Clinical trials with α-galactosylceramide (KRN7000) in advanced cancer

For over a century, research has sought ways to boost the immune system of cancer patients in order to eradicate tumors that arose after escaping presumptive immunosurveillance. With increasing knowledge of the immune system, immunotherapeutic strategies to break tolerance to the tumor evolved from largely nonspecific to more specific and increasingly potent forms of cancer vaccination. Overall however, immunotherapeutic strategies for the treatment of cancer have had limited clinical success and an urgent need exists, therefore, to introduce more effective, knowledge-based therapeutic approaches. Invariant natural killer T (iNKT) cells constitute an evolutionary conserved T lymphocyte lineage with dominant immunoregulatory and antitumor effector cell properties. iNKT specifically recognize the glycolipid α-galactosylceramide (α-GalCer/KRN7000) in the context of the CD1d antigen-presenting molecule resulting in their activation. Activated iNKT have been shown to promote the development of a long-lasting Th1-biased proinflammatory antitumor immune response in a variety of murine tumor-metastasis models of liver, lung and lymph nodes, including colon and lung carcinoma, lymphoma, sarcoma, and melanoma, suggesting broad clinical applicability. Here, we will provide an overview of the preclinical data of α-GalCer that formed the basis for subsequent clinical trials in advanced cancer patients, review these clinical trials, focusing on our own experience with α-GalCer, and discuss future perspectives.