Development of a potent small-molecule degrader against oncogenic BRAFV600E protein that evades paradoxical MAPK activation.

Abstract

BRAF mutations are frequently observed in melanoma and hairy-cell leukemia. Currently approved rapidly accelerated fibrosarcoma (RAF) kinase inhibitors targeting oncogenic BRAF V600 mutations have shown remarkable efficacy in the clinic, but their therapeutic benefits are occasionally hampered by acquired resistance due to RAF dimerization-dependent reactivation of the downstream MAPK pathway, which is known as paradoxical activation. There is also a concern that paradoxical activation of the MAPK pathway may trigger secondary cancer progression. In this study, we developed chimeric compounds, proteolysis targeting chimeras (PROTACs), that target BRAFV600E protein for degradation. CRBN(BRAF)-24, the most effective chimera, potently degraded BRAFV600E in a ubiquitin-proteasome system (UPS)-dependent manner and inhibited the proliferation of BRAFV600E -driven cancer cells. In BRAF wild-type cells, CRBN(BRAF)-24 induced neither BRAFWT degradation nor paradoxical activation of the MAPK pathway. Biochemical analysis revealed that CRBN(BRAF)-24 showed more potent and sustained suppression of MAPK signaling than a BRAFV600E inhibitor, PLX-8394, in BRAFV600E -driven cancer cells. Targeted degradation of BRAFV600E by CRBN(BRAF)-24 could be a promising strategy to evade paradoxical activation of the RAF-MAPK pathway.

• Authors: Nobumichi Ohoka, Masanori Suzuki, Takuya Uchida, Yoshinori Tsukumo, Masayuki Yoshida, Takao Inoue, Hitoshi Ohki, Mikihiko Naito
• Journal: Cancer science (Cancer Sci) Vol. 113 Issue 8 Pg. 2828-2838 (Aug 2022) ISSN: 1349-7006 [Electronic] England
• PMID: 35579105 (Publication Type: Journal Article)
• Copyright: © 2022 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

Chemical References

• Protein Kinase Inhibitors
• BRAF protein, human
• Proto-Oncogene Proteins B-raf

Topics

• Cell Line, Tumor
• Humans
• MAP Kinase Signaling System
• Melanoma (drug therapy, genetics)
• Mutation
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins B-raf (antagonists & inhibitors, metabolism)