March 28 (Reuters) - The U.S. Food and Drug

Administration has declined to approve Milestone

Pharmaceuticals' ( MIST ) nasal spray to treat a type of heart

condition, the company said on Friday.

The health regulator did not raise any concerns related to

the safety or efficacy of the spray, called Cardamyst, but

highlighted two key chemistry, manufacturing and controls

issues.

Shares of the company were halted in premarket trading.