Functional and Clinical Evidence of the Influence of Sorafenib Binding to Albumin on Sorafenib Disposition in Adult Cancer Patients

Tyrosine kinase inhibitors in cancers: Treatment optimization - Part II

Real-life populations are more heterogeneous than those included in prospective clinical studies. In cancer patients, comorbidities and co-medications favor the appearance of severe adverse effects which can significantly impact quality of life and treatment effectiveness. Most of tyrosine kinase inhibitors (TKI) have been developed with flat oral dosing exposing patients to the risk of poor adherence due to side effects. Additionally, genetic or physiological factors, differences in diet, and drug-drug interactions can lead to inter-individual variability affecting treatment outcomes and increasing the risk of adverse events. Knowledge of the different factors of variability allows individualized patient management. This review examines the effects of adherence, food intake, and pharmaceutical form on the pharmacokinetics of oral TKI, as well as evaluating pharmacokinetics considerations improving TKI management. Concentration-effectiveness and concentration-toxicity data are presented for the selected TKI, and a simple therapeutic drug monitoring schema is outlined to help individualize dosing of oral TKI.

Pharmacokinetic considerations for angiogenesis inhibitors used to treat hepatocellular carcinoma: an overview

INTRODUCTION

Hepatocellular carcinoma (HCC) is the fifth malignancy in terms of frequency and the fourth malignancy in terms of cancer-related death worldwide. Systemic therapy of advanced HCC has probably gone through the greatest wave of change in the last decade, with the introduction of several anti-angiogenic drugs and immune checkpoint inhibitors, able to significantly improve patients' prognosis.

AREAS COVERED

In this review, we summarize the pharmacokinetic characteristic of the antiangiogenic drugs currently approved for the treatment of HCC, from oral tyrosine kinase inhibitors (sorafenib, lenvatinib, regorafenib and cabozantinib) to monoclonal antibodies (bevacizumab and ramucirumab), focusing on the main aspects that differ among compounds from the same class, on factors that can exert an influence on pharmacokinetic parameters and the main issues that could limit their clinical use.

EXPERT OPINION

Anti-angiogenic drugs have different profiles in terms of bioavailability, metabolism, elimination and interindividual variability in their pharmacokinetics and effectiveness. More studies should be developed to address the intrinsic and extrinsic factors influencing pharmacokinetics parameters to improve the individual therapeutic response and, furthermore, to evaluate the benefit and the harm of systemic therapy for advanced HCC in selected patients with liver impairment.

Enhanced oral bioavailability and antitumor therapeutic efficacy of sorafenib administered in core-shell protein nanoparticle

Orally delivered molecularly targeted small-molecule drugs play a significant role in managing cancer as a chronic disease. However, due to the poor oral bioavailability of some of these molecules, high-dose administration is required leading to dose-limiting toxicity especially when delivered daily for a long duration. Here, we report an oral nanoformulation for small-molecule multi-kinase inhibitor, sorafenib tosylate, showing nearly two fold enhancement in the oral bioavailability and enhanced therapeutic efficacy with a better safety profile compared to the current clinical formulation. Using a scalable process involving high-pressure homogenization, sorafenib was loaded into an albumin nanocarrier at ~ 50 w/w%. Repeated preparation of gram-scale batches (n = 7) showed an average particle size of 180 ± 9 nm, encapsulation efficiency of 95 [Formula: see text] 2%, and drug-loading efficiency of 48 [Formula: see text] 0.7%. Further, surface engineering with a mucoadhesive layer on nanoparticles (referred to as ABSORF) resulted in the final size of 299 ± 38 nm and surface charge of -54 ± 8 mV. Single-dose and multidose pharmacokinetic studies showed two fold enhancement in the plasma concentration of sorafenib compared to current clinically used tablets. Antitumor efficacy studies in the orthotopic rat liver tumor model showed significant tumor regression (p value = 0.0037) even at half dose (eqv. to 200 mg of human equivalent dose) of ABSORF compared to clinical control (eqv. to 400 mg). The biodistribution of sorafenib from ABSORF was higher in the liver; however, liver and kidney function test parameters were comparable with that of the 2 × dose of clinical control. No abnormalities and signs of toxicity were seen in the histopathological analysis for ABSORF-treated animals. In summary, we demonstrate a scalable preparation of small-molecule drug-loaded nanoformulation with approximately two fold enhancement in oral bioavailability, improved antitumor efficacy, and acceptable toxicity profile.

