Development of a PET Tracer for OGA with Improved Kinetics in the Living Brain.

O-GlcNAcylation is thought to play a role in the development of tau pathology in Alzheimer's disease because of its ability to modulate tau's aggregation propensity. O-GlcNAcylation is regulated by 2 enzymes: O-GlcNAc transferase and O-GlcNAcase (OGA). Development of a PET tracer would therefore be an essential tool for developing therapeutic small-molecule inhibitors of OGA, enabling clinical testing of target engagement and dose selection. Methods: A collection of small-molecule compounds was screened for inhibitory activity and high-affinity binding to OGA, as well as favorable PET tracer attributes (multidrug resistance protein 1 efflux, central nervous system PET multiparameter optimization, etc.). Two lead compounds with high affinity and selectivity for OGA were selected for further profiling, including OGA binding to tissue homogenate using a radioligand competition binding assay. In vivo pharmacokinetics were established using a microdosing approach with unlabeled compounds in rats. In vivo imaging studies were performed in rodents and nonhuman primates (NHPs) with 11C-labeled compounds. Results: Two selected candidates, BIO-735 and BIO-578, displayed promising attributes in vitro. After radiolabeling with tritium, [3H]BIO-735 and [3H]BIO-578 binding in rodent brain homogenates demonstrated dissociation constants of 0.6 and 2.3 nM, respectively. Binding was inhibited, concentration-dependently, by homologous compounds and thiamet G, a well-characterized and structurally diverse OGA inhibitor. Imaging studies in rats and NHPs showed both tracers had high uptake in the brain and inhibition of binding to OGA in the presence of a nonradioactive compound. However, only BIO-578 demonstrated reversible binding kinetics within the time frame of a PET study with a 11C-labeled molecule to enable quantification using kinetic modeling. Specificity of tracer uptake was confirmed with a 10 mg/kg blocking dose of thiamet G. Conclusion: We describe the development and testing of 2 11C PET tracers targeting the protein OGA. The lead compound BIO-578 demonstrated high affinity and selectivity for OGA in rodent and human postmortem brain tissue, leading to its further testing in NHPs. NHP PET imaging studies showed that the tracer had excellent brain kinetics, with full inhibition of specific binding by thiamet G. These results suggest that the tracer [11C]BIO-578 is well suited for further characterization in humans.

Quantifying blue carbon stocks and the role of protected areas to conserve coastal wetlands.

Vegetated coastal ecosystems, in particular mangroves, tidal marshes and seagrasses are highly efficient at sequestering and storing carbon, making them valuable assets for climate change mitigation and adaptation. The state of Queensland, in northeastern Australia, contains almost half of the total area of these blue carbon ecosystems in the country, yet there are few detailed regional or state-wide assessments of their total sedimentary organic carbon (SOC) stocks. We compiled existing SOC data and used boosted regression tree models to evaluate the influence of environmental variables in explaining the variability in SOC stocks, and to produce spatially explicit blue carbon estimates. The final models explained 75 % (for mangroves and tidal marshes) and 65 % (for seagrasses) of the variability in SOC stocks. Total SOC stocks in the state of Queensland were estimated at 569 ± 98 Tg C (173 ± 32 Tg C, 232 ± 50 Tg C, and 164 ± 16 Tg C from mangroves, tidal marshes and seagrasses, respectively). Regional predictions for each of Queensland's eleven Natural Resource Management regions revealed that 60 % of the state's SOC stocks occurred within three regions (Cape York, Torres Strait and Southern Gulf Natural Resource Management regions) due to a combination of high values of SOC stocks and large areas of coastal wetlands. Protected areas in Queensland play an important role in conserving SOC assets in Queensland's coastal wetlands. For example, ~19 Tg C within terrestrial protected areas, ~27 Tg C within marine protected areas and ~ 40 Tg C within areas of matters of State Environmental Significance. Using multi-decadal (1987-2020) mapped distributions of mangroves in Queensland; we found that mangrove area increased by approximately 30,000 ha from 1987 to 2020, which led to temporal fluctuations in mangrove plant and SOC stocks. We estimated that plant stocks decreased from ~45 Tg C in 1987 to ~34.2 Tg C in 2020, while SOC stocks remained relatively constant from ~107.9 Tg C in 1987 to 108.0 Tg C in 2020. Considering the level of current protection, emissions from mangrove deforestation are potentially very low; therefore, representing minor opportunities for mangrove blue carbon projects in the region. Our study provides much needed information on current trends in carbon stocks and their conservation in Queensland's coastal wetlands, while also contributing to guide future management actions, including blue carbon restoration projects.

