Publications by authors named "Edilio Borroni"

48 Publications

The impact of demographic, clinical, genetic, and imaging variables on tau PET status.

Eur J Nucl Med Mol Imaging 2020 Nov 19. Epub 2020 Nov 19.

Clinical Memory Research Unit, Lund University, Lund, Sweden.

Purpose: A substantial proportion of amyloid-β (Aβ)+ patients with clinically diagnosed Alzheimer's disease (AD) dementia and mild cognitive impairment (MCI) are tau PET-negative, while some clinically diagnosed non-AD neurodegenerative disorder (non-AD) patients or cognitively unimpaired (CU) subjects are tau PET-positive. We investigated which demographic, clinical, genetic, and imaging variables contributed to tau PET status.

Methods: We included 2338 participants (430 Aβ+ AD dementia, 381 Aβ+ MCI, 370 non-AD, and 1157 CU) who underwent [F]flortaucipir (n = 1944) or [F]RO948 (n = 719) PET. Tau PET positivity was determined in the entorhinal cortex, temporal meta-ROI, and Braak V-VI regions using previously established cutoffs. We performed bivariate binary logistic regression models with tau PET status (positive/negative) as dependent variable and age, sex, APOEε4, Aβ status (only in CU and non-AD analyses), MMSE, global white matter hyperintensities (WMH), and AD-signature cortical thickness as predictors. Additionally, we performed multivariable binary logistic regression models to account for all other predictors in the same model.

Results: Tau PET positivity in the temporal meta-ROI was 88.6% for AD dementia, 46.5% for MCI, 9.5% for non-AD, and 6.1% for CU. Among Aβ+ participants with AD dementia and MCI, lower age, MMSE score, and AD-signature cortical thickness showed the strongest associations with tau PET positivity. In non-AD and CU participants, presence of Aβ was the strongest predictor of a positive tau PET scan.

Conclusion: We identified several demographic, clinical, and neurobiological factors that are important to explain the variance in tau PET retention observed across the AD pathological continuum, non-AD neurodegenerative disorders, and cognitively unimpaired persons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00259-020-05099-wDOI Listing
November 2020

Diagnostic Performance of RO948 F 18 Tau Positron Emission Tomography in the Differentiation of Alzheimer Disease From Other Neurodegenerative Disorders.

JAMA Neurol 2020 08;77(8):955-965

Clinical Memory Research Unit, Department of Clinical Sciences, Lund University, Malmö, Sweden.

Importance: The diagnostic performance of second-generation tau positron emission tomographic (PET) tracers is not yet known.

Objective: To examine the novel tau PET tracer RO948 F 18 ([18F]RO948) performance in discriminating Alzheimer disease (AD) from non-AD neurodegenerative disorders.

Design, Setting, And Participants: In this diagnostic study, 613 participants in the Swedish BioFINDER-2 study were consecutively enrolled in a prospective cross-sectional study from September 4, 2017, to August 28, 2019. Participants included 257 cognitively unimpaired controls, 154 patients with mild cognitive impairment, 100 patients with AD dementia, and 102 with non-AD neurodegenerative disorders. Evaluation included a comparison of tau PET tracer [18F]RO948 with magnetic resonance imaging (MRI) and cerebrospinal fluid and a head-to-head comparison between [18F]RO948 and flortaucipir F 18 ([18F]flortaucipir) in patients with semantic variant primary progressive aphasia (svPPA).

Exposures: [18F]RO948 (all patients) and [18F]flortaucipir (3 patients with svPPA) tau PET; MRI (hippocampal volume, composite temporal lobe cortical thickness, whole-brain cortical thickness) and cerebrospinal fluid measures (p-tau181 and amyloid Aβ42 and Aβ40 ratio[Aβ42/Aβ40], and Aβ42/p-tau181 ratio).

Main Outcomes And Measures: Standard uptake value ratios (SUVRs) in 4 predefined regions of interest (ROIs) reflecting Braak staging scheme for tau pathology and encompass I-II (entorhinal cortex), III-IV (inferior/middle temporal, fusiform gyrus, parahippocampal cortex, and amygdala), I-IV, and V-VI (widespread neocortical areas), area under the receiver operating characteristic curve (AUC) values, and subtraction images between [18F]RO948 and [18F]flortaucipir.

Results: Diagnostic groups among the 613 participants included cognitively unimpaired (mean [SD] age, 65.8 [12.1] years; 117 men [46%]), mild cognitive impairment (age, 70.8 [8.3] years; 82 men [53%]), AD dementia (age, 73.5 [6.7] years; 57 men [57%]), and non-AD disorders (age, 70.5 [8.6] years; 41 men [40%]). Retention of [18F]RO948 was higher in AD dementia compared with all other diagnostic groups. [18F]RO948 could distinguish patients with AD dementia from individuals without cognitive impairment and those with non-AD disorders, and the highest AUC was obtained using the I-IV ROI (AUC = 0.98; 95% CI, 0.96-0.99 for AD vs no cognitive impairment and AUC = 0.97; 95% CI, 0.95-0.99 for AD vs non-AD disorders), which outperformed MRI (highest AUC = 0.91 for AD vs no cognitive impairment using whole-brain thickness, and AUC = 0.80 for AD vs non-AD disorders using temporal lobe thickness) and cerebrospinal fluid measures (highest AUC = 0.94 for AD vs no cognitive impairment using Aβ42/p-tau181, and AUC = 0.93 for AD vs non-AD disorders using Aβ42/Aβ40). Generally, tau PET positivity using [18F]RO948 was observed only in Aβ-positive cases or in MAPT R406W mutation carriers. Retention of [18F]RO948 was not pronounced in patients with svPPA, and head-to-head comparison revealed lower temporal lobe uptake than with [18F]flortaucipir.

Conclusions And Relevance: In this study, elevated [18F]RO948 SUVRs were most often seen among Aβ-positive cases, which suggests that [18F]RO948 has high specificity for AD-type tau and highlights its potential as a diagnostic marker in the differential diagnosis of AD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1001/jamaneurol.2020.0989DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215644PMC
August 2020

A Comparative Study of in vitro Assays for Predicting the Nonspecific Binding of PET Imaging Agents in vivo.

ChemMedChem 2020 04 13;15(7):585-592. Epub 2019 Dec 13.

Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Fabrikstrasse 2, 4056, Basel, Switzerland.

Nonspecific binding (NSB) is a key parameter in optimizing PET imaging tracers. We compared the ability to predict NSB of three available methods: LIMBA, rat f , and CHI(IAM). Even though NSB is often associated with lipophilicity, we observed that logD does not correlate with any of these assays, clearly indicating that lipophilicity, while influencing NSB, is insufficient to predict it. A cross-comparison of the methods showed that all three correlate and are useful predictors of NSB. The three assays, however, rank the molecules slightly differently, illustrating the challenge of comparing molecules within a narrow chemical space. We also noted that CHI(IAM) values more effectively predict V , a measure of in vivo NSB in the human brain. CHI(IAM) measurements might be a closer model of the actual physicochemical interaction between PET tracer candidates and cell membranes, and seems to be the method of choice for the optimization of in vivo NSB.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cmdc.201900608DOI Listing
April 2020

Glycine Transporter Type I (GlyT1) Inhibitor, Bitopertin: A Journey from Lab to Patient.

