Comparison of phosphonate, hydroxypropyl and carboxylate pendants in Fe(III) macrocyclic complexes as MRI contrast agents.

Fe(III) macrocyclic complexes containing a macrocycle and three pendant groups including phosphonate (NOTP =1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid), carboxylate (NOTA = 1,4,7 - triazacyclononane - N,N',N″ - triacetate) or hydroxypropyl (NOHP =(2S,2'S,2"S)-1,1',1″-(1,4,7-triazonane-1,4,7-triyl)tris(propan-2-ol)) were studied in order to compare the effect of these donor groups on solution chemistry and water proton relaxivity. All three complexes, Fe(NOTP), Fe(NOHP) and Fe(NOTA), display a large degree of kinetic inertness to dissociation in the presence of phosphate and carbonate, under acidic conditions of 100 mM HCl or 1 M HCl or to trans-metalation with Zn(II). The r1 proton relaxivity of the complexes at 1.4 T, 33 °C is compared over the pH range of 1 to 10. At pH 7.4, 33 °C, 1.4 T, Fe(NOHP) has the largest relaxivity (1.5 mM-1 s-1), Fe(NOTP) is second at 1.0 mM-1 s-1, whereas Fe(NOTA) is the lowest at 0.61 mM-1 s-1. Fe(NOTP), Fe(NOHP) and Fe(NOTA) all show an increase in relaxivity at very acidic pH values (< 3) that is consistent with an acid-catalyzed process. Variable temperature 17O NMR studies at near neutral pH are consistent with the absence of an inner-sphere water molecule for Fe(NOTP) and Fe(NOHP), supporting second-sphere or outer-sphere water contributions to proton relaxation. Fe(NOTP) shows contrast enhancement in T1 weighted MRI studies in mice and clears through a renal pathway.

Experimental Study of the Biodistribution of New Bone-Seeking Compounds Based on Phosphonic Acids and Gallium-68.

We investigate biodistribution of gallium-labeled hydroxyethylidenediphosphonic acid (68Ga-HEDP) and diethylenetriaminepentakis(methylenephosphonic acid) (68Ga-DTPMP) in intact Wistar rats. It was shown that 68Ga-DTPMP accumulated mainly in the bone tissue providing high femur/blood and femur/muscle ratios and had high stability in vivo. In contrast, 68Ga-HEDP was characterized by low stability and high uptake of radioactivity in blood throughout the study. So 68Ga-DTPMP can be considered as a new prospective radiotracer in oncology for imaging bone tissue metastasis by positron emission tomography.

Pharmacokinetics of oseltamivir phosphate and oseltamivir carboxylate in non-pregnant and pregnant rhesus monkeys.

Oseltamivir is an antiviral drug approved to treat influenza in humans. Although the dosing regimen of this drug is well established for non-pregnant patients, it is not clear if the significant physiological alterations associated with pregnancy affect the pharmacokinetics of oseltamivir and, thus, warrant different dosing regimens to assure efficacy. In this study, we investigated the suitability of rhesus macaques as an animal model for studying oseltamivir pharmacokinetics during all trimesters of pregnancy in comparison to pre-pregnant conditions. Specifically, we compared the pharmacokinetics of oseltamivir and its pharmacologically active metabolite oseltamivir carboxylate in rhesus monkeys after intravenous and nasogastric administration of 2.5 mg oseltamivir phosphate/kg body weight given prior to and during the first, second, and third trimesters of pregnancy. Pregnancy had only a modest effect upon the pharmacokinetic parameters of oseltamivir and oseltamivir carboxylate. Monkeys treated intravenously in the third trimester had a reduction in Vd and CL, compared to non-pregnant monkeys. These changes did not occur in the other two trimesters. Pregnant monkeys treated intravenously had 20-25% decrease in AUC0-∞ of oseltamivir carboxylate and a corresponding increase in Vd and CL. Pregnant monkeys treated nasogastrically with oseltamivir phosphate demonstrated a pattern that recapitulated intravenous dosing. Taken together these data indicate that rhesus monkeys are an acceptable model for studying drug-pregnancy interactions.

