A phase I, dose escalation, pharmacodynamic, pharmacokinetic, and food-effect study of α2 integrin inhibitor E7820 in patients with advanced solid tumors

Introduction E7820 is an orally administered sulfonamide that inhibits alfa-2-integrin mRNA expression. Pre-clinically E7820 showed tumor anti-angiogenic effects in various tumor cell lines and xenograft mouse models. Human daily dosing of 100 mg QD had previously been shown to be safe and tolerable. Methods The study consisted of two parts: Part A (food effect) and Part B (determination of maximum tolerated dose (MTD) for bi-daily (BID) dosing). E7820 dosing started at 50 mg BID with planned escalation to 60, 80 and 100 mg BID every 28 days. Results Fifteen patients were enrolled in Part A and 26 in Part B. The most frequent adverse events of all grades were constipation, diarrhea, nausea, and fatigue while anemia, neutropenia, and fatigue were most frequent grade ≥3 toxicities. At dose-level 60 mg BID, two patients experienced dose-limiting toxicities (grade 3 neutropenic sepsis and grade 4 neutropenia). Therefore the recommended dose (RD) was 50 mg BID. Food had no effect on E7820 exposure. E7820 exposure following twice daily administration was dose-proportional. Expression of platelet integrin-α2 measured as a response biomarker in Part B, generally decreased by a median 7.7 % from baseline following treatment with 50 mg BID E7820. Reduction was most pronounced within 1-week post treatment. The median duration of treatment was median 54, range 20-111 days. The best overall response in any treatment group was stable disease (SD): 23.1 % in Part A (100 mg QD); at the RD 66.7 % (12 of 18 patients) and 40 % in the 60 mg BID group in Part B.

CONCLUSIONS

Food had no effect on E7820 exposure. A dose of 50 mg BID was considered the MTD. Treatment with E7820 is safe and tolerable with 2/3 of patients (66.7 %) at MTD having SD as their best response.

Disposition of loratadine in healthy volunteers

The absorption, metabolism and excretion of carbon-14-labeled loratadine (LOR, SCH 29851, Claritin) administered orally to healthy male volunteers were evaluated. Following a single oral 10-mg dose of [(14)C]LOR ( approximately 102 microCi), concentrations of LOR and desloratadine (DL; a pharmacologically active descarboethoxy metabolite of LOR) were determined in plasma. Metabolites in plasma, urine and feces were characterized using a liquid chromatography-mass spectrometry system (LC-MS) connected in line with a flow scintillation analyzer (FSA). Maximum plasma LOR and DL concentrations were achieved at 1.5 h and 1.6 h, respectively; thus, LOR was rapidly absorbed but also rapidly metabolized as indicated by these similar t(max) values. Metabolite profiles of plasma showed that LOR was extensively metabolized via descarboethoxylation, oxidation and glucuronidation. Major circulating metabolites included 3-hydroxy-desloratadine glucuonide (3-OH-DL-Glu), dihydroxy-DL-glucuronides, and several metabolites resulting from descarboethoxylation and oxidation of the piperidine ring. LOR was completely metabolized by 6 h post-dose. LOR-derived radiocarbon was excreted almost equally in the urine (41%) and feces (43%). About 13% of the dose was eliminated in the urine as 3-OH-DL-Glu. DL accounted for less than 2% of the dose recovered in the urine and only trace amounts of LOR were detected. 3-OH-DL was the major fecal metabolite ( approximately 17% of the dose). The combined amount of 5- and 6-hydroxy-DL contributed to an additional 10.7% of the dose in feces. Approximately 5.4% and 2.7% of the dose were excreted in the feces as unchanged drug and DL, respectively.