Development of a PHBV nanoparticle as a peptide vehicle for NOD1 activation

NOD1 is an intracellular receptor that, when activated, induces gene expression of pro-inflammatory factors promoting macrophages and neutrophils recruitment at the infection site. However, iE-DAP, the dipeptide agonist that promotes this receptor's activation, cannot permeate cell membranes. To develop a nanocarrier capable of achieving a high and prolonged activation over time, iE-DAP was encapsulated in nanoparticles (NPs) made of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The physicochemical properties, colloidal stability, encapsulation efficiency, and cellular uptake of iE-DAP-loaded PHVB NPs were analyzed. Results evidenced that physicochemical properties of iE-DAP-loaded NPs remained stable over time, and NPs were efficiently internalized into cells, a process that depends on time and concentration. Moreover, our results showed that NPs elicited a controlled cargo release in vitro, and the encapsulated agonist response was higher than its free form, suggesting the possibility of activating intracellular receptors triggering an immune response through the release of NOD1 agonist.

Poly(3-Hydroxybutyrate)-Based Nanoparticles for Sorafenib and Doxorubicin Anticancer Drug Delivery

Dual drug-loaded nanotherapeutics can play an important role against the drug resistance and side effects of the single drugs. Doxorubicin and sorafenib were efficiently co-encapsulated by tailor-made poly([R,S]-3-hydroxybutyrate) (PHB) using an emulsion-solvent evaporation method. Subsequent poly(ethylene glycol) (PEG) conjugation onto nanoparticles was applied to make the nanocarriers stealth and to improve their drug release characteristics. Monodisperse PHB-sorafenib-doxorubicin nanoparticles had an average size of 199.3 nm, which was increased to 250.5 nm after PEGylation. The nanoparticle yield and encapsulation efficiencies of drugs decreased slightly in consequence of PEG conjugation. The drug release of the doxorubicin was beneficial, since it was liberated faster in a tumor-specific acidic environment than in blood plasma. The PEG attachment decelerated the release of both the doxorubicin and the sorafenib, however, the release of the latter drug remained still significantly faster with increased initial burst compared to doxorubicin. Nevertheless, the PEG-PHB copolymer showed more beneficial drug release kinetics in vitro in comparison with our recently developed PEGylated poly(lactic-co-glycolic acid) nanoparticles loaded with the same drugs.

Pharmacokinetics and pharmacogenetics of sorafenib in patients with hepatocellular carcinoma: Implications for combination trials

BACKGROUND & AIMS

Sorafenib and lenvatinib are the first-line treatments approved in hepatocellular carcinoma (HCC), but information is lacking about the relationships between their pharmacokinetics, patients pharmacogenetic profiles, adverse events (AE) and overall survival. We aimed to elucidate these relationships of tyrosine Kinase Inhibitors, such as sorafenib, in order to improve the design of trials testing it in combination with checkpoint inhibitors.

METHODS

We assessed the pharmacokinetics of sorafenib and its N-oxide metabolite at day-0, day-7, day-30, day-60, day-90, day-120, day-150 and day-180 and nine single-nucleotide polymorphisms (SNP) in five genes related to sorafenib metabolism/transport to identify the best point for starting the combination between tyrosine kinases and checkpoint inhibitors.

RESULTS

We prospectively included 49 patients (96% cirrhotic, 37% hepatitis-C, 82% Child-Pugh-A and 59% BCLC-C). Pharmacokinetic values peaked at day-7 and progressively declined until day-60. In the 16 patients without further dose modifications after day-60, pharmacokinetic values remained stable through day-180 (sorafenib P = .90; N-oxide P = .93). Pharmacokinetic values were higher in patients with early dermatological adverse events and lower in patients with early diarrhoea. Sorafenib and N-oxide pharmacokinetic values varied linearly with different alleles of MRP2*3972.

