Cyanide Trapping of Iminium Ion Reactive Metabolites: Implications for Clinical Hepatotoxicity.

Reactive metabolite formation is a major mechanism of hepatotoxicity. Although reactive electrophiles can be soft or hard in nature, screening strategies have generally focused on the use of glutathione trapping assays to screen for soft electrophiles, with many data sets available to support their use. The use of a similar assay for hard electrophiles using cyanide as the trapping agent is far less common, and there is a lack of studies with sufficient supporting data. Using a set of 260 compounds with a defined hepatotoxicity status by the FDA, a comprehensive literature search yielded cyanide trapping data on an unbalanced set of 20 compounds that were all clinically hepatotoxic. Thus, a further set of 19 compounds was selected to generate cyanide trapping data, resulting in a more balanced data set of 39 compounds. Analysis of the data demonstrated that the cyanide trapping assay had high specificity (92%) and a positive predictive value (83%) such that hepatotoxic compounds would be confidently flagged. Structural analysis of the adducts formed revealed artifactual methylated cyanide adducts to also occur, highlighting the importance of full structural identification to confirm the nature of the adduct formed. The assay was demonstrated to add the most value for compounds containing typical structural alerts for hard electrophile formation: half of the severe hepatotoxins with these structural alerts formed cyanide adducts, while none of the severe hepatotoxins with no relevant structural alerts formed adducts. The assay conditions used included cytosolic enzymes (e.g., aldehyde oxidase) and an optimized cyanide concentration to minimize the inhibition of cytochrome P450 enzymes by cyanide. Based on the demonstrated added value of this assay, it is to be initiated for use at GSK as part of the integrated hepatotoxicity strategy, with its performance being reviewed periodically as more data is generated.

Preclinical evaluation of [18F]FB-A20FMDV2 as a selective marker for measuring αVß6 integrin occupancy using positron emission tomography in rodent lung.

PURPOSE: Integrin αvß6 belongs to the RGD subset of the integrin family, and its expression levels are a prognostic and theranostic factor in some types of cancer and pulmonary fibrosis. This paper describes the GMP radiolabelling of the synthetic 20 amino acid peptide A20FMDV2 (NAVPNLRGDLQVLAQKVART), derived from the foot-and-mouth disease virus, and characterises the use of [18F]FB-A20FMDV2 as a high affinity, specific and selective PET radioligand for the quantitation and visualisation of αvß6 in rodent lung to support human translational studies. METHODS: The synthesis of [18F]FB-A20FMDV2 was performed using a fully automated and GMP-compliant process. Sprague-Dawley rats were used to perform homologous (unlabelled FB-A20FMDV2) and heterologous (anti-αvß6 antibody 8G6) blocking studies. In order to generate a dosimetry estimate, tissue residence times were generated, and associated tissue exposure and effective dose were calculated using the Organ Level Internal Dose Assessment/Exponential Modelling (OLINDA/EXM) software. RESULTS: [18F]FB-A20FMDV2 synthesis was accomplished in 180 min providing ~800 MBq of [18F]FB-A20FMDV2 with a molar activity of up to 150 GBq/µmol and high radiochemical purity (> 97%). Following i.v. administration to rats, [18F]FB-A20FMDV2 was rapidly metabolised with intact radiotracer representing 5% of the total radioactivity present in rat plasma at 30 min. For the homologous and heterologous block in rats, lung-to-heart SUV ratios at 30-60 min post-administration of [18F]FB-A20FMDV2 were reduced by 38.9 ± 6.9% and 56 ± 19.2% for homologous and heterologous block, respectively. Rodent biodistribution and dosimetry calculations using OLINDA/EXM provided a whole body effective dose in humans 33.5 µSv/MBq. CONCLUSION: [18F]FB-A20FMDV2 represents a specific and selective PET ligand to measure drug-associated αvß6 integrin occupancy in lung. The effective dose, extrapolated from rodent data, is in line with typical values for compounds labelled with fluorine-18 and combined with the novel fully automated and GMP-compliant synthesis and allows for clinical use in translational studies.

Translation of Inhaled Drug Optimization Strategies into Clinical Pharmacokinetics and Pharmacodynamics Using GSK2292767A, a Novel Inhaled Phosphoinositide 3-Kinase δ Inhibitor.

