Positive Phase 2 results are typically the trigger for big...

Positive Phase 2 results are typically the trigger for big pharma to step in.
This attention will drive the price up, whether a deal is made or PRR decide to do it on their own and raise capital.
With less doubt around efficacy, we can start projecting the potential pricing on the final product with a bit more certainty.
With a better idea of future earnings, we get closer to the traditional rules of valuing companies. Using the average biotech P/E ratio, for example.
Then it's just working out how quickly we can attain peak sales of a given market share.

My crystal ball says the price would spike on the news and climb for a few sessions up about 200% before profit taking drops it back down 30 or 40%. Then it will trade around those levels for a weeks as SM accumulates, raising it another 10-15%.
They'll sell out and perhaps start shorting in order to trigger stop losses and scare the retail investors and accumulate further.
Prima will announce they've secured a breakthrough designation which expedites the P3 trial. FDA has a look at the interim data and decides it's in the best interests of the patients that the control arm receive CVac and conditionally approve it for commercialisation and adjust the P3 to continue as a confirmation trial.
Market Cap increases 2000%, then another 5000% as the additional trials potentially prove CVac works in all MUC-1 over-expressing cancers.

Either that or it crashes on Oct 2.