What: Celldex Therapeutics (CLDX -1.43%) and Momenta Pharmaceuticals (MNTA) ended down about 10% today on no news.

So what: The era of volatile biotechs continues. Throw in some upcoming catalysts, and it's easy for momentum to take hold.

Celldex told investors to expect results from an interim check of the data from its ACT IV trial testing Rintega in glioblastoma in March. If you haven't looked at a calendar recently, March starts tomorrow, Fools.

Momenta is waiting for results in multiple lawsuits: one to see if it can sell its 3-times weekly version of Teva Pharmaceuticals Copaxone, and another to see if other generics infringe on its patents for making generic Lovenox.

Now what: Whether Celldex or Momenta is up 10% or down 10% on any given day is irrelevant to where their stock prices will be after these events.

For example, either the Data Safety and Monitoring Board will tell Celldex it can stop the trial because the drug is working, to stop because it isn't working, or to continue the trial. Investors have an idea of where the stock should trade after each of those outcomes, so where it trades now only changes the magnitude of the move for those who are planning on holding through the announcement.