In my experience, nothing is more dangerous than chasing a bad short up. If you were short this, you should have had stops in. Besides, shorting these biotechs - as opposed to just gambling on some puts, which is what most of the so-called "shorts" really do - is extremely dangerous. These things could pop 10 or 20 bucks at any time. And what is the bad news which could drive MDVN down dramatically? The only danger here is from profit-taking.
Do you remember DNDN and what's the reason why DNDN to go down from 52 to 4 now?
The answer is overprice and earnings (DNDN has earnings but not as expected). The fact is MDVN is overpriced and no earnings (loss). The only thing keeps its price high is HOPE with a lot of empty promises. Time will tell. After a couple of mediocre quarterly earnings will make MDVN to fall the same way of DNDN.