IL-12 Gene and in Vivo Electroporation-Mediated Plasmid DNA Vaccine Therapy in Patients With Merkel Cell Cancer

PRIMARY OBJECTIVES: I. To measure the effect of intratumoral injection of tavo followed by in vivo electroporation (EP) (electroporation-mediated plasmid DNA vaccine therapy) on the local expression of interleukin-12 (IL-12) in the tumor microenvironment in patients with Merkel cell carcinoma (MCC). SECONDARY OBJECTIVES: I. To assess the safety of tavo-EP in MCC. II. To assess the clinical efficacy of this treatment approach in MCC. III. To assess the immunologic changes resulting from this treatment approach. OUTLINE: Patients receive tavo intratumorally (IT) and undergo electrical discharge via OMS around the tumor site for electroporation-mediated plasmid DNA vaccine therapy on days 1, 5, and 8. Patients with unresectable disease may receive a second course of treatment in 12 weeks. Patients with localized disease proceed to definitive treatment as determined by the treating physician starting 2-4 weeks after the first injection. After completion of study treatment, patients are followed up at weeks 4-8 (for patients who received definitive treatment) or 12 (for patients with unresectable disease) and then annually for up to 5 years.