Background: ASP3026 (3026) is a selective, potent, ATP-competitive, small molecule oral inhibitor of ALK receptor tyrosine kinase that has not previously been tested in humans. A Phase 1 dose-escalation trial, using a 3+3 design, evaluating 3026 as an oral single agent was conducted to investigate PK (Day 1 and Day 28), safety and clinical activity in patients (pts) with advanced malignancies (excluding leukemias) of ECOG PS 2 or less. Methods: 3026 was administered under fasting conditions on a continuous schedule to pts in successive dose-escalating cohorts at doses ranging from 25 mg QD to 800 mg QD. Results: Thirty pts were enrolled into the dose escalation part of the study. The MTD was determined based on DLT data from cycle 1. Three DLTs were observed: grade 2 nausea and vomiting leading to dose reduction at 525 mg QD; grade 3 rash leading to dose reduction, and grade 3 ALT/AST increase leading to study withdrawal at 800 mg QD. The most common AEs were constipation, vomiting, diarrhea, nausea and abdominal pain, and all AEs were manageable and reversible. Median AUC and Cmax increased proportionally with dose from 25 mg QD to 800 mg QD. There was no evidence of non-linear PK at ASP3026 doses >25 mg QD. The median terminal half-life was approximately 10 - 41 hours. Overall, A3026 appears well absorbed with median Tmax around 3 hours for both Day 1 and Day 28. Terminal T_1/2 appears adequate for one daily dosing with median values ranging from approximately 18 to 34 hours. Based on visual inspection of pre-dose (trough) values from Days 8, 15, 22, and 28 it appears that steady-state conditions are achieved by day 28. Conclusions: The MTD of 3026 is 525 mg QD. Treatment with 3026 resulted in a promising safety and PK profile in pts with advanced malignancies. Further evaluation of 3026 in pts with tumors harboring gene mutation or ALK fusion genes in the cohort expansion phase at the MTD is ongoing. Clinical trial information: NCT01401504.