Use of Polyamidoamine Dendrimers in Brain Diseases

Polyamidoamine (PAMAM) dendrimers are one of the smallest and most precise nanomolecules available today, which have promising applications for the treatment of brain diseases. Each aspect of the dendrimer (core, size or generation, size of cavities, and surface functional groups) can be precisely modulated to yield a variety of nanocarriers for delivery of drugs and genes to brain cells in vitro or in vivo. Two of the most important criteria to consider when using PAMAM dendrimers for neuroscience applications is their safety profile and their potential to be prepared in a reproducible manner. Based on these criteria, features of PAMAM dendrimers are described to help the neuroscience researcher to judiciously choose the right type of dendrimer and the appropriate method for loading the drug to form a safe and effective delivery system to the brain.

Phosphate binders for preventing and treating chronic kidney disease-mineral and bone disorder (CKD-MBD)

BACKGROUND

Phosphate binders are used to reduce positive phosphate balance and to lower serum phosphate levels for people with chronic kidney disease (CKD) with the aim to prevent progression of chronic kidney disease-mineral and bone disorder (CKD-MBD). This is an update of a review first published in 2011.

OBJECTIVES

The aim of this review was to assess the benefits and harms of phosphate binders for people with CKD with particular reference to relevant biochemical end-points, musculoskeletal and cardiovascular morbidity, hospitalisation, and death.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 July 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs of adults with CKD of any GFR category comparing a phosphate binder to another phosphate binder, placebo or usual care to lower serum phosphate. Outcomes included all-cause and cardiovascular death, myocardial infarction, stroke, adverse events, vascular calcification and bone fracture, and surrogates for such outcomes including serum phosphate, parathyroid hormone (PTH), and FGF23.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion and extracted study data. We applied the Cochrane 'Risk of Bias' tool and used the GRADE process to assess evidence certainty. We estimated treatment effects using random-effects meta-analysis. Results were expressed as risk ratios (RR) for dichotomous outcomes together with 95% confidence intervals (CI) or mean differences (MD) or standardised MD (SMD) for continuous outcomes.

MAIN RESULTS

We included 104 studies involving 13,744 adults. Sixty-nine new studies were added to this 2018 update.Most placebo or usual care controlled studies were among participants with CKD G2 to G5 not requiring dialysis (15/25 studies involving 1467 participants) while most head to head studies involved participants with CKD G5D treated with dialysis (74/81 studies involving 10,364 participants). Overall, seven studies compared sevelamer with placebo or usual care (667 participants), seven compared lanthanum to placebo or usual care (515 participants), three compared iron to placebo or usual care (422 participants), and four compared calcium to placebo or usual care (278 participants). Thirty studies compared sevelamer to calcium (5424 participants), and fourteen studies compared lanthanum to calcium (1690 participants). No study compared iron-based binders to calcium. The remaining studies evaluated comparisons between sevelamer (hydrochloride or carbonate), sevelamer plus calcium, lanthanum, iron (ferric citrate, sucroferric oxyhydroxide, stabilised polynuclear iron(III)-oxyhydroxide), calcium (acetate, ketoglutarate, carbonate), bixalomer, colestilan, magnesium (carbonate), magnesium plus calcium, aluminium hydroxide, sucralfate, the inhibitor of phosphate absorption nicotinamide, placebo, or usual care without binder. In 82 studies, treatment was evaluated among adults with CKD G5D treated with haemodialysis or peritoneal dialysis, while in 22 studies, treatment was evaluated among participants with CKD G2 to G5. The duration of study follow-up ranged from 8 weeks to 36 months (median 3.7 months). The sample size ranged from 8 to 2103 participants (median 69). The mean age ranged between 42.6 and 68.9 years.Random sequence generation and allocation concealment were low risk in 25 and 15 studies, respectively. Twenty-seven studies reported low risk methods for blinding of participants, investigators, and outcome assessors. Thirty-one studies were at low risk of attrition bias and 69 studies were at low risk of selective reporting bias.In CKD G2 to G5, compared with placebo or usual care, sevelamer, lanthanum, iron and calcium-based phosphate binders had uncertain or inestimable effects on death (all causes), cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. Sevelamer may lead to constipation (RR 6.92, CI 2.24 to 21.4; low certainty) and lanthanum (RR 2.98, CI 1.21 to 7.30, moderate certainty) and iron-based binders (RR 2.66, CI 1.15 to 6.12, moderate certainty) probably increased constipation compared with placebo or usual care. Lanthanum may result in vomiting (RR 3.72, CI 1.36 to 10.18, low certainty). Iron-based binders probably result in diarrhoea (RR 2.81, CI 1.18 to 6.68, high certainty), while the risks of other adverse events for all binders were uncertain.In CKD G5D sevelamer may lead to lower death (all causes) (RR 0.53, CI 0.30 to 0.91, low certainty) and induce less hypercalcaemia (RR 0.30, CI 0.20 to 0.43, low certainty) when compared with calcium-based binders, and has uncertain or inestimable effects on cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. The finding of lower death with sevelamer compared with calcium was present when the analysis was restricted to studies at low risk of bias (RR 0.50, CI 0.32 to 0.77). In absolute terms, sevelamer may lower risk of death (all causes) from 210 per 1000 to 105 per 1000 over a follow-up of up to 36 months, compared to calcium-based binders. Compared with calcium-based binders, lanthanum had uncertain effects with respect to all-cause or cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification and probably had reduced risks of treatment-related hypercalcaemia (RR 0.16, CI 0.06 to 0.43, low certainty). There were no head-to-head studies of iron-based binders compared with calcium. The paucity of placebo-controlled studies in CKD G5D has led to uncertainty about the effects of phosphate binders on patient-important outcomes compared with placebo.It is uncertain whether the effects of binders on clinically-relevant outcomes were different for patients who were and were not treated with dialysis in subgroup analyses.

AUTHORS' CONCLUSIONS

In studies of adults with CKD G5D treated with dialysis, sevelamer may lower death (all causes) compared to calcium-based binders and incur less treatment-related hypercalcaemia, while we found no clinically important benefits of any phosphate binder on cardiovascular death, myocardial infarction, stroke, fracture or coronary artery calcification. The effects of binders on patient-important outcomes compared to placebo are uncertain. In patients with CKD G2 to G5, the effects of sevelamer, lanthanum, and iron-based phosphate binders on cardiovascular, vascular calcification, and bone outcomes compared to placebo or usual care, are also uncertain and they may incur constipation, while iron-based binders may lead to diarrhoea.

Anticancer activity of some polyamine derivatives on human prostate and breast cancer cell lines

The aim of this study was to expand our knowledge about anticancer activity of some polyamine derivatives with quinoline or chromane as terminal moieties. Tested compounds were evaluated in vitro towards metastatic human prostate adenocarcinoma (PC3), human carcinoma (DU145) and mammary gland adenocarcinoma (MCF7) cell lines. Cell viability was estimated on the basis of mitochondrial metabolic activity using water-soluble tetrazolium WST1 to establish effective concentrations of the tested compounds under experimental conditions. Cytotoxic potential of polyamine derivatives was determined by the measurement of lactate dehydrogenase activity released from damaged cells, changes in mitochondrial membrane potential, the cell cycle distribution analysis and apoptosis assay. It was revealed that the tested polyamine derivatives differed markedly in their antiproliferative activity. Bischromane derivative 5a exhibited a rather cytostatic than cytotoxic effect on the tested cells, whereas quinoline derivative 3a caused changes in cell membrane integrity, inhibited cell cycle progression, as well as induced apoptosis of prostate and breast cancer cells which suggest its potential application in cancer therapy.

