In the 15 days immediately prior to CTAD, AVXL short interest rose from about 10.1M to 11.9M shares on November 30. That was before any information was out. The stock dropped from the 14s to the 9s. I will bet you the short number has increased since then.
At worst, we are getting a mixed report trial. And even before that outcome, which is not objectively bad news, I challenge you to find any analysts who were factoring AD sales into their revenue models. So the stock price has not dropped on the fundamentals.
Market psychology is part of the game, and institutions are market professionals at influencing investor emotions. And that is happening here. There is short selling, which leads to lower share price, which leads to additional sales (including stop loss and margin calls), and this cycle reinforces itself. People are selling when they don't want to or shouldn't. It may not be a "panic," but it is clearly being amplified by some big money. On the merits alone, AVXL is well undervalued.