I wouldn't call that cautious...I'd call it smart. I've limited my exposure by selling shares and transferring funds into July call options. Even when PPHM reached stat. sig. doubling of OS in 2nd line, the stock only went up 50% and those who knew what it meant and acted quickly were able to buy shares at a modest premium to the prior day's closing price. With such a small trial that is very unlikely in front line.
So, in a positive scenario lets say front line improves OS by 50%. I'd imagine the stock would open up about 50% or at around $2/share. Lots of room up from there for the next, safer Avastin. If there's only a modest improvement (say 20%) which I think will be the case there will probably be a negative effect on the PPS and the "placebo clowns" will be at it again with their lack of p-value, etc. etc. arguments.