Biogen received notice that Medicare patients would not be eligible to get it Alzheimer's drug, which is probably scammy anyways. It has been in a longterm downtrend and dropped further on this news.
Biogen bottomed out in the pre-market and had established a steady uptrend that eventually took out the pre-market range to the upside. The trend was over several hours and had stretched over 2 standard deviations from VWAP. When this trend broke it could signal a good place for longs to close their trades and you should get some kind of mean reversion was my thinking.
BIIB broke it's uptrend and I got short looking to capture a mean reversion scalp trade. I just paid the offer as it crossed the uptrend. I was risking a move back across that line, which never materialized as the trade quickly started to work. Ultimately I would have like to have captured a move to VWAP, but that was very far away and the stock had been strong. Part of the trade got trail stopped out, but I tried to reestablish with little added profit.
This trade was likely so successful because the uptrend was so long in duration and well established. The trade was to catch the momentum part of the move and I caught the meat of one leg, which is just fine. This offered excellent risk to reward.