Systemic Exposure Levels Research Articles

Abstract B56: A phase 1, open-label, dose escalation, nonrandomized study to assess the maximum tolerated dose, dose limiting toxicity, and pharmacokinetics of OPB-31121 in subjects with advanced solid tumors.

Abstract Background: OPB-31121 is a novel compound exhibiting potent growth inhibition of cancer cell lines in vitro and xenografts in vivo. The exact mechanism of action of OPB-31121 has not been fully characterized, but studies indicate that a major effect is inhibition of STAT3 phosphorylation. STAT3 is frequently activated in a variety of solid and hematologic malignancies and may present an important target for antitumor therapy. Methods: Open-label, non-randomized, multi-center study in subjects with advanced solid tumors, using a 3+3 dose escalation design. OPB-31121 was administered orally for 21 days followed by 7 days rest per cycle (28-day cycle). The starting dose was 50 mg BID with escalations planned until the dose-limiting toxicity (DLT) was reached. The primary endpoint was determination of maximum tolerated dose (MTD). Additional endpoints included safety, pharmacokinetics, and anti-tumor effect of OPB-31121. Results: 30 subjects received treatment with OPB-31121. Most common tumor types were colorectal cancer (15), breast (3) and thyroid (2). Mean age was 55.9 (range 35–80) years and 17 of the patients were female. Most common adverse events (AEs) potentially attributed to treatment were gastrointestinal: nausea (80%), vomiting (73%), diarrhea (63%), anorexia (20%), and constipation (17%). Most AEs were CTCAE grades 1–2 and manageable with supportive treatment. Three DLTs were observed: one at 300 mg BID (grade 3 lactic acidosis), and two at 350 mg BID (a grade 3 diarrhea and a grade 3 vomiting); the MTD was 300 mg BID. All patients recovered from DLTs after discontinuing the drug. Six additional (9 total) subjects discontinued during the first cycle. Eight subjects completed only one cycle and 13 completed two cycles. No objective responses were observed. Disease progression was observed in all evaluable patients at first restaging. Pharmacokinetic measurements showed low and transient plasma levels of OPB-31121. Inter-patient variability was high. Exposure was low - area-under-the-curve (AUC) values were 2–3 orders of magnitude lower than those measured at active doses in mouse models. Analysis of metabolites in plasma samples indicates extensive CYP3A4 metabolism and suggests a large first-pass effect in humans, which had not been observed in rodents. Conclusions: OPB-31121 does not show potential as a therapeutic option for most malignancies. The extensive first-pass metabolism and dose-limiting gastrointestinal AEs limit the level of systemic exposure that can be achieved with this agent. Further studies may be warranted in cancers of organs where local concentrations of the compound may be higher (e.g., liver) and an exploratory study in hepatocellular carcinoma is ongoing in Asia. Because STAT3 remains an attractive antitumor target, chemically related compounds with similar pharmacologic activities are currently being evaluated preclinically. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B56.

Biological monitoring of pesticide exposures in residents living near agricultural land

BackgroundThere is currently a lack of reliable information on the exposures of residents and bystanders to pesticides in the UK. Previous research has shown that the methods currently used for assessing pesticide exposure for regulatory purposes are appropriate for farm workers [1]. However, there were indications that the exposures of bystanders may sometimes be underestimated. The previous study did not collect data for residents. Therefore, this study aims to collect measurements to determine if the current methods and tools are appropriate for assessing pesticide exposure for residents living near agricultural fields.Methods/designThe study will recruit owners of farms and orchards (hereafter both will be referred to as farms) that spray their agricultural crops with certain specified pesticides, and which have residential areas in close proximity to these fields. Recruited farms will be asked to provide details of their pesticide usage throughout the spray season. Informed consenting residents (adults (18 years and over) and children (aged 4-12 years)) will be asked to provide urine samples and accompanying activity diaries during the spraying season and in addition for a limited number of weeks before/after the spray season to allow background pesticide metabolite levels to be determined. Selected urine samples will be analysed for the pesticide metabolites of interest. Statistical analysis and mathematical modelling will use the laboratory results, along with the additional data collected from the farmers and residents, to determine systemic exposure levels amongst residents. Surveys will be carried out in selected areas of the United Kingdom over two years (2011 and 2012), covering two spraying seasons and the time between the spraying seasons.DiscussionThe described study protocol was implemented for the sample and data collection procedures carried out in 2011. Based on experience to date, no major changes to the protocol are anticipated for the 2012 spray season although the pesticides and regional areas for inclusion in 2012 are still to be confirmed.

