To date, we have not been able to specifically identify the exact cause of the health injury suffered by the volunteers from the UK. The identification of the cause will be subject of cooperation among the regulatory drug authorities, in which our Institute has been involved. The nature of the tested substance and the reported reaction suggest possible interference with the immunological mechanisms which is difficult to anticipate on the basis of the results of safety tests in animals and which may, rather rapidly, induce a dramatic change in the state of health.
In clinical trials, it is not possible to rule out some risks in advance. The tested medicine is usually not studied to the extend allowing for the determination of all of the product properties when used in man. Many risks may be identified on the basis of animal testing of medicines, yet for certain groups of medicines the data obtained from animals are difficult to extrapolate to man. Such groups are, in particular, medicines affecting the immunological mechanisms, influencing specifically “human” enzymatic systems or active in conditions which cannot be modelled in experimental animals.
In no clinical study – and actually not even during regular use - is it possible to guarantee the absolute safety of the medicine. In clinical trials, the participants always have to be informed in advance about the anticipated risks.
Monoclonal antibodies have established therapeutic uses and some of them are contained in approved and relatively widely used medicinal products. The target structures of the activity of monoclonal antibodies vary, and for this reason monoclonal antibodies cannot be considered a uniform group in terms of their effects. For example, they are used in the treatment of tumour diseases and in patients with autoimmune conditions, which may also manifest as neurological disorders or rheumatological diseases. A number of new monoclonal antibodies are, with a view to the various possibilities of interfering with the mechanism of many diseases, also tested in clinical studies. In the Czech Republic this involves approximately hundreds of patients. In those studies where the medicine is being given to patients rather than to healthy volunteers the patients are usually not financially compensated for their participation in the study.
The mechanism of action of monoclonal antibodies differs by the nature of the intervention for which they are intended. There are many mechanisms of action. One of the possible mechanisms of action is blocking an enzyme. Also, another active substance, such as a radiopharmaceutical or a chemotherapeutic agent, may be bound to the monoclonal antibody. In this case the monoclonal antibody indeed does serve as a “means of transport” and on the basis of a specific bond in a certain tissue the active substance itself gets directly to the site of action, in the concerned case into the tumour cell.