Publications by authors named "Andy D Roberts"

12 Publications

  • Page 1 of 1

Using hyperpolarised NMR and DFT to rationalise the unexpected hydrogenation of quinazoline to 3,4-dihydroquinazoline.

Chem Commun (Camb) 2018 Sep;54(73):10375-10378

Centre for Hyperpolarisation in Magnetic Resonance, University of York, Heslington, York YO10 5NY, UK.

PHIP and SABRE hyperpolarized NMR methods are used to follow the unexpected metal-catalysed hydrogenation of quinazoline (Qu) to 3,4-dihydroquinazoline as the sole product. A solution of [IrCl(IMes)(COD)] in dichloromethane reacts with H2 and Qu to form [IrCl(H)2(IMes)(Qu)2] (2). The addition of methanol then results in its conversion to [Ir(H)2(IMes)(Qu)3]Cl (3) which catalyses the hydrogenation reaction. Density functional theory calculations are used to rationalise a proposed outer sphere mechanism in which (3) converts to [IrCl(H)2(H2)(IMes)(Qu)2]Cl (4) and neutral [Ir(H)3(IMes)(Qu)2] (6), both of which are involved in the formation of 3,4-dihydroquinazoline via the stepwise transfer of H+ and H-, with H2 identified as the reductant. Successive ligand exchange in 3 results in the production of thermodynamically stable [Ir(H)2(IMes)(3,4-dihydroquinazoline)3]Cl (5).
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http://dx.doi.org/10.1039/c8cc04826fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6136267PMC
September 2018

Fragment-Based Discovery of Low-Micromolar ATAD2 Bromodomain Inhibitors.

J Med Chem 2015 Jul 9;58(14):5649-73. Epub 2015 Jul 9.

∥Drug Metabolism and Pharmacokinetics (DMPK), GlaxoSmithKline, Park Road, Ware, Hertfordshire SG12 0DP, United Kingdom.

Overexpression of ATAD2 (ATPase family, AAA domain containing 2) has been linked to disease severity and progression in a wide range of cancers, and is implicated in the regulation of several drivers of cancer growth. Little is known of the dependence of these effects upon the ATAD2 bromodomain, which has been categorized as among the least tractable of its class. The absence of any potent, selective inhibitors limits clear understanding of the therapeutic potential of the bromodomain. Here, we describe the discovery of a hit from a fragment-based targeted array. Optimization of this produced the first known micromolar inhibitors of the ATAD2 bromodomain.
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http://dx.doi.org/10.1021/acs.jmedchem.5b00772DOI Listing
July 2015

1,3-Dimethyl Benzimidazolones Are Potent, Selective Inhibitors of the BRPF1 Bromodomain.

ACS Med Chem Lett 2014 Nov 10;5(11):1190-5. Epub 2014 Sep 10.

Epinova Discovery Performance Unit and Molecular Discovery Research, GlaxoSmithKline , Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, U.K.

The BRPF (bromodomain and PHD finger-containing) protein family are important scaffolding proteins for assembly of MYST histone acetyltransferase complexes. Here, we report the discovery, binding mode, and structure-activity relationship (SAR) of the first potent, selective series of inhibitors of the BRPF1 bromodomain.
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http://dx.doi.org/10.1021/ml5002932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4233354PMC
November 2014

Metabolism and disposition of vilanterol, a long-acting β(2)-adrenoceptor agonist for inhalation use in humans.

Drug Metab Dispos 2013 Jan 4;41(1):89-100. Epub 2012 Oct 4.

Division of Drug Metabolism and Pharmacokinetics, GlaxoSmithKline R&D, Park Road, Ware, Hertfordshire, SG12 0DP, United Kingdom.

The metabolism and disposition of vilanterol, a novel long-acting β(2)-adrenoceptor agonist (LABA) for inhalation use, was investigated after oral administration in humans. Single oral administrations of up to 500 μg of vilanterol were shown to be safe and well tolerated in two clinical studies in healthy men. In a human radiolabel study, six healthy men received a single oral dose of 200 μg of [(14)C]vilanterol (74 kBq). Plasma, urine, and feces were collected up to 168 hours after the dose and were analyzed for vilanterol, metabolites, and radioactivity. At least 50% of the radioactive dose was orally absorbed. The primary route of excretion of drug-related material was via O-dealkylation to metabolites, which were mainly excreted in urine. Vilanterol represented a very small percentage (<0.5%) of the total drug-related material in plasma, indicative of extensive first-pass metabolism. Circulating metabolites resulted mainly from O-dealkylation and exhibited negligible pharmacologic activity. The therapeutic dose level for vilanterol is 25 μg by the inhalation route. At this low-dose level, the likelihood of pharmacologically inactive metabolites causing unexpected toxicity is negligible. In addition to providing an assessment of the disposition of vilanterol in human, this work highlights a number of complexities associated with determining human absorption, distribution, metabolism, and excretion (ADME) for inhaled molecules--mainly related to the low chemical doses and complications associated with the inhalation route of administration.
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http://dx.doi.org/10.1124/dmd.112.048603DOI Listing
January 2013

Sensitivity of early life stages of freshwater mussels (Unionidae) to acute and chronic toxicity of lead, cadmium, and zinc in water.