Monitoring of systemic exposure to plant protection products and DNA damage in orchard workers

The systemic exposure of plum tree growers and operators to plant protection products (PPPs) and effects on DNA were assessed. Specifically, a GC–MS/MS method was developed and validated for the analysis of serum samples for the presence of seven active substances of PPPs. The analytical results verified the presence of myclobutanil, propargite, cypermethrin and deltamethrin in 7 out of 19 serum samples. The incidence of DNA damage was monitored using the single cell electrophoresis assay (comet assay). A paired Student's t-test revealed a statistically significant increase of SSBs in the blood samples collected at the end of the cropping period as compared to the samples collected from the same subjects before the start of PPPs application period. Moreover, the group of seven subjects with detectable serum pesticides levels revealed statistically significant increase of SSBs as compared to the group of subjects with no detectable PPP levels. The results of the present study demonstrate that the agriculture workers may exhibit detectable level of systemic exposure to the applied PPPs which are correlated to increased DNA damage during the cultivation period.

4‐Substituted Thioquinolines and Thiazoloquinolines: Potent, Selective, and Tween‐80 in vitro Dependent Families of Antitubercular Agents with Moderate in vivo Activity

Two new families of closely related selective, non-cytotoxic, and potent antitubercular agents were discovered: thioquinolines and thiazoloquinolines. The compounds were found to possess potent antitubercular properties in vitro, an activity that is dependent on experimental conditions of MIC determination (resazurin test and the presence or absence of Tween-80). To clarify the therapeutic potential of these compound families, a medicinal chemistry effort was undertaken to generate a lead-like structure that would enable murine efficacy studies and help elucidate the in vivo implications of the in vitro observations. Although the final compounds showed only limited levels of systemic exposure in mice, modest levels of efficacy in vivo at nontoxic doses were observed.

A Phase I/IIa Clinical Trial of a Recombinant Rho Protein Antagonist in Acute Spinal Cord Injury

Multiple lines of evidence have validated the Rho pathway as important in controlling the neuronal response to growth inhibitory proteins after central nervous system (CNS) injury. A drug called BA-210 (trademarked as Cethrin(®)) blocks activation of Rho and has shown promise in pre-clinical animal studies in being used to treat spinal cord injury (SCI). This is a report of a Phase I/IIa clinical study designed to test the safety and tolerability of the drug, and the neurological status of patients following the administration of a single dose of BA-210 applied during surgery following acute SCI. Patients with thoracic (T2-T12) or cervical (C4-T1) SCI were sequentially recruited for this dose-ranging (0.3 mg to 9 mg Cethrin), multi-center study of 48 patients with complete American Spinal Injury Association assessment (ASIA) A. Vital signs; clinical laboratory tests; computed tomography (CT) scans of the spine, head, and abdomen; magnetic resonance imaging (MRI) of the spine, and ASIA assessment were performed in the pre-study period and in follow-up periods out to 1 year after treatment. The treatment-emergent adverse events that were reported were typical for a population of acute SCI patients, and no serious adverse events were attributed to the drug. The pharmacokinetic analysis showed low levels of systemic exposure to the drug, and there was high inter-patient variability. Changes in ASIA motor scores from baseline were low across all dose groups in thoracic patients (1.8±5.1) and larger in cervical patients (18.6±19.3). The largest change in motor score was observed in the cervical patients treated with 3 mg of Cethrin in whom a 27.3±13.3 point improvement in ASIA motor score at 12 months was observed. Approximately 6% of thoracic patients converted from ASIA A to ASIA C or D compared to 31% of cervical patients and 66% for the 3-mg cervical cohort. Although the patient numbers are small, the observed motor recovery in this open-label trial suggests that BA-210 may increase neurological recovery after complete SCI. Further clinical trials with Cethrin in SCI patients are planned, to establish evidence of efficacy.

