A practical guide to the interpretation of PK/PD profiles of longer-acting analogue insulins. Part one: The principles of glucose clamp studies

Glucose clamp studies are used to determine pharmacokinetics (PK) and  pharmacodynamics (PD) of analogue insulins. With the development of longer-acting basal analogue insulins, including glargine 300 (Gla-300) and insulin degludec (IDeg), results from numerous glucose clamp studies are readily available. However, interpreting PK/PD profiles in a scientifically  sound manner can be a challenging feat. This is the first in a series of publications that will suggest practical tips for interpreting and comparing results from glucose clamp studies. Variations in the glucose clamp  methodology, duration of clamp studies and glucose clamp targets influence the study design and results significantly. Selection of study  populations, including healthy patients or patients with Type 1 or 2 diabetes mellitus, has important implications. The dose of study insulin should  reflect that of the general treatment population, and ideally steady-state conditions should be used. During the study the plasma insulin  concentration and glucose infusion rate describe the pharmacokinetics and pharmacodynamics of the study insulin. With these practical tips in mind, results of glucose clamp studies can be interpreted in a scientifically correct manner. The next article in this series will discuss the interpretation of PK/PD profiles using two newly developed longer-acting basal analogue insulins: Gla-300 and IDeg.Keywords: analogue insulins, glucose clamp, time–action profile, glucose infusion rate, pharmacokinetic

Limitations of the 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyl-2H-tetrazolium bromide (MTT) assay when compared to three commonly used cell enumeration assays

BACKGROUND : The tetrazolium-based MTT assay has long been regarded as the gold standard of cytotoxicity assays as it is highly sensitive and has been miniaturised for use as a high-throughput screening assay. However, various reports refer to interference by different test compounds, including the glycolysis inhibitor 3-bromopyruvate, with the conversion of the dye to coloured formazan crystals. This study assessed the linear range and reproducibility of three commonly used cell enumeration assays; the neutral red uptake (NRU), resazurin reduction (RES) and sulforhodamine B (SRB) assays, in comparison to the MTT assay. Interference between the MTT assay and three glycolysis inhibitors, 2-deoxyglucose, 3-bromopyruvate and lonidamine, was investigated. RESULTS : Data indicate that the NRU, RES and SRB assays showed the smallest variability across the linear range, while the largest variation was observed for the MTT assay. This implies that these assays would more accurately detect small changes in cell number than the MTT assay. The SRB assay provided the most reproducible results as indicated by the coefficient of determination after a limited number of experiments. The SRB assay also produced the lowest variance in the derived 50% inhibitory concentration (IC50), while IC50 concentrations of 3-bromopyruvate could not be detected using either the MTT or RES assays after 24 hours incubation. Interference in the MTT assay was observed for all three tested glycolysis inhibitors in a cell-free environment. No interferences were observed for the NRU, SRB or RES assays. CONCLUSIONS : This study demonstrated that the MTT assay was not the best assay in a number of parameters that must be considered when a cell enumeration assay is selected: the MTT assay was less accurate in detecting changes in cell number as indicated by the variation observed in the linear range, had the highest variation when the IC50 concentrations of the glycolysis inhibitors were determined, and interference between the MTT assay and all the glycolysis inhibitors tested were observed. The SRB assay performed best overall considering all of the parameters, suggesting that it is the most suitable assay for use in preclinical screening of novel therapeutic compounds with oxido-reductive potential.Additional file 1: The IC50 concentrations of 3-bromopyruvate calculated for MCF-7 cells after 24 or 72 hour incubation calculated per experimental repeat. Results are indicated as IC50 ± SEM. Where no values are given these could not be calculated as the assay reported relative cell survival of greater than 50% at the tested concentrations (n = 4).Additional file 2: Interference of three glycolysis inhibitors with the NRU, RES and SRB assays in cell-free systems (n = 3).The National Research Foundation of South Africa (TTK1207072152)http://www.biomedcentral.com/bmcpublichealtham201

Incidence of hypoglycaemia in the South African population with diabetes: Results from the IDMPS Wave 7 study

