Purinylpyridinylamino-based DFG-in/αC-helix-out B-Raf inhibitors: Applying mutant versus wild-type B-Raf selectivity indices for compound profiling

  • Bioorg Med Chem. 2016 May 15;24(10):2215-34. doi: 10.1016/j.bmc.2016.03.055.
Longbin Liu  1 ,  Matthew R Lee  2 ,  Joseph L Kim  3 ,  Douglas A Whittington  3 ,  Howard Bregman  4 ,  Zihao Hua  4 ,  Richard T Lewis  4 ,  Matthew W Martin  4 ,  Nobuko Nishimura  5 ,  Michele Potashman  4 ,  Kevin Yang  5 ,  Shuyan Yi  4 ,  Karina R Vaida  4 ,  Linda F Epstein  3 ,  Carol Babij  6 ,  Manory Fernando  6 ,  Josette Carnahan  6 ,  Mark H Norman  5
Affiliations
  • 1. Department of Medicinal Chemistry, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA. Electronic address: [email protected].
  • 2. Department of Molecular Structure and Characterization, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA.
  • 3. Department of Molecular Structure and Characterization, Amgen Inc., 360 Binney St., Cambridge, MA 02142, USA.
  • 4. Department of Medicinal Chemistry, Amgen Inc., 360 Binney St., Cambridge, MA 02142, USA.
  • 5. Department of Medicinal Chemistry, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA.
  • 6. Department of Oncology Research, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA.
PMID: 27085672 DOI: 10.1016/j.bmc.2016.03.055
Abstract

One of the challenges for targeting B-Raf(V600E) with small molecule inhibitors had been achieving adequate selectivity over the wild-type protein B-Raf(WT), as inhibition of the latter has been associated with hyperplasia in normal tissues. Recent studies suggest that B-Raf inhibitors inducing the 'DFG-in/αC-helix-out' conformation (Type IIB) likely will exhibit improved selectivity for B-Raf(V600E). To explore this hypothesis, we transformed Type IIA inhibitor (1) into a series of Type IIB inhibitors (sulfonamides and sulfamides 4-6) and examined the SAR. Three selectivity indices were introduced to facilitate the analyses: the B-Raf(V600E)/B-Raf(WT) biochemical ((b)S), cellular ((c)S) selectivity, and the phospho-ERK activation ((p)A). Our data indicates that α-branched sulfonamides and sulfamides show higher selectivities than the linear derivatives. We rationalized this finding based on analysis of structural information from the literature and provided evidence for a monomeric B-Raf-inhibitor complex previously hypothesized to be responsible for the desired B-Raf(V600E) selectivity.

Keywords
B-Raf; C-helix; DFG; Inhibitor; Selectivity; Sulfonamide; Wild-type; v600e.