Evaluation of the Antimicrobial Activity of Cationic Polymers against Mycobacteria: Toward Antitubercular Macromolecules

Antimicrobial resistance is a global healthcare problem with a dwindling arsenal of usable drugs. Tuberculosis, caused by Mycobacterium tuberculosis, requires long-term combination therapy and multi- and totally drug resistant strains have emerged. This study reports the antibacterial activity of cationic polymers against mycobacteria, which are distinguished from other Gram-positive bacteria by their unique cell wall comprising a covalently linked mycolic acid-arabinogalactan-peptidoglycan complex (mAGP), interspersed with additional complex lipids which helps them persist in their host. The present study finds that poly(dimethylaminoethyl methacrylate) has particularly potent antimycobacterial activity and high selectivity over two Gram-negative strains. Removal of the backbone methyl group (poly(dimethylaminoethyl acrylate)) decreased antimycobacterial activity, and poly(aminoethyl methacrylate) also had no activity against mycobacteria. Hemolysis assays revealed poly(dimethylaminoethyl methacrylate) did not disrupt red blood cell membranes. Interestingly, poly(dimethylaminoethyl methacrylate) was not found to permeabilize mycobacterial membranes, as judged by dye exclusion assays, suggesting the mode of action is not simple membrane disruption, supported by electron microscopy analysis. These results demonstrate that synthetic polycations, with the correctly tuned structure are useful tools against mycobacterial infections, for which new drugs are urgently required.

PAMAM Dendrimers and Branched Polyethyleneglycol (Nanoparticles) Prodrugs of (-)-β-D-(2R, 4R)-dioxolane-thymine (DOT) and Their Anti-HIV Activity

The synthesis, characterization, anti-HIV activity and cytotoxicity of dendrimers of (–)-β-D-(2 R,4 R)-dioxolane-thymine (DOT) and polyethylene glycol (PEG)–DOT conjugates are described. Dendrimers in this study were polyamidoamine (PAMAM) generation 2.0, 3.0, 5.0 and 6.0, along with 8.0-branched PEG with a molecular weight of 40 kDa. DOT was attached to PAMAM dendrimers or branched PEG via ester or phosphate groups. Size exclusion chromatography was used to purify the dendrimers and PEG conjugates, which were characterized by NMR and MALDI—TOF mass spectrometry. The synthesized PAMAM dendrimers and PEG conjugates were evaluated for anti-HIV activity against HIV-1LAI in primary human peripheral blood mononuclear cells (PBMCs) and cytotoxicity in PBMCs, CEM and Vero cells. PAMAM dendrimers of DOT with ester linkages and particularly phosphate linkers showed an increase in anti-HIV potency in comparison with DOT alone (140- and 56-fold, respectively). Unfortunately, the PAMAM dendrimers also exhibited increased cytotoxicity. Anti-HIV activity of PEG—DOT conjugates was found to be lower than that of DOT.

Self-Assembled Gold Nanoclusters for Bright Fluorescence Imaging and Enhanced Drug Delivery

Nanoparticles combining enhanced cellular drug delivery with efficient fluorescence detection are important tools for the development of theranostic agents. Here, we demonstrate this concept by a simple, fast, and robust protocol of cationic polymer-mediated gold nanocluster (Au NCs) self-assembly into nanoparticles (NPs) of ca. 120 nm diameter. An extensive characterization of the monodisperse and positively charged NPs revealed pH-dependent swelling properties, strong fluorescence enhancement, and excellent colloidal and photostability in water, buffer, and culture medium. The versatility of the preparation is demonstrated by using different Au NC surface ligands and cationic polymers. Steady-state and time-resolved fluorescence measurements give insight into the aggregation-induced emission phenomenon (AIE) by tuning the Au NC interactions in the self-assembled nanoparticles using the pH-dependent swelling. In vitro studies in human monocytic cells indicate strongly enhanced uptake of the NPs compared to free Au NCs in endocytic compartments. The NPs keep their assembly structure with quite low cytotoxicity up to 500 μg Au/mL. Enhanced drug delivery is demonstrated by loading peptides or antibodies in the NPs using a one-pot synthesis. Fluorescence microscopy and flow cytometry confirmed intracellular colocalization of the biomolecules and the NP carriers with a respective 1.7-fold and 6.5-fold enhanced cellular uptake of peptides and antibodies compared to the free biomolecules.

Cardiovascular effects of sevelamer in stage 3 CKD

Serum phosphate independently predicts cardiovascular mortality in the general population and CKD, even when levels are in the normal range. Associations between serum phosphate, arterial stiffness, and left ventricular (LV) mass suggest a possible pathophysiological mechanism, potentially mediated by the phosphaturic hormone fibroblast growth factor-23 (FGF-23). To what extent the phosphate binder sevelamer modulates these effects is not well understood. In this single-center, randomized, double-blind, placebo-controlled trial, we enrolled 120 patients with stage 3 nondiabetic CKD. After a 4-week open-label run-in period, during which time all patients received sevelamer carbonate, we randomly assigned 109 patients to sevelamer (n=55) or placebo (n=54) for an additional 36 weeks. We assessed LV mass and systolic and diastolic function with cardiovascular magnetic resonance imaging and echocardiography, and we assessed arterial stiffness by carotid-femoral pulse wave velocity. The mean age was 55 years, and the mean eGFR was 50 ml/min per 1.73 m(2). After 40 weeks, we found no statistically significant differences between sevelamer and placebo with regard to LV mass, systolic and diastolic function, or pulse wave velocity. Only 56% of subjects took ≥ 80% of prescribed therapy; in this compliant subgroup, treatment with sevelamer associated with lower urinary phosphate excretion and serum FGF-23 but not serum phosphate, klotho, vitamin D, or cardiovascular-related outcomes of interest. In conclusion, this study does not provide evidence that sevelamer carbonate improves LV mass, LV function, or arterial stiffness in stage 3 nondiabetic CKD.

Production of toxic pavettamine and pavettamine conjugates in the gousiekte-causing Fadogia homblei plant and its relation to the bacterial endosymbiont

Plant poisoning of livestock is responsible for considerable economic losses in southern Africa. Six plant species of the Rubiaceae family are known to cause gousiekte, a cardiac syndrome of ruminants induced by ingestion of the toxic compound pavettamine. Progress in understanding the etiology of this disease is largely hampered by the variable toxicity of the plants and the absence of a quantification method for pavettamine. The pavettamine concentration in leaf samples of Fadogia homblei, a known gousiekte causing plant, was analyzed by mass-spectrometry. In the most apical leaf pair, the highest concentration of pavettamine was detected. Distal leaves contained progressively less pavettamine. Besides a significant amount of free pavettamine, most pavettamine was found to occur in a conjugated form. To which molecules the pavettamine is conjugated remains unknown as is the function of conjugated pavettamine in the development of gousiekte. All know gousiekte-causing plants contain symbiotic bacteria in their leaves; it was hypothesized that these bacteria might be involved in the production of pavettamine. However, analysis of in vitro cultures of the F. homblei endosymbiont revealed no production of pavettamine. Pavettamine is therefore not produced by the bacteria alone. It is either the product of the interaction with the plant or solely produced by the host.

Phosphate binders for preventing and treating bone disease in chronic kidney disease patients

BACKGROUND

Phosphate binders are widely used to lower serum phosphorus levels in people with chronic kidney disease (CKD) but their impact in CKD remains controversial.

OBJECTIVES

To review the effects of various phosphate binders on biochemical and patient-level end-points in CKD stages 3 to 5D.

SEARCH STRATEGY

In March 2010 we searched MEDLINE, EMBASE, the Cochrane Renal Group's Specialised Register and CENTRAL for relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs that assessed the effects of various phosphate binders in adults with CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed search results and extracted data. Results were expressed as mean differences (MD) for continuous outcomes and risk ratios (RR) for dichotomous outcomes with 95% confidence intervals (CI) using a random-effects model.