A Visual Interpretation Algorithm for Assessing Brain Tauopathy with 18F-MK-6240 PET.

In vivo characterization of pathologic deposition of tau protein in the human brain by PET imaging is a promising tool in drug development trials of Alzheimer disease (AD). 6-(fluoro-18F)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine (18F-MK-6240) is a radiotracer with high selectivity and subnanomolar affinity for neurofibrillary tangles that shows favorable nonspecific brain penetration and excellent kinetic properties. The purpose of the present investigation was to develop a visual assessment method that provides both an overall assessment of brain tauopathy and regional characterization of abnormal tau deposition. Methods: 18F-MK-6240 scans from 102 participants (including cognitively normal volunteers and patients with AD or other neurodegenerative disorders) were reviewed by an expert nuclear medicine physician masked to each participant's diagnosis to identify common patterns of brain uptake. This initial visual read method was field-tested in a separate, nonoverlapping cohort of 102 participants, with 2 additional naïve readers trained on the method. Visual read outcomes were compared with semiquantitative assessments using volume-of-interest SUV ratio. Results: For the visual read, the readers assessed 8 gray-matter regions per hemisphere as negative (no abnormal uptake) or positive (1%-25% of the region involved, 25%-75% involvement, or >75% involvement) and then characterized the tau binding pattern as positive or negative for evidence of tau and, if positive, whether brain uptake was in an AD pattern. The readers demonstrated agreement 94% of the time for overall positivity or negativity. Concordance on the determination of regional binary outcomes (negative or positive) showed agreement of 74.3% and a Fleiss κ of 0.912. Using clinical diagnosis as the ground truth, the readers demonstrated a sensitivity of 73%-79% and specificity of 91%-93%, with a combined reader-concordance sensitivity of 80% and specificity of 93%. The average SUV ratio in cortical regions showed a robust correlation with visually derived ratings of regional involvement (r = 0.73, P < 0.0001). Conclusion: We developed a visual read algorithm for 18F-MK-6240 PET offering determination of both scan positivity and the regional degree of cortical involvement. These cross-sectional results show strong interreader concordance on both binary and regional assessments of tau deposition, as well as good sensitivity and excellent specificity supporting use as a tool for clinical trials.

Estimation of Drag Finishing Abrasive Effect for Cutting Edge Preparation in Broaching Tool.

In recent years, cutting edge preparation became a topic of high interest in the manufacturing industry because of the important role it plays in the performance of the cutting tool. This paper describes the use of the drag finishing DF cutting edge preparation process on the cutting tool for the broaching process. The main process parameters were manipulated and analyzed, as well as their influence on the cutting edge rounding, material remove rate MRR, and surface quality/roughness (Ra, Rz). In parallel, a repeatability and reproducibility R&R analysis and cutting edge radius re prediction were performed using machine learning by an artificial neural network ANN. The results achieved indicate that the influencing factors on re, MRR, and roughness, in order of importance, are drag depth, drag time, mixing percentage, and grain size, respectively. The reproducibility accuracy of re is reliable compared to traditional processes, such as brushing and blasting. The prediction accuracy of the re of preparation with ANN is observed in the low training and prediction errors 1.22% and 0.77%, respectively, evidencing the effectiveness of the algorithm. Finally, it is demonstrated that the DF has reliable feasibility in the application of edge preparation on broaching tools under controlled conditions.

Quantitative systems pharmacology model for Alzheimer's disease to predict the effect of aducanumab on brain amyloid.