CONCLUSIONS

Sorafenib's pharmacokinetics is heterogeneous across HCC patients. This heterogeneity affects adverse events development and must be taken into account in setting the dose and timing of its combination with checkpoint inhibitors.

Sorafenib Loaded Inhalable Polymeric Nanocarriers against Non-Small Cell Lung Cancer

PURPOSE

This exploration is aimed at developing sorafenib (SF)-loaded cationically-modified polymeric nanoparticles (NPs) as inhalable carriers for improving the therapeutic efficacy of SF against non-small cell lung cancer (NSCLC).

METHODS

The NPs were prepared using a solvent evaporation technique while incorporating cationic agents. The optimized NPs were characterized by various physicochemical parameters and evaluated for their aerosolization properties. Several in-vitro evaluation studies were performed to determine the efficacy of our delivery carriers against NSCLC cells.

RESULTS

Optimized nanoparticles exhibited an entrapment efficiency of ~40%, <200 nm particle size and a narrow poly-dispersity index. Cationically-modified nanoparticles exhibited enhanced cellular internalization and cytotoxicity (~5-fold IC₅₀ reduction vs SF) in various lung cancer cell types. The inhalable nanoparticles displayed efficient aerodynamic properties (MMAD ~ 4 μM and FPF >80%). In-vitro evaluation also resulted in a superior ability to inhibit cancer metastasis. 3D-tumor simulation studies further established the anti-cancer efficacy of NPs as compared to just SF.

CONCLUSION

The localized delivery of SF-loaded nanoparticles resulted in improved anti-tumor activity as compared to SF alone. Therefore, this strategy displays great potential as a novel treatment approach against certain lung cancers.

Therapies targeting the signal pathways of pheochromocytoma and paraganglioma

Pheochromocytoma and paraganglioma (PCC/PGL) are rare tumors that originate from adrenal or extra-adrenal chromaffin cells. A significant clinical manifestation of PCC/PGL is that the tumors release a large number of catecholamines continuously or intermittently, causing persistent or paroxysmal hypertension and multiple organ functions and metabolic disorders. Though majority of the tumors are non-metastatic, about 10% are metastatic tumors. Others even have estimated that the rate of metastasis may be as high as 26%. The disease is most common in individuals ranging from 20 to 50 years old and the age of onset strongly depends on the genetic background: patients with germline mutations in susceptible genes have an earlier presentation. Besides, there are no significant differences in the incidence between men and women. At present, traditional treatments, such as surgical treatment, radionuclide therapy, and chemotherapy are still prior choices. However, they all have several deficiencies so that the effects are not extremely significant. Contemporary studies have shown that hypoxia-associated signal pathway, associated with the cluster 1 genes of PCC/PGL, and increased kinase signal pathways, associated with the cluster 2 genes of PCC/PGL, are the two major pathways involving the molecular pathogenesis of PCC/PGL, indicating that PCC/PGL can be treated with targeted therapies in emerging trends. This article reviews the progress of molecular-targeted therapies for PCC/PGL.

Major pitfalls of protein kinase inhibitors prescription: A review of their clinical pharmacology for daily use

Protein kinase inhibitors (PKI) are a growing class of anticancer agents. They are prescribed with flat doses, and their oral administration is associated with interindividual variability in exposure. Patients can be over- or underexposed, due to numerous factors. We reviewed key pharmacokinetic concepts and mechanisms by which PKIs prescription could be altered. Challenging situations that could lead to increased toxicity or to therapeutic failure are described and recommendation for clinicians are proposed. Finally, the interest of therapeutic drug monitoring and indications for its use in daily practice is discussed.

Overexpression of c-Jun contributes to sorafenib resistance in human hepatoma cell lines

Background

Despite recent advances in treatment strategies, it is still difficult to cure patients with hepatocellular carcinoma (HCC). Sorafenib is the only approved multiple kinase inhibitor for systemic chemotherapy in patients with advanced HCC. The majority of advanced HCC patients are resistant to sorafenib. The mechanisms of sorafenib resistance are still unknown.

Methods

The expression of molecules involved in the mitogen-activated protein kinase (MAPK) signaling pathway in human hepatoma cell lines was examined in the presence or absence of sorafenib. Apoptosis of human hepatoma cells treated with sorafenib was investigated, and the expression of Jun proto-oncogene (c-Jun) was measured.

