The Role of Therapeutic Vaccines in Cancer Immunotherapy

Cancer vaccines offer an exciting option for active immunotherapy, providing a potentially safe and effective treatment that also prevents or minimizes toxic side effects in vaccinated patients. Clinical results from previous phase III clinical trials have suggested that the efficacy of cancer vaccines largely depends on their potential to trigger robust immunological responses. A preexisting immune response to cancer-specific peptides is crucial for achieving a meaningful clinical outcome during vaccinations. However, various factors may hinder the effectiveness of therapeutic vaccines. By overcoming these challenges, cancer vaccines have the potential to become a cornerstone in immunotherapy. This review aims to share our insights on the major challenges that are encountered when optimizing the potential of cancer vaccines, particularly focusing on important aspects regulating their clinical efficacy, such as vaccine composition, the adjuvant to be used and the HLA-restricting element for the tumor peptides targeted by a particular vaccine. Additionally, we discuss several obstacles which hindered the successful clinical development of therapeutic cancer vaccines, such as the standard of care, the clinical design, and the choice of the antigen(s) to be included in vaccine formulation. The identification of patients that are most likely to respond to vaccinations by developing immunological responses and the desirable clinical efficacy are also crucial, and, therefore, predictive biomarkers are strictly required. Finally, we present our views on future prospects that may lead to an enhancement of the anticancer effects of vaccines, ensuring their pivotal role in cancer immunotherapy.