Disposition and pharmacokinetics of temozolomide in rat

1. Temozolomide, an imidazotetrazine derivative, is a cytotoxic alkylating agent of broad-spectrum antitumour activity. The absorption, metabolism, distribution and excretion of temozolomide have been investigated in male and female Sprague-Dawley and Long-Evans rats following single oral or intravenous dose administration of 200 mg m(-2) non-radiolabelled or (14)C-radiolabelled temozolomide. The distribution of (14)C-temozolomide was also evaluated by whole-body autoradiography in male Sprague-Dawley rats. Plasma concentrations of temozolomide and its active metabolite 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC) were determined by high-performance liquid chromatography (HPLC) with ultraviolet detection. Plasma, urine and faeces were profiled by HPLC with radiochemical detection. 2. Temozolomide was rapidly and extensively (>90%) absorbed and widely distributed in tissues. The distribution pattern of radioactivity was gender independent. Penetration into the brain following oral or intravenous administration was 35-39% based on the brain/plasma AUC ratio. 3. Following intravenous or oral administration, temozolomide was primarily eliminated renally (75-85% of the dose) as either unchanged drug, a carboxylic acid analogue, AIC (a degradation product) and a highly polar unidentified peak. Biliary excretion was minimal (1.4-1.6%). The pharmacokinetics (oral versus intravenous) were similar and gender independent. The absolute oral availability was 96-100%. Temozolomide was rapidly eliminated (t(1/2) = 1.2 h) and converted to MTIC. 4. Systemic exposure to MTIC was about 2% that of temozolomide. Overall, the disposition of temozolomide in rats was similar to that observed in humans.

Disposition of desloratadine in healthy volunteers

The absorption, metabolism and excretion of desloratadine (DL, Clarinex) were characterized in six healthy male volunteers. Subjects received a single oral 10-mg dose of [(14)C]DL ( approximately 104 microCi). Blood, urine and feces were collected over 240 h. DL was well absorbed; drug-derived radioactivity was excreted in both urine (41%) and feces (47%). With the exception of a single subject, DL was extensively metabolized; the major biotransformation pathway consisted of hydroxylation at the 3 position of the pyridine ring and subsequent glucuronidation (3-OH-DL-glucuronide or M13). In five of the six subjects, DL was slowly eliminated (mean t((1/2)) = 19.5 h) and persisted in the plasma for 48-120 h post-dose. This is in contrast to a t((1/2)) of approximately 110 h and quantifiable plasma DL concentrations for the entire 240-h sampling period in one subject, who was identified phenotypically as a poor metabolizer of DL. This subject also exhibited correspondingly lower amounts of M13 in urine and 3-OH-DL (M40) in feces. Disposition of DL in this subject was characterized by slow absorption, slow metabolism and prolonged elimination. Further clinical studies confirmed the lack of safety issues associated with polymorphism of DL metabolism (Prenner et al. 2006, Expert Opinion on Drug Safety, 5: 211-223).

Assessment of a multiple-dose drug interaction between ezetimibe, a novel selective cholesterol absorption inhibitor and gemfibrozil

OBJECTIVE

Ezetimibe is a novel lipid-lowering drug that prevents intestinal absorption of dietary and biliary cholesterol leading to significant reduction in total-C, LDL-C, Apo B, and TG and increases in HDL-C in patients with hypercholesterolemia. Gemfibrozil, a fibric acid derivative, is an effective lipid-modulating agent that increases serum high-density lipoprotein cholesterol and decreases serum TG. The objective of this study was to evaluate the potential for a pharmacokinetic (PK) interaction between ezetimibe and gemfibrozil.

METHODS

This was a randomized, open-label, 3-way crossover, multiple-dose study in 12 healthy adult male volunteers. All subjects received the following 3 treatments orally for 7 days: ezetimibe 10 mg once daily, gemfibrozil 600 mg every 12 hours, and ezetimibe 10 mg once daily plus gemfibrozil 600 mg every 12 hours. A washout period of > or = 7 days separated the 3 treatments. In each treatment, blood samples were collected on day 7 to assess the steady-state PK of ezetimibe and gemfibrozil. The oral bioavailability of ezetimibe coadministered with gemfibrozil relative to each drug administered alone was evaluated with an analysis-of-variance model.