Intestinal Absorption and Presystemic Elimination of Various Chemical Constituents Present in GBE50 Extract, a Standardized Extract of Ginkgo biloba Leaves

The nature and level of systemic exposure to active herbal constituents will profoundly affect their bioactivities at action sites, which is fundamental in understanding their roles in the overall beneficial effects of an herbal medicine. The objective of this study is to gain a full picture of the systemic exposure to various putatively active ginkgo constituents after p.o. administration of GBE50 extract, a standardized extract of Ginkgo biloba leaves, to rats and understanding of the relevant mechanisms governing the intestinal absorption and presystemic elimination. To define the ginkgo compounds to be studied, a literature informatics-guided chemical profiling revealed that GBE50 extract contained 71 ginkgo constituents, including terpene lactones, flavonols, flavones, an isoflavone, biflavones, flavanols, and carboxylic acids, at levels ranging from 0.01 to 55.3mg/g. Among the ginkgo constituent groups the terpene lactones and the flavonol glycosides were significantly measurable in the post-administrative rat plasma. The intestinal absorption of terpene lactones appeared to be dictated by their intermediate membrane permeability, while the influences of MDR-1-mediated intestinal efflux and the presystemic metabolism and biliary excretion might be limited. Because of their deglycosylation, their absence in the small intestine and relatively slow presystemic elimination, many intact flavonol glycosides could be absorbed albeit to a limited extent. Colonic deglycosylation of the flavonol glycosides occurred and the glucuronides of flavonol aglycones were also measured in the rat plasma. Although some biflavones had relatively high abundance in GBE50 extract, these ginkgo constituents were not measured in the rat plasma because of their poor solubility and poor permeability that hindered the intestinal absorption. The levels of the remaining ginkgo constituents in GBE50 extract were too low to be measured in the rat plasma. The current study enabled us to better understand the nature of systemic exposure to ginkgo compounds after p.o. administration of GBE50 extract and to more precisely implement multi-component PK study of the extract.

Avaliação dos níveis de mercúrio sistêmico após exposição ocupacional ao amálgama dentário. Parte II: avaliação longitudinal

This study was a longitudinal evaluation of the systemic mercury exposure levels. Thirty urine samples were collected from ten male and female undergraduate dental school students, distributed into three dependent groups: G1 (n = 10) - students before their first contact with silver amalgam; G2 (n = 10) the same group of students within 48 hours after their first occupational contact with silver amalgam; G3 (n = 10) the same group of students at the end of the course, three and a half years later. In this study, the cold vapor atomic absorption spectroscopy (CVAAS) was used for urine analysis. There was a significant statistical difference to ANOVA test between dependent groups GR1 x GR2 (p = 0,001218) and GR2 x GR3 (p = 0,012423). Handling dental amalgam offers a potential risk to increase mercury levels.

Influence of continuous venovenous hemofiltration and continuous venovenous hemodiafiltration on the disposition of doripenem.

