- Rigidification Dramatically Improves Inhibitor Selectivity for RAF Kinases
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One effective means to achieve inhibitor specificity for RAF kinases, an important family of cancer drug targets, has been to target the monomeric inactive state conformation of the kinase domain, which, unlike most other kinases, can accommodate sulfonamide-containing drugs such as vemurafenib and dabrafenib because of the presence of a unique pocket specific to inactive RAF kinases. We previously reported an alternate strategy whereby rigidification of a nonselective pyrazolo[3,4-d]pyrimidine-based inhibitor through ring closure afforded moderate but appreciable increases in selectivity for RAF kinases. Here, we show that a further application of the rigidification strategy to a different pyrazolopyrimidine-based scaffold dramatically improved selectivity for RAF kinases. Crystal structure analysis confirmed our inhibitor design hypothesis revealing that 2l engages an active-like state conformation of BRAF normally associated with poorly discriminating inhibitors. When screened against a panel of distinct cancer cell lines, the optimized inhibitor 2l primarily inhibited the proliferation of the expected BRAFV600E-harboring cell lines consistent with its kinome selectivity profile. These results suggest that rigidification could be a general and powerful strategy for enhancing inhibitor selectivity against protein kinases, which may open up therapeutic opportunities not afforded by other approaches.
- Assadieskandar, Amir,Yu, Caiqun,Maisonneuve, Pierre,Kurinov, Igor,Sicheri, Frank,Zhang, Chao
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- NITROGEN-CONTAINING BICYCLIC HETEROARYL COMPOUNDS AND METHODS OF USE
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The present invention comprises a new class of compounds capable of modulating Raf kinase and, accordingly, useful for treatment of Raf kinase mediated diseases, including melanomas, tumors and other cancer-related conditions. The compounds have Formula (I) wherein R1 is Formula (II), (III) or (IV) and A1, A2, A3, A4, X, Z, Z', R1, R2, R3, R4, R5 and R6 are defined herein. The invention further comprises pharmaceutical compositions, methods for treatment of Raf kinase mediated diseases, and intermediates and processes useful for the preparation of compounds of the invention.
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Page/Page column 121
(2008/06/13)
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