A rapid and sensitive method for determination of sorafenib in human plasma using a liquid chromatography/tandem mass spectrometry assay

Determination of Gemcitabine and Sorafenib in Spiked Human Plasma Using Multivariate Model Update Chemometric Methods

BACKGROUND

Gemcitabine (GEM), a pyrimidine nucleoside, has been used as a first-line treatment in non-small-cell lung cancer (NSCLC). Sorafenib (SOR), a nonselective multi-kinase inhibitor, is used as a chemotherapeutic agent in different types of cancers including NSCLC in preclinical studies. Co-administration of GEM and SOR was found to be effective and well-tolerated in the treatment of NSCLC.

OBJECTIVE

The aim of the present work is to determine the studied drugs in spiked human plasma simultaneously through resolving the overlapping spectra and removing the interference of the plasma matrix.

METHOD

Two updated chemometric models were developed using UV absorbance of the drugs, which named principal component regression (PCR) and partial least-squares (PLS) for determination of GEM and SOR in the ranges of 5-25 and 2-22 µg/mL, respectively.

RESULTS

Validation of the two updated models has been achieved in accordance with US Food and Drug Administration (FDA) guidelines, and the results were satisfactory. The two methods had the advantages of high predictive ability of the studied drugs with high precision and accuracy. Moreover, there was no significant difference obtained when statistical comparison was done between the developed and reported methods, showing good validity of the suggested methods.

CONCLUSIONS

The two updated models have the advantages of being rapid, accurate, sensitive, and cost-effective for the determination of GEM and SOR in quality control laboratories without any need for initial separation procedures.

HIGHLIGHTS

Two updated chemometric methods, PCR and PLS, were developed for the estimation of GEM and SOR in spiked human plasma using their UV absorbance data.

FDA-Validated Ecofriendly Chromatographic Methods for Simultaneous Determination of Gemcitabine and Sorafenib: Applications to Pharmacokinetics

Combination therapy of gemcitabine and sorafenib is synergistically effective and well tolerated in patients with non-small cell lung cancer (NSCLC). In this study, the pharmacokinetic parameters of both gemcitabine and sorafenib were estimated after intra-peritoneal administration in rats using novel, green and sensitive RP-HPLC and TLC-densitometric methods where sildenafil used as an internal standard. Firstly, the developed RP-HPLC method achieved on ZORBAX Eclipse Plus C18 (4.6 mm × 150 mm, 5 μm) using a mixture of methanol: 40 mM ammonium acetate solution. On the other hand, the developed TLC-densitometric method was achieved on TLC plates using a developing system of methanol: ethyl acetate (3: 7, by volume) and scanning wave length at 260 nm. Additionally, the developed methods were validated according to FDA guidelines. Moreover, the developed methods were successfully used to study the pharmacokinetic parameters of both gemcitabine and sorafenib after administration of each drug alone and co-administration in rats. The results presented that drug–drug interaction between drugs happened when administrated together affecting the pharmacokinetic parameters of each other. The proposed methods, being ecofriendly, accurate, and sensitive, may become the corner stone for further clinical studies of the studied drugs determinations applied on humans.

LC-MS/MS monitoring of the colorectal carcinoma cellular uptake and entrapment of sorafenib and its N-oxide active metabolite

Sorafenib (SOR) is a multikinase inhibitor with a mild activity against colorectal cancer cells due to multi-drug resistance mechanisms. Potentiated SOR activity was expected upon combination with some ginger derived compounds due to their interference with intracellular drug metabolism. Studying such combination necessitates the development of a sensitive validated LC-MS/MS method for the determination of intra and extracellular concentration of SOR and its N-oxide metabolite (SNX) in colorectal cancer cells. SOR, SNX and the internal standard (diclofenac sodium) were efficiently separated on Eclipse plus C18 column (3.0 ×150 mm, 5 µm) using isocratic elution with acetonitrile and 0.01 M ammonium formate aqueous solution containing 0.1% formic acid (69:31, v/v). Sample pretreatment using solid phase extraction was optimized and the mean percent recoveries were more than 97.01% for both analytes. Detection was conducted at positive ion multiple reaction monitoring (MRM) mode and the monitored mass transitions were 465.2 → 252.2 for SOR and 481.1 → 286.0 for SNX. The method was linear over the range 0.25 - 200.00 ng/mL (r² ≥ 0.9992) for SOR and 0.10 - 125.00 ng/mL (r² ≥ 0.9990) for SNX in both intra and extracellular matrices. The lower limits of quantification (LLOQ) were 0.25 and 0.10 ng/mL for SOR and SNX, respectively. Accuracies were within 94.25 - 109.45% and precision CV values did not exceed 7.63%. The method was able to monitor the cellular uptake and entrapment of both analytes and to prove the positive effect of the ginger derived compounds on SOR activity.