Alzheimer's disease (AD) is an irreversible, progressive brain disorder that impairs memory and cognitive function. Dysregulation of the amyloid-ß (Aß) pathway and amyloid plaque accumulation in the brain are hallmarks of AD. Aducanumab is a human, immunoglobulin gamma 1 monoclonal antibody targeting aggregated forms of Aß. In phase Ib and phase III studies, aducanumab reduced Aß plaques in a dose dependent manner, as measured by standard uptake value ratio of amyloid positron emission tomography imaging. The goal of this work was to develop a quantitative systems pharmacology model describing the production, aggregation, clearance, and transport of Aß as well as the mechanism of action for the drug to understand the relationship between aducanumab dosing regimens and changes of different Aß species, particularly plaques in the brain. The model was used to better understand the pharmacodynamic effects observed in the clinical trials of aducanumab and assist in the clinical development of future Aß therapies.

Seagrass blue carbon stocks and sequestration rates in the Colombian Caribbean.

Seagrass ecosystems rank amongst the most efficient natural carbon sinks on earth, sequestering CO2 through photosynthesis and storing organic carbon (Corg) underneath their soils for millennia and thereby, mitigating climate change. However, estimates of Corg stocks and accumulation rates in seagrass meadows (blue carbon) are restricted to few regions, and further information on spatial variability is required to derive robust global estimates. Here we studied soil Corg stocks and accumulation rates in seagrass meadows across the Colombian Caribbean. We estimated that Thalassia testudinum meadows store 241 ± 118 Mg Corg ha-1 (mean ± SD) in the top 1 m-thick soils, accumulated at rates of 122 ± 62 and 15 ± 7 g Corg m-2 year-1 over the last ~ 70 years and up to 2000 years, respectively. The tropical climate of the Caribbean Sea and associated sediment run-off, together with the relatively high primary production of T. testudinum, influencing biotic and abiotic drivers of Corg storage linked to seagrass and soil respiration rates, explains their relatively high Corg stocks and accumulation rates when compared to other meadows globally. Differences in soil Corg storage among Colombian Caribbean regions are largely linked to differences in the relative contribution of Corg sources to the soil Corg pool (seagrass, algae Halimeda tuna, mangrove and seston) and the content of soil particles < 0.016 mm binding Corg and enhancing its preservation. Despite the moderate areal extent of T. testudinum in the Colombian Caribbean (661 km2), it sequesters around 0.3 Tg CO2 year-1, which is equivalent to ~ 0.4% of CO2 emissions from fossil fuels in Colombia. This study adds data from a new region to a growing dataset on seagrass blue carbon and further explores differences in meadow Corg storage based on biotic and abiotic environmental factors, while providing the basis for the implementation of seagrass blue carbon strategies in Colombia.

Current and future carbon stocks in coastal wetlands within the Great Barrier Reef catchments.

Australia's Great Barrier Reef (GBR) catchments include some of the world's most intact coastal wetlands comprising diverse mangrove, seagrass and tidal marsh ecosystems. Although these ecosystems are highly efficient at storing carbon in marine sediments, their soil organic carbon (SOC) stocks and the potential changes resulting from climate impacts, including sea level rise are not well understood. For the first time, we estimated SOC stocks and their drivers within the range of coastal wetlands of GBR catchments using boosted regression trees (i.e. a machine learning approach and ensemble method for modelling the relationship between response and explanatory variables) and identified the potential changes in future stocks due to sea level rise. We found levels of SOC stocks of mangrove and seagrass meadows have different drivers, with climatic variables such as temperature, rainfall and solar radiation, showing significant contributions in accounting for variation in SOC stocks in mangroves. In contrast, soil type accounted for most of the variability in seagrass meadows. Total SOC stock in the GBR catchments, including mangroves, seagrass meadows and tidal marshes, is approximately 137 Tg C, which represents 9%-13% of Australia's total SOC stock while encompassing only 4%-6% of the total extent of Australian coastal wetlands. In a global context, this could represent 0.5%-1.4% of global SOC stock. Our study suggests that landward migration due to projected sea level rise has the potential to enhance carbon accumulation with total carbon gains between 0.16 and 0.46 Tg C and provides an opportunity for future restoration to enhance blue carbon.

Seagrass losses since mid-20th century fuelled CO2 emissions from soil carbon stocks.

