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 in Esperion Therapeutics (NASDAQ:ESPR) surged by more than 10% today after the FDA announced that it was removing a partial clinical hold that had been placed on Esperion's cholesterol lowering drug ETC-1002 in 2009.

So what: A partial clinical hold allows clinical studies to continue, but with specific restrictions issued by the FDA. For example, Esperion has been able to continue studying ETC-1002 in midstage clinical trials despite the FDA restricting the maximum dose of ETC-1002 to 240 mg and limiting trials to six months or less in duration.

Those midstage trial results have (so far) been solid. Patients taking ETC-1002 as a monotherapy saw their bad cholesterol levels fall by 27% and 30% at doses of 120 mg and 180 mg, respectively. Combining ETC-1002 with Merck's Zetia, a $4 billion per year drug, lowered bad cholesterol levels by 43%.

In addition to the dose and trial duration, the FDA also required Esperion to conduct two-year rat-and-mouse carcinogenic studies.

Those study results, which Esperion submitted to the FDA last year, were necessary before the company could launch studies longer than six months.

Since the FDA has now lifted its partial clinical hold, investor attention can now turn to Esperion's planned discussion with the FDA regarding its phase 2b results, which is expected to happen during Q3, and the launch of Esperion's large, long-term phase 3 trials by year-end.

Now what: The FDA's lifting of the partial hold is arguably critical to Esperion. ETC-1002 is the only therapy currently in clinical trials at Esperion, and without the FDA's action the company may not have been able to launch its phase 3 trials as planned.

Although the phase 3 trials are set to kick-off by the end of this year, the trial design is likely to include studying the drug through 2017, which suggests that an FDA review of ETC-1002 (assuming that phase 3 is a success) could be as far off as 2018 or 2019.

That suggests that interested investors should keep a close eye on Esperion's cash burn rate. Studying therapies for lowering cholesterol involves trials that include thousands of patients, and the costs of these trials can prove to be substantial. To address those costs, Esperion bolstered its balance sheet last fall with a secondary offering of 4,887,500 shares that raised an additional $91.6 million. As a result, Esperion has roughly $140 million in cash on the books. The company believes that should be enough to carry it through its phase 3 studies and into 2018, but investors would be wise to keep an eye on how quickly that balance drops. Regardless, Esperion remains a clinical stage company, and that means investing in it comes with its fair share of risk.