Results

The expression and phosphorylation of c-Jun were enhanced in human hepatoma cell lines after treatment with sorafenib. Inhibiting c-Jun enhanced sorafenib-induced apoptosis. The overexpression of c-Jun impaired sorafenib-induced apoptosis. The expression of osteopontin, one of the established AP-1 target genes, was enhanced after treatment with sorafenib in human hepatoma cell lines.

Conclusions

The protein c-Jun plays a role in sorafenib resistance in human hepatoma cell lines. The modulation and phosphorylation of c-Jun could be a new therapeutic option for enhancing responsiveness to sorafenib. Modulating c-Jun may be useful for certain HCC patients with sorafenib resistance.

Prognostic significance of adverse events in patients with hepatocellular carcinoma treated with sorafenib

Sorafenib is the standard treatment for patients with hepatocellular carcinoma (HCC) with advanced stage disease. Although its effectiveness has been demonstrated by randomized clinical trials and confirmed by field practice studies, reliable markers predicting therapeutic response have not yet been identified. Like other tyrosine kinase inhibitors, treatment with sorafenib is burdened by the development of adverse effects, the most frequent being cutaneous toxicity, diarrhoea, arterial hypertension and fatigue. In recent years, several studies have analysed the correlation between off-target effects and sorafenib efficacy in patients with HCC. In this review, an overview of the studies assessing the prognostic significance of sorafenib-related adverse events is provided.

Evaluation of antiangiogenic efficacy in advanced hepatocellular carcinoma: Biomarkers and functional imaging

Many years after therapeutic wilderness, sorafenib finally showed a clinical benefit in patients with advanced hepatocellular carcinoma. After the primary general enthusiasm worldwide, some disappointments emerged particularly since no new treatment could exceed or at least match sorafenib in this setting. Without these new drugs, research focused on optimizing care of patients treated with sorafenib. One challenging research approach deals with identifying prognostic and predictive biomarkers of sorafenib in this population. The task still seems difficult; however appropriate investigations could resolve this dilemma, as observed for some malignancies where other drugs were used.

Effect of glucuronidation on transport and tissue accumulation of tyrosine kinase inhibitors: consequences for the clinical management of sorafenib and regorafenib

INTRODUCTION

UDP-glucuronosyltransferases (UGTs) are a multigenic family of enzymes responsible for the glucuronidation reaction. Many therapeutic classes of drugs used in solid tumors are UGT substrates, including cancer therapies.

AREAS COVERED

This article describes the tyrosine kinase inhibitors (TKIs) undergoing hepatic glucuronidation; its effect on transport and tissue accumulation and the clinical consequences of this particular metabolism. A PubMed search concerning the pharmacokinetics of the TKIs was performed. All are extensively metabolized by CYP450. Two TKIs, sorafenib and regorafenib, also have a major UGT-mediated metabolism and were therefore studied.

EXPERT OPINION

The prescription of the same dose of sorafenib and regorafenib for all patients may be inappropriate since at each enzymatic step of this multistep metabolism inter-individual fluctuations exist. Having a non-exclusive CYP-mediated route of metabolism may reduce the risk of variability in drug exposure when CYP3A4 substrates are concomitantly given. Several clinical consequences derive from this pharmacokinetic particularity of sorafenib and regorafenib. Since no clear difference distinguishes TKIs in efficacy in large randomized trials, the differences for the clinical management of their toxicity is a critical aspect.

Binding interaction between sorafenib and calf thymus DNA: spectroscopic methodology, viscosity measurement and molecular docking

The binding interaction of sorafenib with calf thymus DNA (ct-DNA) was studied using UV-vis absorption spectroscopy, fluorescence emission spectroscopy, circular dichroism (CD), viscosity measurement and molecular docking methods. The experimental results revealed that there was obvious binding interaction between sorafenib and ct-DNA. The binding constant (Kb) of sorafenib with ct-DNA was 5.6×10(3) M(-1) at 298 K. The enthalpy and entropy changes (ΔH(0) and ΔS(0)) in the binding process of sorafenib with ct-DNA were -27.66 KJ mol(-1) and -21.02 J mol(-1) K(-1), respectively, indicating that the main binding interaction forces were van der Waals force and hydrogen bonding. The docking results suggested that sorafenib preferred to bind on the minor groove of A-T rich DNA and the binding site of sorafenib was 4 base pairs long. The conformation change of sorafenib in the sorafenib-DNA complex was obviously observed and the change was close relation with the structure of DNA, implying that the flexibility of sorafenib molecule played an important role in the formation of the stable sorafenib-ct-DNA complex.

