it is not surprise nor secret they are putting a hard fight and are determined. so when this thing runs up on hope of accelerated approval, shorts come back with a hard and serious blow to the momentum each and everytime. and then the so call longs give in to fear and run. sooner or later, the longs can't take the attach anymore and give up completely. on real positive news will revive the sentiment.
It could be the shorts but as i have stated before i believe this is mm manipulation that occurs around option expiration. They will move the price in such a fashion that a majority of expiring calls and puts expire worthless.
if i am right the price should start back up on monday.