Abstract
9020 Background: TKI258 (dovitinib lactate), is a multi-tyrosine kinase inhibitor of VEGF receptors-1,2,3, FGF receptors-1, 2, 3, PDGFR-β, and c-KIT. A phase I study was conducted to determine the maximum tolerated dose (MTD), the biological activity and the preliminary efficacy of TKI258 in patients with advanced melanoma. A panel of plasma biomarkers of angiogenesis and soluble receptors were evaluated to determine the pharmacodynamic effect of TKI258. Methods: Patients were treated orally with 200, 300, 400 or 500 mg/day on a once daily continuous dose schedule. The MTD was defined at 400 mg/day. Plasma samples from 43 patients were collected. Plasma concentration of TKI258 was measured by LC/MS/MS. Plasma VEGF, placental growth factor (PLGF), basic FGF (bFGF), and soluble VEGFR1 and VEGFR2 (sVEGFR1 and 2), and c-Kit were measured by multiplex assays using the Meso-Scale Discovery platform. Plasma FGF23 was evaluated by ELISA as a pharmcodynamic marker of FGFR1 inhibition. Results: Following 400 mg or 500 mg continuous daily dosing, the mean plasma exposure (AUC24hr) was approximately 3000 ng/mL*h and 4100 ng/mL*h, respectively. No accumulation in TKI258 plasma exposure was observed at doses of 400mg or below, while accumulation up to 2.5-fold was observed on day 15 following the 500 mg daily dose. At the end of the first treatment cycle, mean plasma VEGF, PLGF and FGF23 levels increased over baseline by 100%, 198% and 68%, respectively, while mean plasma sVEGFR2 levels decreased by 15% in patients treated with 400 and 500 mg/day TKI258. Further analysis of correlations with pharmacokinetic and clinical parameters is ongoing. Conclusions: TKI258 therapy is associated with increases of plasma VEGF and PLGF as well as decreases of sVEGFR2 suggesting VEGFR inhibition. Induction of plasma FGF23 suggest that FGFR may be inhibited at doses of 400 mg/day and above. This panel of circulating proteins may have utility as pharmacodynamic biomarkers of TKI258 activity in patients with advanced melanoma. [Table: see text]
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