Regorafenib has been demonstrated to inhibit multiple kinases, including the RET, VEGFR1–3, c-Kit, TIE-2, PDGFRβ, FGFR1, RAF1, BRAF and p38 MAPK kinases.21 To determine whether the efficacy of regorafenib was a result of inhibition of cell surface receptor kinases, we evaluated neuroblastoma cells after regorafenib treatment for inhibition of known receptor tyrosine kinase targets. This evidence concerns the gene FLT1 and neuroblastoma.