Early drug development is usually subdivided into 2 main parts.
- The first part precedes the FIH clinical trial, it is the preclinical phase. The preclinical phase, a critical step in early development as it will provide the data needed to conclude whether the NCE is bioavailable and safe enough to be tested in humans for the first time.
- The second part is the clinical phase where the drug candidate is generally first administered in a single ascending dose to human volunteers (phase 1a), followed by repeated ascending dosing in human volunteers (phase 1b), and finally administered at different doses and dose regimens to relatively small number of carefully selected patients (phase 2a).