I'm writing this a couple days later, so I don't remember the exact catalyst, but I think BCTX introduced some new drug or something, so it was in-play this day. It has a history of spiking on news before fading back, so I knew there was possibility for good upside given pre-market price action.
I had bids against the pre-market low, which got hit and immediately stopped because I had too tight a stop at ten cents. Given the share size and time of day, my risk allocation should have been larger. I got wicked by 3 pennies before it ran almost $3. I was trading something else which prevented me from re-entering. I find that I am really good at identifying good entries by reading charts, but in this case my aversion to risk prevented me from making a good trade.
Lesson: Don't run super tight stops on the open, especially on names I am not actively managing.