With the price gradually increasing, now above $18, this is not a time to sell. While ISIS had a nice gain since the october implosion and after the FDA approval, with most buyes having positive gains at these levels, long term this will be considered cheap.
Strongly believe the stock ends the year above $20 and am looking at $22-$24. As stated in several posts.
Still, it could pull back. So I'm more of a hold, but I have my shares. if your still looking to get in (or cover) no one can't predict the future. It's still worth while to grab some at these levels. If your long and have a nice gain, your never wrong to secure a profit and potentially buy on a pull back.
If someone would have said "ISIS will break a 52 week high" after I posted this, I'd have thought they where nuts. More proof the price is unpredictable, to dangerous to short, and full of long term potential.
Unless something amazing happens I can't imagine it would get above $25 by the end of the year, not with out some real residual cash flow.
Hold for the long haul. Your never wrong to take a profit. It may come in if your short, but why would you become or stay short at $18 let alone $19? If it breaks $20 no one knows what it will do. Gamble if you want.