Staff reviewers of the U.S. Food and Drug Administration (FDA) have raised questions about the safety of AstraZeneca Plc's gout treatment. 

Reviewers pointed to higher death rates, cardiovascular issues and kidney-related side effects in patients who took the drug, lesinurad, a preliminary review published on Wednesday showed.

Industry analysts forecast annual sales of the drug to reach $350 million by 2020, according to consensus forecasts compiled by Thomson Reuters Cortellis.

Lesinurad, which is used in combination with an older gout drug febuxostat, decreases the production of uric acid and increases its excretion.

Gout, which affects nearly 8.3 million Americans, is a form of arthritis in which excess uric acid in the body forms crystals in joints and other tissues, leading to painful inflammation.

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Although the drug is not expected by analysts to be a major contributor to AstraZeneca's sales, its success in late-stage trials vindicates the company's ability to develop new medicines.

A panel of independent advisers to the FDA will make a recommendation on the drug on Friday. The agency typically follows the panel's recommendations.

Lesinurad was developed by Ardea Biosciences, which AstraZeneca bought for $1.26 billion in 2012.