Seagrass meadows store globally significant organic carbon (Corg ) stocks which, if disturbed, can lead to CO2 emissions, contributing to climate change. Eutrophication and thermal stress continue to be a major cause of seagrass decline worldwide, but the associated CO2 emissions remain poorly understood. This study presents comprehensive estimates of seagrass soil Corg erosion following eutrophication-driven seagrass loss in Cockburn Sound (23 km2 between 1960s and 1990s) and identifies the main drivers. We estimate that shallow seagrass meadows (<5 m depth) had significantly higher Corg stocks in 50 cm thick soils (4.5 ± 0.7 kg Corg /m2 ) than previously vegetated counterparts (0.5 ± 0.1 kg Corg /m2 ). In deeper areas (>5 m), however, soil Corg stocks in seagrass and bare but previously vegetated areas were not significantly different (2.6 ± 0.3 and 3.0 ± 0.6 kg Corg /m2 , respectively). The soil Corg sequestration capacity prevailed in shallow and deep vegetated areas (55 ± 11 and 21 ± 7 g Corg  m-2  year-1 , respectively), but was lost in bare areas. We identified that seagrass canopy loss alone does not necessarily drive changes in soil Corg but, when combined with high hydrodynamic energy, significant erosion occurred. Our estimates point at ~0.20 m/s as the critical shear velocity threshold causing soil Corg erosion. We estimate, from field studies and satellite imagery, that soil Corg erosion (within the top 50 cm) following seagrass loss likely resulted in cumulative emissions of 0.06-0.14 Tg CO2-eq over the last 40 years in Cockburn Sound. We estimated that indirect impacts (i.e. eutrophication, thermal stress and light stress) causing the loss of ~161,150 ha of seagrasses in Australia, likely resulted in the release of 11-21 Tg CO2 -eq since the 1950s, increasing cumulative CO2 emissions from land-use change in Australia by 1.1%-2.3% per annum. The patterns described serve as a baseline to estimate potential CO2 emissions following disturbance of seagrass meadows.

Discovery of [11C]MK-6884: A Positron Emission Tomography (PET) Imaging Agent for the Study of M4Muscarinic Receptor Positive Allosteric Modulators (PAMs) in Neurodegenerative Diseases.

The measurement of receptor occupancy (RO) using positron emission tomography (PET) has been instrumental in guiding discovery and development of CNS directed therapeutics. We and others have investigated muscarinic acetylcholine receptor 4 (M4) positive allosteric modulators (PAMs) for the treatment of symptoms associated with neuropsychiatric disorders. In this article, we describe the synthesis, in vitro, and in vivo characterization of a series of central pyridine-related M4 PAMs that can be conveniently radiolabeled with carbon-11 as PET tracers for the in vivo imaging of an allosteric binding site of the M4 receptor. We first demonstrated its feasibility by mapping the receptor distribution in mouse brain and confirming that a lead molecule 1 binds selectively to the receptor only in the presence of the orthosteric agonist carbachol. Through a competitive binding affinity assay and a number of physiochemical properties filters, several related compounds were identified as candidates for in vivo evaluation. These candidates were then radiolabeled with 11C and studied in vivo in rhesus monkeys. This research eventually led to the discovery of the clinical radiotracer candidate [11C]MK-6884.

Test-retest characteristic of [18F]MK-6240 quantitative outcomes in cognitively normal adults and subjects with Alzheimer's disease.

[18F]MK-6240 is a selective, high-affinity PET radiotracer for imaging neurofibrillary tangles (NFT) in Alzheimer's disease (AD). Herein, we report test-retest (T-RT) reproducibility of [18F]MK-6240 in AD and healthy volunteers (HV). Twelve subjects with AD and three cognitively normal HV were enrolled in the study and dynamically scanned for 150 min with [18F]MK-6240 under a T-RT protocol. Two radioactivity doses were investigated: 165 ± 3 MBq (n = 6) and 300 ± 40 MBq (n = 9). Serial arterial blood samples were taken for each scan to obtain metabolite-corrected input functions. Following intravenous administration of [18F]MK-6240, the tracer rapidly partitioned into the brain and its heterogenous distribution pattern was consistent with known NFT pathology in AD. In contrast, uptake in HV was low and uniform across the brain parenchyma. Across all subjects, average T-RT variabilities in NFT-rich regions were ∼21%, ∼14% and ∼6% for various quantitative metrics: total distribution volume (VT), binding potential (BPND), and standardized uptake ratio (SUVR90-120), respectively. No significant differences in SUVR T-RT variability were observed between the high and low injected radioactivity groups (5.6% and 6.1%, respectively). This work suggests [18F]MK-6240 has adequate SUVR T-RT characteristics supporting the use of this outcome in future studies.