This study describes the pharmacokinetic (PK) and pharmaco-dynamic (PD) profile of N-(5-(4-(5-(((2R,6S)-2,6-dimethylmorpholino)methyl)oxazol-2-yl)-1H-indazol-6-yl)-2-methoxypyridin-3-yl)methanesulfonamide (GSK2292767A), a novel low-solubility inhaled phosphoinositide 3-kinase delta (PI3Kδ) inhibitor developed as an alternative to 2-(6-(1H-indol-4-yl)-1H-indazol-4-yl)-5-((4-isopropylpiperazin-1-yl)methyl)oxazole (nemiralisib), which is a highly soluble inhaled inhibitor of PI3Kδ with a lung profile consistent with once-daily dosing. GSK2292767A has a similar in vitro cellular profile to nemiralisib and reduces eosinophilia in a murine PD model by 63% (n = 5, P < 0.05). To explore whether a low-soluble compound results in effective PI3Kδ inhibition in humans, a first time in human study was conducted with GSK2292767A in healthy volunteers who smoke. GSK2292767A was generally well tolerated, with headache being the most common reported adverse event. PD changes in induced sputum were measured in combination with drug concentrations in plasma from single (0.05-2 mg, n = 37), and 14-day repeat (2 mg, n = 12) doses of GSK2292767A. Trough bronchoalveolar lavage (BAL) for PK was taken after 14 days of repeat dosing. GSK2292767A displayed a linear increase in plasma exposure with dose, with marginal accumulation after 14 days. Induced sputum showed a 27% (90% confidence interval 15%, 37%) reduction in phosphatidylinositol-trisphosphate (the product of phosphoinositide 3-kinase activation) 3 hours after a single dose. Reduction was not maintained 24 hours after single or repeat dosing. BAL analysis confirmed the presence of GSK2292767A in lung at 24 hours, consistent with the preclinical lung retention profile. Despite good lung retention, target engagement was only present at 3 hours. This exposure-response disconnect is an important observation for future inhaled drug design strategies considering low solubility to drive lung retention.

Design, Synthesis, and Evaluation of Lung-Retentive Prodrugs for Extending the Lung Tissue Retention of Inhaled Drugs.

A major limitation of pulmonary delivery is that drugs can exhibit suboptimal pharmacokinetic profiles resulting from rapid elimination from the pulmonary tissue. This can lead to systemic side effects and a short duration of action. A series of dibasic dipeptides attached to the poorly lung-retentive muscarinic M3 receptor antagonist piperidin-4-yl 2-hydroxy-2,2-diphenylacetate (1) through a pH-sensitive-linking group have been evaluated. Extensive optimization resulted in 1-(((R)-2-((S)-2,6-diaminohexanamido)-3,3-dimethylbutanoyl)oxy)ethyl 4-(2-hydroxy-2,2-diphenylacetoxy)piperidine-1-carboxylate (23), which combined very good in vitro stability and very high rat lung binding. Compound 23 progressed to pharmacokinetic studies in rats, where, at 24 h post dosing in the rat lung, the total lung concentration of 23 was 31.2 µM. In addition, high levels of liberated drug 1 were still detected locally, demonstrating the benefit of this novel prodrug approach for increasing the apparent pharmacokinetic half-life of drugs in the lungs following pulmonary dosing.

A way to decylamine-stabilized gold nanoparticles of tailored sizes tuning their growth in solution.

Acetone solvated Au nanoparticles (Au NPs) were prepared by Metal Vapour Synthesis (MVS) co-condensing Au and acetone vapours. Nanoparticles growth was quenched at different times by using decylamine (DA) as stabilizer and DA-stabilized Au NPs were characterized by UV-Vis, NMR DOSY and HRTEM techniques. The dependence of metal clustering processes on gold concentration was investigated.

Translational pharmacology of an inhaled small molecule αvß6 integrin inhibitor for idiopathic pulmonary fibrosis.

