Robert D. Arnold

Magnetic Nanoparticle-Based Hyperthermia for Head & Neck Cancer in Mouse Models

In this study, magnetic iron oxide nanoparticle induced hyperthermia is applied for treatment of head and neck cancer using a mouse xenograft model of human head and neck cancer (Tu212 cell line). A hyperthermia system for heating iron oxide nanoparticles was developed by using alternating magnetic fields. Both theoretical simulation and experimental studies were performed to verify the thermotherapy effect. Experimental results showed that the temperature of the tumor center has dramatically elevated from around the room temperature to about 40oC within the first 5-10 minutes. Pathological studies demonstrate epithelial tumor cell destruction associated with the hyperthermia treatment.

Pectin and charge modified pectin hydrogel beads as a colon-targeted drug delivery carrier.

The physical and chemical properties of commercial low methoxyl citrus pectins, CP 28 and CP 55, and a pectinmethylesterase (PME) charge modified citrus pectin (MP 38) were compared, and the differences in ability to encapsulate indomethacin in hydrogel beads was determined at 0.5 or 1.0% (w/v) indomethacin ratio, and 100, 200 or 300 mM CaCl(2) solution. In order to investigate the drug release characteristics, indomethacin loaded dried hydrogel beads were immersed in simulated gastric fluids (pH 1.2) for 2h, followed by immersing in simulated intestinal fluids (pH 7.4) for 3h. Pectin type was highly significant (p<0.0001) for encapsulation efficiency and in vitro release assay. Encapsulation efficiency was also highly affected (p<0.0001) by indomethacin ratio and CaCl(2) concentration. The accumulative release rate of indomethacin from pectin hydrogel bead was less than 15% in simulated gastro-intestinal fluids. MP 38 beads showed significantly higher entrapment efficiency and lower release rate than beads formed from CP 28 or CP 55. MP 38 hydrogel formulated with 300 mM CaCl(2) and 0.5% indomethacin ratio showed the highest entrapment efficiency. These studies suggest that charge modification of pectin improves encapsulation efficiency of drugs for colon targeted drug delivery system through oral administration.

Mechanistic population pharmacokinetics of total and unbound paclitaxel for a new nanodroplet formulation versus Taxol in cancer patients

PurposeOur objectives were (1) to compare the disposition and in vivo release of paclitaxel between a tocopherol-based Cremophor-free formulation (Tocosol Paclitaxel®) and Cremophor® EL-formulated paclitaxel (Taxol®) in human subjects, and (2) to develop a mechanistic model for unbound and total paclitaxel pharmacokinetics.MethodsA total of 35 patients (averagexa0±xa0SD age: 59xa0±13xa0years) with advanced non-hematological malignancies were studied in a randomized two-way crossover trial. Patients received 175xa0mg/m2 paclitaxel as 15xa0min (Tocosol Paclitaxel) or 3xa0h (Taxol) intravenous infusion in each study period. Paclitaxel concentrations were determined by LC–MS/MS in plasma ultrafiltrate and whole blood. NONMEM VI was used for population pharmacokinetics.ResultsA linear disposition model with three compartments for unbound paclitaxel and a one-compartment model for Cremophor were applied. Total clearance of unbound paclitaxel was 845xa0L/h (variability: 25% CV). The prolonged release with Tocosol Paclitaxel was explained by the limited solubility of unbound paclitaxel of 405xa0ng/mL (estimated) in plasma. The 15xa0min Tocosol Paclitaxel infusion yielded a mean time to 90% cumulative input of 1.14xa0±xa00.16xa0h. Tocosol Paclitaxel was estimated to release 9.8% of the dose directly into the deep peripheral compartment. The model accounted for the presence of drug-containing nanodroplets in blood.ConclusionsPopulation pharmacokinetic analysis indicated linear disposition and a potentially higher bioavailability of unbound paclitaxel following Tocosol Paclitaxel administration due to direct release at the target site. The prolonged release of Tocosol Paclitaxel supports 15xa0min paclitaxel infusions. This mechanistic model may be important for development of prolonged release formulations that distribute in and from the systemic circulation.