Australian vegetated coastal ecosystems as global hotspots for climate change mitigation.

Policies aiming to preserve vegetated coastal ecosystems (VCE; tidal marshes, mangroves and seagrasses) to mitigate greenhouse gas emissions require national assessments of blue carbon resources. Here, we present organic carbon (C) storage in VCE across Australian climate regions and estimate potential annual CO2 emission benefits of VCE conservation and restoration. Australia contributes 5-11% of the C stored in VCE globally (70-185 Tg C in aboveground biomass, and 1,055-1,540 Tg C in the upper 1 m of soils). Potential CO2 emissions from current VCE losses are estimated at 2.1-3.1 Tg CO2-e yr-1, increasing annual CO2 emissions from land use change in Australia by 12-21%. This assessment, the most comprehensive for any nation to-date, demonstrates the potential of conservation and restoration of VCE to underpin national policy development for reducing greenhouse gas emissions.

Brain Imaging of Alzheimer Dementia Patients and Elderly Controls with 18F-MK-6240, a PET Tracer Targeting Neurofibrillary Tangles.

18F-MK-6240 (18F-labeled 6-(fluoro)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine) is a highly selective, subnanomolar-affinity PET tracer for imaging neurofibrillary tangles (NFTs). Plasma kinetics, brain uptake, and preliminary quantitative analysis of 18F-MK-6240 in healthy elderly (HE) subjects, subjects with clinically probable Alzheimer disease (AD), and subjects with amnestic mild cognitive impairment were characterized in a study that is, to our knowledge, the first to be performed on humans. Methods: Dynamic PET scans of up to 150 min were performed on 4 cognitively normal HE subjects, 4 AD subjects, and 2 amnestic mild cognitive impairment subjects after a bolus injection of 152-169 MBq of 18F-MK-6240 to evaluate tracer kinetics and distribution in brain. Regional SUV ratio (SUVR) and distribution volume ratio were determined using the cerebellar cortex as a reference region. Total distribution volume was assessed by compartmental modeling using radiometabolite-corrected input function in a subgroup of 6 subjects. Results:18F-MK-6240 had rapid brain uptake with a peak SUV of 3-5, followed by a uniformly quick washout from all brain regions in HE subjects; slower clearance was observed in regions commonly associated with NFT deposition in AD subjects. In AD subjects, SUVR between 60 and 90 min after injection was high (approximately 2-4) in regions associated with NFT deposition, whereas in HE subjects, SUVR was approximately 1 across all brain regions, suggesting high tracer selectivity for binding NFTs in vivo. 18F-MK-6240 total distribution volume was approximately 2- to 3-fold higher in neocortical and medial temporal brain regions of AD subjects than in HE subjects and stabilized by 60 min in both groups. Distribution volume ratio estimated by the Logan reference tissue model or compartmental modeling correlated well (R2 > 0.9) to SUVR from 60 to 90 min for AD subjects. Conclusion:18F-MK-6240 exhibited favorable kinetics and high binding levels to brain regions with a plausible pattern for NFT deposition in AD subjects. In comparison, negligible tracer binding was observed in HE subjects. This pilot study suggests that simplified ratio methods such as SUVR can be used to quantify NFT binding. These results support further clinical development of 18F-MK-6240 for potential application in longitudinal studies.

Quantification of human brain PDE4 occupancy by GSK356278: A [11C](R)-rolipram PET study.