Chimia (Aarau) 2018 Aug;72(7):477-484

Roche Pharmaceutical Research and Early Development (pRED) Roche Innovation Center Basel Medicinal Chemistry Department 124 Grenzacherstrasse, B 92 /6.30 CH-4070 Basel.

Glycine transporter-1 (GlyT1) inhibition has been extensively studied both in pharmaceutical companies and academic institutions primarily as a potential new approach to treat schizophrenia, a severe and chronic mental illness. More recently, preclinical results have suggested that this approach could also have therapeutic potential for CNS disorders beyond schizophrenia as well as for non-CNS indications. Over the past 17 years, Roche has been a key player in the GlyT1 field with the discovery and development of bitopertin, the most advanced GlyT1 inhibitor to date and the only one which completed Phase III clinical studies for schizophrenia. In this article, we relate the eventful journey of the discovery and development of bitopertin, from project initiation in 2001 to its evaluation today in patients suffering from beta-thalassemia, a monogenic hereditary haematological disorder.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2533/chimia.2018.477DOI Listing
August 2018

Evaluation of F-RO-948 PET for Quantitative Assessment of Tau Accumulation in the Human Brain.

J Nucl Med 2018 12 10;59(12):1877-1884. Epub 2018 Aug 10.

Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland.

The availability of tau PET radioligands enables quantitative assessment of tau density and distribution in the human brain. We evaluated the kinetics of a novel radioligand, F-RO-948 (previously referred to as F-RO6958948), and its ability to identify tau positivity in individual patients with mild Alzheimer disease (AD). Eleven subjects with amyloid-positive mild AD, 5 amyloid-negative older control subjects (OC), and 5 younger control subjects (YC) completed 1 or 2 (4 AD and 5 OC) PET scans with F-RO-948 for 90, 120, or 200 min. The kinetics of the radioligand was evaluated with standard compartmental and noncompartmental models (with plasma data in 70% of cases), tissue-reference methods, and SUV ratio. These approaches were applied to assess the ability of F-RO-948 to discriminate AD subjects from OC subjects. The plasma reference graphical analysis appeared to be the optimal method of quantification for F-RO-948, yielding strictly time-consistent values of distribution volume and distribution volume ratio at 90 min against the analyses at 120 and 200 min. The reference tissue graphical analysis and SUV ratio were cross-validated against plasma reference graphical analysis. Test-retest evaluation showed excellent reproducibility. A proposed novel index of tau load, the regional tau-positive fraction, showed high values in the medial and lateral temporal and parietal regions in AD and successfully separated AD subjects from OC and YC subjects with a significant margin. F-RO-948 appears to be a promising radioligand for quantitative imaging of tau in the brain of AD patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2967/jnumed.118.214437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6278898PMC
December 2018

Characterization of 3 Novel Tau Radiopharmaceuticals, C-RO-963, C-RO-643, and F-RO-948, in Healthy Controls and in Alzheimer Subjects.

J Nucl Med 2018 12 4;59(12):1869-1876. Epub 2018 May 4.

Pharma Research and Early Development, Hoffmann-La Roche, Basel, Switzerland.

C-RO-963, C-RO-643, and F-RO-948 (previously referred to as C-RO6924963, C-RO6931643, and F-RO6958948, respectively) have been reported as promising PET tracers for tau imaging based on in vitro and preclinical PET data. Here we describe the first, to our knowledge, human evaluation of these novel radiotracers. Amyloid PET-positive Alzheimer disease (AD) subjects and younger controls each received 2 different tau tracers. Dynamic 90-min scans were obtained after bolus injection of C-RO-963, C-RO-643, or F-RO-948. Arterial blood sampling was performed on 11 healthy controls and 11 AD subjects. Regions were defined on MR images, and PET data were quantified by plasma reference graphical analysis (for total distribution volume) and target cerebellum ratio (SUV ratios of 60- to 90-min frames). SUV ratio images were also analyzed voxelwise. Five older controls each underwent 2 scans with F-RO-948 for evaluation of test-retest variability. Four AD subjects underwent a repeated F-RO-948 scan 6-22 mo after the first scan. Six additional healthy controls (3 men and 3 women; age range, 41-67 y) each underwent 1 whole-body dosimetry scan with F-RO-948. In younger controls, SUV was observed in the temporal lobe with values of approximately 3.0 for C-RO-963, 1.5 for C-RO-643, and 3.5 for F-RO-948. Over all brain regions and subjects, the trend was for F-RO-948 to have the highest SUV, followed by C-RO-963 and then C-RO-643. Regional analysis of SUV ratio and total distribution volume for C-RO-643 and F-RO-948 clearly discriminated the AD group from the healthy control groups. Compartmental modeling confirmed that C-RO-643 had lower brain entry than either C-RO-963 or F-RO-948 and that F-RO-948 showed better contrast between (predicted) areas of high versus low tau accumulation. Thus, our subsequent analysis focused on F-RO-948. Both voxelwise and region-based analysis of F-RO-948 binding in healthy controls versus AD subjects revealed multiple areas where AD subjects significantly differed from healthy controls. Of 22 high-binding regions, 13 showed a significant group difference (after ANOVA, = 45, < 10). Voxelwise analysis also revealed a set of symmetric clusters where AD subjects had higher binding than healthy controls (threshold of < 0.001, cluster size > 50). F-RO-948 demonstrates characteristics superior to C-RO-643 and C-RO-963 for characterization of tau pathology in AD. Regional binding data and kinetic properties of F-RO-948 compare favorably with other existing tau PET tracers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2967/jnumed.118.209916DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6278896PMC
December 2018

Preclinical Evaluation of F-RO6958948, C-RO6931643, and C-RO6924963 as Novel PET Radiotracers for Imaging Tau Aggregates in Alzheimer Disease.

J Nucl Med 2018 04 28;59(4):675-681. Epub 2017 Sep 28.

Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland.

Tau aggregates and amyloid-β (Aβ) plaques are key histopathologic features in Alzheimer disease (AD) and are considered targets for therapeutic intervention as well as biomarkers for diagnostic in vivo imaging agents. This article describes the preclinical in vitro and in vivo characterization of 3 novel compounds-RO6958948, RO6931643, and RO6924963-that bind specifically to tau aggregates and have the potential to become PET tracers for future human use. RO6958948, RO6931643, and RO6924963 were identified as high-affinity competitors at the H-T808 binding site on native tau aggregates in human late-stage AD brain tissue. Binding of tritiated compounds to brain tissue sections of AD patients and healthy controls was analyzed by macro- and microautoradiography and by costaining of tau aggregates and Aβ plaques on the same tissue section using specific antibodies. All 3 tracer candidates were radiolabeled with a PET nuclide and tested in vivo in tau-naïve baboons to assess brain uptake, distribution, clearance, and metabolism. H-RO6958948, H-RO6931643, and H-RO6924963 bound with high affinity and specificity to tau aggregates, clearly lacking affinity for concomitant Aβ plaques in human AD Braak V tissue sections. The specificity of all 3 radioligands for tau aggregates was supported, first, by binding patterns in AD sections comparable to the tau-specific radioligand H-T808; second, by very low nonspecific binding in brain tissue devoid of tau pathology, excluding significant radioligand binding to any other central nervous system target; and third, by macroscopic and microscopic colocalization and quantitative correlation of radioligand binding and tau antibody staining on the same tissue section. RO6958948, RO6931643, and RO6924963 were successfully radiolabeled with a PET nuclide at high specific activity, radiochemical purity, and yield. After intravenous administration of F-RO6958948, C-RO6931643, and C-RO6924963 to baboons, PET scans indicated good brain entry, rapid washout, and a favorable metabolism pattern. F-RO6958948, C-RO6931643, and C-RO6924963 are promising PET tracers for visualization of tau aggregates in AD. Head-to-head comparison and validation of these tracer candidates in AD patients and healthy controls will be reported in due course.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2967/jnumed.117.196741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5932750PMC
April 2018

Identification of Three Novel Radiotracers for Imaging Aggregated Tau in Alzheimer's Disease with Positron Emission Tomography.

