Navigare necessere est. Improved navigation would help to solve two crucial problems in modern drug therapy: toxicity and precise delivery.

The availability of the human genome sequence together with major advances in biological technologies have an enormous potential to usher in a new era of medicine. We can imagine a situation in which a physician uses advanced molecular and imaging techniques—individually or collectively— to diagnose an illness and determine the exact molecular ‘fingerprint’ of the disease, be it cancer, cardiovascular disease or an infection. The physician will not only know what has gone awry in the patient’s body but also have access to a wide range of new, highly effective therapeutics that directly tackle molecular defects or invading pathogens without causing side effects. Such drugs could be, for example, peptides that specifically instruct cancer cells to initiate apoptosis, or molecules that repair a defect in the DNA of the cell. Many biomedical researchers are optimistic that such a scenario will be realized through the current advances in genomics, proteomics, systems biology and advanced diagnostic and imaging techniques, in conjunction with new methods of drug development. This scenario challenges our current concept of treatment, whereby physicians identify a disease and prescribe a drug to treat it. Quite probably, the concept of a drug targeted against a single illness will no longer be accurate. Many diseases induce changes to cells and tissue, such as those that occur in tumour development, which involve numerous genes and proteins. Even a simple infection triggers a complex cascade of gene and protein actions both in the infected cells and in the cells of the immune system. Instead of using a therapeutic that tackles rapidly dividing cells to kill tumour cells—which in the course of treatment affects normal body cells—or an antibiotic that kills beneficial bacteria as well, it would be much safer and more efficient to use therapeutics that target only the molecules that are involved in pathogenesis. It is logical to assume that, as soon as we know the precise sequence and pattern of molecular events for a specific disease, we can devise such drugs to interfere with pathological processes and correct what has gone wrong. Some of these new, so-called ‘smart’, drugs are already available or are under development. They include small peptides that target specific surface receptors on cancer cells and also gene therapeutics— gene constructs, antisense oligonucleotides and small interfering RNAs (siRNAs)—that induce changes specifically in metabolism or gene expression. Another example is the protease inhibitor that blocks HIV protease and thus prevents the virus from maturing. On the diagnostic side, there are further advances: new diagnostic tools based on gene or gene expression analyses allow physicians to select the most effective drugs to treat various cancers or to circumvent drug resistance in anti-HIV therapy. These are the first harbingers of this new concept of medicine, and the next few years will probably see the arrival of many more peptides, antibodies and other molecules.