Thanks bear....things are starting to come into clearer focus.  

Thankfully we have that news from this past June that the FDA is likely to support a NDA for Apabetalone if BETonMACE is successful:

https://globenewswire.com/news-release/2018/06/14/1524896/0/en/Resverlogix-Announces-FDA-Confirmation-Regarding-Filing-Pathway-for-Apabetalone.html

The FDA link that CP provided now makes sense....to be frank I thought phase III was basically the end of the line, that if it failed the only recourse would be anotehr phase III trial.  That info on the FDA's page talks about the rate at which drugs move from Ph 1 to Ph 2, then Ph 2 to Ph 3, and finally Ph 3 to Ph 4.  It doesn't talk about approval rates....just the rate at which drugs move to the next stage.

Obviously not all drugs that are approved for marketing, not all of them require a Ph 4 study....but as per that info, 25-30% of them do.  I'm going to accept the roughly 60% approval rate for Ph III  cardiovascular drugs as being pretty much on the money....meaning roughly 6 out of every 10 CVD drugs are approved for marketing, but that 2 or 3 of them still require a further Ph 4 study after they've been approved.

A side benefit of a Ph 4 study is that in addition to looking for potential long term side effects, they also can provide data for further applications for a drug.  I've been reading how mental health conditions like bi-polar could have an arterial component....