Taking aim sooner
If personalised medicine is to achieve its full potential, it should be used earlier on in clinical trials
Jun 9th 2011 | from the print edition
ONE of the prospects supporters of the Human Genome Project held out was personalised medicine. Knowing which genes were involved in a particular patient’s disease would allow drugs to be deployed with greater precision. That is starting to happen in the field of cancer. Several targeted therapies, aimed at specific cancer-causing mutations, including Gleevec for chronic myelogenous leukaemia and Herceptin for some types of breast cancer, have been spectacularly successful. Yet in most cases of cancer doctors still base their treatment on where in the body a tumour has sprung up, rather than on which molecular aberrations have caused it.
The same is true of medical researchers recruiting volunteers for clinical trials, especially those known as phase I trials, in which a new drug is tested on people for the first time. Participants in such trials are often those whose tumour has spread beyond its original site, and will probably prove fatal. Usually, they have tried all proven therapies, to no avail. Their precarious condition means they are rarely accepted for phase II and III trials, which are more complicated and extensive.
Oddly, though, even if the drug being tested is a targeted therapy the tradition in phase I trials has been to gather together patients with, say, lung cancer and assume that all carry the relevant mutation. That is because such trials are concerned mainly with testing a drug’s safety, not its efficacy. The volunteers are usually happy to go along with this. But the odds are not good. On average, fewer than 5% of participants in phase I trials respond successfully to the treatment.