BACE1 is a key protease controlling the formation of amyloid β, a peptide hypothesized to play a significant role in the pathogenesis of Alzheimer's disease (AD). Therefore, the development of potent ...and selective inhibitors of BACE1 has been a focus of many drug discovery efforts in academia and industry. Herein, we report the nonclinical and early clinical development of LY2886721, a BACE1 active site inhibitor that reached phase 2 clinical trials in AD. LY2886721 has high selectivity against key off-target proteases, which efficiently translates in vitro activity into robust in vivo amyloid β lowering in nonclinical animal models. Similar potent and persistent amyloid β lowering was observed in plasma and lumbar CSF when single and multiple doses of LY2886721 were administered to healthy human subjects. Collectively, these data add support for BACE1 inhibition as an effective means of amyloid lowering and as an attractive target for potential disease modification therapy in AD.
The beta-site APP cleaving enzyme 1, known as BACE1, has been a widely pursued Alzheimer’s disease drug target owing to its critical role in the production of amyloid-beta. We have previously ...reported the clinical development of LY2811376 and LY2886721. LY2811376 advanced to Phase I before development was terminated due to nonclinical retinal toxicity. LY2886721 advanced to Phase II, but development was halted due to abnormally elevated liver enzymes. Herein, we report the discovery and clinical development of LY3202626, a highly potent, CNS-penetrant, and low-dose BACE inhibitor, which successfully addressed these key development challenges.
Objective
To enable use of clinical magnetic resonance images (MRIs) to quantify abnormalities in normal appearing (NA) white matter (WM) and gray matter (GM) in multiple sclerosis (MS) and to ...determine associations with MS‐related disability. Identification of these abnormalities heretofore has required specialized scans not routinely available in clinical practice.
Methods
We developed an analytic technique which normalizes image intensities based on an intensity atlas for quantification of WM and GM abnormalities in standardized MRIs obtained with clinical sequences. Gaussian mixture modeling is applied to summarize image intensity distributions from T1‐weighted and 3D‐FLAIR (T2‐weighted) images from 5010 participants enrolled in a multinational database of MS patients which collected imaging, neuroperformance and disability measures.
Results
Intensity distribution metrics distinguished MS patients from control participants based on normalized non‐lesional signal differences. This analysis revealed non‐lesional differences between relapsing MS versus progressive MS subtypes. Further, the correlation between our non‐lesional measures and disability was approximately three times greater than that between total lesion volume and disability, measured using the patient derived disease steps. Multivariate modeling revealed that measures of extra‐lesional tissue integrity and atrophy contribute uniquely, and approximately equally, to the prediction of MS‐related disability.
Interpretation
These results support the notion that non‐lesional abnormalities correlate more strongly with MS‐related disability than lesion burden and provide new insight into the basis of abnormalities in NA WM. Non‐lesional abnormalities distinguish relapsing from progressive MS but do not distinguish between progressive subtypes suggesting a common progressive pathophysiology. Image intensity parameters and existing biomarkers each independently correlate with MS‐related disability.
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Inhibition of BACE1 has become an important strategy in the quest for disease modifying agents to slow the progression of Alzheimer’s disease. We previously reported the ...fragment-based discovery of LY2811376, the first BACE1 inhibitor reported to demonstrate robust reduction of human CSF Aβ in a Phase I clinical trial. We also reported on the discovery of LY2886721, a potent BACE1 inhibitor that reached phase 2 clinical trials. Herein we describe the preparation and structure activity relationships (SAR) of a series of BACE1 inhibitors utilizing trans-cyclopropyl moieties as conformational constraints. The design, details of the stereochemically complex organic synthesis, and biological activity of these BACE1 inhibitors is described.
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The BACE1 enzyme is a key target for Alzheimer’s disease. During our BACE1 research efforts, fragment screening revealed that bicyclic thiazine 3 had low millimolar activity against ...BACE1. Analysis of the co-crystal structure of 3 suggested that potency could be increased through extension toward the S3 pocket and through conformational constraint of the thiazine core. Pursuit of S3-binding groups produced low micromolar inhibitor 6, which informed the S3-design for constrained analogs 7 and 8, themselves prepared via independent, multi-step synthetic routes. Biological characterization of BACE inhibitors 6–8 is described.