Pharmacokinetics of tenofovir monoester and association with intracellular tenofovir diphosphate following single-dose tenofovir disoproxil fumarate.

BACKGROUND: Tenofovir monoester is a relatively lipophilic intermediate formed during the hydrolysis of tenofovir disoproxil to tenofovir. Its clinical pharmacokinetic profile and influence on the cellular pharmacology of tenofovir diphosphate have not been reported. METHODS: Plasma, PBMC and dried blood spots (DBS) were obtained from HIV-uninfected adults participating in a randomized, cross-over bioequivalence study of single-dose tenofovir disoproxil fumarate (TDF)/emtricitabine unencapsulated or encapsulated with a Proteus® ingestible sensor. Plasma pharmacokinetics of tenofovir monoester and tenofovir were characterized using non-compartmental methods. Relationships with tenofovir diphosphate in DBS and PBMC were examined using mixed-effects models. RESULTS: Samples were available from 24 participants (13 female; 19 white, 3 black, 2 Hispanic). Tenofovir monoester appeared rapidly with a median (range) Tmax of 0.5 h (0.25-2) followed by a rapid monophasic decline with a geometric mean (coefficient of variation) t½ of 26 min (31.0%). Tenofovir monoester Cmax was 131.6 ng/mL (69.8%) and AUC0-4 was 93.3 ng·h/mL (47.9%). The corresponding values for plasma tenofovir were 222.2 ng/mL (37.1%) and 448.1 ng·h/mL (30.0%). Tenofovir monoester AUC0-∞ (but not tenofovir AUC0-∞) was a significant predictor of tenofovir diphosphate in both PBMC (P = 0.015) and DBS (P = 0.005), increasing by 3.8% (95% CI 0.8%-6.8%) and 4.3% (95% CI 1.5%-7.2%), respectively, for every 10 ng·h/mL increase in tenofovir monoester. CONCLUSIONS: Tenofovir monoester Cmax and AUC0-4 were 59.2% and 20.6% of corresponding plasma tenofovir concentrations. Tenofovir monoester was significantly associated with intracellular tenofovir diphosphate concentrations in PBMC and DBS, whereas tenofovir concentrations were not. Tenofovir monoester likely facilitates cell loading, thereby increasing tenofovir diphosphate exposures in vivo.

Brief Report: Pharmacokinetics of Crushed Elvitegravir Combination Tablet Given With or Without Enteral Nutrition.

We investigated whether a fixed-dose combination tablet of elvitegravir, cobicistat, emtricitabine, and tenofovirDF (Stribild) can be crushed and combined with enteral nutrition without influencing pharmacokinetics. This was an open-label, 3-period, single-dose, randomized, crossover trial in 24 healthy volunteers. Subjects received Stribild whole tablet with breakfast (reference), crushed/suspended Stribild + breakfast, crushed/suspended Stribild + enteral nutrition. Crushed/suspended Stribild + enteral nutrition was bioequivalent (90% confidence interval between 80% and 125%) with a whole Stribild tablet. Crushed/suspended Stribild + breakfast showed bioequivalence for the area under the curve (AUC0-32), but not for maximum concentration (Cmax) (considered not clinically relevant). Patients with swallowing difficulties or an enteral feeding tube can use crushed and suspended Stribild tablets.

Comparative assessment of the environmental hazards of and exposure to perfluoroalkyl phosphonic and phosphinic acids (PFPAs and PFPiAs): Current knowledge, gaps, challenges and research needs.

