The stock is in the hands of the traders now, who will create volatility as long as the fundamentals don't change or as long as volume remains strong. While it would have been nice to see the stock hold in the $4's until phase III, there probably aren't enough institutions willing to take on the risk and retail support is probably lean due to the "underwhelming" phase II results (underwhelming in that most people don't understand that 20% partial response and 30% stable disease is actually excellent when compared to existing treatments). Any way, unless you get an analyst that goes out on a limb (which they probably won't before the phase III results), we will be in the hands of the traders. They'll get bored when the volume dries up.
Well I also believe it will be traded for all it's worth for the next week or two until the volume dries up. It is obvious that there was a lot of share sold today by institutions. It also appears there were others who were more than happy to buy. Hopefully they have all positioned themselves now and it did seem like they let it free at the end of the day.