Hi We talked about this gap many times. The "good" part, it was done under AIS ticker. :o))
There are gaps that never get fill (see Jazz and even ACAD if they get approval or buyout), so we just have to wait and see.
I think the selling is a fund that said : If the CEO don't want to take risk (minimal) with his free options and shares, maybe we should do the same and buy back after approval if we want to.
the insider selling in the year before the most important milestone of the company (up to date), sent the worse message to the market. Selling plan can be canceled any time, bad impression takes time to come over.