Comparison of the pharmacokinetics of two formulations of hydroxyethyl starch in healthy horses.

A lower molecular weight and molar substitution formulation (130/0.4) of hydroxyethyl starch solution has been shown to have a more sustained effect on COP and similar hemodynamic effects as a higher molecular weight and molar substitution formulation (600/0.75) in healthy horses. In humans, these pharmacodynamic characteristics are coupled with more rapid clearance and decreased adverse coagulation effects and accumulation. The objective of this study was to determine and compare the pharmacokinetics of these two formulations in horses. Eight healthy horses were given a 10 mL/kg bolus of each formulation (600/0.75 and 130/0.4) of hydroxyethyl starch solution in a randomized crossover design. Blood was collected, and plasma was harvested for plasma levels over 24 h. Pharmacokinetic parameters for each horse were estimated from a noncompartmental analysis. Treatment with 600/0.75 resulted in a higher initial plasma concentration (C0 ), systemic half-life (t1/2 ), and overall drug exposure (AUC0-inf ) in addition to decreased elimination rate (ß), volume of distribution (Vd), and clearance (CL), compared to treatment with 130/0.4 (P < 0.001). The pharmacokinetic findings combined with previous pharmacodynamics findings suggest that 130/0.4 can provide similar benefits to 600/0.75 with a lower risk of accumulation in the circulation.

Nephrotoxicity of epigenetic inhibitors used for the treatment of cancer.

This study determined the anti-neoplastic activity and nephrotoxicity of epigenetic inhibitors in vitro. The therapeutic efficacy of epigenetic inhibitors was determined in human prostate cancer cells (PC-3 and LNCaP) using the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-Aza) and the histone deacetylase inhibitor trichostatin A (TSA). Cells were also treated with carbamazepine (CBZ), an anti-convulsant with histone deacetylase inhibitor-like properties. 5-Aza, TSA or CBZ alone did not decrease MTT staining in PC-3 or LNCaP cells after 48 h. In contrast, docetaxel, a frontline chemotherapeutic induced concentration-dependent decreases in MTT staining. Pretreatment with 5-Aza or TSA increased docetaxel-induced cytotoxicity in LNCaP cells, but not PC-3 cells. TSA pretreatment also increased cisplatin-induced toxicity in LNCaP cells. Carfilzomib (CFZ), a protease inhibitor approved for the treatment of multiple myeloma had minimal effect on LNCaP cell viability, but reduced MTT staining 50% in PC-3 cells compared to control, and pretreatment with 5-Aza further enhanced toxicity. Treatment of normal rat kidney (NRK) and human embryonic kidney 293 (HEK293) cells with the same concentrations of epigenetic inhibitors used in prostate cancer cells significantly decreased MTT staining in all cell lines after 48 h. Interestingly, we found that the toxicity of epigenetic inhibitors to kidney cells was dependent on both the compound and the stage of cell growth. The effect of 5-Aza and TSA on DNA methyltransferase and histone deacetylase activity, respectively, was confirmed by assessing the methylation and acetylation of the CDK inhibitor p21. Collectively, these data show that combinatorial treatment with epigenetic inhibitors alters the efficacy of chemotherapeutics in cancer cells in a compound- and cell-specific manner; however, this treatment also has the potential to induce nephrotoxic cell injury.

Pharmacokinetics, pulmonary disposition and tolerability of liposomal gentamicin and free gentamicin in foals.

REASONS FOR PERFORMING THE STUDY: Although gentamicin is highly active against Rhodococcus equi in vitro, its clinical efficacy has been limited presumably due to poor cellular uptake. Encapsulation of drugs in liposomes enhances their cellular uptake. OBJECTIVES: To compare the disposition of liposomal gentamicin (LG) and free gentamicin (FG) in the plasma, pulmonary epithelial lining fluid and bronchoalveolar cells of healthy foals after i.v. administration or by nebulisation, and to assess the tolerability of the drug after repeated i.v. dosing. STUDY DESIGN: Experimental study. METHODS: Eight healthy foals received a single i.v. or nebulised dose (6.6 mg/kg bwt) of LG or FG in a balanced Latin square design, with a 14-day washout period between treatments. Subsequently, 12 healthy foals were given either LG or FG at 6.6 mg/kg bwt i.v. q. 24 h for 7 doses and urinary protein, creatinine, γ-glutamyltransferase and electrolytes were measured on Days 0, 3 and 7 to quantify renal injury. Concentrations of gentamicin were measured using liquid chromatography-tandem mass spectrometry. RESULTS: After i.v. administration, LG had a significantly higher mean (± s.d.) half-life (16.3 ± 3.5 vs. 6.2 ± 1.8 h) and volume of distribution (2.00 ± 1.03 vs. 0.72 ± 0.32 l/kg bwt) compared with FG. Peak gentamicin concentrations in bronchoalveolar cells were significantly higher for LG compared with FG after administration by both the i.v. (5.27 ± 2.67 vs. 2.98 ± 1.67 mg/l) and the nebulised (4.47 ± 2.66 vs. 1.49 ± 0.57 mg/l) routes. Liposomal gentamicin was well tolerated by all foals and indices of renal injury were not significantly different from those of foals administered FG. CONCLUSIONS: Administration of LG is well tolerated and results in higher intracellular drug concentrations than FG. Liposomal gentamicin warrants further investigation for the treatment of infections caused by intracellular pathogens such as Rhodococcus equi.