Perfluoroalkyl phosphonic and phosphinic acids (PFPAs and PFPiAs) are sub-groups of per- and polyfluoroalkyl substances (PFASs) that have been commercialized since the 1970s, particularly as defoamers in pesticide formulations and wetting agents in consumer products. Recently, C4/C4 PFPiA and its derivatives have been presented as alternatives to long-chain PFASs in certain applications. In this study, we systematically assess the publicly available information on the hazardous properties, occurrence, and exposure routes of PFPAs and PFPiAs, and make comparisons to the corresponding properties of their better-known carboxylic and sulfonic acid analogs (i.e. PFCAs and PFSAs). This comparative assessment indicates that [i] PFPAs likely have high persistence and long-range transport potential; [ii] PFPiAs may transform to PFPAs (and possibly PFCAs) in the environment and biota; [iii] certain PFPAs and PFPiAs can only be slowly eliminated from rainbow trout and rats, similarly to long-chain PFCAs and PFSAs; [iv] PFPAs and PFPiAs have modes-of-action that are both similar to, and different from, those of PFCAs and PFSAs; and [v] the measured levels of PFPAs/PFPiAs in the global environment and biota appear to be low in comparison to PFCAs and PFSAs, suggesting, for the time being, low risks from PFPAs and PFPiAs alone. Although risks from individual PFPAs/PFPiAs are currently low, their ongoing production and use and high persistence will lead to increasing exposure and risks over time. Furthermore, simultaneous exposure to PFPAs, PFPiAs and other PFASs may result in additive effects necessitating cumulative risk assessments. To facilitate effective future research, we highlight possible strategies to overcome sampling and analytical challenges.

Intestinal behavior of the ester prodrug tenofovir DF in humans.

Tenofovir-disoproxil-fumarate (TDF) is a double ester prodrug which enables intestinal uptake of tenofovir (TFV) after oral administration in humans. In this study, prodrug stability was monitored in situ in the human intestine and in vitro using biorelevant media. In fasted state human intestinal fluids, the prodrug was completely degraded within 90 min, resulting in the formation of the mono-ester intermediate and TFV; in fed state intestinal fluids, the degradation rate of TDF was slightly reduced and no TFV was formed. Intestinal fluid samples aspirated after administration of TDF confirmed extensive intraluminal degradation of TDF in fasted state conditions; a relatively fast absorption of TDF partly compensated for the degradation. Although food intake reduced intestinal degradation, the systemic exposure was not proportionally increased. The lower degradation in fed state conditions may be attributed to competing esterase substrates present in food, lower chemical degradation in the slightly more acidic environment and micellar entrapment, delaying exposure to the "degrading" intestinal environment. The results of this study demonstrate premature intestinal degradation of TDF and suggest that TFV may benefit from a more stable prodrug approach; however, fast absorption may compensate for fast degradation, indicating that prodrug selection should not be limited to stability assays.

Radiolabeling, stability studies, and pharmacokinetic evaluation of thulium-170-labeled acyclic and cyclic polyaminopolyphosphonic acids.

OBJECTIVE: Thulium-170 [T1/2=128.4 days, Eß(max)=968 keV, and Eγ=84 keV (3.26%)] could be considered an easily producible and cost-effective alternative to (89)Sr for the preparation of radiopharmaceuticals for palliation of bone pain arising due to skeletal metastases. Multidentate aminomethylene polyphosphonic acids have already been proven to be effective as carrier moieties for developing radiolabeled bone pain palliation agents using lanthanide radionuclides. Therefore, an attempt was made to evaluate the potential of a series of (170)Tm-labeled acyclic (diethylenetriaminepentamethylene phosphonic acid and triethylenetetraminehexamethylene phosphonic acid) and cyclic polyaminopolyphosphonic acids (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid [DOTMP] and 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetramethylene phosphonic acid [CTMP]) toward their use as alternative bone pain palliation agents. EXPERIMENTAL: Thulium-170 was produced by irradiating the natural Tm2O3 target at a thermal neutron flux of 7×10(13) n·cm(-2)·s(-1) for a period of 60 days. All the phosphonic acid ligands were synthesized and characterized in-house. The protocols for radiolabeling the phosphonic acids with (170)Tm were standardized. Biological evaluation of the (170)Tm-labeled phosphonic acids were carried out in normal Wistar rats by biodistribution as well as by scintigraphic studies. RESULTS: Thulium-170 was produced with adequate specific activity (173 Ci/g, 6.41 TBq/g) and high radionuclidic purity (99.62%). All the (170)Tm-labeled phosphonic acids, except (170)Tm-CTMP, were prepared with very high radiochemical purity (>98%) under optimized reaction conditions and exhibited high stability. All the agents showed selective skeletal accumulation with insignificant uptake in other vital organs/tissues and major clearance through renal pathway. These findings were also substantiated by scintigraphic studies. CONCLUSIONS: Although all the (170)Tm-labeled phosphonic acids showed significant and selective skeletal accumulation, radiochemical studies indicate that (170)Tm-DOTMP is the best choice for carrying out further evaluation toward its use for clinical applications.

