Regorafenib

Regorafenib strongly prevents VEGFR2 autophosphorylation in NIH-3T3/VEGFR2 cells with IC50 of 3 nM. In HAoSMCs, regorafenib suppresses PDGFR-β autophosphorylation after stimulation with PDGF-BB, with an IC50 of 90 nM. Regorafenib also inhibits FGFR signaling in MCF-7 breast cancer (BC) cells stimulated with FGF10. Regorafenib very potently inhibited the mutant receptors KIT^K642E and RET^C634W, with IC50 of approximately 20 nM and 10 nM, respectively. Regorafenib inhibits the proliferation of VEGF¹⁶⁵-stimulated HUVECs, with an IC50 of approximately 3 nM. Regorafenib prevents the proliferation of FGF2-stimulated HUVECs and of PDGF-BB-stimulated HAoSMCs with IC50 of 127 nM and 146 nM, respectively. ^[1] Regorafenib targets both tumor cell proliferation and tumor vasculature through inhibition of receptors of tyrosine kinases (VEGFR, KIT, RET, FGFR, and PDGFR) and serine/threonine kinases (Raf and p38MAPK). ^[2] Regorafenib suppresses growth of human Hep3B, PLC/PRF/5 and HepG2 cells in a concentration- and time-dependent manner. ^[3]

Regorafenib reveals potent dose-dependent TGI in various preclinical human xenograft models in mice, with tumor shrinkages in breast MDA-MB-231 and renal 786-O carcinoma models. Regorafenib prevents not only the growth of syngeneic primary 4T1 breast tumors growing orthotopically in the fat pad, but also suppresses the formation of tumor metastasis in the lung. ^[1]

• Kinase assays

  In vitro assays using recombinant VEGFR2 (murine aa785–aa1367), VEGFR3 (murine aa818–aa1363), PDGFRβ (aa561–aa1106), Raf-1 (aa305–aa648) and BRafV600E (aa409–aa765) kinase domains are performed. Initial in vitro kinase inhibition profiling is performed at a fixed 1 μM Regorafenib concentration. Inhibitory concentration of 50% (IC50) values are determined from selected responding kinases, e.g., VEGFR1 and RET. TIE2 kinase inhibition is measured with a homogeneous time-resolved fluorescence (HTRF) assay using a recombinant fusion protein of glutathione-S-transferase, the intracellular domain of TIE2 and the peptide biotin-Ahx-EPKDDAYPLYSDFG as substrate.

• Cell lines

  GIST 882 and TT cells

• Concentrations

  5 nM-10 μM

• Incubation Time

  96 hours

• Method

  For proliferation assays, GIST 882 and TT cells are grown in RPMI medium containing L-glutamine, and MDA-MB-231, HepG2 and A375 cells in DMEM always containing 10% hiFBS. Cells are trypsinized, plated at 5×10⁴ cells/well in 96-well plates in complete media containing 10% FBS and grown overnight at 37 °C. The next day, vehicle or Regorafenib serially diluted in complete growth media to between 10 μM and 5 nM final concentrations, and 0.2% DMSO, is added and incubation is continued for 96 hours. Cell proliferation is quantified.

• Animal Models

  Female athymic NCr nu/nu mice with Colo-205, MDA-MB-231 or 786-O

• Dosages

  3 mg/kg, 10 mg/kg, 30 mg/kg, 100 mg/kg

• Administration

  Orally