Sorafenib

Sorafenib (BAY-43-9006), marketed by Bayer as Nexavar® (USA), is anticancer drug approved by US-FDA for the treatment of unresectable hepatocellular carcinoma and advanced renal cell carcinoma. Sorafenib inhibited tumor growth and angiogenesis through targeting both the RAF/MEK/ERK pathway and receptor tyrosine kinases. This study presents a comprehensive profile of sorafenib, including detailed nomenclature, formula, elemental analysis, methods of preparation, physico-chemical characteristics, and methods of analysis (including spectroscopic, electrochemical, and chromatographic methods of analysis). Spectroscopic and spectrometric analyses include UV/vis spectroscopy, vibrational spectroscopy, nuclear magnetic resonance spectrometry ((1)H and (13)C NMR), and mass spectrometry. Chromatographic methods of analyses include thin layer chromatography and high-performance liquid chromatography. Only few stability indicating methods were found for quantification of sorafenib after exposing tablet dosage form to various stress conditions such as hydrolysis, oxidation, thermal stress, photo and UV light. However, none of these described methods were made to separate and quantify the degradation products. Pharmacology studies including pharmacodynamics, mechanism of action, pharmacokinetics and drug-drug interactions were also presented. An appropriate table and figures were attached to each of the above mentioned sections along with total of 55 references.

Pharmacokinetic interaction study of novel combination of palbociclib and sorafenib for hepatocellular carcinoma in SD rats

Hepatocellular carcinoma (HCC) is a fatal oncogenic disorder with few therapeutic options. Novel therapeutic strategy with combination of a selective CDK4/6 inhibitor palbociclib (PAL) with a tyrosine kinase inhibitor (TKI) sorafenib (SOR) is reported to impair tumour growth and significantly increased survival in various preclinical models of HCC. In the current work a sensitive and rapid UHPLC-QTOF-MS method was established for the concurrent quantification of PAL and SOR in rat plasma using ibrutinib as internal standard (IS). Chromatographic separation was carried out on an Agilent Poroshell EC C18 (50 mm × 3 mm, 2.7 μm) using gradient mobile phase consisting of 0.1% formic acid and acetonitrile. Flow rate of 0. 45 mL/min with a run time of 5 min was used for separation. A simple sample preparation approach of protein precipitation was used in the current study. The mass spectrometric analysis of selective ions at [M + H]⁺m/z 448.2455 for PAL, m/z 465.0936 for SOR and m/z 441.2034 for IS was monitored with extracted ion chromatography. The LC-MS method meets the regulatory bio-analytical guidelines, exhibited good sensitivity and linearity over the range of 1.0-2000.0 ng/mL for PAL and SOR. The pharmacokinetic parameters of PAL remained unchanged when SOR was co-administered with PAL. The study pointed out that the co-intake of PAL with SOR resulted in a slight increment of C_max (11.21%) and AUC (7.95%) levels of SOR when co-administered with PAL when compared to individual oral intake in SD rats. The current method provides a modern rapid and sensitive tool for pharmacokinetic studies of PAL and SOR in a pre-clinical set up.

