A U.S. District Court on Friday made a preliminary ruling in favor of Amarin Corp. in its lawsuit against the U.S. Food and Drug Administration, saying the Irish drug maker has the right to promote information about off-label uses for its prescription fish-oil pill.

The court ruled that the company has the right, under the First Amendment, to promote information to health-care professionals about certain uses of Vascepa that aren't covered by the drug's FDA-approved labeling—as long as the information is true and not misleading.

A FDA representative declined to comment, saying the agency "does not comment on possible, pending or ongoing litigation." An appeal of the ruling can be filed within 60 days, Amarin said in a news release.

Amarin had filed its suit in May in a move that was expected to have broad ramifications for the way the pharmaceutical industry markets medicines and interacts with physicians.

Shares of Amarin surged 15% to $2.35 following the ruling.

Amarin wanted to provide doctors with clinical trial data that didn't directly pertain to the approved uses of its Vascepa prescription fish-oil pill. The FDA had endorsed the drug to treat people with very high levels of triglycerides, a type of fat in the blood that can lead to heart disease.

But Amarin wanted to market the pill to people with slightly lower levels of triglycerides who were already taking statins, a cholesterol drug. Amarin also wanted to reference data from an FDA-approved study that showed Vascepa's potential to reduce the risk of cardiovascular disease, according to the suit. The FDA rejected Amarin's bid.

Amarin said it can now use efficacy data from the clinical trial and other relevant study results. The company said it plans to begin promotional activities as soon as possible.

The question over where drug makers should be allowed to distribute information about unapproved uses of their medicines has been widely debated after a federal appeals court overturned the criminal conviction of a sales rep for promoting so-called off-label uses of a drug three years ago. The court ruled his actions constituted protected speech because the information was truthful and not misleading.

Since then, the pharmaceutical industry has been lobbying the FDA to revise its guidelines, because the decision only applied to three states.