Environ Toxicol Chem 2010 Sep;29(9):2053-63

U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201, USA.

Toxicity of lead, cadmium, or zinc to early life stages of freshwater mussels (fatmucket, Lampsilis siliquoidea; Neosho mucket, L. rafinesqueana) was evaluated in 48-h exposures with mussel larvae (glochidia), in 96-h exposures with newly transformed (5-d-old) and two- or six-month-old juvenile mussels, or in 28-d exposures with two- or four-month-old mussels in reconstituted soft water. The 24-h median effect concentrations (EC50s) for fatmucket glochidia (>299 microg Pb/L, >227 microg Cd/L, 2,685 microg Zn/L) and 96-h EC50s for two- or six-month-old fatmucket (>426 microg Pb/L, 199 microg Cd/L, 1,700 microg Zn/L) were much higher than 96-h EC50s for newly transformed fatmucket (142 and 298 microg Pb/L, 16 microg Cd/L, 151 and 175 microg Zn/L) and Neosho mucket (188 microg Pb/L, 20 microg Cd/L, 145 microg Zn/L). Chronic values for fatmucket were 10 microg Pb/L, 6.0 microg Cd/L, and 63 and 68 microg Zn/L. When mussel data from the present study and the literature were included in updated databases for deriving U.S. Environmental Protection Agency water quality criteria, mussel genus mean acute values were in the lower percentiles of the sensitivity distribution of all freshwater species for Pb (the 26th percentile), Cd (the 15th to 29th percentile), or Zn (the 12th to 21st percentile). The mussel (Lampsilis) genus mean chronic value was the lowest value ever reported for Pb (the 9th percentile) but was near the middle of the sensitivity distribution for Cd (the 61st percentile) or Zn (the 44th percentile). These results indicate that mussels were relatively sensitive to the acute toxicity of these three metals and to the chronic toxicity of Pb, but were moderately sensitive to the chronic toxicity of Cd or Zn compared to other freshwater species.
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http://dx.doi.org/10.1002/etc.250DOI Listing
September 2010

Prefrontal cortex oxygenation during incremental exercise in chronic fatigue syndrome.

Clin Physiol Funct Imaging 2008 Nov 29;28(6):364-72. Epub 2008 Jul 29.

Faculty of Kinesiology & Health Studies, University of Regina, Regina, SK, Canada.

This study examined the effects of maximal incremental exercise on cerebral oxygenation in chronic fatigue syndrome (CFS) subjects. Furthermore, we tested the hypothesis that CFS subjects have a reduced oxygen delivery to the brain during exercise. Six female CFS and eight control (CON) subjects (similar in height, weight, body mass index and physical activity level) performed an incremental cycle ergometer test to exhaustion, while changes in cerebral oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), total blood volume (tHb = HbO2 + HHb) and O2 saturation [tissue oxygenation index (TOI), %)] was monitored in the left prefrontal lobe using a near-infrared spectrophotometer. Heart rate (HR) and rating of perceived exertion (RPE) were recorded at each workload throughout the test. Predicted VO2peak in CFS (1331 +/- 377 ml) subjects was significantly (P < or = 0.05) lower than the CON group (1990 +/- 332 ml), and CFS subjects achieved volitional exhaustion significantly faster (CFS: 351 +/- 224 s; CON: 715 +/- 176 s) at a lower power output (CFS: 100 +/- 39 W; CON: 163 +/- 34 W). CFS subjects also exhibited a significantly lower maximum HR (CFS: 154 +/- 13 bpm; CON: 186 +/- 11 bpm) and consistently reported a higher RPE at the same absolute workload when compared with CON subjects. Prefrontal cortex HbO2, HHb and tHb were significantly lower at maximal exercise in CFS versus CON, as was TOI during exercise and recovery. The CFS subjects exhibited significant exercise intolerance and reduced prefrontal oxygenation and tHb response when compared with CON subjects. These data suggest that the altered cerebral oxygenation and blood volume may contribute to the reduced exercise load in CFS, and supports the contention that CFS, in part, is mediated centrally.
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http://dx.doi.org/10.1111/j.1475-097X.2008.00822.xDOI Listing
November 2008

Chronic toxicity of copper and ammonia to juvenile freshwater mussels (Unionidae).

