the only thing would be if a BP wanted to take a chance on the company. A sizeable offer before approval might tempt ARNA to sell.
Think about it, BP would get a bargain compared to post approval and ARNA would get a safe out just in case.
My thoughts are this wont happen, but that is the only scenario in which it would. Furthermore, if it did happen, I'd sell on the pop and gtfo, because know one knows better about their drug than ARNA. If they sell pre approval thats a bad bad sign.