In vivo molecular targeted radiotherapy

Unsealed radionuclides have been in clinical therapeutic use for well over half a century. Following the early inappropriate clinical administrations of radium salts in the early 20th century, the first real clinical benefits became evident with the use of 131I-sodium iodide for the treatment of hypothyroidism and differentiated thyroid carcinoma and 32P-sodium phosphate for the treatment of polycythaemia vera. In recent years the use of bone seeking agents 89Sr, 153Sm and 186Re for the palliation of bone pain have become widespread and considerable progress has been evident with the use of 131I-MIBG and 90Y-somatostatin receptor binding agents. Although the use of monoclonal antibody based therapeutic products has been slow to evolve, the start of the 21st century has witnessed the first licensed therapeutic antibody conjugates based on 90Y and 131I for the treatment of non-Hodgkin's lymphoma. The future clinical utility of this form of therapy will depend upon the development of radiopharmaceutical conjugates capable of selective binding to molecular targets. The availability of some therapeutic radionuclides such as 188Re produced from the tungsten generator system which can produce activity as required over many months, may make this type of therapy more widely available in some remote and developing countries

Hydrophilic and lipophilic radiopharmaceuticals as tracers in pharmaceutical development: In vitro – In vivo studies

BACKGROUND: Scintigraphic studies have been performed to assess the release, both in vitro and in vivo, of radiotracers from tablet formulations. Four different tracers with differing physicochemical characteristics have been evaluated to assess their suitability as models for drug delivery. METHODS: In-vitro disintegration and dissolution studies have been performed at pH 1, 4 and 7. In-vivo studies have been performed by scintigraphic imaging in healthy volunteers. Two hydrophilic tracers, ((99m)Tc-DTPA) and ((99m)Tc-MDP), and two lipophilic tracers, ((99m)Tc-ECD) and ((99m)Tc-MIBI), were used as drug models. RESULTS: Dissolution and disintegration profiles, differed depending on the drug model chosen. In vitro dissolution velocity constants indicated a probable retention of the radiotracer in the formulation. In vivo disintegration velocity constants showed important variability for each radiopharmaceutical. Pearson statistical test showed no correlation between in vitro drug release, and in vivo behaviour, for (99m)Tc-DTPA, (99m)Tc-ECD and (99m)Tc-MIBI. High correlation coefficients were found for (99m)Tc-MDP not only for in vitro dissolution and disintegration studies but also for in vivo scintigraphic studies. CONCLUSION: Scintigraphic studies have made a significant contribution to the development of drug delivery systems. It is essential, however, to choose the appropriate radiotracers as models of drug behaviour. This study has demonstrated significant differences in release patterns, depending on the model chosen. It is likely that each formulation would require the development of a specific model, rather than being able to use a generic drug model on the basis of its physicochemical characteristics

Non-linearity of the collagen triple helix in solution and implications for collagen function

Collagen adopts a characteristic supercoiled triple helical conformation which requires a repeating (Xaa-Yaa-Gly)n sequence. Despite the abundance of collagen, a combined experimental and atomistic modelling approach has not so far quantitated the degree of flexibility seen experimentally in the solution structures of collagen triple helices. To address this question, we report an experimental study on the flexibility of varying lengths of collagen triple helical peptides, composed of six, eight, ten and twelve repeats of the most stable Pro-Hyp-Gly (POG) units. In addition, one unblocked peptide, (POG)10unblocked, was compared with the blocked (POG)10 as a control for the significance of end effects. Complementary analytical ultracentrifugation and synchrotron small angle X-ray scattering data showed that the conformations of the longer triple helical peptides were not well explained by a linear structure derived from crystallography. To interpret these data, molecular dynamics simulations were used to generate 50 000 physically realistic collagen structures for each of the helices. These structures were fitted against their respective scattering data to reveal the best fitting structures from this large ensemble of possible helix structures. This curve fitting confirmed a small degree of non-linearity to exist in these best fit triple helices, with the degree of bending approximated as 4–17° from linearity. Our results open the way for further studies of other collagen triple helices with different sequences and stabilities in order to clarify the role of molecular rigidity and flexibility in collagen extracellular and immune function and disease

