The path from a validated target to an approved medicine is long, and most candidates that enter it do not finish. The stages below are the usual shape of that journey; the durations are typical ranges rather than fixed numbers, and they vary widely by disease and by how much is already known.
Target validation comes first. Laboratory work establishes that changing the gene or protein actually alters the disease process and that doing so is tolerable. This stage can take a year or more, and it sometimes ends with the target being abandoned.
Next comes the search for molecules that act on the target — the screening and optimization work. Many candidates are made and tested, and the ones that bind well, avoid obvious safety problems, and can be delivered in the body are refined into a single lead candidate. This typically takes several years.
Before any testing in people, the candidate goes through safety testing in laboratory systems and animals. This stage exists to catch problems that predictions missed, and it takes roughly one to three years.
Clinical trials then test the candidate in people, in three broad phases: a small group to check safety and how the body handles the drug, a larger group to see whether it actually helps, and a still larger group to confirm the benefit and track less common side effects. Together these phases usually take six to ten years.
Finally, regulators review the evidence and decide whether the medicine can be approved and sold. Even after approval, monitoring continues, because rare side effects may only appear once very large numbers of people have taken the medicine. From start to finish, the whole road commonly takes ten to fifteen years.