Objectives: Management of diabetes is a balancing act of preventing a state of hyperglycaemia while avoiding episodes of hypoglycaemia. Limited information is currently available on the incidence of hypoglycaemia in South African people diagnosed with diabetes. Data regarding the management of diabetes and incidence of hypoglycaemia in the South African population was collected as part of Wave 7 of the International Diabetes Management Practices Study (IDMPS).Design and methods: During this observational study the first 10 adult individuals with type 2 diabetes and the first five adult individuals with type 1 diabetes presenting to a study site during the two-week study period were enrolled.Setting: Patients were enrolled from the private healthcare sector in South Africa only.Subjects: A total of 445 individuals (49 diagnosed with T1D, 396 diagnosed with T2D) were included.Outcome measures: Glycated haemoglobin and hypoglycaemia data were recorded for each patient.Results: Of the patients who reported experiencing hypoglycaemia, 48.6% (17/35) among T1D individuals and 67.8% (40/71) among T2D individuals experienced hypoglycaemia over a four-week period. Furthermore, in patients who discontinued insulin treatment (n = 11), fear of hypoglycaemia was reported to influence adherence to insulin treatment by 27.3% in T1D and T2D individuals. Of the 148 patients not achieving their HbA1c target, 23.0% reported fear of hypoglycaemia as a reason.Conclusions: This report demonstrates the need to address hypoglycaemia and fear of hypoglycaemia in the South African diabetes population

RNA-based therapy in the management of lipid disorders: a review

This review focuses on antisense oligonucleotides and small interfering ribonucleic acid therapies approved or under development for the management of lipid disorders. Recent advances in RNA-based therapeutics allow tissue-specific targeting improving safety. Multiple potential target proteins have been identified and RNA-based therapeutics have the potential to significantly improve outcomes for patients with or at risk for atherosclerotic cardiovascular disease. The advantages of RNA-based lipid modifying therapies include the ability to reduce the concentration of almost any target protein highly selectively, allowing for more precise control of metabolic pathways than can often be achieved with small molecule-based drugs. RNA-based lipid modifying therapies also make it possible to reduce the expression of target proteins for which there are no small molecule inhibitors. RNA-based therapies can also reduce pill burden as their administration schedule typically varies from weekly to twice yearly injections. The safety profile of most current RNA-based lipid therapies is acceptable but adverse events associated with various therapies targeting lipid pathways have included injection site reactions, inflammatory reactions, hepatic steatosis and thrombocytopenia. While the body of evidence for these therapies is expanding, clinical experience with these therapies is currently limited in duration and the results of long-term studies are eagerly awaited

Long-term safety and efficacy of alirocumab in South African patients with heterozygous familial hypercholesterolaemia : the ODYSSEY open-label extension study

BACKGROUND : Alirocumab reduces low-density lipoprotein cholesterol (LDL-C) levels by up to 61%. The ODYSSEY Open-Label Extension study investigated the effect of alirocumab in patients with heterozygous familial hypercholesterolaemia (HeFH) over 144 weeks. METHODS : Eligible patients with HeFH had completed an earlier double-blind, randomised, placebo-controlled parent study. Patients were initiated on 75 mg alirocumab Q2W subcutaneous (SC) unless baseline LDL-C was > 8.9 mmol/l, in which case they received 150 mg alirocumab Q2W. Dose titration to 150 mg Q2W was at the investigator’s discretion. RESULTS : The study enrolled 167 patients and the parent study mean (± SD) baseline LDL-C level was 3.65 ± 1.9 mmol/l. Mean LDL-C level was reduced by 48.7% at week 144; mean on-treatment LDL-C was 2.30 ± 1.24 mmol/l. Eight patients reported injection-site reactions, with one treatment discontinuation. Treatment emergent anti-drug antibodies were identified in five patients but these did not affect the efficacy. CONCLUSION : Alirocumab effectively and safely reduced LDL-C in these patients.http://www.cvja.co.zahj2020Physiolog

