Quantitative Measure of Intestinal Permeability Using Blue Food Coloring.

BACKGROUND: Loss of intestinal barrier integrity plays a fundamental role in the pathogenesis of various gastrointestinal diseases and is implicated in the onset of sepsis and multiple organ failure. An array of methods to assess different aspects of intestinal barrier function suffers from lack of sensitivity, prolonged periods of specimen collection, or high expense. We have developed a technique to measure the concentration of the food dye FD&C Blue #1 from blood and sought to assess its utility in measuring intestinal barrier function in humans. MATERIALS AND METHODS: Four healthy volunteers and 10 critically ill subjects in the intensive care unit were recruited in accordance with an institutional review board approved protocol. Subjects were given 0.5 mg/kg Blue #1 enterally as an aqueous solution of diluted food coloring. Five blood specimens were drawn per subject: 0 h (before dose), 1, 2, 4, and 8 h. After plasma isolation, organic extracts were analyzed by high-performance liquid chromatography/mass spectrometry detecting the presence of unmodified dye. RESULTS: We found no baseline detectable absorption in healthy volunteers. After including the subjects in the intensive care unit, we compared dye absorption in the six subjects who met criteria for septic shock with the eight who did not. Septic patients demonstrated significantly greater absorption of Blue #1 after 2 h. CONCLUSIONS: We have developed a novel, easy-to-use method to measure intestinal barrier integrity using a food grade dye detectable by mass spectrometry analysis of patient blood following oral administration.

Tracking Antibody Distribution with Near-Infrared Fluorescent Dyes: Impact of Dye Structure and Degree of Labeling on Plasma Clearance.

Monoclonal antibodies labeled with near-infrared (NIR) fluorophores have potential use in disease detection, intraoperative imaging, and pharmacokinetic characterization of therapeutic antibodies in both the preclinical and clinical setting. Recent work has shown conjugation of NIR fluorophores to antibodies can potentially alter antibody disposition at a sufficiently high degree of labeling (DoL); however, other reports show minimal impact after labeling with NIR fluorophores. In this work, we label two clinically approved antibodies, Herceptin (trastuzumab) and Avastin (bevacizumab), with NIR dyes IRDye 800CW (800CW) or Alexa Fluor 680 (AF680), at 1.2 and 0.3 dyes/antibody and examine the impact of fluorophore conjugation on antibody plasma clearance and tissue distribution. At 0.3 DoL, AF680 conjugates exhibited similar clearance to unlabeled antibody over 17 days while 800CW conjugates diverged after 4 days, suggesting AF680 is a more suitable choice for long-term pharmacokinetic studies. At the 1.2 DoL, 800CW conjugates cleared faster than unlabeled antibodies after several hours, in agreement with other published reports. The tissue biodistribution for bevacizumab-800CW and -AF680 conjugates agreed well with literature reported biodistributions using radiolabels. However, the greater tissue autofluorescence at 680 nm resulted in limited detection above background at low (∼2 mg/kg) doses and 0.3 DoL for AF680, indicating that 800CW is more appropriate for short-term biodistribution measurements and intraoperative imaging. Overall, our work shows a DoL of 0.3 or less for non-site-specifically labeled antibodies (with a Poisson distribution) is ideal for limiting the impact of NIR fluorophores on antibody pharmacokinetics.

Improved oral absorption of cilostazol via sulfonate salt formation with mesylate and besylate.