[Pharmacokinetics of tenofovir in Beagle dogs after oral dosing of tenofovir dipivoxil fumarate using HPLC-MS/MS analysis].

A simple, rapid and sensitive method was developed for the quantification of tenofovir in plasma of Beagle dogs using HPLC-MS/MS analysis. The analytes tenofovir and internal standard (IS) adefovir were separated on a Zorbax SB-C18 column (3.5 microm, 100 mm x 2.1 mm, Agilent, USA) with mobile phase of methanol/water containing 0.3% formic acid using a gradient elution mode at a flow rate of 0.2 mL x min(-1). The plasma sample preparation was a simple deproteinization by the addition of 20% trichloroacetic acid followed by centrifugation. The detection was performed in positive selected reaction monitoring (SRM) mode with an electrospray ionization (ESI) source. The reactions monitored were m/z 288.1-176.2 for tenofovir and m/z 274.1-162.2 for adefovir (IS). Linear detection responses were obtained for tenofovir ranging from 10 to 5 000 ng x mL(-1). The intra- and inter-day precisions (RSD%) was no more than 6.3% with high recovery and good stability for the quantification, indicating the present method was specific, fast, accurate and reliable. The method was successfully applied to the pharmacokinetic study of two tenofovir agents. Tenofovir dipivoxil fumarate (BP0018, test agent) and tenofovir disoproxil fumarate (reference agent) were orally administrated to 8 Beagle dogs according to the 2 x 2 crossover design. Comparing with the reference agent, the longer MRT and t1/2 were obtained in the group of BP0018, while no significant difference was observed in AUC(0-t), AUC(0-infinity), C(max) and t(max) between them, suggesting that tenofovir dipivoxil fumarate was bioequivalent to the tenofovir disoproxil fumarate in Beagle dogs.

Pre-exposure prophylaxis for HIV infection: how antiretroviral pharmacology helps to monitor and improve adherence.

INTRODUCTION: Pre-exposure prophylaxis (PrEP) with antiretroviral drugs is a novel biomedical intervention that can prevent HIV transmission among high-risk populations. As findings from multiple PrEP studies have suggested that adherence is vital to achieve the full prevention benefits of PrEP, it is important to understand the clinical pharmacology and pharmacokinetic (PK) properties of PrEP antiretrovirals, the association of PK and PrEP efficacy, and the potential for drug concentration measurement to be used as a tool to monitor PrEP adherence. AREAS COVERED: This review examines studies related to PrEP adherence with attention to the clinical pharmacology and PK of current and novel PrEP agents. Studies of animal models, PK, and clinical trials related to PrEP and adherence were reviewed. EXPERT OPINION: In summary, when combined as part of a comprehensive prevention strategy that includes use of condoms and risk-reduction counseling, PrEP has tremendous promise as an adjunctive biomedical HIV prevention intervention, providing that adherence is maintained.

MTN-001: randomized pharmacokinetic cross-over study comparing tenofovir vaginal gel and oral tablets in vaginal tissue and other compartments.