Levosimendan for the prevention of acute organ dysfunction in sepsis

BACKGROUND Levosimendan is a calcium-sensitizing drug with inotropic and other properties that may improve outcomes in patients with sepsis. METHODS We conducted a double-blind, randomized clinical trial to investigate whether levosimendan reduces the severity of organ dysfunction in adults with sepsis. Patients were randomly assigned to receive a blinded infusion of levosimendan (at a dose of 0.05 to 0.2 μg per kilogram of body weight per minute) for 24 hours or placebo in addition to standard care. The primary outcome was the mean daily Sequential Organ Failure Assessment (SOFA) score in the intensive care unit up to day 28 (scores for each of five systems range from 0 to 4, with higher scores indicating more severe dysfunction; maximum score, 20). Secondary outcomes included 28-day mortality, time to weaning from mechanical ventilation, and adverse events. RESULTS The trial recruited 516 patients; 259 were assigned to receive levosimendan and 257 to receive placebo. There was no significant difference in the mean (±SD) SOFA score between the levosimendan group and the placebo group (6.68±3.96 vs. 6.06±3.89; mean difference, 0.61; 95% confidence interval [CI], −0.07 to 1.29; P=0.053). Mortality at 28 days was 34.5% in the levosimendan group and 30.9% in the placebo group (absolute difference, 3.6 percentage points; 95% CI, −4.5 to 11.7; P=0.43). Among patients requiring ventilation at baseline, those in the levosimendan group were less likely than those in the placebo group to be successfully weaned from mechanical ventilation over the period of 28 days (hazard ratio, 0.77; 95% CI, 0.60 to 0.97; P=0.03). More patients in the levosimendan group than in the placebo group had supraventricular tachyarrhythmia (3.1% vs. 0.4%; absolute difference, 2.7 percentage points; 95% CI, 0.1 to 5.3; P=0.04). CONCLUSIONS The addition of levosimendan to standard treatment in adults with sepsis was not associated with less severe organ dysfunction or lower mortality. Levosimendan was associated with a lower likelihood of successful weaning from mechanical ventilation and a higher risk of supraventricular tachyarrhythmia. (Funded by the NIHR Efficacy and Mechanism Evaluation Programme and others; LeoPARDS Current Controlled Trials number, ISRCTN12776039.

Trial Protocol: Randomised controlled trial of the effects of very low calorie diet, modest dietary restriction, and sequential behavioural programme on hunger, urges to smoke, abstinence and weight gain in overweight smokers stopping smoking

Background\ud Weight gain accompanies smoking cessation, but dieting during quitting is controversial as hunger may increase urges to smoke. This is a feasibility trial for the investigation of a very low calorie diet (VLCD), individual modest energy restriction, and usual advice on hunger, ketosis, urges to smoke, abstinence and weight gain in overweight smokers trying to quit. \ud \ud Methods\ud This is a 3 armed, unblinded, randomized controlled trial in overweight (BMI > 25 kg/$m^2$), daily smokers (CO > 10 ppm); with at least 30 participants in each group. Each group receives identical behavioural support and NRT patches (25 mg(8 weeks),15 mg(2 weeks),10 mg(2 weeks)). The VLCD group receive a 429-559 kcal/day liquid formula beginning 1 week before quitting and continuing for 4 weeks afterwards. The modest energy restricted group (termed individual dietary and activity planning(IDAP)) engage in goal-setting and receive an energy prescription based on individual basal metabolic rate(BMR) aiming for daily reduction of 600 kcal. The control group receive usual dietary advice that accompanies smoking cessation i.e. avoiding feeling hungry but eating healthy snacks. After this, the VLCD participants receive IDAP to provide support for changing eating habits in the longer term; the IDAP group continues receiving this support. The control group receive IDAP 8 weeks after quitting. This allows us to compare IDAP following a successful quit attempt with dieting concurrently during quitting. It also aims to prevent attrition in the unblinded, control group by meeting their need for weight management. Follow-up occurs at 6 and 12 months. \ud \ud Outcome measures include participant acceptability, measured qualitatively by semi-structured interviewing and quantitatively by recruitment and attrition rates. Feasibility of running the trial within primary care is measured by interview and questionnaire of the treatment providers. Adherence to the VLCD is verified by the presence of urinary ketones measured weekly. Daily urges to smoke, hunger and withdrawal are measured using the Mood and Physical Symptoms Scale-Combined (MPSS-C) and a Hunger Craving Score (HCS). 24 hour, 7 day point prevalence and 4-week prolonged abstinence (Russell Standard) is confirmed by CO < 10 ppm. Weight, waist and hip circumference and percentage body fat are measured at each visit. \ud \ud Trial Registration\ud Current controlled trials ISRCTN83865809\ud \u

