Enthusiasm over tumor immunization strategies is increasing with the availability of multiple cloned tumor associated antigens as targets. Similarly, interest in polynucleotide immunization is rapidly growing with numerous demonstrations of efficacy in animal models of infectious diseases. The applicant has shown that a polynucleotide vaccine encoding human carcinoembryonic antigen (CEA) can elicit CEA-specific cellular and humoral immune responses as well as protect against challenge with syngeneic CEA-expressing colon cancer cells. In this application, the applicant will perform preclinical and clinical trials of polynucleotide immunization in two tumor systems: 1) colorectal adenocarcinoma with CEA as the target antigen, and 2) melanoma with melanoma antigen recognized by T cells-I (MART-1) as the target antigen. In addition to the relevant tumor-associated antigen, each polynucleotide construct will encode hepatitis B surface antigen to demonstrate the efficacy of this novel vaccination strategy in humans as well as provide a control for plasmid DNA purification and delivery. Murine developmental studies will evaluate the optimal molecular configuration for co-expression of a tumor-associated antigen (TAA) and HBsAg; the optimal configuration of the TAA (membrane anchored versus secreted) to elicit antitumor effects; technique of administration (intramuscular, intramuscular during muscle regeneration, or biolistic delivery); dose and schedule variables; and co-delivery of accessory molecule cDNA's to augment immune response and antitumor effects. Further murine studies will examine the mechanisms whereby polynucleotide immunization elicits antitumor effects. Reagents selected for human trials will undergo preclinical testing in a limited number of primates to identify the optimal dose and schedule as well as adverse effects. The applicant has accomplished preclinical development of the CEA/HBsAg polynucleotide construct for use in the first two proposed trials: 1) phase la trial in metastatic colorectal cancer, and 2) phase lb trial in Dukes' C colorectal cancer. Preclinical development of the MARTI /HBsAg construct is ongoing for use as post-operative adjuvant therapy for high risk melanoma. He will conduct these trials in conjunction with a laboratory effort to extensively characterize patient immune response to the encoded antigens as an intermediate endpoint of vaccine efficacy. Results of these phase I studies will provide a regimen which elicits a substantive immune response to the encoded tumor-associated antigen in the majority of patients. This regimen can then be taken to phase 11 and III trials in low tumor burden patients to evaluate impact on disease free and overall survival.
