Diagram of major milestone transition and go/no-go decision points in the discovery phase of pharmaceutical R&D leading to preclinical development. Details as follows: (1) Conduct exploratory work that includes project conception, target validation and screening. (2) Identify chemical lead(s) and establish target drug profile. (3) Optimize chemical properties and biological activity against the target drug profile. (4) Complete all necessary studies to allow an investigational new drug (IND) application to be filed.