Messenger RNA and Plasmid DNA Vaccines for the Treatment of Cancer

Immunotherapy is now an established therapy for nearly a third of patients with cancer. Most therapies, typically using cytokines or checkpoint blockade therapy, rely on global activation of immune effector cells. The ability of vaccines to activate specific populations of cells has led to a renewed interest in their ability to treat cancers, either alone or with other immune therapies or other conventional therapies. The COVID-19 pandemic sparked a new interest in nucleic acid vaccines with the development of new technologies and the short manufacturing time for vaccine implementation. Nucleic acid-based cancer vaccines have been studied for decades, but have shown modest anti-tumor efficacy as monotherapies, as many of these vaccines encode for shared tumor-associated antigens (TAAs) and must overcome immune tolerance. New developments, technologies, routes of delivery, and combination therapies have paved the way for new approaches and clinical trials involving nucleic acid vaccines for the treatment of cancer. Here we review mRNA and pDNA vaccines for the treatment of cancer, including similarities and differences in their mechanisms of action, an overview of these treatment modalities in preclinical and clinical studies, methods to improve these vaccine strategies, and exciting new combination approaches in development.