J Med Chem 2017 09 12;60(17):7350-7370. Epub 2017 Jul 12.

Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd. , CH-4070 Basel, Switzerland.

Aggregates of tau and beta amyloid (Aβ) plaques constitute the histopathological hallmarks of Alzheimer's disease and are prominent targets for novel therapeutics as well as for biomarkers for diagnostic in vivo imaging. In recent years much attention has been devoted to the discovery and development of new PET tracers to image tau aggregates in the living human brain. Access to a selective PET tracer to image and quantify tau aggregates represents a unique tool to support the development of any novel therapeutic agent targeting pathological forms of tau. The objective of the study described herein was to identify such a novel radiotracer. As a result of this work, we discovered three novel PET tracers (2-(4-[C]methoxyphenyl)imidazo[1,2-a]pyridin-7-amine 7 ([C]RO6924963), N-[C]methyl-2-(3-methylphenyl)imidazo[1,2-a]pyrimidin-7-amine 8 ([C]RO6931643), and [F]2-(6-fluoropyridin-3-yl)pyrrolo[2,3-b:4,5-c']dipyridine 9 ([F]RO6958948)) with high affinity for tau neurofibrillary tangles, excellent selectivity against Aβ plaques, and appropriate pharmacokinetic and metabolic properties in mice and non-human primates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.7b00632DOI Listing
September 2017

Sembragiline: A Novel, Selective Monoamine Oxidase Type B Inhibitor for the Treatment of Alzheimer's Disease.

J Pharmacol Exp Ther 2017 09 22;362(3):413-423. Epub 2017 Jun 22.

Roche Innovation Center Basel, Pharma Research and Early Development, F. Hoffmann-La Roche Ltd., Basel, Switzerland (E.B., B.B., F.G., E.P., S.N., H.L., J.M., A.P., and R.W.); Buck Institute for Research on Aging, Novato, California (S.C., S.R., A.R., A.S., and J.A.); and Evotec International GmbH, Hamburg, Germany (A.M.C. and B.E.).

Monoamine oxidase B (MAO-B) has been implicated in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative disorders. Increased MAO-B expression in astroglia has been observed adjacent to amyloid plaques in AD patient brains. This phenomenon is hypothesized to lead to increased production of hydrogen peroxide and reactive oxygen species (ROS), thereby contributing to AD pathology. Therefore, reduction of ROS-induced oxidative stress via inhibition of MAO-B activity may delay the progression of the disease. In the present study we report the pharmacological properties of sembragiline, a novel selective MAO-B inhibitor specifically developed for the treatment of AD, and on its effect on ROS-mediated neuronal injury and astrogliosis in MAO-B transgenic animals. Sembragiline showed potent and long-lasting MAO-B-selective inhibition and did not inhibit MAO-A at doses where full inhibition of MAO-B was observed. Such selectivity should translate into a favorable clinical safety profile. Indeed, sembragiline neither induced the serotonin syndrome when administered together with the serotonin precursor l-5-hydroxytryptophan in combination with antidepressants such as fluoxetine, nor potentiated the pressor effect of tyramine. Additionally, in experiments using a transgenic animal model conditionally overexpressing MAO-B in astroglia, sembragiline protected against neuronal loss and reduced both ROS formation and reactive astrogliosis. Taken together, these findings warrant further investigation of the potential therapeutic benefit of MAO-B inhibitors in patients with AD and other neurologic disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/jpet.117.241653DOI Listing
September 2017

Sembragiline in Moderate Alzheimer's Disease: Results of a Randomized, Double-Blind, Placebo-Controlled Phase II Trial (MAyflOwer RoAD).

J Alzheimers Dis 2017 ;58(4):1217-1228

Roche Product Development Neuroscience, Roche Innovation Center Basel, F.Hoffmann-La Roche Ltd, Switzerland.

Background: Sembragiline is a potent, selective, long-acting, and reversible MAO-B inhibitor developed as a potential treatment for Alzheimer's disease (AD).

Objective: To evaluate the safety, tolerability, and efficacy of sembragiline in patients with moderate AD.

Methods: In this Phase II study (NCT01677754), 542 patients with moderate dementia (MMSE 13-20) on background acetylcholinesterase inhibitors with/without memantine were randomized (1:1:1) to sembragiline 1 mg, 5 mg, or placebo once daily orally for 52 weeks.

Results: No differences between treated groups and placebo in adverse events or in study completion. The primary endpoint, change from baseline in ADAS-Cog11, was not met. At Week 52, the difference between sembragiline and placebo in ADAS-Cog11 change from baseline was - 0.15 (p = 0.865) and 0.90 (p = 0.312) for 1 and 5 mg groups, respectively. Relative to placebo at Week 52 (but not at prior assessment times), the 1 mg and 5 mg sembragiline groups showed differences in ADCS-ADL of 2.64 (p = 0.051) and 1.89 (p = 0.160), respectively. A treatment effect in neuropsychiatric symptoms (as assessed by the difference between sembragiline and placebo on BEHAVE-AD-FW) was also seen at Week 52 only: - 2.80 (p = 0.014; 1 mg) and - 2.64 (p = 0.019; 5 mg), respectively. A post hoc subgroup analysis revealed greater treatment effects on behavior and functioning in patients with more severe baseline behavioral symptoms (above the median).

Conclusions: This study showed that sembragiline was well-tolerated in patients with moderate AD. The study missed its primary and secondary endpoints. Post hoc analyses suggested potential effect on neuropsychiatric symptoms and functioning in more behaviorally impaired study population at baseline.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3233/JAD-161309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523913PMC
May 2018

Kinetic Modeling of the Tau PET Tracer F-AV-1451 in Human Healthy Volunteers and Alzheimer Disease Subjects.

J Nucl Med 2017 07 1;58(7):1124-1131. Epub 2016 Dec 1.

Molecular NeuroImaging LLC, New Haven, Connecticut.

