Rational design, synthesis, and biological evaluation of Pan-Raf inhibitors to overcome resistance
Selective BRafV600E inhibitors with DFG-in conformation have been proven effective against a subset of melanoma. However, representative inhibitor vemurafenib rapidly acquire resistance in the BRafWT cells through a CRaf or BRafWT dependent manner. Simutaneous targeting all subtypes of Raf proteins offer the prospect of enhanced efficacy as well as reduced potential for acquired resistance. Described herein is the design and characterization of a series of compounds I-01~I-22 which based on pyrimidine scaffold with DFG-out conformation as Pan-Raf inhibitors. Among them, I-15 binds to all Raf protomers with IC50 values of 12.6 nM (BRafV600E), 30.1 nM (ARaf), 19.7 nM (BRafWT) and 17.5 nM (CRaf), respectively, demonstrates cellular activity against BRafWT phenotypic melanoma and BRafV600E phenotypic colorectal cancer cells. The western blot results for the P-Erk inhibition in human melanoma SK-Mel-2 cell line showed I-15 inhibited the proliferation of SK-Mel-2 cell line at concentration as low as 400 nM, without paradoxical activation of Erk as vemurafenib, which supported I-15 may become a good candidate compound to overcome the resistance of melanoma induced by vemurafenib. I-15 also have a favorable pharmacokinetic profile in rat. Rational design, synthesis, SAR, lead selection and evaluation of the key compounds studies are described.