Groton - Amarin Corp. plc announced Thursday that its heart medication Vascepa could soon be marketed in China under a new commercialization agreement that sent shares of its stock soaring on the Nasdaq exchange.

Shares were up more than 10 percent in the midafternoon Thursday after an initial surge that had sent the stock to its highest level in months.

"If China's potential can be realized, it could mark an important victory for Amarin," said the investment site TheMotleyFool in an online posting.

Amarin said it had reached an agreement with China-based Eddingpharm to develop and commercialize Vascepa on the mainland as well as in Hong Kong, Taiwan and Macao. Amarin will get $15 million up front and milestone payments of up to $154 million as well as royalties on net sales.

"Our agreement with Eddingpharm reflects the culmination of a competitive process and represents a significant step toward commercializing Vascepa in a major market outside the United States," said John F. Thero, Amarin's chief executive, in a statement.

According to Amarin, China is the third leading pharmaceutical market in the world and has been growing over the past decade at an annual rate of about 20 percent. At its current rate of growth, China will surpass Japan as the second largest drug market within the next five years, the company said.

Amarin said its prescription-grade fish oil could be the first such omega-3 product introduced in China, potentially helping millions of patients with high levels of fat in their blood - a risk indicator for heart disease.

"Eddingpharm has established development and regulatory capabilities and an impressive commercial organization that has launched many innovative products in China," Thero said. "Eddingpharm's successful track record of long-term alliances with leading global pharmaceutical companies gives us confidence in Vascepa's success in China."

Amarin, an Irish company that has its research-and-development headquarters on Bridge Street, has seen its stock price tank since the U.S. Food and Drug Administration rescinded a special agreement that had appeared to clear the way for Vascepa to be approved for use in millions of people with moderately elevated levels of triglycerides in their blood. It currently has approval to market the drug only to U.S. patients with very high triglyceride levels.

Vascepa sales, which once had been projected at $1 billion annually, have been disappointing, totaling only $14.1 million in the third quarter of last year. Facing low sales numbers and increased costs to demonstrate Vascepa's effectiveness, Amarin two years ago laid off half its worldwide staff.

l.howard@theday.com

Twitter: @KingstonLeeHow