MAIN RESULTS

Sixty studies (7631 participants) were included. There was no significant reduction in all-cause mortality (10 studies, 3079 participants: RR 0.73, 95% CI 0.46 to 1.16), or serum calcium by phosphorus (Ca x P) product with sevelamer hydrochloride compared to calcium-based agents. There was a significant reduction in serum phosphorus (16 studies, 3126 participants: MD 0.23 mg/dL, 95% CI 0.04 to 0.42) and parathyroid hormone (PTH) (12 studies, 2551 participants; MD 56 pg/mL, 95% CI 26 to 84) but a significant increase in the risk of hypercalcaemia (12 studies, 1144 participants: RR 0.45, 95% CI 0.35 to 0.59) with calcium-based agents compared to sevelamer hydrochloride. There was a significant increase in the risk of adverse gastrointestinal events with sevelamer hydrochloride in comparison to calcium salts (5 studies, 498 participants: RR 1.58, 95% CI 1.11 to 2.25). Compared with calcium-based agents, lanthanum significantly reduced serum calcium (2 studies, 122 participants: MD -0.30 mg/dL, 95% CI -0.64 to -0.25) and the Ca x P product, but not serum phosphorus levels. The effects of calcium acetate on biochemical end-points were similar to those of calcium carbonate. The phosphorus lowering effects of novel agents such as ferric citrate, colestilan and niacinamide were only reported in a few studies.

AUTHORS' CONCLUSIONS

Available phosphate-binding agents have been shown to reduce phosphorus levels in comparison to placebo. However, there are insufficient data to establish the comparative superiority of novel non-calcium binding agents over calcium-containing phosphate binders for patient-level outcomes such as all-cause mortality and cardiovascular end-points in CKD.

Sevelamer reduces the efficacy of many other drugs

(1) Sevelamer, a phosphate-binding polymer, is used to treat hyperphosphataemia in patients with chronic renal failure. Pharmacokinetic studies and some clinical reports have shown that sevelamer binds many drugs, including furosemide, ciclosporin and tacrolimus, thus making them less effective; (2) It is best to take sevelamer some time before or after other drugs.

A Comparison of Sevelamer Hydrochloride with Calcium Acetate on Biomarkers of Bone Turnover in Hemodialysis Patients

OBJECTIVE

To evaluate the influence of sevelamer hydrochloride and calcium acetate on biomarkers of bone turnover in patients with hyperphosphatemia receiving hemodialysis.

METHODS

In this prospective, open-label, randomized, active-controlled study, 70 patients (38 men and 32 women) with hyperphosphatemia (serum phosphorus level >6.0 mg/dL) underwent a two-week washout period and were randomly selected to receive sevelamer hydrochloride (n = 37) or calcium acetate (n = 33) for eight weeks. Changes in serum levels of intact parathyroid hormone (iPTH), alkaline phosphatase (Alk-P), phosphorus, and calcium were measured and compared.

RESULTS

After eight weeks of treatment, calcium acetate lowered iPTH levels significantly more than sevelamer hydrochloride did (-178.0 vs. -69.0 pg/mL, p = 0.0019). Levels of Alk-P were significantly elevated in patients given sevelamer hydrochloride compared with levels in those given calcium acetate treatment (24.09 vs. 7.45 U/L, p = 0.0014). Changes in serum phosphorus levels did not differ between sevelamer hydrochloride (-1.93 mg/dL) and calcium acetate (-2.5 mg/dL) at the end of the study (p = 0.0514). Changes in the calcium and phosphorous product did not significantly differ between the sevelamer-hydrochloride group (-18.06 mg2/dL2) and the calcium-acetate group (-19.05 mg2/dL2, p = 0.6764). Fifteen patients (45.5%) treated with calcium acetate had hypercalcemia (serum-adjusted calcium level >10.5 mg/dL); the rate was significantly higher than that of patients treated with sevelamer (five [13.5%] of 37, p = 0.0039).

CONCLUSION

Treatment with sevelamer hydrochloride had the advantage of maintaining stable iPTH levels and elevating Alk-P levels while lowering serum phosphorus levels and calcium-phosphorous product.

[To facilitate the compliance of phosphate binder for the control of hyperphosphatemia in chronic kidney disease patients]

Despite phosphate binders are necessary for the control of hyperphosphatemia in chronic kidney disease, adherence to medication tends to be low due to the lack of subjective symptoms of patients. Such non- adherence often causes compromised health outcomes. Key factors affecting adherence of phosphate binders are being the occurrence of side effects such as constipation, taking a lot of tablets, being lack of motive for medication. Thus, to facilitate the adherence of phosphate binders, it is recommended to select medication properly according to the situation of individual patients, to consider the side effect reduction and to raise motive of adherence by educational interventions and drug counseling.

A review article: sevelamer hydrochloride and metabolic acidosis in dialysis patients

Sevelamer hydrochloride is a phosphate binder and its effectiveness to reduce the cardiovascular mortality of dialysis patients has been tested. Sevelamer hydrochloride also contains chlorine, so a decrease in bicarbonate due to chlorine load was anticipated and metabolic acidosis thought to associate with sevelamer hydrochloride has been reported in some papers. We reported that sevelamer hydrochloride exacerbated metabolic acidosis in hemodialysis patients, depending on the dosage. Also a Japanese nationwide survey suggested that sevelamer hydrochloride usage potentially aggravates acidosis in dialysis patients. A multi-institute research study by Edmung et al. has shown that metabolic acidosis, with serum CO2 below 17.5 mmol/L, is by itself associated with increased risk of death in dialysis patients. Furthermore, the Dialysis Outcomes and Practice Patterns Study (DOPPS) revealed that both high (> 27 mmol/L) and low (< or = 17 mmol/L) serum bicarbonate (total CO2) levels were associated with increased risk for mortality and hospitalization. There has not been any significant evidence to show that sevelamer hydrochloride has reduced the cardiovascular mortality of dialysis patients compared with calcium-based binder. Clinicians should check not only the level of chlorine but also the level of total CO2 or bicarbonate during the treatment with sevelamer hydrochloride, and control metabolic acidosis.

Occupational allergic contact dermatitis from epoxy resin in a golf club repairman

A golfer presented with facial and hand eczema. He had exacerbations of his hand eczema prior to golf tournaments. Being an authorized golf club repairman, he had been working with a two-part glue containing an epoxy resin (ER) based on diglycidyl ether of bisphenol A (DGEBA) and the hardener diethylenetriamine (DETA) for approximately 4 years before he developed any skin problems. He was patch-tested with the standard, which contains an ER based on DGEBA (DGEBA-R), epoxy (containing DETA), and rubber glove series and had positive reactions to DGEBA-R only. Other work materials (a latex glove, a golf glove made of leather, and part of the handle of his own golf club "as is" and in a methyl tert-butyl ether extract) were tested, with negative results. Allergic contact dermatitis from ER affects the skin by direct contact; the dermatitis is usually localized to the hands and forearms. If the face and eyelids are involved, the dermatitis may be due to exposure to airborne hardeners or reactive diluents, exposure to airborne dust from residual monomers, or ectopic allergic reactions. Our repairman had sandpapered an old glued surface, which may have led to possible airborne dust formation, thus explaining the facial eczema. Therefore, a worker with contact allergy to ER may continue working provided the skin is protected from contamination.

Efficacy and tolerability of sevelamer carbonate in hyperphosphatemic patients who have chronic kidney disease and are not on dialysis

BACKGROUND AND OBJECTIVES

Sevelamer carbonate is an improved, buffered form of sevelamer hydrochloride developed for the treatment of hyperphosphatemia in patients with chronic kidney disease. This study investigated the ability of sevelamer carbonate to control serum phosphorous in hyperphosphatemic patients who had chronic kidney disease and were not on dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was an open-label, dosage-titration study. Patients with serum phosphorus > or =5.5 mg/dl were enrolled (n = 46). Sevelamer carbonate was administered for 8 wk. Patients were supplemented with native vitamin D (400 IU). The primary efficacy parameter was the change from baseline in serum phosphorous. Secondary measures included the percentage of serum phosphorus responders; changes in serum lipids, calcium-phosphorus product, and bicarbonate; and safety and tolerability.