Binding interaction of sorafenib with bovine serum albumin: Spectroscopic methodologies and molecular docking

The binding interaction of sorafenib with bovine serum albumin (BSA) was studied using fluorescence, circular dichrosim (CD) and molecular docking methods. The results revealed that there was a static quenching of BSA induced by sorafenib due to the formation of sorafenib-BSA complex. The binding constant and number of binding site of sorafenib with BSA under simulated physiological condition (pH=7.4) were 6.8×10(4) M(-1) and 1 at 310 K, respectively. Base on the sign and magnitude of the enthalpy and entropy changes (ΔH(0)=-72.2 kJ mol(-1) and ΔS(0)=-140.4J mol(-1) K(-1)) and the results of molecular docking, it could be suggested that the binding process of sorafenib and BSA was spontaneous and the main interaction forces of sorafenib with BSA were van der Waals force and hydrogen bonding interaction. From the results of site marker competitive experiments and molecular docking, it could be deduced that sorafenib was inserted into the subdomain IIA (site I) of BSA and leads to a slight change of the conformation of BSA. And, the significant change of conformation of sorafenib occurred in the binding process with BSA to increase the stability of the sorafenib-BSA system, implying that the flexibility of sorafenib played an important role in the binding process.

Transferrin targeted core-shell nanomedicine for combinatorial delivery of doxorubicin and sorafenib against hepatocellular carcinoma

Combinatorial drug delivery is an attractive, but challenging requirement of next generation cancer nanomedicines. Here, we report a transferrin-targeted core-shell nanomedicine formed by encapsulating two clinically used single-agent drugs, doxorubicin and sorafenib against liver cancer. Doxorubicin was loaded in poly(vinyl alcohol) nano-core and sorafenib in albumin nano-shell, both formed by a sequential freeze-thaw/coacervation method. While sorafenib from the nano-shell inhibited aberrant oncogenic signaling involved in cell proliferation, doxorubicin from the nano-core evoked DNA intercalation thereby killing >75% of cancer cells. Upon targeting using transferrin ligands, the nanoparticles showed enhanced cellular uptake and synergistic cytotoxicity in ~92% of cells, particularly in iron-deficient microenvironment. Studies using 3D spheroids of liver tumor indicated efficient penetration of targeted core-shell nanoparticles throughout the tissue causing uniform cell killing. Thus, we show that rationally designed core-shell nanoparticles can effectively combine clinically relevant single-agent drugs for exerting synergistic activity against liver cancer.

FROM THE CLINICAL EDITOR

Transferrin-targeted core-shell nanomedicine encapsulating doxorubicin and sorafenib was studied as a drug delivery system against hepatocellular carcinoma, resulting in enhanced and synergistic therapeutic effects, paving the way towards potential future clinical applications of similar techniques.

Drug safety evaluation of sorafenib for treatment of solid tumors: consequences for the risk assessment and management of cancer patients

INTRODUCTION

Sorafenib is a multi-tyrosine kinase inhibitor (TKI). Considerable clinical experience has been accumulated since its first Phase III clinical trial in metastatic renal cancer patients in 2007. The management of its early acute toxicity in fit patients is well known. The management of prolonged treatment becomes the new challenge.

AREAS COVERED

Using sorafenib as a key word for PubMed search, we review preclinical and clinical data and discuss the pharmacokinetics and pharmacodynamics of sorafenib, its acute and cumulative toxicities and their consequences for patient management.

