Background: AR-12 (OSU-03012) is an oral celecoxib analogue lacking COX-2 inhibitory activity that inhibits pyruvate dehydrogenase kinase isoenzyme 1 (PDK-1), AKT and impacts the endoplastic reticulum stress pathway. Preclinical studies indicate antitumor activity of AR-12 in various models and enhanced activity in combination. We completed a first in human clinical trial to determine its safety and tolerability, maximum tolerated dose (MTD) and recommended phase II dose (RD). Secondary objectives included assessment of tumor response, pharmacokinetics (PK) and pharmacodynamics (PD) including food effect. Methods: Patients (pts) with advanced solid tumors, ECOG PS 0-1, and adequate organ function were recruited in a modified 3+3 dose-escalation study. Pts received a run-in dose of AR-12 to analyze PK-PD and food effect, followed by continuous daily (QD) dosing in 28-day cycles. A twice daily (BID) cohort was initiated based on safety data. PD analysis was performed in platelet-rich plasma (PRP) and paired tumor biopsies when feasible. Results: 35 pts received at least one dose of study drug; 30 were evaluable for dose limiting toxicities (DLT) at dose ranges 100-3200mg QD and 800-1600mg BID. No DLT were observed in the QD cohort; DLT in the BID cohort are listed in table 1. Drug-related events (NCI-CTCAE v3) included rash (G2-2pts; G3-1pt), fatigue (G2-2pts; G3-4pts), nausea (G2-7pts; G3-1pt) and bloating (G2-1pt). Cmax after single dose was dose-proportional but high PK variability was observed, likely due to inadequate disintegration and dissolution of the formulation in the stomach. At RD, partial GSK3ß inhibition in PRP after 4 hours suggests AKT-pathway modulation. Best response (RECIST v1.0) was stable disease >6 cycles for 2 pts. Conclusions: The RD based on safety data is 800mg BID. Signs of pathway modulation were observed in concordance with the expected mechanism of action but were short-lasting. Considering limited drug absorption and PK variability, a new formulation of the drug will be developed to overcome these limitations. Clinical trial information: NCT00978523.