RESUMO
Genetic evidence points to deposition of amyloid-ß (Aß) as a causal factor for Alzheimer's disease. Aß generation is initiated when ß-secretase (BACE1) cleaves the amyloid precursor protein. Starting with an oxazine lead 1, we describe the discovery of a thiazine-based BACE1 inhibitor 5 with robust Aß reduction in vivo at low concentrations, leading to a low projected human dose of 14 mg/day where 5 achieved sustained Aß reduction of 80% at trough level.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Inibidores de Proteases/química , Tiazinas/química , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Citocromo P-450 CYP2C9/química , Citocromo P-450 CYP2C9/metabolismo , Cães , Avaliação Pré-Clínica de Medicamentos , Feminino , Meia-Vida , Haplorrinos , Coração/efeitos dos fármacos , Humanos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Camundongos , Inibidores de Proteases/farmacocinética , Inibidores de Proteases/farmacologia , Ratos , Ratos Sprague-Dawley , Tiazinas/metabolismo , Tiazinas/farmacologiaRESUMO
In previous studies, the introduction of electron withdrawing groups to 1,4-oxazine BACE1 inhibitors reduced the p Ka of the amidine group, resulting in compound 2 that showed excellent in vivo efficacy, lowering Aß levels in brain and CSF. However, a suboptimal cardiovascular safety margin, based on QTc prolongation, prevented further progression. Further optimization resulted in the replacement of the 2-fluoro substituent by a CF3-group, which reduced hERG inhibition. This has led to compound 3, with an improved cardiovascular safety margin and sufficiently safe in GLP toxicity studies to progress into clinical trials.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Inibidores de Proteases/química , Inibidores de Proteases/farmacologia , Administração Intravenosa , Administração Oral , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Animais , Ácido Aspártico Endopeptidases/metabolismo , Disponibilidade Biológica , Doenças Cardiovasculares/induzido quimicamente , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Cães , Avaliação Pré-Clínica de Medicamentos/métodos , Estabilidade de Medicamentos , Canal de Potássio ERG1/metabolismo , Cobaias , Humanos , Masculino , Camundongos Endogâmicos , Oxazinas/química , Fragmentos de Peptídeos/líquido cefalorraquidiano , Inibidores de Proteases/administração & dosagem , Inibidores de Proteases/efeitos adversos , Ratos Sprague-Dawley , Relação Estrutura-AtividadeRESUMO
Gamma-secretase, a membrane bound protease which cleaves the transmembrane protein amyloid-ß protein precursor (AßPP), is a therapeutic target for Alzheimer's disease. Gamma-secretase inhibitors (GSIs) and modulators (GSMs) are being investigated as potential disease-modifying agents. Preclinical in vivo models to monitor the activity on gamma-secretase are described in different species such as mouse, rat, and guinea pigs. All these models have their value in testing compounds with amyloid lowering properties, however, compound characteristics and pharmacokinetic properties, as well as other species characteristics such as limited sampling volumes of cerebrospinal fluid (CSF), recommended the use of a larger, non-rodent animal species. For this purpose, a screening model in dogs was developed for testing GSIs and GSMs. We showed that GSIs and GSMs had a dose- and time-dependent effect on Aß(37), Aß(38), Aß(40), and Aß(42) in CSF. Changes in liver function were evidenced by a transient increase in bilirubin with the GSMs and incidental increases in alanine aminotransferase for GSMs as well as GSIs. Microarray analysis of liver biopsies enabled to elucidate potential mechanisms behind the liver function changes. The relevance of the liver findings should be further evaluated in chronic pre-clinical safety studies and in humans. Based on our data, we can conclude that the dog is a very appropriate species to assess efficacy and safety of compounds which have an effect on AßPP processing such as GSMs, GSIs, and BACE-inhibitors.