So wouldn't the real trade have been to buy TEVA premarket? They fell more and should regain more if Copaxone isn't damaged. And they have a 13 PE, not expensive. And TEVA did move back up nicely from its' premarket low.
MNTA I think moves up more because it is undervalued regardless of Copaxone rather than falls because of Copaxone, which I always thought was more of a theory about it getting approved anytime soon. In fact, if MTNA takes 2-4 years to get approved, then Copaxone could well be in decline.
IMO since a lot of retail also own MNTA, it tends to trade down more easily than stocks like AMZN, NFLX, ETC. Likely some retail are leveraged, making it more likley they will sell quickly.
On sale is sort of relative thing, IMO MNTA hasn't been on sale since the price went close to 5 in 2008. Below 10 is on sale, down 4% premaket isn't much of a sale.