Environ Toxicol Chem 2007 Oct;26(10):2048-56

Columbia Environmental Research Center, U.S. Geological Survey, Columbia, Missouri 65201, USA.

The objectives of the present study were to develop methods for conducting chronic toxicity tests with juvenile mussels under flow-through conditions and to determine the chronic toxicity of copper and ammonia to juvenile mussels using these methods. In two feeding tests, two-month-old fatmucket (Lampsilis siliquoidea) and rainbow mussel (Villosa iris) were fed various live algae or nonviable algal mixture for 28 d. The algal mixture was the best food resulting in high survival (>or=90%) and growth. Multiple copper and ammonia toxicity tests were conducted for 28 d starting with two-month-old mussels. Six toxicity tests using the algal mixture were successfully completed with a control survival of 88 to 100%. Among copper tests with rainbow mussel, fatmucket, and oyster mussel (Epioblasma capsaeformis), chronic value ([ChV], geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) ranged from 8.5 to 9.8 microg Cu/L for survival and from 4.6 to 8.5 microg Cu/L for growth. Among ammonia tests with rainbow mussel, fatmucket, and wavy-rayed lampmussel (L. fasciola), the ChV ranged from 0.37 to 1.2 mg total ammonia N/L for survival and from 0.37 to 0.67 mg N/L for growth. These ChVs were below the U.S. Environmental Protection Agency 1996 chronic water quality criterion (WQC) for copper (15 microg/L; hardness 170 mg/L) and 1999 WQC for total ammonia (1.26 mg N/L; pH 8.2 and 20 degrees C). Results indicate that toxicity tests with two-month-old mussels can be conducted for 28 d with >80% control survival; growth was frequently a more sensitive endpoint compared to survival; and the 1996 chronic WQC for copper and the 1999 chronic WQC for total ammonia might not be adequately protective of the mussel species tested. However, a recently revised 2007 chronic WQC for copper based on the biotic ligand model may be more protective in the water tested.
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http://dx.doi.org/10.1897/06-524R.1DOI Listing
October 2007

Acute toxicity of copper, ammonia, and chlorine to glochidia and juveniles of freshwater mussels (Unionidae).

Environ Toxicol Chem 2007 Oct;26(10):2036-47

Columbia Environmental Research Center, U.S. Geological Survey, Columbia, Missouri 65201, USA.

The objective of the present study was to determine acute toxicity of copper, ammonia, or chlorine to larval (glochidia) and juvenile mussels using the recently published American Society for Testing and Materials (ASTM) Standard guide for conducting laboratory toxicity tests with freshwater mussels. Toxicity tests were conducted with glochidia (24- to 48-h exposures) and juveniles (96-h exposures) of up to 11 mussel species in reconstituted ASTM hard water using copper, ammonia, or chlorine as a toxicant. Copper and ammonia tests also were conducted with five commonly tested species, including cladocerans (Daphnia magna and Ceriodaphnia dubia; 48-h exposures), amphipod (Hyalella azteca; 48-h exposures), rainbow trout (Oncorhynchus mykiss; 96-h exposures), and fathead minnow (Pimephales promelas; 96-h exposures). Median effective concentrations (EC50s) for commonly tested species were >58 microg Cu/L (except 15 microg Cu/L for C. dubia) and >13 mg total ammonia N/L, whereas the EC50s for mussels in most cases were <45 microg Cu/L or <12 mg N/L and were often at or below the final acute values (FAVs) used to derive the U.S. Environmental Protection Agency 1996 acute water quality criterion (WQC) for copper and 1999 acute WQC for ammonia. However, the chlorine EC50s for mussels generally were >40 microg/L and above the FAV in the WQC for chlorine. The results indicate that the early life stages of mussels generally were more sensitive to copper and ammonia than other organisms and that, including mussel toxicity data in a revision to the WQC, would lower the WQC for copper or ammonia. Furthermore, including additional mussel data in 2007 WQC for copper based on biotic ligand model would further lower the WQC.
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http://dx.doi.org/10.1897/06-523R.1DOI Listing
October 2007

Intra- and interlaboratory variability in acute toxicity tests with glochidia and juveniles of freshwater mussels (Unionidae).

Environ Toxicol Chem 2007 Oct;26(10):2029-35

Columbia Environmental Research Center, U.S. Geological Survey, New Haven Road, Columbia, Missouri 65201, USA.

