Kind of ridiculous how closely ISIS mirrors IBB. Even the little bump on the way up in the last hour. Doesn't matter really. ISIS led the way down, but will outpace IBB on the way up as IBB outpaces NASDAQ, Russell2k, etc and as they outpace S&P500.
Sector-wide selling has been happening for a couple weeks now. Isis is locked in step with IBB or rather the biotech sector. Hard to swim against the current. Lots of negative momentum in the market in general.