I don't think that's indicative of that at all. Firstly, if their CMO knows anything about how the trial is going, then moderna is in way bigger legal trouble than some insider trading stuff.
Secondly, loook at their situation. They've had a multi billion valuation for years with nothing on the market. They get a contract for a vaccine, and get a couple billion out of the feds. BILLIONS IN NON-DILUTIVE FUNDING. Think about that. Then the markets react by pushing they stock even higher, to the point where it was 15x what it was before the announcement.
Now let's digress for a moment to Gilead. They cured Hep C. It put them on top of the world for a couple years... Then their stock went to shit after they cured everyone. They fixed a problem no one could fix for millennia and it fucked them up the ass. Such is the stock market. And that was for a drug they could charge $80,000 a pop for or something, netting them like $12B per year.
Now back to moderna. They can't charge a premium on the drug per the rules of the government's funding (at least not to Americans--not sure about anyone else). And they know even if they could this problem is going away in 6mo to a year after vaccine approval, in which case they're going back to $6/share like really, really quickly.
So while I don't like it on its face, it's probably the rational thing to do.