Open AccessDiscovery of a First-in-Class Inhibitor of the PRMT5–Substrate Adaptor Interaction
Author(s) -
David C. McKinney,
Brian J. McMillan,
Matthew J. Ranaghan,
Jamie A. Moroco,
Merissa Brousseau,
Zachary Mullin-Bernstein,
Meghan O’Keefe,
Patrick McCarren,
Michael F. Mesleh,
Kathleen M. Mulvaney,
Foxy Robinson,
Ritu Singh,
Besnik Bajrami,
Florence F. Wagner,
Robert Hilgraf,
Martin J. Drysdale,
Arthur J. Campbell,
Adam Skepner,
David E. Timm,
Dale Porter,
Virendar K. Kaushik,
William R. Sellers,
Alessandra Ianari
Publication year - 2021
Publication title -
journal of medicinal chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.01
H-Index - 261
eISSN - 1520-4804
pISSN - 0022-2623
DOI - 10.1021/acs.jmedchem.1c00507
Subject(s) - chemistry , protein arginine methyltransferase 5 , spliceosome , signal transducing adaptor protein , methylation , cysteine , small molecule , methyltransferase , binding site , covalent bond , biochemistry , stereochemistry , enzyme , signal transduction , dna , rna splicing , rna , organic chemistry , gene
PRMT5 and its substrate adaptor proteins (SAPs), pICln and Riok1, are synthetic lethal dependencies in MTAP-deleted cancer cells. SAPs share a conserved PRMT5 binding motif (PBM) which mediates binding to a surface of PRMT5 distal to the catalytic site. This interaction is required for methylation of several PRMT5 substrates, including histone and spliceosome complexes. We screened for small molecule inhibitors of the PRMT5-PBM interaction and validated a compound series which binds to the PRMT5-PBM interface and directly inhibits binding of SAPs. Mode of action studies revealed the formation of a covalent bond between a halogenated pyridazinone group and cysteine 278 of PRMT5. Optimization of the starting hit produced a lead compound, BRD0639, which engages the target in cells, disrupts PRMT5-RIOK1 complexes, and reduces substrate methylation. BRD0639 is a first-in-class PBM-competitive inhibitor that can support studies of PBM-dependent PRMT5 activities and the development of novel PRMT5 inhibitors that selectively target these functions.