Clinical experience with HLA-B7 plasmid DNA/lipid complex in advanced squamous cell carcinoma of the head and neck.

OBJECTIVE: To investigate the safety and efficacy of alloantigen plasmid DNA therapy in patients with advanced head and neck squamous cell carcinoma using Allovectin-7 (Vical Inc, San Diego, Calif), a DNA/lipid complex designed to express the class I major histocompatibility complex antigen HLA-B7. DESIGN: Multi-institutional prospective trial. SETTING: Academic medical setting. PATIENTS: A total of 69 patients were enrolled in 3 sequential clinical trials: a single-center phase 1 trial and 2 multicenter phase 2 trials. Eligibility criteria included unresectable squamous cell carcinoma that failed conventional therapy, Karnofsky performance status score of 70 or greater, and no concurrent anticancer or immunosuppressive therapies. INTERVENTION: Patients received 2 biweekly intratumoral injections of 10 microg (phase 1 and first phase 2 trials) or 100 microg (second phase 2 trial) of Allovectin-7 followed by 4 weeks of observation. Patients with stable or responding disease after the observation period were given a second treatment cycle identical to the first. MAIN OUTCOME MEASURES: Patients were assessed for toxic effects, and tumor size was measured after cycles 1 (at 6 weeks) and 2 (at 16 weeks). RESULTS: Allovectin-7 treatment was well tolerated, with no grade 3 or 4 drug-related toxic effects. Of 69 patients treated, 23 (33%) had stable disease or a partial response after the first cycle of treatment and proceeded to the second cycle. After the second cycle, 6 patients had stable disease, 4 had a partial response, and 1 had a complete response. Responses persisted for 21 to 106 weeks. CONCLUSIONS: Intratumoral plasmid DNA immunotherapy for head and neck cancer with Allovectin-7 is safe, and further investigations are planned in patients with less advanced disease, where it could potentially improve patient survival and reduce the need for radical high-morbidity treatments.

Phase I study of direct intralesional gene transfer of HLA-B7 into metastatic renal carcinoma lesions.

Renal cancer cell lines exhibit deficient expression of MHC class I antigens required for appropriate CTL stimulation. Nabel et al. (Proc. Natl. Acad. Sci. USA, 90: 11307-11311, 1993) demonstrated that direct gene transfer of the deficient class I MHC molecule into melanoma cells would stimulate their immune destruction. Stopeck et al. (J. Clin. Oncol., 15: 341-349, 1997) demonstrated the clinical use of this approach in melanoma patients. We investigated the safety and ability to bestow gene expression via intratumoral transfer of escalating amounts of lipid-formulated plasmid DNA encoding for the MHC HLA-B7 gene product Allovectin-7 into metastatic renal cancer lesions. Fifteen patients with histologically confirmed, HLA-B7-negative metastatic renal cancer received intratumoral injection of Allovectin-7 on an escalating dose schedule. Tumors were evaluated serially by computed tomography scan, ultrasound, and physical examination. Presence of the HLA-B7 gene and protein was determined via PCR, flow cytometry, and immunohistochemical staining in serial biopsy specimens. HLA-B7 gene, mRNA, or protein expression could be conclusively demonstrated in 8 of 14 patients (57%). Three patients had tumor biopsy to assess the presence of tumor-infiltrating lymphocytes, and all three had higher posttreatment levels of tumor-infiltrating lymphocytes. There were no significant clinical responses or toxicity at the site of injection or at other, noninjected tumor sites. This study demonstrated that intratumoral injection of Allovectin-7 is safe, feasible, and associated with minimal toxicity. This approach was capable of bestowing gene expression, possible resulting in antitumor CTL response. Despite lack of tumor regression in this series of renal cancer patients, the simplicity and low toxicity of this approach commend it for Phase II studies in renal and other cancers, as well as for transfection with other genes.

Conserved folding in retroviral proteases: crystal structure of a synthetic HIV-1 protease.

The rational design of drugs that can inhibit the action of viral proteases depends on obtaining accurate structures of these enzymes. The crystal structure of chemically synthesized HIV-1 protease has been determined at 2.8 angstrom resolution (R factor of 0.184) with the use of a model based on the Rous sarcoma virus protease structure. In this enzymatically active protein, the cysteines were replaced by alpha-amino-n-butyric acid, a nongenetically coded amino acid. This structure, in which all 99 amino acids were located, differs in several important details from that reported previously by others. The interface between the identical subunits forming the active protease dimer is composed of four well-ordered beta strands from both the amino and carboxyl termini and residues 86 to 94 have a helical conformation. The observed arrangement of the dimer interface suggests possible designs for dimerization inhibitors.