Non-Labeled, Stable Labeled, or Radiolabelled Approaches for Provision of Intravenous Pharmacokinetics in Humans: A Discussion Piece

A review of the use of microdoses and isotopic microtracers for clinical intravenous pharmacokinetic (i.v. PK) data provision is presented. The extent of application of the varied approaches available and the relative merits of each are highlighted with the aim of assisting practitioners in making informed decisions on the most scientifically appropriate design to adopt for any given new drug in development. It is envisaged that significant efficiencies will be realized as i.v. PK data in humans becomes more routinely available for suitable assets in early development, than has been the case prior to the last decade.

Recommendations on the Use of Multiple Labels in Human Mass Balance Studies

The administration of radiolabeled drug candidates is considered the gold standard in absorption, distribution, metabolism, and excretion studies for small-molecule drugs since it allows facile and accurate quantification of parent drug, metabolites, and total drug-related material independent of the compound structure. The choice of the position of the radiolabel, typically 14C or 3H, is critical to obtain relevant information. Sometimes, a biotransformation reaction may lead to cleavage of a part of the molecule. As a result, only the radiolabeled portion can be followed, and information on the fate of the nonlabeled metabolite may be lost. Synthesis and administration of two or more radiolabeled versions of the parent drug as a mixture or in separate studies may resolve this issue but comes with additional challenges. In this paper, we address the questions that may be considered to help make the right choice whether to use a single or multiple radiolabel approach and discuss the pros and cons of different multiple-labeling strategies that can be taken as well as alternative methods that allow the nonlabeled part of the molecule to be followed. SIGNIFICANCE STATEMENT: Radiolabeled studies are the gold standard in drug metabolism research, but molecules can undergo cleavage with loss of the label. This often results in discussions around potential use of multiple labels, which seem to be occurring with increased frequency since an increasing proportion of the small-molecule drugs are tending towards larger molecular weights. This review provides insight and decision criteria in considering a multiple-label approach as well as pros and cons of different strategies that can be followed.

The prevalence of atrial fibrillation in Greenland: a register-based cross-sectional study based on disease classifications and prescriptions of oral anticoagulants

   Previous studies of the prevalence of atrial fibrillation (AF) in Greenland are based on either single-point electrocardiograms (ECGs) or patients admitted with stroke. This study estimates the prevalence of AF based on disease classifications in the electronic medical record system (EMR) and prescriptions of oral anticoagulants (OACs). Patients given a diagnose classification code for AF or atrial flutter or prescribed the vitamin K antagonist Warfarin or the direct-acting oral anticoagulant Rivaroxaban were identified in the EMR. Descriptive data and selected laboratory values were extracted, and a minimum CHA₂DS₂-VASc score was calculated for the 790 patients identified in the EMR (66% men). A total prevalence of AF of 1.4% was found in the general population (1.8% among men and 1.0% among women), with a significantly lower prevalence among women younger than 70 years. There was a significant increase in AF-prevalence with advancing age (p<0.001) for both men and women. A minimum CHA₂DS₂-VASc was estimated and app. 10% of the patients may be undertreated with OACs. The prevalence of AF found in this study is higher than that found in previous studies in Greenland and comparable to the prevalence found in other Western countries, indicating that AF is common in Greenland.

Prevalence, incidence, mortality, and quality of care of diagnosed diabetes in Greenland

AIMS

To estimate prevalence, incidence, and mortality of diagnosed diabetes in Greenland, and to evaluate quality of diabetes care among men and women, and patients living in towns and settlements.

METHODS

This study was designed as an observational cross-sectional study based on review of data obtained from the electronic medical record (EMR) in Greenland. All permanent residents of Greenland registered with a diabetes diagnosis in the EMR (N = 1498) were included.

RESULTS

The age-standardized prevalence of diabetes was 2.19% as of Nov 30, 2018. The age-standardized incidence was 147 per 100,000 per year and the age-standardized mortality was 62 per 10,000 person-year among people aged ≥0 years old (Dec 1, 2017 to Nov 30, 2018). Quality of diabetes care was slightly higher among women compared to men concerning proportion with annual measurement of glycated haemoglobin (HbA_1c) (89.9% vs. 85.8%; p < 0.015), blood pressure (83.7% vs. 76.7%; p < 0.001).The only difference observed in quality of care among settlements and towns was lower proportion tested for microalbuminuria within one year in settlements (50.3% vs. 40.1%; p < 0.001).

CONCLUSIONS

The age-standardized prevalence of diagnosed diabetes in Greenland was 2.19% and the prevalence of diagnosed diabetes among adults aged ≥20 years was 3.7%. Only minor differences in quality of care related to gender and place of residence were observed. Further improvements in quality of care are warranted.