EXPERT OPINION

The systematic multi-disciplinary risk assessment of cancer patients prior to TKI initiation reduces the risks of acute and late toxicity, especially drug-drug interactions and arterial risks. Sarcopenia is now identified as a major risk of severe toxicity. The very diverse clinical pictures of cumulative toxicity must be known. The monitoring of sorafenib systemic exposure is helpful especially in elderly patients. Moreover, at disease progression, it allows distinguishing between underexposure to sorafenib and truly acquired resistance to the drug. The optimal use of sorafenib should allow improving the reported results of flat-dose. Finally, most of this knowledge could be used for the development and optimal use of the other TKIs.

Sorafenib dose escalation is not uniformly associated with blood pressure elevations in normotensive patients with advanced malignancies

Hypertension with vascular endothelial growth factor (VEGF) receptor inhibitors is associated with superior treatment outcomes for advanced cancer patients. To determine whether increased doses of sorafenib cause incremental increases in blood pressure (BP) we measured 12-hour ambulatory BP in 41 normotensive advanced solid tumor patients in a randomized dose escalation study. After 7 days’ sorafenib (400mg BID) mean diastolic BP (DBP) increased in both study groups. After dose escalation, group A (400mg TID) had marginally significant further increase in 12-hour mean DBP (p=0.053) but group B (600mg BID) did not achieve statistically significant increases (p=0.25). Within groups, individuals varied in BP response to sorafenib dose escalation, but these differences did not correlate with changes in steady state plasma sorafenib concentrations. These findings in normotensive patients suggest BP is a complex pharmacodynamic biomarker of VEGF inhibition. Patients have intrinsic differences in sensitivity to the BP elevating effects of sorafenib.

Drug interactions with solid tumour-targeted therapies

Drug interactions are an on-going concern in the treatment of cancer, especially when targeted therapies, such as tyrosine kinase inhibitors (TKI) or mammalian target of rapamycin (mTOR) inhibitors, are being used. The emergence of elderly patients and/or patients with both cancer and other chronic co-morbidities leads to polypharmacy. Therefore, the risk of drug-drug interactions (DDI) becomes a clinically relevant issue, all the more so as TKIs and mTOR inhibitors are essentially metabolised by cytochrome P450 enzymes. These DDIs can result in variability in anticancer drug exposure, thus favouring the selection of resistant cellular clones or the occurrence of toxicity. This review provides a comprehensive overview of DDIs that involve targeted therapies approved by the FDA for the treatment of solid tumours for more than 3 years (sorafenib, sunitinib, erlotinib, gefitinib, imatinib, lapatinib, everolimus, temsirolimus) and medicinal herb or drugs. This review also provides some guidelines to help oncologists and pharmacists in their clinical practice.

Early sorafenib-induced toxicity is associated with drug exposure and UGTIA9 genetic polymorphism in patients with solid tumors: a preliminary study

Background

Identifying predictive biomarkers of drug response is of key importance to improve therapy management and drug selection in cancer therapy. To date, the influence of drug exposure and pharmacogenetic variants on sorafenib-induced toxicity remains poorly documented. The aim of this pharmacokinetic/pharmacodynamic (PK/PD) study was to investigate the relationship between early toxicity and drug exposure or pharmacogenetic variants in unselected adult outpatients treated with single-agent sorafenib for advanced solid tumors.

Methods

Toxicity was recorded in 54 patients on days 15 and 30 after treatment initiation and sorafenib exposure was assessed in 51 patients. The influence of polymorphisms in CYP3A5, UGT1A9, ABCB1 and ABCG2 was examined in relation to sorafenib exposure and toxicity. Clinical characteristics, drug exposure and pharmacogenetic variants were tested univariately for association with toxicities. Candidate variables with p<0.1 were analyzed in a multivariate analysis.

Results

Gender was the sole parameter independently associated with sorafenib exposure (p = 0.0008). Multivariate analysis showed that increased cumulated sorafenib (AUC_cum) was independently associated with any grade ≥3 toxicity (p = 0.037); UGT1A9 polymorphism (rs17868320) with grade ≥2 diarrhea (p = 0.015) and female gender with grade ≥2 hand-foot skin reaction (p = 0.018). Using ROC curve, the threshold AUC_cum value of 3,161 mg/L.h was associated with the highest risk to develop any grade ≥3 toxicity (p = 0.018).

