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 focused on developing anticancer therapies, tanked as much as 43% after reporting early-stage results for leukemia drug EPZ-5676.

So what: According to the company's press release, EPZ-5676 -- which blocks a select protein known as DOT1L, which is responsible for the development of acute leukemia with MLL-rearrangement -- demonstrated a "therapeutic mechanism of action" in four of eight MLL-r patients and no response in non-MLL-r patients. Epizyme also notes that it did not achieve a maximum tolerated dose in its studies although EPZ-5676 appeared to be safe and well-tolerated.

Now what: It seems like a fairly benign and innocuous early stage press release, but investors seem keen on focusing on the early efficacy of the EPZ-5676. Even though it delivered what looks like a 50% response rate, analysts and investors are concerned that its effectiveness is being glossed over early on in this study. In Epizyme's defense, the company is still dose-escalating EPZ-5676 to discover the right dosing period and didn't reach a maximum-tolerated dose which means there could be room for improved clinical benefit. I generally dislike placing too much credence in very early-stage results like this, but if my arm were twisted I would say that emotions probably got the better of investors today with Epizyme.