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Changes in microphytobenthos fluorescence over a tidal cycle: implications for sampling designs

Intertidal microphytobenthos (MPB) are important primary producers and provide food for herbivores in soft sediments and on rocky shores. Methods of measuring MPB biomass that do not depend on the time of collection relative to the time of day or tidal conditions are important in any studies that need to compare temporal or spatial variation, effects of abiotic factors or activity of grazers. Pulse amplitude modulated (PAM) fluorometry is often used to estimate biomass of MPB because it is a rapid, non-destructive method, but it is not known how measures of fluorescence are altered by changing conditions during a period of low tide. We investigated this experimentally using in situ changes in minimal fluorescence (F) on a rocky shore and on an estuarine mudflat around Sydney (Australia), during low tides. On rocky shores, the time when samples are taken during low tide had little direct influence on measures of fluorescence as long as the substratum is dry. Wetness from wave-splash, seepage from rock pools, run-off, rainfall, etc., had large consequences for any comparisons. On soft sediments, fluorescence was decreased if the sediment dried out, as happens during low-spring tides on particularly hot and dry days. Surface water affected the response of PAM and therefore measurements used to estimate MPB, emphasising the need for care to ensure that representative sampling is done during low tide

Synthesis, in Vitro Evaluation, and Radiolabelling of Fluorinated Puromycin Analogues: Potential Candidates for PET Imaging of Protein Synthesis

There is currently no ideal radiotracer for imaging protein synthesis rate (PSR) by positron emission tomography (PET). Existing fluorine-18 labelled amino acid-based radiotracers predominantly visualize amino acid transporter processes, and in many cases they are not incorporated into nascent proteins at all. Others are radiolabelled with the short half-life positron emitter carbon-11 which is rather impractical for many PET centers. Based on the puromycin (6) structural manifold, a series of 10 novel derivatives of 6 was prepared via Williamson ether synthesis from a common intermediate. A bioluminescence assay was employed to study their inhibitory action on protein synthesis which identified fluoroethyl analogue (7b) as a lead compound. The fluorine-18 analogue was prepared via nucleophilic substitution of the corresponding tosylate precursor in modest radiochemical yield 2±0.6% and excellent radiochemical purity (>99%) and showed complete stability over 3 h at ambient temperature.H.M.B. acknowledges the Royal Society of Chemistry Research Fund for partial funding of this project and the NIHR Clinical Research Network (East Midlands) for funding her post. We are grateful to the U.K. Medical Research Council (MRC) for funding (Grant G9219778). C.T. was supported by the MRC/University of Nottingham Doctoral Training Program. S.M.S. acknowledges the EPSRC Mass Spectrometry Facility for funding her attendance at the Mass Spectrometry Summer School 2016. Dr. W. Chan (University of Nottingham) is acknowledged for access to synthetic chemistry facilities. The EPSRC Mass Spectrometry Facility at the University of Swansea is acknowledged for performing HRMS analyses