from a quick scan of the investor's history they look to be exclusively private investments (not publicly traded co's) so I assume they were holding shares since before IPO and got freed from a lockup period. That's all total speculation however, I haven't looked deeply enough into things
Don't ask IR - I've tried to contact them for 2 years, by phone or email, and nada. There used to be a receptionist to at least answer the main contact number, but that seems to have been downsized. Not sure how much of this company you need to own to warrant a response, but I don't seem to be in that category.
My favorite euphemism for the lack of transparency is 'information asymmetry'. Some companies show a lot more of it than others. The recent haircut without anything from IR confirms that this company's strong suit is not transparency.
That's the million dollar question. Volume is huge today too. Either somebody knows something bad is coming (dilution? side effect problem?) or a significant holder is dumping for reasons unrelated to TSRX (margin call, etc.)