OBJECTIVE: Cilostazol is a Biopharmaceutical Classification System class II drug with low solubility and high permeability, so its oral absorption is variable and incomplete. The aim of this study was to prepare two sulfonate salts of cilostazol to increase the dissolution and hence the oral bioavailability of cilostazol. METHODS: Cilostazol mesylate and cilostazol besylate were synthesized from cilostazol by acid addition reaction with methane sulfonic acid and benzene sulfonic acid, respectively. The salt preparations were characterized by nuclear magnetic resonance spectroscopy. The water contents, hygroscopicity, stress stability, and photostability of the two cilostazol salts were also determined. The dissolution profiles in various pH conditions and pharmacokinetic studies in rats were compared with those of cilostazol-free base. RESULTS: The two cilostazol salts exhibited good physicochemical properties, such as nonhygroscopicity, stress stability, and photostability, which make it suitable for the preparation of pharmaceutical formulations. Both cilostazol mesylate and cilostazol besylate showed significantly improved dissolution rate and extent of drug release in the pH range 1.2-6.8 compared to the cilostazol-free base. In addition, after oral administration to rats, cilostazol mesylate and cilostazol besylate showed increases in C max and AUC t of approximately 3.65- and 2.87-fold and 3.88- and 2.94-fold, respectively, compared to cilostazol-free base. CONCLUSION: This study showed that two novel salts of cilostazol, such as cilostazol mesylate and cilostazol besylate, could be used to enhance its oral absorption. The findings warrant further preclinical and clinical studies on cilostazol mesylate and cilostazol besylate at doses lower than the usually recommended dosage, so that it can be established as an alternative to the marketed cilostazol tablet.

Evidence for therapeutic drug monitoring of targeted anticancer therapies.

Therapeutic drug monitoring (TDM) provides valuable guidance for dose adjustment of antibiotics, immunosuppressives, antiepileptics, and other drugs, but its use for traditional anticancer therapies has been limited. Perhaps the most important obstacle is the impractical requirement of multiple blood samples to adequately define systemic exposure of drugs that have a short elimination half-life and are given by intermittent intravenous injections. However, the newer targeted anticancer therapies have different pharmacokinetic (PK) and dosing characteristics compared with traditional cytotoxic drugs, making it possible to estimate the steady-state drug exposure with a single trough-level measurement. Recent evidence indicates that certain PK parameters, including trough levels, are correlated with clinical outcomes for many of these agents, including imatinib, sunitinib, rituximab, and cetuximab. Although the current evidence is insufficient to mandate TDM in routine practice, a concerted investigation should be encouraged to determine whether the steady-state trough measurements of targeted agents will have a practical place in the clinical care of patients with cancer.

Preparation, in vitro release, and pharmacokinetics in rabbits of lyophilized injection of sorafenib solid lipid nanoparticles.

Sorafenib solid lipid nanoparticles (S-SLN) were prepared by emulsion evaporation-solidification at low temperature. Morphology was examined by transmission electron microscope. Particle size and zeta potential were determined by laser granularity equipment. Encapsulation efficiency (EE) was detected by Sephadex gel chromatography and high-performance liquid chromatography (HPLC). The in vitro release profile of S-SLN was studied with dialysis technology. The lyophilized injection of S-SLN was prepared by freeze drying and analyzed by differential scanning calorimetry. The plasma concentration of sorafenib in blood was determined by HPLC. The solid lipid nanoparticles assumed a spherical shape with an even distribution of diameter and particle size 108.23 ± 7.01 nm (n = 3). The polydispersity index, zeta potential, and EE were determined to be 0.25 ± 0.02, -16.37 ± 0.65 mV, and 93.49% ± 1.87%, respectively (n = 3). The in vitro release accorded with the Weibull distribution model. An equal volume of 15% (w/v) mannitol performed better as the protective agent for a lyophilized injection of S-SLN with a new material phase formation. The pharmacokinetic processes of sorafenib solution and lyophilized injection of S-SLN in vivo were in accordance with the two-compartment and one-compartment models, respectively. S-SLN nanoparticles are thus considered a promising drug-delivery system.

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.

Variability of sorafenib toxicity and exposure over time: a pharmacokinetic/pharmacodynamic analysis.