RESULTS

Sevelamer carbonate treatment resulted in a statistically significant decrease in mean serum phosphorous levels from baseline to end of treatment. A total of 75% of patients with stage 4 and 70% of patients with stage 5 chronic kidney disease achieved the target serum phosphorous at the end of treatment. There were statistically significant decreases in serum calcium-phosphorus product and total and low-density lipoprotein cholesterol at the end of treatment and a statistically significant increase in mean serum bicarbonate levels (from 16.6 to 18.2 mEq/L). Sevelamer carbonate was well tolerated.

CONCLUSIONS

Sevelamer carbonate is an effective and well-tolerated therapy for the control of phosphorous levels in hyperphosphatemic patients who have chronic kidney disease and are not on dialysis.

A comparative review of the efficacy and safety of established phosphate binders: calcium, sevelamer, and lanthanum carbonate

BACKGROUND

Obstacles to successful management of hyperphosphatemia in chronic kidney disease include inadequate control of dietary phosphate and non-compliance with phosphate-binder therapy. Three major classes of phosphate binders include calcium-based binders, sevelamer HCl, and lanthanum carbonate.

SCOPE

A literature search was performed using MEDLINE and EMBASE databases to identify clinical trials from January 1966 to May 2007 comparing classes of phosphate binders with regard to efficacy, safety, compliance, or pharmacoeconomics. Search terms included lanthanum AND sevelamer, lanthanum AND calcium, and sevelamer AND calcium. A total of 1372 articles were identified in the search, with 125 review articles and clinical trials of interest identified.

FINDINGS

Calcium-based binders are effective, but their potential to contribute to total body calcium overload and vascular calcification is an important long-term clinical concern. Sevelamer HCl is effective in reducing serum phosphate, has no systemic absorption, and does not increase total body calcium load. However, sevelamer HCl binds bile acids, is not an efficient phosphate binder in an acidic environment, and contributes to metabolic acidosis. Lanthanum carbonate is a potent and selective phosphate binder that retains high affinity for phosphate over a wide pH range, does not bind bile acids or contribute to metabolic acidosis, and has the potential to reduce pill burden and increase patient compliance compared with other phosphate binders.

CONCLUSIONS

All three classes of phosphate binders are effective at reducing serum phosphate levels. Lanthanum carbonate may result in increased adherence by decreasing the pill burden.

Sevelamer hydrochloride in peritoneal dialysis patients: results of a multicenter cross-sectional study

BACKGROUND

Sevelamer hydrochloride is a phosphate binder widely employed in hemodialysis patients. Until now, information about its efficacy and safety in peritoneal dialysis patients has been scarce.

PATIENTS AND METHODS

In September 2005 a cross-sectional study of demographic, biochemical, and therapeutic data of patients from 10 peritoneal dialysis units in Catalonia and the Balearic Islands, Spain, was conducted.

RESULTS

We analyzed data from 228 patients. At the time of the study, 128 patients (56%) were receiving sevelamer. Patients receiving sevelamer were younger (p < 0.01), showed a longer period of time on dialysis (p < 0.01), and had a lower Charlson Comorbidity Index (p < 0.01). Serum calcium and intact parathyroid hormone levels were not different between the two groups, while phosphate levels <5.5 mg/dL were observed more frequently in patients not receiving sevelamer (79% vs 61%, p < 0.01). Serum total cholesterol (167 +/- 41 vs 189 +/- 42 mg/dL, p < 0.01) and low density lipoprotein (LDL) cholesterol (90 +/- 34 vs 109 +/- 34 mg/dL, p < 0.01), but not high density lipoprotein cholesterol or triglycerides, were lower in sevelamer-treated patients. Moreover, sevelamer-treated patients displayed a higher serum albumin (38 +/- 5 vs 36 +/- 4 g/L, p < 0.01) and a lower C-reactive protein (4.9 +/- 12.8 vs 8.8 +/- 15.7 mg/L, p < 0.01). Blood bicarbonate levels <22 mmol/L were observed more frequently in patients receiving sevelamer (22% vs 5%, p < 0.01). Logistic regression analysis adjusting by confounding variables confirmed that sevelamer therapy was associated with serum total cholesterol <200 mg/dL [relative risk (RR): 2.77, 95% confidence interval (CI): 1.44 - 5.26, p = 0.002] and blood bicarbonate <22 mmol/L (RR: 8.5, 95% CI: 2.6 - 27.0, p < 0.001), but not with serum phosphate >5.5 mg/dL, calcium-phosphate product >55 mg(2)/dL(2), serum albumin <35 g/L, or C-reactive protein >5 mg/L.

CONCLUSIONS

This uncontrolled cross-sectional study in peritoneal dialysis patients showed that sevelamer hydrochloride treatment allows an adequate serum phosphate level in about 60% of patients and significantly reduces total and LDL-cholesterol levels. Since this treatment is associated with metabolic acidosis in 22% of patients, we recommend close monitoring of bicarbonate levels in this group of patients until the clinical significance of this result is clarified.

In Vivo evaluation of a PAMAM-cystamine-(Gd-DO3A) conjugate as a biodegradable macromolecular MRI contrast agent

Macromolecular Gd(III) chelates are superior magnetic resonance imaging (MRI) contrast agents for blood pool and tumor imaging. However, their clinical development is limited by the safety concerns related to the slow excretion and long-term gadolinium tissue accumulation. A generation 6 PAMAM Gd(III) chelate conjugate with a cleavable disulfide spacer, PAMAM-G6-cystamine-(Gd-DO3A), was prepared as a biodegradable macromolecular MRI contrast agent with rapid excretion from the body. T(1) and T(2) relaxivities of the contrast agent were 11.6 and 13.3 mM(-1)sec(-1) at 3T, respectively. Blood pool and tumor contrast enhancement of the agent were evaluated in female nude mice bearing MDA-MB-231 human breast carcinoma xenografts with a nondegradable conjugate PAMAM-G6-(Gd-DO3A) as a control. PAMAM-G6-cystamine-(Gd-DO3A) resulted in significant contrast enhancement in the blood for about 5 mins, and Gd-DO3A was released from the conjugate and rapidly excreted via renal filtration after the disulfide spacer was cleaved. The nondegradable control had much longer blood circulation and excreted more slowly from the body. PAMAM-G6-cystamine-(Gd-DO3A) also resulted in more prominent tumor contrast enhancement than the control. However, PAMAM-G6-cystamine-(Gd-DO3A) demonstrated high toxicity due to the intrinsic toxicity of PAMAM dendrimers. In conclusion, although PAMAM-G6-cystamine-(Gd-DO3A) showed some advantages compared with the nondegradable control, PAMAM dendrimers are not suitable carriers for biodegradable macromolecular MRI contrast agents, due to their high toxicity.

Effects of sevelamer and calcium-based phosphate binders on mortality in hemodialysis patients

Elevated serum phosphorus and calcium are associated with arterial calcification and mortality in dialysis patients. Unlike calcium-based binders, sevelamer attenuates arterial calcification but it is unknown whether sevelamer affects mortality or morbidity. In a multicenter, randomized, open-label, parallel design trial we compared sevelamer and calcium-based binders on all-cause and cause-specific mortality (cardiovascular, infection, and other) in prevalent hemodialysis patients. A total of 2103 patients were initially randomized to treatment and 1068 patients completed the study. All-cause mortality rates and cause-specific mortality rates were not significantly different. There was a significant age interaction on the treatment effect. Only in patients over 65 years of age was there a significant effect of sevelamer in lowering the mortality rate. There was a suggestion that sevelamer was associated with lower overall, but not cardiovascular-linked, mortality in older patients. We suggest that further research is needed to confirm these findings.