In-vivo relation between plasma concentration of sorafenib and its safety in Chinese patients with metastatic renal cell carcinoma: a single-center clinical study

This single-center, observational study analyzed the association between plasma concentration of sorafenib and its safety and efficacy in Chinese patients with metastatic renal cell carcinoma (mRCC). Adult patients with RCC (n = 94), treated with sorafenib were enrolled between January 2014 and January 2015. Sorafenib plasma concentrations were measured by liquid chromatography-tandem mass spectrometry. Safety and efficacy variables were evaluated using National Cancer Institute-Common Toxicity Criteria for Adverse Events and Response Evaluation Criteria in Solid Tumors criteria. Association of plasma concentration with safety and efficacy was analyzed. The steady state plasma concentration of sorafenib after 2 weeks of treatment ranged from 881 to 12,526 ng/mL. Major adverse reactions (ADRs) included diarrhea (76.5%), hand-foot syndrome (HFS; 68.99%) and fatigue (55.32%). Significant association was reported between plasma concentration and all the ADRs except rash. At 6 weeks, complete response (CR), partial response (PR), stable disease (SD) and progressive disease (PD) was reported in 3.1%, 13.82%, 52.2% and 13.82% patients, respectively. Objective response and disease control rates were 17.02% and 69.14%. Plasma concentration of sorafenib was >10,000 ng/mL in patients with severe ADRs, which decreased with reduction in dose or discontinuation of treatment. After 21.2 weeks follow-up, median progression free survival was 12.3 months. CR, PR, SD and PD were reported in 1%, 46%, 33% and 19% patients. In conclusion, plasma concentration of sorafenib was associated with its safety and efficacy in Chinese patients with mRCC.

Sorafenib cardiotoxicity increases mortality after myocardial infarction

RATIONALE

Sorafenib is an effective treatment for renal cell carcinoma, but recent clinical reports have documented its cardiotoxicity through an unknown mechanism.

OBJECTIVE

Determining the mechanism of sorafenib-mediated cardiotoxicity.

METHODS AND RESULTS

Mice treated with sorafenib or vehicle for 3 weeks underwent induced myocardial infarction (MI) after 1 week of treatment. Sorafenib markedly decreased 2-week survival relative to vehicle-treated controls, but echocardiography at 1 and 2 weeks post MI detected no differences in cardiac function. Sorafenib-treated hearts had significantly smaller diastolic and systolic volumes and reduced heart weights. High doses of sorafenib induced necrotic death of isolated myocytes in vitro, but lower doses did not induce myocyte death or affect inotropy. Histological analysis documented increased myocyte cross-sectional area despite smaller heart sizes after sorafenib treatment, further suggesting myocyte loss. Sorafenib caused apoptotic cell death of cardiac- and bone-derived c-kit+ stem cells in vitro and decreased the number of BrdU+ (5-bromo-2'-deoxyuridine+) myocytes detected at the infarct border zone in fixed tissues. Sorafenib had no effect on infarct size, fibrosis, or post-MI neovascularization. When sorafenib-treated animals received metoprolol treatment post MI, the sorafenib-induced increase in post-MI mortality was eliminated, cardiac function was improved, and myocyte loss was ameliorated.

CONCLUSIONS

Sorafenib cardiotoxicity results from myocyte necrosis rather than from any direct effect on myocyte function. Surviving myocytes undergo pathological hypertrophy. Inhibition of c-kit+ stem cell proliferation by inducing apoptosis exacerbates damage by decreasing endogenous cardiac repair. In the setting of MI, which also causes large-scale cell loss, sorafenib cardiotoxicity dramatically increases mortality.

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.

Phase I study of sorafenib in combination with docetaxel and prednisone in chemo-naïve patients with metastatic castration-resistant prostate cancer

PURPOSE

We performed a dose-escalation study to investigate the safety of sorafenib in combination with docetaxel and prednisone in chemo-naïve patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Six patients were included per dose level. Following docetaxel infusion on day 1 (75 mg/m(2)/q3 weeks), sorafenib was administered at 200 mg BID on days 2-19 (dose level 1), at 200 mg BID on days 1-21 (dose level 2), at 400 mg BID on days 2-19 (dose level 3), at 400 mg BID on days 1-21 (dose level 4). Maximal tolerated dose (MTD) was exceeded if ≥2 patients experienced dose-limiting toxicities (DLT) during cycle 1. The recommended phase 2 dose for sorafenib was defined as one dose level below MTD. If MTD was not reached, the highest feasible dose would be selected to treat an expanded cohort to confirm safety.

