tyrosine kinase inhibitors: their on-target toxicities as potential indicators of efficacy

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of certain forms of cancers, raising hopes for many patients with otherwise unresponsive tumours. While these agents are generally well tolerated, clinical experience with them has highlighted their unexpected association with serious toxic effects on various organs such as the heart, lungs, liver, kidneys, thyroid, skin, blood coagulation, gastrointestinal tract and nervous system. Many of these toxic effects result from downstream inhibition of vascular endothelial growth factor or epidermal growth factor signalling in cells of normal organs. Many of these undesirable effects such as hypertension, hypothyroidism, skin reactions and possibly proteinuria are on-target effects. Since tyrosine kinases are widely distributed with specific functional roles in different organs, this association is not too surprising. Various studies suggest that the development of these on-target effects indicates clinically desirable and effective inhibition of the corresponding ligand-mediated receptor linked with oncogenesis. This is reflected as improved efficacy in the subgroup of patients who develop these on-target adverse effects compared with those who do not. Inevitably, issues arise with respect to the regulatory assessment of efficacy and risk/benefit of the TKIs as well as the clinical approach to managing patients who develop these effects. Routine subgroup analysis of efficacy data from clinical trials (patients with and without on-target toxicity) may enable more effective clinical use of TKIs since (i) discontinuing or reducing the dose of the TKI has a negative impact if the tumour is TKI-responsive; and (ii) it is usually possible to manage these undesirable on-target effects with conventional clinical approaches. Prospective studies are needed to investigate this proposition further.

Efficacy and safety of axitinib versus sorafenib in metastatic renal cell carcinoma: subgroup analysis of Japanese patients from the global randomized Phase 3 AXIS trial

OBJECTIVE

Axitinib is a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors 1, 2 and 3. The efficacy and safety of axitinib in Japanese patients with metastatic renal cell carcinoma were evaluated.

METHODS

A subgroup analysis was conducted in Japanese patients enrolled in the randomized Phase III trial of axitinib versus sorafenib after failure of one prior systemic therapy for metastatic renal cell carcinoma.

RESULTS

Twenty-five (of 361) and 29 (of 362) patients randomized to the axitinib and sorafenib arms, respectively, were Japanese and included in this analysis. Median progression-free survival in Japanese patients was 12.1 months (95% confidence interval 8.6 to not estimable) for axitinib and 4.9 months (95% confidence interval 2.8-6.6) for sorafenib (hazard ratio 0.390; 95% confidence interval 0.130-1.173; stratified one-sided P = 0.0401). The objective response rate was 52.0% for axitinib and 3.4% for sorafenib (P = 0.0001). The common all-causality adverse events (all grades) in Japanese patients were dysphonia (68%), hypertension (64%), hand-foot syndrome (64%) and diarrhea (56%) for axitinib, and hand-foot syndrome (86%), hypertension (62%) and diarrhea (52%) for sorafenib. The safety profiles of axitinib and sorafenib in Japanese patients were generally similar to those observed in the overall population, with the exceptions of higher incidences of hypertension, dysphonia, hand-foot syndrome, hypothyroidism and stomatitis.

CONCLUSIONS

Axitinib is efficacious and well tolerated in Japanese patients with previously treated metastatic renal cell carcinoma, consistent with the results in the overall population, providing a new targeted therapy for these Japanese patients.

Inappropriate elevation of serum thyrotropin levels in patients treated with axitinib

BACKGROUND

Although anticancer treatment with the tyrosine kinase inhibitor (TKI) axitinib frequently causes thyroid dysfunction, the associated mechanism and clinical features have not been elucidated.

METHODS

Six patients were treated with axitinib for metastatic renal cell carcinoma at the Hamamatsu University School of Medicine between 2008 and 2010. We reviewed their thyroid function results and compared them to those of patients treated with two other TKIs, sunitinib or sorafenib, and to those of subjects with normal hypothalamic-pituitary-thyroid (HPT) function.

RESULTS

Axitinib-induced thyroid dysfunction was observed in all patients, and two patterns were observed: increased serum thyrotropin (TSH) levels within one month after administration occurred in five patients and transient thyrotoxicosis due to destructive thyroiditis occurred in five patients within 7 months of treatment. Four patients exhibited both. When the relationship between the serum TSH and thyroid hormones was evaluated using plots of TSH versus both free thyroxine and free triiodothyronine, four patients showed an inappropriate elevation of serum TSH during administration of axitinib. Their values apparently shifted against the regression line compared to data from patients with a normal HPT function. A similar tendency, though weaker, was observed in some patients treated with sunitinib or sorafenib.

