ESPR $23.67 -20.17%
I haven't investigated this stock yet to understand it's price gyrations .. and really don't understand the prolonged spike to over $100 a couple of years ago.
From DE - this might be worth looking into. If this were an OTC stock, and if the spike in price hadn't lasted so long (the one to over $100) - I would write this one off as a classic 'pump and dump'- but there appears to be 'more to the story'.

Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...