Discovery of First-in-Class Protein Arginine Methyltransferase 5 (PRMT5) Degraders

The
aberrant expression of protein arginine methyltransferase 5
(PRMT5) has been associated with multiple cancers. Using the proteolysis
targeting chimera technology, we discovered a first-in-class PRMT5
degrader 15 (MS4322). Here, we report the design, synthesis,
and characterization of compound 15 and two structurally
similar controls 17 (MS4370) and 21 (MS4369),
with impaired binding to the von Hippel-Lindau E3 ligase and PRMT5,
respectively. Compound 15, but not 17 and 21, effectively reduced the PRMT5 protein level in MCF-7 cells.
Our mechanism studies indicate that compound 15 degraded
PRMT5 in an E3 ligase- and proteasome-dependent manner. Compound 15 also effectively reduced the PRMT5 protein level and inhibited
growth in multiple cancer cell lines. Moreover, compound 15 was highly selective for PRMT5 in a global proteomic study and exhibited
good plasma exposure in mice. Collectively, compound 15 and its two controls 17 and 21 are valuable
chemical tools for exploring the PRMT5 functions in health and disease.