Role of the phospholipase A2 receptor in liposome drug delivery in prostate cancer cells.

The M-type phospholipase A2 receptor (PLA2R1) is a member of the C-type lectin superfamily and can internalize secreted phospholipase A2 (sPLA2) via endocytosis in non-cancer cells. sPLA2 itself was recently shown to be overexpressed in prostate tumors and to be a possible mediator of metastasis; however, little is known about the expression of PLA2R1 or its function in prostate cancers. Thus, we examined PLA2R1 expression in primary prostate cells (PCS-440-010) and human prostate cancer cells (LNCaP, DU-145, and PC-3), and we determined the effect of PLA2R1 knockdown on cytotoxicity induced by free or liposome-encapsulated chemotherapeutics. Immunoblot analysis demonstrated that the expression of PLA2R1 was higher in prostate cancer cells compared to that in primary prostate cells. Knockdown of PLA2R1 expression in PC-3 cells using shRNA increased cell proliferation and did not affect the toxicity of cisplatin, doxorubicin (Dox), and docetaxel. In contrast, PLA2R1 knockdown increased the in vitro toxicity of Dox encapsulated in sPLA2 responsive liposomes (SPRL) and correlated with increased Dox and SPRL uptake. Knockdown of PLA2R1 also increased the expression of Group IIA and X sPLA2. These data show the novel findings that PLA2R1 is expressed in prostate cancer cells, that PLA2R1 expression alters cell proliferation, and that PLA2R1 modulates the behavior of liposome-based nanoparticles. Furthermore, these studies suggest that PLA2R1 may represent a novel molecular target for controlling tumor growth or modulating delivery of lipid-based nanomedicines.

Evidence for distinct mechanisms of uptake and antitumor activity of secretory phospholipase A2 responsive liposome in prostate cancer.

Secretory phospholipase A(2) (sPLA(2)) cleave phospholipids at sn-2 ester bonds, releasing lysophospholipids and fatty acids, and are over expressed in several pathologies, including inflammation, arthritis, sepsis and breast and prostate cancers. Herein we evaluated the therapeutic activity of liposomes engineered to be responsive to different sPLA(2) isoforms compared to clinically used long-circulating (pegylated) sterically stabilized liposomes (SSL) in vitro and in vivo, and assessed differences in roles of sPLA(2) in the mechanism of uptake and delivery of these nanoparticles. Exposing sPLA(2) responsive liposomes (SPRL) to sPLA(2) increased the release of intraluminal entrapped contents in a time-dependent manner that was inhibited by the sPLA(2) inhibitor LY3117273. Treatment of prostate cancer cells with doxorubicin encapsulated in SSL and SPRL resulted in cytotoxicity in LNCaP, DU-145 and PC-3 cells lines comparable to free drug. Interestingly, cytotoxicity was not altered by sPLA(2) inhibition. Tracking of drug and liposome delivery using fluorescence microscopy and flow cytometry, we demonstrated that drug uptake was liposome-dependent, as encapsulation of doxorubicin in SPRL resulted in 1.5 to 2-fold greater intracellular drug levels compared to SSL. Liposome uptake was cell-dependent and did not correlate to doxorubicin uptake; however, doxorubicin uptake was generally greatest in PC-3 cells, followed by DU-145 cells and then LNCaP cells. In almost all cases, uptake of one of our formulations, SPRL-E, was greater than SSL. The therapeutic activity of SPRL in vivo was demonstrated using a mouse xenograft model of human prostate cancer, which showed that doxorubicin entrapped within SPRL decreased tumor growth compared to SSL, suggesting that SPRL are more effective at slowing tumor growth than a SSL formulation similar to the FDA approved DOXIL™. Collectively, these data show the therapeutic activity of SPRL compared to SSL, yield insights into the mechanisms of action of these nanoparticles and suggest that SPRL could be useful for treatment of other pathologies that over express sPLA(2).