CONCLUSION

This is the first study to report an inappropriate elevation of serum TSH levels in patients treated with axitinib.

Axitinib in metastatic renal cell carcinoma: results of a pharmacokinetic and pharmacodynamic analysis

Axitinib is a potent and selective inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, approved for second-line therapy for advanced renal cell carcinoma (RCC). Axitinib population pharmacokinetic and pharmacokinetic/pharmacodynamic relationships were evaluated. Using nonlinear mixed effects modeling with pooled data from 383 healthy volunteers, 181 patients with metastatic RCC, and 26 patients with other solid tumors in 17 trials, the disposition of axitinib was best described by a 2-compartment model with first-order absorption and a lag time, with estimated mean systemic clearance (CL) of 14.6 L/h and central volume of distribution (V(c)) of 47.3 L. Of 12 covariates tested, age over 60 years and Japanese ethnicity were associated with decreased CL, whereas V(c) increased with body weight. However, the magnitude of predicted changes in exposure based on these covariates does not warrant dose adjustments. Multivariate Cox proportional hazard regression and logistic regression analyses showed that higher exposure and diastolic blood pressure were independently associated with longer progression-free and overall survivals and higher probability of partial response in metastatic RCC patients. These findings support axitinib dose titration to increase plasma exposure in patients who tolerate axitinib, and also demonstrate diastolic blood pressure as a potential marker of efficacy.

Axitinib in Metastatic Renal Cell Carcinoma

Targeted agents have revolutionized the management of metastatic renal cell carcinoma (RCC). Axitinib, an inhibitor of vascular endothelial growth factor receptor (VEGFR), has been an important addition to currently available therapies for advanced RCC. Its ability to inhibit VEGFRs at nanomolar concentrations distinguishes it as a potent tyrosine kinase inhibitor, with increased selectivity for VEGFR-1, 2, and 3 at clinically applicable concentrations. The phase 3 AXIS trial has established its superiority in prolonging progression-free survival (PFS) in previously treated RCC patients (median PFS 6.7 months for axitinib vs. 4.7 months for sorafenib). Common toxicities of axitinib include hypertension, diarrhea, nausea, hand-foot syndrome, fatigue, and hypothyroidism. Axitinib-induced diastolic blood pressure elevation may be associated with improved clinical outcome, likely reflecting the “on-target” effect of axitinib. Dose escalation to achieve therapeutic plasma drug levels is of considerable clinical interest. Although axitinib has established efficacy in patients treated with one previous agent, its use in the frontline setting is currently the subject of ongoing research.

A phase I study of BMS-690514 in Japanese patients with advanced or metastatic solid tumors

Purpose

BMS-690514 is a novel oral tyrosine kinase inhibitor of ErbB and vascular endothelial growth factor receptor. This open-label phase I dose-escalation study (ClinicalTrials.gov Identifier: NCT00516451) aimed to assess the safety, preliminary efficacy, pharmacokinetics, and pharmacodynamics of BMS-690514 in Japanese patients with advanced or metastatic solid tumors.

Methods

Patients with advanced or metastatic solid tumors received oral BMS-690514 once daily continuously until disease progression or intolerable toxicity occurred. Dose-limiting toxicity (DLT) was evaluated from the first dose to Day 29. Dose levels at 100 and 200 mg were investigated. Assessments included adverse events, tumor response, pharmacokinetics, pharmacodynamics, 2 [18F] fluoro-2-deoxyglucose positron-emitting tomography, and epidermal growth factor receptor and K-ras mutations.

Results

BMS-690514 at the dose of 100 mg (n = 3) or 200 mg (n = 3) was administered once daily to totally nine patients and was well tolerated up to 200 mg. No treatment-related serious adverse events or DLTs were reported. Frequently observed treatment-related AEs were acne, diarrhea, dry skin, hypertension, stomatitis, blood fibrinogen increased, hemoglobin decreased, pruritus, and hypoalbuminemia. These were generally reported as Grade 1 and 2. Five of 9 patients (56 %) had stable disease. Plasma concentrations of BMS-690514 reached Cmax within 3 h and declined with an effective half-life of approximately 10 and 12 h at 100 and 200 mg, respectively.