Sevelamer and Other Anion-Exchange Resins in the Prevention and Treatment of Hyperphosphataemia in Chronic Renal Failure

Sevelamer, or more precisely 'sevelamer hydrochloride', is a weakly basic anion-exchange resin in the chloride form that was introduced in 1997 for the treatment of the hyperphosphataemia of patients with end-stage renal failure, usually those on long-term haemodialysis. The rationale for this therapy was that sevelamer would sequester phosphate within the gastrointestinal tract, so preventing its absorption and enhancing its faecal excretion. Over the succeeding years, large numbers of patients have been treated with sevelamer, and it has fulfilled expectations in helping to control the hyperphosphataemia of end-stage renal failure. However, it is only one of many anion-exchange resins that could be used for this purpose, some of which are currently available for clinical use and are much less costly than sevelamer. Theoretical considerations suggest that some of these other resins might be at least as efficient as sevelamer in sequestering phosphate in the gastrointestinal tract. Neither sevelamer, nor any of these other agents, has been submitted to a proper metabolic balance study to measure the amount of phosphate sequestered by the resin in the bowel, and without this information it is impossible to judge which is the ideal resin for this purpose.

Highly Poly(Ethylene) Glycolylated Islets Improve Long-Term Islet Allograft Survival without Immunosuppressive Medication

The surface modification of islets using poly(ethylene glycol) (PEG) is being studied as a means of preventing host immune responses against transplanted islets. In this study, to completely shield islets with PEG molecules, we increased the amount of PEG conjugated to islet surfaces, by multiple PEGylation or amplified PEGylation using poly-L-lysine, poly(allylamine), or poly(ethyleneimine), respectively. Amplified PEGylation was associated with islet cytotoxicity and functional impairment, but multiple PEGylation affected neither islet viability nor functionality. In addition, when triply PEGylated islets were allotransplanted into diabetic recipients, these islets survived in 3 of the 7 recipients for more than 100 days without any immunosuppressive treatment. Moreover, the blood glucose levels of these 3 recipients were stable and in the normal range. Immunohistochemical analysis showed that 3 of 7 triply PEGylated islets transplants survived for 100 days and that 4 that were rejected before day 20 were all immunologically protected from immune cells. However, unmodified islets were completely destroyed within 1 week. Consequently, we suggest that multiple PEGylation offers an effective means of reducing the immunogenicity of transplanted islets by increasing the amount of surface-bound PEG.

Development of a polyamine database for assessing dietary intake

Reducing the concentration of polyamines (spermine, spermidine, and putrescine) in the body pool may slow the cancer process. Because dietary spermine, spermidine, and putrescine contribute to the body pool of polyamines, quantifying them in the diet is important. Limited information about polyamine content of food is available, especially for diets in the United States. This brief report describes the development of a polyamine database linked to the Fred Hutchinson Cancer Center food frequency questionnaire (FFQ). Values for spermine, spermidine, and putrescine were calculated and reported per serving size (nmol/serving). Of the foods from the database that were evaluated, fresh and frozen corn contain the highest levels of putrescine (560,000 nmol/serving and 902,880 nmol/serving) and spermidine (137,682 nmol/serving and 221,111 nmol/serving), and green pea soup contains the highest concentration of spermine (36,988 nmol/serving). The polyamine database and FFQ were tested with a convenience sample (n=165). Average daily polyamine intakes from the sample were: 159,133 nmol/day putrescine, 54,697 nmol/day spermidine, and 35,698 nmol/day spermine. Orange and grapefruit juices contributed the greatest amount of putrescine (44,441 nmol/day) to the diet. Green peas contributed the greatest amount of spermidine (3,283 nmol/day) and ground meat contributed the greatest amount of spermine (2,186 nmol/day). Development of this database linked to an FFQ provides a means of estimating polyamine intake and contributes to investigations relating polyamines to cancer.

Results of a randomized crossover study comparing once-daily and thrice-daily sevelamer dosing

BACKGROUND

Patients with renal failure require complex regimens of renal replacement therapies and medications, including ingestion of phosphate-binding agents 3 times daily. Previous studies suggested that sevelamer may provide extended phosphate binding and be effective with once-daily dosing, thus simplifying the phosphate-binder regimen.

METHODS

Twenty-four patients were enrolled in this study, 21 of whom were randomly assigned to sevelamer administration at their previously prescribed dose, either once daily with the largest meal or thrice daily with meals, with crossover to the other regimen after 4 weeks. Eighteen patients completed both treatment periods. The primary efficacy measure for which the study was powered is comparison of the effect of once-daily versus standard thrice-daily sevelamer dosing on serum phosphorus level control, determined by using equivalence testing. Secondary efficacy measures are the effects of the 2 regimens on serum calcium level corrected for albumin level; calcium x phosphorus product; albumin; intact parathyroid hormone; total, low-density lipoprotein, high-density lipoprotein, and non-high-density lipoprotein cholesterol; and triglyceride levels.

RESULTS

Once-daily sevelamer was as effective as thrice-daily dosing of sevelamer in controlling serum phosphorus, calcium, calcium x phosphorus product, serum albumin, and serum lipid levels. Bioequivalence was not shown for intact parathyroid hormone, likely because of high variability. Mean serum phosphorus levels were 4.6 +/- 0.3 mg/dL (1.49 +/- 0.10 mmol/L) during thrice-daily dosing and 5.0 +/- 0.3 mg/dL (1.61 +/- 0.10 mmol/L) during once-daily dosing. The average prescribed dose of sevelamer during both treatment regimens was 6.7 +/- 2.4 g. Routine laboratory measures were similar in the 2 groups. Both regimens were well-tolerated.

CONCLUSION

Despite concerted patient-directed educational efforts, phosphorus level control in patients with renal failure is suboptimal and contributes to increased mortality risk. Once-daily sevelamer could simplify these regimens and encourage medication compliance, perhaps improving hyperphosphatemia management.

Long-term management of sevelamer hydrochloride-induced metabolic acidosis aggravation and hyperkalemia in hemodialysis patients

Sevelamer hydrochloride use in hemodialysis patients is complicated by metabolic acidosis aggravation and hyperkalemia. Rare reports about a short-term correction of this complication have been published. The current authors investigated the long-term correction of metabolic acidosis and hyperkalemia in sevelamer hydrochloride-treated patients at doses adequate to achieve serum phosphate levels within K/DOQI recommendations. The authors followed 20 hemodialysis patients for 24 months in an open-label prospective study. The dialysate bicarbonate concentration was increased stepwise to a maximum 40 mEq/L and adjusted to reach patient serum bicarbonate levels of 22 mEq/L, according to K/DOQI recommendations. Laboratory results for serum bicarbonate, potassium, calcium, phosphate, albumin, alkaline phosphatase, iPTH, cholesterol (HDL-LDL), triglycerides, Kt/V, systolic-diastolic arterial pressure were recorded. Sevelamer hydrochloride-induced metabolic acidosis aggravation and hyperkalemia in hemodialysis patients were corrected, on the long-term, by an increase in dialysate bicarbonate concentration. Further improvement in bone biochemistry was noted with this adequate acidosis correction and parallel sevelamer hydrochloride administration, in sufficiently large doses to achieve K/DOQI phosphate recommendations.

Sevelamer hydrochloride versus aluminum hydroxide: effect on serum phosphorus and lipids in CAPD patients

BACKGROUND

Dietary phosphorus restriction, oral administration of phosphorus binders, and dialysis are the main strategies to control hyperphosphatemia in patients with stage 5 chronic kidney disease. Aluminum hydroxide (AH) and calcium carbonate, the most commonly used phosphorus binders, have serious disadvantages, such as aluminum toxicity and hypercalcemia. Sevelamer hydrochloride (SH) is a relatively new nonabsorbed calcium- and aluminum-free phosphorus binder. The present study was designed to evaluate the efficacy of SH in the control of hyperphosphatemia and its effect, compared to AH, on serum lipid parameters in patients on continuous ambulatory peritoneal dialysis (CAPD).

