Therapeutic Cancer Vaccines: How Much Closer Are We?

The promise of immune-based therapies to treat cancer has been realized over the last several years with several breakthrough therapies, including T-cell checkpoint inhibitors and chimeric antigen receptor (CAR)-T cell therapies. While cancer vaccines have been investigated for many decades, to date only one has been approved in the USA as a treatment for existing cancer. The failure of several anti-tumor vaccines in large phase III trials has led many to question their future role in cancer treatment. Trials to date have demonstrated that many cancer vaccines can elicit tumor-specific T cells, but these T cells may be insufficient to mediate substantial anti-tumor effects without concurrent blockade of tumor-resistance mechanisms. Emerging data from preclinical models and clinical trials demonstrate that cancer vaccines have greater activity in low-volume disease and in combination with other immune-modulating therapies, including T-cell checkpoint blockade, targeting these resistance mechanisms. Because T-cell checkpoint therapies likely require the presence or activity of tumor-specific T cells, cancer vaccines may be optimal agents to use in combination to enable these therapies to work for greater numbers of patients. Future trials will explore optimal vaccine approaches and antigens that work best in combination treatment approaches and in earlier stages of disease.