Conclusions

Oral BMS-690514 was well tolerated in Japanese patients with advanced or metastatic solid tumors up to 200 mg.

Axitinib for the treatment of patients with advanced metastatic renal cell carcinoma (mRCC) after failure of prior systemic treatment

The landscape of renal cell carcinoma (RCC) treatment has changed dramatically during recent years. Bevacizumab/interferon, sunitinib, sorafenib, temsirolimus, everolimus, and pazopanib have been proven effective in metastatic RCC. Axitinib is a novel tyrosine kinase inhibitor, which inhibits the vascular endothelial growth factor receptor (VEGFR) at subnanomolar level. Based on this extraordinary VEGFR inhibition, axitinib is considered a next-generation agent. The recent AXIS trial reported on axitinib's efficacy in second line treatment of RCC, which led to its recent approval in the USA. This review focuses on the clinical efficacy of axitinib in RCC patients.

An open-label, phase 1 study evaluating safety, tolerability, and pharmacokinetics of linifanib (ABT-869) in Japanese patients with solid tumors

Purpose

This phase 1 study assessed the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of linifanib in Japanese patients with advanced solid tumors.

Methods

Patients were assigned to one of four sequential cohorts (0.05, 0.10, 0.20, or 0.25 mg/kg) of oral, once-daily linifanib on a 21-day cycle. Adverse events (AEs) were assessed per common terminology criteria for adverse events v3.0; tumor responses were assessed by response evaluation criteria in solid tumors.

Results

Eighteen patients were enrolled. Eleven (61%) received ≥3 prior therapies. Dose-limiting toxicities were Grade 3 ALT increase (0.10 mg/kg linifanib) and Grade 1 T-wave inversion (0.25 mg/kg linifanib) requiring dose interruption for >7 days and discontinuation on day 29. The most common linifanib-related AE was hypertension. Other significant treatment-related AEs included proteinuria, fatigue, and palmar-plantar erythrodysaesthesia. Linifanib pharmacokinetics were dose-proportional across 0.10–0.25 mg/kg. Two patients (11.1%) had confirmed partial responses, 12 had a best response of stable disease (11 had stable disease for ≥12 weeks), and four patients were not evaluable due to incomplete data. Four patients (lung cancer, breast cancer, thymic cancer, sarcoma) have continued linifanib for ≥48 weeks (range, 48–96+ weeks).

Conclusion

Linifanib was well tolerated with promising preliminary clinical activity in Japanese patients. Later-phase global studies examining linifanib efficacy will include Japanese patients.

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.

Radioactive iodine (131I) therapy for differentiated thyroid cancer in Japan: current issues with historical review and future perspective

Radioactive iodine (RAI, (131)I) has been used as a therapeutic agent for differentiated thyroid cancer (DTC) with over 50 years of history. Recently, it is now attracting attention in medical fields as one of the molecular targeting therapies, which is known as targeted radionuclide therapy. Radioactive iodine therapy (RIT) for DTC, however, is now at stake in Japan, because Japan is confronting several problems, including the recent occurrence of the Great East Japan Disaster (GEJD) in March 2011. RIT for DTC is strictly limited in Japan and requires hospitalization. Because of strict regulations, severe lack of medical facilities for RIT has become one of the most important medical problems, which results in prolonged waiting time for Japanese patients with DTC, including those with distant metastasis, who wish to receive RIT immediately. This situation is also due to various other factors, such as prolonged economic recession, super-aging society, and subsequent rapidly changing medical environment. In addition, due to the experience of atomic bombings in Hiroshima and Nagasaki, Japanese people have strong feeling of "radiophobia". There is fear that GEJD and related radiation contamination may worsen this feeling, which might be reflected in more severe regulation of RIT. To overcome these difficulties, it is essential to collect and disclose all information about the circumstances around this therapy in Japan. In this review, we would like to look at this therapy through several lenses, including historical, cultural, medical, and socio-economic points of view. We believe that clarifying the problems is sure to lead to the resolution of this complicated situation. We have also included several recommendations for future improvements.

