An updated patent review of protein arginine N-methyltransferase inhibitors (2019–2022)

Protein arginine methyltransferases (PRMTs), enzymes catalyzing the methylation of target proteins, play an essential role in maintaining functional homeostasis in normal physiology. Aberrant expressions and enhanced enzymatic activities of PRMTs have been closely associated with pathological states such as cancer, inflammatory, immune, metabolic, and neurodegenerative diseases. Therefore, the development of inhibitors targeting PRMTs has attracted a great deal of attention in both pharmaceutical industries and academic community. This review focuses on the small-molecule inhibitors targeting PRMTs in cancer therapy in the patents published since 2019. The recent clinical development is also discussed here. In recent years, the discovery of small-molecule PRMT inhibitors, especially PRMT5 inhibitors has become a rapidly expanding research area for cancer therapy. Although a number of potent PRMT inhibitors with different chemical scaffolds have been developed and nine of them have entered into clinical trials, their scaffolds are relatively less diverse. Sub-type selectivity should be considered in drug discovery as nonselective inhibition of PRMTs may cause undesirable pharmacological effects. Hence, the development of new effective inhibitors with isoform-specific and tumor-biased distributions remains an important area for further studies.