Yes, you definately need to see PIIb data and maybe some trials in related indications before you wait around for PIII data.
Two other red flags I will look for in the future after my unpleasant Pharmos experience:
1) Murky modes of action. I was always a bit nervous about the 'multiple modes of action' of dexanabinol. It was supposed to be a cannabinoid, but it wasn't active at either of the two known cannabinoid receptors. It sounded like Pharmos wasn't exactly sure how it worked - turned out that it didnt' work.
2) Small biotechs with no big Pharma partners. Pharmos had no partnerships at all. You would think in a hot field like cannabinoids they could have done some sort of collaboration. Now I want to see a small company's science validated by a partnership with a big pharma. I figure these big pharma guys ought to be able to evaluate the potential of some bio-technology much better than I can.
These are two reasons I like Arena right now. (1) They are focused on small molecule drugs targeting GPCR's - so the mode of action is crystal clear, and (2) Arena has partnerships with Merck and J&J. So probably this company is not a total scam.
Actually, with Arena, the risk is right out in the open, they are trying to resurrect Phen-Fen. I am hoping that since they are trading at close to cash, there is not too much downside risk in holding through their upcoming PIIa obesity results (due in June). Plus, Arena is not a one compound company, they have lots of other compounds coming along for other indications. So if Son-of-Phen-Fen flames out, the story is not over.