The αvß6 integrin plays a key role in the activation of transforming growth factor-ß (TGFß), a pro-fibrotic mediator that is pivotal to the development of idiopathic pulmonary fibrosis (IPF). We identified a selective small molecule αvß6 RGD-mimetic, GSK3008348, and profiled it in a range of disease relevant pre-clinical systems. To understand the relationship between target engagement and inhibition of fibrosis, we measured pharmacodynamic and disease-related end points. Here, we report, GSK3008348 binds to αvß6 with high affinity in human IPF lung and reduces downstream pro-fibrotic TGFß signaling to normal levels. In human lung epithelial cells, GSK3008348 induces rapid internalization and lysosomal degradation of the αvß6 integrin. In the murine bleomycin-induced lung fibrosis model, GSK3008348 engages αvß6, induces prolonged inhibition of TGFß signaling and reduces lung collagen deposition and serum C3M, a marker of IPF disease progression. These studies highlight the potential of inhaled GSK3008348 as an anti-fibrotic therapy.

Discovery of an Orally Bioavailable Pan αv Integrin Inhibitor for Idiopathic Pulmonary Fibrosis.

The heterodimeric transmembrane αv integrin receptors have recently emerged as potential targets for the treatment of idiopathic pulmonary fibrosis. Herein, we describe how subtle modifications of the central aromatic ring of a series of phenylbutyrate-based antagonists of the vitronectin receptors αvß3 and αvß5 significantly change the biological activities against αvß6 and αvß8. This resulted in the discovery of a pan αv antagonist (compound 39, 4-40 nM for the integrin receptors named above) possessing excellent oral pharmacokinetic properties in rats (with a clearance of 7.6 mL/(min kg) and a bioavailability of 97%).

Profile of a Highly Selective Quaternized Pyrrolidine Betaine αvß6 Integrin Inhibitor-(3S)-3-(3-(3,5-Dimethyl-1H-pyrazol-1-yl)phenyl)-4-((1S and 1R,3R)-1-methyl-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-ium-1-yl)butanoate Synthesized by Stereoselective Methylation.

A quaternary ammonium betaine 7 is described which shows exceptional potency and selectivity (1.4 to >3 logs) for the αvß6 integrin receptor over the other αv integrins as determined in cell adhesion assays. 7 is prepared by remarkably stereoselective methylation, the origins of which are discussed. The chemical, biological, physicochemical, and pharmacokinetic properties of 7 and its docking into αvß6 are described along with related analogues.

Size-controlled synthesis and NMR characterization of mesitylene-vinylsiloxanes stabilized Pt nanoparticles in solution.

Pt nanoclusters have been generated by reaction of Pt vapour and mesitylene vapour and the role of the mesitylene/platinum ratio and the Pt particle size has been evaluated, quenching the resulting mesitylene solvated Pt atoms with 1,3-divinyltetramethyldisiloxane (DVS) as additional ligand. The Pt particle sizes have been estimated on the basis of DOSY (Diffusion-Ordered SpectroscopY) analysis and information on their structure features have been obtained by combined use of 2D NMR techniques.

Discovery of ( S)-3-(3-(3,5-Dimethyl-1 H-pyrazol-1-yl)phenyl)-4-(( R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic Acid, a Nonpeptidic αvß6 Integrin Inhibitor for the Inhaled Treatment of Idiopathic Pulmonary Fibrosis.

A series of 3-aryl(pyrrolidin-1-yl)butanoic acids were synthesized using a diastereoselective route, via a rhodium catalyzed asymmetric 1,4-addition of arylboronic acids in the presence of ( R)-BINAP to a crotonate ester to provide the ( S) absolute configuration for the major product. A variety of aryl substituents including morpholine, pyrazole, triazole, imidazole, and cyclic ether were screened in cell adhesion assays for affinity against αvß1, αvß3, αvß5, αvß6, and αvß8 integrins. Numerous analogs with high affinity and selectivity for the αvß6 integrin were identified. The analog ( S)-3-(3-(3,5-dimethyl-1 H-pyrazol-1-yl)phenyl)-4-(( R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic acid hydrochloride salt was found to have very high affinity for αvß6 integrin in a radioligand binding assay (p Ki = 11), a long dissociation half-life (7 h), very high solubility in saline at pH 7 (>71 mg/mL), and pharmacokinetic properties commensurate with inhaled dosing by nebulization. It was selected for further clinical investigation as a potential therapeutic agent for the treatment of idiopathic pulmonary fibrosis.