The pharmacokinetics, safety, and tolerability of a single 1-hour, 500-mg intravenous infusion of doripenem were assessed in dialysis-dependent subjects with stage 5 chronic kidney disease undergoing continuous renal replacement therapy (CRRT) via 12-hour continuous venovenous hemofiltration (CVVH) (n = 6) or continuous venovenous hemodiafiltration (CVVHDF) (n = 5). Healthy volunteers were also assessed (n = 12). Concentrations of doripenem and the primary metabolite doripenem-M-1 were measured in plasma and ultrafiltrate or ultrafiltrate/dialysate by a validated liquid chromatography-tandem mass spectrometry method. In dialysis-dependent subjects, levels of systemic exposure to doripenem and doripenem-M-1 were approximately 3- and 5-fold greater, respectively, than those in healthy subjects: for doripenem, 98 μg·h/ml for CVVH and 77 μg·h/ml for CVVHDF versus 32 μg·h/ml for healthy subjects, and for doripenem-M-1, 24 μg·h/ml for CVVH and 22 μg·h/ml for CVVHDF versus 4.7 μg·h/ml for healthy subjects. The mean sieving coefficients and saturation coefficients were >0.67 for both doripenem and doripenem-M-1. During CVVH and CVVHDF, respectively, the percentages of administered doripenem dose removed were 38% and 29%, and clearances of doripenem were 22 and 25 ml/min. Both CVVH and CVVHDF efficiently removed doripenem and doripenem-M-1. Despite significant removal of drug by CVVH and CVVHDF, a single 1-hour, 500-mg doripenem infusion produced significantly higher plasma concentrations of doripenem, higher systemic exposure (area under the plasma concentration-time curve from time zero to 12 h after the start of infusion [AUC(0-12)]), and longer half-life (t(1/2)) in subjects receiving CVVH or CVVHDF than in healthy volunteers. The recovery of drug in ultrafiltrate and ultrafiltrate/dialysate and the enhanced rate of reduction of plasma concentrations indicate that CVVH and CVVHDF significantly augmented residual total body clearance of doripenem in subjects receiving CRRT. Doripenem dosage regimens for patients receiving CRRT thus need to be adjusted.

Atenolol Exposure and Risk for Development of Adverse Metabolic Effects: A Pilot Study

To evaluate whether the level of systemic exposure to atenolol explains observed interindividual differences in adverse metabolic responses. Open-label, prospective, pharmacokinetic pilot substudy of the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study. General clinical research center. Fifteen hypertensive adults (mean age 46 +/- 8.9 yrs) who were enrolled in the PEAR study. Patients received atenolol therapy for at least 8 weeks, with 5 of those weeks at a dosage of 100 mg/day, and then underwent a 2-hour oral glucose tolerance test during a pharmacokinetic study visit. Twenty-hour plasma atenolol concentrations were measured during the pharmacokinetic visit. Glucose and insulin levels were measured during the 2-hour oral glucose tolerance test, and fasting plasma lipid, glucose, and insulin levels were measured at baseline and after 8 weeks of atenolol treatment. A significant association was noted between atenolol area under the concentration-time curve (AUC) and change in fasting glucose level when adjusted for covariates (p=0.0025); the effect was strongest in women. No significant relationship was noted between plasma atenolol concentration and glucose AUC during oral glucose tolerance testing (r=0.08, p=0.78), nor between atenolol AUC and change in triglyceride levels (r=0.13, p=0.63). Higher plasma atenolol exposure may be a risk factor for an increase in fasting plasma glucose level during atenolol treatment. These findings require confirmation in a larger sample.

Effect of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) micelles on pharmacokinetics and intestinal toxicity of irinotecan hydrochloride: potential involvement of breast cancer resistance protein (ABCG2)

Intestinal toxicity and low levels of systemic drug exposure are among the major problems associated with tumour therapy. We have developed poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) micelles loaded with irinotecan hydrochloride (CPT-11) hoping to decrease CPT-11-induced intestinal toxicity while increasing its systemic exposure. In addition, we have investigated the potential involvement of breast cancer resistance protein (BCRP) in biliary excretion, pharmacokinetics, and intestinal toxicity of CPT-11. PEO-PPO-PEO micelles were prepared using PEO(20)-PPO(70)-PEO(20) and lecithin. The effect of PEO-PPO-PEO micelles on BCRP-mediated cellular accumulation and transport efflux of CPT-11 was evaluated in MDCKII/BCRP cells. The biliary excretion, intestinal damage, and pharmacokinetic study of CPT-11-loaded PEO-PPO-PEO micelles were investigated in rats. The obtained micelles could effectively inhibit BCRP-mediated CPT-11 efflux in MDCKII/BCRP cells, and significantly decrease the drug biliary excretion in rats. Moreover, intestinal toxicity, assessed by microscopic examination of pathological damage, was ameliorated in rats injected with PEO-PPO-PEO micelles compared with rats injected with CPT-11 alone. Treatment with PEO-PPO-PEO micelles resulted in prolonged circulation time in blood and increased bioavailability of CPT-11 and SN-38 (7-ethyl-10-hydroxycamptothecin). PEO-PPO-PEO micelles were identified as promising carriers able to reduce intestinal toxicity and increase antitumour therapeutic effect of CPT-11. The study indicated a potential involvement of BCRP in CPT-11 pharmacokinetics and CPT-11-induced intestinal toxicity.