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

REASONS FOR PERFORMING STUDY: Therapeutic 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. OBJECTIVE: To determine the effect of age on the pharmacokinetics of a single 12 mg/kg bwt i.v. dose of gentamicin in foals. METHODS: Six 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. RESULTS: Elimination 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). CONCLUSIONS: The pharmacokinetics of gentamicin change considerably in the first 2 weeks of life. POTENTIAL RELEVANCE: Intravenous 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.

Pharmacokinetic assessment of ketanserin in the horse.

The purpose of this study was to determine the pharmacokinetics (PK) of the 5-HT(2A) receptor antagonist ketanserin in healthy adult horses, and to develop a computational model that could be used to optimize dosing. Plasma concentrations of ketanserin were determined using liquid chromatography with mass spectrometry after single and multiple intravenous administration in the horse. A two-compartment linear pharmacokinetic model described the plasma concentration-time profile of ketanserin after single and multiple doses in healthy horses; the terminal half-life was 11.5 h; steady-state volume of distribution was 10.5 L/kg; AUC was 115 ng · h/mL; and clearance was 0.87 L/h/kg. Model simulations followed by the examination in three healthy horses suggest 0.3 mg/kg q.8 h exhibited linear PK and produced consistent systemic blood concentrations of ketanserin above 3 ng/mL.

A phase I clinical and pharmacokinetic study of the multi-drug resistance protein-1 (MRP-1) inhibitor sulindac, in combination with epirubicin in patients with advanced cancer.

PURPOSE: Multi-drug resistance mediated by ATP-binding cassette trans-membrane protein pumps is an important cause of cancer treatment failure. Sulindac has been shown to be a competitive substrate for the clinically important resistance protein, multi-drug resistance protein-1 (MRP-1), and thus might enhance the anti-cancer activity of substrate chemotherapeutic agents, e.g. anthracyclines. METHODS: We conducted a dose-escalating, single arm, prospective, open label, non-randomised phase I trial of epirubicin (75 mg/m(2)) in combination with escalating oral doses of sulindac (0-800 mg) in patients with advanced cancer to identify an appropriate dose of sulindac to use in future resistance studies. Anthracycline and sulindac pharmacokinetics were studied in cycles 1 and 3. RESULTS: Seventeen patients (8 breast, 3 lung, 2 bowel, 1 melanoma, 1 renal, 1 ovarian and 1 of unknown primary origin, 16/17 having had prior chemotherapy) were enrolled. Eight patients received a full six cycles of treatment; 14 patients received three or more cycles. Dose-limiting toxicity was observed in two patients at 800 mg sulindac (1 renal impairment, 1 fatal haemoptysis in a patient with advanced lung cancer), and sulindac 600 mg was deemed to be the maximum tolerated dose. Sulindac had no effect on epirubicin pharmacokinetics. Among 15 patients with evaluable tumour, two partial responses were seen (malignant melanoma and breast cancer). Four others had prolonged stable disease. CONCLUSION: Epirubicin 75 mg/m(2) and sulindac 600 mg are the recommended doses for phase II studies for these agents in combination.

Genetic and environmental influences on MMPI factor scales: joint model fitting to twin and adoption data.

In general, the shared family environment appears to play a negligible role in determining individual differences in personality and interests. Nevertheless, scattered reports of significant shared environmental influence on such variables appear in the literature. Using data from the Texas Adoption Project (TAP), the current study attempted to replicate twin study findings of significant shared environmental variance on four of nine Minnesota Multiphasic Personality Inventory (MMPI) factor scales (Rose, 1988). Conventional behavioral genetic analyses of the adoption data agreed in affirming a significant shared environmental influence on individual differences in Religious Orthodoxy only. Subsequent simultaneous modeling of Rose's twin data and TAP adoption data resulted in three scales (Extraversion, Inadequacy, and Religious Orthodoxy) showing significant shared environmental influence. Again, effects were most substantial for Religious Orthodoxy, where the shared environment accounted for nearly 50% of the variance. It is argued that assortative mating cannot explain this finding.