Cancer DNA vaccines: current preclinical and clinical developments and future perspectives

Abstract

The recent developments in immuno-oncology have opened an unprecedented avenue for the emergence of vaccine strategies. Therapeutic DNA cancer vaccines are now considered a very promising strategy to activate the immune system against cancer. In the past, several clinical trials using plasmid DNA vaccines demonstrated a good safety profile and the activation of a broad and specific immune response. However, these vaccines often demonstrated only modest therapeutic effects in clinical trials due to the immunosuppressive mechanisms developed by the tumor. To enhance the vaccine-induced immune response and the treatment efficacy, DNA vaccines could be improved by using two different strategies. The first is to increase their immunogenicity by selecting and optimizing the best antigen(s) to be inserted into the plasmid DNA. The second strategy is to combine DNA vaccines with other complementary therapies that could improve their activity by attenuating immunosuppression in the tumor microenvironment or by increasing the activity/number of immune cells. A growing number of preclinical and clinical studies are adopting these two strategies to better exploit the potential of DNA vaccination. In this review, we analyze the last 5-year preclinical studies and 10-year clinical trials using plasmid DNA vaccines for cancer therapy. We also investigate the strategies that are being developed to overcome the limitations in cancer DNA vaccination, revisiting the rationale for different combinations of therapy and the different possibilities in antigen choice. Finally, we highlight the most promising developments and critical points that need to be addressed to move towards the approval of therapeutic cancer DNA vaccines as part of the standard of cancer care in the future.

Keywords: Antigens; Cancer; Cancer vaccines; Combination therapy; DNA vaccines; Immuno-oncology; Immunotherapy; Neoantigens.

Fig. 1

The different types of cancer vaccines

Fig. 2

Innate and adaptive immune activation induced by DNA vaccines

Fig. 3

Mechanisms of action of therapies postulated to mediate synergistic effects in combination with DNA

Fig. 4

Ongoing clinical trials of the analyzed studies. a Cancer types using cancer DNA vaccines in clinical trials. b Type of antigens encoded in the DNA vaccine. c Studies combining cancer DNA vaccines with other therapies (endocrine therapy, immunotherapy, chemotherapy, chemoradiotherapy or adjuvants) or using DNA vaccines as a single therapy