Improvement of diabetes care in a small but geographically widely spread population in Greenland. Effects of a national diabetes care programme

AIMS

To estimate the prevalence of diagnosed Type 2 diabetes mellitus in Greenland and to evaluate the quality of the diabetes care before and after implementation of a new diabetes programme.

METHODS

In this observational and cross-sectional study, data from the medical records were collected in Greenland in 2008 and 2010. Information about age, gender, most recently measured HbA(1c) , blood pressure and serum cholesterol and from the examination of eyes, feet and urine was obtained. The prevalence was estimated using the whole adult population in Greenland as background population. The quality of the diabetes care was monitored by six process, three biological and three treatment indicators. A diabetes concept based on national guidelines, systematized recording in an electronic medical record and feedback to the clinics were used to improve diabetes care.

RESULTS

Four hundred and sixty-five patients were included in the 2008 sample and 691 in the 2010 sample. The total prevalence increased from 2.3 (95% CI 2.1-2.5) % in 2008 to 2.7 (95%CI 2.5-3.0) among Greenlanders aged 40 years old or above, corresponding to an increase of 19% (P = 0.006). All process indicators improved significantly between the two observations.

CONCLUSIONS

Along with an increasing prevalence of diagnosed Type 2 diabetes, all six process quality indicators increased. It is strongly recommended that focus on the quality of diabetes care in Greenland should be maintained in order to benefit from the programme in the longer term.

Orthostatic hypotensive effect of antipsychotic drugs in Wistar rats by in vivo and in vitro studies of alpha1-adrenoceptor function

RATIONALE

Many antipsychotics cause orthostatic hypotension possibly due to antagonist action on resistance vessel alpha1A-adrenoceptors (alpha1A-AR).

OBJECTIVE

We have tested this possibility by determining in Wistar rats how the orthostatic hypotensive effect of several antipsychotic drugs compares with their affinity for adrenoceptors in mesenteric small arteries (MSA with mainly alpha1A-AR) and aorta (mainly alpha1D-AR).

MATERIALS AND METHODS

Using a tilt setup, orthostatic hypotension was measured in anaesthetized rats for prazosin and the antipsychotics haloperidol, sertindole, risperidone, clozapine, ziprasidone, domperidone, olanzapine, and aripiprazole. For in vitro studies, segments of MSA and aorta were mounted on a wire myograph for isometric tension recording. Cumulative concentration-response curves were constructed to phenylephrine (PE) in the absence and presence of the drugs. Apparent affinity (pA2) was calculated by Schild analysis.

RESULTS

Prazosin antagonized tilt-induced and PE responses in both studies (threshold 4 ng/ml, pA2 9.52 MSA, 10.1 aorta). The rank order of the potency of the antipsychotics in the tilt experiments correlated (r2 = 0.69, P = 0.01) with the pA2-values in MSA: Risperidone and sertindole had the highest potency in the tilt test (threshold 159 and 97 ng/ml) and the highest apparent affinity in MSA (pA2 8.92 and 8.78), in contrast with aripiprazole and domperidone, which had the lowest in each case (threshold 4.1 and 3.0 microg/ml, pA2 7.17 and 6.99). In aorta, the pA2 values did not correlate with the in vivo potencies; in particular, sertindole had no functional affinity in aorta.

CONCLUSION

We conclude that the orthostatic hypotensive effect in rats of the antipsychotic drugs investigated is mediated through alpha1A-ARs.

Efficacy of small-molecule glycogen synthase kinase-3 inhibitors in the postnatal rat model of tau hyperphosphorylation

BACKGROUND AND PURPOSE

Glycogen synthase kinase-3 (GSK-3) affects neuropathological events associated with Alzheimeŕs disease (AD) such as hyperphosphorylation of the protein, tau. GSK-3beta expression, enzyme activity and tau phosphorylated at AD-relevant epitopes are elevated in juvenile rodent brains. Here, we assess five GSK-3beta inhibitors and lithium in lowering phosphorylated tau (p-tau) and GSK-3beta enzyme activity levels in 12-day old postnatal rats.

EXPERIMENTAL APPROACH

Brain levels of inhibitors following treatment in vivo were optimized based on pharmacokinetic data. At optimal doses, p-tau (Ser(396)) levels in brain tissue was measured by immunoblotting and correlated with GSK-3beta enzyme activities in the same tissues. Effects of GSK inhibitors on p-tau, GSK-3beta activities and cell death were measured in a human neuronal cell line (LUHMES).

