I find that interesting with approval days away they decided to change it. We will be halted on monday btw i would say by noone so the shorts are running out of time.
No I don't think its a matter of the risk of getting the nod.
No one really knows yay or nay about the FDA approval, although a lot of people seem to have their opinions, which are simply just their opinions.
Its a matter of the institution heavily leveraged to one side on a position in a particular stock (in this case SCHWAB itself and its clients with MAPP). This is a "margin call" of sorts to ensure that if there was a sudden need to "close" positions wrt MAPP, they can do it in such a way that it is not detrimental to the institution's health. A margin call brings things back into balance - or so the institution believes, except that it "could" cause volatility on the stock and its derivatives, as people scramble to close. Volumes could be a killer, but I don't think its that bad here.
I ain't no expert, so take this with a grain of salt.
Margin requirements are different from institution to instituion. Its a way for an institution to protect its portfolio, so it sounds like Schwab has an unusual amount of action for MAPP and is seeking a hedge by calling upon it(?)
My institution has it at 30% for me, they provide 70% loan.