RESULTS

Ezetimibe was rapidly absorbed and extensively conjugated to its glucuronide metabolite. Ezetimibe did not alter the bioavailability (based on AUC) of gemfibrozil. The mean AUC0-12 of gemfibrozil was 74.7 and 74.1 microg h/ml with and without ezetimibe coadministration, respectively (log-transformed geometric mean ratio (GMR) = 99.2; 90% confidence interval (CI) = 92 - 107%). Conversely, gemfibrozil significantly (p < 0.05) increased the plasma concentrations of ezetimibe and total ezetimibe (i.e. ezetimibe plus ezetimibe-glucuronide). Exposure to ezetimibe and total ezetimibe was increased approximately 1.4-fold and 1.7-fold, respectively (CI = 109 - 173% for ezetimibe and 142 - 190% for total ezetimibe), however, this increase was not considered to be clinically relevant. Ezetimibe and gemfibrozil administered alone or concomitantly for 7 days was well tolerated.

CONCLUSIONS

The coadministration of ezetimibe and gemfibrozil in patients is unlikely to cause a clinically significant drug interaction. The coadministration of these agents is a promising approach for patients with mixed dyslipidemia. Additional clinical studies are warranted.

Marked inactivation of O6-alkylguanine-DNA alkyltransferase activity with protracted temozolomide schedules

Temozolomide, an oral DNA methylator that inactivates the DNA repair enzyme O(6)-alkylguanine-DNA alkyltransferase (AGAT), has demonstrated anticancer activity on protracted schedules. Protracted schedules may lead to an 'autoenhancement' of temozolomide's inherent cytotoxic potential by cumulative reduction of the cell's capacity for AGAT-mediated DNA repair and resistance. This study was undertaken to characterise AGAT inactivation and regeneration in the peripheral blood mononuclear cells (PBMCs) of patients treated on two protracted temozolomide schedules. O(6)-alkyl guanine-DNA alkyltransferase activity was measured in the PBMCs of patients treated on two phase I protracted temozolomide studies. Patients were treated daily for either 7 days every 2 weeks (Schedule A) or 21 days every 4 weeks (Schedule B). The effects of various temozolomide doses (75-175 mg m(-2)), treatment duration (7-21 days), and temozolomide plasma levels on AGAT inactivation and regeneration, as well as the relation between AGAT inactivation and toxicity, were studied. O(6)-alkyl guanine-DNA alkyltransferase activity in PBMCs was measured serially in 52 patients. Marked inactivation of AGAT occurred following 7 days of temozolomide treatment, with mean AGAT activity decreasing by 72% (P<0.0001). Similarly, mean AGAT activity decreased by 63 and 73% after 14 and 21 days of treatment, respectively (P<0.001 for both comparisons). O(6)-alkyl guanine-DNA alkyltransferase inactivation was greater after 7 days of treatment with higher doses of temozolomide than lower doses and remained markedly reduced 7 days post-treatment. However, AGAT inactivation following temozolomide treatment for 14 and 21 days was similar at all doses. On the continuous 21-day schedule, AGAT inactivation was significantly greater in patients who experienced severe thrombocytopenia than those who did not (90.3+/-5.5 vs 72.5+/-16.1%, P<0.045). In conclusion, protracted administration of temozolomide, even at relatively low daily doses, leads to significant and prolonged depletion of AGAT activity, which may enhance the antitumour activity of the agent.

Bioavailability of dextromethorphan (as dextrorphan) from sustained release formulations in the presence of guaifenesin in human volunteers

A multiple dose bioavailability study with six healthy male human volunteers was conducted. The bioavailability of an experimental sustained release tablet containing dextromethorphan hydrobromide (DXP-HBr), was compared with a marketed sustained release DXP-HBr suspension in a three-way crossover study. Plasma samples, collected serially after oral drug administration, were analysed for the major metabolite of dextromethorphan (DXP), dextrorphan (DX), using a specific HPLC method with fluorescence detection. The bioavailability parameters; area under the concentration-time curve (AUC), maximum plasma concentration (Cmax), and time to peak (Tmax), were obtained from the plasma concentration-time data. Additionally, pharmacokinetic parameters such as mean residence time (MRT), accumulation factor (R), fluctuation index (Fi), total body clearance (Cl), and the average concentration (C) were estimated by using model independent kinetics approach. Analysis of variance of the data revealed that the presence of guaifenesin in the test formulation does not appear to have a statistically significant (p > 0.05) effect on the bioavailability of dextromethorphan as dextrorphan. The relative bioavailability of the tablet dosage form with respect to the suspension was found to be 113% on Day 1 and 110% on Day 6.

