Synthesis, Optimization, and Large-Scale Preparation of the Low-Dose Central Nervous System-Penetrant BACE1 Inhibitor LY3202626 via a [3 + 2] Nitrone Cycloaddition

Discovery and Early Clinical Development of LY3202626, a Low-Dose, CNS-Penetrant BACE Inhibitor

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.

Small-molecule BACE1 inhibitors: a patent literature review (2011 to 2020)

INTRODUCTION

Inhibition of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) has been extensively pursued as potential disease-modifying treatment for Alzheimer's disease (AD). Clinical failures with BACE inhibitors have progressively raised the bar forever cleaner candidates with reduced cardiovascular liability, toxicity risk, and increased selectivity over cathepsin D (CatD) and BACE2.

AREAS COVERED

This review provides an overview of patented BACE1 inhibitors between 2011 and 2020 per pharmaceutical company or research group and highlights the progress that was made in dialing out toxicity liabilities.

EXPERT OPINION

Despite an increasingly crowded IP situation, significant progress was made using highly complex chemistry in avoiding toxicity liabilities, with BACE1/BACE2 selectivity being the most remarkable achievement. However, clinical trial data suggest on-target toxicity is likely a contributing factor, which implies the only potential future of BACE1 inhibitors lies in careful titration of highly selective compounds in early populations where the amyloid burden is still minimal as prophylactic therapy, or as an affordable oral maintenance therapy following amyloid-clearing therapies.