BACKGROUND: Oral and vaginal preparations of tenofovir as pre-exposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection have demonstrated variable efficacy in men and women prompting assessment of variation in drug concentration as an explanation. Knowledge of tenofovir concentration and its active form, tenofovir diphosphate, at the putative vaginal and rectal site of action and its relationship to concentrations at multiple other anatomic locations may provide key information for both interpreting PrEP study outcomes and planning future PrEP drug development. OBJECTIVE: MTN-001 was designed to directly compare oral to vaginal steady-state tenofovir pharmacokinetics in blood, vaginal tissue, and vaginal and rectal fluid in a paired cross-over design. METHODS AND FINDINGS: We enrolled 144 HIV-uninfected women at 4 US and 3 African clinical research sites in an open label, 3-period crossover study of three different daily tenofovir regimens, each for 6 weeks (oral 300 mg tenofovir disoproxil fumarate, vaginal 1% tenofovir gel [40 mg], or both). Serum concentrations after vaginal dosing were 56-fold lower than after oral dosing (p<0.001). Vaginal tissue tenofovir diphosphate was quantifiable in ≥90% of women with vaginal dosing and only 19% of women with oral dosing. Vaginal tissue tenofovir diphosphate was ≥130-fold higher with vaginal compared to oral dosing (p<0.001). Rectal fluid tenofovir concentrations in vaginal dosing periods were higher than concentrations measured in the oral only dosing period (p<0.03). CONCLUSIONS: Compared to oral dosing, vaginal dosing achieved much lower serum concentrations and much higher vaginal tissue concentrations. Even allowing for 100-fold concentration differences due to poor adherence or less frequent prescribed dosing, vaginal dosing of tenofovir should provide higher active site concentrations and theoretically greater PrEP efficacy than oral dosing; randomized topical dosing PrEP trials to the contrary indicates that factors beyond tenofovir's antiviral effect substantially influence PrEP efficacy. TRIAL REGISTRATION: ClinicalTrials.gov NCT00592124.

Pharmacokinetics and food interaction of a novel prodrug of tenofovir, tenofovir dipivoxil fumarate, in healthy volunteers.

WHAT IS KNOWN AND OBJECTIVE: Tenofovir dipivoxil fumarate is a novel ester prodrug of tenofovir, a specific anti-hepatitis B virus (HBV) drug candidate. The pharmacokinetic properties and the effects of food intake on tenofovir dipivoxil have not yet been reported in healthy adults. The aim of this study was to evaluate the pharmacokinetic properties and food interaction of tenofovir dipivoxil in healthy Chinese volunteers. METHODS: Pharmacokinetic studies included an ascending single dose of 150, 300, 600 mg and multiple doses of 300 mg. Food interaction was evaluated following a single oral dose of tenofovir dipivoxil fumarate 300 mg administered with a high-fat and high-energy standard breakfast or after a 12-h fast. Pharmacokinetic parameters of tenofovir given in each treatment period were calculated using non-compartmental analysis. RESULTS: After a single dose of 150, 300 and 600 mg, the main pharmacokinetic parameters for tenofovir were as follows: Cmax 209·6, 456·7, 989·8 ng/mL; AUClast 1744·9, 2663·5, 6010·2 ng h/mL, respectively. After multiple doses of 300 mg, the main pharmacokinetic parameters for tenofovir were Cmax 523·4 ng/mL, AUClast 4152·4 ng h/mL. After a single dose of 300 mg with a high-fat and high-energy standard breakfast, the main pharmacokinetic parameters for tenofovir were Cmax 448·5 ng/mL, AUClast 3286·8 ng h/mL. The plasma Cmax and AUC of tenofovir showed significance difference between a single dose of 300 mg and the accordingly multiple doses (P < 0·05). A standard high-fat meal enhanced mean AUClast values of tenofovir (relative AUClast  = 125·8%; 90% CI 114·5, 136·2); however, food did not show any significant on Cmax (relative Cmax  = 103·4%; 90% CI 94·6, 112·6). WHAT IS NEW AND CONCLUSIONS: Oral tenofovir dipivoxil fumarate produced predictable and dose-proportional plasma tenofovir pharmacokinetics. The accumulation ratio was 1·51, suggesting tenofovir dipivoxil fumarate displayed accumulation after repeated administration. The bioavailability of tenofovir dipivoxil fumarate was increased by approximately 25% as measured by AUClast after a single dose when taken with food, compared with fasting.

Preparation and biological evaluation of (64)Cu labeled Tyr(3)-octreotate using a phosphonic acid-based cross-bridged macrocyclic chelator.

