Arna has many possible catalysts that could either explain and or justify today's move (I have been buying Arna-dollar cost averaging). Absent pending news, IMO, today's move is likely "option" related, etc. If arna managed to stay above 8, someone is stand to benefit quite bit, etc. Furthermore, it is possible that this same person or persons could also bought arna shares (double dipping).
Orex started having bids at and or around the same time that arna started going up, etc. Unfortunately, orex has no such catalysts that can justify any sustainable upward momentum, etc. I just shorted orex today.
The biggest differece between the two (arna & orex) other than the obvious fudamentals and potential catalysts is the surge in volume in arna, etc.
I will be looking into selling my arna shares tomorrow for a nice profit (I take my profits).
I wish bought more shares of arna. What a nice gain! So, basically depends on strength and momentum of trend & rumor, I would have to decide to either to lock-in the profits or add more shares, etc. This is what we call a happy problem, so no rush to anything, etc.
Now, I am long arna and started shorting orex. I will start shorting orex dollar cost averaging unless there is a trend change and or if it move against my position and reaches my "cut-loss-n-run" (cover) threashold, etc.
Now that I started shorting orex, I would not engage in any, IMO stuff, until I no loger has a position in Orex, etc.