Amarin's (NASDAQ:AMRN) share price was riding high this summer as its key drug Vascepa neared approval from the Food and Drug Administration. While this stock is still up more than 50% year to date post-approval, the company is facing new challenges, and its share price has floundered recently.

To help you weigh both the opportunities and risks associated with this stock, we're launching a brand new premium report on Amarin. The following is only a sample of what you'll find in the complete report.

What does Vascepa treat?
Fat is something that we generally think is bad, but triglycerides are a specific type of fat that every healthy body needs to function at a cellular level. Nevertheless, having a lot of this fat in your bloodstream may take a serious toll on your health. According to the World Heart Federation, extremely high triglyceride levels -- a condition called hypertriglyceridemia -- can lead to heart attacks and strokes.

Amarin's Vascepa, which is derived from an omega-3 fatty acid, lowers triglyceride levels and specifically treats patients with the most severe cases. To put this into context, a healthy person has less than 150 milligrams of triglycerides for every deciliter of blood, while patients with severe hypertriglyceridemia can have a concentration of between 500-2,000 mg/dL. In rare -- and extremely dangerous cases -- these levels can exceed 2,000 mg/dL.

Fighting fat with fat
Omega-3 fatty acids, which are present in fish oil, can combat this disorder. You can readily find over-the-counter omega-3 supplements at your local pharmacy, but they probably won't be effective against severely elevated triglyceride levels. However, it's been commonly thought for years that omega-3 supplements promote a healthy heart, but recent data suggests otherwise. Two separate academic research groups sent the media into a frenzy when their research indicated that fish oil pills don't seem to have any discernible long-term benefits.

Is it possible that these supplements don't actually help your heart? Yes. Should Amarin shareholders care? Not really.

As this debate continues to divide medical opinion, investors can rest assured that Vascepa's efficacy is not being questioned. This is a prescription drug derived from an exceedingly pure omega-3 fatty acid, and a clinical study demonstrated that triglyceride levels were lowered by a whopping 33% after patients took the drug for only 12 weeks. Not only is this drug very potent, but it also has a great safety profile and is associated with virtually no harmful side effects.

Market
Fortunately, Amarin is entering a market with few U.S. competitors. Abbott Laboratories' (NYSE:ABT) medicines Tricor and Trilipix are players in this space, and brought in almost $1.4 billion in the U.S. alone in fiscal 2011. Despite this impressive figure, Amarin reports that these drugs interfere with important biochemical pathways and can elevate liver enzyme levels. GlaxoSmithKline's (NYSE:GSK) drug Lovaza, on the other hand, is partially made up of omega-3 fatty acid like Vascepa. In fiscal 2011, its U.S. sales topped $900 million.

The differentiating factor here is that Lovaza contains an additional chemical called DHA, and Vascepa does not. While DHA can contribute to lowering triglyceride levels, it might actually increase cholesterol. When Amarin's sales team starts pounding the pavement, you can be sure they'll use Vascepa's purity and exclusion of DHA as an edge against the competition.

Analysts believe that Vascepa's combined efficacy and safety could translate into more than $1 billion in sales. However, this is Amarin's maiden voyage into the hypertriglyceridemia market, and it remains to be seen if the company can execute a successful drug launch.

Future opportunities
In terms of potential customers, it's estimated that around 4 million Americans suffer from the most serious form of hypertriglyceridemia. GSK's Lovaza is also approved for the same indication -- and just as a reminder, this means that both drugs are only approved to treat patients with triglyceride levels of 500 mg/dL or higher.

It may seem like Amarin is entering a finite market and will have to compete directly with GSK for a limited number of patients, but Amarin could be able to sell the drug to a broader market in the coming years. The company has successfully completed a separate clinical trial with Vascepa -- referred to as the ANCHOR study -- to treat patients with triglyceride levels in the 200-500 mg/dL range who are also taking additional medication to lower their cholesterol. Roughly 40 million Americans have triglycerides at these levels, so this would make Vascepa available to a massive patient population.

Much like Al Pacino's character in the film Scent of a Woman, an FDA-approved expansion of Vascepa's use could mean that Amarin is "just gettin' warmed up."

Max Macaluso, Ph.D. has no positions in the stocks mentioned above. The Motley Fool owns shares of Abbott Laboratories. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.