Tat-braftide is a BRAF kinase inhibitor consisting of the10-mer peptide inhibitor, braftide, TRHVNILLFM, linked by PEG to the cell penetrating sequence TAT. Tat-braftide was designed to bind to the dimer interface of the BRAF kinase domain, and accordingly it inhibits BRAF kinase activity by disrupting BRAF dimers, with an IC50 of 43 nM in kinase assays. Additionally, targeting the dimer interface of BRAF kinase leads to protein degradation of both RAF and MEK, uncovering a novel scaffolding function of RAF in protecting large MAPK complexes from protein degradation. Tat-braftide shows efficient inhibition and degradation of WT BRAF and BRAFG469A in a variety of cells exhibiting either RAS dependence or independence. Tatbraftide treatment causes dose dependent inhibition of growth of HCT116 and HCT-15 cells, with EC50 values of 7.1 and 6.6 µM, demonstrating potent inhibiton of cell viability in KRAS-mutated colon cancer cells.
