The Actelion drug discovery process consists of iterative cycles between chemistry and biology. Specialists from different fields (see also Technologies) gather in project teams to support drug discovery, which begins with the screening of a selected protein (drug target) leading to the identification of a chemical compound with biological activity (hit). After confirmation of the biological activity and the chemical feasibility, the hit becomes a lead structure, which is improved through chemical modifications until it fulfills the criteria for a clinical development candidate, eventually proposed for clinical development.