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 Amarin Corporation (NASDAQ:AMRN) rose more than 11% Wednesday after SunTrust Bank upgraded the stock to buy from neutral and set a price target of $6. The move appears to be based on optimism that Amarin's Vascepa can continue to grow sales and that the company can eventually win label expansion.

So what:  In 2012, the FDA approved use of Vascepa as a triglyceride-lowering medicine for patients with severe hypertriglyceridemia after clinical studies showed triglyceride levels fell 33% from baseline in patients using the drug.

However, that small patient population has not translated into significant revenue (Vascepa sales totaled just $14.1 million in the third quarter). As a result, investors have hoped the FDA would OK a label expansion for Vascepa that would increase its total addressable patient pool.

In October 2013, those hopes were dashed when a key FDA advisory panel decided against supporting label expansion, opting instead to wait for more confirmatory data.

Since Amarin is spending tens of millions of dollars on clinical studies, and data from a late-stage trial that could prove Vascepa improves cardiac outcomes won't be available until 2018, the FDA's decision has prompted questions over whether Amarin can remain solvent long enough for the drug to win approval in that larger patient population.

Now what:  SunTrust's upgrade offers investors some optimism that Amarin can remain viable; however, many questions remain for the company. Although cost-cutting reduced outflow from operations to $58.7 million through the first nine months of 2014, from $157.2 million in the comparable period of 2013, expenses continue to outstrip revenue. As a result, Amarin's cash on hand totaled $135.4 million at the end of the third quarter, which was $56 million less than it had on the books heading into 2014. Overall, the ongoing uncertainty regarding any potential label expansion and a high cash burn rate make this one too speculative for me.