METHODS

30 stable patients on CAPD were included in an open-label, randomized crossover study. After a 2-week phosphorus binder washout period, 15 patients (group I) were administered SH for 8 weeks and in the remaining patients (group II), AH was introduced (phase A). After a new 2-week washout period, patients crossed over to the alternate agent for another 8 weeks (phase B).

RESULTS

There were similar reductions in serum phosphorus levels over the course of the study with both agents: by 1.18 +/- 0.07 mg/dL (0.38 +/- 0.03 mmol/L) with SH and by 1.25 +/- 0.15 mg/dL (0.40 +/- 0.05 mmol/L) with AH in phase A (p = NS), and by 1.35 +/- 0.25 mg/dL (0.43 +/- 0.08 mmol/L) with AH and by 1.23 +/- 0.80 mg/dL (0.39 +/- 0.25 mmol/L) with SH in phase B (p = NS). Moreover, SH administration was associated with a 10.5% +/- 9.4% and a 20.1% +/- 6.8% fall in total cholesterol (p < 0.05) and low-density Lipoprotein cholesterol (p < 0.001) in phase A, and 11.9% +/- 7.2% (p < 0.05) and 21.5% +/- 2.4% (p < 0.001), respectively, in phase B. In both phases of the study, AH administration was not followed by a significant change in serum lipid parameters.

CONCLUSION

Sevelamer hydrochloride is a well-tolerated alternative to calcium- or aluminum-containing phosphorus binder in the control of serum phosphorus in CAPD patients. Furthermore, SH improves the lipid profile in these patients.

Sevelamer worsens metabolic acidosis in hemodialysis patients

BACKGROUND

Sevelamer hydrochloride, a major phosphate binder for patients on maintenance hemodialysis (MHD) is associated with reduced serum bicarbonate concentration due to hydrochloric acid release in the gut and to the binding of short chain fatty acids in the large intestine. Since metabolic acidosis can be deleterious, a study was devised to compare the time course of serum bicarbonate concentration during treatment with sevelamer hydrochloride or calcium carbonate.

METHODS

Sixteen well nourished patients on MHD who were in excellent clinical conditions and achieving target levels for blood pressure (BP) and hemoglobin (Hb), while on a protein intake of 1.1g/kg body weight (bw), were enrolled in the study. After a 2-week washout period, the patients were divided into two groups, each consisting of eight patients, and randomized either to 24 weeks of sevelamer followed by 24 weeks of calcium carbonate (group A) or to 24 weeks of calcium carbonate followed by 24 weeks of sevelamer (group B). Protein intake, n-protein catabolic rate (nPCR), serum concentrations of calcium, phosphate, calcium x phosphate (Ca x P) product, bicarbonate, intact parathyroid hormone (iPTH) and albumin were monitored. Time course changes in serum bicarbonate concentrations in relation to short and long dialytic intervals (48 vs. 72 hr) were also investigated.

RESULTS

Both sevelamer and calcium carbonate effectively controlled serum phosphate and the Ca x P product. During calcium carbonate treatment plasma phosphate concentrations were significantly below those of patients on sevelamer. Plasma bicarbonate concentration fell within target DOQI values during calcium carbonate administration both in group A and in group B, a goal which was not achieved under sevelamer administration. After a long dialytic interval in patients on sevelamer, serum bicarbonate concentration averaged 17.3 +/- 1.1 mEq/L, whereas it averaged 21.1 +/- 0.7 mEq/L in patients on calcium carbonate (p<0.01). Finally, a 24-week sevelamer administration caused a statistically significant (p<0.05) reduction (0.8 g/dL) in serum albumin concentration, without affecting iPTH. Taken together, these results indicate that sevelamer worsens metabolic acidosis, which needs to be corrected.

[Relationship between serum calcium level and PTH concentration proved with sevelamer hydrochloride]

About a dialysis patient's calcium-phosphate (Ca.P) metabolism, in general good control is obtained by use of sevelamer hydrochloride. As for this, what is significantly depended on not only lower P concentration but also lower Ca concentration by the change to sevelamer hydrochloride from calcium carbonate. However, by one side, much rises of i-PTH are observed by most patients with change to sevelamer hydrochloride. In this examination, Deltai-PTH was intentionally correlated with Delta calcium concentration but there was no correlation in i-PTH and Ca concentration.

[Treatment with phosphate binder (sevelamer hydrochloride, calcium carbonate) based on PTH]

When sevelamer hydrochloride is used as a phosphate binder instead of the more common calcium carbonate, the PTH rises. This has been observed in many cases and makes it more difficult for practical use. However, considering the calcium load, the excessive dosing of calcium carbonate must be avoided. With that in mind, we divided the i-PTH in groups of 100 pg/mL and tested the changes in i-PTH value, P value, the adjusted Ca value, and the product of Ca and P before and after a dosage of sevelamer hydrochloride. When the average i-PTH was under 100mg/mL 6 months before dosing, the sevelamer hydrochloride single dosage group showed an early rise in i-PTH after dosing, maintaining a higher level than the calcium carbonate combined dosage group. Therefore, it was concluded that the use of sevelamer hydrochloride alone as a phosphate binder is best. On the other hand, the group with an average i-PTH over 100 pg/mL 6 months before dosing showed a rise of i-PTH that went over the K/DOQI guideline with a single dosing of sevelamer hydrochloride. Therefore, we concluded that using both sevelamer hydrochloride and calcium carbonate for phosphate binder is best.

[Defining the role of sevelamer chloride as a therapeutic agent for management of phosphate in patient with hemodialysis]

It has been about 18 months after the commercial release of sevelamer hydrochloride. I examined the phosphorus management in patient with hemodialysis with the use sevelamer hydrochloride. The phosphorus reduction of sevelamer hydrochloride was weaker than the precipitated calcium carbonate. Patients on artificial dialysis must undergo dietary therapy for the sevelamer hydrochloride to be effective. However, by switching from precipitated calcium carbonate to sevelamer hydrochloride, the calcium level dropped, and as a result the intact PTH rose. It was possible to subdue the rise of intact PTH with vitamin D. The usefulness of vitamin D dramatically increased with the decrease and the eventual cancellation of precipitated calcium carbonate. Furthermore, the calcium load lightened and the product of calcium and phosphorus decreased. At this point, I do not expect substantial phosphorus reduction from sevelamer hydrochloride. It must be recognized that the basis of phosphorus management is proper diet. Only with that can sevelamer hydrochloride be used to its fullest potential.

[Treatment of adynamic bone disease with the complete replacement from calcium carbonate to sevelamer hydrochloride]

The aim of this study was to examine the therapeutic effect of hypocalcemic stimulation caused by sevelamer hydrochloride (SH) administration on adynamic bone disease (ABD). The subjects were 28 maintenance hemodialysis (HD) patients who had remained in ABD state in spite of no administration of vitamin D(3) since HD induction (15 males and 13 females;12 diabetic patients and 16 non-diabetic patients). The mean age was 61.8+/-9.5 years and the mean HD duration was 5.5+/-3.9 years. The calcium concentration in the dialysate was 3.0 mEq/L. We made the final daily dose of SH after two months the same as the first daily dose of calcium carbonate (CC) in the following manner. At first we administered only CC at breakfast and lunch and SH at supper. And for the next two weeks we administered CC at breakfast and SH at lunch and supper. And for the final two weeks we administered only SH. After that we increased the dose of SH as much as possible. We evaluated the therapeutic effect of the above treatment on ABD using intact-osteocalcin (iOC) [Teijin. Tokyo] as a marker before and 6, 12 months after the beginning of the replacement. If iOC Ievel of 30 to 70 ng/mL showed normal tumover bone (NTB), 5 cases (17.9%) changed into NTB in 6 months. 9 cases (32.1%) changed into NTB in 12 months and one case (3.6%) changed into ostitis fibrosa in 12 months. It is thought that SH is effective for the treatment of ABD but we have to be careful for ostitis fibrosa.

