Alloantigen gene therapy for squamous cell carcinoma of the head and neck - Results of a phase 1 trial

Objective: To determine the safety and efficacy of an immunogenic gene therapy using a drug designed to produce expression of a foreign class I major histocompatibility complex protein in patients with head and neck cancer. Design: Phase 1 prospective clinical trial. Setting: Academic medical setting. Patients: Nine patients with advanced head and neck squamous cell carcinoma who had failed conventional therapy and did not express HLA-B7, a class I major histocompatibility complex protein. Intervention: Patients were treated with Allovectin-7 (Vical Inc, San Diego, Calif) by direct intratumoral injection. Allovectin-9 contains a plasmid complementary DNA complexed with a cationic lipid, which results in expression of HLA-B7. Main Outcome Measures: Patients were assessed for any toxic effects and for any change in tumor volume. Biopsy specimens obtained before and after therapy were evaluated by immunohistochemistry to detect HLA-B7 expression and with the terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assay to detect any induction of apoptosis. Results: There were no toxic effects of the gene therapy. In 4 of these 9 patients there was a partial response to treatment, evidenced by a gradual reduction in tumor size. One patient has remained alive for more than 17 months since commencing treatment, with no clinical evidence of disease but with persistent histological evidence of cancer. Analysis of the biopsy specimens from 2 of the patients who responded to therapy demonstrated HLA-B7 expression. The TUNEL assay demonstrated extensive apoptosis in both of these patients, suggesting that this may be the mechanism of tumor reduction. Conclusions: These data demonstrate the potential efficacy and lack of toxicity of this form of alloantigen gene therapy. A multi-institutional study has been initiated to expand on these findings.