Long-Term Tolerability and Serum Concentration of Bevacizumab (Avastin) when Injected in Newborn Rabbit Eyes

PURPOSE. To test the long-term effects and systemic exposure level after single or multiple bevacizumab (Avastin) intravitreal injections in newborn rabbit eyes. METHODS. Four groups of newborn New Zealand rabbits received a single intravitreal bevacizumab injection at a concentration of 1.25 mg/0.05 mL at the ages of 2 (group 1), 4 (group 2), 6 (group 3), and 12 (group 5) weeks. The other group of rabbits (group 4) received three consecutive injections of bevacizumab at a concentration of 1.25 mg/0.05 mL at weeks 2, 6, and 10. Eight days after injection, the serum concentration of bevacizumab was determined in groups 1, 2, 3, and 5. Morphologic and functional changes were evaluated 12 months after bevacizumab injection. RESULTS. Twelve months after either single or multiple intravitreal injections of bevacizumab, newborn rabbit eyes showed no significant differences compared with control eyes on examination with funduscopy, histopathology, or electroretinogram. The serum concentrations when the injections were performed at the ages of 2 (19.4 +/- 8.1 microg/mL) and 4 (10.2 +/- 2.3 microg/mL) weeks were significantly higher than the serum level detected when the injection was performed at 12 weeks of age (2.8 +/- 1.2 microg/mL, P = 0.02 and P = 0.024, respectively). CONCLUSIONS. After 1 year, single and three consecutive intravitreal injections of 1.25 mg bevacizumab in newborn rabbit eyes are well tolerated. Systemic exposure is higher when the injection is performed at an early age.

Synthesis and in vitro evaluation of bisphosphonated glycopeptide prodrugs for the treatment of osteomyelitis

As therapeutic agents of choice in the treatment of complicated infections, glycopeptide antibiotics are often preferentially used in cases of osteomyelitis, an infection located in bone and notoriously difficult to successfully manage. Yet frequent and heavy doses of these systemically administered antibiotics are conventionally prescribed to obtain higher antibiotic levels in the bone and reduce the high recurrence rates. Targeting antibiotics to the bone after systemic administration would present at least three potential advantages: (i) greater efficacy, by concentrating the therapeutic agent in bone; (ii) greater convenience, through a reduction in the frequency of administration; and (iii) greater safety, by reducing the levels of systemic drug exposure. We present here the design, synthesis and in vitro evaluation of eight prodrugs of the glycopeptide antibacterial agents vancomycin and oritavancin taking advantage of the affinity of the bisphosphonate group for bone for delivery to osseous tissues.

鼻噴霧用ステロイド薬デキサメタゾンシペシル酸エステル（ＮＳ‐１２６Ｃ）の第Ｉ相試験―単回および反復投与による第Ｉ相試験―

Dexamethasone cipecilate (NS-126C), a new steroid nasal spray in powder form, is effective in once-a-day administration. We conducted a placebo-controlled, double-blind phase I clinical study in single administration at 50 μg, 100 μg, 200 μg, or 400 μg and repeated administration at 200 μg or 400 mg once a day for 14 days in healthy adults to determine NS-126C safety and pharmacokinetics. An analysis of subjective symptoms, objective findings, anterior rhinoscopy, laboratory tests, adrenal function tests, physical examination, throat or nasal fungal tests, and nasal ciliary function tests showed only 1 adverse event for which a causal relationship to the study drug could not be ruled out, i.e. 1 case of mild throat discomfort in 1 subject given the drug at 100 μg in the single-dose study. No adverse effect on adrenal function was observed. In pharmacokinetic examination, plasma levels of the unchanged drug and its principal metabolite, DX-17-CPC, and the level of unchanged drug in urine were less than the quantitation limit of <16 pg/ml in all subjects. DX-17-CPC was detected in urine at and after 120 hours from initial administration in the repeated-dose study, but was low in concentration at less than 3 times the quantitation limit. These findings confirmed the safety of NS-126C at 400 μg, once a day, for 14 days, with only extremely low levels of systemic exposure demonstrated.