In vitro and in vivo gene transfer with poly(amino acid) vesicles

Non-viral gene delivery systems utilise either amine lipids or polyamines and although non-viral gene delivery systems are said to have a superior safety profile to viruses, the polyamines such as poly(L-lysine) are toxic when used without derivatisation and usually require specific receptor mediated uptake and/or endosomolytic agents to be effective. However, the conversion of poly(L-lysine) and poly(L-ornithine) polyamino acids into amphiphilic vesicle forming polymers reduces the toxicity of the polyamino acids and enables the resulting polyamino acid vesicles to deliver genes both in vitro and in vivo in the absence of receptor specific ligands and endosomolytic agents. The incorporation of a distearoylphosphatidylethanolamine poly(ethylene glycol)-galactosamine conjugate (with the galactosamine unit at the distal end of the poly(ethylene glycol) moiety) into the polyamino acid formulations improved in vitro gene transfer in the case of the amphiphilic poly(L-ornithine) (POP) although no in vivo targeting was detected with the galactosamine formulations. We conclude that the conversion of poly(L-lysine) and poly(L-ornithine) into amphiphilic colloid forming molecules reduces their toxicity, thus allowing these systems to be used for gene transfer in vivo. It is possible that this approach may be extended to other polyamines.

Poly(HEMA)--based embolic material in endovascular surgery of liver

Physico-chemical and medico-biological methods, including hematology and cytology, were used in an evaluation of properties of poly(2-hydroxyethyl methacrylate) (poly(HEMA))-based embolic material indicated in the occlusion of branches of hepatic artery of patients with focal alterations of the liver. The elastographic method helped in predicting mechanical properties of the hydrogel material. Poly(HEMA) was mechanically stable for endovascular applications, exhibited no significant loss in elasticity and possessed consistency resembling the soft tissue of the organism. Analysis of blood in contact with poly(HEMA) hydrogel provided a control of its biological inertness. Recently, 315 patients with focal alterations of the liver, including hemobilic hemorrhages and both primary and metastatic tumors, underwent endovascular occlusion with poly(HEMA) emboli as a pre-surgical step or as a simple occlusive measure. Compared with a direct operation on hemangiomatous injuries in the liver without endovascular occlusion, embolization with poly(HEMA) allowed to reduce 2.5-3 times bleeding in the operational zone. At the same time, the poly(HEMA) embolic material induced activation of general hemostatic reaction in the postembolization period.

Prevention of experimental cerebral vasospasm by intracranial delivery of a nitric oxide donor from a controlled-release polymer: toxicity and efficacy studies in rabbits and rats

BACKGROUND AND PURPOSE

A reduction in the local availability of nitric oxide (NO) may play a role in the etiology of chronic cerebral vasospasm after subarachnoid hemorrhage (SAH). We investigated the toxicity and efficacy of a locally delivered NO donor from a controlled-release polymer in preventing experimental cerebral vasospasm in rats and rabbits, respectively.

METHODS

Diethylenetriamine/NO (DETA/NO) was incorporated into controlled release ethylene-vinyl acetate (EVAc) polymers. Twenty-eight rats were used in a dose-escalation toxicity study to establish a maximally tolerated dose of DETA/NO-EVAc polymer. In the efficacy experiment, 20 rabbits were assigned to 4 experimental groups (n=5 per group): sham operation; SAH only; SAH+empty EVAc polymer; and SAH+DETA/NO-EVAc polymer. Treatment was initiated 30 minutes after blood deposition. Basilar artery lumen patency was assessed 72 hours after hemorrhage to evaluate the efficacy of DETA/NO in preventing cerebral vasospasm.

RESULTS

In the toxicity study, a dose of 3.4 mg/kg was identified as the LD(20) (dose with 20% mortality during the study period) of this DETA/NO formulation. Brain histology revealed hemorrhage and ischemic changes at the implantation site associated with high concentrations of DETA/NO. In the efficacy study, treatment with DETA/NO-EVAc polymer resulted in a significant decrease in basilar artery vasospasm compared with no treatment (93.0+/-4.9% versus 71.4+/-11.9%; P=0.035) or compared with treatment with blank EVAc polymer (93.0+/-4.9% versus 73.2+/-6.4%; P=0.003).

CONCLUSIONS

Local delivery of DETA/NO prevents vasospasm in the rabbit basilar artery. Local delivery of DETA/NO via polymers is a safe and effective strategy for preventing cerebral vasospasm after SAH in this model.

Cross-reactivity of Sydney funnel-web spider antivenom: neutralization of the in vitro toxicity of other Australian funnel-web (Atrax and Hadronyche) spider venoms

Australian funnel-web spiders are recognized as one of the most venomous spiders to humans world-wide. Funnel-web spider antivenom (FWS AV) reverses clinical effects of envenomation from the bite of Atrax robustus and a small number of related Hadronyche species. This study assessed the in vitro efficacy of FWS AV in neutralization of the effects of funnel-web spider venoms, collected from various locations along the eastern seaboard of Australia, in an isolated chick biventer cervicis nerve-muscle preparation. Venoms were separated by SDS-PAGE electrophoresis to compare protein composition and transblotted for Western blotting and incubation with FWS AV.SDS-PAGE of venoms revealed similar low and high molecular weight protein bands. Western blotting with FWS AV showed similar antivenom binding with protein bands in all the venoms tested. Male funnel-web spider venoms (7/7) and female venoms (5/10) produced muscle contracture and fasciculation when applied to the nerve-muscle preparation. Venom effects were reversed by subsequent application of FWS AV or prevented by pretreatment of the preparation with antivenom.FWS AV appears to reverse the in vitro toxicity of a number of funnel-web spider venoms from the eastern seaboard of Australia. FWS AV should be effective in the treatment of envenomation from most, if not all, species of Australian funnel-web spiders.

Biocompatibility of polycations: in vitro agglutination and lysis of red blood cells and in vivo toxicity

The effects of six polycations were studied in vitro on red blood cells (RBC) and in vivo after intravenous administration. Hemagglutination and hemolysis depended not only on the molar mass and the concentration of these polycations, but also on their chemical nature. The hemagglutination and hemolysis induced by poly(L-lysine), diethylaminoethyldextran, poly(dimethyldiallylammonium) chloride and poly[2-(dimethylamino)ethyl methacrylate] was low to moderate, whereas a severe hemolysis was induced by a partially quaternized poly[thio-1-(N,N-diethyl-aminoethyl)ethylene]. In the case of poly(epsilon-lysine), no significant hemagglutination nor hemolysis was observed. The presence of plasma proteins reduced both agglutination and hemolysis. This protective effect was enhanced when the polycations interacted with plasma proteins before contact with RBC. In the presence of albumin, the behavior depended on the polycation and on the order of addition of the three components of the suspension, namely albumin, polycation and RBC. Depending on the polycation, albumin-polycation complexes were either less active or more active on RBC than the same polycation in protein-free medium. In vivo the studied polycations induced an immediate mortality except poly(epsilon-lysine), which induced a delayed mortality. The minimal dose of polycations inducing immediate mortality paralleled their effect on RBC.

Production of pathogen-inactivated RBC concentrates using PEN110 chemistry: a Phase I clinical study

BACKGROUND

Despite extensive reductions in risk, donor selection and testing cannot eliminate pathogen transmission. The objective of this study was to evaluate clinically the viability of pathogen-inactivated RBCs.

STUDY DESIGN AND METHODS

Twelve healthy subjects each donated two units of blood that were handled as additive system control units or were inactivated using the PEN110 process (INACTINE, V.I. Technologies) in randomized order. PEN110, which inactivates pathogens by reacting with nucleic acid bases, was incubated with RBCs for 6 hours, followed by washing and quenching with sodium thiosulfate. Radiolabeled RBC recovery and survival determinations were undertaken after 28 days of storage; biochemical and hematologic variables were assessed over 42 days.

