Novo Nordisk A/S's closely watched diabetes drug semaglutide is effective, a preliminary review by the U.S. Food and Drug Administration concluded, sending the company's shares up 3.4 percent in premarket trading on Monday.

The review, posted on the FDA's website on Monday, comes two days ahead of a meeting of advisors to the agency who will discuss the drug, semaglutide, and recommend whether it should be approved.

The FDA typically follows the recommendations of its advisors.

"The review for efficacy supports the claim of using semaglutide for improving glycemic control in adults with type 2 diabetes," the review said. The reviewers found no additional cardiovascular risk associated with the drug.

There was an increase in the number of people who developed sight problems, the review said, but concluded there was "no reason to restrict semaglutide with respect to population or dosing schedule."