WASHINGTON (AP) — Amylin Pharmaceuticals won approval Friday for its long-delayed diabetes drug Bydureon, a next-generation treatment that requires fewer injections than the company’s 7-year old product, Byetta.

Bydureon is a once-a-week version of Byetta, which is taken twice a day to help diabetes patients control their blood sugar. Amylin executives say the new drug’s convenient regimen will give it a competitive advantage in the marketplace. However, after multiple delays it enters a market crowded with diabetes treatments, including one in the same class that has shown superior results.

The Food and Drug Administration approval comes after two previous rejections in 2010, when the agency asked Amylin to conduct a new study of the drug’s effects on the heart. News of the costly requirement sent company shares tumbling more than 50 percent and contributed to the breakup of Amylin’s long-standing partnership with Eli Lilly and Co. The companies ended their collaboration in November, with Amylin paying $250 million and agreeing to take over full responsibility for both Byetta and Bydureon.

Analysts generally expect Bydureon to generate $940 million in sales annually by 2016, though Deutsche Bank analyst Robyn Karnauskas says the drug must post $1.2 billion annually to turn a profit.

Karnauskas points out in a note to investors that Amylin currently has $2 billion in long-term debt and only $210 million in cash. She says Bydureon’s approval should give the San Diego company greater flexibility to refinance its debt.

Bydureon is part of the broader GLP-1 class of drugs, which work by increasing the body’s insulin production.

Amylin executives say the convenience of the drug’s weekly regimen should give it a competitive advantage in the marketplace. However, last year Amylin reported disappointing results for Bydureon against Novo Nordisk’s Victoza, a once-daily injection approved last January. On average, Bydureon reduced blood sugar levels in diabetics less than Victoza, which uses a different mechanism of action.

Bydureon was co-developed with Indianapolis-based Eli Lilly, which also helped co-market Byetta. Both drugs are scheduled to transfer to Amylin by the end of 2013. Alkermes, based in Waltham, Mass., created Bydureon’s formulation technology that gradually releases the drug over the course of a week.

Shares of Amylin Pharmaceuticals Inc. leaped $1.54, or 12.7 percent, to $13.68 in after-hours trading.