Exploiting drug synergism to extend the application of oestrone analogues

Most successful treatment strategies for neosplasms comprise combinations of anti-cancer drugs with different mechanisms of action and side effect profiles. This strategy allows for the use of anti-cancer agents at the lowest possible concentrations, translating into fewer adverse events reported in the clinical setting. To identify synergistic combinations in vitro, the Median Effect equation of Chou and Talalay is often employed. In this study two characteristics which distinguish malignant cells from non-malignant cells were targeted using combination therapy: enhanced proliferation rate and altered energy production. The increased proliferation rate of tumourigenic cells were targeted using antimitotic oestrone analogues, ESE-15-ol and ESE-16. These oestrone analogues were in silico designed from the potent anti-cancer compound 2-methoxyoestradiol. Six glycolysis inhibitors were selected for this study in order to selectively target the aerobic glycolysis preferred by malignant cells for energy production. The glycolysis inhibitors included the glucose analogue 2-deoxyglucose, the hexokinase inhibitor 3-bromopyruvate, the anti-spermatogenic agent lonidamine, the small molecule fasentin, the flavonoid quercetin (QUER) and the HIV-protease inhibitor indinavir (IND). The potential synergy of combinations of anti-mitotic oestrone analogues and glycolysis inhibitors were investigated after 72 h using the sulforhodamine B cell enumeration assay and in vitro breast cancer models presenting the three main phenotypic subtypes of clinical breast cancer. Using CalcuSYN software based on the Median Effect equation, a combination index value is calculated for each tested combination indicating the degree of synergy achieved. Based on the combination index values and published toxicity reports, combinations of ESE- 15-ol and ESE-16 with either IND or QUER were selected for further study on the MCF-7 and MDA-MB-231 breast adenocarcinoma cells. The sequence of toxicity induced by the selected synergistic combinations was investigated by evaluating various intracellular parameters. It was demonstrated that selected combinations of oestrone analogues and glycolysis inhibitors resulted in generation of reactive oxygen species after 6 h, which is regarded as an indicator of early toxicity. After 24 h the catabolic adaptive mechanism of autophagy was not induced by any combination. However, as autophagy is a dynamic process its role later in the sequence of toxicity cannot be excluded. Ultrastructure studies indicate the formation of multivesicular bodies in combination treated cells. Data indicate that combinations of oestrone analogues with IND caused hyperpolarisation of the mitochondrial membrane potential which suggests inhibition of ATP synthesis, activation of the extrinsic pathway and the induction of apoptotic and necrotic cell death after 72 h. Treatment with combinations of oestrone analogues with QUER resulted dissipation of mitochondrial membrane potential, activation of caspases 9 and -3/7 which culminated in the induction of apoptotic and necrotic cell death after 72 h. As tumourigenic cells readily induce the formation of new blood vessels and invade nontumourigenic tissue, the ability of the selected combinations to inhibit angiogenesis was investigated. Combinations of oestrone analogues with IND or QUER resulted in decreased secretion of pro-angiogenic vascular endothelial growth factor, inhibited the formation of complex tubule networks of endothelial cells and reduced migration of breast adenocarcinoma and endothelial cells. This suggests that these combinations have anti-angiogenic properties. During this study the potential synergy of oestrone analogues and glycolysis inhibitors were investigated as a means of effectively eradicating breast cancer using low doses of anticancer agents. Synergistic combinations of oestrone analogues and IND or QUER were identified on MCF-7 and MDA-MB-231 breast adenocarcinoma cells. Data indicate that these combinations activate different molecular pathways to induce cell death via apoptosis and necrosis and inhibit various stages of angiogenesis. It is therefore proposed that these combinations have potential as anti-metastatic therapy.Thesis (PhD)--University of Pretoria, 2016.tm2016PharmacologyPh

A practical guide to the interpretation of PK/PD profiles of longer-acting analogue insulins. Part two: Insulin degludec vs. insulin glargine U300