We characterized the relationship between the plasma concentration of the phospodiesterase (PDE)-4 inhibitor GSK356278 and occupancy of the PDE4 enzyme in the brain of healthy volunteers, using the positron emission tomography (PET) tracer [11C](R)-rolipram. To this end, PET scans were acquired in eight male volunteers before and at 3 and 8 h after a single 14 mg oral dose of GSK356278. A metabolite-corrected arterial input function was used in conjunction with the dynamic PET emission data to estimate volumes of distribution (VT) from a two-tissue compartment model. The administration of GSK356278 reduced [11C](R)-rolipram whole brain VT by 17% at 3 h post-dose (p = 0.01) and by 4% at 8 h post-dose. The mean plasma Cmax was 42.3 ng/ml, leading to a PDE4 occupancy of 48% at Tmax. The in vivo affinity of GSK356278 was estimated as EC50 = 46 ± 3.6 ng/ml. We present the first report of a direct estimation of PDE4 blockade in the living human brain. In vivo affinity of GSK356278 for the PDE4, estimated in this early phase study, was combined with GSK356278 safety and tolerability data to decide on a therapeutic dose for future clinical development.

Radiosynthesis and evaluation of 1-substituted 3-(2,3-dihydro-1H-inden-2-yl)-6-(1-ethylpropyl)-(3R,6R)-2,5-piperazinedione derivatives as PET tracers for imaging the central oxytocinergic system.

Oxytocin is known to be implicated in a variety of functions, such as learning, stress, anxiety, feeding, and pain perception. Oxytocin is also important for social memory and attachment, human bonding, sexual and maternal behaviour, and aggression. Human disorders characterized by aberrant social interactions, such as autism and schizophrenia, may also involve abnormal oxytocin levels. GSK712043, GSK711320, and GSK664004, three antagonists exhibiting subnanomolar affinity for the human oxytocin receptor (hOTR) and high selectivity over vasopressin receptors were successfully labelled with carbon-11 with suitable yields (0.5-1GBq @EOS), high molar activity (275-700 GBq/µmol), and radiochemical purities. The in vivo regional uptake of these radiotracers was determined in porcine brain. [11 C]GSK711320 baseline scan showed no significant brain uptake, and limited initial uptake was observed following administration of [11 C]GSK712043 or [11 C]GSK664004. The [11 C]GSK712043 and [11 C]GSK664004 kinetics were slow and peaked at around 2%ID/L at 90 minutes post-injection. For both tracers, the distribution of activity was homogeneous throughout the brain. All the tracers showed high uptake in the pituitary gland, especially [11 C]GSK711320; however, its uptake could not be blocked by pretreatment with the known OTR antagonist, L368,899. In vivo evaluation of these candidates demonstrated that they are not suitable as central OTR PET imaging agents.

Efficacy of a fixed combination of 0.09 % xanthan gum/0.1 % chondroitin sulfate preservative free vs polyethylene glycol/propylene glycol in subjects with dry eye disease: a multicenter randomized controlled trial.

BACKGROUND: Dry eye disease (DED) is multifactorial, affecting 5-34 % of the global adult population and reducing quality of life. The artificial tears or lubricants are the therapy most used for the treatment of DED, due to their low side effect profile, which attempt to modify the properties of the tear film. The aim of the present study was to evaluate the clinical efficacy of a fixed combination of xanthan gum and chondroitin sulfate preservative free on the ocular surface of patients with dry eye disease during 60 days of intervention. METHODS: A phase III, double-blind, masked, controlled, multicenter, clinical trial of 148 subjects, randomized to either a fixed combination of xanthan gum 0.09 % and chondroitin sulfate 0.1 % (XG/CS) ophthalmic solution (n = 76) or a fixed combination of polyethylene glycol 400 0.4 % and propylene glycol 0.3 % (PEG/PG) (n = 72). Subjects self-dosed four times daily during 60 days. Follow-up was set on days 2, 7, 15, 30 and 60. Assessments of anterior/posterior segment ocular signs were performed. The outcome measures included Schirmer test, tear film break-up time and OSDI score. Security variables included intraocular pressure, lisamine green and fluorescein ocular surface stains. RESULTS: The primary efficacy endpoints were similar between groups at baseline. After intervention time Schirmer test increased in both groups compared to baseline, XG/CS (6.4 ± 2.2 vs 11.0 ± 6.6; p = 0.002) and PEG/PG (6.5 ± 2.5 vs 10.5 ± 5.6; p = 0.019) respectively. Similar results were reported in the tear film break-up time in XG/CS (5.5 ± 2.1 vs 7.4 ± 2.9; p = 0.027) and PEG/PG (5.2 ± 2.0 vs 7.4 ± 2.7; p = 0.046) respectively. The OSDI score decreased to normal values in both groups, XG/CS (19.3 ± 7.4 vs 7.3 ± 5.9; p = 0.001) and PEG/PG (19.3 ± 7.5 vs 7.9 ± 8.2; p = 0.001) respectively. There was no significant difference between treatments for any parameter. Moreover, both groups decreased the presence of burning sensation, tearing, foreign body sensation, conjunctival hyperemia and photophobia. The adverse events were not related to the interventions. CONCLUSIONS: Xanthan gum/chondroitin sulfate preservative free showed similar clinical efficacy, evaluated with OSDI score, TBUT and Schirmer test compared to polyethylene glycol/propylene glycol in the treatment of dry eye disease. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01657253 . Date of registration May 19, 2014.