Metabolites in Safety Testing: Issues and Approaches to the Safety Evaluation of Human Metabolites in a Drug that is Extensively Metabolized

In 2008 the Food and Drug Administration (FDA) modified its standard for evaluating toxicity of drug metabolites defining metabolites of concern as those that are detected circulating at more than 10% of the systemic exposure level of the parent compound at steady state. GSK1018921, a novel glycine transporter 1 inhibitor, was extensively metabolized in humans, with parent compound accounting for 12% and 1% of circulating drug related material after single and repeat dose, respectively. Since the parent was present at low relative concentrations, all fifteen metabolites detected in human plasma, met the 10% metabolites in safety testing (MIST) criterion, and therefore might require extensive quantification and further evaluation. At least thirteen metabolites warranted non-clinical characterization since they were either observed at significantly greater levels in humans than in preclinical species or they were not detected in animals. However the application of alternative strategies to 2008 FDA MIST guidance, such as those suggested by scientific literature and by the recent revision of the International Conference of Harmonisation (ICH) M3 guidance which recommended providing safety coverage for metabolites greater than 10% of total drug related material, allowed us to focus on one metabolite for additional safety evaluation.

An intranasal irritation assessment of antibacterial ointment alone or in combination with mupirocin versus Bactroban Nasal ® in rabbits

The purpose of this study was to evaluate the potential irritating effects and the systemic exposure level of an antibacterial ointment containing REP8839 as a single agent or in combination with mupirocin versus Bactroban Nasal ® in rabbits. Additionally, the reversibility of REP8839 effects during a 14-day recovery period was assessed. Five treatment groups of six male and six female New Zealand White rabbits received dose levels of 1%, 2%, and 4% REP8839, 2% Bactroban Nasal ®, or 2% REP8839/2% mupirocin combination. One additional group of six animals/sex served as the control and received the vehicle, Petrolatum/Softisan ® 649. The test article or vehicle was administered to all groups via topical administration to the external nares, twice a day (approx. 8 h intervals between the doses) for 21 consecutive days, at a dose volume of 100 μL per nare/dose for a total of 400 μL per day (200 μL per nare). Two animals/sex/group were maintained for a 14-day recovery period. The external nares were reflected back and the mucosal lining was evaluated and scored for erythema and edema within 30–60 min following the first dose each day. Blood samples were collected from all animals at designated time points on Day 21 of the study to assess systemic exposure levels. Cross-sectioning of the nasal tract was conducted in all the groups for microscopic evaluation. Mucosal scoring of the nares did not reveal any edema or erythema in any of the dose groups with the antibacterial alone, with the combination product, or with Bactroban Nasal ®. Mean body weights and food consumption were not adversely impacted by the test articles. Minimal plasma exposure was observed in the rabbits (<5 ng/mL). The REP8839 groups did appear to have dose-responsive exposure (from below the limit of quantitation to 5 ng/mL with 1%, 2%, and 4% REP8839, respectively). Microscopic changes on the nasal sectioning noted in these animals were infrequent and considered incidental findings unrelated to administration of the test articles. In conclusion doses of up to 4% of REP8839 ointment as a single agent or 2% in the combination product, as well as 2% Bactroban Nasal ®, were not found to induce mucosal irritation when applied topically to the external nares twice a day for 21 consecutive days. Additionally, no delayed effects were observed in the recovery animals.

