I believe the primary reason for the move is over confusion that somehow AEZS is still associated with KERX. Other reasons can include resolution of lawsuits against the company, upcoming pipeline catalysts, or various unsubstantiated rumors. What's puzzling is the insane volume which suggests to me that something major is possibly going on behind the scenes and has leaked out. Look what happened with KERX last week. I sincerely hope this is true, especially for the sake of longs who have held their shares through last April's perifosine debacle.
I hope that there is a leaked catalyst for this move, but I suspect that your theore about the KERX confusion in partially to blame. Both have taken an after-hours downturn after the KERX shelf offering announcement.