NTRK1 and neuroblastoma: 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.