PDGFRB and neoplasm: A notable exception is fatigue with incidence that appears higher than sorafenib (all grades: 25%; grade 3–4: 4%) or lenvatinib (any grade 30%; grade 3–4: 4%).21 This can be potentially attributable to the individual drug on-target/off-tumour activity and/or different potencies against different cellular kinases as tivozanib has an anti-VEGFR-2 activity in vitro that is 187 times higher compared to sorafenib and 32 times higher compared to lenvatinib; its activity against PDGFRβ is 46 and 197 times higher compared to sorafenib and lenvatinib, respectively.12,26,27