KEY RESULTS

Lithium and CHIR98014 reduced tau phosphorylation (Ser(396)) in the cortex and hippocampus of postnatal rats, while Alsterpaullone and SB216763 were effective only in hippocampus. AR-A014418 and Indirubin-3'-monoxime were ineffective in either brain region. Inhibition of p-tau in brain required several-fold higher levels of GSK inhibitors than the IC(50) values obtained in recombinant or cell-based GSK-3beta enzyme activity assays. The inhibitory effect on GSK-3beta activity ex vivo correlated with protection against cell death and decrease of p-tau- in LUHMES cells, using low microM inhibitor concentrations.

CONCLUSIONS AND IMPLICATIONS

Selective small-molecule inhibitors of GSK-3 reduce tau phosphorylation in vivo. These findings corroborate earlier suggestions that GSK-3beta may be an attractive target for disease-modification in AD and related conditions where tau phosphorylation is believed to contribute to disease pathogenesis.

Structure-activity analysis of guanidine group in agmatine for brain agmatinase

To identify a selective inhibitor of mammalian agmatinase, screening was performed on four analogues of agmatine with modifications directly to the guanidine group, six analogues with modifications to the carbon-amine chain, and one analogue with modifications at both ends of the molecule. Control compounds were aminoguanidine and 7-nitroindazole, known inhibitors of the three isoforms (i, e, n) of nitric oxide synthase (NOS), and arcaine, a known inhibitor of the glutamate NMDA receptor. These compounds were compared for inhibition of rat agmatinase and arginine decarboxylase (ADC) activities. Results were studied by ab initio Hartee-Fock descriptors based on optimized geometries and van der Waals radii. Linear correlations were obtained using various geometric and electronic descriptors of the carbon (C), nitrogen (N), and hydrogen (H) atoms in the guanidine moiety. The best fit equation for percent activity remaining of rat agmatinase was = 0.3225 D + 72.76 D1916 + 64.97 D1920 - 192.58 H21 - 253.09 (r = 0.89), where D is the calculated dipole moment, D1916 and D1920 are the N19-N16 and N19-N20 distances, respectively, and H21 is the charge on H21. This agmatinase equation is distinct from the equations fit for ADC, the three NOS isoforms, and inhibition of NMDA receptor binding.

[Epigenetic modification of the genetic material. Genomic imprinting and its significance for disease in human beings]

Genomic imprinting is the epigenetic differential marking of maternally and paternally inherited alleles of specific genes or chromosomal subregions during gametogenesis, leading after fertilization to differential expression during development. Expression is thus monoallelic, with one parental allele being expressed, the other silenced. Imprinting implies the existence of a reversible imprinting signal, which is erased in the gonads to be reset according to the sex of the individual. Mutations in imprinted genes are not inherited in a regular Mendelian fashion. The number of identified imprinted genes is now around 35. Three congenital human disorders are known to be caused by errors in the expression pattern of imprinted genes: Prader-Willi syndrome, Angelman syndrome and Beckwith-Wiedemann syndrome. A number of cancers are also caused by errors in imprinted genes.

Analysis of the hydrology and flow of nitrogen in 17 Danish catchments

In the search for tools for evaluating the effects of national action plans combating diffuse nutrient pollution causing eutrophication of surface waters, a study of the nitrogen (N) flow in 17 Danish agricultural catchments was carried out. Data on N input and N harvest for the agricultural year of 1993/1994 was obtained from questionnaire surveys facilitating the set up of N balances. Net export of N from the catchments measured at the outlet was obtained from time-series of stream water chemistry and discharge from 1993-1997. N leaching from the root zone of each field was calculated using an empirical model. A physically based lumped rainfall-runoff model was used for separating the hydrograph time-series into three runoff components: baseflow, interflow and overland flow. Large regional variations in net N input were found ranging from 62 kg N ha(-1) yr(-1) in the loamy eastern part of the country dominated by cereal production to 137 kg N ha(-1) yr(-1) in the western part characterised by less fertile sandy soils and dominated by animal husbandry. N leaching from the root zone showed a corresponding variation with regional averages ranging from 34.5 kg N ha(-1) yr(-1) to 90.9 kg N ha(-1) yr(-1). No similar regional pattern could however be found regarding net N export, and no relationship could be established between net N export and root zone N leaching. This finding was ascribed to a varying and in some catchments very high (>80%) N retention during subsurface transport to the stream. The hydrological modelling revealed that loamy catchments had a high proportion of quick flow (overland flow + interflow), whereas baseflow dominated the sandy catchments. Further, a highly significant relationship between N retention and proportion of quick flow was found emphasising the importance of understanding the hydrological pathways. This should be taken into consideration when evaluating the N loading of surface waters resulting from a given agricultural practice and the effects of possible changes in this practice.