Secretory phospholipase A2 responsive liposomes

Secretory phospholipase A(2) (sPLA(2)) expression is increased in several cancers and has been shown to trigger release from some lipid carriers. This study used electrospray ionization mass spectrometry (ESI-MS) and release of 6-carboxyfluorescein (6-CF) to determine the effects of sPLA(2) on various liposome formulations. Different combinations of zwitterionic [1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine, 1,2-distearoyl-sn-glycero-3-phosphatidylcholine, and 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE)] and anionic [1,2-distearoyl-sn-glycero-3-phosphatidic acid, 1,2-distearoyl-sn-glycero-3-phosphatidylglycerol (DSPG), 1,2-distearoyl-sn-glycero-3-phosphatidylserine, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol) 2000 (DSPE-PEG)] phospholipids were examined. DSPG and DSPE were most susceptible to sPLA(2)-mediated degradation compared with other phospholipids. Increased 6-CF release was observed after inclusion of 10 mol % DSPE and anionic lipids into different liposome formulations. Group IIa sPLA(2)-mediated 6-CF release was less than Group III and relatively insensitive to cholesterol (Chol), whereas Chol reduced sPLA(2)-mediated release. Inclusion of DSPE-PEG increased sPLA(2)-mediated 6-CF release, whereas serum reduced lipid degradation and 6-CF release significantly. These data demonstrate that ESI-MS and 6-CF release were useful in determining the selectivity of sPLA(2) and release from liposomes, that differences in the activity of different sPLA(2) isoforms exist, and that DSPE-PEG enhanced sPLA(2)-mediated release of liposomal constituents. These findings will aid in the selection of lipids and optimization of the kinetics of drug release for the treatment of cancers and diseases of inflammation in which sPLA(2) expression is increased.

Multiple-pool cell lifespan models for neutropenia to assess the population pharmacodynamics of unbound paclitaxel from two formulations in cancer patients

PurposeOur objective was to build a mechanism-based pharmacodynamic model for the time course of neutropenia in cancer patients following paclitaxel treatment with a tocopherol-based Cremophor-free formulation (Tocosol Paclitaxel®) and Cremophor® EL-formulated paclitaxel (Taxol®).MethodsA randomized two-way crossover trial was performed with 35 adult patients who received 175xa0mg/m2 paclitaxel as either 15xa0min (Tocosol Paclitaxel) or 3xa0h (Taxol) intravenous infusions. Paclitaxel concentrations were measured by LC–MS/MS. NONMEM VI was used for population pharmacodynamics.ResultsThe cytotoxic effect on neutrophils was described by four mechanism-based models predicated on known properties of paclitaxel that used unbound concentrations in the central, deep peripheral or an intracellular compartment as forcing functions. Tocosol Paclitaxel was estimated to release 9.8% of the dose directly into the deep peripheral compartment (DPC). All models provided reasonable fitting of neutropenic effects. The model with the best predictive performance assumed that this dose fraction was released into 22.5% of the DPC which included the site of toxicity. The second-order cytotoxic rate constant was 0.00211xa0mL/ng per hour (variability: 52% CV). The relative exposure at the site of toxicity was 2.21xa0±xa00.41 times (averagexa0±xa0SD) larger for Tocosol Paclitaxel compared to Taxol. Lifespan was 11.0xa0days for progenitor cells, 1.95xa0days for maturating cells, and 4.38xa0days for neutrophils. Total drug exposure in blood explained half of the variance in nadir to baseline neutrophil count ratio.ConclusionsThe relative exposure of unbound paclitaxel at the site of toxicity was twice as large for Tocosol Paclitaxel compared to Taxol. The proposed mechanism-based models explained the extent and time course of neutropenia jointly for both formulations.

