The glowing green moth that advertises the sleeping pill Lunesta has become one of the best-known logos in the drug industry, gliding serenely across magazine pages, websites, and television screens. Now a tiny nutrition-supplement company is trying to clip its wings, saying that the Lunesta moth is an illegal knockoff of its own butterfly logo.

Tharos Laboratories Inc., which sells herbal sleep supplements, says Sepracor Inc. of Marlborough deliberately snatched its idea for advertising a sleep drug. For evidence, they point to Tharos’s butterfly, a winged blue outline that flutters across advertisements for its Nytex sleep supplement.

Tharos is asking a judge to block Sepracor from using its moth and to fork over any profits that it gained by using the logo. The money at stake could be considerable. Lunesta’s introduction last year was one of the top 10 new-drug launches in history, and sales are on track to reach nearly $600 million in 2006. Lunesta is also the single most heavily advertised drug of the past two years, according to TNS Media Intelligence, which estimates that Sepracor has spent more than $400 million on ads so far…The suit hints at the massive value a good logo can bring to a product…According to the suit, Tharos began using its butterfly logo in 2003, a year before Lunesta was approved. It applied to register the trademark in 2005. The suit points out that Lunesta’s website, like Tharos’s, has a “picture of a woman sleeping as its butterfly design mark crosses the webpage in a flying manner.”

Tharos says the green moth and its blue butterfly have already caused confusion among potential customers. The Tharos suit in U.S. District Court in Utah alleges trademark infringement, false advertising, and unfair competition.

—Stephen Heuser, The Boston Globe, 12/4/06