F-AV-1451 is currently the most widely used of several experimental tau PET tracers. The objective of this study was to evaluate F-AV-1451 binding with full kinetic analysis using a metabolite-corrected arterial input function and to compare parameters derived from kinetic analysis with SUV ratio (SUVR) calculated over different imaging time intervals. F-AV-1451 PET brain imaging was completed in 16 subjects: 4 young healthy volunteers (YHV), 4 aged healthy volunteers (AHV), and 8 Alzheimer disease (AD) subjects. Subjects were imaged for 3.5 h, with arterial blood samples obtained throughout. PET data were analyzed using plasma and reference tissue-based methods to estimate the distribution volume, binding potential (BP), and SUVR. BP and SUVR were calculated using the cerebellar cortex as a reference region and were compared across the different methods and across the 3 groups (YHV, AHV, and AD). AD demonstrated increased F-AV-1451 retention compared with YHV and AHV based on both invasive and noninvasive analyses in cortical regions in which paired helical filament tau accumulation is expected in AD. A correlation of > 0.93 was found between BP (130 min) and SUVR-1 at all time intervals. Cortical SUVR curves reached a relative plateau around 1.0-1.2 for YHV and AHV by approximately 50 min, but increased in AD by up to approximately 20% at 110-130 min and approximately 30% at 160-180 min relative to 80-100 min. Distribution volume (130 min) was lower by 30%-35% in the YHV than AHV. Our data suggest that although F-AV-1451 SUVR curves do not reach a plateau and are still increasing in AD, an SUVR calculated over an imaging window of 80-100 min (as currently used in clinical studies) provides estimates of paired helical filament tau burden in good correlation with BP, whereas SUVR sensitivity to regional cerebral blood changes needs further investigation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2967/jnumed.116.182881DOI Listing
July 2017

Increased basal ganglia binding of F-AV-1451 in patients with progressive supranuclear palsy.

Mov Disord 2017 01 6;32(1):108-114. Epub 2016 Oct 6.

Lund University, Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Malmö, Sweden.

Background: Progressive supranuclear palsy (PSP) is difficult to diagnose accurately. The recently developed tau PET tracers may improve the diagnostic work-up of PSP.

Methods: Regional tau accumulation was studied using F-AV-1451 PET in 11 patients with PSP and 11 age-matched healthy controls in the Swedish BioFinder study.

Results: F-AV-1451 standard uptake volume ratios were significantly higher in the basal ganglia in PSP patients when compared with controls (globus pallidus 1.75 vs 1.50; putamen 1.51 vs 1.35). Retention in the basal ganglia was correlated with age in both groups (r = .43-.78, P < .05). In PSP, we observed a significant correlation between clinical deterioration measured with the PSP rating scale and standard uptake volume ratios in the globus pallidus (r = .74, P < .05). However, no F-AV-1451 retention was observed in the cerebral cortex or white matter of either PSP patients or controls, and autoradiography did not reveal any specific binding of AV-1451 to PSP tau aggregates.

Conclusion: We found higher F-AV-1451 retention in the basal ganglia of PSP patients when compared with healthy elderly controls, but also increases with age in both controls and patients. As a result of the overlap in retention between diagnostic groups and the age-dependent increase present also in controls, F-AV-1451 PET might not reliably distinguish individual patients with PSP from controls. However, further studies are needed to evaluate whether F-AV-1451 PET might be useful as a progression marker in clinical PSP trials. © The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mds.26813DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6204612PMC
January 2017

Alterations in High-Frequency Neuronal Oscillations in a Cynomolgus Macaque Test of Sustained Attention Following NMDA Receptor Antagonism.

Neuropsychopharmacology 2016 Apr 10;41(5):1319-28. Epub 2015 Sep 10.

Center for Neuroscience, Biosciences Division, SRI International, Menlo Park, CA, USA.

A growing body of evidence indicates that neuronal oscillations in the gamma frequency range (30-80 Hz) are disturbed in schizophrenic patients during cognitive processes and may represent an endophenotype of the disease. N-methyl-D-aspartate (NMDA) receptor antagonists have been used experimentally to induce schizophrenia-like symptoms including cognitive deficits in animals and humans. Here we characterized neuronal oscillations and event-related potentials (ERPs) in Cynomolgus macaques fully trained to perform a continuous performance test (CPT) in the presence and absence of the NMDA antagonist phencyclidine (PCP). Macaques (n=8) were trained to touch 'target' stimuli and ignore 'distractor' stimuli presented randomly on a touchscreen. Subsequently, all subjects were implanted with epidural EEG electrodes over frontal (FC) and parietal cortices (PC) and later tested under vehicle (saline, i.m.) or acute PCP (0.1-0.3 mg/kg, i.m.) conditions. Compared with vehicle treatment, PCP produced a significant dose-dependent decrease in CPT performance accuracy and increased reaction times. Furthermore, PCP elevated the amplitudes of 'low' (30-50 Hz) and 'high' (51-80 Hz) gamma oscillations in FC and PC around target presentations for all correct responses. The CPT accuracy was inversely correlated with the gamma band amplitude in the presence of PCP. Additionally, PCP delayed the N100 peak latency in FC, and prolonged and suppressed the cognitively relevant P300 component of mean ERPs in FC and PC, respectively. The NMDA receptor antagonist-induced alteration in neuronal oscillations and ERPs may contribute to the observed cognitive deficits in macaques, and enhance our understanding of EEG recordings as a translatable biomarker.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/npp.2015.281DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4793115PMC
April 2016

Label-free assay for the assessment of nonspecific binding of positron emission tomography tracer candidates.

Eur J Pharm Sci 2015 Nov 2;79:27-35. Epub 2015 Sep 2.

F. Hoffmann-La Roche Ltd., pRED, Pharma Research and Early Development, Pharmaceutical Research, Innovation Center Basel, CH-4070 Basel, Switzerland.. Electronic address:

Positron emission tomography (PET) is a valuable non-invasive technique for the visualization of drug tissue distribution and receptor occupancy at the target site in living animals and men. Many potential PET tracers, however, fail due to an unfavorably high non-specific binding (NSB) to non-target proteins and phospholipid membranes which compromises the sensitivity of PET. Hence, there is a high demand to assess the extent of NSB as early as possible in the PET tracer development process, preferentially before ligands are radiolabeled and elaborate imaging studies are performed. The purpose of this study was to establish a novel Lipid Membrane Binding Assay (LIMBA) for assessing the tendency of potential tracers to bind non-specifically to brain tissue. The assay works with unlabeled compounds and allows the medium-throughput measurement of brain tissue/water distribution coefficients, logDbrain (pH7.4), at minimal expense of animal tissue. To validate LIMBA, logDbrain (pH7.4) values were measured and compared with NSB estimates derived from in vivo PET studies in human brain (n=10 tracers, literature data), and in vitro autoradiography studies in rat and mouse brain slices (n=30 tritiated radioligands). Good agreement between logDbrain (pH7.4) and the volume of distribution in brain of non-specifically bound tracer in PET was achieved, pertaining to compounds classified as non-substrates of P-glycoprotein (R(2)≥0.88). The ability of LIMBA for the prediction of NSB was further supported by the strong correlation between logDbrain (pH7.4) and NSB in brain autoradiography (R(2)≥0.76), whereas octanol/water distribution coefficients, logDoct (pH7.4) were less predictive. In conclusion, LIMBA provides a fast and reliable tool for identifying compounds with unfavorably high NSB in brain tissue. The data may be used in conjunction with other parameters like target affinity, density and membrane permeability for the selection of most promising compounds to be further investigated in vivo as potential novel PET tracers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejps.2015.08.014DOI Listing
November 2015

Application of cross-species PET imaging to assess neurotransmitter release in brain.