Somatostatin receptors (SSTr) are overexpressed in a wide range of neuroendocrine tumors, making them excellent targets for nuclear imaging and therapy, and radiolabeled somatostatin analogues have been investigated for positron emission tomography imaging and radionuclide therapy of SSTr-positive tumors, especially of the subtype-2 (SSTr2). The aim of this study was to develop a somatostatin analogue, Tyr(3)-octreotate (Y3-TATE), conjugated to a novel cross-bridged macrocyclic chelator, 11-carboxymethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4-methanephosphonic acid (CB-TE1A1P). Unlike traditional cross-bridged macrocycles, such as 4,11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (CB-TE2A), CB-TE1A1P-Y3-TATE was radiolabeled with (64)Cu in high purity and high specific activity using mild conditions. Saturation binding assays revealed that (64)Cu-CB-TE1A1P-Y3-TATE had comparable binding affinity but bound to more binding sites in AR42J rat pancreatic tumor cell membranes than (64)Cu-CB-TE2A-Y3-TATE. Both radiopharmaceuticals showed comparable uptake in SSTr2 positive tissues in AR42J tumor-bearing rats. (64)Cu-CB-TE1A1P-Y3-TATE demonstrated improved blood clearance compared to (64)Cu-CB-TE2A-Y3-TATE, as the tumor/blood ratios of (64)Cu-CB-TE1A1P-Y3-TATE were shown to be significantly higher than those of (64)Cu-CB-TE2A-Y3-TATE at 4 and 24 h postinjection. (64)Cu-CB-TE1A1P-Y3-TATE, in spite of a relatively high kidney uptake, accumulated less in nontarget organs such as liver, lung, and bone. Small animal PET/CT imaging of (64)Cu-CB-TE1A1P-Y3-TATE in AR42J tumor bearing rats validated significant uptake and good contrast in the tumor. This study suggests that CB-TE1A1P is a promising bifunctional chelator for (64)Cu-labeled for Y3-TATE, owing to high binding affinity and target tissue uptake, the ability to radiolabel the agent at lower temperatures, and improved tumor/nontarget organ ratios over (64)Cu-CB-TE2A-Y3-TATE.

Phosphorous acid residues in apples after foliar fertilization: results of field trials.

The levels of phosphorous acid residues in apples after foliar fertilization with P fertilizers and after treatment with a phosphonate fungicide (Fosetyl-Al) were determined and compared. Two field trials and a glasshouse experiment, using different genotypes and plants of different age, were carried out and monitored over a three-year period. Phosphorous acid residues were found in apples after application of foliar P fertilizers. Concentrations of the residues ranged between 0.02 and 14 mg kg(-1) depending on the phosphorous acid content in the fertilizer used and the plant size and yield. The treatments induced an accumulation of the residue in the course of the experiments, which in some cases reached a level exceeding the maximum limit set by EU legislation. Residues were also detected in other plant organs, i.e., roots and buds. Plants treated with Fosetyl-Al contained phosphorous acid residues in their fruits and buds two years after the suspension of the treatment, suggesting a long-term persistence of the substance in plant storage organs. A second experiment, involving treatment of trees with seven foliar fertilizers of different composition, also induced accumulation of phosphorous acid residues in fruits. It is concluded that a wide array of foliar products containing phosphorous acid, even as a minor component, could mimic the residue effect of phosphonate fungicide treatments.

Pharmacokinetics of a tumor necrosis factor-alpha phosphorothioate 2'-O-(2-methoxyethyl) modified antisense oligonucleotide: comparison across species.

The pharmacokinetics of a 2'-O-(2-methoxyethyl)-ribose modified phosphorothioate oligonucleotide, ISIS 104838 (human tumor necrosis factor-alpha antisense), have been characterized in mouse, rat, dog, monkey, and human. Plasma pharmacokinetics after i.v. administration exhibited relatively rapid distribution from plasma to tissues with a distribution half-life estimated from approximately 15 to 45 min in all species. Absorption after s.c. injection was high (80-100%), and absorption after intrajejunal administration in proprietary formulations was as high as 10% bioavailability compared with i.v. administration. Urinary excretion of the parent drug was low, with less than 1% of the administered dose excreted in urine after i.v. infusion in monkeys at clinically relevant doses (< or = 5 mg/kg). ISIS 104838 is highly bound to plasma proteins, likely preventing renal filtration. However, shortened oligonucleotide metabolites of ISIS 104838 lose their affinity to bind plasma proteins. Thus, excretion of radiolabel (mostly as metabolites) in urine (75%) and feces (5-10%) was nearly complete by 90 days. Elimination of ISIS 104838 from tissue was slow (multiple days) for all species, depending on the tissue or organ. The highest concentrations of ISIS 104838 in tissues were seen in kidney, liver, lymph nodes, bone marrow, and spleen. In general, concentrations of ISIS 104838 were higher in monkey tissues than in rodents at body weight-equivalent doses. Plasma pharmacokinetics scale well across species as a function of body weight alone. This favorable pharmacokinetic profile for ISIS 104838 provides guidance for clinical development and appears to support infrequent and convenient dose administration.

