RESUMEN
PURPOSE: Tau deposition is a key pathological feature of Alzheimer's disease (AD) and other neurodegenerative disorders. The spreading of tau neurofibrillary tangles across defined brain regions corresponds to the observed level of cognitive decline in AD. Positron-emission tomography (PET) has proved to be an important tool for the detection of amyloid-beta (Aß) aggregates in the brain, and is currently being explored for detection of pathological misfolded tau in AD and other non-AD tauopathies. Several PET tracers targeting tau deposits have been discovered and tested in humans. Limitations have been reported, especially regarding their selectivity. METHODS: In our screening campaign we identified pyrrolo[2,3-b:4,5-c']dipyridine core structures with high affinity for aggregated tau. Further characterization showed that compounds containing this moiety had significantly reduced monoamine oxidase A (MAO-A) binding compared to pyrido[4,3-b]indole derivatives such as AV-1451. RESULTS: Here we present preclinical data of all ten fluoropyridine regioisomers attached to the pyrrolo[2,3-b:4,5-c']dipyridine scaffold, revealing compounds 4 and 7 with superior properties. The lead candidate [18F]PI-2620 (compound 7) displayed high affinity for tau deposits in AD brain homogenate competition assays. Specific binding to pathological misfolded tau was further demonstrated by autoradiography on AD brain sections (Braak I-VI), Pick's disease and progressive supranuclear palsy (PSP) pathology, whereas no specific tracer binding was detected on brain slices from non-demented donors. In addition to its high affinity binding to tau aggregates, the compound showed excellent selectivity with no off-target binding to Aß or MAO-A/B. Good brain uptake and fast washout were observed in healthy mice and non-human primates. CONCLUSIONS: Therefore, [18F]PI-2620 was selected for clinical validation.
Asunto(s)
Enfermedad de Alzheimer/diagnóstico por imagen , Inhibidores de la Monoaminooxidasa/síntesis química , Tomografía de Emisión de Positrones/métodos , Piridinas/síntesis química , Radiofármacos/síntesis química , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Radioisótopos de Flúor/farmacocinética , Humanos , Macaca mulatta , Ratones , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/farmacocinética , Unión Proteica , Piridinas/farmacocinética , Radiofármacos/farmacocinéticaRESUMEN
The aggregation of amyloid-ß peptides into cytotoxic oligomeric and fibrillary aggregates is believed to be one of the major pathological events in Alzheimer disease. Here we report the design and synthesis of a novel series of indole and 7-azaindole derivatives containing, nitrile, piperidine and N-methyl-piperidine substituents at the 3-position to prevent the pathological self-assembly of amyloid-ß. We have further demonstrated that substitution of the azaindole and indole derivatives at the 3 positions is required to obtain compounds with improved physicochemical properties to allow brain penetration.
Asunto(s)
Enfermedad de Alzheimer/prevención & control , Péptidos beta-Amiloides/antagonistas & inhibidores , Descubrimiento de Drogas , Indoles/farmacología , Fragmentos de Péptidos/antagonistas & inhibidores , Animales , Encéfalo/efectos de los fármacos , Humanos , Hígado/efectos de los fármacos , Masculino , RatonesRESUMEN
It is assumed that amyloid-ß aggregation is a crucial event in the pathogenesis of Alzheimer's disease. Novel 2,6-disubstituted pyridine derivatives were designed to interact with the ß-sheet conformation of Aß via donor-acceptor-donor hydrogen bond formation. A series of pyridine derivatives were synthesized and tested regarding their potential to inhibit the aggregation of Aß. The 2,6-diaminopyridine moiety was identified as a key component to inhibit Aß aggregation. Overall, compounds having three 2,6-disubstituted pyridine units separated by at least one C2- or C3-linker displayed the most potent inhibition of Aß aggregation.
Asunto(s)
Péptidos beta-Amiloides/antagonistas & inhibidores , Piridinas/farmacología , Relación Dosis-Respuesta a Droga , Humanos , Estructura Molecular , Agregado de Proteínas/efectos de los fármacos , Piridinas/síntesis química , Piridinas/química , Relación Estructura-ActividadRESUMEN
Passive immunization against ß-amyloid (Aß) has become an increasingly desirable strategy as a therapeutic treatment for Alzheimer's disease (AD). However, traditional passive immunization approaches carry the risk of Fcγ receptor-mediated overactivation of microglial cells, which may contribute to an inappropriate proinflammatory response leading to vasogenic edema and cerebral microhemorrhage. Here, we describe the generation of a humanized anti-Aß monoclonal antibody of an IgG4 isotype, known as MABT5102A (MABT). An IgG4 subclass was selected to reduce the risk of Fcγ receptor-mediated overactivation of microglia. MABT bound with high affinity to multiple forms of Aß, protected against Aß1-42 oligomer-induced cytotoxicity, and increased uptake of neurotoxic Aß oligomers by microglia. Furthermore, MABT-mediated amyloid plaque removal was demonstrated using in vivo live imaging in hAPP((V717I))/PS1 transgenic mice. When compared with a human IgG1 wild-type subclass, containing the same antigen-binding variable domains and with equal binding to Aß, MABT showed reduced activation of stress-activated p38MAPK (p38 mitogen-activated protein kinase) in microglia and induced less release of the proinflammatory cytokine TNFα. We propose that a humanized IgG4 anti-Aß antibody that takes advantage of a unique Aß binding profile, while also possessing reduced effector function, may provide a safer therapeutic alternative for passive immunotherapy for AD. Data from a phase I clinical trial testing MABT is consistent with this hypothesis, showing no signs of vasogenic edema, even in ApoE4 carriers.