Synthesis of α-Vinyl Amino Acids

This chapter presents procedures for the synthesis of α-vinyl amino acids, in which the usual α-proton is replaced by an unsubstituted vinyl group (Fig. 1). The parent member of this family, α-vinylglycine (R≠H), is a natural product (1,2) and acts as a suicide substrate for a number of PLP-dependent enzymes (4-9). Higher members of this family (R≠H) have also been synthesized (10-12). Several including α-vinyl-m-tyrosine (13-15), α-vinyl-DOPA (13-15), α-vinylglutamate (16), α-vinylornithine (17), α-vinyllysine (18), and α-vinylarginine (18) are Trojan horse inhibitors of their cognate amino acid decarboxylases (AADCs). Such (appropriately labeled) AADC inhibitors may also have potential as reagents for positron emission tomography (19). Fig. 1. Generic structure for α-vinyl amino acids.

Genetic analysis of the minimal replicon of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid

Using a combination of mutagenesis with the transposon gamma delta and polymerase chain reaction subcloning, the essential elements of the replication region of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid have been identified. An open reading frame, coding for a protein with homology to Rep proteins from other Lactococcus plasmids, is essential. This protein is trans-acting and could not be replaced by the Rep protein from another Lactococcus plasmid. A second open reading frame immediately downstream from the first could be removed or inactivated with no apparent effect on plasmid replication. A region containing two 10 bp direct repeats and three tandem repeats of a 22 bp sequence, immediately upstream of the essential open reading frame, is also essential and probably includes the origin of replication. A 181-bp DNA fragment containing this region was sufficient to allow replication in Lactococcus if the trans-acting protein was provided on another replicon. Single-stranded replication intermediates could not be detected, suggesting that the citrate plasmid uses theta replication rather than rolling-circle replication.

Computed tomography of intralobar bronchopulmonary sequestration supplied from the renal artery

Intralobar bronchopulmonary sequestration typically receives systemic arterial supply from the descending thoracic or upper abdominal aorta. Isolated reports have documented supply from branch vessels of the abdominal aorta, including the celiac axis and inferior phrenic artery. We report a case of the anomalous arterial supply arising from the right renal artery.

Oesophageal stricture and dysphagia after endoscopic sclerotherapy for bleeding varices

Oesophageal stricture and dysphagia after endoscopic sclerotherapy of oesophageal varices were assessed with regard to occurrence and severity and the relation to the treatment. We followed 34 patients for three to 47 months who had two to 25 treatments with submucosal, paravenous injections of polidocanol (3%). Twenty patients (59%) developed stricture or dysphagia; 14 both dysphagia and endoscopically verified stricture, two dysphagia without stricture, and four stricture without dysphagia. Both phenomena occurred intermittently and often independent of each other, but occupied median 38% of the observation time in these 20 patients. The patients developing strictures had received significantly more treatments and greater amount of sclerosant, and they had significantly more preceding mucosal necroses. The varices were eradicated to about the same degree and the incidence of recurrent haemorrhage was the same as in the patients who had not developed stricture.

Mammography directed wire marking of nonpalpable breast lesions. A consecutive biopsy study of 100 patients

Among 665 patients referred for breast complaints, 100 women (15%) had mammographically detected nonpalpable lesions suspected of malignancy. Using a mammography directed hook wire marking, 115 excisional biopsies were carried out. A correct biopsy containing the lesion was obtained in 113 instances. There were 2 failures, due to displacements of the wire in one case and surgical inexperience in another case. Two patients had minor wound complications. Invasive carcinoma was found in 12 and carcinoma in situ in 4 biopsies, i.e., a cancer rate of 16% of patients and 14% of biopsies. The biopsy procedure was simple, time saving, and acceptable of patients. The excisions were small and the cosmetic results excellent. During mammography for control of wire position, and during dressing and surgical manipulations the flexible hooked wire remained as originally placed in all cases but one.

Pituitary-testicular function in patients with chronic alcoholism

Testis and liver histology, and pituitary-testicular function were studied in thirty chronic alcoholics. Severe reduction of spermatogenesis was found in 30% and in these patients serum follicle stimulating hormone and prolactin concentrations were significantly higher. There was no correlation between abnormalities in the liver and testis. The serum testosterone was normal in most cases. Sexual dysfunction and testicular atrophy occurred in more than half of the patients and were not related to liver disease. Testicular disorder in chronic alcoholism may be independent of liver disease.