BACKGROUND: Sorafenib displays major interpatient pharmacokinetic variability. It is unknown whether the pharmacokinetics of sorafenib influence its toxicity. METHODS: We analyzed the severity and kinetics of sorafenib-induced toxicities in unselected consecutive patients with cancer, as well as their relationship with biological, clinical, and pharmacokinetic parameters. Toxicity was recorded bimonthly. Sorafenib plasma concentrations were assessed by liquid chromatography. RESULTS: For 83 patients (median age, 62 years; range, 21-84 years), median sorafenib 12-hour area under the curve (AUC(0-12)) was 52.8 mg · h/L (range: 11.8-199.6). A total of 51 patients (61%) experienced grade 3-4 toxicities, including hand-foot skin reactions (23%), asthenia (18%), and diarrhea (11%). Sorafenib AUC(0-12) preceding grade 3-4 toxicities was significantly higher than that observed in the remaining population (61.9 mg · h/L vs. 53 mg · h/L). In 25 patients treated with fixed doses of sorafenib for the first 4 months, median dose-normalized AUC(0-12) on day 120 was significantly lower than on day 15 (63 vs. 102 mg · h/L). The incidence of hypertension and hand-foot skin reactions significantly decreased over time. CONCLUSION: Sorafenib AUC(0-12) decreases over time, similarly to the incidence of hypertension and hand-foot skin reactions. Monitoring of sorafenib plasma concentrations may help to prevent acute severe toxicities and detect patients with suboptimal exposure at disease progression.

The plasma and cerebrospinal fluid pharmacokinetics of sorafenib after intravenous administration in non-human primates.

PURPOSE: Sorafenib is a small molecule inhibitor of multiple signaling kinases thought to contribute to the pathogenesis of many tumors including brain tumors. Clinical trials with sorafenib in primary and metastatic brain tumors are ongoing. We evaluated the plasma and cerebrospinal fluid (CSF) pharmacokinetics (PK) of sorafenib after an intravenous (IV) dose in a non-human primate (NHP) model. METHODS: 7.3 mg/kg of sorafenib free base equivalent solubilized in 20% cyclodextrin was administered IV over 1 h to three adult rhesus monkeys. Serial paired plasma and CSF samples were collected over 24 h. Sorafenib was quantified with a validated HPLC/tandem mass spectrometry assay. PK parameters were estimated using non-compartmental methods. CSF penetration was calculated from the AUC(CSF) : AUC(plasma). RESULTS: Peak plasma concentrations after IV dosing ranged from 3.4 to 7.6 µg/mL. The mean ± standard deviation (SD) area under the plasma concentration from 0 to 24 h was 28 ± 4.3 µg • h/mL, which is comparable to the exposure observed in humans at recommended doses. The mean ± SD clearance was 1.7 ± 0.5 mL/min/kg. The peak CSF concentrations ranged from 0.00045 to 0.00058 µg/mL. The mean ± SD area under the CSF concentration from 0 to 24h was 0.0048 ± 0.0016 µg•h/mL. The mean CSF penetration of sorafenib was 0.02% and 3.4% after correcting for plasma protein binding. CONCLUSION: Sorafenib is well tolerated in NHP and measurable in CSF after an IV dose. The CSF penetration of sorafenib is limited relative to total and free drug exposure in plasma.

Differences in the pharmacokinetics of 4-amino-3-chlorophenyl hydrogen sulfate, a metabolite of resatorvid, in rats and dogs.

The pharmacokinetics of 4-amino-3-chlorophenyl hydrogen sulfate, M-III of resatorvid, in rats and dogs were investigated using radiolabeled M-III ([(14)C]M-III). The elimination half-life of (14)C in the plasma of rats was approximately 1/30 of that of dogs after intravenous dosing of [(14)C]M-III at 0.5 mg/kg to rats and dogs. The in vitro and in vivo plasma protein binding ratios of M-III were relatively high and were the same in both species. The intrinsic clearance (CL(int)) of M-III in rats was much higher than the glomerular filtration rate in rats. Furthermore, the concentration of [(14)C]M-III in the kidney of rats was much higher than that in the plasma. On the contrary, in dogs, the concentration of [(14)C]M-III in the kidney was very much lower than that in the plasma. These results indicated that M-III was effectively taken up into the kidney and was excreted into the urine in rats; however, in dogs, ineffective renal uptake of M-III was presumed. When [(14)C]M-III and probenecid were simultaneously and continually infused intravenously to rats, the CL(int) of M-III decreased with increasing plasma concentrations of probenecid, indicating that kidney uptake of M-III in rats was inhibited by probenecid. It was also thought that uptake by the organic anion transport system(s) in the basolateral membrane is involved in the renal uptake of M-III in rats. The pharmacokinetic differences of M-III between rats and dogs are considered to be mainly caused by the difference in the urinary excretion via the renal distribution processes.