Asunto(s)
Enfermedad de Alzheimer/terapia , Péptidos beta-Amiloides/inmunología , Inmunoglobulina G/farmacología , Microglía/efectos de los fármacos , Microglía/metabolismo , Fármacos Neuroprotectores/farmacología , Fragmentos de Péptidos/metabolismo , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/inmunología , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animales , Animales Recién Nacidos , Receptor 1 de Quimiocinas CX3C , Células Cultivadas , Corteza Cerebral/citología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Relación Dosis-Respuesta Inmunológica , Método Doble Ciego , Ensayo de Inmunoadsorción Enzimática , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Regulación de la Expresión Génica/inmunología , Proteínas Fluorescentes Verdes/genética , Hipocampo/citología , Humanos , Inmunoglobulina G/metabolismo , Masculino , Ratones , Ratones Transgénicos , Microscopía Confocal , Persona de Mediana Edad , Mutación/genética , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Fármacos Neuroprotectores/metabolismo , Placa Amiloide/inmunología , Placa Amiloide/metabolismo , Placa Amiloide/patología , Presenilina-1/genética , Unión Proteica/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptores de Quimiocina/genética , Estadísticas no Paramétricas , Factores de Tiempo , Factor de Necrosis Tumoral alfa/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
Increasing evidence implicates Aß peptides self-assembly and fibril formation as crucial events in the pathogenesis of Alzheimer disease. Thus, inhibiting Aß aggregation, among others, has emerged as a potential therapeutic intervention for this disorder. Herein, we employed 3-aminopyrazole as a key fragment in our design of non-dye compounds capable of interacting with Aß42 via a donor-acceptor-donor hydrogen bond pattern complementary to that of the ß-sheet conformation of Aß42. The initial design of the compounds was based on connecting two 3-aminopyrazole moieties via a linker to identify suitable scaffold molecules. Additional aryl substitutions on the two 3-aminopyrazole moieties were also explored to enhance π-π stacking/hydrophobic interactions with amino acids of Aß42. The efficacy of these compounds on inhibiting Aß fibril formation and toxicity in vitro was assessed using a combination of biophysical techniques and viability assays. Using structure activity relationship data from the in vitro assays, we identified compounds capable of preventing pathological self-assembly of Aß42 leading to decreased cell toxicity.
Asunto(s)
Péptidos beta-Amiloides/antagonistas & inhibidores , Péptidos beta-Amiloides/química , Fragmentos de Péptidos/antagonistas & inhibidores , Fragmentos de Péptidos/química , Pirazoles/química , Línea Celular Tumoral , Citotoxinas/antagonistas & inhibidores , Citotoxinas/química , Humanos , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Estructura Secundaria de Proteína , Relación Estructura-ActividadRESUMEN
The compound screening was initiated with a direct staining assay to identify compounds binding to Tau aggregates and not Abeta plaques using human brain sections derived from late stage Alzheimer's disease donors. The binding of Tau aggregate selective compounds was then quantitatively assessed with human brain derived paired helical filaments utilizing the label-free Back Scattering Interferometry assay. In vivo biodistribution experiments of selected fluorine-18 labeled compounds were performed in mice to assess brain uptake, brain washout, and defluorination. Compound 11 emerged as the most promising candidate, displaying high in vitro binding affinity and selectivity to neurofibrillary tangles. Fluorine-18 labeled compound 11 showed high brain uptake and rapid washout from the mouse brain with no observed bone uptake. Furthermore, compound 11 was able to detect Tau aggregates in tauopathy brain sections from corticobasal degeneration, progressive supranuclear palsy, and Pick's disease donors. Thus, 2-(4-(2-fluoroethoxy)piperidin-1-yl)-9-methyl-9H-pyrrolo[2,3-b:4,5-c']dipyridine (PI-2014, compound 11) was selected for characterization in a first-in-human study.