Conclusion

In this preliminary study, increased cumulated drug exposure and UGT1A9 polymorphism (rs17868320) identified patients at high risk for early sorafenib-induced severe toxicity. Further PK/PD studies on larger population are warranted to confirm these preliminary results.

Sorafenib in advanced melanoma: a critical role for pharmacokinetics?

BACKGROUND

Inter-patient pharmacokinetic variability can lead to suboptimal drug exposure, and therefore might impact the efficacy of sorafenib. This study reports long-term pharmacokinetic monitoring of patients treated with sorafenib and a retrospective pharmacodynamic/pharmacokinetic analysis in melanoma patients.

PATIENTS AND METHODS

Heavily pretreated patients with stage IV melanoma were started on sorafenib 400 mg twice daily (bid). In the absence of limiting toxicity, dose escalation of 200 mg bid levels was done every 2 weeks. Plasma sorafenib measurement was performed at each visit, allowing a retrospective pharmacodynamic/pharmacokinetic analysis for safety and efficacy.

RESULTS

In all, 19 of 30 patients underwent dose escalation over 400 mg bid, and 28 were evaluable for response. The overall disease control rate was 61% (95% confidence interval (CI): 42.6-78.8), including three confirmed responses (12%). Disease control rate and progression-free survival (PFS) were improved in patients with high vs low exposure (80% vs 32%, P=0.02, and 5.25 vs 2.5 months, P=0.005, hazard ratio (HR)=0.28 (95% CI: 0.11-0.73)). In contrast, drug dosing had no effect on PFS. In multivariate analysis, drug exposure was the only factor associated with PFS (HR=0.36 (95% CI: 0.13-0.99)). Diarrhoea and anorexia were correlated with drug dosing, while hypertension and hand-foot skin reaction were correlated with drug exposure.

CONCLUSIONS

Although sorafenib had modest efficacy in melanoma, these results suggest a correlation between exposure and efficacy of sorafenib. Therefore, dose optimisation in patients with low exposure at standard doses should be evaluated in validated indications.

Exogenous albumin inhibits sorafenib-induced cytotoxicity in human cancer cell lines

Sorafenib is an orally administered multikinase inhibitor that exhibits anti-angiogenic and anti-tumor activity. Sorafenib is also known to bind to protein (>99.5%), suggesting protein binding may be involved in sorafenib pharmacokinetic variability. Albumin is a major drug-binding protein. In this study, we examined the effect of albumin on sorafenib-induced cytotoxicity using two in vitro culture cell lines, human hepatoma Huh-7 cells and androgen-independent prostate cancer PC-3 cells. The cells were cultured and incubated, and cytotoxicity was assessed. Results were confirmed by western blotting. The presence of exogenous albumin markedly blocked the sorafenib-induced cytotoxicity in the two cell lines. Albumin concentration, the change of pharmacological signal transduction as Raf-B, vascular endothelial growth factor (VEGF), and phosphorylation of MEK1/2 or ERK1/2 were found to be decreased by sorafenib. Co-incubation of warfarin, a representative coumarin anticoagulant and potent binding activity, with albumin enhanced the cytotoxic effects by sorafenib. These mechanisms depend on the high binding proper ties of sorafenib and exogenous albumin. Furthermore, we investigated the effects of endo genous albumin expression on sorafenib-induced cytotoxicity using the siRNA knockdown system or transfected expression vector assay. However, the cytotoxic effects by sorafenib showed little change either with the knockdown or overexpression of albumin. Our results suggest that particular care should be taken with albuminemia or the combined use of drugs with a high affinity for albumin, such as warfarin, and sorafenib in the treatment of cancer patients. Our findings may be useful to the cancer therapeutic strategy by sorafenib.

Is the toxicity of anti-angiogenic drugs predictive of outcome? A review of hypertension and proteinuria as biomarkers of response to anti-angiogenic therapy

INTRODUCTION

The prototypic anti-angiogenic agents, VEGF inhibitors, are increasingly used in clinical practice to treat a variety of tumours. Although generally well tolerated, their toxicities can be significant or occasionally life threatening. The ability to identify those patients whose disease will respond to VEGF inhibitors would minimise exposure to ineffective drugs for some patients. To date, there are no validated predictive or prognostic biomarkers for anti-angiogenic drugs. Toxicities such as hypertension and proteinuria are related to the effect of VEGF inhibition on the vasculature. This has led to the investigation of these toxicities as potential biomarkers of clinical outcome in patients treated with these agents.