Preclincial testing of sorafenib and RAD001 in the Nf(flox/flox) ;DhhCre mouse model of plexiform neurofibroma using magnetic resonance imaging.

BACKGROUND: Neurofibromatosis type 1 (NF1) is an inherited disease predisposing affected patients to variable numbers of benign neurofibromas. To date there are no effective chemotherapeutic drugs available for this slow growing tumor. Molecularly targeted agents that aim to slow neurofibroma growth are being tested in clinical trials. So preclinical models for testing potential therapies are urgently needed to prioritize drugs for clinical trials of neurofibromas. PROCEDURE: We used magnetic resonance imaging (MRI) to monitor neurofibroma development in the Nf1(flox/flox) ;DhhCre mouse model of GEM grade I neurofibroma. Based on studies implicating mTOR and Raf signaling in NF1 mutant cells, we tested the therapeutic effect of RAD001 and Sorafenib in this model. Mice were scanned to establish growth rate followed by 8 weeks of drug treatment, then re-imaged after the last dose of drug treatment. Tumor volumes were determined by volumetric measurement. RESULTS: We found that rate of tumor growth varied among mice, as it does in human patients. RAD001 inhibited its predicted target pS6K, yet there was no significant decrease in the tumor volume in RAD001 treated mice compared to the vehicle control group. Sorafenib inhibited cyclinD1 expression and cell proliferation in tumors, and volumetric measurements identified significant decreases in tumor volume in some mice. CONCLUSION: The data demonstrate that volumetric MRI analysis can be used to monitor the therapeutic effect in the preclinical neurofibroma drug screening, and suggest that Sorafenib might have clinical activity in some neurofibromas.

Phase I trial of sorafenib in combination with interferon-alpha in Japanese patients with unresectable or metastatic renal cell carcinoma.

BACKGROUND: We investigated the safety, pharmacokinetics, tumor response, and immunological parameters of sorafenib plus interferon α-2b [corrected] (IFN) in Japanese patients with advanced RCC. PATIENTS AND METHODS: After 2 weeks of IFN-alone treatment, eligible patients received 28-day cycles of continuous sorafenib 200 mg (Cohort 1) or 400 mg (Cohorts 2 and 3) twice daily combined with intramuscular IFN 6 (Cohorts 1 and 2) or 9 (Cohort 3) million international units (MIU) three times a week. RESULTS: A total of 18 patients received at least one dose of sorafenib plus IFN. Five patients had dose-limiting toxicities (DLTs). The most common DLT was fatigue, experienced in four DLT patients. All 18 patients experienced at least one treatment-emergent adverse event (AE). The most common treatment-emergent AEs included fatigue, fever, platelets, leukocytes, hemoglobin, weight loss and anorexia. Five patients had confirmed partial response and 11 had stable disease, a response rate of 27.8%. IFN had no relevant impact on the pharmacokinetics of sorafenib. CONCLUSIONS: Sorafenib administered in combination with IFN was well tolerated, with promising results in efficacy. Continuous sorafenib 400 mg twice daily in combination with IFN 6 MIU three times a week is recommended in Japanese patients with advanced RCC.

A new rapid and sensitive LC-MS assay for the determination of sorafenib in plasma: application to a patient undergoing hemodialysis.

A simple liquid chromatography-mass spectrometry method was developed and validated for quantification of sorafenib (Nexavar) in human plasma. After a solid-phase extraction procedure, the separation was performed within 2 minutes using an isocratic flow of a mobile phase consisting of formic acid/acetonitrile applied on a C18 analytical column. The analyte was detected by mass spectrometry in the single-ion monitoring mode. The method was validated according to the recommendations of the US Food and Drug Administration. The method was linear (r² > 0.99) between 10 and 10,000 ng/mL. The lower limits of detection and quantification were 5 and 10 ng/mL, respectively. Within-day and between-day imprecisions were less than 10.4%, and inaccuracy did not exceed 8.7%. The mean extraction recovery was 92.2%. The method also provided satisfactory results in terms of time stability and dilution integrity. Sorafenib plasma concentrations of the studied patient ranged between 1831 and 3459 ng/mL. This new technique is rapid, sensitive, and was applied to the determination of sorafenib plasma concentrations in a patient undergoing hemodialysis. Our results indicate that sorafenib is not cleared from plasma by hemodialysis, although analysis should be delayed after dialysis to avoid erratic fluctuations.

