Stepping closer to treating Alzheimer's disease patients with BACE1 inhibitor drugs

Abstract

Alzheimer's disease (AD) is the most common age-dependent neurodegenerative disease which impairs cognitive function and gradually causes patients to be unable to lead normal daily lives. While the etiology of AD remains an enigma, excessive accumulation of β-amyloid peptide (Aβ) is widely believed to induce pathological changes and cause dementia in brains of AD patients. BACE1 was discovered to initiate the cleavage of amyloid precursor protein (APP) at the β-secretase site. Only after this cleavage does γ-secretase further cleave the BACE1-cleaved C-terminal APP fragment to release Aβ. Hence, blocking BACE1 proteolytic activity will suppress Aβ generation. Due to the linkage of Aβ to the potential cause of AD, extensive discovery and development efforts have been directed towards potent BACE1 inhibitors for AD therapy. With the recent breakthrough in developing brain-penetrable BACE1 inhibitors, targeting amyloid deposition-mediated pathology for AD therapy has now become more practical. This review will summarize various strategies that have successfully led to the discovery of BACE1 drugs, such as MK8931, AZD-3293, JNJ-54861911, E2609 and CNP520. These drugs are currently in clinical trials and their updated states will be discussed. With the promise of reducing Aβ generation and deposition with no alarming safety concerns, the amyloid cascade hypothesis in AD therapy may finally become validated.

Keywords: Alzheimer’s disease; Amyloid deposition; Amyloid plaques; Amyloid precursor protein; Aspartyl protease; BACE1; Clinical trials; Drug discovery; Fragment based drug discovery; Secretase; Verubecestat; β-amyloid peptide.

Fig. 1

Chemical structure of compound MK-8931. MK-8931 is developed at Merck and also named as Verubecestat with a Chemical formula of C₁₇ H₁₇ F₂ N₅ O₃ S. It’s structural name is N-[3-[(5R)-3-amino-5,6-dihydro-2,5-dimethyl-1,1-dioxido-2H-1,2,4-thiadiazin-5-yl]-4-fluorophenyl]-5-fluoro-2-pyridinecarboxamide. The molecular weight is 409.41

Fig. 2

Chemical structures of compound AZD-3293. a AZD-3289 is a potent BACE1 inhibitor with a chemical formula of C₂₆H₂₈N₄O and a structure name of (3S)-3-[2-(difluoromethyl)pyridin-4-yl]-7-fluoro-3-(3-pyrimidin-5-ylphenyl)-1,2-dihydroisoindol-1-amine. It’s molecular weight is 449. b AZD-3293 is developed at AstraZeneca and Astex with a chemical formula of C₂₆H₂₈N₄O and structural name of 4-Methoxy-5′′-methyl-6′-[5-(prop-1-yn-1-yl)pyridin-3-yl]-3′H-dispiro[cyclohexane-1,2′-indene-1′,2′′-imidazole]-4′′-amine. It’s molecular weight is 412. 54