RESULTS

Two DLTs were observed during sorafenib dose-escalation consisting of grade 4 febrile neutropenia (dose level 2) and grade 3 hand-foot syndrome (HFS) (dose level 3). Our pharmacokinetic results showed an increased exposure to docetaxel across all dose levels during sorafenib comedication. The main grade ≥3 toxicities were neutropenia (35 %), HFS (27 %), and febrile neutropenia (19 %). The prostate-specific antigen (PSA) response rate was 74 %. Median overall survival was 25.2 months.

CONCLUSION

Three-weekly docetaxel and prednisone could be combined with sorafenib at 400 mg BID on days 1-21 without reaching MTD. However, we observed a pharmacokinetic interaction between sorafenib and docetaxel, associated with significant toxicities, raising concerns about the safety of this combination in mCRPC.

Phase I pharmacokinetic and pharmacodynamic study of cetuximab, irinotecan and sorafenib in advanced colorectal cancer

Background This phase Ib study was designed to determine the maximum tolerated doses (MTD) and dose limiting toxicities (DLTs) of irinotecan and cetuximab with sorafenib. Secondary objectives included characterizing the pharmacokinetics and pharmacodynamics and evaluating preliminary antitumor activity in patients with advanced colorectal cancer (CRC). Methods Patients with metastatic, pretreated CRC were treated at five dose levels. Results Eighteen patients were recruited with median age 56.5 years. In the first five patients treated, 2 irinotecan related DLTs were observed. With reduced dose intensity irinotecan, there were no further DLTs. The most common toxicities were diarrhea, nausea/vomiting, fatigue, anorexia and rash. DLTs included neutropenia and thrombocytopenia. Two patients had partial responses (one with a KRAS mutation) and 8 had stable disease (8-36 weeks). The median progression free survival (PFS) and overall survival (OS) were 2.5 and 4.7 months respectively. Pharmacokinetic analyses suggest sorafenib and metabolite exposure correlate with OS and DLTs. Conclusions The recommended phase II dose (RP2D) is irinotecan 100 mg/m(2) i.v. days 1, 8; cetuximab 400 mg/m(2) i.v. days 1 and 250 mg/m(2) i.v. weekly; and sorafenib 400 mg orally twice daily in advanced, pretreated CRC. The combination resulted in a modest response rate.

A phase I multi-institutional study of systemic sorafenib in conjunction with regional melphalan for in-transit melanoma of the extremity

BACKGROUND

Isolated limb infusion with melphalan (ILI-M) corrected for ideal body weight (IBW) is a well-tolerated treatment for patients with in-transit extremity melanoma with an approximate 29 % complete response (CR) rate. Sorafenib, a multi-kinase inhibitor, has been shown to augment tumor response to chemotherapy in preclinical studies.

METHODS

A multi-institutional, dose-escalation, phase I study was performed to evaluate the safety and antitumor activity of sorafenib in combination with ILI-M. Patients with AJCC stage IIIB/IIIC/IV melanoma were treated with sorafenib starting at 400 mg daily for 7 days before and 7 days after ILI-M corrected for IBW. Toxicity, drug pharmacokinetics, and tumor protein expression changes were measured and correlated with clinical response at 3 months.

RESULTS

A total of 20 patients were enrolled at two institutions. The maximum tolerated dose (MTD) of sorafenib in combination with ILI-M was 400 mg. Four dose-limiting toxicities occurred, including soft tissue ulcerations and compartment syndrome. There were three CRs (15 %) and four partial responses (20 %). Of patients with the Braf mutation, 83 % (n = 6) progressed compared with only 33 % without (n = 12). Short-term sorafenib treatment did alter protein expression as measured with reverse phase protein array (RPPA) analysis, but did not inhibit protein expression in the MAP kinase pathway. Sorafenib did not alter melphalan pharmacokinetics.

CONCLUSION

This trial defined the MTD of systemically administered sorafenib in combination with ILI-M. Although some responses were seen, the addition of sorafenib to ILI-M did not appear to augment the effects of melphalan but did increase regional toxicity.

