Background: Tanibirumab is a fully human monoclonal antibody to the vascular endothelial growth factor receptor 2 (VEGFR-2). We conducted a first-in-human phase I study of Tanibirumab in patients with solid tumors which were refractory to standard chemotherapy. Primary endpoints are evaluating safety, pharmacokinetics (PKs), estimating maximum-tolerated dose (MTD) and recommended phase II dose (RP2D). Methods: We designed to escalate Tanibirumab at 9 different dose levels with 3+3 method and Tanibirumab (1-28mg/kg) was administered intravenously on D1, 8, 15 in 28-day courses. Dose limiting toxicities (DLTs) were assessed in only first cycle of treatment and response evaluation was performed every 2 cycles. The effects of Tanibirumab on serum VEGF, soluble VEGFR-2, PlGF and correlation between VEGF, VEGFR-2 expression in archival tumor tissue and efficacy were planned. Results: From October 2011 to September 2013, a total of 26 patients with refractory solid tumors were enrolled. The median age was 58 years (range, 27-75) and 20 patients were male. Most common tumor type was colorectal cancer (N = 18) and 7 patients had history of previous bevacizumab treatment. As hemangioma continued to occur, last dose level, 28m/kg was not performed. DLTs were not found, and MTD was confirmed as 24mg/kg. Hemangioma was observed in 50% of patients, but most of those were grade 1-2 which disappeared after discontinuation of study drug. Among 18 patients of efficacy set, no objective response was observed, but 11 patients showed stable disease. PKs were characterized by dose-dependent linear exposure and mean trough concentrations exceeded biologically relevant target levels at 12mg/kg and above. Serum VEGF, soluble VEGFR-2, PlGF increased at 4mg/kg dose level and above. Conclusions: Treatment with Tanibirumab showed tolerable toxicity profile and modest clinical efficacy in patients with refractory solid tumors. We have a plan to conduct phase II trial in patients with glioma. Clinical trial information: NCT01660360