RAF1 and melanoma: Combining XL888 (Exelixis), a non-benzoquinone ATP-competitive inhibitor of HSP90, with targeted inhibitors of the RAS/RAF/MEK/ERK (MAPK) signaling pathway (XL888 + vemurafenib, and XL888 + vemurafenib + cobimetinib) is currently evaluated in phase I clinical trials in patients with unresectable melanoma (clinicaltrials.gov).