Effect of age on the pharmacokinetics of a single daily dose of gentamicin sulfate in healthy foals

REASONS FOR PERFORMING STUDYnTherapeutic drug monitoring in a small number of foals of various ages indicates that the standard adult dose of 6.6 mg/kg bwt q. 24 h for gentamicin is too low and a dose of 12 mg/kg bwt has been proposed. The pharmacokinetics of this dosage in foals and the ages at which this higher dose should be used have not previously been investigated.nnnOBJECTIVEnTo determine the effect of age on the pharmacokinetics of a single 12 mg/kg bwt i.v. dose of gentamicin in foals.nnnMETHODSnSix healthy foals were given a single i.v. dose of gentamicin at 1-3 days, 2, 4, 8 and 12 weeks of age. Plasma concentrations were measured using LC-MS/MS.nnnRESULTSnElimination half-life (mean ± s.d.) was significantly longer in 1-3-day-old foals (8.2 ± 2.0 h) than in foals 4 weeks of age (3.7 ± 1.5 h) or older. Volume of distribution was significantly higher in 1-3-day-old foals (0.75 ± 0.20 l/kg bwt) than in 8- (0.27 ± 0.10 l/kg bwt) or 12-week-old foals (0.29 ± 0.11 l/kg bwt). Concentrations of gentamicin 1 h after administration were significantly lower in 1-3-day-old foals (20.52 ± 2.07 μg/ml) than in all other age groups (>42.16 ± 17.57 μg/ml). Concentrations of gentamicin 24 h after administration were significantly higher in the 1-3-day-old foals (1.97 ± 0.90 μg/ml) than in all the other age groups (<0.85 ± 0.46 μg/ml).nnnCONCLUSIONSnThe pharmacokinetics of gentamicin change considerably in the first 2 weeks of life.nnnPOTENTIAL RELEVANCEnIntravenous administration of gentamicin at a dose of 12 mg/kg bwt q. 36 h would be required in foals less than 2 weeks of age. In foals 2 weeks of age or older, a lower dose of 6.6 mg/kg bwt given q. 24 h was predicted to be adequate.

The antioxidant phenylaminoethyl selenide reduces doxorubicin-induced cardiotoxicity in a xenograft model of human prostate cancer.

Anthracyclines are potent anticancer agents, but cardiotoxicity mediated by free radical generation limits their clinical use. This study evaluated the anticancer activity of phenyl-2-aminoethyl selenide (PAESe) and its potential to reduce doxorubicin (DOX)-induced cardiotoxicity. Growth inhibitory effects of PAESe with DOX, and vincristine, clinically used anticancer agents, and tert-butylhydroperoxide (TBHP), a known oxidant, on the growth of human prostate carcinoma (PC-3) cells was determined. PAESe (≤1μm) did not alter the growth of PC-3 cells, however, concomitant use of PAESe decreased the oxidative-mediated cytotoxicity of TBHP, but had limited effect on vincristine or DOX activity. Further, PAESe decreased the formation of intracellular reactive oxygen species from TBHP and DOX. The effect of PAESe on the activity of DOX was determined using a tumor (PC-3) xenograft model in mice. PAESe did not alter DOX antitumor activity and showed evidence of direct antitumor activity relative to controls. DOX treatment decreased mice body weight significantly, whereas concomitant administration of PAESe and DOX was similar to controls. Most importantly, PAESe decreased DOX-mediated infiltration of neutrophil and macrophages into the myocardium. These data suggest PAESe had in vivo antitumor activity and in combination with DOX decreased early signs of cardiotoxicity while preserving its antitumor activity.

The Efficacy of Intranasal Administration of Dexmedetomidine and Ketamine to Yellow-Bellied Sliders (Trachemys scripta scripta)