Evolution of a Novel, Orally Bioavailable Series of PI3Kδ Inhibitors from an Inhaled Lead for the Treatment of Respiratory Disease.

A four-step process of high-quality modeling of existing data, deconstruction, identification of replacement cores, and an innovative synthetic regrowth strategy led to the rapid discovery of a novel oral series of PI3Kδ inhibitors with promising selectivity and excellent in vivo characteristics.

Synthesis and biological evaluation of pro-drugs of GW196771, a potent glycine antagonist acting at the NMDA receptor.

GW196771 is a potent antagonist of the modulatory glycine site of the N-methyl-D-aspartate (NMDA) receptor exhibiting outstanding in vivo profile in different animal models of chronic pain. With the aim to maximize the drug delivery to the target organs a suitable "pro-drug approach" was attempted; in this regards two conjugates of GW196771 with nutrients actively transported into the brain, namely adenosine and glucose, were prepared and investigated. These compounds, were evaluated in vitro in terms of their stability in rat plasma and in vivo on rats. Although an improvement was observed in terms of brain penetration of the esters vs. the parent compound, the amount of the latter did not increase significantly, probably due to some degradation events in the brain, different from the expected ester hydrolysis, resulting in a reduced availability of GW196771.

Glucose-coated superparamagnetic iron oxide nanoparticles prepared by metal vapour synthesis are electively internalized in a pancreatic adenocarcinoma cell line expressing GLUT1 transporter.

Iron oxide nanoparticles (IONP) can have a variety of biomedical applications due to their visualization properties through Magnetic Resonance Imaging (MRI) and heating with radio frequency or alternating magnetic fields. In the oncological field, coating IONP with organic compounds to provide specific features and to achieve the ability of binding specific molecular targets appears to be very promising. To take advantage of the high avidity of tumor cells for glucose, we report the development of very small glucose-coated IONP (glc-IONP) by employing an innovative technique, Metal Vapor Synthesis (MVS). Moreover, we tested the internalization of our gl-IONP on a tumor line, BxPC3, over-expressing GLUT 1 transporter. Both glc-IONP and polyvinylpyrrolidone-IONP (PVP-IONP), as control, were prepared with MVS and were tested on BxPC3 at various concentrations. To evaluate the role of GLUT-1 transporter, we also investigated the effect of adding a polyclonal anti-GLUT1 antibody. After proper treatment, the iron value was assessed by atomic absorption spectrometer, reported in mcg/L and expressed in mg of protein. Our IONP prepared with MVS were very small and homogeneously distributed in a narrow range (1.75-3.75 nm) with an average size of 2.7 nm and were super-paramagnetic. Glc-IONP were internalized by BxPC3 cells in a larger amount than PVP-IONP. After 6h of treatment with 50 mcg/mL of IONPs, the content of Fe was 1.5 times higher in glc-IONP-treated cells compared with PVP-IONP-treated cells. After 1h pre-treatment with anti-GLUT1, a reduction of 41% cellular accumulation of glc-IONP was observed. Conversely, the uptake of PVP-IONPs was reduced only by 14% with antibody pretreatment. In conclusion, MVS allowed us to prepare small, homogeneous, super-paramagnetic glc-IONP, which are electively internalized by a tumor line over-expressing GLUT1. Our glc-IONP appear to have many requisites for in vivo use.

Optimization of Novel Indazoles as Highly Potent and Selective Inhibitors of Phosphoinositide 3-Kinase δ for the Treatment of Respiratory Disease.

Optimization of lead compound 1, through extensive use of structure-based design and a focus on PI3Kδ potency, isoform selectivity, and inhaled PK properties, led to the discovery of clinical candidates 2 (GSK2269557) and 3 (GSK2292767) for the treatment of respiratory indications via inhalation. Compounds 2 and 3 are both highly selective for PI3Kδ over the closely related isoforms and are active in a disease relevant brown Norway rat acute OVA model of Th2-driven lung inflammation.

Expression analysis of brain-derived neurotrophic factor (BDNF) mRNA isoforms after chronic and acute antidepressant treatment.

