Let me give you a very clear example. Some types of breast cancer, for example, have receptors on the surface and they could be targeted by a drug. That does not apply to all types of breast cancer, but it does apply to some types of tumours. If some tumours have those receptors, they will respond very well to the drug and will be destroyed.
The problem is that we don’t want to give those drugs to everyone. If we did, it would be very expensive. In addition, most patients do not even have the receptors that allow them to react to the drugs. In those cases, they would experience all the side effects of the drug without benefiting from it at all.
The idea behind personalized medicine is to stratify patients and to ensure that we are developing drugs that are better targeted to patients who have a certain genetic history and who are going to respond to those treatments. By also conducting genetic tests, known as pharmacogenomics tests, we make sure to treat each patient based on their response capacity. We do not treat patients who would be likely to have more pronounced side effects because of their genetic make-up. So we have to reduce the side effects, target the treatment and, obviously, increase the capacity for treatment.