Preclinical Characterization of 18F-MK-6240, a Promising PET Tracer for In Vivo Quantification of Human Neurofibrillary Tangles.

A PET tracer is desired to help guide the discovery and development of disease-modifying therapeutics for neurodegenerative diseases characterized by neurofibrillary tangles (NFTs), the predominant tau pathology in Alzheimer disease (AD). We describe the preclinical characterization of the NFT PET tracer 18F-MK-6240. METHODS: In vitro binding studies were conducted with 3H-MK-6240 in tissue slices and homogenates from cognitively normal and AD human brain donors to evaluate tracer affinity and selectivity for NFTs. Immunohistochemistry for phosphorylated tau was performed on human brain slices for comparison with 3H-MK-6240 binding patterns on adjacent brain slices. PET studies were performed with 18F-MK-6240 in monkeys to evaluate tracer kinetics and distribution in the brain. 18F-MK-6240 monkey PET studies were conducted after dosing with unlabeled MK-6240 to evaluate tracer binding selectivity in vivo. RESULTS: The 3H-MK-6240 binding pattern was consistent with the distribution of phosphorylated tau in human AD brain slices. 3H-MK-6240 bound with high affinity to human AD brain cortex homogenates containing abundant NFTs but bound poorly to amyloid plaque-rich, NFT-poor AD brain homogenates. 3H-MK-6240 showed no displaceable binding in the subcortical regions of human AD brain slices and in the hippocampus/entorhinal cortex of non-AD human brain homogenates. In monkey PET studies, 18F-MK-6240 displayed rapid and homogeneous distribution in the brain. The 18F-MK-6240 volume of distribution stabilized rapidly, indicating favorable tracer kinetics. No displaceable binding was observed in self-block studies in rhesus monkeys, which do not natively express NFTs. Moderate defluorination was observed as skull uptake. CONCLUSION: 18F-MK-6240 is a promising PET tracer for the in vivo quantification of NFTs in AD patients.

Discovery of 6-(Fluoro-(18)F)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine ([(18)F]-MK-6240): A Positron Emission Tomography (PET) Imaging Agent for Quantification of Neurofibrillary Tangles (NFTs).

Neurofibrillary tangles (NFTs) made up of aggregated tau protein have been identified as the pathologic hallmark of several neurodegenerative diseases including Alzheimer's disease. In vivo detection of NFTs using PET imaging represents a unique opportunity to develop a pharmacodynamic tool to accelerate the discovery of new disease modifying therapeutics targeting tau pathology. Herein, we present the discovery of 6-(fluoro-(18)F)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine, 6 ([(18)F]-MK-6240), as a novel PET tracer for detecting NFTs. 6 exhibits high specificity and selectivity for binding to NFTs, with suitable physicochemical properties and in vivo pharmacokinetics.

Preclinical Characterization of the Phosphodiesterase 10A PET Tracer [(11)C]MK-8193.

PURPOSE: A positron emission tomography (PET) tracer for the enzyme phosphodiesterase 10A (PDE10A) is desirable to guide the discovery and development of PDE10A inhibitors as potential therapeutics. The preclinical characterization of the PDE10A PET tracer [(11)C]MK-8193 is described. PROCEDURES: In vitro binding studies with [(3)H]MK-8193 were conducted in rat, monkey, and human brain tissue. PET studies with [(11)C]MK-8193 were conducted in rats and rhesus monkeys at baseline and following administration of a PDE10A inhibitor. RESULTS: [(3)H]MK-8193 is a high-affinity, selective PDE10A radioligand in rat, monkey, and human brain tissue. In vivo, [(11)C]MK-8193 displays rapid kinetics, low test-retest variability, and a large specific signal that is displaced by a structurally diverse PDE10A inhibitor, enabling the determination of pharmacokinetic/enzyme occupancy relationships. CONCLUSIONS: [(11)C]MK-8193 is a useful PET tracer for the preclinical characterization of PDE10A therapeutic candidates in rat and monkey. Further evaluation of [(11)C]MK-8193 in humans is warranted.