Functional and clinical evidence of the influence of sorafenib binding to albumin on sorafenib disposition in adult cancer patients.

PURPOSE: Sorafenib, an oral multitargeted tyrosine kinase inhibitor, is highly bound to plasma proteins (>99.5%). Little is known about the influence of variations in sorafenib protein binding on its disposition. The aims of this study were to characterize in vitro sorafenib binding properties to albumin using the quenching fluorescence method and investigate the influence of albuminemia and bilirubinemia on sorafenib disposition in 54 adult cancer patients. RESULTS: In vitro estimate of sorafenib dissociation constant (Kd) for albumin was 0.22 µM [CI95 0.20-0.23]. In physiological conditions, sorafenib unbound fraction would increase 1.7-fold as albuminemia decreased from 45 g/L (680 µM) to 30 g/L (453 µM). In presence of bilirubin, apparent Kd of sorafenib was ~1.5-fold greater for bilirubin/albumin molar ratio of 1:4. In clinical settings, median sorafenib clearance (CL) was 1.42 L/h (0.75-2.13 L/h). In univariate analysis, sex, body mass index, and albuminemia were associated with CL (p = 0.04, 0.048, and 0.008, respectively). In multivariate analysis, albuminemia (p = 0.0036) was the single parameter independently associated with CL. CONCLUSION: These findings highlight the major influence of albuminemia on sorafenib clearance and its disposition in cancer patients.

Clinical results and pharmacokinetics of sorafenib in chronic hemodialysis patients with metastatic renal cell carcinoma in a single center.

OBJECTIVE: We investigated the safety and feasibility of sorafenib in patients with end-stage renal disease undergoing hemodialysis by examining the influence of pharmacokinetic parameters to their benefit and also the occurrence of drug-related adverse events of sorafenib. METHODS: Ten patients with metastatic renal cell carcinoma undergoing hemodialysis received sorafenib. Initial dose was 200 mg once daily, and the dose was increased up to the maintenance dose of 200 mg twice daily. The pharmacokinetic study was performed after a steady state was reached with 200 mg twice daily in six patients. RESULTS: Complete response occurred in one patient, partial response in three, stable disease in four and progressive disease in two. Median progression-free survival was 6.3 months. Serious adverse events were found in nine patients, including a Grade 5 subarachnoid hemorrhage and a Grade 4 cerebellar hemorrhage. In the pharmacokinetic study, the geometric mean of maximum concentration and area under the curve from 0 to 10 h of plasma concentration were similar on the day of hemodialysis and the day off hemodialysis. These data were lower than those from Japanese people with healthy kidneys and normal kidney function. There was no association between objective response or the occurrence of serious adverse events and pharmacokinetic parameters. CONCLUSIONS: Treatment with sorafenib of patients with metastatic renal cell carcinoma undergoing hemodialysis appears to be feasible, but we express some concern about the higher incidence of serious adverse events even with the reduced dose. However, clinical efficacy was not compromised.

(2S,4S)-4-Fluoro-1-{[(2-hydroxy-1,1-dimethylethyl)amino]acetyl}-pyrrolidine-2-carbonitrile monobenzenesulfonate (TS-021) is a selective and reversible dipeptidyl peptidase IV inhibitor.

