It's pretty common to see a biotech tank on any given day, so when three companies dropped substantially the other day, it wasn't that surprising. Unless you're an investor in the companies, of course.

Seattle Genetics (NASDAQ:SGEN), which sells cancer drug Adcetris, dropped because revenue was only up 19%. While that wasn't exactly the growth investors were hoping for, Seattle Genetics still has a substantial pipeline worth owning.

Pharmacyclics (UNKNOWN:PCYC.DL) was another earnings "loser." During the first full quarter on the market, demand for its cancer drug, Imbruvica, came in at a little over $50 million. Despite getting a second approval in mid February for CLL, which is a larger market than mantle cell lymphoma that it was first approved for, Pharmacyclics guided for sales of just $295 million for the year.

Finally, Endocyte (NASDAQ:ECYT) was the loser of the group after announcing that its trial testing vintafolide in ovarian-cancer patients was stopped early for futility. Based on data to date, the data monitoring committee believes the trial won't be able to show that vintafolide increases in progression-free survival if Endocyte let it go to completion.

In the video below, senior biotech specialist Brian Orelli and health care analyst David Williamson discuss the drops and which companies might be bad-news buys.