I've seen JAZZ, REGN, and PCYC all cited as exampl

I've seen JAZZ, REGN, and PCYC all cited as examples of wild share price swings/fluctuations. While it's helpful to see that this has happened in otherwise wildly successful biotechs, it might be equally helpful to know the reasons behind it (for comparison). I've not been investing long enough to know and don't really know where to look to find out. Do any of you have knowledge of what brought about those huge share price declines in those companies?

TIA