PRINCETON, NJ ( TheStreet) -- Omthera Pharmaceuticals released late-stage study results on its omega-3 (fish oil) drug Thursday, which while positive, don't appear to compare well to Amarin's ( AMRN) competing product. Amarin shares are up $1.43, or 14%, to $11.40 Thursday on reaction to the Omthera news. Omthera said that a low and high dose of Epanova lowered triglyceride (TG) levels by 26% and 31% respectively in patients who entered the clinical trial with very high levels of the blood-based fat. Non-HDL-C levels were also reduced by 8% in both Epanova doses, according to Omthera. Epanova treatment was compared against an olive oil control in the phase III study but investors were more interested in comparing the drug to previously announced results from a similar trial of Amarin's AMR101. Here, AMR101 looks better. Low and high doses of AMR101 reduced TG levels by 20% and 33% respectively in the same type of patients with very high TG levels at baseline. AMR101, however, produced greater reductions on non-HDL-C levels of 8% and 18% for the low and high dose, respectively. Perhaps most telling, Omthera did not disclose data on Epanova's ability to lower or maintain LDL (bad cholesterol) levels in the phase III trial. By comparison, Amarin's AMR101, in its own study, showed a 2.3% reduction in LDL-C at the high dose. Omthera's Epanova, at a lower dose, appears to work just as well as GlaxoSmithKline's ( GSK) Lovaza, the only prescription-grade omega-3 product currently on the market. But Amarin's AMR101's lipid-lowering profile, and particularly its ability to stabilize or even lower LDL levels, may be best in class. Amarin submitted AMR101 for approval and U.S. regulators are expected to make a decision by July 26. Amarin shares have been volatile for much of the past year on concerns about AMR101 patent protection as well as uncertainty about how the drug, if approved, will be marketed. Investor expectations that Amarin would be sold to a large pharmaceutical company have yet to be met. In the past week, SAC Capital bought an additional 3.7 million shares of Amarin, increasing its total position to 7.2 million share, regulatory filings show. The hedge fund controlled by Steve Cohen now owns 5.3% of Amarin. On the other side, Abingworth and Soffinova Ventures, early venture capital backers of Amarin, sold 2.3 million shares and 3 million shares of the company, respectively. Both firms retain significant Amarin positions. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: firstname.lastname@example.org. Follow TheStreet on Twitter and become a fan on Facebook.