The purpose of this study is to determine whether activation of a prodrug after intratumoral gene transfer is safe in humans, and to determine dose levels for further clinical development.

The study is a phase I clinical trial evaluating the intratumoral injection of defective adenovirus containing HSVtk (the thymidine kinase of herpes simplex virus), in patients with advanced hepatocellular carcinoma that were not amenable to curative therapy. The study was conducted in a single center in Spain. Five consecutive cohorts of two patients received increasing doses of the vector by intratumoral injection and equal doses of either intravenous ganciclovir or oral valganciclovir. The dose received by each consecutive cohort of patients was progressively higher according to a prefixed scale.

Inclusion Criteria:

• Unequivocal diagnosis of hepatocellular carcinoma according to histological confirmation or EASL-AASLD criteria
• Contraindication for surgical treatment of the disease
• Detectable disease by imaging
• Ability to give informed consent and to express the willingness to fulfill protocol requirements during the study

Exclusion Criteria:

• Current pregnancy or breast-feeding
• Acute infection
• Positive anti-HIV antibodies
• Hematologic alterations not attributable to hypersplenism, or in any case, intense neutropenia and thrombocytopenia, defined as neutrophil count lower than 0,5/pL or platelet count lower than 20/pL
• Participation in other clinical trial during the previous month