Psychopharmacology (Berl) 2015 Nov 30;232(21-22):4129-57. Epub 2015 Apr 30.

Neuroscience Research Unit, Pfizer Inc, Cambridge, MA, USA.

Rationale: This review attempts to summarize the current status in relation to the use of positron emission tomography (PET) imaging in the assessment of synaptic concentrations of endogenous mediators in the living brain.

Objectives: Although PET radioligands are now available for more than 40 CNS targets, at the initiation of the Innovative Medicines Initiative (IMI) "Novel Methods leading to New Medications in Depression and Schizophrenia" (NEWMEDS) in 2009, PET radioligands sensitive to an endogenous neurotransmitter were only validated for dopamine. NEWMEDS work-package 5, "Cross-species and neurochemical imaging (PET) methods for drug discovery", commenced with a focus on developing methods enabling assessment of changes in extracellular concentrations of serotonin and noradrenaline in the brain.

Results: Sharing the workload across institutions, we utilized in vitro techniques with cells and tissues, in vivo receptor binding and microdialysis techniques in rodents, and in vivo PET imaging in non-human primates and humans. Here, we discuss these efforts and review other recently published reports on the use of radioligands to assess changes in endogenous levels of dopamine, serotonin, noradrenaline, γ-aminobutyric acid, glutamate, acetylcholine, and opioid peptides. The emphasis is on assessment of the availability of appropriate translational tools (PET radioligands, pharmacological challenge agents) and on studies in non-human primates and human subjects, as well as current challenges and future directions.

Conclusions: PET imaging directed at investigating changes in endogenous neurochemicals, including the work done in NEWMEDS, have highlighted an opportunity to further extend the capability and application of this technology in drug development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00213-015-3938-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4600473PMC
November 2015

Pharmacology of basimglurant (RO4917523, RG7090), a unique metabotropic glutamate receptor 5 negative allosteric modulator in clinical development for depression.

J Pharmacol Exp Ther 2015 Apr 9;353(1):213-33. Epub 2015 Feb 9.

Roche Pharmaceutical Research and Early Development, Discovery Neuroscience, Neuroscience, Ophthalmology, and Rare Diseases (L.L., S.H.S., B.K., A.B., M.v.K., M.H., E.B., E.P., W.S., J.G.W.), Discovery Chemistry (E.V., S.K., J.W., G.J.), Operations for Neuroscience, Ophthalmology, and Rare Diseases (R.H.P., J.-L.M.), Pharmaceutical Sciences (A.C.H., A.P., C.F., A.G., M.S., N.J.P., L.P., U.N.), and Small Molecules Process Research and Synthesis (T.H.), Roche Innovation Center Basel, Basel, Switzerland; and Center for Neuroscience, Biosciences Division, SRI International, Menlo Park, California (S.R.M., T.S.K.).

Major depressive disorder (MDD) is a serious public health burden and a leading cause of disability. Its pharmacotherapy is currently limited to modulators of monoamine neurotransmitters and second-generation antipsychotics. Recently, glutamatergic approaches for the treatment of MDD have increasingly received attention, and preclinical research suggests that metabotropic glutamate receptor 5 (mGlu5) inhibitors have antidepressant-like properties. Basimglurant (2-chloro-4-[1-(4-fluoro-phenyl)-2,5-dimethyl-1H-imidazol-4-ylethynyl]-pyridine) is a novel mGlu5 negative allosteric modulator currently in phase 2 clinical development for MDD and fragile X syndrome. Here, the comprehensive preclinical pharmacological profile of basimglurant is presented with a focus on its therapeutic potential for MDD and drug-like properties. Basimglurant is a potent, selective, and safe mGlu5 inhibitor with good oral bioavailability and long half-life supportive of once-daily administration, good brain penetration, and high in vivo potency. It has antidepressant properties that are corroborated by its functional magnetic imaging profile as well as anxiolytic-like and antinociceptive features. In electroencephalography recordings, basimglurant shows wake-promoting effects followed by increased delta power during subsequent non-rapid eye movement sleep. In microdialysis studies, basimglurant had no effect on monoamine transmitter levels in the frontal cortex or nucleus accumbens except for a moderate increase of accumbal dopamine, which is in line with its lack of pharmacological activity on monoamine reuptake transporters. These data taken together, basimglurant has favorable drug-like properties, a differentiated molecular mechanism of action, and antidepressant-like features that suggest the possibility of also addressing important comorbidities of MDD including anxiety and pain as well as daytime sleepiness and apathy or lethargy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/jpet.114.222463DOI Listing
April 2015

Metabotropic glutamate receptor 5 negative allosteric modulators: discovery of 2-chloro-4-[1-(4-fluorophenyl)-2,5-dimethyl-1H-imidazol-4-ylethynyl]pyridine (basimglurant, RO4917523), a promising novel medicine for psychiatric diseases.

J Med Chem 2015 Feb 2;58(3):1358-71. Epub 2015 Feb 2.

Discovery Chemistry, Therapeutic Modalities, ‡Discovery Neuroscience, Neuroscience, Ophthalmology & Rare Diseases (NORD), §Communications, ∥Pharmaceutical Sciences, ⊥Molecular Design and Chemical Biology, Therapeutic Modalities, #Small Molecules Process Research and Synthesis, Therapeutic Modalities, ∞Infections Diseases, and ×Operations for Neuroscience, Ophthalmology, and Rare Diseases (NORD), Innovation Center Basel, Roche Pharmaceutical Research and Early Development , Grenzacherstrasse 124, CH-4070 Basel, Switzerland.

Negative allosteric modulators (NAMs) of metabotropic glutamate receptor 5 (mGlu5) have potential for the treatment of psychiatric diseases including depression, fragile X syndrome (FXS), anxiety, obsessive-compulsive disorders, and levodopa induced dyskinesia in Parkinson's disease. Herein we report the optimization of a weakly active screening hit 1 to the potent and selective compounds chloro-4-[1-(4-fluorophenyl)-2,5-dimethyl-1H-imidazol-4-ylethynyl]pyridine (basimglurant, 2) and 2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine (CTEP, 3). Compound 2 is active in a broad range of anxiety tests reaching the same efficacy but at a 10- to 100-fold lower dose compared to diazepam and is characterized by favorable DMPK properties in rat and monkey as well as an excellent preclinical safety profile and is currently in phase II clinical studies for the treatment of depression and fragile X syndrome. Analogue 3 is the first reported mGlu5 NAM with a long half-life in rodents and is therefore an ideal tool compound for chronic studies in mice and rats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jm501642cDOI Listing
February 2015

Effect of bitopertin, a glycine reuptake inhibitor, on negative symptoms of schizophrenia: a randomized, double-blind, proof-of-concept study.

JAMA Psychiatry 2014 Jun;71(6):637-46

F. Hoffmann-La Roche, Basel, Switzerland.

Importance: In schizophrenia, the severity of negative symptoms is a key predictor of long-term disability. Deficient signaling through the N-methyl-D-aspartate receptor is hypothesized to underlie many signs and symptoms associated with schizophrenia in particular negative symptoms. Glycine acts as an N-methyl-D-aspartate receptor coagonist. Blockade of the glycine transporter type 1 to inhibit glycine reuptake and elevate synaptic glycine concentrations represents an effective strategy to enhance N-methyl-D-aspartate receptor transmission.