Abstract The purpose of this study was to evaluate the efficacy of dexmedetomidine and ketamine and reversal with atipamezole administered intranasally to Trachemys scripta scripta. Eight healthy adult turtles received 0.2 and 10 mg/kg of dexmedetomidine and ketamine, respectively. Heart rate, respiratory rate, temperature, and sedation (on a scale of 0–4) were measured. Blood was collected 45 min post induction for drug plasma levels from both the subcarapacial and tail veins, followed by intranasal atipamezole administration (0.5 mg/kg). The most frequent sedation scores (2 and 3) provided a level of sedation deep enough to perform a thorough physical exam and minor clinical procedures. All of the turtles became active in 18.9 ± 7 min after atipamezole administration. No adverse effects were observed and all measured cardiopulmonary parameters were within normal limits. Plasma levels of both dexmedetomidine and ketamine indicated adequate absorption and distribution with no difference in the levels obtained from either the subcarapacial or the tail venipuncture sites. A combination of dexmedetomidine–ketamine can be used intranasally to induce moderate to heavy sedation for physical examination, venipuncture, and other minor procedures in the yellow-bellied slider without adverse effects. In addition, the intranasal administration of atipamezole appears efficacious for reversal of dexmedetomidine. Intranasal administration of anesthetic agents holds promise for sedating and anesthetizing chelonians, which are often difficult to thoroughly examine and restrain for biological sample collection, both in the clinic and in the field.

Enhanced antitumor activity of low-dose continuous administration schedules of topotecan in prostate cancer

Purpose: The objective of this study was to determine the antitumor effects of alternate dosing schedules of topotecan in prostate cancer. Results: A concentration-dependent increase in cytotoxicity was observed in PC-3 and LNCaP cells after topotecan treatment using conventional and metronomic protocols. A significant increase in potency (2.4-18 fold, after 72 hr) was observed following metronomic dosing compared to conventional dosing administration in both cell lines. Metronomic dosing also increased the percentage of PC-3 cells in the G2/M, compared to control, but did not alter LNCaP cell cycle distribution. Metronomic dosing increased p21 protein expression in LNCaP and PC-3 cells compared to conventional dosing. The observed in vitro activity was confirmed using an in vivo model of human prostate cancer. Metronomic dosing and continuous infusion decreased tumor volume significantly (p < 0.05) compared to control and conventional topotecan treatment, but had no effect on tumor vascular staining. Methods: The cytotoxicity of topotecan after conventional or metronomic dosing was determined by examining cellular morphology, mitochondrial enzymatic activity (MTT), total cellular protein (SRB), annexin V and propidium iodine (PI) staining, cell cycle and western blot analysis in human prostate cancer cell lines (PC-3 and LNCaP) and the effects metronomic or continuous infusion on tumor growth in an in vivo tumor xenograft model. Conclusions: These data support the hypothesis that low-dose continuous administration of topotecan increases potency compared to conventional dosing in prostate cancer. These data also suggest the novel finding that the enhanced antitumor activity of topotecan following low-dose exposure correlates to alterations in cell cycle and increased p21 expression.

Pharmacokinetic evaluation of immediate- and extended-release formulations of levetiracetam in dogs

OBJECTIVEnTo compare the pharmacokinetics of various formulations of levetiracetam after oral administration of a single dose to healthy dogs.nnnANIMALSn6 neurologically normal mixed-breed dogs.nnnPROCEDURESnA crossover study design was used. Blood samples for serum harvest were collected from each dog before and at various points after oral administration of one 500-mg tablet of each of 2 generic extended-release (ER) formulations, 1 brand-name ER formulation, or 1 brand-name immediate-release (IR) formulation of levetiracetam. Serum samples were analyzed to determine pharmacokinetic properties of each formulation by means of ultra-high-performance liquid chromatography with tandem mass spectrometry.nnnRESULTSnNo dogs had clinically important adverse effects for any formulation of levetiracetam. All ER formulations had a significantly lower maximum serum drug concentration and longer time to achieve that concentration than did the IR formulation. Half-lives and elimination rate constants did not differ significantly among formulations. Values for area under the drug concentration-versus-time curve did not differ significantly between ER formulations and the IR formulation; however, 1 generic ER formulation had a significantly lower area under the curve than did other ER formulations.nnnCONCLUSIONS AND CLINICAL RELEVANCEnAll ER formulations of levetiracetam had similar pharmacokinetic properties in healthy dogs, with some exceptions. Studies will be needed to evaluate the clinical efficacy of the various formulations; however, findings suggested that twice-daily administration of ER formulations may be efficacious in the treatment of seizures in dogs.