Acute toxicity and toxicokinetics of dipfluzine hydrochloride, a novel calcium channel blocker

Dipfluzine hydrochloride, diphenylpiperazine calcium channel blocker, is a promising candidate to treat ischemic stroke. The purpose of the study is to evaluate the acute toxicity and toxicokinetics of dipfluzine hydrochloride after single intravenous doses in rats. Acute toxicity study was performed in rats at doses of 5, 6, 10, 15, 25, 30, 35, and 40 mg/kg. Concentrations of dipfluzine in plasma and tissues were determined with a reverse-phase HPLC method after single doses of 5, 15 and 30 mg/kg. The results demonstrated that no-observed-adverse-effect level (NOAEL), lowest-observed-adverse-effect level (LOAEL), maximal tolerance dose (MTD), and minimal lethal dose (MLD) were respectively 5, 6, 30, 35 mg/kg for i.v. administration of dipfluzine hydrochloride. The toxicokinetic study revealed that the severity of toxicity was linear with the level of systemic exposure. The highest tissue exposure was detected in lung tissue and it may primarily contribute to the pulmonary congestion in dead rats. Longer elimination half-lives of dipfluzine in kidney, brain, liver, and pancreas imply a possible accumulation of dipfluzine in these tissues for long-term exposure. In addition, a temporary impairment in liver and heart was observed for clinical chemistry in 30 mg/kg dose group. The findings will help to design further studies to characterize the repeat-dose toxicity of dipfluzine hydrochloride.

Preclinical Pharmacokinetics of a HepDirect Prodrug of a Novel Phosphonate-Containing Thyroid Hormone Receptor Agonist

The prodrug [(2R,4S)-4-(3-chlorophenyl)-2-[(3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl)phenoxy)methyl]-2-oxido-[1,3,2]-dioxaphosphonane (MB07811)] of a novel phosphonate-containing thyroid hormone receptor agonist [3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl)phenoxylmethylphosphonic acid (MB07344)] is the first application of the HepDirect liver-targeting approach to a non-nucleotide agent. The disposition of MB07811 was characterized in rat, dog, and monkey to assess its liver specificity, which is essential in limiting the extrahepatic side effects associated with this class of lipid-lowering agents. MB07811 was converted to MB07344 in liver microsomes from all species tested (CL(int) 1.23-145.4 microl/min/mg). The plasma clearance and volume of distribution of MB07811 matched or exceeded 1 l/h/kg and 3 l/kg, respectively. Although absorption of prodrug was good, its absolute oral bioavailability as measured systemically was low (3-10%), an indication of an extensive hepatic first-pass effect. This effect was confirmed by comparison of systemic exposure levels of MB07811 after portal and jugular vein administration to rats, which demonstrated a hepatic extraction ratio of >0.6 with liver CYP3A-mediated conversion to MB07344 being a major component. The main route of elimination of MB07811 and MB07344 was biliary, with no evidence for enterohepatic recirculation of MB07344. Similar metabolic profiles of MB07811 were obtained in liver microsomes across the species tested. Tissue distribution and whole body autoradiography confirmed that the liver is the major target organ of MB07811 and that conversion to MB07344 was high in the liver relative to that in other tissues. Hepatic first-pass extraction and metabolism of MB07811, coupled with possible selective distribution of MB07811-derived MB07344, led to a high degree of liver targeting of MB07344.

Markers of Systemic Bacterial Exposure in Periodontal Disease and Cardiovascular Disease Risk: A Systematic Review and Meta‐Analysis

Recent meta-analyses reported a weak association between periodontal disease (PD) on clinical examination and cardiovascular disease (CVD). Systemic bacterial exposure from periodontitis, which correlates poorly with the clinical examination, has been proposed as the more biologically pertinent risk factor. The purpose of this study was to review and analyze the association between PD with elevated systemic bacterial exposure and CVD. We searched in the PubMed, Cochrane Controlled Trials Register, EMBASE, and SCOPUS databases for all literature examining PD and CVD. From 10 selected publications, we extracted 12 cohort (N = 5) and cross-sectional (N = 7) studies and included 11 of these in a meta-analysis. With stratified analyses, this resulted in 14 analyses of coronary heart disease (CHD; N = 7), stroke (N = 4), and carotid intima-medial thickening (CIMT; N = 3) as a measure of early atherosclerosis. Systemic bacterial exposure was measured by periodontal bacterial burden (N = 1), periodontitis-specific serology (N = 12), or C-reactive protein (N = 1). Periodontal disease with elevated markers of systemic bacterial exposure was associated strongly with CHD compared to subjects without PD, with a summary odds ratio of 1.75 (95% confidence interval (CI): 1.32 to 2.34; P <0.001). This group was not associated with CVD events or with stroke but was associated with a significant increase in mean CIMT (0.03 mm; 95% CI: 0.02 to 0.04). Periodontal disease with elevated bacterial exposure is associated with CHD events and early atherogenesis (CIMT), suggesting that the level of systemic bacterial exposure from periodontitis is the biologically pertinent exposure with regard to atherosclerotic risk.