Objective: To determine the efficacy and safety of bitopertin (RG1678), a glycine reuptake inhibitor, in patients with schizophrenia and predominant negative symptoms who were stable while taking an antipsychotic treatment.

Design, Setting, And Participants: This randomized, double-blind, placebo-controlled, phase 2 proof-of-concept trial involved 323 patients with schizophrenia and predominant negative symptoms across 66 sites worldwide.

Interventions: Bitopertin (10, 30, or 60 mg/d) or placebo added to standard antipsychotic therapy for a treatment duration of 8 weeks.

Main Outcomes And Measures: Change from baseline in the Positive and Negative Syndrome Scale negative factor score.

Results: In the per-protocol population, 8 weeks of treatment with bitopertin was associated with a significant reduction of negative symptoms in the 10-mg/d (mean [SE] reduction in negative symptoms score, -25% [2%]; P = .049) and 30-mg/d (mean [SE], -25% [2%]; P = .03) bitopertin groups, a significantly higher response rate and a trend toward improved functioning in the 10-mg/d group when compared with placebo (mean [SE], -19% [2%]). Results reached trend-level significance in the intent-to-treat population. Estimates of bitopertin binding to glycine transporter type 1 showed that low to medium levels of occupancy yielded optimal efficacy in patients, consistent with findings in preclinical assays.

Conclusions And Relevance: Bitopertin-mediated glycine reuptake inhibition may represent a novel treatment option for schizophrenia, with the potential to address negative symptoms.

Trial Registration: clinicaltrials.gov Identifier: NCT00616798.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1001/jamapsychiatry.2014.163DOI Listing
June 2014

Neuropharmacological and neurobiological relevance of in vivo ¹H-MRS of GABA and glutamate for preclinical drug discovery in mental disorders.

Neuropsychopharmacology 2014 Sep 3;39(10):2331-9. Epub 2014 Apr 3.

pRED, Pharma Research & Early Development, DTA Neuroscience, F. Hoffmann-La Roche, Basel, Switzerland.

Proton magnetic resonance spectroscopy ((1)H-magnetic resonance spectroscopy (MRS)) is a translational modality with great appeal for neuroscience since the two major excitatory and inhibitory neurotransmitters, glutamate, and GABA, can be noninvasively quantified in vivo and have served to explore disease state and effects of drug treatment. Yet, if (1)H-MRS shall serve for decision making in preclinical pharmaceutical drug discovery, it has to meet stringent requirements. In particular, (1)H-MRS needs to reliably report neurobiologically relevant but rather small changes in neurometabolite levels upon pharmacological interventions and to faithfully appraise target engagement in the associated molecular pathways at pharmacologically relevant doses. Here, we thoroughly addressed these matters with a three-pronged approach. Firstly, we determined the sensitivity and reproducibility of (1)H-MRS in rat at 9.4 Tesla for detecting changes in GABA and glutamate levels in the striatum and the prefrontal cortex, respectively. Secondly, we evaluated the neuropharmacological and neurobiological relevance of the MRS readouts by pharmacological interventions with five well-characterized drugs (vigabatrin, 3-mercaptopropionate, tiagabine, methionine sulfoximine, and riluzole), which target key nodes in GABAergic and glutamatergic neurotransmission. Finally, we corroborated the MRS findings with ex vivo biochemical analyses of drug exposure and neurometabolite concentrations. For all five interventions tested, (1)H-MRS provided distinct drug dose-effect relationships in GABA and glutamate over preclinically relevant dose ranges and changes as low as 6% in glutamate and 12% in GABA were reliably detected from 16 mm(3) volumes-of-interest. Taken together, these findings demonstrate the value and limitation of quantitative (1)H-MRS of glutamate and GABA for preclinical pharmaceutical research in mental disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/npp.2014.79DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4138741PMC
September 2014

Analysis of adult neurogenesis: evidence for a prominent "non-neurogenic" DCX-protein pool in rodent brain.

PLoS One 2013 14;8(5):e59269. Epub 2013 May 14.

F. Hoffmann-La Roche AG, Pharma Research & Early Development, DTA Neuroscience, Basel, Switzerland.

Here, we have developed a highly sensitive immunoassay for Dcx to characterize expression in brain and cerebrospinal fluid (CSF) of rodents. We demonstrate that Dcx is widely expressed during development in various brain regions and as well can be detected in cerebrospinal fluid of rats (up to 30 days postnatal). While Dcx protein level decline in adulthood and were detectable in neurogenic regions of the adult rodent brain, similar levels were also detectable in brain regions expected to bear no neurogenesis including the cerebral cortex and CA1/CA3 enriched hippocampus. We monitored DCX protein levels after paradigms to increase or severely decrease adult hippocampal neurogenesis, namely physical activity and cranial radiation, respectively. In both paradigms, Dcx protein- and mRNA-levels clearly reflected changes in neurogenesis in the hippocampus. However, basal Dcx-levels are unaffected in non-neurogenic regions (e.g. CA1/CA3 enriched hippocampus, cortex). These data suggest that there is a substantial "non-neurogenic" pool of Dcx- protein, whose regulation can be uncoupled from adult neurogenesis suggesting caution for the interpretation of such studies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0059269PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3653925PMC
December 2013

Dual hypocretin receptor antagonism is more effective for sleep promotion than antagonism of either receptor alone.

PLoS One 2012 2;7(7):e39131. Epub 2012 Jul 2.

Center for Neuroscience and Metabolic Disease Research, SRI International, Menlo Park, California, USA.

The hypocretin (orexin) system is involved in sleep/wake regulation, and antagonists of both hypocretin receptor type 1 (HCRTR1) and/or HCRTR2 are considered to be potential hypnotic medications. It is currently unclear whether blockade of either or both receptors is more effective for promoting sleep with minimal side effects. Accordingly, we compared the properties of selective HCRTR1 (SB-408124 and SB-334867) and HCRTR2 (EMPA) antagonists with that of the dual HCRTR1/R2 antagonist almorexant in the rat. All 4 antagonists bound to their respective receptors with high affinity and selectivity in vitro. Since in vivo pharmacokinetic experiments revealed poor brain penetration for SB-408124, SB-334867 was selected for subsequent in vivo studies. When injected in the mid-active phase, SB-334867 produced small increases in rapid-eye-movement (REM) and non-REM (NR) sleep. EMPA produced a significant increase in NR only at the highest dose studied. In contrast, almorexant decreased NR latency and increased both NR and REM proportionally throughout the subsequent 6 h without rebound wakefulness. The increased NR was due to a greater number of NR bouts; NR bout duration was unchanged. At the highest dose tested (100 mg/kg), almorexant fragmented sleep architecture by increasing the number of waking and REM bouts. No evidence of cataplexy was observed. HCRTR1 occupancy by almorexant declined 4-6 h post-administration while HCRTR2 occupancy was still elevated after 12 h, revealing a complex relationship between occupancy of HCRT receptors and sleep promotion. We conclude that dual HCRTR1/R2 blockade is more effective in promoting sleep than blockade of either HCRTR alone. In contrast to GABA receptor agonists which induce sleep by generalized inhibition, HCRTR antagonists seem to facilitate sleep by reducing waking "drive".
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0039131PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388080PMC
November 2012

Pre-clinical characterization of [11C]R05013853 as a novel radiotracer for imaging of the glycine transporter type 1 by positron emission tomography.

