BGB-283: Small Molecule RAF Dimer Inhibitor to Treat Solid Tumors

BGB-283 is a novel inhibitor of RAF, in both monomeric and dimeric forms. BGB-283 has demonstrated potent and reversible inhibitory activities against RAF family kinases, including wild-type ARAF, BRAF, CRAF and BRAF V600E, in biochemical assays. In addition, BGB-283 has shown potent inhibitory activity against EGFR in biochemical assays using EGFR kinases, cancer cell lines, and xenograft models. In BRAF wild-type cells that harbor the KRAS mutations, treatment with BGB-283 resulted in much reduced up-regulation of pERK, a phosphorylated form of ERK, compared with vemurafenib in cancer cell models.

In preclinical testing, BGB-283 also retained inhibitory activity in vemurafenib-Scientistresistant BRAF splicing isoform p61-BRAF V600E. Data generated in preclinical studies using biochemical, cell-based and animal studies suggest that BGB-283 could offer significant patient benefit in inhibiting tumors with aberrations in the RAF MAPK/ERK pathway, including BRAF mutations and KRAS/NRAS mutations as either monotherapy or in combination with other cancer therapies.

We believe BGB-283 has the potential to be differentiated from other drug candidates currently under development and from approved first-generation BRAF inhibitors due to the following:

  • Increased inhibitory activity against RAF dimers – BGB-283’s increased inhibitory activity against RAF dimers may potentially address resistances associated with increased RAF dimer formation in response to treatment with first-generation BRAF inhibitors.
  • Increased activity in KRAS/NRAS mutated cancers – We believe that BGB-283’s RAF dimer activity could translate into anti-tumor activity in KRAS/NRAS mutated cancers. Anti-tumor activities were observed in preclinical KRAS/NRAS mutant cancer models in vivo.
  • Increased inhibitory activity against EGFR – BGB-283 has demonstrated inhibitory activity against EGFR. The reported response rate of vemurafenib in BRAF V600E colorectal cancer is only 5%. Two independent studies suggested that EGFR feedback activation could be one of the main mechanisms of the observed resistance to first-generation BRAF inhibitors. BGB-283 has demonstrated good EGFR inhibitory activity in both in vitro and in vivo preclinical models. BGB-283’s activity against EGFR may help address the EGFR feedback activation observed in BRAF V600E colorectal cancer tumors.
  • Differentiated resistance profile – BGB-283 has shown inhibitory activity against RAF dimers. An increase in RAF dimers has been observed to be a major resistance mechanism to first generation BRAF inhibitors.

 

Mechanism of Action

BGB-283