The incretin hormone glucagon-like peptide-1 (GLP-1) has significant roles in the regulation of postprandial glucose metabolism, and the active form of GLP-1 is rapidly degraded by dipeptidyl peptidase (DPP)-IV. Therefore, DPP-IV inhibition is a promising approach for the treatment of type 2 diabetes. In the present study, we investigated the character of a DPP-IV inhibitor, TS-021, (2S, 4S)-4-fluoro-1-{[(2-hydroxy-1,1-dimethylethyl)amino]acetyl}-pyrrolidine-2-carbonitrile monobenzenesulfonate both in vitro and in vivo. TS-021 inhibits DPP-IV activity in human plasma with an IC(50) value of 5.34nM. In kinetics experiments, TS-021 had a relatively higher dissociation rate constant, with a k(off) value of 1.09×10(-3)s, despite exhibiting a potent human plasma DPP-IV inhibition activity with a K(i) value of 4.96nM. TS-021 exhibited significant inhibition selectivity against DPP-8 (>600 fold), DPP-9 (>1200 fold) and other peptidases examined (>15,000 fold). In normal rats, dogs and monkeys, a single oral dose of TS-021 exhibited favorable pharmacokinetic profiles. In Zucker fatty (fa/fa) rats, a rat model of obesity and impaired glucose tolerance, the oral administration of TS-021 resulted in the suppression of plasma DPP-IV activity and an increase in the active form of GLP-1. Furthermore, TS-021 exhibited a significant improvement in glucose tolerance by increasing the plasma insulin level during oral glucose tolerance tests at doses of 0.02-0.5mg/kg. These results suggest that TS-021 is a selective and reversible dipeptidyl peptidase IV inhibitor and has excellent characteristics as an oral anti-diabetic agent for postprandial hyperglycemia in patients with impaired glucose tolerance or type 2 diabetes.

Pneumatosis intestinalis associated with treatment of cancer patients with the vascular growth factor receptor tyrosine kinase inhibitors sorafenib and sunitinib.

Recently, pneumatosis intestinalis has been described in patients receiving bevacizumab, a monoclonal antibody to VEGF-A. Pneumatosis intestinalis is a condition characterized by subserosal and submucosal gas-filled cysts in the gastrointestinal tract. We report on pneumatosis intestinalis in patients receiving oral anti-VEGF agents. Patients shared the following characteristics: long-term (> 4 months) exposure to anti-VEGF agents, lack of other factors predisposing to pneumatosis intestinalis, and lack of recent surgical intervention. Taken together, these observations suggest that pneumatosis intestinalis is a probable class-effect of anti-VEGF agents.

Comparison of different tumor response criteria in patients with hepatocellular carcinoma after systemic therapy with the multikinase inhibitor sorafenib.

RATIONALE AND OBJECTIVES: The aim of this study was to compare tumor changes in patients with hepatocellular carcinoma receiving sorafenib using evaluation criteria of the American Association for the Study of Liver Diseases (AASLD) and the European Association for the Study of the Liver (EASL) as opposed to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. MATERIALS AND METHODS: Twenty-five patients with inoperable hepatocellular carcinoma receiving oral sorafenib underwent magnetic resonance imaging at baseline and follow-up every 8 weeks (range, 2-19 weeks; mean, 7.6 weeks). Data were evaluated retrospectively. Survey time until progression ranged from 5 to 102 weeks (mean, 25.6 weeks), with a total of 54 target lesions being monitored. Additionally, evaluation of serum α-fetoprotein was performed at follow-up. RESULTS: The best response at follow-up using RECIST resulted in rates of 4% objective response (complete remission or partial remission), 24% (progressive disease), and 72% (stable disease). In contrast, AASLD and EASL criteria identified objective responses in 28% and 48%. Twenty percent of all patients classified as having progressive disease by RECIST were identified as having "pseudo"-progression due to extensive necrosis. Eleven percent of patients classified as having stable disease by RECIST were disclosed as essentially progressive. AASLD area and AASLD diameter disclosed 36% and 40% of patients as having partial remission, respectively, whereas EASL criteria discovered only 24%. There was no significant correlation between serum α-fetoprotein progression and AASLD, EASL, or RECIST evaluation criteria. CONCLUSIONS: Response monitoring via functional criteria such as AASLD or EASL criteria is likely to more accurately reflect vital tumor burden in hepatocellular carcinoma compared to RECIST.

High-performance liquid chromatographic method for the determination of sorafenib in human serum and peritoneal fluid.