Neuroimage 2013 Jul 10;75:291-300. Epub 2011 Dec 10.

The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA; Department of Psychiatry, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Department of Neuroscience, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Department of Environmental Health Sciences, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Honorary Professor of Neuroscience and Pharmacology, University of Copenhagen, Denmark.

A specific positron emission tomography (PET) radiotracer for the glycine transporter type 1 (GlyT1) would constitute an imaging biomarker to investigate the distribution of GlyT1 in normal individuals and those with neuropsychiatric disorders. In addition it could demonstrate the ability of a novel drug to reach its target in the brain and enable receptor occupancy studies, thus facilitating drug development. In this article we describe the evaluation in non-human primates of two candidate PET radiotracers ([(11)C]RO5013852 and [(11)C]RO5013853) previously characterized in the rat. Both radiotracers showed acceptable uptake in the baboon brain and heterogeneous distribution consistent with that reported for GlyT1. In vivo blockade studies with two specific glycine reuptake inhibitors (GRIs), RO5013853 and bitopertin (RG1678, reduced uptake of both tracers to homogenous levels across brain regions and demonstrated specificity of the signal. [(11)C]RO5013853 showed a larger specific signal and slightly higher brain uptake and was therefore selected for further characterization. Quantitative compartmental analysis of PET data showed that the 2-tissue compartment model with 5 parameters was the most appropriate to describe the kinetics of [(11)C]RO5013853. Two additional methods were used: a) the Logan graphical analysis using plasma input and, b) a linear parametric imaging approach with the 2-tissue compartmental model. These produced VT estimates of comparable magnitude, namely, pons, thalamus and cerebellum>caudate, putamen and cortical regions. High resolution autoradiography with tritiated RO5013853 was used to confirm the binding pattern observed by PET. In vivo metabolism studies in the baboon demonstrated the formation of a single, radiolabeled metabolite more polar than the parent compound. Finally, [(11)C]RO5013853 was used to quantify the degree of cerebral GlyT1 occupancy observed in the baboon following oral administration of bitopertin, a selective GRI presently in Phase III clinical trial. Plasma concentrations of approximately 150-300 ng/mL were estimated to produce 50% GlyT1 occupancy in the thalamus, the cerebellum and the pons. [(11)C]RO5013853 is a promising radiotracer for in vivo imaging of the GlyT1. It can be easily radiolabeled, exhibits moderate metabolism, displays a good specific signal, and is suitable for receptor occupancy studies of therapeutic compounds that target the GlyT1. The successful characterization of [(11)C]RO5013853 in healthy volunteers is presented in this NeuroImage issue (Wong et al., 2013).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2011.11.090DOI Listing
July 2013

Characterization of [11C]RO5013853, a novel PET tracer for the glycine transporter type 1 (GlyT1) in humans.

Neuroimage 2013 Jul 1;75:282-290. Epub 2011 Dec 1.

F. Hoffmann-La Roche Ltd., Pharmaceutical Division, Grenzacherstrasse 124, CH-4070 Basel, Switzerland.

We characterize a novel radioligand for the glycine transporter type 1 (GlyT1), [(11)C]RO5013853, in humans. Ten healthy male volunteers, 23-60 years of age, were enrolled in this PET study; seven subjects participated in the evaluation of test-retest reliability and three subjects in whole body dosimetry. Subjects were administered intravenous bolus injections of approximately 1100 MBq (30 mCi) [(11)C]RO5013853 with a high specific activity of about 481 GBq (13 Ci)/μmol. Standard compartmental model analysis with arterial plasma input function, and an alternative noninvasive analysis method which was evaluated and validated by occupancy studies in both baboons and humans, were performed. Mean parameter estimates of the volumes of distribution (VT) obtained by a 2-tissue 5-parameter model were higher in the cerebellum, pons, and thalamus (1.99 to 2.59 mL/mL), and lower in the putamen, caudate, and cortical areas (0.86 to 1.13 mL/mL), with estimates showing less than 10% difference between test and retest scans. Tracer retention was effectively blocked by the specific glycine reuptake inhibitor (GRI), bitopertin (RG1678). [(11)C]RO5013853 was safe and well tolerated. Human dosimetry studies showed that the effective dose was approximately 0.0033 mSv/MBq, with the liver receiving the highest absorbed dose. In conclusion, quantitative dynamic PET of the human brain after intravenous injection of [(11)C]RO5013853 attains reliable measurements of GlyT1 binding in accordance with the expected transporter distribution in the human brain. [(11)C]RO5013853 is a radioligand suitable for further clinical PET studies. Full characterization of a novel radiotracer for GlyT1 in humans is provided. The tracer has subsequently been used to assess receptor occupancy in healthy volunteers and to estimate occupancy at doses associated with best efficacy in a clinical trial with schizophrenic patients with predominantly negative symptoms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2011.11.052DOI Listing
July 2013

Glycine reuptake inhibitor RG1678: a pharmacologic characterization of an investigational agent for the treatment of schizophrenia.

Neuropharmacology 2012 Feb 27;62(2):1152-61. Epub 2011 Nov 27.

CNS Discovery, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070 Basel, Switzerland.

Dysfunctional N-methyl-d-aspartate (NMDA) receptor neurotransmission has been implicated in the pathophysiology of schizophrenia. It is thought that this abnormal functioning can be corrected by increasing availability of the NMDA co-agonist glycine through inhibition of glycine transporter type 1 (GlyT1). Herein is described the pharmacologic profile of RG1678, a potent and noncompetitive glycine reuptake inhibitor. In vitro, RG1678 noncompetitively inhibited glycine uptake at human GlyT1 with a concentration exhibiting half-maximal inhibition (IC(50)) of 25 nM and competitively blocked [(3)H]ORG24598 binding sites at human GlyT1b in membranes from Chinese hamster ovary cells. In hippocampal CA1 pyramidal cells, RG1678 enhanced NMDA-dependent long-term potentiation at 100 nM but not at 300 nM. In vivo, RG1678 dose-dependently increased cerebrospinal fluid and striatal levels of glycine measured by microdialysis in rats. Additionally RG1678 attenuated hyperlocomotion induced by the psychostimulant d-amphetamine or the NMDA receptor glycine site antagonist L-687,414 in mice. RG1678 also prevented the hyper-response to d-amphetamine challenge in rats treated chronically with phencyclidine, an NMDA receptor open-channel blocker. In the latter experiment, a decrease in ex vivo striatal [(3)H]raclopride binding was also measured. These data demonstrate that RG1678 is a potent, noncompetitive glycine reuptake inhibitor that can modulate both glutamatergic and dopaminergic neurotransmission in animal experiments that model aspects of schizophrenia. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuropharm.2011.11.008DOI Listing
February 2012

Molecular recognition at the active site of catechol-O-methyltransferase (COMT): adenine replacements in bisubstrate inhibitors.

Chemistry 2011 May 27;17(23):6369-81. Epub 2011 Apr 27.

Laboratorium für Organische Chemie, ETH-Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland.