Pharmacokinetics and biodistribution of a nucleotide-based thrombin inhibitor in rats

PURPOSE

To characterize the pharmacokinetic and tissue distribution profiles of a nucleotide-based thrombin inhibitor (GS522, phosphodiester oligonucleotide, GGTTGGTGTGGTTGG) following intravenous administration to rats.

METHODS

Pharmacokinetic study: 10 mg/kg, 20 mg/kg, 30 mg/kg (6 animals/dose) were administered to rats by rapid injection into the femoral vein. Blood samples were collected over a 45 minute period. Plasma concentrations of GS522 were determined using capillary gel electrophoresis with laser-induced fluorescence detection. Biodistribution Study: 10 mg/kg (400 microl, 31.46 microCi/ml) of 3H-GS522 was administered to rats by rapid injection into the femoral vein. The animals were sacrificed by decapitation at 1, 5, 10, 30, 60, 360 minutes post-dose (3 rats/point). Brain, blood, duodenum, eyes, heart, kidney, liver, lungs, muscle, pancreas, skin, spleen and vein samples were collected, processed and quantitated using liquid scintillation counting.

RESULTS

The pharmacokinetic profile declines in multiexponential manner, exhibiting extremely fast distribution and elimination (t1/2 = 7.6-9.0 min, Cl = 22.0-28.0 ml/min, V = 83.9-132.4 ml/kg). GS522 follows linear pharmacokinetics, with the area under the curve being proportional to the dose (Rsq = 0.9744). Highest radioactivity levels were detected in kidney, liver and blood (39.7, 15.7 and 15.3% dose/ respective organ). Less than 1% of the dose was detected in the heart, spleen and lungs, and >0.3% of the dose was found in the brain and eyes. The oligonucleotide associated radioactivity was uniformly distributed between the brain regions (left and right lobe and cerebellum). Six hours following the dose administration a statistically significant increase (p < 0.05) in radioactivity levels was observed in the brain, eyes, skin, liver, pancreas and vein.

CONCLUSIONS

The pharmacokinetic and biodistribution profiles of GS522 following intravenous administration to rats at three doses were characterized. The oligonucleotide associated radioactivity was widely distributed in tissues. The amount of radioactivity sharply decreased with time in most tissues. Kidney, liver and muscle were the main sites of accumulation. The oligonucleotide associated radioactivity did not cross the blood brain barrier to an appreciable extent. In addition, a statistically significant increase (p < 0.05) in the radioactivity levels observed in select tissues suggested a re-uptake mechanism for intact oligonucleotide or its degradation products.

Quantitative determination of short single-stranded oligonucleotides from blood plasma using capillary electrophoresis with laser-induced fluorescence

The quantitative determination of short (< 20 bases) single-standed (ss-) oligonucleotides (oligos) from blood plasma using capillary gel electrophoresis with laser-induced fluorescence is reported. Oligos were derivatized on column after equilibration of the column with a 1:150 dilution of OliGreen dye. The resulting fluorescent complex was detected and measured with an argon ion laser detector using excitation/emission wavelengths of 488/520 nm, respectively. The method involves precipitation of plasma proteins with phenol-chloroform followed by dilution and drop analysis in nanopure water for 30 min on a 0.025 microns cellulose acetate membrane. This treatment lowers the ionic strength of the plasma sample resulting in a significant improvement of the electrokinetic loading (5 kV, 10 s) of the analyte. Optimal electrophoretic separation was achieved at 13 kV using 4 M urea in a 10% polyacrylamide gel filled capillary, 100 mM Tris borate as the running buffer, and a temperature of 30 degrees C. Oligos were determined in the presence of p(dT)20/40 as internal standard. The observed migration times were 6.35 and 6.60 min for the oligo and internal standard, respectively. The migration times and fluorescent yield of the complex were temperature dependent. Increasing the separation temperature (20 to 60 degrees C) resulted in a decrease in the migration time and fluorescent yield of the oligonucleotide-dye complex. A linear response over a broad concentration range (0.02-1.5 micrograms/mL, R2 = 0.997) was obtained. The limit of quantitation was set at 20 ng/mL (CV% = 11.3%). The intraday variability was 9.44, 5.28, and 9.2% for 190, 760, and 1520 ng/mL plasma samples, respectively. Data are presented to illustrate the practicality of the method for the pharmacokinetic evaluation of GS522 and potential metabolites in plasma after intravenous administration to rats.