RESULTS

After 28 days, treated units had a 24-hour double-label ((51)Cr/(99m)Tc) recovery (85.0 +/- 5.0%) that was indistinguishable from control units (85.9 +/- 2.7%); the times required for reduction of radioactivity of labeled cells to half the Day 1 activity (T(50)) were similar for both groups (treated, 31.9 +/- 8.2 days; control, 32.9 +/- 3.3 days). No deleterious effects of PEN110 treatment were found on RBC antigens tested. Treatment reduced 2,3-DPG levels by half and slightly lowered pH levels. Throughout the 42-day storage period, treated RBCs had a lower level of lactate production and a trend toward lower glucose consumption. Hemolysis remained below 1 percent; supernatant potassium and ATP levels were lower than those seen in control RBCs.

CONCLUSION

PEN110-treated RBCs stored for 28 days meet all critical requirements for therapeutically useful units.

Novel synthetic polyamines are effective in the treatment of experimental microsporidiosis, an opportunistic AIDS-associated infection

Microsporidia are eukaryotic obligate intracellular protists that are emerging pathogens in immunocompromised hosts, such as patients with AIDS or patients who have undergone organ transplantation. We have demonstrated in vitro and in vivo that synthetic polyamine analogs are effective antimicrosporidial agents with a broad therapeutic window. CD8-knockout mice or nude mice infected with the microsporidian Encephalitozoon cuniculi were cured when they were treated with four different novel polyamine analogs at doses ranging from 1.25 to 5 mg/kg of body weight/day for a total of 10 days. Cured animals demonstrated no evidence of parasitemia by either PCR or histologic staining of tissues 30 days after untreated control animals died.

Occupational dermatoses from one-component epoxy coatings containing a modified polyamine hardener

In an electronics plant, 2 one-component epoxy coatings containing a modified polyamine hardener were used as covering materials for protecting important information on police radio circuit boards. The resinous parts of the coatings consisted of epoxy resins based on diglycidyl ether of bisphenol F. The hardener was a dimethylaminopropylamine (DMAPA)-epoxy adduct and contained about 0.16% free DMAPA. Of 105 workers, 17 (16%) were diagnosed to have work-related dermatitis but were not patch tested. The hands were the commonly affected region (13 out of 17 cases). The latent period of dermatitis was very short (mean 21.5 days). The work-related dermatoses were closely related to the type of work and working periods. In the present study, hand protection and the introduction of automation have been demonstrated to be useful for the prevention of epoxy coating dermatitis.

RenaGel, a nonabsorbed calcium- and aluminum-free phosphate binder, lowers serum phosphorus and parathyroid hormone. The RenaGel Study Group

BACKGROUND

This multicenter, open-label, dose-titration study assessed the safety and efficacy of RenaGel(R), a nonabsorbed calcium- and aluminum-free phosphate binder, in lowering serum phosphorus. Secondary outcomes were its effects on serum intact parathyroid hormone (iPTH) and serum lipids.

METHODS

Phosphate binders were discontinued during a two-week washout period. Patients whose serum phosphorus was more than 6.0 mg/dl during washout were eligible for treatment. RenaGel(R), at starting doses of two, three, or four 440 mg capsules three times per day with meals, was administered to 172 hemodialysis patients for eight weeks. RenaGel(R) could be increased by one capsule per meal every two weeks as necessary to achieve serum phosphorus control. A second two-week washout period followed.

RESULTS

Mean serum phosphorus rose from 6.8 +/- 2.0 mg/dl at prewashout to 9.1 +/- 2.4 mg/dl at the end of the washout period. It then declined to 6.6 +/- 1.9 mg/dl by the end of the eight-week RenaGel(R) treatment period (P < 0. 0001). Serum phosphorus increased to 8.0 +/- 2.2 mg/dl at the end of the second washout period. The mean dose at the end of RenaGel(R) treatment was 5.4 g per day. Eighty-four percent of the patients previously used calcium-based phosphate binders. As expected, calcium declined during the initial washout period when calcium-based phosphate binders were discontinued. Mean serum calcium declined from 9.6 +/- 1.0 mg/dl at prewashout to 9.1 +/- 0.8 mg/dl after washout. It then increased to 9.4 +/- 0.9 mg/dl by the end of RenaGel(R) treatment. Median serum iPTH increased during the two-week washout from 208 pg/ml to 316 pg/ml and then declined to 224 pg/ml at the end of the eight-week treatment period (P < 0.0001 vs. end of initial washout). After eight weeks of treatment, RenaGel(R) reduced mean serum total cholesterol from 171.0 +/- 43.1 mg/dl to 145.0 +/- 38.7 mg/dl (P < 0.0001) and mean serum low-density lipoprotein cholesterol from 102.0 +/- 34.9 mg/dl to 75. 6 +/- 29.4 mg/dl (P < 0.0001). High-density lipoprotein cholesterol, triglycerides, and serum albumin did not change.

CONCLUSIONS

RenaGel(R), a novel and calcium- plus aluminum-free effective phosphate binder, can control serum phosphorus and reduce the levels of PTH and cholesterol without inducing hypercalcemia or other side effects. Thus, this new phosphate binder may be effective in the treatment of renal osteodystrophy in uremic patients.

Effect of RenaGel, a non-absorbed, calcium- and aluminium-free phosphate binder, on serum phosphorus, calcium, and intact parathyroid hormone in end-stage renal disease patients

BACKGROUND

Control of dietary phosphate absorption in end-stage renal disease patients is essential to prevent the deleterious sequelae of phosphorus retention. Efficacy of currently available calcium- and aluminium-containing phosphate binders is constrained by the side-effects associated with the absorption of calcium and aluminium. The current study examined the efficacy of RenaGel, a calcium- and aluminium-free, polymeric phosphate binder, in end-stage renal disease patients.

METHODS

Administration of calcium- or aluminium-containing phosphate binders ceased during a 2-week washout period. RenaGel, at starting doses of one, two, or three 500-mg capsules three times per day with meals, was administered for 8 weeks. RenaGel dose was titrated up 1 capsule per meal at the end of each 2-week period if necessary to achieve phosphorus control. A second 2-week washout period followed the end of RenaGel treatment.

RESULTS

Mean serum phosphorus rose from a pre-washout level of 6.9 mg/dl (2.23 mmol/l) to 8.1 mg/dl (2.62 mmol/l) at the end of the initial 2-week washout. With RenaGel treatment, serum phosphorus declined and returned to pre-washout levels after 4 weeks. Serum phosphorus reached a nadir of 6.5 mg/dl (2.10 mmol/l) after 7 weeks of RenaGel treatment. Serum phosphorus rose to 8.2 mg/dl (2.65 mmol/l) 2 weeks after cessation of RenaGel treatment. As anticipated, calcium declined during the initial washout period when calcium-based phosphate binders were stopped for the majority of patients. The rise in serum phosphorus and decline in serum calcium during washout resulted in an increase in median intact parathyroid hormone (iPTH) levels from 292 pg/ml to 395 pg/ml. iPTH fell to 283 pg/ml after 6 weeks of RenaGel treatment despite a persistently lower serum calcium. RenaGel treatment also reduced serum total and LDL cholesterol by 25 mg/dl (0.65 mmol/l) and 23 mg/dl (0.59 mmol/l) respectively.

CONCLUSIONS

RenaGel appears to be an effective phosphate binder free of calcium and aluminium. Phosphorus control with two to four RenaGel capsules per meal appears to result in comparable phosphorus lowering seen with calcium- or aluminium-based phosphate binders. RenaGel may offer an alternative for the control of phosphorus retention in end-stage renal disease patients.