Most biotechs go through a cycle of depressed value. You can pick them up when they are depressed and then ride them into catalytic events. Its a medium term thing, 6 mos, a year. Sometimes you catch them right before the run for some fast money.
If you get them when no one wants them, you can risk the catalyst and swing for the fences at the risk of losing your gains in the run up.
The probability is not bad. Several losses - gains wiped out but hen you hit the 500 bagger.
The key is looking for them when noone wants them.
My entry in CLSN was around two and I got out around 1.50. Thats not as tight as it ought to be.