The First Dendritic Cell-Based Therapeutic Cancer Vaccine is Approved by the FDA

To the Editor: The sentinel cell in the immune system, the dendritic cell (DC), has long been the front runner of new cancer treatments. The unique ability DC have to stimulate the immune system has been realised as a potent tool to treat disease ever since it was possible to grow DC in vitro from haematopoietic stem cells [1] or monocytes [2]. The potential for the treatment of patients was quickly realised, but the awaited advance in cancer treatment was slow in the coming. This was because of a combination of the complexity of cancer and the scientific community’s understanding of the regulation of the immune system as well as a number of technical challenges and a lack of good manufacturing practice grade reagents. However, together with advances in understanding the immune system regulation, a landmark paper was published by Small et al. in 2006 [3]. Small and colleagues showed in a placebo-controlled phase III study with prostate cancer patients an increased median survival and increased specific immunological activity. After 3 years, 34 per cent of patients were alive in the treated group compared to only 11 percent in the placebo group with a median benefit of 4.5 months. The immunological correlate of T-cell stimulation was 8-fold higher in treated patients compared to controls. The experimental set-up was a harvest of autologous monocytes, culture and treating the cells with a fusion protein consisting of prostatic acid phosphatase and granulocyte-macrophage colony-stimulating factor, before the differentiated DC were infused into patients. Although this was a significant finding, the US FDA approval of this treatment modality for metastatic asymptomatic hormone refractory prostate cancer patients was long pending with two more phase III trials completed before it was finally approved on 29th of April this year (http://www.fda.gov/BiologicsBloodVaccines/CellularGeneTherapyProducts/ApprovedProducts). This is the first therapeutic cancer vaccine to pass the hurdles to final approval and show that the DC vaccine field has matured enough to make the transition into the clinic. We foresee that this will not be the last of the new therapeutic vaccines to achieve a breakthrough and that this will become a standard treatment of care for cancer patients in the near future.