Thyroid dysfunction from antineoplastic agents

Unlike cytotoxic agents that indiscriminately affect rapidly dividing cells, newer antineoplastic agents such as targeted therapies and immunotherapies are associated with thyroid dysfunction. These include tyrosine kinase inhibitors, bexarotene, radioiodine-based cancer therapies, denileukin diftitox, alemtuzumab, interferon-α, interleukin-2, ipilimumab, tremelimumab, thalidomide, and lenalidomide. Primary hypothyroidism is the most common side effect, although thyrotoxicosis and effects on thyroid-stimulating hormone secretion and thyroid hormone metabolism have also been described. Most agents cause thyroid dysfunction in 20%-50% of patients, although some have even higher rates. Despite this, physicians may overlook drug-induced thyroid dysfunction because of the complexity of the clinical picture in the cancer patient. Symptoms of hypothyroidism, such as fatigue, weakness, depression, memory loss, cold intolerance, and cardiovascular effects, may be incorrectly attributed to the primary disease or to the antineoplastic agent. Underdiagnosis of thyroid dysfunction can have important consequences for cancer patient management. At a minimum, the symptoms will adversely affect the patient's quality of life. Alternatively, such symptoms can lead to dose reductions of potentially life-saving therapies. Hypothyroidism can also alter the kinetics and clearance of medications, which may lead to undesirable side effects. Thyrotoxicosis can be mistaken for sepsis or a nonendocrinologic drug side effect. In some patients, thyroid disease may indicate a higher likelihood of tumor response to the agent. Both hypothyroidism and thyrotoxicosis are easily diagnosed with inexpensive and specific tests. In many patients, particularly those with hypothyroidism, the treatment is straightforward. We therefore recommend routine testing for thyroid abnormalities in patients receiving these antineoplastic agents.

Irinotecan synergistically enhances the antiproliferative and proapoptotic effects of axitinib in vitro and improves its anticancer activity in vivo

AIMS

To demonstrate the synergistic antiproliferative and proapoptotic activity of irinotecan and axitinib in vitro and the improvement of the in vivo effects on angiogenesis and pancreatic cancer.

METHODS

Proliferation and apoptotic assays were performed on human dermal microvascular endothelial cells and pancreas cancer (MIAPaCa-2, Capan-1) cell lines exposed to SN-38, the active metabolite of irinotecan, axitinib, or their simultaneous combination for 72 hours. ERK1/2 and Akt phosphorylation, the vascular endothelial growth factor (VEGF), VEGF receptor-2, and thrombospondin-1 (TSP-1) concentration were measured by ELISAs. ATP7A and ABCG2 gene expression was performed with real-time polymerase chain reaction and SN-38 intracellular concentrations were measured by high-performance liquid chromatography. Capan-1 xenografts in nude mice were treated with irinotecan and axitinib alone or in simultaneous combination.

RESULTS

A strong synergistic effect on antiproliferative and proapoptotic activity was found with the axitinib/SN-38 combination on endothelial and cancer cells. ERK1/2 and Akt phosphorylation were significantly inhibited by lower concentrations of the combined drugs in all the cell lines. Axitinib and SN-38 combined treatment greatly inhibited the expression of the ATP7A and ABCG2 genes in endothelial and cancer cells, increasing the SN-38 intracellular concentration. Moreover, TSP-1 secretion was increased in cells treated with both drugs, whereas VEGFR-2 levels significantly decreased. In vivo administration of the simultaneous combination determined an almost complete regression of tumors and tumor neovascularization.

CONCLUSIONS

In vitro results show the highly synergistic properties of simultaneous combination of irinotecan and axitinib on endothelial and pancreas cancer cells, suggesting a possible translation of this schedule into the clinics.

Does axitinib (AG-01376) have a future role in metastatic renal cell carcinoma and other malignancies?

Axitinib (Pfizer Inc., UK) is an oral small-molecule receptor tyrosine kinase inhibitor that targets angiogenesis. Axitinib has greater affinity and is a more selective inhibitor of VEGF receptor 1, -2 and -3, PDGFR and c-KIT than both sunitinib and sorafenib. It has encouraging efficacy and safety data in Phase II trials for metastatic renal cell carcinoma and advanced thyroid cancer patients. It is now being investigated in two Phase III trials in metastatic renal cell carcinoma and in Phase II trials in a range of tumor types. These trials will determine whether axitinib is an effective and safe antiangiogenic therapy.