Discovery hands off a candidate
Drug discovery is the part that finds a molecule: a target, a hit, a lead, and after lead optimization a single drug candidate chosen at candidate selection. That candidate is a real, well-characterized new chemical entity with decent potency, selectivity, and ADMET properties. But it has only ever been tested in proteins, cells, and maybe a handful of animals. Nobody knows yet whether it is safe or useful in people. Closing that gap is what *development* means.
Once that molecule is committed to development it is usually called a clinical candidate, and a company tracks all of its candidates together as a drug pipeline. Development is no longer mostly chemistry: it is toxicology, formulation, manufacturing, clinical medicine, statistics, and regulation working in parallel for years.
Long, costly, and mostly failure
The honest headline numbers: from a development candidate to an approved medicine typically takes 10–15 years and costs on the order of one to two billion dollars when you count the failures it took to get there. And failures are the rule, not the exception. This loss of candidates along the way is called attrition. Of the candidates that enter human testing, only roughly one in ten reaches regulatory approval.
The shape of the journey
It helps to see the whole map before zooming in. Each stage in this list is a guide in this track:
- Preclinical — animal safety and dosing studies under strict quality rules, to justify the first human dose (preclinical development).
- IND — the regulatory application that legally opens the door to testing in humans (investigational new drug).
- Clinical phases — Phase I, II, and III trials answering, in turn, *is it safe?*, *does it work?*, and *is it better, in many patients?*
- Quality and approval — making the drug reproducibly (GMP/GLP) and convincing regulators to approve it.
- Patents, generics, biosimilars — the economics that decide who can sell the medicine, and for how long (patent, generic, biosimilar).