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.

Activity of the multikinase inhibitor sorafenib in combination with cytarabine in acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a genetically heterogeneous cancer that frequently exhibits aberrant kinase signaling. We investigated a treatment strategy combining sorafenib, a multikinase inhibitor with limited single-agent activity in AML, and cytarabine, a key component of AML chemotherapy.

METHODS

Using 10 human AML cell lines, we determined the effects of sorafenib (10 μM) on antileukemic activity by measuring cell viability, proliferation, ERK1/2 signaling, and apoptosis. We also investigated the effects of sorafenib treatment on the accumulation of cytarabine and phosphorylated metabolites in vitro. A human equivalent dose of sorafenib in nontumor-bearing NOD-SCID-IL2Rγ(null) mice was determined by pharmacokinetic studies using high performance liquid chromatography with tandem mass spectrometric detection, and steady-state concentrations were estimated by the fit of a one-compartment pharmacokinetic model to concentration-time data. The antitumor activity of sorafenib alone (60 mg/kg) twice daily, cytarabine alone (6.25 mg/kg administered intraperitoneally), or sorafenib once or twice daily plus cytarabine was evaluated in NOD-SCID-IL2Rγ(null) mice bearing AML xenografts.

RESULTS

Sorafenib at 10 μM inhibited cell viability, proliferation and ERK1/2 signaling, and induced apoptosis in all cell lines studied. Sorafenib also increased the cellular accumulation of cytarabine and metabolites resulting in additive to synergistic antileukemic activity. A dose of 60 mg/kg in mice produced a human equivalent sorafenib steady-state plasma exposure of 10 μM. The more dose-intensive twice-daily sorafenib plus cytarabine (n = 15) statistically significantly prolonged median survival in an AML xenograft model compared with sorafenib once daily plus cytarabine (n = 12), cytarabine alone (n = 26), or controls (n = 27) (sorafenib twice daily plus cytarabine, median survival = 46 days; sorafenib once daily plus cytarabine, median survival = 40 days; cytarabine alone, median survival = 36 days; control, median survival = 19 days; P < .001 for combination twice daily vs all other treatments listed).

CONCLUSIONS

Sorafenib in combination with cytarabine resulted in strong anti-AML activity in vitro and in vivo. These results warrant clinical evaluation of sorafenib with cytarabine-based regimens in molecularly heterogeneous AML.

Two drug interaction studies of sirolimus in combination with sorafenib or sunitinib in patients with advanced malignancies

PURPOSE

Sirolimus is the prototypical mTOR inhibitor. Sorafenib and sunitinib are small molecule inhibitors of multiple kinases including VEGF receptor (VEGFR) kinases. These agents have different mechanisms of action, providing a strong rationale for combination.

EXPERIMENTAL DESIGN

Patients with advanced cancer were assigned to receive either sirolimus or the VEGFR inhibitor alone for a 2-week lead-in period, followed by combination therapy. The primary end point of each trial was to determine whether a drug interaction exists between sirolimus and either sorafenib or sunitinib, as defined by a difference in C(max) for each drug alone compared with its C(max) during combination therapy.

RESULTS

The sorafenib and sunitinib trials enrolled 34 and 23 patients, respectively. There were no clinically significant differences in C(max) for any of the drugs alone compared with the C(max) during combination therapy. Toxicity profiles were similar to those expected for each drug alone. One patient with adrenal cortical cancer had a partial response to sirolimus and sunitnib.

CONCLUSIONS

Sirolimus can be safely combined with sorafenib or sunitinib. Our trial design is feasible and informative in screening for potential drug-drug interactions, using a relatively small number of patients and limited pharmacokinetic sampling.