Local Tolerance and Systemic Safety of Pegaptanib Sodium in the Dog and Rabbit

To evaluate the local tolerance, systemic toxicity, and toxicokinetics in dogs and rabbits of pegaptanib sodium, an aptamer that targets vascular endothelial growth factor (VEGF(165)). Dogs received biweekly, bilateral, intravitreous (IVT) injections of pegaptanib sodium for 9 months at doses of 0.3 (n = 10), 1 (n = 10), or 3 mg (n = 14); 14 control dogs received phosphate-buffered saline (PBS). In rabbits, pegaptanib sodium was administered by IVT injection biweekly for 6 months at doses of 0.2 (n = 14), 0.67 (n = 14), or 2 mg (n = 18); 18 rabbits received PBS. The systemic and ocular safety of pegaptanib sodium was assessed. Assessments in both dogs and rabbits included complete ophthalmologic examinations, serum chemistry, hematology, urinalysis, and coagulation assessments, as well as gross and microscopic pathologic examination. In addition, dogs were assessed by electroretinography and electrocardiography. In a cardiovascular safety study, loading intravenous boluses and maintenance infusions of pegaptanib sodium or PBS were administered to dogs (n = 4) in an ascending dose design, with each dose level separated by 2-3 days. The pegaptanib dosing regimens were designed to achieve pegaptanib plasma concentrations of approximately 90, 270, or 900 ng/mL. There were no pegaptanib sodium-associated clinical, ophthalmologic, pathologic, or cardiovascular abnormalities at doses of pegaptanib that achieved systemic and ocular exposure levels in excess of those associated with the recommended pegaptanib IVT dosing regimen of 0.3 mg per study eye in patients with age-related macular degeneration. These studies, together with data from clinical trials, provide strong evidence that inhibition of VEGF(165) by pegaptanib in the eye is a safe therapy for the treatment of ocular neovascular disease.

Cellular uptake mechanisms and potential therapeutic utility of peptidic cell delivery vectors: Progress 2001–2006

Cell delivery vectors (CDVs) are short amphipathic and cationic peptides and peptide derivatives, usually containing multiple lysine and arginine residues. They possess inherent membrane activity and can be conjugated or complexed with large impermeable macromolecules and even microscopic particles to facilitate cell entry. Various mechanisms have been proposed but it is now becoming clear that the main port of entry into cells of such CDV constructs involves adsorptive-mediated endocytosis rather than direct penetration of the plasma membrane. It is still unclear, however, how and to what extent CDV constructs are capable of exiting endosomal compartments and reaching their intended cellular site of action, usually the cytosol or the nucleus. Furthermore, although many CDVs can mediate cellular uptake of their cargo and appear comparatively non-toxic to cells in tissue culture, the utility of CDVs for in vivo applications remains poorly understood. Whatever the mechanisms of cell entry and disposition, the overriding question as far as potential pharmacological application of CDV conjugates is concerned is whether or not a therapeutic margin can be achieved by their administration. Such a margin will only result if the intracellular concentration in the target tissues necessary to elicit the biological effect of the CDV cargo can be achieved at systemic CDV exposure levels that are non-toxic to both target and bystander cells. It is proposed that the focus of CDV research now be shifted from mechanistic in vitro studies with labeled but otherwise unconjugated CDVs to in vivo pharmacological and toxicological studies using CDV-derivatized and other cationized forms of inherently non-permeable macromolecules of true therapeutic interest.