What pullback? Maybe we get a 52 wk high today, volume is strong and price is up. By the way, insm won't be selling any shares to the russell index funds. Those shares are being collected daily on the open market and will be sold at a prenegotiated price which could be blown to smitherines if phase3 results come in the next 4 weeks!
Jesse - I'd be extremely surprised if any of the agents for the tracker funds have started buying INSM yet. The INSM bit is far too insignificant in the scheme of things for them to be worrying about it yet. They have far bigger fish to fry.
My gut feeling is that when they do start to accumulate in June, the share price will go to $30-plus almost immediately.