Sequential therapy with JX-594, a targeted oncolytic poxvirus, followed by sorafenib in hepatocellular carcinoma: preclinical and clinical demonstration of combination efficacy

JX-594 is a targeted and granulocyte-macrophage colony stimulating factor (GM-CSF) expressing oncolytic poxvirus designed to selectively replicate in and destroy cancer cells through viral oncolysis and tumor-specific immunity. In a phase 1 trial, JX-594 injection into hepatocellular carcinoma (HCC) was well-tolerated and associated with viral replication, decreased tumor perfusion, and tumor necrosis. We hypothesized that JX-594 and sorafenib, a small molecule inhibitor of B-raf and vascular endothelial growth factor receptor (VEGFR) approved for HCC, would have clinical benefit in combination given their demonstrated efficacy in HCC patients and their complementary mechanisms-of-action. HCC cell lines were uniformly sensitive to JX-594. Anti-raf kinase effects of concurrent sorafenib inhibited JX-594 replication in vitro, whereas sequential therapy was superior to either agent alone in murine tumor models. We therefore explored pilot safety and efficacy of JX-594 followed by sorafenib in three HCC patients. In all three patients, sequential treatment was (i) well-tolerated, (ii) associated with significantly decreased tumor perfusion, and (iii) associated with objective tumor responses (Choi criteria; up to 100% necrosis). HCC historical control patients on sorafenib alone at the same institutions had no objective tumor responses (0 of 15). Treatment of HCC with JX-594 followed by sorafenib has antitumoral activity, and JX-594 may sensitize tumors to subsequent therapy with VEGF/VEGFR inhibitors.

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.

A pharmacodynamic study of sorafenib in patients with relapsed and refractory acute leukemias

We report the results of a phase I dose escalation trial of the multikinase inhibitor sorafenib in relapsed and refractory acute leukemia patients using an intermittent dosing regimen. Fifteen patients with advanced leukemia (12 with acute myeloid leukemia, 2 with acute lymphoblastic leukemia, 1 with biphenotypic) and a median age of 63 (range 37-85) years were enrolled and treated on a dose escalation trial. Toxicities >or=grade 3 were present in 55% of cycles and the maximum tolerated dose (MTD) was determined to be 400 mg b.i.d. x 21 days in a 28-day cycle. Plasma inhibitory assays of kinase targets extracellular signal-regulated kinase (ERK) and FLT3-internal tandem duplication (ITD) showed excellent target inhibition, with FLT3-ITD silencing occurring below the MTD. The N-oxide metabolite of sorafenib seemed to be a more potent inhibitor of FLT3-ITD than the parent compound. Despite marked ex vivo FLT-3 ITD inhibition, no patients met the criteria for complete or partial response in this monotherapy study. Out of 15 patients, 11 experienced stable disease as best response. Although sorafenib showed only modest clinical activity as a single agent in this heavily treated population, robust inhibition of FLT3 and ERK suggests that there may be a potential important role in combination therapies.

Safety, efficacy, pharmacokinetics, and pharmacodynamics of the combination of sorafenib and tanespimycin

PURPOSE

Heat shock protein (Hsp) 90 inhibition affects the Raf kinase signaling pathway and could enhance antitumor effects of sorafenib, a Raf kinase inhibitor. The combination of sorafenib and tanespimycin [17-allyl-amino-geldanamycin (17-AAG); NSC 330507/KOS-953] was evaluated in a phase I trial with the primary objective of defining a phase II dose.

PATIENTS AND METHODS

The dose cohorts consisted of fixed continuous oral dosing of 400 mg sorafenib twice daily, starting at 14 days before tanespimycin, which was administered intravenously at escalating doses (starting at 300 mg/m,(2) with 50 mg/m(2) increments), on days 1, 8, and 15 in a 28-day cycle. Toxicity was assessed weekly, and response was evaluated every two cycles.

RESULTS

Twenty-seven toxicity-evaluable patients were enrolled and treated at four dose levels. Predominant primary malignancies were renal cancer (12), melanoma (6), and colorectal cancer (4). Dose-limiting toxicities of grade 4 transaminitis and grade 3 hand-foot syndrome in one patient each were observed at 450 mg/m(2) of tanespimycin. One hundred fourteen cycles were administered with a median of four cycles (range 1-17 cycles). Plasma concentrations of sorafenib and metabolites reached steady state after 7 days. Tanespimycin did not alter sorafenib concentrations. Pharmacodynamics showed a decrease in Hsp90 levels and induction of Hsp70. Clinical efficacy was observed in 9 of 12 renal cancer patients and 4 of 6 melanoma patients

CONCLUSIONS

Recommended phase II doses of this combination are 400 mg sorafenib twice daily and 400 mg/m(2) tanespimycin on days 1, 8, and 15, every 28 days. Clinical and pharmacodynamic activity was observed in kidney cancer and melanoma.