Determination of single-stranded oligodeoxynucleotides by capillary gel electrophoresis with laser induced fluorescence and on column derivatization

OliGreen reagent, a new dye for complexing of oligonucleotides of low molecular mass was successfully utilized for their quantitative analysis using on column derivatization and capillary gel electrophoresis with laser induced fluorescence. Method optimization for the precise, accurate and reproducible quantitation of low-molecular-mass oligonucleotides from aqueous matrices is described.

Novel methods of microparticulate production: application to drug delivery

The purpose of this paper is to present two novel techniques, electrostatic spraying and oscillating capillary nebulization, for the production of microspheres of uniform reproducible particle size distribution. Cholesterol was chosen as a model compound to show the utility of both procedures. The processes for each method are described, illustrating their simplicity and absence of an external detrimental phase. Scanning electron microscopy was used to assess morphology while laser diffraction analysis was used to determine particle size. Electrostatic spraying of cholesterol yielded particles of round shape, smooth surface, and uniform distribution of particle size ranging between 10-30 microns and 100-300 microns. Oscillating capillary nebulization of cholesterol molten at 170 degrees C produced microspheres with an average diameter ranging from 22 microns to 30 microns when gas back pressures controlling the vibration of the capillary ranged from 60 to 90 psi. Electrostatic spraying and oscillating capillary nebulization are one-step procedures that result in high production yields. Both techniques are easy to set up and afford both production speed and reproducibility. The absence of a detrimental external phase makes them particularly appealing for the microencapsulation of proteins and polynucleotides in polymers with low melting temperatures. The feasibility of production of cholesterol microspheres can be extrapolated to the production of excipient-free microspheres of steroids.

Simultaneous determination of dextrorphan and guaifenesin in human plasma by liquid chromatography with fluorescence detection

A sensitive liquid chromatographic (LC) method was developed and validated for the simultaneous determination of dextrorphan and guaifenesin in human plasma using fluorescence detection. Dextrorphan and guaifenesin were extracted from plasma by a liquid-liquid extraction procedure using chloroform containing laudanosine as the internal standard. A cyano column (15 cm x 46 mm i.d., Spherisorb 5-CN) and a mobile phase containing acetonitrile-triethylamine-distilled water (10:1:89, v/v/v) (pH 6) were used. The concentration-response relationship for dextrorphan was found to be linear over a concentration range of 23-515 ng ml-1 with a lower limit of detection of 20 ng ml-1; the accuracy of the method would fall (95% confidence limit) within 9.53% and 11.07% of the true value for the inter-and intra-day, respectively; the inter- and intra-day precision, as measured by RSD, ranged from 1.88% to 30.07% (mean 2.28%) and from 4.69% to 7.51% (mean 5.67%) over the dynamic concentration range of the method (33-326 ng ml-1). The concentration-response relationship for guaifenesin was found to be linear over a concentration range of 181-8136 ng ml-1 with a lower detection limit of 30 ng ml-1; the accuracy of the method would fall (95% confidence limit) within 9.78% and 8.04% of the true value for the inter- and intra-day, respectively; the inter- and intra-day precision, as measured by the RSD, ranged from 2.55 to 6.07% (mean 3.90%) and from 3.12 to 3.90% (mean 3.52%) over the dynamic concentration range of the method (435-6430 ng ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)