The normal reaction for a shareholder when the price has gone...

The normal reaction for a shareholder when the price has gone down is to console himself by saying that it is a good buying opportunity. One has to determine why the price has fallen and in this case the reason is obvious as the primary endpoints were not met and hence it is now a case of analysing the detailed report to determine where the failings were and going back to the drawing board and making adjustments to the formula to determine if that would improve efficacy.
The current report will put off partnership arrangements and this could be quite detrimental to future negotiations and PAR may not have a good bargaining position in subsequent negotiations.
There are however other products in the pipeline and hence not all is lost. A product can only be commercialised if it passes all the phases of clinical testing and this is long process. Be patient and do not rush to buy just because it looks cheap. That's my view and the best is to DYOR and then decide what you want to do.