Developments on BACE 1 Inhibitors as Anti-Alzheimer Agents: A Perspective on Medicinal Chemistry-Based Advances

Alzheimer's disease (AD) is a progressive and complicated neurodegenerative disorder that mostly affects the elderly and is characterized by memory loss, cognitive dysfunction, accumulation of amyloid beta (Aβ) plaques, neurofibrillary tangles, and cholinergic deficits. Current therapies used for AD, such as acetylcholinesterase inhibitors and NMDA receptor antagonist memantine, can only provide temporary or symptomatic relief, but they do not stop or reverse the progression of the disease. Numerous pathogenic hypotheses have been proposed to explain this mechanism; however, the amyloid cascade hypothesis remains the most widely accepted theory, as it suggests that β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) plays a critical role in the generation of Aβ peptides. Therefore, BACE1 may be a key therapeutic target. This review primarily focuses on the key role of BACE1 in AD pathogenesis and describes the development of its inhibitors over three generations, explaining their structure, design, and pharmacological properties. While the first generation lacked brain penetration, the second-generation improved potency but encountered clinical trial failures due to adverse effects. The third generation of these drugs was designed to achieve a balance between efficacy, selectivity, and safety. Additionally, we review the promising molecules currently under clinical investigation, highlighting both their therapeutic potential and the challenges that remain in developing effective disease-modifying therapies for AD treatment.