Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Epizyme (NASDAQ:EPZM), a clinical-stage biopharmaceutical company developing treatments for patients with genetically defined cancers, exploded higher by as much as 84% after it announced after the bell on Monday that EPZ-5676, a DOT1L inhibitor for acute leukemias, had reached its proof-of-concept milestone.

So what: According to Epizyme's press release, its achievement of the proof-of-concept milestone, which was triggered by "objective responses in patients with translocations of the MLL gene," earns the company a $25 million milestone payment from its collaborative partner Celgene (NASDAQ:CELG), which has the rights to the currently experimental drug outside the U.S. In addition, Epizyme's update also notes that it earned a separate $4 million milestone payment from GlaxoSmithKline (NYSE:GSK) for one of three histone methyltransferase target included in the duo's collaborative efforts. Because of these payments, Epizyme boosted its year-end cash guidance to $145 million from previous forecasts of $115 million.

Now what: The real news here is that if Celgene is forking over $25 million to Epizyme, EPZ-5676's data must be impressive. We should have a better idea of exactly how promising that data is sometime in the first half of 2014. With Epizyme's press release also noting its intention to run five clinical proof-of-concept trials in 2014, it's clear that this is going to be a company with a lot going on this year. I'm personally not chasing today's run-up higher because I'd much rather see that early-stage data in plain-as-day text than guess how good or bad it might be. Until we get more concrete data, the risks at these lofty levels could outweigh the rewards.