The present study evaluated the performance and variability in acute toxicity tests with glochidia and newly transformed juvenile mussels using the standard methods outlined in American Society for Testing and Materials (ASTM). Multiple 48-h toxicity tests with glochidia and 96-h tests with juvenile mussels were conducted within a single laboratory and among five laboratories. All tests met the test acceptability requirements (e.g., >or=90% control survival). Intralaboratory tests were conducted over two consecutive mussel-spawning seasons with mucket (Actinonaias ligamentina) or fatmucket (Lampsilis siliquoidea) using copper, ammonia, or chlorine as a toxicant. For the glochidia of both species, the variability of intralaboratory median effective concentrations (EC50s) for the three toxicants, expressed as the coefficient of variation (CV), ranged from 14 to 27% in 24-h exposures and from 13 to 36% in 48-h exposures. The intralaboratory CV of copper EC50s for juvenile fatmucket was 24% in 48-h exposures and 13% in 96-h exposures. Interlaboratory tests were conducted with fatmucket glochidia and juveniles by five laboratories using copper as a toxicant. The interlaboratory CV of copper EC50s for glochidia was 13% in 24-h exposures and 24% in 48-h exposures, and the interlaboratory CV for juveniles was 22% in 48-h exposures and 42% in 96-h exposures. The high completion success and the overall low variability in test results indicate that the test methods have acceptable precision and can be performed routinely.
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http://dx.doi.org/10.1897/06-520R.1DOI Listing
October 2007

A gender-specific discriminator in Sprague-Dawley rat urine: the deployment of a metabolic profiling strategy for biomarker discovery and identification.

Anal Biochem 2007 Mar 28;362(2):182-92. Epub 2006 Dec 28.

Safety Assessment Division, GlaxoSmithKline, Ware, UK.

The use of nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) as complementary analytical techniques for open metabolic profiling is illustrated in the context of defining urinary biochemical discriminators between male and female Sprague-Dawley rats. Subsequent to the discovery of a female-specific urinary discriminator by LC-MS, further LC, MS, and NMR methods have been applied in a coordinated effort to identify this urinary component. Thereafter, the biological relevance and context of the identified component, in this case a steroid metabolite, has been achieved. This approach will be deployed in future studies of disease, drug efficacy, and toxicity to discover and identify biologically relevant markers.
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http://dx.doi.org/10.1016/j.ab.2006.12.037DOI Listing
March 2007

A [17F]-fluoromethane PET/TMS study of effective connectivity.

Brain Res Bull 2004 Aug;64(2):103-13

Department of Psychiatry, University of Wisconsin, Madison, 6001 Research Park Blvd., Madison, WI 53719, USA.

We used transcranial magnetic stimulation (TMS) in combination with positron emission tomography (PET) to investigate the effective connectivity of four cortical regions within the same study. By employing [17F]-[CH3F] ([17F]-fluoromethane) as a radiotracer of blood-flow, we were able to obtain increased sensitivity compared to [15O]-H2O for both cortical and subcortical structures. The brain areas investigated were left primary motor cortex, right primary visual cortex, and left and right prefrontal areas. We found that each site of stimulation yielded a different pattern of activation/deactivation consistent with its anatomical connectivity. Moreover, we found that TMS of prefrontal and motor cortical areas gave rise to trans-synaptic activation of subcortical circuits.
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http://dx.doi.org/10.1016/j.brainresbull.2004.04.020DOI Listing
August 2004

Direct on-line hyphenation of capillary liquid chromatography to nuclear magnetic resonance spectroscopy: practical aspects and application to drug metabolite identification.

J Chromatogr A 2004 Mar;1028(2):259-66

DMPK Structural ID Group, GlaxoSmithKline R&D, Park Road, Ware, Herts SG12 0DP, UK.

In combining the high peak concentrations of capillary liquid chromatography (CapLC) with the high mass sensitivity of micro scale nuclear magnetic resonance (NMR) the hyphenation of CapLC to micro NMR offers a substantial gain in overall sensitivity. This paper deals with our experiences gained using a commercial CapLC-NMR system which has very recently become available. The limits of detection (SNR > 3) for a test compound of a molecular weight of M 318 were found to be approximately 100 ng (0.35 nmol) within an hour acquisition time and approximately 25 ng over night (85 pmol). Practical aspects such as the feasibility of stopped-flow experiments and sample handling issues are discussed in detail and first possible drug metabolite applications to hepatocyte incubations and direct analysis of plasma samples are presented.
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http://dx.doi.org/10.1016/j.chroma.2003.11.105DOI Listing
March 2004