Cathepsin S (Cat S) plays an important role in many pathological conditions, including abdominal aortic aneurysm (AAA). Inhibition of Cat S may provide a new treatment for AAA. To date, several ...classes of Cat S inhibitors have been reported, many of which form covalent interactions with the active site Cys25. Herein, we report the discovery of a novel series of noncovalent inhibitors of Cat S through a medium-throughput focused cassette screen and the optimization of the resulting hits. Structure-based optimization efforts led to Cat S inhibitors such as 5 and 9 with greatly improved potency and drug disposition properties. This series of compounds binds to the S2 and S3 subsites without interacting with the active site Cys25. On the basis of in vitro potency, selectivity, and efficacy in a CaCl2-induced AAA in vivo model, 5 (LY3000328) was selected for clinical development.
The development of beta-site amyloid-beta precursor protein cleaving enzyme (BACE) 1 inhibitors for the treatment of Alzheimer's disease requires optimization of inhibitor potency, selectivity, and ...brain penetration. Moreover, there is a need for low-dose compounds since liver toxicity was found with some BACE inhibitors.
To determine whether the high
potency and robust pharmacodynamic effect of the BACE inhibitor LY3202626 observed in nonclinical species translated to humans.
The effect of LY3202626 versus vehicle on amyloid-β (Aβ) levels was evaluated in a series of
assays, as well as in
and multi-part clinical pharmacology studies. Aβ levels were measured using analytical biochemistry assays in brain, plasma, and cerebrospinal fluid (CSF) of mice, dogs and humans. Nonclinical data were analyzed using an ANOVA followed by Tukey's
test and clinical data used summary statistics.
LY3202626 exhibited significant human BACE1 inhibition, with an IC
of 0.615±0.101 nM in a fluorescence resonance energy transfer assay and an EC
of 0.275±0.176 nM for lowering Aβ
and 0.228±0.244 nM for Aβ
in PDAPP neuronal cultures. In dogs, CSF Aβ
concentrations were significantly reduced by ∼80% at 9 hours following a 1.5 mg/kg dose. In humans, CSF Aβ
was reduced by 73.1±7.96 % following administration of 6 mg QD. LY3202626 was found to freely cross the blood-brain barrier in dogs and humans.
LY3202626 is a potent BACE1 inhibitor with high blood-brain barrier permeability. The favorable safety and pharmacokinetic/pharmacodynamic profile of LY3202626 supports further clinical development.
3-(Imidazo1,2-
apyridin-3-yl)-, its aza-analogs, and 3-(pyrazolo1,5-
apyridin-3-yl)-4-(2-acyl-(1,2,3,4-tetrahydro1,4diazepino6,7,1-
hiindol-7-yl))maleimides are very potent inhibitors of GSK3 (⩽5
nM) ...with >160 to >10,000-fold selectivity versus CDK2/4 and PKCβII.
Many 3-aryl-4-(1,2,3,4-tetrahydro1,4diazepino6,7,1-
hiindol-7-yl)maleimides exhibit potent GSK3 inhibitory activity (<100
nM IC
50), although few show significant selectivity (>100
×) versus CDK2, CDK4, or PKCβII. However, combining 3-(imidazo1,2-
apyridin-3-yl), 3-(pyrazolo1,5-
apyridin-3-yl) or aza-analogs with a 4-(2-acyl-(1,2,3,4-tetrahydro1,4diazepino6,7,1-
hiindol-7-yl)) group on the maleimide resulted in very potent inhibitors of GSK3 (⩽5
nM) with >160 to >10,000-fold selectivity versus CDK2/4 and PKCβII. These compounds also inhibited tau phosphorylation in cells and were effective in lowering plasma glucose in a rat model of type 2 diabetes (ZDF rat).
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