I was wondering why LABU, which is a 3x times leveraged biotechnological ETF, went down in July 2015. I understand that it tries to track SPSIBI (Biotech Index) whose top ten holdings are: ICPT, SRPT, REGN, LGND, ESPR, HRTX, ANAB, NBIX, VRTX, ALNY
Based on Yahoo Finance, some of these stocks had a very bad year in 2015 (especially ESPR, ALNY, and others).
Why was that? Does anybody remember what happened? Was it due to some state regulation or was it because of the poor performance of those particular companies?
I was unable to find reasons for why it went down so I'd like to ask here. Thanks for any helpful comment.