Background. The A3 adenosine receptor (A3AR) is overexpressed in thetumorandin the peripheral bloodmononuclear cells of patients with hepatocellular carcinoma (HCC). The orally active drug candidate CF102, an A3AR agonist, induces apoptosis of HCC cells via deregulation of the Wnt signaling pathway. In this open label phase I/II trial, the safety and clinical effects of CF102 were assessed in patients with advanced unresectable HCC. Methods. The primary objectives of this trial were to examine the safety and pharmacokinetic (PK) behavior of CF102 given orally (1, 5,and25mgBID) in 28-day cycles. Evaluation of anti-tumor effects and the utilization of A3AR as a biological predictive marker of response to CF102 were the secondary objectives. Results. Eighteen patients received CF102-six at each dose level. No serious drug-related adverse events or doselimiting toxicities were observed. CF102 demonstrated good oral bioavailability and linear PK behavior. Median overall survival in the study population, 67% of whom had received prior sorafenib, was 7.8 months, and for Child Pugh B patients (28%) it was 8.1 months. Stable disease by RECIST was observed in four patients for at least 4 months. CF102 maintained liver function over a 6-month period. A correlation between receptor overexpression levels at baseline and patients' overall survival was found. One of the patients who presented with skin nodules that were biopsy- proven to be HCC metastases prior to the trial showed complete metastasis regression during three months of treatment with CF102. Conclusions. CF102 is safe and well-tolerated, showing favorable PK characteristics in Child Pugh A and B HCC patients, justifying further clinical development.