L-Dopa, the standard therapeutic for Parkinson's disease, is inactivated by the enzyme catechol-O-methyltransferase (COMT). COMT catalyzes the transfer of an activated methyl group from S-adenosylmethionine (SAM) to its catechol substrates, such as L-dopa, in the presence of magnesium ions. The molecular recognition properties of the SAM-binding site of COMT have been investigated only sparsely. Here, we explore this site by structural alterations of the adenine moiety of bisubstrate inhibitors. The molecular recognition of adenine is of special interest due to the great abundance and importance of this nucleobase in biological systems. Novel bisubstrate inhibitors with adenine replacements were developed by structure-based design and synthesized using a nucleosidation protocol introduced by Vorbrüggen and co-workers. Key interactions of the adenine moiety with COMT were measured with a radiochemical assay. Several bisubstrate inhibitors, most notably the adenine replacements thiopyridine, purine, N-methyladenine, and 6-methylpurine, displayed nanomolar IC(50) values (median inhibitory concentration) for COMT down to 6 nM. A series of six cocrystal structures of the bisubstrate inhibitors in ternary complexes with COMT and Mg(2+) confirm our predicted binding mode of the adenine replacements. The cocrystal structure of an inhibitor bearing no nucleobase can be regarded as an intermediate along the reaction coordinate of bisubstrate inhibitor binding to COMT. Our studies show that solvation varies with the type of adenine replacement, whereas among the adenine derivatives, the nitrogen atom at position 1 is essential for high affinity, while the exocyclic amino group is most efficiently substituted by a methyl group.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201003648DOI Listing
May 2011

Orexin receptor 2 expression in the posterior hypothalamus rescues sleepiness in narcoleptic mice.

Proc Natl Acad Sci U S A 2011 Mar 28;108(11):4471-6. Epub 2011 Feb 28.

Department of Neurology and Division of Endocrinology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.

Narcolepsy is caused by a loss of orexin/hypocretin signaling, resulting in chronic sleepiness, fragmented non-rapid eye movement sleep, and cataplexy. To identify the neuronal circuits underlying narcolepsy, we produced a mouse model in which a loxP-flanked gene cassette disrupts production of the orexin receptor type 2 (OX2R; also known as HCRTR2), but normal OX2R expression can be restored by Cre recombinase. Mice lacking OX2R signaling had poor maintenance of wakefulness indicative of sleepiness and fragmented sleep and lacked any electrophysiological response to orexin-A in the wake-promoting neurons of the tuberomammillary nucleus. These defects were completely recovered by crossing them with mice that express Cre in the female germline, thus globally deleting the transcription-disrupter cassette. Then, by using an adeno-associated viral vector coding for Cre recombinase, we found that focal restoration of OX2R in neurons of the tuberomammillary nucleus and adjacent parts of the posterior hypothalamus completely rescued the sleepiness of these mice, but their fragmented sleep was unimproved. These observations demonstrate that the tuberomammillary region plays an essential role in the wake-promoting effects of orexins, but orexins must stabilize sleep through other targets.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1012456108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3060231PMC
March 2011

Discovery of benzoylisoindolines as a novel class of potent, selective and orally active GlyT1 inhibitors.

Bioorg Med Chem Lett 2010 Dec 7;20(23):6960-5. Epub 2010 Oct 7.

F. Hoffmann-La Roche Ltd, Pharmaceutical Research Basel, Basel, Switzerland.

Benzoylisoindolines were discovered as a novel structural class of GlyT1 inhibitors. SAR studies and subsequent lead optimization efforts focused primarily on addressing hERG liability and on improving in vivo efficacy resulted in the identification of potent GlyT1 inhibitors displaying excellent selectivity and in vivo PD and PK profiles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bmcl.2010.09.124DOI Listing
December 2010

Selective GlyT1 inhibitors: discovery of [4-(3-fluoro-5-trifluoromethylpyridin-2-yl)piperazin-1-yl][5-methanesulfonyl-2-((S)-2,2,2-trifluoro-1-methylethoxy)phenyl]methanone (RG1678), a promising novel medicine to treat schizophrenia.

J Med Chem 2010 Jun;53(12):4603-14

F. Hoffmann-La Roche Ltd., Pharmaceutical Division, CH-4070 Basel, Switzerland.

The GlyT1 transporter has emerged as a key novel target for the treatment of schizophrenia. Herein, we report on the optimization of the 2-alkoxy-5-methylsulfonebenzoylpiperazine class of GlyT1 inhibitors to improve hERG channel selectivity and brain penetration. This effort culminated in the discovery of compound 10a (RG1678), the first potent and selective GlyT1 inhibitor to have a beneficial effect in schizophrenic patients in a phase II clinical trial.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jm100210pDOI Listing
June 2010

Biochemical and electrophysiological characterization of almorexant, a dual orexin 1 receptor (OX1)/orexin 2 receptor (OX2) antagonist: comparison with selective OX1 and OX2 antagonists.

Mol Pharmacol 2009 Sep 19;76(3):618-31. Epub 2009 Jun 19.

F. Hoffmann-La Roche Ltd., Bldg. 69/333, CH-4070 Basel, Switzerland.

Recent preclinical and clinical research has shown that almorexant promotes sleep in animals and humans without disrupting the sleep architecture. Here, the pharmacology and kinetics of [(3)H]almorexant binding to human orexin 1 receptor (OX(1))- and human orexin 2 receptor (OX(2))-human embryonic kidney 293 membranes were characterized and compared with those of selective OX(1) and OX(2) antagonists, including 1-(5-(2-fluoro-phenyl)-2-methyl-thiazol-4-yl)-1-((S)-2-(5-phenyl-(1,3,4)oxadiazol-2-ylmethyl)-pyrrolidin-1-yl)-methanone (SB-674042), 1-(6,8-difluoro-2-methyl-quinolin-4-yl)-3-(4-dimethylamino-phenyl)-urea (SB-408124), and N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulfonyl)-amino]-N-pyridin-3-ylmethyl-acetamide (EMPA). The effect of these antagonists was also examined in vitro on the spontaneous activity of rat ventral tegmental area (VTA) dopaminergic neurons. [(3)H]Almorexant bound to a single saturable site on hOX(1) and hOX(2) with high affinity (K(d) of 1.3 and 0.17 nM, respectively). In Schild analyses using the [(3)H]inositol phosphates assay, almorexant acted as a competitive antagonist at hOX(1) and as a noncompetitive-like antagonist at hOX(2). In binding kinetic analyses, [(3)H]almorexant had fast association and dissociation rates at hOX(1), whereas it had a fast association rate and a remarkably slow dissociation rate at hOX(2). In the VTA, orexin-A potentiated the basal firing frequency to 175 +/- 17% of control in approximately half of the neurons tested. In the presence of 1 microM SB-674042 or SB-408124, the effect of orexin-A was only partially antagonized. However, in the presence of 1 microM EMPA or 1 microM almorexant, the effect of orexin-A was completely antagonized. In conclusion, almorexant exhibited a noncompetitive and long-lasting pseudo-irreversible mode of antagonism as a result of its very slow rate of dissociation from OX(2). The electrophysiology data suggest that OX(2) might be more important than OX(1) in mediating the effect of orexin-A on slow-firing of VTA dopaminergic neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/mol.109.055152DOI Listing
September 2009