The neurotrophin brain-derived neurotrophic factor (BDNF) is considered to be a key factor for neuronal survival, differentiation and plasticity. According to a proposed hypothetical model BDNF expression might play a central role in the pathogenesis of depression. The BDNF gene is rather complex in its structure and it can express four different mRNA isoforms by alternative splicing, each producing the same protein. This might reflect fine tuning of gene regulation by different signalling networks. Since the BDNF gene has been reported to be upregulated by antidepressants, the expression of the four BDNF mRNA isoforms was measured by real-time quantitative RT-PCR in rat hippocampi after chronic and acute treatment with the antidepressant drug fluoxetine and GR205171, a selective NK-1 receptor antagonist with anxiolytic-like properties. The aim of this study was to test the hypothesis of differential regulation of the mRNA isoforms by those compounds. Our results indicate that the expression of BDNF mRNA isoforms is not affected by chronic or acute treatment with fluoxetine or GR205171.

Effect of the TRPV1 antagonist SB-705498 on the nasal parasympathetic reflex response in the ovalbumin sensitized guinea pig.

BACKGROUND AND PURPOSE: Nasal sensory nerves play an important role in symptoms associated with rhinitis triggered by environmental stimuli. Here, we propose that TRPV1 is pivotal in nasal sensory nerve activation and assess the potential of SB-705498 as an intranasal therapy for rhinitis. EXPERIMENTAL APPROACH: The inhibitory effect of SB-705498 on capsaicin-induced currents in guinea pig trigeminal ganglion cells innervating nasal mucosa was investigated using patch clamp electrophysiology. A guinea pig model of rhinitis was developed using intranasal challenge of capsaicin and hypertonic saline to elicit nasal secretory parasympathetic reflex responses, quantified using MRI. The inhibitory effect of SB-705498, duration of action and potency comparing oral versus intranasal route of administration were examined. KEY RESULTS: SB-705498 concentration-dependently inhibited capsaicin-induced currents in isolated trigeminal ganglion cells (pIC50 7.2). In vivo, capsaicin ipsilateral nasal challenge (0.03-1 mM) elicited concentration-dependent increases in contralateral intranasal fluid secretion. Ten per cent hypertonic saline initiated a similar response. Atropine inhibited responses to either challenge. SB-705498 inhibited capsaicin-induced responses by ∼50% at 10 mg·kg⁻¹ (oral), non-micronized 10 mg·mL⁻¹ or 1 mg·mL⁻¹ micronized SB-705498 (intranasal) suspension. Ten milligram per millilitre intranasal SB-705498, dosed 24 h prior to capsaicin challenge produced a 52% reduction in secretory response. SB-705498 (10 mg·mL⁻¹, intranasal) inhibited 10% hypertonic saline responses by 70%. CONCLUSIONS AND IMPLICATIONS: The paper reports the development of a guinea pig model of rhinitis. SB-705498 inhibits capsaicin-induced trigeminal currents and capsaicin-induced contralateral nasal secretions via oral and intranasal routes; efficacy was optimized using particle-reduced SB-705498. We propose that TRPV1 is pivotal in initiating symptoms of rhinitis.

Molecular clinical safety intelligence: a system for bridging clinically focused safety knowledge to early-stage drug discovery - the GSK experience.

Drug toxicity is a major cause of late-stage product attrition. During lead identification and optimization phases little information is typically available about which molecules might have safety concerns. A system was built linking chemistry, preclinical and human safety information, enabling scientists to lever safety knowledge across multiple disciplines. The system consists of a data warehouse with chemical structures and chemical and biological properties for ∼80000 compounds and tools to access and analyze clinical data, toxicology, in vitro pharmacology and drug metabolism data. Tapping into this safety knowledge enables rapid clinically focused risk assessments of drug candidates. Use of this strategy adds value to the drug discovery process at GSK via efficient triage of compounds based on their potential for toxicity.

p38alpha mitogen-activated protein kinase inhibitors: optimization of a series of biphenylamides to give a molecule suitable for clinical progression.

p38alpha MAP kinase is a key anti-inflammatory target for rheumatoid arthritis, influencing biosynthesis of pro-inflammatory cytokines TNFalpha and IL-1beta at a translational and transcriptional level. In this paper, we describe how we have optimized a series of novel p38alpha/beta inhibitors using crystal structures of our inhibitors bound to p38alpha, classical medicinal chemistry, and modeling of virtual libraries to derive a molecule suitable for progression into clinical development.