It turned out that the immune response against the envelope E1 protein, which is located on the surface of the virus, was low or entirely absent in most chronically infected patients. So far, chimpanzees are the only recognized animal model that can be used for the evaluation of the impact of a therapeutic agent on the natural development of hepatitis C, before clinical studies on human beings are started. The immunological response of these animals can have a predictive value for the evaluation of the possible results of vaccination in human volunteers and patients. By gaining more insight into the structure and the function of a virus, a therapeutic vaccine can be prepared which will enhance an organism's capacity to fight off a virus and to eliminate it, by inducing an immune response that includes a substantial increase in the antibodies and protective T cells in the organism. Such therapeutic vaccines are a relatively new approach in clinical medicine.
Clinical studies mean that a potential medicine is being administered to human beings.
Efficacy and safety of the new treatment are compared with a placebo or with the existing standard treatment. Usually, several complementary Phase III studies are performed simultaneously. The reports of the Phase I through III studies are part of the registration file. Studies commencing after closing the registration file but before the product is released on the market are sometimes grouped under the name Phase IIIb studies. Phase IV Phase IV starts when the product is released on the market.