PURPOSE: Sorafenib is recommended for therapy of advanced hepatocellular carcinoma and renal cell carcinoma. Preclinical data indicate a relation between dose and antitumor efficacy. In clinical trials, adverse events improve after dose reduction suggesting a dose-dependent toxicity. Given dose has a direct impact on the drug serum concentration, but the latter also can be influenced by multiple factors, including interaction and metabolisation. To enable the investigation of concentration-related effects, an easy and sensitive assay for sorafenib drug monitoring is essential. METHODS: A high-performance liquid chromatography (HPLC) analysis involving an extraction with diethyl ether followed by separation on a Pinnacle™ DB C18 column and quantitation by UV absorbance at 260 nm was established. Sorafenib concentrations in samples of serum and peritoneal fluid have been determined. RESULTS: The assay was validated for serum samples and is linear over the concentration range of 100-5,000 ng/ml with a determination coefficient of >0.999. The limit of detection is 0.25 ng/ml. The intra- and inter-day coefficients of variation were below 3.03%. Sorafenib recovery in spiked probes of peritoneal fluid was above 85%. Sorafenib concentrations in 44 serum samples and 14 probes of peritoneal fluid have been determined with a mean of 3,328 and 1,380 ng/ml, respectively (standard deviation 2,267 and 659 ng/ml). CONCLUSIONS: A sensitive and selective HPLC method for the determination of sorafenib in human serum was developed and also verified for peritoneal fluid. This method provides a useful tool for pharmacokinetic investigations as well as for therapeutic drug monitoring of sorafenib.

Pharmacokinetic results of a phase I trial of sorafenib in combination with dacarbazine in patients with advanced solid tumors.

PURPOSE: Sorafenib, a multikinase inhibitor of Raf and several growth factor receptors, is under investigation in combination with dacarbazine, a commonly used chemotherapeutic agent for the treatment of many cancers. The current phase I study investigates the effects of sorafenib on the pharmacokinetic (PK) profile of dacarbazine and its metabolite 5-amino-imidazole-4-carboxamide (AIC). (AIC is formed in amounts equimolar to the active alkylating moiety, methane diazohydroxide, which is undetectable by known validated assays.) METHODS: Patients with advanced solid tumors received intravenous dacarbazine 1,000 mg/m(2) on day 1 of a 21-day cycle to evaluate the PK of dacarbazine alone. Sorafenib 400 mg was administered twice daily continuously starting at day 2 of cycle 1. The PK of dacarbazine in the presence of sorafenib was assessed on day 1 of cycle 2. Sorafenib PK was also assessed at steady state. RESULTS: PK data were available for 15 of 23 patients. With concomitant administration of sorafenib, the mean AUC and C (max) values of dacarbazine were reduced by 23 and 16%, respectively. Mean AUC and C (max) values of AIC were increased by 41 and 45%, respectively, with individual increases of up to 106 and 136%, respectively. The apparent terminal half-lives of the two compounds were not significantly influenced by sorafenib. Based on coefficients of variation, the AUC and C (max) values for sorafenib and its three metabolites were highly variable with dacarbazine coadministration. CONCLUSIONS: Concomitant administration of sorafenib and dacarbazine as described above may result in decreased dacarbazine exposure but increased AIC exposure.

Quantitation of sorafenib and its active metabolite sorafenib N-oxide in human plasma by liquid chromatography-tandem mass spectrometry.

A simple and rapid method with high performance liquid chromatography/tandem mass spectrometry is described for the quantitation of the kinase inhibitor sorafenib and its active metabolite sorafenib N-oxide in human plasma. A protein precipitation extraction procedure was applied to 50 µL of plasma. Chromatographic separation of the two analytes, and the internal standard [(2)H(3)(13)C]-sorafenib, was achieved on a C(18) analytical column and isocratic flow at 0.3 mL/min for 4 min. Mean within-run and between-run precision for all analytes were <6.9% and accuracy was <5.3%. Calibration curves were linear over the concentration range of 50-10,000 ng/mL for sorafenib and 10-2500 ng/mL for sorafenib N-oxide. This method allows a specific, sensitive, and reliable determination of the kinase inhibitor sorafenib and its active metabolite sorafenib N-oxide in human plasma in a single analytical run.