Proteolytic therapeutic modalities for amyloidoses: Insights into immunotherapy, PROTAC, and photo-oxygenation

Amyloidoses, which are characterized by abnormal accumulation of amyloid proteins leading to organ dysfunction, represent a major therapeutic challenge. They include neurodegenerative diseases, such as Alzheimer disease (AD), tauopathies and synucleinopathies. Since amyloids are causative factors in these diseases, the importance of proteolytic methods to remove amyloid, such as immunotherapy and Proteolysis Targeting Chimera (PROTAC) technology, has been recognized. Immunotherapy removes target proteins by antibody-mediated reactions and is the most studied method in practical use for the treatment of AD. PROTAC is a small molecule that uses the ubiquitin-proteasome system to degrade intracellular target proteins and has demonstrated efficacy in clinical trials for other diseases. In addition, a new modality called photo-oxygenation has been developed. Photo-oxygenation is a method of selectively adding oxygen to amyloid using a photocatalyst, which is a small molecule compound that is activated by light. Studies both in vitro and in vivo have shown promising results in inhibiting amyloid aggregation and enhancing the clearance of amyloid proteins. In this review, we introduce and discuss these proteolytic modalities, and provide insights into potential future directions for the clinical application in amyloidoses.