Sometimes you get a big bang if its approved but the real profit is made during the run up. If you gonna do biotech plays with FDA approvals you gotta be scoping the PDUFA calendar every month (
https://www.biopharmcatalyst.com/calendars/pdufa-calendar) to know whats coming up, hop in accordingly and ride the waves up to the date. I got almost 30% off TRVN a week or so before the approval date. I know others made way more if they got in earlier. I'm up almost 25% on LPCN and its approval date isn't until Aug. 28th.
FDA Approvals are like earnings, good or bad, it's hard to predict which way it will go and even harder to predict reaction. I generally get out before approvals and then move onto the next although, like earnings, you can play the overreaction to the FDA decision as well.