Description: IC50: ~10 nmol/L for FGFR1–3 Fibroblast growth factor receptor 1 (FGFR1) and FGFR2 amplifications are observed in approximately 10% of breast cancers and are related to poor outcomes. Dovitinib (TKI258) is an oral tyrosine kinase inhibitor (TKI) against FGFR1–3, VEGFR1–3, and platelet-derived growth factor receptor (PDGFR). In vitro: Dovitinib decreased the concentrations of pFRS2 and pERK/MAPK in a dose-dependent manner in FGFR1 amplified and FGFR2 amplified cell lines. The IC50 for cell growth inhibition was 190 and 180 nmol/L in MDA-MB-134 and SUM52, respectively. Conversely, IC50 values were more than 2,000 nmol/L in the 11 breast cancer cell lines that had neither FGFR1 nor FGFR2 amplification . In vivo: In vivo model (HBCx-2 breast cancer primary xenograft, with 8 FGFR1 gene copies), dovitinib prevented tumor growth at the 30 mg/kg dose and caused tumor regression at the 50 mg/kg dose. Similarly, dovitinib caused tumor regression in HBCx-3 xenografts when administered at a dose of 40 mg/kg daily until day 35 . Clinical trial: Eighty-one patients were enrolled in the trial. Unconfirmed response or stable disease for over 6 months was observed in 5 and 1 patient(s) with FGFR1-amplified/HR-positive and FGFR1-nonamplified/HR-positive breast cancer. When qPCR-identified amplifications in FGFR1, FGFR2, or FGF3 were grouped to define an FGF pathway–amplified breast cancer in HR-positive patients, the mean reduction in target lesions was 21.1% compared with a 12.0% increase in patients that did not present with FGF pathway–amplified breast cancer .