2018 Background: NK105 is a new polymeric micelle carrier system for paclitaxel (PTX). A preclinical study revealed that the plasma AUC and tumor AUC of NK105 were 90-fold higher and 25-fold higher, respectively, than those of free-PTX, i.e., the conventional PTX formulation. NK105 had higher in vivo antitumor activity and lower neurotoxicity than free-PTX. This phase I study was designed to examine the MTD, DLTs, recommended dose (RD) for phase II, and the pharmacokinetics of NK105. Methods: NK105 was administered as a 1-hour intravenous infusion every 3 weeks, without antiallergic premedication. The starting dose was 10 mg PTX equivalent/m2, and the dose was escalated according to the accelerated titration method. Results: To date, 17 patients (pts) have received the following doses: 10 mg/m2 (n=1); 20 mg/m2 (n=1); 40 mg/m2 (n=1); 80 mg/m2 (n=1); 110 mg/m2 (n=3); 150 mg/m2 (n=5); and 180 mg/m2 (n=5). The tumor types treated included pancreatic (n=9), bile duct (n=5), gastric (n=2), and colonic (n=1) cancers. Neutropenia was the most common hematological toxicity. Grade 3 fever developed in 1 pt given 180 mg/m2. No other grade 3 or 4 non-hematological toxicity, including neuropathy, was observed. DLTs occurred in pts given 180 mg/m2 (grade 4 neutropenia lasting for more than 5 days). This dose was designated as the MTD. Allergic reactions developed in only one pt at 180 mg/m2, who was sensitive to other drugs such as antibiotics anti-inflammatory. A partial response was observed in one pt with pancreatic cancer and pts with colonic and gastric cancer had stable disease. The Cmax and AUC of NK105 were dose dependent. The plasma AUC of NK105 at 180 mg/m2 was approximately 30-fold higher than that of the conventional formulation of PTX. Conclusions: Accrual is ongoing at the 150 mg/m2 dose level to determine the RD. DLT was Grade 4 neutropenia. NK105 produces prolonged high levels of PTX in plasma. A 1-hour infusion of NK105 every 3 weeks was feasible, well tolerated, and effective in patients with pancreatic cancer. Even after the long term usage, only grade 1 or 2 neuropathy was observed. NK105 will be evaluated in Phase II studies of patients with advanced pancreatic and gastric cancers. No significant financial relationships to disclose.