Rubbing my ball, page-468

So my very broad, layman understanding:
- phase 1 determines if it is safe
- phase 2 determines if it works (hence common failure point)
- phase 3 is a relatively (to the above) large, expensive trial testing efficacy to a level that is acceptable to regulators.

Welcome correction or confirmation for those with more knowledge in this area. As I said this is my broad, layman understanding and I realise that clincal signs for early efficacy could be tested in phase 1 and safety continues to be assessed throughout.

So we need phase three for widescale retail sale. There are exceptions, for example I think I saw somewhere you can access Japanese markets after earlier phases, which is why companies often start their for early revenues, if anyone nows more about that please comment.