Glucose clamp studies form an integral part of the early development of insulin therapies. Data generated in these studies are used to establish pharmacokinetic (PK) and pharmacodynamic (PD) profiles of the agents, but methodological differences confound comparison of results from different glucose clamp studies. The first part of this series on glucose clamp studies discussed practical tips for the interpretation of glucose clamp studies. The second part of the series compares the PK/PD profiles of longer-acting basal analogue insulins, insulin degludec (IDeg) and insulin glargine U300 (Gla-300). The patient populations for glucose clamp studies with these analogue insulins differ, and therefore direct comparison of the data is not always possible. The maximum duration of action of IDeg is reported as 42 h and that of Gla-300 as 36 h, translating to 24 h coverage. The plasma insulin concentration of IDeg is 56 times that of Gla-300. Results from phase III clinical trials for these analogue insulins confirm the predictability and low within-subject variability observed in glucose clamp studies. Insight into the PK/PD profiles of longeracting basal analogue insulins allows the treating physician to utilise these characteristics to optimise the treatment of their patients with diabetes.Keywords: analogue insulins, glucose clamp, time–action profile, pharmacokinetics, pharmacodynamic

A meta-theoretical glimpse into the future of South African corporate communication management

This article provides a concise discussion of meta-theoretical (critical-rhetorical, feminist and postmodernistic) approaches towards corporate communication management utilising meta-ethical points of departure with the aim of providing a glimpse into the meta-theoretical future of corporate communication management. The discussion is supplemented by an analysis of the challenges that face organisations in the fast-changing environment of the twenty-first century and corporate communication management as a critical/strategic management function that has the potential to assist organisations in adapting and remaining relevant to their environment, and by implication to the needs of their key internal and external stakeholders. The article is concluded by an explication of corporate communication management as being inextricably linked to ethical conduct and a product of the amalgamation of different meta-theoretical approaches, which interprets and advances the values of both stakeholders and the organisation in a manner that socially and ethically responsible, dialogical mutually adaptive, and contributes to democratising the organisation's decision-making and management processes. This poses challenges to, and insight into, the meta-theoretical approach held while engaging in discourse on the comprehensive nature of corporate communication management.Strategic managemen

A practical guide to the interpretation of PK/PD profiles of longer-acting analogue insulins. Part one: The principles of glucose clamp studies

Glucose clamp studies are used to determine pharmacokinetics (PK) and pharmacodynamics (PD) of analogue insulins. With the development of longer-acting basal analogue insulins, including glargine 300 (Gla-300) and insulin degludec (IDeg), results from numerous glucose clamp studies are readily available. However, interpreting PK/PD profiles in a scientifically sound manner can be a challenging feat. This is the first in a series of publications that will suggest practical tips for interpreting and comparing results from glucose clamp studies. Variations in the glucose clamp methodology, duration of clamp studies and glucose clamp targets influence the study design and results significantly. Selection of study populations, including healthy patients or patients with Type 1 or 2 diabetes mellitus, has important implications. The dose of study insulin should reflect that of the general treatment population, and ideally steady-state conditions should be used. During the study the plasma insulin concentration and glucose infusion rate describe the pharmacokinetics and pharmacodynamics of the study insulin. With these practical tips in mind, results of glucose clamp studies can be interpreted in a scientifically correct manner. The next article in this series will discuss the interpretation of PK/PD profiles using two newly developed longer-acting basal analogue insulins: Gla-300 and IDeg

A practical guide to the interpretation of PK/PD profiles of longer-acting analogue insulins. Part one : the principles of glucose clamp studies

Glucose clamp studies are used to determine pharmacokinetics (PK) and pharmacodynamics (PD) of analogue insulins. With the development of longer-acting basal analogue insulins, including glargine 300 (Gla-300) and insulin degludec (IDeg), results from numerous glucose clamp studies are readily available. However, interpreting PK/PD profiles in a scientifically sound manner can be a challenging feat. This is the first in a series of publications that will suggest practical tips for interpreting and comparing results from glucose clamp studies. Variations in the glucose clamp methodology, duration of clamp studies and glucose clamp targets influence the study design and results significantly. Selection of study populations, including healthy patients or patients with Type 1 or 2 diabetes mellitus, has important implications. The dose of study insulin should reflect that of the general treatment population, and ideally steady-state conditions should be used. During the study the plasma insulin concentration and glucose infusion rate describe the pharmacokinetics and pharmacodynamics of the study insulin. With these practical tips in mind, results of glucose clamp studies can be interpreted in a scientifically correct manner. The next article in this series will discuss the interpretation of PK/PD profiles using two newly developed longer-acting basal analogue insulins: Gla-300 and IDeg.http://www.tandfonline.com/loi/oemd20am2018Pharmacolog