Simple and selective method for the determination of various tyrosine kinase inhibitors used in the clinical setting by liquid chromatography tandem mass spectrometry

A fast, sensitive, universal and accurate method for the determination of four different tyrosine kinase inhibitors from biological material was developed using LC-MS/MS techniques. Utilizing a simple protein precipitation with acetonitrile a 20 microl sample volume of biological matrixes can be extracted at 4 degrees C with minimal effort. After centrifugation the sample extract is introduced directly onto the LC-MS/MS system without further clean-up and assayed across a linear range of 1-4000 ng/ml. Chromatography was performed using a Dionex Ultimate 3000 with a Phenomenex prodigy ODS3 (2.0 mm x 100 mm, 3 microm) column and eluted at 200 microl/min with a tertiary mobile phase consisting of 20mM ammonium acetate:acetonitrile:methanol (2.5:6.7:8.3%). Injection volume varied from 0.1 microl to 1 microl depending on the concentration of the drug observed. Samples were observed to be stable for a maximum of 48 h after extraction when kept at 4 degrees C. Detection was performed using a turbo-spray ionization source and mass spectrometric positive multi-reaction-monitoring-mode (+MRM) for Gefitinib (447.1 m/z; 127.9 m/z), Erlotinib (393.9 m/z; 278.2 m/z), Sunitinib (399.1 m/z; 283.1 m/z) and Sorafenib (465.0 m/z; 251.9 m/z) at an ion voltage of +3500 V. The accuracy, precision and limit-of-quantification (LOQ) from cell culture medium were as follows: Gefitinib: 100.2+/-3.8%, 11.2 nM; Erlotinib: 101.6+/-3.7%, 12.7 nM; Sunitinib: 100.8+/-4.3%, 12.6 nM; Sorafenib: 93.9+/-3.0%, 10.8 nM, respectively. This was reproducible for plasma, whole blood, and serum. The method was observed to be linear between the LOQ and 4000 ng/ml for each analyte. Effectiveness of the method is illustrated with the analysis of samples from a cellular accumulation investigation and from determination of steady state concentrations in clinically treated patients.

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

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

Interaction of the multikinase inhibitors sorafenib and sunitinib with solute carriers and ATP-binding cassette transporters

PURPOSE

To compare side-by-side the uptake of sorafenib and sunitinib in vitro by human uptake solute carriers of the SLC22A and SLCO families, the transport by and inhibition of efflux ATP-binding cassette (ABC) transporters, and the role of ABCB1 in the plasma pharmacokinetics and brain penetration of these agents.

EXPERIMENTAL DESIGN

Uptake of [(3)H]sorafenib or [(3)H]sunitinib was assessed in Xenopus laevis oocytes or mammalian cells transfected with cDNAs coding for human OATP1A2, OATP1B1, OATP1B3, OCT1, OAT2, OAT3, OCTN1, or OCTN2. Efflux and inhibition experiments were conducted in cells transfected with human ABCB1, ABCG2, ABCC2, or ABCC4. In vivo pharmacokinetic studies were done in knockout mice lacking Abcb1-type transporters.

RESULTS

Intracellular uptake was not appreciably affected by any of the studied solute carriers and was minute relative to the respective prototypical substrates. Sorafenib and sunitinib showed concentration-dependent (1 and 10 micromol/L), low to moderate affinity for ABCB1 but were not affected by the other ABC transporters. Both agents inhibited all tested ABC transporters. The absence of Abcb1 had no affect on plasma pharmacokinetics, but brain penetration was moderately increased by 1.9- and 2.9-fold for sorafenib and sunitinib, respectively, in knockout animals versus controls.

CONCLUSIONS

Unlike other tyrosine kinase inhibitors, sorafenib and sunitinib do not appear to rely on active transport to enter the cell nor are they high-affinity substrates for ABC efflux transporters. Based on these characteristics, these two drugs may be less susceptible to transporter-mediated alterations in systemic exposure and transporter-related resistance mechanisms.

