The peptide telomerase vaccine, GV1001, is under development for use as active immunotherapy in the treatment of cancer. Normally, the immune system is tolerant to self-proteins and peptides, while being able to react to foreign pathogens. However, cancer cells are degenerated cells and many of their peptides and proteins are self-proteins or peptides. By using vaccination, the immune tolerance towards a specific peptide or protein can be circumvented.