AREAS COVERED

Putative mechanisms for the development of hypertension and proteinuria, and their potential role as clinically useful biomarkers in relation to anti-angiogenic drugs are discussed in this article. PUBMED, EMBASE and abstracts presented at the American Society of Clinical Oncology until July 2011 were searched to identify relevant English language articles. Studies of anti-angiogenic therapies testing the relationship of either hypertension or proteinuria with outcome were included.

EXPERT OPINION

The evidence in support of the hypothesis that hypertension and proteinuria are biomarkers of response to anti-angiogenic drugs is inconclusive. Current evidence suggests that hypertension is a pharmacodynamic effect of anti-angiogenic agents. Future studies should aim to measure and report toxicities in a standardised manner to facilitate comparisons between studies.

Plasma protein binding of sorafenib, a multi kinase inhibitor: in vitro and in cancer patients

Sorafenib is an orally administered multikinase inhibitor that exhibits antiangiogenic and antitumor activity. Few investigators have been able to correlate cumulative sorafenib dose or total exposure to pharmacodynamic effects. This discrepancy may be in part due to poorly understood protein binding characteristics. Since unbound drug concentrations are believed to be more relevant to pharmacological and toxicological responses than total drug, an equilibrium dialysis method using 96-well microdialysis plates was optimized and validated for determining the fraction unbound (F(u)) sorafenib in human plasma and in isolated protein solutions. Unbound sorafenib concentrations were determined in cancer patients receiving the drug orally at a dose of 400 mg and 600 mg twice daily. Sorafenib was extensively bound with mean F(u) value of 0.3% in both non-cancer and cancer patient's plasma. The binding in plasma was concentration independent, indicating a low-affinity, possibly nonspecific and nonsaturable process. In isolated protein solutions, 99.8% and 79.3% of sorafenib was bound to human serum albumin (HSA) (4 g/dL) and α(1)-acid glycoprotein (AAG) (0.1 g/dL) with binding constants of 1.24 × 10(6) M(-1) and 1.40 × 10(5) M(-1), respectively. In cancer patients receiving sorafenib, unbound sorafenib was not correlated with patient characteristics or laboratory values. In conclusion, sorafenib is highly protein bound in human plasma with a higher affinity towards albumin and limited free drug may be partly responsible for its borderline clinical activity.

Sorafenib exposure decreases over time in patients with hepatocellular carcinoma

BACKGROUND

Intra-patient variability in sorafenib pharmacokinetics has been poorly investigated to date. We hypothesized that sorafenib clearance could decrease over time, as seen with imatinib.

PATIENTS AND METHODS

Sorafenib plasma concentrations were determined by liquid chromatography, every 2 weeks, in consecutive hepatocellular carcinoma patients treated with sorafenib. Sorafenib dose-normalized area under the concentration-time curve (AUC) was determined from a population pharmacokinetics model, and its kinetics was analyzed in order to identify possible alterations of exposure over time.

RESULTS

Fifteen hepatocellular carcinoma patients with Child-Pugh A cirrhosis, in whom sorafenib dosing remained unchanged from initiation of treatment to disease progression, were eligible for this analysis. Sorafenib AUC significantly decreased over time: the median AUC during the third month of treatment was lower than that observed after one month of treatment (43.0 vs. 60.3 mg/L.h, p = 0.008). Most importantly, median sorafenib AUC at the time of progression was almost two-fold lower than that observed after one month of therapy (33.2 vs. 60.3 mg/L.h, p = 0.007). These findings suggest an induction of expression of efflux transporters in the gut wall, or an induction of sorafenib metabolism.

CONCLUSIONS

In patients with progressive disease in whom exposure markedly decreased from baseline, sorafenib dose escalation could be considered, aiming to restore an adequate drug exposure and possibly anti-tumor activity.