Glutathione stability in whole blood: effects of various deproteinizing acids.

High-performance liquid chromatography separation of reduced and oxidized glutathione (GSH and GSSG) in biologic samples using electrochemical detection offers the convenience of both simultaneous quantitation and simple sample preparation. Rapid acidification is required to prevent GSH autooxidation, GSH and GSSG degradation, and precipitate proteins that interfere with analysis. Currently, little consistency exists in the literature regarding acid selection or the feasibility of sample storage before analysis. The purpose of this work was to examine the effects of perchloric (PCA), trichloroacetic (TCA), metaphosphoric (MPA), and 5-sulfosalicylic (SSA) acids on the short-term stability of GSH and GSSG measurements in whole blood. Samples were collected from adult volunteers and treated with multiple concentrations of each acid. The samples were analyzed immediately and aliquots were stored at -80 degrees C for up to 28 days. The suitability of each acid was assessed by percentage change of GSH and GSSG from baseline, efficiency of protein removal, and alteration of chromatogram characteristics. In general, increasing the acid concentration improved sample stability. Nevertheless, SSA did not achieve acceptable sample stability at any concentration tested. MPA was found to leave substantial amounts of protein in the samples, and TCA may interfere with the peaks of interest. Based on these results, a final concentration of 15% PCA is suggested for analysis of glutathione in whole blood. Although immediate sample preparation is preferred, 15% PCA can maintain sample integrity for 4 weeks after storage at -80 degrees C.

In vitro radioautographic studies of the biodistribution of radiopharmaceuticals on blood elements

In the present study evaluated the binding of the radiopharmaceuticals sodium pertechnetate (Na (99m)TcO4), methylenediphosphonic acid (99m)Tc-MDP)) and glucoheptonate acid (99m)Tc-GHA)) to blood elements using centrifugation and radioautographic techniques. Heparinized blood was incubated with the labelled compounds for 0, 1, 2, 3, 4, 6 and 24 h. Plasma (P) and blood cells (BC) were isolated and precipitated with 5 percent trichloroacetic acid (TCA), and soluble (SF) and isoluble fractions (IF) were separated. Blood samples were prepared (0 and 24 h) and coated with LM-1 radioautographic emulsions and percent radioactivity (percent rad) in P and BC was determined. The binding of Na (99m)TcO4 (percentrad) to P was 61.2 percent (0 h) and 46.0 percent (24 h), and radioautography showed 63.7 percent (0 h) and 43.3 percent (24 h). The binding to BC was 38.8 percent (0 h) and 54.0 percent (24 h), and radioautography showed 36.3 percent (0h) and 56.7 percent (24 h), and radioautography showed 36.3 percent (0 h) and 56.7 percent (24 h). (99m) Tc-MDP study presented 91.1 percent (0 h) to P and 87.2 percent (24 h), and radioautography showed 67.9 percent (0 h) and 67.4 percent (24 h). The binding to BC was 8.9 percent (0 h) and 12.8 percent (24 h), and radioautography showed 32.1 percent (0 h) and 32.6 percent (24 h). (99m)Tc-GHA study was 90.1 percent (0 h) to P and 79.9 percent (24 h), and radioautography showed 67.2 percent (0 h) and 60.1 percent (24 h). The binding to BC was 9.9 percent (0 h) and 20.1 percent (24 h), and radioautography showed 32.8 percent (0 h) and 39.9 percent (24 h). The comparasion of the obtained results suggests that the binding to plasma and blood cells in the two techniques used (radioautography and centrifugation) qualitatively in accordance.