A putative biomarker signature for clinically effective AKT inhibition: correlation of in vitro, in vivo and clinical data identifies the importance of modulation of the mTORC1 pathway.

Our identification of dysregulation of the AKT pathway in ovarian cancer as a platinum resistance specific event led to a comprehensive analysis of in vitro, in vivo and clinical behaviour of the AKT inhibitor GSK2141795. Proteomic biomarker signatures correlating with effects of GSK2141795 were developed using in vitro and in vivo models, well characterised for related molecular, phenotypic and imaging endpoints. Signatures were validated in temporally paired biopsies from patients treated with GSK2141795 in a clinical study. GSK2141795 caused growth-arrest as single agent in vitro, enhanced cisplatin-induced apoptosis in vitro and reduced tumour volume in combination with platinum in vivo. GSK2141795 treatment in vitro and in vivo resulted in ~50-90% decrease in phospho-PRAS40 and 20-80% decrease in fluoro-deoxyglucose (FDG) uptake. Proteomic analysis of GSK2141795 in vitro and in vivo identified a signature of pathway inhibition including changes in AKT and p38 phosphorylation and total Bim, IGF1R, AR and YB1 levels. In patient biopsies, prior to treatment with GSK2141795 in a phase 1 clinical trial, this signature was predictive of post-treatment changes in the response marker CA125. Development of this signature represents an opportunity to demonstrate the clinical importance of AKT inhibition for re-sensitisation of platinum resistant ovarian cancer to platinum.

Dose-Finding Quantitative 18F-FDG PET Imaging Study with the Oral Pan-AKT Inhibitor GSK2141795 in Patients with Gynecologic Malignancies.

UNLABELLED: AKT (a serine/threonine-specific protein kinase) regulates many cellular processes contributing to cytotoxic drug resistance. This study's primary objective examined the relationship between GSK2141795, an oral, pan-AKT inhibitor, and (18)F-FDG PET markers of glucose metabolism in tumor tissue to determine whether (18)F-FDG PET could be used to guide personalized dosing of GSK2141795. Biomarker analysis of biopsies was also undertaken. METHODS: Twelve patients were enrolled in 3 cohorts; all underwent dynamic (18)F-FDG PET scans and serial pharmacokinetic sampling at baseline, week 2, and week 4 with tumor biopsies before treatment and at week 4. Response was evaluated by RECIST v1.1 and Gynecologic Cancer Intergroup criteria. Biopsy samples were analyzed for mutations and protein expression. RESULTS: GSK2141795 did not significantly influence blood glucose levels. No dose-response relationship was observed between GSK2141795 pharmacokinetics and (18)F-FDG PET pharmacodynamic measures; however, an exposure-response relationship was seen between maximum drug concentrations and maximal decrease in (18)F-FDG uptake in the best-responding tumor. This relationship also held for pharmacokinetic parameters of exposure and 1,5-anhydroglucitol (a systemic measure of glucose metabolism). Phospho-AKT upregulation at week 4 in biopsies confirmed AKT inhibition by GSK2141795. Single-agent activity was observed with a clinical benefit rate of 27% (3/11) and 30% (3/10) CA125 response in the study's platinum-resistant ovarian patients. AKT pathway activation by PIK3CA/PIK3R1 mutation did not correlate with clinical activity, whereas RAS/RAF pathway mutations did segregate with resistance to AKT inhibition. CONCLUSION: GSK2141795 demonstrated an exposure-response relationship with decreased (18)F-FDG uptake and is active and tolerable. This study's design integrating (18)F-FDG PET, pharmacokinetics, and biomarker analyses demonstrates the potential for clinical development for personalized treatment.