Ever since the NASDAQ debacle the stock has become a debacle. Many said they where completely out of their depth on business issues and PF's departure is the first recognition of this. He is a scientist and from I can tell a very good one. Since the Arrowhead results he has further confirmed BLT's advantage over their solution but I don't believe he ever communicated this properly to the market.
Anyway, CS is likely to be the next to go. A qualified CEO will remove any need for his role. GW will likely stay on as secretary.