Phase I and pharmacokinetic study of sorafenib in patients with hepatic or renal dysfunction: CALGB 60301

PURPOSE

We sought to characterize the pharmacokinetics (PK) and determine a tolerable dose of oral sorafenib in patients with hepatic or renal dysfunction.

PATIENTS AND METHODS

Patients were assigned to one of nine cohorts: cohort 1, bilirubin < or = upper limit of normal (ULN) and AST < or = ULN and creatinine clearance (CC) > or = 60 mL/min; cohort 2, bilirubin more than ULN but < or = 1.5x ULN and/or AST more than ULN; cohort 3, CC between 40 and 59 mL/min; cohort 4, bilirubin more than 1.5x ULN to < or = 3x ULN (any AST); cohort 5, CC between 20 and 39 mL/min; cohort 6, bilirubin more than 3x ULN to 10x ULN (any AST); cohort 7, CC less than 20 mL/min; cohort 8, albumin less than 2.5 mg/dL (any bilirubin/AST); and cohort 9, hemodialysis. Sorafenib was administered as a 400-mg dose on day 1 for PK, and continuous daily dosing started on day 8.

RESULTS

Of 150 registered patients, 138 patients were treated. With the exception of cohorts 6 and 7, at least 12 patients per cohort were assessable, and the dose level with prospectively defined dose-limiting toxicity in less than one third of patients by day 29 was considered tolerable. No significant associations between the sorafenib PK and cohort were found.

CONCLUSION

We recommend the following empiric sorafenib starting doses by cohort: cohort 1, 400 mg twice a day; cohort 2, 400 mg twice a day; cohort 3, 400 mg twice a day; cohort 4, 200 mg twice a day; cohort 5, 200 mg twice a day; cohort 6, not even 200 mg every third day tolerable; cohort 7, not defined; cohort 8, 200 mg each day; and cohort 9, 200 mg each day.

Incorporating FLT3 inhibitors into acute myeloid leukemia treatment regimens

FMS-Like-Tyrosine kinase-3 (FLT3) mutations are found in about 30% of cases of acute myeloid leukemia and confer an increased relapse rate and reduced overall survival. Targeting of this tyrosine kinase by direction inhibition is the focus of both preclinical and clinical research in AML. Several molecules in clinical development inhibit FLT3 with varying degrees of specificity. Preclinical models suggest that these compounds enhance the cytotoxicity of conventional chemotherapeutics against FLT3 mutant leukemia cells. The pharmacodynamic interactions between FLT3 inhibitors and chemotherapy appear to be sequence dependent. When the FLT3 inhibitor is used prior to chemotherapy, antagonism is displayed, while if FLT3 inhibition is instituted after to exposure to chemotherapy, synergistic cytotoxicity is seen. The combination of FLT3 inhibitors with chemotherapy is also complicated by potential pharmacokinetic obstacles, such as plasma protein binding and p-glycoprotein interactions. Ongoing and future studies are aimed at incorporating FLT3 inhibitors into conventional induction and consolidation therapy specifically for patients with FLT3 mutant AML.

Development of a rapid and sensitive LC-MS/MS assay for the determination of sorafenib in human plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of sorafenib in human plasma. Sample pretreatment involved simple protein precipitation by the addition of 0.5 mL acetonitrile, containing internal standard ([2H3, 15N] sorafenib), to 50 microL of plasma sample volume. Separation was achieved on a Waters SymmetryShield RP8 (2.1 mm x 50 mm, 3.5 microm) column at room temperature using an isocratic elution method with acetonitrile/0.1% formic acid in water: 65/35 (v/v) at a flow rate of 0.25 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 464.9 --> 252.0 (sorafenib) and m/z 469.0 --> 259.0 (internal standard). Calibration curves were linear in the concentration range of 5-2000 ng/mL. The accuracy and precision values, calculated from three different sets of quality control samples analyzed in quintuplicate on six different days, ranged from 92.86% to 99.88% and from 1.19% to 4.53%, respectively.