As a study of one prescription fish oil, GlaxoSmithKline’s now off-patent Lovaza, reported negative results, some experts continued to express optimism about Amarin’s ongoing Vascepa trial.

The evidence base around fish oil has always been mixed, and the negative results from the large Lovaza trial only added to that. In the study, called ASCEND, patients taking the prescription fish oil plus aspirin and patients taking a placebo showed no differences in cardiovascular events and death rates.

The trial, results of which were announced at last week’s European Society of Cardiology meeting, followed more than 15,000 people over seven years. But researchers concluded the differences between the two patient groups were not significant enough to prove efficacy. Other fish oil studies have reached similar results.

Despite the setback for this type of fish oil, some experts and analysts still believe Amarin’s seven-year study of its own prescription-grade fish oil, Vascepa, could be successful. The differences between the two studies, these experts argue, mean that one negative result does not forebode another.

Amarin’s trial, called REDUCE-IT, is expected to report results by the end of September. But the company was quick to point out differences between this unsuccessful trial and REDUCE-IT. The pharma company outlined these differences in a statement on Friday. 

Vascepa, to start, is a different formulation than Lovaza. Vascepa contains only one type of omega-3, EPA, while Lovaza contains two types, EPA and DHA, the latter of which tends to raise “bad” cholesterol and may offset some of its potential benefit, according to some experts. Vascepa also contains a higher dose of EPA omega-3 than Lovaza—four grams of EPA compared to 465 milligrams in Lovaza, nearly nine times more.

The trials also studied different patient populations. REDUCE-IT is studying adults with high risk of heart attack and stroke, while the Lovaza study only looked at patients with diabetes. Amarin believes that omega-3s are likely to be more successful in patients with a higher risk of cardiovascular events.

Jefferies analysts largely agreed. In an investor note, released Tuesday, they wrote that the ASCEND results have “little to no” bearing on REDUCE-IT. The analysts gave the Vascepa trial a 55% chance of success. 

Yet, other experts maintain that the Lovaza trial should be the last indicator needed to justify abandoning clinical use of fish oil for primary heart disease prevention, due to the evidence. 

Dr. Harlan Krumholz, editor-in-chief of the The New England Journal of Medicine’s Journal Watch Cardiology, wrote after the ASCEND results that, “People may quibble over the dose (higher doses do tend to lower triglyceride levels), but if we are to adhere to evidence, it is past time to move on from [omega-3] fatty acids for the primary prevention of vascular events.”

Dr. Sanjay Kaul, attending cardiologist at Cedars-Sinai Medical Center in Los Angeles, also remains “skeptical” about Vascepa, though he believes the trial could still be successful given its focus on a different drug and population. 

“REDUCE-IT enrolled patients at high risk for [cardiovascular disease] and is using a much higher dose of a different type of [omega-3],” Kaul wrote in an email. “Aspirin [dosed along with the omega-3 in the ASCEND trial] does not have much of a favorable impact in primary prevention, including patients with diabetes, but it does provide value in secondary prevention. So, it is possible for Vascepa to provide benefit in this high-risk cohort provided there is sufficient lowering of triglycerides. However, I remain skeptical!”

Despite the negative Lovaza results, Amarin believes their study is “the ‘right’ drug, at the ‘right’ dose in the ‘right’ patient population,” the company said in its statement. 

A Jefferies analyst note from earlier this month showed how much Amarin stands to gain from a successful Vascepa study. If the REDUCE-IT study is positive, Vascepa could reach up to $2 billion in sales at its peak.